From bf9eab8aa038619548d9ac90d6156e3b8f90fff4 Mon Sep 17 00:00:00 2001
From: Jan Svoboda <jan@svoboda.ai>
Date: Tue, 21 Oct 2025 15:48:10 -0700
Subject: [PATCH] Revert "[clang] Cherry-pick FS sandboxing (pt. 1)"

---
 .../lib/Tooling/ApplyReplacements.cpp         |   2 +-
 .../clang-include-fixer/IncludeFixer.cpp      |   5 +-
 clang-tools-extra/clang-move/Move.cpp         |   2 +-
 clang-tools-extra/clangd/Compiler.cpp         |  10 +-
 clang-tools-extra/clangd/ConfigCompile.cpp    |   2 +-
 .../clangd/SystemIncludeExtractor.cpp         |   2 +-
 .../clangd/index/SymbolCollector.cpp          |   2 +-
 clang-tools-extra/clangd/tool/ClangdMain.cpp  |   6 +-
 .../include-cleaner/tool/IncludeCleaner.cpp   |   2 +-
 .../include-cleaner/unittests/RecordTest.cpp  |  10 +-
 .../clang/Basic/DiagnosticDriverKinds.td      |   6 +-
 .../clang/Basic/DiagnosticFrontendKinds.td    |   3 -
 clang/include/clang/CodeGen/BackendUtil.h     |   2 +-
 clang/include/clang/Driver/Options.td         |  11 +-
 clang/include/clang/Frontend/ASTUnit.h        |   7 +-
 .../include/clang/Frontend/CompilerInstance.h |  51 ++---
 .../clang/Frontend/CompilerInvocation.h       |   3 +-
 clang/include/clang/Frontend/Utils.h          |   5 +-
 clang/include/clang/Lex/HeaderSearch.h        |   3 -
 .../include/clang/Serialization/ModuleCache.h |   9 +-
 clang/lib/CodeGen/BackendUtil.cpp             |  57 +++--
 clang/lib/CodeGen/CGOpenMPRuntime.cpp         |  10 +-
 clang/lib/CodeGen/CodeGenAction.cpp           |   3 +-
 clang/lib/CodeGen/CodeGenModule.cpp           |  35 +---
 clang/lib/CrossTU/CrossTranslationUnit.cpp    |  16 +-
 clang/lib/Driver/ToolChains/Clang.cpp         |  43 +---
 clang/lib/ExtractAPI/ExtractAPIConsumer.cpp   |   3 +-
 clang/lib/Frontend/ASTMerge.cpp               |   3 +-
 clang/lib/Frontend/ASTUnit.cpp                |  15 +-
 clang/lib/Frontend/ChainedIncludesSource.cpp  |   3 +-
 clang/lib/Frontend/CompileJobCache.cpp        |   6 +-
 clang/lib/Frontend/CompilerInstance.cpp       | 198 ++++++++++++------
 clang/lib/Frontend/CompilerInvocation.cpp     |  96 +++++++--
 clang/lib/Frontend/FrontendAction.cpp         |  26 ++-
 .../Frontend/ModuleDependencyCollector.cpp    |  11 +-
 clang/lib/Frontend/PrecompiledPreamble.cpp    |   5 +-
 .../lib/Frontend/Rewrite/FrontendActions.cpp  |   2 +-
 .../ExecuteCompilerInvocation.cpp             |  13 +-
 clang/lib/Interpreter/Interpreter.cpp         |   7 +-
 clang/lib/Lex/HeaderSearch.cpp                |  14 +-
 clang/lib/Serialization/ASTWriter.cpp         |   7 +-
 clang/lib/Serialization/ModuleCache.cpp       |  86 --------
 clang/lib/StaticAnalyzer/Checkers/Yaml.h      |   8 +-
 .../StaticAnalyzer/Frontend/ModelInjector.cpp |  15 +-
 clang/lib/Testing/TestAST.cpp                 |  12 +-
 .../DependencyScanningWorker.cpp              | 108 ++++++----
 .../InProcessModuleCache.cpp                  |   7 -
 .../IncludeTreeActionController.cpp           |   3 +-
 clang/lib/Tooling/Tooling.cpp                 |   5 +-
 .../Inputs/taint-generic-config-vfs.json      |  17 --
 clang/test/Analysis/model-file-missing.cpp    |   3 -
 clang/test/Analysis/taint-generic.c           |   6 +-
 clang/test/CAS/output-path-error.c            |   2 +-
 clang/test/CAS/pgo-profile-with-pch.c         |   6 +-
 clang/test/CAS/pgo-profile.c                  |  16 +-
 clang/test/CodeGen/cspgo-instrumentation.c    |   6 +-
 .../test/CodeGen/cspgo-instrumentation_lto.c  |   6 +-
 .../CodeGen/cspgo-instrumentation_thinlto.c   |   8 +-
 clang/test/CodeGen/opt-record.c               |   2 +-
 clang/test/CodeGen/pgo-instrumentation.c      |   4 +-
 .../thinlto-clang-diagnostic-handler-in-be.c  |   2 +-
 .../CodeGenCXX/fdebug-info-for-profiling.cpp  |   2 +-
 clang/test/CodeGenCXX/profile-remap.cpp       |   4 +-
 clang/test/Driver/Inputs/a.proftext           |   2 -
 clang/test/Driver/cl-options.c                |  17 +-
 clang/test/Driver/clang_f_opts.c              |  18 +-
 clang/test/Driver/fcs-profile-generate.c      |  12 +-
 clang/test/Driver/fsplit-machine-functions.c  |  12 +-
 .../optimization-remark-with-hotness-new-pm.c |  11 +-
 ...dules-cache-path-canonicalization-output.c |  18 --
 clang/test/OpenMP/amdgcn_save_temps.c         |  23 --
 clang/test/OpenMP/host-ir-file-vfs.c          |  33 ---
 clang/test/Profile/c-captured.c               |   2 +-
 clang/test/Profile/c-counter-overflows.c      |   2 +-
 clang/test/Profile/c-general.c                |   8 +-
 clang/test/Profile/c-outdated-data.c          |   4 +-
 clang/test/Profile/c-unprofiled-blocks.c      |   2 +-
 clang/test/Profile/c-unprofiled.c             |   2 +-
 clang/test/Profile/cxx-class.cpp              |   2 +-
 clang/test/Profile/cxx-hash-v2.cpp            |   4 +-
 clang/test/Profile/cxx-lambda.cpp             |   2 +-
 clang/test/Profile/cxx-missing-bodies.cpp     |   2 +-
 .../Profile/cxx-never-executed-branch.cpp     |   2 +-
 clang/test/Profile/cxx-rangefor.cpp           |   2 +-
 clang/test/Profile/cxx-templates.cpp          |   2 +-
 clang/test/Profile/cxx-throws.cpp             |   4 +-
 clang/test/Profile/func-entry.c               |   2 +-
 clang/test/Profile/misexpect-branch-cold.c    |   2 +-
 .../misexpect-branch-nonconst-expected-val.c  |   2 +-
 .../Profile/misexpect-branch-unpredictable.c  |   2 +-
 clang/test/Profile/misexpect-branch.c         |   8 +-
 clang/test/Profile/misexpect-switch-default.c |   2 +-
 .../test/Profile/misexpect-switch-nonconst.c  |   2 +-
 .../misexpect-switch-only-default-case.c      |   2 +-
 clang/test/Profile/misexpect-switch.c         |   2 +-
 clang/test/Profile/objc-general.m             |   2 +-
 .../test/Profile/profile-does-not-exist-ir.c  |  10 +-
 clang/test/Profile/profile-does-not-exist.c   |   6 +-
 clang/test/Profile/profile-summary.c          |   2 +-
 clang/test/VFS/broken-vfs-module-dep.c        |   1 +
 clang/tools/c-index-test/core_main.cpp        |   7 +-
 .../ClangExtDefMapGen.cpp                     |   4 +-
 .../clang-import-test/clang-import-test.cpp   |   6 +-
 .../clang-installapi/ClangInstallAPI.cpp      |   2 +-
 clang/tools/driver/cc1_main.cpp               |   8 +-
 clang/tools/driver/cc1as_main.cpp             |  16 +-
 clang/tools/driver/driver.cpp                 |  21 +-
 clang/tools/libclang/CDependencies.cpp        |   5 +-
 clang/tools/libclang/CIndex.cpp               |   7 +-
 clang/unittests/AST/ExternalASTSourceTest.cpp |   3 +-
 clang/unittests/CodeGen/TestCompiler.h        |   5 +-
 clang/unittests/Driver/ToolChainTest.cpp      |   3 +-
 clang/unittests/Frontend/ASTUnitTest.cpp      |   3 +-
 .../unittests/Frontend/CodeGenActionTest.cpp  |   6 +-
 .../Frontend/CompilerInstanceTest.cpp         |   6 +-
 .../unittests/Frontend/FrontendActionTest.cpp |  19 +-
 clang/unittests/Frontend/OutputStreamTest.cpp |   9 +-
 .../Serialization/ForceCheckFileInputTest.cpp |  11 +-
 .../Serialization/ModuleCacheTest.cpp         |   4 -
 .../Serialization/NoCommentsTest.cpp          |   1 -
 .../PreambleInNamedModulesTest.cpp            |   8 +-
 clang/unittests/Support/TimeProfilerTest.cpp  |   7 +-
 .../DependencyScannerTest.cpp                 |   5 +-
 flang/lib/Frontend/CompilerInvocation.cpp     |   3 +-
 flang/lib/Frontend/FrontendActions.cpp        |   6 +-
 lldb/source/Commands/CommandObjectTarget.cpp  |   4 +-
 .../Clang/ClangExpressionParser.cpp           |   8 +-
 .../Clang/ClangModulesDeclVendor.cpp          |   3 +-
 .../Clang/ModuleDependencyCollector.h         |   4 +-
 llvm/include/llvm/CodeGen/AsmPrinter.h        |   8 -
 .../llvm/Frontend/OpenMP/OMPIRBuilder.h       |   9 +-
 llvm/include/llvm/Passes/PassBuilder.h        |  19 +-
 llvm/include/llvm/Support/CommandLine.h       |   4 +-
 llvm/include/llvm/Support/FileCollector.h     |  11 +-
 llvm/include/llvm/Support/FileSystem.h        |  12 ++
 llvm/include/llvm/Support/PGOOptions.h        |  11 +-
 llvm/include/llvm/Support/Path.h              |  12 --
 llvm/include/llvm/Support/SourceMgr.h         |  11 +-
 llvm/include/llvm/Support/VirtualFileSystem.h |  10 +-
 .../Instrumentation/DataFlowSanitizer.h       |   7 +-
 .../Transforms/Instrumentation/GCOVProfiler.h |   7 +-
 llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp    |   2 -
 .../AsmPrinter/AsmPrinterInlineAsm.cpp        |   2 -
 llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp     |  20 +-
 llvm/lib/LTO/LTOBackend.cpp                   |  17 +-
 llvm/lib/Passes/PassBuilder.cpp               |   5 +-
 llvm/lib/Passes/PassBuilderPipelines.cpp      |  43 ++--
 llvm/lib/Support/CommandLine.cpp              |  24 +--
 llvm/lib/Support/FileCollector.cpp            |  16 +-
 llvm/lib/Support/PGOOptions.cpp               |   9 +-
 llvm/lib/Support/Path.cpp                     | 100 ++++-----
 llvm/lib/Support/SourceMgr.cpp                |  18 +-
 llvm/lib/Support/VirtualFileSystem.cpp        |  31 +--
 llvm/lib/TableGen/Main.cpp                    |   2 -
 llvm/lib/TableGen/Parser.cpp                  |   2 -
 llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp  |   2 -
 llvm/lib/Target/X86/X86InstrInfo.cpp          |   1 -
 .../Instrumentation/DataFlowSanitizer.cpp     |  12 +-
 .../Instrumentation/GCOVProfiling.cpp         |  30 ++-
 llvm/tools/dsymutil/Reproducer.cpp            |   5 +-
 llvm/tools/llvm-config/llvm-config.cpp        |   6 +-
 llvm/tools/llvm-dwp/llvm-dwp.cpp              |   2 +-
 .../llvm-mc-assemble-fuzzer.cpp               |   2 -
 llvm/tools/llvm-mc/llvm-mc.cpp                |   2 -
 llvm/tools/llvm-ml/llvm-ml.cpp                |   2 -
 llvm/tools/llvm-opt-report/OptReport.cpp      |   2 +-
 llvm/tools/obj2yaml/obj2yaml.cpp              |   2 +-
 llvm/tools/opt/NewPMDriver.cpp                |  14 +-
 llvm/tools/yaml2obj/yaml2obj.cpp              |   2 +-
 llvm/unittests/Support/CommandLineTest.cpp    |  12 +-
 llvm/unittests/Support/FileCollectorTest.cpp  |  21 +-
 llvm/unittests/Support/Path.cpp               |   4 +-
 llvm/unittests/Support/SourceMgrTest.cpp      |  10 -
 .../Support/VirtualFileSystemTest.cpp         |  55 +----
 llvm/utils/FileCheck/FileCheck.cpp            |   2 +-
 llvm/utils/split-file/split-file.cpp          |   1 -
 mlir/lib/IR/Diagnostics.cpp                   |   6 +-
 .../OpenMP/OpenMPToLLVMIRTranslation.cpp      |  21 +-
 mlir/lib/Tools/PDLL/Parser/Parser.cpp         |   2 -
 .../Tools/mlir-pdll-lsp-server/PDLLServer.cpp |   2 -
 .../tblgen-lsp-server/TableGenServer.cpp      |   2 -
 mlir/tools/mlir-pdll/mlir-pdll.cpp            |   2 -
 182 files changed, 865 insertions(+), 1240 deletions(-)
 delete mode 100644 clang/test/Analysis/Inputs/taint-generic-config-vfs.json
 delete mode 100644 clang/test/Analysis/model-file-missing.cpp
 delete mode 100644 clang/test/Driver/Inputs/a.proftext
 delete mode 100644 clang/test/Modules/modules-cache-path-canonicalization-output.c
 delete mode 100644 clang/test/OpenMP/amdgcn_save_temps.c
 delete mode 100644 clang/test/OpenMP/host-ir-file-vfs.c

diff --git a/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp b/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
index 0ac8f712e112f..b895075e4f31c 100644
--- a/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
+++ b/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
@@ -142,7 +142,7 @@ groupReplacements(const TUReplacements &TUs, const TUDiagnostics &TUDs,
     // build directories, make them absolute immediately.
     SmallString<128> Path = R.getFilePath();
     if (BuildDir)
-      llvm::sys::path::make_absolute(*BuildDir, Path);
+      llvm::sys::fs::make_absolute(*BuildDir, Path);
     else
       SM.getFileManager().makeAbsolutePath(Path);
 
diff --git a/clang-tools-extra/clang-include-fixer/IncludeFixer.cpp b/clang-tools-extra/clang-include-fixer/IncludeFixer.cpp
index fa3ec4a975d65..7b0e4ecda8214 100644
--- a/clang-tools-extra/clang-include-fixer/IncludeFixer.cpp
+++ b/clang-tools-extra/clang-include-fixer/IncludeFixer.cpp
@@ -94,9 +94,10 @@ bool IncludeFixerActionFactory::runInvocation(
 
   // Create the compiler's actual diagnostics engine. We want to drop all
   // diagnostics here.
-  Compiler.createDiagnostics(new clang::IgnoringDiagConsumer,
+  Compiler.createDiagnostics(Files->getVirtualFileSystem(),
+                             new clang::IgnoringDiagConsumer,
                              /*ShouldOwnClient=*/true);
-  Compiler.createSourceManager();
+  Compiler.createSourceManager(*Files);
 
   // We abort on fatal errors so don't let a large number of errors become
   // fatal. A missing #include can cause thousands of errors.
diff --git a/clang-tools-extra/clang-move/Move.cpp b/clang-tools-extra/clang-move/Move.cpp
index 519d359991cdb..17f597170f9f6 100644
--- a/clang-tools-extra/clang-move/Move.cpp
+++ b/clang-tools-extra/clang-move/Move.cpp
@@ -75,7 +75,7 @@ std::string MakeAbsolutePath(StringRef CurrentDir, StringRef Path) {
     return "";
   llvm::SmallString<128> InitialDirectory(CurrentDir);
   llvm::SmallString<128> AbsolutePath(Path);
-  llvm::sys::path::make_absolute(InitialDirectory, AbsolutePath);
+  llvm::sys::fs::make_absolute(InitialDirectory, AbsolutePath);
   return CleanPath(std::move(AbsolutePath));
 }
 
diff --git a/clang-tools-extra/clangd/Compiler.cpp b/clang-tools-extra/clangd/Compiler.cpp
index 6ebc2eac25745..8b3865c8a8e5c 100644
--- a/clang-tools-extra/clangd/Compiler.cpp
+++ b/clang-tools-extra/clangd/Compiler.cpp
@@ -147,9 +147,13 @@ prepareCompilerInstance(std::unique_ptr<clang::CompilerInvocation> CI,
   }
 
   auto Clang = std::make_unique<CompilerInstance>(std::move(CI));
-  Clang->createVirtualFileSystem(VFS, &DiagsClient);
-  Clang->createDiagnostics(&DiagsClient, false);
-  Clang->createFileManager();
+  Clang->createDiagnostics(*VFS, &DiagsClient, false);
+
+  if (auto VFSWithRemapping = createVFSFromCompilerInvocation(
+          Clang->getInvocation(), Clang->getDiagnostics(), VFS))
+    VFS = VFSWithRemapping;
+  Clang->createFileManager(VFS);
+
   if (!Clang->createTarget())
     return nullptr;
 
diff --git a/clang-tools-extra/clangd/ConfigCompile.cpp b/clang-tools-extra/clangd/ConfigCompile.cpp
index 6a5206df9a261..35d35f747a868 100644
--- a/clang-tools-extra/clangd/ConfigCompile.cpp
+++ b/clang-tools-extra/clangd/ConfigCompile.cpp
@@ -131,7 +131,7 @@ struct FragmentCompiler {
       return std::nullopt;
     }
     llvm::SmallString<256> AbsPath = llvm::StringRef(*Path);
-    llvm::sys::path::make_absolute(FragmentDirectory, AbsPath);
+    llvm::sys::fs::make_absolute(FragmentDirectory, AbsPath);
     llvm::sys::path::native(AbsPath, Style);
     return AbsPath.str().str();
   }
diff --git a/clang-tools-extra/clangd/SystemIncludeExtractor.cpp b/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
index b4f0c4f765c2f..0b067e8b0b2b2 100644
--- a/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
+++ b/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
@@ -106,7 +106,7 @@ struct DriverArgs {
     // relative or absolute).
     if (llvm::any_of(Driver,
                      [](char C) { return llvm::sys::path::is_separator(C); })) {
-      llvm::sys::path::make_absolute(Cmd.Directory, Driver);
+      llvm::sys::fs::make_absolute(Cmd.Directory, Driver);
     }
     this->Driver = Driver.str().str();
     for (size_t I = 0, E = Cmd.CommandLine.size(); I < E; ++I) {
diff --git a/clang-tools-extra/clangd/index/SymbolCollector.cpp b/clang-tools-extra/clangd/index/SymbolCollector.cpp
index 39c479b5f4d5b..6bdb1080fb294 100644
--- a/clang-tools-extra/clangd/index/SymbolCollector.cpp
+++ b/clang-tools-extra/clangd/index/SymbolCollector.cpp
@@ -325,7 +325,7 @@ class SymbolCollector::HeaderFileURICache {
     if (R.second) {
       llvm::SmallString<256> AbsPath = Path;
       if (!llvm::sys::path::is_absolute(AbsPath) && !FallbackDir.empty())
-        llvm::sys::path::make_absolute(FallbackDir, AbsPath);
+        llvm::sys::fs::make_absolute(FallbackDir, AbsPath);
       assert(llvm::sys::path::is_absolute(AbsPath) &&
              "If the VFS can't make paths absolute, a FallbackDir must be "
              "provided");
diff --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
index 91b2422d412c8..f287439f10cab 100644
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -577,7 +577,7 @@ class TestScheme : public URIScheme {
     Body = Body.ltrim('/');
     llvm::SmallString<16> Path(Body);
     path::native(Path);
-    path::make_absolute(TestScheme::TestDir, Path);
+    fs::make_absolute(TestScheme::TestDir, Path);
     return std::string(Path);
   }
 
@@ -775,8 +775,8 @@ It should be used via an editor plugin rather than invoked directly. For more in
 clangd accepts flags on the commandline, and in the CLANGD_FLAGS environment variable.
 )";
   llvm::cl::HideUnrelatedOptions(ClangdCategories);
-  llvm::cl::ParseCommandLineOptions(argc, argv, Overview, /*Errs=*/nullptr,
-                                    /*VFS=*/nullptr, FlagsEnvVar);
+  llvm::cl::ParseCommandLineOptions(argc, argv, Overview,
+                                    /*Errs=*/nullptr, FlagsEnvVar);
   if (Test) {
     if (!Sync.getNumOccurrences())
       Sync = true;
diff --git a/clang-tools-extra/include-cleaner/tool/IncludeCleaner.cpp b/clang-tools-extra/include-cleaner/tool/IncludeCleaner.cpp
index fefbfc3a9614d..372ab5fa2706e 100644
--- a/clang-tools-extra/include-cleaner/tool/IncludeCleaner.cpp
+++ b/clang-tools-extra/include-cleaner/tool/IncludeCleaner.cpp
@@ -344,7 +344,7 @@ mapInputsToAbsPaths(clang::tooling::CompilationDatabase &CDB,
     }
     for (const auto &Cmd : Cmds) {
       llvm::SmallString<256> CDBPath(Cmd.Filename);
-      llvm::sys::path::make_absolute(Cmd.Directory, CDBPath);
+      llvm::sys::fs::make_absolute(Cmd.Directory, CDBPath);
       CDBToAbsPaths[std::string(CDBPath)] = std::string(AbsPath);
     }
   }
diff --git a/clang-tools-extra/include-cleaner/unittests/RecordTest.cpp b/clang-tools-extra/include-cleaner/unittests/RecordTest.cpp
index fc8b23ffcb17c..91d2697712b6e 100644
--- a/clang-tools-extra/include-cleaner/unittests/RecordTest.cpp
+++ b/clang-tools-extra/include-cleaner/unittests/RecordTest.cpp
@@ -625,15 +625,13 @@ TEST_F(PragmaIncludeTest, ExportInUnnamedBuffer) {
                                                  *Diags, "clang"));
 
   auto Clang = std::make_unique<CompilerInstance>(std::move(Invocation));
-  Clang->createVirtualFileSystem(VFS);
-  Clang->createDiagnostics();
+  Clang->createDiagnostics(*VFS);
 
-  Clang->createFileManager();
-  FileManager &FM = Clang->getFileManager();
+  auto *FM = Clang->createFileManager(VFS);
   ASSERT_TRUE(Clang->ExecuteAction(*Inputs.MakeAction()));
   EXPECT_THAT(
-      PI.getExporters(llvm::cantFail(FM.getFileRef("foo.h")), FM),
-      testing::ElementsAre(llvm::cantFail(FM.getFileRef("exporter.h"))));
+      PI.getExporters(llvm::cantFail(FM->getFileRef("foo.h")), *FM),
+      testing::ElementsAre(llvm::cantFail(FM->getFileRef("exporter.h"))));
 }
 
 TEST_F(PragmaIncludeTest, OutlivesFMAndSM) {
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 0141205adafd5..ab66191a3fc0f 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -367,6 +367,9 @@ def err_drv_optimization_remark_format : Error<
 def err_drv_no_neon_modifier : Error<"[no]neon is not accepted as modifier, please use [no]simd instead">;
 def err_drv_invalid_omp_target : Error<"OpenMP target is invalid: '%0'">;
 def err_drv_incompatible_omp_arch : Error<"OpenMP target architecture '%0' pointer size is incompatible with host '%1'">;
+def err_drv_omp_host_ir_file_not_found : Error<
+  "provided host compiler IR file '%0' is required to generate code for OpenMP "
+  "target regions but cannot be found">;
 def err_drv_omp_host_target_not_supported : Error<
   "target '%0' is not a supported OpenMP host target">;
 def err_drv_ptrauth_not_supported : Error<
@@ -683,9 +686,6 @@ def warn_drv_fine_grained_bitfield_accesses_ignored : Warning<
   "option '-ffine-grained-bitfield-accesses' cannot be enabled together with a sanitizer; flag ignored">,
   InGroup<OptionIgnored>;
 
-def err_drv_profile_instrument_use_path_with_no_kind : Error<
-  "option '-fprofile-instrument-use-path=' requires -fprofile-instrument-use=<kind>">;
-
 def note_drv_verify_prefix_spelling : Note<
   "-verify prefixes must start with a letter and contain only alphanumeric"
   " characters, hyphens, and underscores">;
diff --git a/clang/include/clang/Basic/DiagnosticFrontendKinds.td b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
index fac9d81ee542a..a45500887588a 100644
--- a/clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -327,9 +327,6 @@ def err_target_unsupported_type_for_abi
     : Error<"%0 requires %1 type support, but ABI '%2' does not support it">;
 }
 
-def err_omp_host_ir_file_not_found : Error<
-  "provided host compiler IR file '%0' is required to generate code for OpenMP "
-  "target regions but cannot be found">;
 def err_alias_to_undefined : Error<
   "%select{alias|ifunc}0 must point to a defined "
   "%select{variable or |}1function">;
diff --git a/clang/include/clang/CodeGen/BackendUtil.h b/clang/include/clang/CodeGen/BackendUtil.h
index 9a2b31393735b..bae2798b09f66 100644
--- a/clang/include/clang/CodeGen/BackendUtil.h
+++ b/clang/include/clang/CodeGen/BackendUtil.h
@@ -52,7 +52,7 @@ void EmbedBitcode(llvm::Module *M, const CodeGenOptions &CGOpts,
                   llvm::MemoryBufferRef Buf);
 
 void EmbedObject(llvm::Module *M, const CodeGenOptions &CGOpts,
-                 llvm::vfs::FileSystem &VFS, DiagnosticsEngine &Diags);
+                 DiagnosticsEngine &Diags);
 } // namespace clang
 
 #endif
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 8962a035a4e2a..ab36095da58d4 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3399,8 +3399,7 @@ defm declspec : BoolOption<"f", "declspec",
 def fmodules_cache_path : Joined<["-"], "fmodules-cache-path=">, Group<i_Group>,
   Flags<[]>, Visibility<[ClangOption, CC1Option]>,
   MetaVarName<"<directory>">,
-  HelpText<"Specify the module cache path">,
-  MarshallingInfoString<HeaderSearchOpts<"ModuleCachePath">>;
+  HelpText<"Specify the module cache path">;
 def fmodules_user_build_path : Separate<["-"], "fmodules-user-build-path">, Group<i_Group>,
   Flags<[]>, Visibility<[ClangOption, CC1Option]>,
   MetaVarName<"<directory>">,
@@ -8084,11 +8083,6 @@ def fprofile_instrument_path_EQ : Joined<["-"], "fprofile-instrument-path=">,
     HelpText<"Generate instrumented code to collect execution counts into "
              "<file> (overridden by LLVM_PROFILE_FILE env var)">,
     MarshallingInfoString<CodeGenOpts<"InstrProfileOutput">>;
-def fprofile_instrument_use_EQ : Joined<["-"], "fprofile-instrument-use=">,
-    HelpText<"Enable PGO use instrumentation">, Values<"none,clang,llvm,csllvm,sample-coldcov">,
-    NormalizedValuesScope<"llvm::driver::ProfileInstrKind">,
-    NormalizedValues<["ProfileNone", "ProfileClangInstr", "ProfileIRInstr", "ProfileCSIRInstr", "ProfileIRSampleColdCov"]>,
-    MarshallingInfoEnum<CodeGenOpts<"ProfileUse">, "ProfileNone">;
 def fprofile_instrument_use_path_EQ :
     Joined<["-"], "fprofile-instrument-use-path=">,
     HelpText<"Specify the profile path in PGO use compilation">,
@@ -8892,8 +8886,7 @@ def fopenmp_is_target_device : Flag<["-"], "fopenmp-is-target-device">,
   HelpText<"Generate code only for an OpenMP target device.">;
 def : Flag<["-"], "fopenmp-is-device">, Alias<fopenmp_is_target_device>;
 def fopenmp_host_ir_file_path : Separate<["-"], "fopenmp-host-ir-file-path">,
-  HelpText<"Path to the IR file produced by the frontend for the host.">,
-  MarshallingInfoString<LangOpts<"OMPHostIRFile">>;
+  HelpText<"Path to the IR file produced by the frontend for the host.">;
 
 } // let Visibility = [CC1Option, FC1Option]
 
diff --git a/clang/include/clang/Frontend/ASTUnit.h b/clang/include/clang/Frontend/ASTUnit.h
index b7ba65a8d85bc..1485192e8f1e3 100644
--- a/clang/include/clang/Frontend/ASTUnit.h
+++ b/clang/include/clang/Frontend/ASTUnit.h
@@ -706,15 +706,16 @@ class ASTUnit {
   /// \returns - The initialized ASTUnit or null if the AST failed to load.
   static std::unique_ptr<ASTUnit> LoadFromASTFile(
       StringRef Filename, const PCHContainerReader &PCHContainerRdr,
-      WhatToLoad ToLoad, IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
-      std::shared_ptr<DiagnosticOptions> DiagOpts,
+      WhatToLoad ToLoad, std::shared_ptr<DiagnosticOptions> DiagOpts,
       IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
       const FileSystemOptions &FileSystemOpts,
       const HeaderSearchOptions &HSOpts, const LangOptions *LangOpts = nullptr,
       bool OnlyLocalDecls = false,
       CaptureDiagsKind CaptureDiagnostics = CaptureDiagsKind::None,
       bool AllowASTWithCompilerErrors = false,
-      bool UserFilesAreVolatile = false);
+      bool UserFilesAreVolatile = false,
+      IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS =
+          llvm::vfs::getRealFileSystem());
 
 private:
   /// Helper function for \c LoadFromCompilerInvocation() and
diff --git a/clang/include/clang/Frontend/CompilerInstance.h b/clang/include/clang/Frontend/CompilerInstance.h
index 91782a2694886..72861e573ea34 100644
--- a/clang/include/clang/Frontend/CompilerInstance.h
+++ b/clang/include/clang/Frontend/CompilerInstance.h
@@ -87,9 +87,6 @@ class CompilerInstance : public ModuleLoader {
   /// The options used in this compiler instance.
   std::shared_ptr<CompilerInvocation> Invocation;
 
-  /// The virtual file system instance.
-  IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS;
-
   /// The diagnostics engine instance.
   IntrusiveRefCntPtr<DiagnosticsEngine> Diagnostics;
 
@@ -456,31 +453,7 @@ class CompilerInstance : public ModuleLoader {
   /// @name Virtual File System
   /// @{
 
-  bool hasVirtualFileSystem() const { return VFS != nullptr; }
-
-  /// Create a virtual file system instance based on the invocation.
-  ///
-  /// @param BaseFS The file system that may be used when configuring the final
-  ///               file system, and act as the underlying file system. Must not
-  ///               be NULL.
-  /// @param DC If non-NULL, the diagnostic consumer to be used in case
-  ///           configuring the file system emits diagnostics. Note that the
-  ///           DiagnosticsEngine using the consumer won't obey the
-  ///           --warning-suppression-mappings= flag.
-  void createVirtualFileSystem(IntrusiveRefCntPtr<llvm::vfs::FileSystem>
-                                   BaseFS = llvm::vfs::getRealFileSystem(),
-                               DiagnosticConsumer *DC = nullptr);
-
-  /// Use the given file system.
-  void setVirtualFileSystem(IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS) {
-    VFS = std::move(FS);
-  }
-
-  llvm::vfs::FileSystem &getVirtualFileSystem() const { return *VFS; }
-
-  IntrusiveRefCntPtr<llvm::vfs::FileSystem> getVirtualFileSystemPtr() const {
-    return VFS;
-  }
+  llvm::vfs::FileSystem &getVirtualFileSystem() const;
 
   /// @}
   /// @name File Manager
@@ -718,31 +691,32 @@ class CompilerInstance : public ModuleLoader {
   /// Note that this routine also replaces the diagnostic client,
   /// allocating one if one is not provided.
   ///
+  /// \param VFS is used for any IO needed when creating DiagnosticsEngine. It
+  /// doesn't replace VFS in the CompilerInstance (if any).
+  ///
   /// \param Client If non-NULL, a diagnostic client that will be
   /// attached to (and, then, owned by) the DiagnosticsEngine inside this AST
   /// unit.
   ///
   /// \param ShouldOwnClient If Client is non-NULL, specifies whether
   /// the diagnostic object should take ownership of the client.
-  void createDiagnostics(DiagnosticConsumer *Client = nullptr,
+  void createDiagnostics(llvm::vfs::FileSystem &VFS,
+                         DiagnosticConsumer *Client = nullptr,
                          bool ShouldOwnClient = true);
 
-  /// Create a DiagnosticsEngine object.
+  /// Create a DiagnosticsEngine object with a the TextDiagnosticPrinter.
   ///
   /// If no diagnostic client is provided, this creates a
   /// DiagnosticConsumer that is owned by the returned diagnostic
   /// object, if using directly the caller is responsible for
   /// releasing the returned DiagnosticsEngine's client eventually.
   ///
-  /// \param VFS The file system used to load the suppression mappings file.
-  ///
   /// \param Opts - The diagnostic options; note that the created text
   /// diagnostic object contains a reference to these options.
   ///
   /// \param Client If non-NULL, a diagnostic client that will be
   /// attached to (and, then, owned by) the returned DiagnosticsEngine
-  /// object. If NULL, the returned DiagnosticsEngine will own a newly-created
-  /// client.
+  /// object.
   ///
   /// \param CodeGenOpts If non-NULL, the code gen options in use, which may be
   /// used by some diagnostics printers (for logging purposes only).
@@ -755,10 +729,13 @@ class CompilerInstance : public ModuleLoader {
                     const CodeGenOptions *CodeGenOpts = nullptr);
 
   /// Create the file manager and replace any existing one with it.
-  void createFileManager();
+  ///
+  /// \return The new file manager on success, or null on failure.
+  FileManager *
+  createFileManager(IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS = nullptr);
 
   /// Create the source manager and replace any existing one with it.
-  void createSourceManager();
+  void createSourceManager(FileManager &FileMgr);
 
   /// Create the preprocessor, using the invocation, file, and source managers,
   /// and replace any existing one with it.
@@ -1028,7 +1005,7 @@ class CompilerInstance : public ModuleLoader {
 
   std::pair<std::shared_ptr<llvm::cas::ObjectStore>,
             std::shared_ptr<llvm::cas::ActionCache>>
-  getOrCreateCASDatabases();
+  createCASDatabases();
 };
 
 } // end namespace clang
diff --git a/clang/include/clang/Frontend/CompilerInvocation.h b/clang/include/clang/Frontend/CompilerInvocation.h
index d3455d240d916..4bf5f8ec15b86 100644
--- a/clang/include/clang/Frontend/CompilerInvocation.h
+++ b/clang/include/clang/Frontend/CompilerInvocation.h
@@ -434,8 +434,7 @@ IntrusiveRefCntPtr<llvm::vfs::FileSystem> createVFSFromCompilerInvocation(
 
 IntrusiveRefCntPtr<llvm::vfs::FileSystem> createVFSFromCompilerInvocation(
     const CompilerInvocation &CI, DiagnosticsEngine &Diags,
-    IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
-    std::shared_ptr<llvm::cas::ObjectStore> OverrideCAS = nullptr);
+    IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS);
 
 IntrusiveRefCntPtr<llvm::vfs::FileSystem>
 createVFSFromOverlayFiles(ArrayRef<std::string> VFSOverlayFiles,
diff --git a/clang/include/clang/Frontend/Utils.h b/clang/include/clang/Frontend/Utils.h
index 18bf21c147bde..4e76006905f5a 100644
--- a/clang/include/clang/Frontend/Utils.h
+++ b/clang/include/clang/Frontend/Utils.h
@@ -152,9 +152,8 @@ class ModuleDependencyCollector : public DependencyCollector {
   std::error_code copyToRoot(StringRef Src, StringRef Dst = {});
 
 public:
-  ModuleDependencyCollector(std::string DestDir,
-                            IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS)
-      : DestDir(std::move(DestDir)), Canonicalizer(std::move(VFS)) {}
+  ModuleDependencyCollector(std::string DestDir)
+      : DestDir(std::move(DestDir)) {}
   ~ModuleDependencyCollector() override { writeFileMap(); }
 
   StringRef getDest() { return DestDir; }
diff --git a/clang/include/clang/Lex/HeaderSearch.h b/clang/include/clang/Lex/HeaderSearch.h
index fb95c6187ca74..bccec4dd951d6 100644
--- a/clang/include/clang/Lex/HeaderSearch.h
+++ b/clang/include/clang/Lex/HeaderSearch.h
@@ -966,9 +966,6 @@ void ApplyHeaderSearchOptions(HeaderSearch &HS,
                               const LangOptions &Lang,
                               const llvm::Triple &triple);
 
-void normalizeModuleCachePath(FileManager &FileMgr, StringRef Path,
-                              SmallVectorImpl<char> &NormalizedPath);
-
 } // namespace clang
 
 #endif // LLVM_CLANG_LEX_HEADERSEARCH_H
diff --git a/clang/include/clang/Serialization/ModuleCache.h b/clang/include/clang/Serialization/ModuleCache.h
index ec052c5c18e0a..3117d954a09cc 100644
--- a/clang/include/clang/Serialization/ModuleCache.h
+++ b/clang/include/clang/Serialization/ModuleCache.h
@@ -45,15 +45,11 @@ class ModuleCache : public RefCountedBase<ModuleCache> {
   /// were validated.
   virtual void updateModuleTimestamp(StringRef ModuleFilename) = 0;
 
-  /// Prune module files that haven't been accessed in a long time.
-  virtual void maybePrune(StringRef Path, time_t PruneInterval,
-                          time_t PruneAfter) = 0;
-
   /// Returns this process's view of the module cache.
   virtual InMemoryModuleCache &getInMemoryModuleCache() = 0;
   virtual const InMemoryModuleCache &getInMemoryModuleCache() const = 0;
 
-  // TODO: Virtualize writing/reading PCM files, etc.
+  // TODO: Virtualize writing/reading PCM files, pruning, etc.
 
   virtual ~ModuleCache() = default;
 };
@@ -63,9 +59,6 @@ class ModuleCache : public RefCountedBase<ModuleCache> {
 /// \c CompilerInstance instances participating in building modules for single
 /// translation unit in order to share the same \c InMemoryModuleCache.
 IntrusiveRefCntPtr<ModuleCache> createCrossProcessModuleCache();
-
-/// Shared implementation of `ModuleCache::maybePrune()`.
-void maybePruneImpl(StringRef Path, time_t PruneInterval, time_t PruneAfter);
 } // namespace clang
 
 #endif
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 0f9129d1575a4..32afc66f4b742 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -447,8 +447,7 @@ static bool initTargetOptions(const CompilerInstance &CI,
 
   if (Options.BBSections == llvm::BasicBlockSection::List) {
     ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
-        CI.getVirtualFileSystem().getBufferForFile(
-            CodeGenOpts.BBSections.substr(5));
+        MemoryBuffer::getFile(CodeGenOpts.BBSections.substr(5));
     if (!MBOrErr) {
       Diags.Report(diag::err_fe_unable_to_load_basic_block_sections_file)
           << MBOrErr.getError().message();
@@ -580,8 +579,7 @@ getInstrProfOptions(const CodeGenOptions &CodeGenOpts,
   return Options;
 }
 
-static void setCommandLineOpts(const CodeGenOptions &CodeGenOpts,
-                               vfs::FileSystem &VFS) {
+static void setCommandLineOpts(const CodeGenOptions &CodeGenOpts) {
   SmallVector<const char *, 16> BackendArgs;
   BackendArgs.push_back("clang"); // Fake program name.
   if (!CodeGenOpts.DebugPass.empty()) {
@@ -601,9 +599,8 @@ static void setCommandLineOpts(const CodeGenOptions &CodeGenOpts,
   // FIXME: The command line parser below is not thread-safe and shares a global
   // state, so this call might crash or overwrite the options of another Clang
   // instance in the same process.
-  llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1, BackendArgs.data(),
-                                    /*Overview=*/"", /*Errs=*/nullptr,
-                                    /*VFS=*/&VFS);
+  llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
+                                    BackendArgs.data());
 }
 
 void EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
@@ -804,8 +801,7 @@ static void addSanitizers(const Triple &TargetTriple,
     HWASanPass(SanitizerKind::KernelHWAddress, true);
 
     if (LangOpts.Sanitize.has(SanitizerKind::DataFlow)) {
-      MPM.addPass(DataFlowSanitizerPass(LangOpts.NoSanitizeFiles,
-                                        PB.getVirtualFileSystemPtr()));
+      MPM.addPass(DataFlowSanitizerPass(LangOpts.NoSanitizeFiles));
     }
   };
   if (ClSanitizeOnOptimizerEarlyEP) {
@@ -857,9 +853,9 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
   if (CodeGenOpts.hasProfileIRInstr())
     // -fprofile-generate.
     PGOOpt = PGOOptions(getProfileGenName(CodeGenOpts), "", "",
-                        CodeGenOpts.MemoryProfileUsePath, PGOOptions::IRInstr,
-                        PGOOptions::NoCSAction, ClPGOColdFuncAttr,
-                        CodeGenOpts.DebugInfoForProfiling,
+                        CodeGenOpts.MemoryProfileUsePath, nullptr,
+                        PGOOptions::IRInstr, PGOOptions::NoCSAction,
+                        ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling,
                         /*PseudoProbeForProfiling=*/false,
                         CodeGenOpts.AtomicProfileUpdate);
   else if (CodeGenOpts.hasProfileIRUse()) {
@@ -868,30 +864,32 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
                                                     : PGOOptions::NoCSAction;
     PGOOpt = PGOOptions(CodeGenOpts.ProfileInstrumentUsePath, "",
                         CodeGenOpts.ProfileRemappingFile,
-                        CodeGenOpts.MemoryProfileUsePath, PGOOptions::IRUse,
-                        CSAction, ClPGOColdFuncAttr,
+                        CodeGenOpts.MemoryProfileUsePath, VFS,
+                        PGOOptions::IRUse, CSAction, ClPGOColdFuncAttr,
                         CodeGenOpts.DebugInfoForProfiling);
   } else if (!CodeGenOpts.SampleProfileFile.empty())
     // -fprofile-sample-use
     PGOOpt = PGOOptions(
         CodeGenOpts.SampleProfileFile, "", CodeGenOpts.ProfileRemappingFile,
-        CodeGenOpts.MemoryProfileUsePath, PGOOptions::SampleUse,
+        CodeGenOpts.MemoryProfileUsePath, VFS, PGOOptions::SampleUse,
         PGOOptions::NoCSAction, ClPGOColdFuncAttr,
         CodeGenOpts.DebugInfoForProfiling, CodeGenOpts.PseudoProbeForProfiling);
   else if (!CodeGenOpts.MemoryProfileUsePath.empty())
     // -fmemory-profile-use (without any of the above options)
-    PGOOpt = PGOOptions("", "", "", CodeGenOpts.MemoryProfileUsePath,
+    PGOOpt = PGOOptions("", "", "", CodeGenOpts.MemoryProfileUsePath, VFS,
                         PGOOptions::NoAction, PGOOptions::NoCSAction,
                         ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling);
   else if (CodeGenOpts.PseudoProbeForProfiling)
     // -fpseudo-probe-for-profiling
-    PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", PGOOptions::NoAction,
-                        PGOOptions::NoCSAction, ClPGOColdFuncAttr,
-                        CodeGenOpts.DebugInfoForProfiling, true);
+    PGOOpt =
+        PGOOptions("", "", "", /*MemoryProfile=*/"", nullptr,
+                   PGOOptions::NoAction, PGOOptions::NoCSAction,
+                   ClPGOColdFuncAttr, CodeGenOpts.DebugInfoForProfiling, true);
   else if (CodeGenOpts.DebugInfoForProfiling)
     // -fdebug-info-for-profiling
-    PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", PGOOptions::NoAction,
-                        PGOOptions::NoCSAction, ClPGOColdFuncAttr, true);
+    PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", nullptr,
+                        PGOOptions::NoAction, PGOOptions::NoCSAction,
+                        ClPGOColdFuncAttr, true);
 
   // Check to see if we want to generate a CS profile.
   if (CodeGenOpts.hasProfileCSIRInstr()) {
@@ -907,7 +905,7 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
       PGOOpt->CSAction = PGOOptions::CSIRInstr;
     } else
       PGOOpt = PGOOptions("", getProfileGenName(CodeGenOpts), "",
-                          /*MemoryProfile=*/"", PGOOptions::NoAction,
+                          /*MemoryProfile=*/"", nullptr, PGOOptions::NoAction,
                           PGOOptions::CSIRInstr, ClPGOColdFuncAttr,
                           CodeGenOpts.DebugInfoForProfiling);
   }
@@ -943,7 +941,7 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
       (CodeGenOpts.DebugPassManager || DebugPassStructure),
       CodeGenOpts.VerifyEach, PrintPassOpts);
   SI.registerCallbacks(PIC, &MAM);
-  PassBuilder PB(TM.get(), PTO, PGOOpt, &PIC, CI.getVirtualFileSystemPtr());
+  PassBuilder PB(TM.get(), PTO, PGOOpt, &PIC);
 
   // Handle the assignment tracking feature options.
   switch (CodeGenOpts.getAssignmentTrackingMode()) {
@@ -1121,9 +1119,8 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
     if (std::optional<GCOVOptions> Options =
             getGCOVOptions(CodeGenOpts, LangOpts))
       PB.registerPipelineStartEPCallback(
-          [this, Options](ModulePassManager &MPM, OptimizationLevel Level) {
-            MPM.addPass(
-                GCOVProfilerPass(*Options, CI.getVirtualFileSystemPtr()));
+          [Options](ModulePassManager &MPM, OptimizationLevel Level) {
+            MPM.addPass(GCOVProfilerPass(*Options));
           });
     if (std::optional<InstrProfOptions> Options =
             getInstrProfOptions(CodeGenOpts, LangOpts))
@@ -1297,7 +1294,7 @@ void EmitAssemblyHelper::emitAssembly(BackendAction Action,
                                       std::unique_ptr<raw_pwrite_stream> OS,
 				      std::unique_ptr<raw_pwrite_stream> CasIDOS,
                                       BackendConsumer *BC) {
-  setCommandLineOpts(CodeGenOpts, CI.getVirtualFileSystem());
+  setCommandLineOpts(CodeGenOpts);
 
   bool RequiresCodeGen = actionRequiresCodeGen(Action);
   CreateTargetMachine(RequiresCodeGen);
@@ -1334,7 +1331,7 @@ runThinLTOBackend(CompilerInstance &CI, ModuleSummaryIndex *CombinedIndex,
       ModuleToDefinedGVSummaries;
   CombinedIndex->collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
 
-  setCommandLineOpts(CGOpts, CI.getVirtualFileSystem());
+  setCommandLineOpts(CGOpts);
 
   // We can simply import the values mentioned in the combined index, since
   // we should only invoke this using the individual indexes written out
@@ -1510,13 +1507,13 @@ void clang::EmbedBitcode(llvm::Module *M, const CodeGenOptions &CGOpts,
 }
 
 void clang::EmbedObject(llvm::Module *M, const CodeGenOptions &CGOpts,
-                        llvm::vfs::FileSystem &VFS, DiagnosticsEngine &Diags) {
+                        DiagnosticsEngine &Diags) {
   if (CGOpts.OffloadObjects.empty())
     return;
 
   for (StringRef OffloadObject : CGOpts.OffloadObjects) {
     llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> ObjectOrErr =
-        VFS.getBufferForFile(OffloadObject);
+        llvm::MemoryBuffer::getFileOrSTDIN(OffloadObject);
     if (ObjectOrErr.getError()) {
       auto DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                           "could not open '%0' for embedding");
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index df9201f26aa18..a5f2f0efa2c3b 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -1038,8 +1038,7 @@ CGOpenMPRuntime::CGOpenMPRuntime(CodeGenModule &CGM)
       /*HasRequiresReverseOffload*/ false, /*HasRequiresUnifiedAddress*/ false,
       hasRequiresUnifiedSharedMemory(), /*HasRequiresDynamicAllocators*/ false);
   OMPBuilder.initialize();
-  OMPBuilder.loadOffloadInfoMetadata(*CGM.getFileSystem(),
-                                     CGM.getLangOpts().OpenMPIsTargetDevice
+  OMPBuilder.loadOffloadInfoMetadata(CGM.getLangOpts().OpenMPIsTargetDevice
                                          ? CGM.getLangOpts().OMPHostIRFile
                                          : StringRef{});
   OMPBuilder.setConfig(Config);
@@ -1539,14 +1538,15 @@ static llvm::TargetRegionEntryInfo getEntryInfoFromPresumedLoc(
     SourceManager &SM = CGM.getContext().getSourceManager();
     PresumedLoc PLoc = SM.getPresumedLoc(BeginLoc);
 
-    if (!CGM.getFileSystem()->exists(PLoc.getFilename()))
+    llvm::sys::fs::UniqueID ID;
+    if (llvm::sys::fs::getUniqueID(PLoc.getFilename(), ID)) {
       PLoc = SM.getPresumedLoc(BeginLoc, /*UseLineDirectives=*/false);
+    }
 
     return std::pair<std::string, uint64_t>(PLoc.getFilename(), PLoc.getLine());
   };
 
-  return OMPBuilder.getTargetEntryUniqueInfo(FileInfoCallBack,
-                                             *CGM.getFileSystem(), ParentName);
+  return OMPBuilder.getTargetEntryUniqueInfo(FileInfoCallBack, ParentName);
 }
 
 ConstantAddress CGOpenMPRuntime::getAddrOfDeclareTargetVar(const VarDecl *VD) {
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 61ae1cdcb1395..892db0014fe83 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -1160,8 +1160,7 @@ void CodeGenAction::ExecuteAction() {
     TheModule->setTargetTriple(Triple(TargetOpts.Triple));
   }
 
-  EmbedObject(TheModule.get(), CodeGenOpts, CI.getVirtualFileSystem(),
-              Diagnostics);
+  EmbedObject(TheModule.get(), CodeGenOpts, Diagnostics);
   EmbedBitcode(TheModule.get(), CodeGenOpts, *MainFile);
 
   LLVMContext &Ctx = TheModule->getContext();
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 138c007c2834f..c54c5fe19b974 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -496,15 +496,10 @@ CodeGenModule::CodeGenModule(ASTContext &C,
     auto ReaderOrErr = llvm::IndexedInstrProfReader::create(
         CodeGenOpts.ProfileInstrumentUsePath, *FS,
         CodeGenOpts.ProfileRemappingFile);
-    if (auto E = ReaderOrErr.takeError()) {
-      unsigned DiagID = Diags.getCustomDiagID(
-          DiagnosticsEngine::Error, "Error in reading profile %0: %1");
-      llvm::handleAllErrors(std::move(E), [&](const llvm::ErrorInfoBase &EI) {
-        Diags.Report(DiagID)
-            << CodeGenOpts.ProfileInstrumentUsePath << EI.message();
-      });
-      return;
-    }
+    // We're checking for profile read errors in CompilerInvocation, so if
+    // there was an error it should've already been caught. If it hasn't been
+    // somehow, trip an assertion.
+    assert(ReaderOrErr);
     PGOReader = std::move(ReaderOrErr.get());
   }
 
@@ -536,7 +531,8 @@ CodeGenModule::CodeGenModule(ASTContext &C,
   if (!CGO.MSSecureHotPatchFunctionsFile.empty() ||
       !CGO.MSSecureHotPatchFunctionsList.empty()) {
     if (!CGO.MSSecureHotPatchFunctionsFile.empty()) {
-      auto BufOrErr = FS->getBufferForFile(CGO.MSSecureHotPatchFunctionsFile);
+      auto BufOrErr =
+          llvm::MemoryBuffer::getFile(CGO.MSSecureHotPatchFunctionsFile);
       if (BufOrErr) {
         const llvm::MemoryBuffer &FileBuffer = **BufOrErr;
         for (llvm::line_iterator I(FileBuffer.getMemBufferRef(), true), E;
@@ -592,10 +588,6 @@ void CodeGenModule::createOpenCLRuntime() {
 }
 
 void CodeGenModule::createOpenMPRuntime() {
-  if (!LangOpts.OMPHostIRFile.empty() && !FS->exists(LangOpts.OMPHostIRFile))
-    Diags.Report(diag::err_omp_host_ir_file_not_found)
-        << LangOpts.OMPHostIRFile;
-
   // Select a specialized code generation class based on the target, if any.
   // If it does not exist use the default implementation.
   switch (getTriple().getArch()) {
@@ -1571,7 +1563,7 @@ void CodeGenModule::Release() {
   EmitBackendOptionsMetadata(getCodeGenOpts());
 
   // If there is device offloading code embed it in the host now.
-  EmbedObject(&getModule(), CodeGenOpts, *getFileSystem(), getDiags());
+  EmbedObject(&getModule(), CodeGenOpts, getDiags());
 
   // Set visibility from DLL storage class
   // We do this at the end of LLVM IR generation; after any operation
@@ -8121,17 +8113,12 @@ void CodeGenModule::printPostfixForExternalizedDecl(llvm::raw_ostream &OS,
 
     // Get the UniqueID for the file containing the decl.
     llvm::sys::fs::UniqueID ID;
-    auto Status = FS->status(PLoc.getFilename());
-    if (!Status) {
+    if (llvm::sys::fs::getUniqueID(PLoc.getFilename(), ID)) {
       PLoc = SM.getPresumedLoc(D->getLocation(), /*UseLineDirectives=*/false);
       assert(PLoc.isValid() && "Source location is expected to be valid.");
-      Status = FS->status(PLoc.getFilename());
-    }
-    if (!Status) {
-      SM.getDiagnostics().Report(diag::err_cannot_open_file)
-          << PLoc.getFilename() << Status.getError().message();
-    } else {
-      ID = Status->getUniqueID();
+      if (auto EC = llvm::sys::fs::getUniqueID(PLoc.getFilename(), ID))
+        SM.getDiagnostics().Report(diag::err_cannot_open_file)
+            << PLoc.getFilename() << EC.message();
     }
     OS << llvm::format("%x", ID.getFile()) << llvm::format("%x", ID.getDevice())
        << "_" << llvm::utohexstr(Result.low(), /*LowerCase=*/true, /*Width=*/8);
diff --git a/clang/lib/CrossTU/CrossTranslationUnit.cpp b/clang/lib/CrossTU/CrossTranslationUnit.cpp
index a3fe2f4325e9c..6d0f042d5accd 100644
--- a/clang/lib/CrossTU/CrossTranslationUnit.cpp
+++ b/clang/lib/CrossTU/CrossTranslationUnit.cpp
@@ -13,7 +13,6 @@
 #include "clang/AST/ASTImporter.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/ParentMapContext.h"
-#include "clang/Basic/DiagnosticDriver.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CrossTU/CrossTUDiagnostic.h"
 #include "clang/Frontend/ASTUnit.h"
@@ -238,16 +237,7 @@ template <typename T> static bool hasBodyOrInit(const T *D) {
 }
 
 CrossTranslationUnitContext::CrossTranslationUnitContext(CompilerInstance &CI)
-    : Context(CI.getASTContext()), ASTStorage(CI) {
-  if (CI.getAnalyzerOpts().ShouldEmitErrorsOnInvalidConfigValue &&
-      !CI.getAnalyzerOpts().CTUDir.empty()) {
-    auto S = CI.getVirtualFileSystem().status(CI.getAnalyzerOpts().CTUDir);
-    if (!S || S->getType() != llvm::sys::fs::file_type::directory_file)
-      CI.getDiagnostics().Report(diag::err_analyzer_config_invalid_input)
-          << "ctu-dir"
-          << "a filename";
-  }
-}
+    : Context(CI.getASTContext()), ASTStorage(CI) {}
 
 CrossTranslationUnitContext::~CrossTranslationUnitContext() {}
 
@@ -578,8 +568,8 @@ CrossTranslationUnitContext::ASTLoader::loadFromDump(StringRef ASTDumpPath) {
       new DiagnosticsEngine(DiagID, *DiagOpts, DiagClient));
   return ASTUnit::LoadFromASTFile(
       ASTDumpPath, CI.getPCHContainerOperations()->getRawReader(),
-      ASTUnit::LoadEverything, CI.getVirtualFileSystemPtr(), DiagOpts, Diags,
-      CI.getFileSystemOpts(), CI.getHeaderSearchOpts());
+      ASTUnit::LoadEverything, DiagOpts, Diags, CI.getFileSystemOpts(),
+      CI.getHeaderSearchOpts());
 }
 
 /// Load the AST from a source-file, which is supposed to be located inside the
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 33ebc7cd25f62..1c2d82ff10c2f 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -41,7 +41,6 @@
 #include "llvm/Frontend/Debug/Options.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Option/ArgList.h"
-#include "llvm/ProfileData/InstrProfReader.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Compression.h"
@@ -503,47 +502,19 @@ static void addPGOAndCoverageFlags(const ToolChain &TC, Compilation &C,
   }
 
   if (ProfileUseArg) {
-    SmallString<128> UsePathBuf;
-    StringRef UsePath;
     if (ProfileUseArg->getOption().matches(options::OPT_fprofile_instr_use_EQ))
-      UsePath = ProfileUseArg->getValue();
+      CmdArgs.push_back(Args.MakeArgString(
+          Twine("-fprofile-instrument-use-path=") + ProfileUseArg->getValue()));
     else if ((ProfileUseArg->getOption().matches(
                   options::OPT_fprofile_use_EQ) ||
               ProfileUseArg->getOption().matches(
                   options::OPT_fprofile_instr_use))) {
-      UsePathBuf =
-          ProfileUseArg->getNumValues() == 0 ? "" : ProfileUseArg->getValue();
-      if (UsePathBuf.empty() || llvm::sys::fs::is_directory(UsePathBuf))
-        llvm::sys::path::append(UsePathBuf, "default.profdata");
-      UsePath = UsePathBuf;
-    }
-    auto ReaderOrErr =
-        llvm::IndexedInstrProfReader::create(UsePath, D.getVFS());
-    if (auto E = ReaderOrErr.takeError()) {
-      auto DiagID = D.getDiags().getCustomDiagID(
-          DiagnosticsEngine::Error, "Error in reading profile %0: %1");
-      llvm::handleAllErrors(std::move(E), [&](const llvm::ErrorInfoBase &EI) {
-        D.Diag(DiagID) << UsePath.str() << EI.message();
-      });
-    } else {
-      std::unique_ptr<llvm::IndexedInstrProfReader> PGOReader =
-          std::move(ReaderOrErr.get());
-      StringRef UseKind;
-      // Currently memprof profiles are only added at the IR level. Mark the
-      // profile type as IR in that case as well and the subsequent matching
-      // needs to detect which is available (might be one or both).
-      if (PGOReader->isIRLevelProfile() || PGOReader->hasMemoryProfile()) {
-        if (PGOReader->hasCSIRLevelProfile())
-          UseKind = "csllvm";
-        else
-          UseKind = "llvm";
-      } else
-        UseKind = "clang";
-
-      CmdArgs.push_back(
-          Args.MakeArgString("-fprofile-instrument-use=" + UseKind));
+      SmallString<128> Path(
+          ProfileUseArg->getNumValues() == 0 ? "" : ProfileUseArg->getValue());
+      if (Path.empty() || llvm::sys::fs::is_directory(Path))
+        llvm::sys::path::append(Path, "default.profdata");
       CmdArgs.push_back(
-          Args.MakeArgString("-fprofile-instrument-use-path=" + UsePath));
+          Args.MakeArgString(Twine("-fprofile-instrument-use-path=") + Path));
     }
   }
 
diff --git a/clang/lib/ExtractAPI/ExtractAPIConsumer.cpp b/clang/lib/ExtractAPI/ExtractAPIConsumer.cpp
index 6966d4097d64a..1087eb3001856 100644
--- a/clang/lib/ExtractAPI/ExtractAPIConsumer.cpp
+++ b/clang/lib/ExtractAPI/ExtractAPIConsumer.cpp
@@ -444,7 +444,8 @@ bool ExtractAPIAction::PrepareToExecuteAction(CompilerInstance &CI) {
     return true;
 
   if (!CI.hasFileManager())
-    CI.createFileManager();
+    if (!CI.createFileManager())
+      return false;
 
   auto Kind = Inputs[0].getKind();
 
diff --git a/clang/lib/Frontend/ASTMerge.cpp b/clang/lib/Frontend/ASTMerge.cpp
index 51925ec85e7b6..a4ce88351e28e 100644
--- a/clang/lib/Frontend/ASTMerge.cpp
+++ b/clang/lib/Frontend/ASTMerge.cpp
@@ -47,8 +47,7 @@ void ASTMergeAction::ExecuteAction() {
         /*ShouldOwnClient=*/true));
     std::unique_ptr<ASTUnit> Unit = ASTUnit::LoadFromASTFile(
         ASTFiles[I], CI.getPCHContainerReader(), ASTUnit::LoadEverything,
-        CI.getVirtualFileSystemPtr(), nullptr, Diags, CI.getFileSystemOpts(),
-        CI.getHeaderSearchOpts());
+        nullptr, Diags, CI.getFileSystemOpts(), CI.getHeaderSearchOpts());
 
     if (!Unit)
       continue;
diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index e4390b9f6f9d6..a99e176291582 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -799,13 +799,12 @@ void ASTUnit::ConfigureDiags(IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
 
 std::unique_ptr<ASTUnit> ASTUnit::LoadFromASTFile(
     StringRef Filename, const PCHContainerReader &PCHContainerRdr,
-    WhatToLoad ToLoad, IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
-    std::shared_ptr<DiagnosticOptions> DiagOpts,
+    WhatToLoad ToLoad, std::shared_ptr<DiagnosticOptions> DiagOpts,
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
     const FileSystemOptions &FileSystemOpts, const HeaderSearchOptions &HSOpts,
     const LangOptions *LangOpts, bool OnlyLocalDecls,
     CaptureDiagsKind CaptureDiagnostics, bool AllowASTWithCompilerErrors,
-    bool UserFilesAreVolatile) {
+    bool UserFilesAreVolatile, IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
   std::unique_ptr<ASTUnit> AST(new ASTUnit(true));
 
   // Recover resources if we crash before exiting this method.
@@ -1180,14 +1179,10 @@ bool ASTUnit::Parse(std::shared_ptr<PCHContainerOperations> PCHContainerOps,
   // Ensure that Clang has a FileManager with the right VFS, which may have
   // changed above in AddImplicitPreamble.  If VFS is nullptr, rely on
   // createFileManager to create one.
-  if (VFS && FileMgr && &FileMgr->getVirtualFileSystem() == VFS) {
-    Clang->setVirtualFileSystem(std::move(VFS));
+  if (VFS && FileMgr && &FileMgr->getVirtualFileSystem() == VFS)
     Clang->setFileManager(&*FileMgr);
-  } else {
-    Clang->setVirtualFileSystem(std::move(VFS));
-    Clang->createFileManager();
-    FileMgr = Clang->getFileManagerPtr().get();
-  }
+  else
+    FileMgr = Clang->createFileManager(std::move(VFS));
 
   // Recover resources if we crash before exiting this method.
   llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance>
diff --git a/clang/lib/Frontend/ChainedIncludesSource.cpp b/clang/lib/Frontend/ChainedIncludesSource.cpp
index 990fb3c32a3d0..f9a398dbfb90f 100644
--- a/clang/lib/Frontend/ChainedIncludesSource.cpp
+++ b/clang/lib/Frontend/ChainedIncludesSource.cpp
@@ -124,12 +124,11 @@ IntrusiveRefCntPtr<ExternalSemaSource> clang::createChainedIncludesSource(
 
     auto Clang = std::make_unique<CompilerInstance>(
         std::move(CInvok), CI.getPCHContainerOperations());
-    Clang->createVirtualFileSystem();
     Clang->setDiagnostics(Diags.get());
     Clang->setTarget(TargetInfo::CreateTargetInfo(
         Clang->getDiagnostics(), Clang->getInvocation().getTargetOpts()));
     Clang->createFileManager();
-    Clang->createSourceManager();
+    Clang->createSourceManager(Clang->getFileManager());
     Clang->createPreprocessor(TU_Prefix);
     Clang->getDiagnosticClient().BeginSourceFile(Clang->getLangOpts(),
                                                  &Clang->getPreprocessor());
diff --git a/clang/lib/Frontend/CompileJobCache.cpp b/clang/lib/Frontend/CompileJobCache.cpp
index c210d075d26b1..6e32eb80edb87 100644
--- a/clang/lib/Frontend/CompileJobCache.cpp
+++ b/clang/lib/Frontend/CompileJobCache.cpp
@@ -271,7 +271,7 @@ static std::string fixupRelativePath(const std::string &Path, FileManager &FM,
   // Apply "normal" working directory.
   if (!WorkingDir.empty()) {
     SmallString<128> Tmp(Path);
-    llvm::sys::path::make_absolute(WorkingDir, Tmp);
+    llvm::sys::fs::make_absolute(WorkingDir, Tmp);
     return std::string(Tmp);
   }
   return Path;
@@ -296,7 +296,7 @@ std::optional<int> CompileJobCache::initialize(CompilerInstance &Clang) {
   if (!CacheCompileJob)
     return std::nullopt;
 
-  std::tie(CAS, Cache) = Clang.getOrCreateCASDatabases();
+  std::tie(CAS, Cache) = Clang.createCASDatabases();
   if (!CAS || !Cache)
     return 1; // Exit with error!
 
@@ -613,8 +613,8 @@ Expected<std::optional<int>> CompileJobCache::replayCachedResult(
     std::optional<llvm::cas::CASID> *OutMCOutputID) {
   CompilerInstance Clang(std::move(Invok));
   llvm::raw_svector_ostream DiagOS(DiagText);
-  Clang.createVirtualFileSystem(llvm::vfs::getRealFileSystem());
   Clang.createDiagnostics(
+      *llvm::vfs::getRealFileSystem(),
       new TextDiagnosticPrinter(DiagOS, Clang.getDiagnosticOpts()));
   Clang.setVerboseOutputStream(DiagOS);
 
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index b73095f076fe1..2f25e3f9e8643 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -172,14 +172,11 @@ bool CompilerInstance::createTarget() {
   return true;
 }
 
+llvm::vfs::FileSystem &CompilerInstance::getVirtualFileSystem() const {
+  return getFileManager().getVirtualFileSystem();
+}
+
 void CompilerInstance::setFileManager(FileManager *Value) {
-  if (Value == nullptr) {
-    FileMgr = nullptr;
-    return;
-  }
-  if (VFS == nullptr)
-    VFS = Value->getVirtualFileSystemPtr();
-  assert(VFS == Value->getVirtualFileSystemPtr());
   FileMgr = Value;
 }
 
@@ -279,35 +276,24 @@ static void collectIncludePCH(CompilerInstance &CI,
 
 static void collectVFSEntries(CompilerInstance &CI,
                               std::shared_ptr<ModuleDependencyCollector> MDC) {
+  if (CI.getHeaderSearchOpts().VFSOverlayFiles.empty())
+    return;
+
   // Collect all VFS found.
   SmallVector<llvm::vfs::YAMLVFSEntry, 16> VFSEntries;
-  CI.getVirtualFileSystem().visit([&](llvm::vfs::FileSystem &VFS) {
-    if (auto *RedirectingVFS = dyn_cast<llvm::vfs::RedirectingFileSystem>(&VFS))
-      llvm::vfs::collectVFSEntries(*RedirectingVFS, VFSEntries);
-  });
+  for (const std::string &VFSFile : CI.getHeaderSearchOpts().VFSOverlayFiles) {
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Buffer =
+        llvm::MemoryBuffer::getFile(VFSFile);
+    if (!Buffer)
+      return;
+    llvm::vfs::collectVFSFromYAML(std::move(Buffer.get()),
+                                  /*DiagHandler*/ nullptr, VFSFile, VFSEntries);
+  }
 
   for (auto &E : VFSEntries)
     MDC->addFile(E.VPath, E.RPath);
 }
 
-void CompilerInstance::createVirtualFileSystem(
-    IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS, DiagnosticConsumer *DC) {
-  DiagnosticOptions DiagOpts;
-  DiagnosticsEngine Diags(new DiagnosticIDs, DiagOpts, DC,
-                          /*ShouldOwnClient=*/false);
-
-  std::tie(CAS, ActionCache) =
-      getInvocation().getCASOpts().getOrCreateDatabases(
-          Diags, /*CreateEmptyCASOnFailure=*/false);
-
-  VFS = createVFSFromCompilerInvocation(getInvocation(), Diags,
-                                        std::move(BaseFS), CAS);
-  // FIXME: Should this go into createVFSFromCompilerInvocation?
-  if (getFrontendOpts().ShowStats)
-    VFS =
-        llvm::makeIntrusiveRefCnt<llvm::vfs::TracingFileSystem>(std::move(VFS));
-}
-
 // Diagnostics
 static void SetUpDiagnosticLog(DiagnosticOptions &DiagOpts,
                                const CodeGenOptions *CodeGenOpts,
@@ -359,10 +345,11 @@ static void SetupSerializedDiagnostics(DiagnosticOptions &DiagOpts,
   }
 }
 
-void CompilerInstance::createDiagnostics(DiagnosticConsumer *Client,
+void CompilerInstance::createDiagnostics(llvm::vfs::FileSystem &VFS,
+                                         DiagnosticConsumer *Client,
                                          bool ShouldOwnClient) {
-  Diagnostics = createDiagnostics(getVirtualFileSystem(), getDiagnosticOpts(),
-                                  Client, ShouldOwnClient, &getCodeGenOpts());
+  Diagnostics = createDiagnostics(VFS, getDiagnosticOpts(), Client,
+                                  ShouldOwnClient, &getCodeGenOpts());
 }
 
 IntrusiveRefCntPtr<DiagnosticsEngine> CompilerInstance::createDiagnostics(
@@ -401,18 +388,24 @@ IntrusiveRefCntPtr<DiagnosticsEngine> CompilerInstance::createDiagnostics(
 
 // File Manager
 
-void CompilerInstance::createFileManager() {
-  assert(VFS && "CompilerInstance needs a VFS for creating FileManager");
-  FileMgr = llvm::makeIntrusiveRefCnt<FileManager>(getFileSystemOpts(), VFS);
+FileManager *CompilerInstance::createFileManager(
+    IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
+  if (!VFS)
+    VFS = FileMgr ? &FileMgr->getVirtualFileSystem()
+                  : createVFSFromCompilerInvocation(getInvocation(),
+                                                    getDiagnostics(), CAS);
+  assert(VFS && "FileManager has no VFS?");
+  if (getFrontendOpts().ShowStats)
+    VFS =
+        llvm::makeIntrusiveRefCnt<llvm::vfs::TracingFileSystem>(std::move(VFS));
+  FileMgr = new FileManager(getFileSystemOpts(), std::move(VFS));
+  return FileMgr.get();
 }
 
 // Source Manager
 
-void CompilerInstance::createSourceManager() {
-  assert(Diagnostics && "DiagnosticsEngine needed for creating SourceManager");
-  assert(FileMgr && "FileManager needed for creating SourceManager");
-  SourceMgr = new SourceManager(getDiagnostics(),
-                                                       getFileManager());
+void CompilerInstance::createSourceManager(FileManager &FileMgr) {
+  SourceMgr = new SourceManager(getDiagnostics(), FileMgr);
 }
 
 // Initialize the remapping of files to alternative contents, e.g.,
@@ -524,7 +517,7 @@ void CompilerInstance::createPreprocessor(TranslationUnitKind TUKind) {
   // then we're the top level compiler instance and need to create one.
   if (!ModuleDepCollector && !DepOpts.ModuleDependencyOutputDir.empty()) {
     ModuleDepCollector = std::make_shared<ModuleDependencyCollector>(
-        DepOpts.ModuleDependencyOutputDir, getVirtualFileSystemPtr());
+        DepOpts.ModuleDependencyOutputDir);
   }
 
   // If there is a module dep collector, register with other dep collectors
@@ -566,16 +559,9 @@ void CompilerInstance::createPreprocessor(TranslationUnitKind TUKind) {
 }
 
 std::string CompilerInstance::getSpecificModuleCachePath(StringRef ModuleHash) {
-  assert(FileMgr && "Specific module cache path requires a FileManager");
-
-  if (getHeaderSearchOpts().ModuleCachePath.empty())
-    return "";
-
   // Set up the module path, including the hash for the module-creation options.
-  SmallString<256> SpecificModuleCache;
-  normalizeModuleCachePath(*FileMgr, getHeaderSearchOpts().ModuleCachePath,
-                           SpecificModuleCache);
-  if (!getHeaderSearchOpts().DisableModuleHash)
+  SmallString<256> SpecificModuleCache(getHeaderSearchOpts().ModuleCachePath);
+  if (!SpecificModuleCache.empty() && !getHeaderSearchOpts().DisableModuleHash)
     llvm::sys::path::append(SpecificModuleCache, ModuleHash);
   return std::string(SpecificModuleCache);
 }
@@ -973,7 +959,7 @@ llvm::vfs::OutputBackend &CompilerInstance::getOrCreateOutputBackend() {
 
 std::pair<std::shared_ptr<llvm::cas::ObjectStore>,
           std::shared_ptr<llvm::cas::ActionCache>>
-CompilerInstance::getOrCreateCASDatabases() {
+CompilerInstance::createCASDatabases() {
   // Create a new CAS databases from the CompilerInvocation. Future calls to
   // createFileManager() will use the same CAS.
   std::tie(CAS, ActionCache) =
@@ -985,13 +971,13 @@ CompilerInstance::getOrCreateCASDatabases() {
 
 llvm::cas::ObjectStore &CompilerInstance::getOrCreateObjectStore() {
   if (!CAS)
-    getOrCreateCASDatabases();
+    createCASDatabases();
   return *CAS;
 }
 
 llvm::cas::ActionCache &CompilerInstance::getOrCreateActionCache() {
   if (!ActionCache)
-    getOrCreateCASDatabases();
+    createCASDatabases();
   return *ActionCache;
 }
 
@@ -1402,28 +1388,27 @@ std::unique_ptr<CompilerInstance> CompilerInstance::cloneForModuleCompileImpl(
   auto &Inv = Instance.getInvocation();
 
   if (ThreadSafeConfig) {
-    Instance.setVirtualFileSystem(ThreadSafeConfig->getVFS());
-    Instance.createFileManager();
+    Instance.createFileManager(ThreadSafeConfig->getVFS());
   } else if (FrontendOpts.ModulesShareFileManager) {
-    Instance.setVirtualFileSystem(getVirtualFileSystemPtr());
     Instance.setFileManager(&getFileManager());
   } else {
-    Instance.setVirtualFileSystem(&getVirtualFileSystem());
-    Instance.createFileManager();
+    Instance.createFileManager(&getVirtualFileSystem());
   }
 
   if (ThreadSafeConfig) {
-    Instance.createDiagnostics(&ThreadSafeConfig->getDiagConsumer(),
+    Instance.createDiagnostics(Instance.getVirtualFileSystem(),
+                               &ThreadSafeConfig->getDiagConsumer(),
                                /*ShouldOwnClient=*/false);
   } else {
     Instance.createDiagnostics(
+        Instance.getVirtualFileSystem(),
         new ForwardingDiagnosticConsumer(getDiagnosticClient()),
         /*ShouldOwnClient=*/true);
   }
   if (llvm::is_contained(DiagOpts.SystemHeaderWarningsModules, ModuleName))
     Instance.getDiagnostics().setSuppressSystemWarnings(false);
 
-  Instance.createSourceManager();
+  Instance.createSourceManager(Instance.getFileManager());
   SourceManager &SourceMgr = Instance.getSourceManager();
 
   if (ThreadSafeConfig) {
@@ -1853,6 +1838,90 @@ static void checkConfigMacros(Preprocessor &PP, Module *M,
   }
 }
 
+/// Write a new timestamp file with the given path.
+static void writeTimestampFile(StringRef TimestampFile) {
+  std::error_code EC;
+  llvm::raw_fd_ostream Out(TimestampFile.str(), EC, llvm::sys::fs::OF_None);
+}
+
+/// Prune the module cache of modules that haven't been accessed in
+/// a long time.
+static void pruneModuleCache(const HeaderSearchOptions &HSOpts) {
+  llvm::sys::fs::file_status StatBuf;
+  llvm::SmallString<128> TimestampFile;
+  TimestampFile = HSOpts.ModuleCachePath;
+  assert(!TimestampFile.empty());
+  llvm::sys::path::append(TimestampFile, "modules.timestamp");
+
+  // Try to stat() the timestamp file.
+  if (std::error_code EC = llvm::sys::fs::status(TimestampFile, StatBuf)) {
+    // If the timestamp file wasn't there, create one now.
+    if (EC == std::errc::no_such_file_or_directory) {
+      writeTimestampFile(TimestampFile);
+    }
+    return;
+  }
+
+  // Check whether the time stamp is older than our pruning interval.
+  // If not, do nothing.
+  time_t TimeStampModTime =
+      llvm::sys::toTimeT(StatBuf.getLastModificationTime());
+  time_t CurrentTime = time(nullptr);
+  if (CurrentTime - TimeStampModTime <= time_t(HSOpts.ModuleCachePruneInterval))
+    return;
+
+  // Write a new timestamp file so that nobody else attempts to prune.
+  // There is a benign race condition here, if two Clang instances happen to
+  // notice at the same time that the timestamp is out-of-date.
+  writeTimestampFile(TimestampFile);
+
+  // Walk the entire module cache, looking for unused module files and module
+  // indices.
+  std::error_code EC;
+  for (llvm::sys::fs::directory_iterator Dir(HSOpts.ModuleCachePath, EC),
+       DirEnd;
+       Dir != DirEnd && !EC; Dir.increment(EC)) {
+    // If we don't have a directory, there's nothing to look into.
+    if (!llvm::sys::fs::is_directory(Dir->path()))
+      continue;
+
+    // Walk all of the files within this directory.
+    for (llvm::sys::fs::directory_iterator File(Dir->path(), EC), FileEnd;
+         File != FileEnd && !EC; File.increment(EC)) {
+      // We only care about module and global module index files.
+      StringRef Extension = llvm::sys::path::extension(File->path());
+      if (Extension != ".pcm" && Extension != ".timestamp" &&
+          llvm::sys::path::filename(File->path()) != "modules.idx")
+        continue;
+
+      // Look at this file. If we can't stat it, there's nothing interesting
+      // there.
+      if (llvm::sys::fs::status(File->path(), StatBuf))
+        continue;
+
+      // If the file has been used recently enough, leave it there.
+      time_t FileAccessTime = llvm::sys::toTimeT(StatBuf.getLastAccessedTime());
+      if (CurrentTime - FileAccessTime <=
+              time_t(HSOpts.ModuleCachePruneAfter)) {
+        continue;
+      }
+
+      // Remove the file.
+      llvm::sys::fs::remove(File->path());
+
+      // Remove the timestamp file.
+      std::string TimpestampFilename = File->path() + ".timestamp";
+      llvm::sys::fs::remove(TimpestampFilename);
+    }
+
+    // If we removed all of the files in the directory, remove the directory
+    // itself.
+    if (llvm::sys::fs::directory_iterator(Dir->path(), EC) ==
+            llvm::sys::fs::directory_iterator() && !EC)
+      llvm::sys::fs::remove(Dir->path());
+  }
+}
+
 void CompilerInstance::createASTReader() {
   if (TheASTReader)
     return;
@@ -1863,10 +1932,11 @@ void CompilerInstance::createASTReader() {
   // If we're implicitly building modules but not currently recursively
   // building a module, check whether we need to prune the module cache.
   if (getSourceManager().getModuleBuildStack().empty() &&
-      !getPreprocessor().getHeaderSearchInfo().getModuleCachePath().empty())
-    ModCache->maybePrune(getHeaderSearchOpts().ModuleCachePath,
-                         getHeaderSearchOpts().ModuleCachePruneInterval,
-                         getHeaderSearchOpts().ModuleCachePruneAfter);
+      !getPreprocessor().getHeaderSearchInfo().getModuleCachePath().empty() &&
+      getHeaderSearchOpts().ModuleCachePruneInterval > 0 &&
+      getHeaderSearchOpts().ModuleCachePruneAfter > 0) {
+    pruneModuleCache(getHeaderSearchOpts());
+  }
 
   HeaderSearchOptions &HSOpts = getHeaderSearchOpts();
   std::string Sysroot = HSOpts.Sysroot;
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index c4c738ef3604c..8602b16c2f526 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1373,6 +1373,15 @@ static void parseAnalyzerConfigs(AnalyzerOptions &AnOpts,
   if (AnOpts.ShouldTrackConditionsDebug && !AnOpts.ShouldTrackConditions)
     Diags->Report(diag::err_analyzer_config_invalid_input)
         << "track-conditions-debug" << "'track-conditions' to also be enabled";
+
+  if (!AnOpts.CTUDir.empty() && !llvm::sys::fs::is_directory(AnOpts.CTUDir))
+    Diags->Report(diag::err_analyzer_config_invalid_input) << "ctu-dir"
+                                                           << "a filename";
+
+  if (!AnOpts.ModelPath.empty() &&
+      !llvm::sys::fs::is_directory(AnOpts.ModelPath))
+    Diags->Report(diag::err_analyzer_config_invalid_input) << "model-path"
+                                                           << "a filename";
 }
 
 /// Generate a remark argument. This is an inverse of `ParseOptimizationRemark`.
@@ -1527,10 +1536,9 @@ static std::string serializeXRayInstrumentationBundle(const XRayInstrSet &S) {
 static IntrusiveRefCntPtr<llvm::vfs::FileSystem>
 createBaseFS(const FileSystemOptions &FSOpts, const FrontendOptions &FEOpts,
              const CASOptions &CASOpts, DiagnosticsEngine &Diags,
-             IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
              std::shared_ptr<llvm::cas::ObjectStore> OverrideCAS) {
   if (FSOpts.CASFileSystemRootID.empty() && FEOpts.CASIncludeTreeID.empty())
-    return BaseFS;
+    return llvm::vfs::getRealFileSystem();
 
   // If no CAS was provided, create one with CASOptions.
   std::shared_ptr<llvm::cas::ObjectStore> CAS = std::move(OverrideCAS);
@@ -1621,6 +1629,34 @@ createBaseFS(const FileSystemOptions &FSOpts, const FrontendOptions &FEOpts,
   return FS;
 }
 
+// Set the profile kind using fprofile-instrument-use-path.
+static void setPGOUseInstrumentor(CodeGenOptions &Opts,
+                                  const Twine &ProfileName,
+                                  llvm::vfs::FileSystem &FS,
+                                  DiagnosticsEngine &Diags) {
+  auto ReaderOrErr = llvm::IndexedInstrProfReader::create(ProfileName, FS);
+  if (auto E = ReaderOrErr.takeError()) {
+    unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
+                                            "Error in reading profile %0: %1");
+    llvm::handleAllErrors(std::move(E), [&](const llvm::ErrorInfoBase &EI) {
+      Diags.Report(DiagID) << ProfileName.str() << EI.message();
+    });
+    return;
+  }
+  std::unique_ptr<llvm::IndexedInstrProfReader> PGOReader =
+    std::move(ReaderOrErr.get());
+  // Currently memprof profiles are only added at the IR level. Mark the profile
+  // type as IR in that case as well and the subsequent matching needs to detect
+  // which is available (might be one or both).
+  if (PGOReader->isIRLevelProfile() || PGOReader->hasMemoryProfile()) {
+    if (PGOReader->hasCSIRLevelProfile())
+      Opts.setProfileUse(llvm::driver::ProfileInstrKind::ProfileCSIRInstr);
+    else
+      Opts.setProfileUse(llvm::driver::ProfileInstrKind::ProfileIRInstr);
+  } else
+    Opts.setProfileUse(llvm::driver::ProfileInstrKind::ProfileClangInstr);
+}
+
 void CompilerInvocation::setDefaultPointerAuthOptions(
     PointerAuthOptions &Opts, const LangOptions &LangOpts,
     const llvm::Triple &Triple) {
@@ -2186,6 +2222,11 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
             : llvm::codegenoptions::DebugTemplateNamesKind::Mangled);
   }
 
+  if (!Opts.ProfileInstrumentUsePath.empty()) {
+    auto FS = createBaseFS(FSOpts, FEOpts, CASOpts, Diags, nullptr);
+    setPGOUseInstrumentor(Opts, Opts.ProfileInstrumentUsePath, *FS, Diags);
+  }
+
   if (const Arg *A = Args.getLastArg(OPT_ftime_report, OPT_ftime_report_EQ,
                                      OPT_ftime_report_json)) {
     Opts.TimePasses = true;
@@ -3545,6 +3586,9 @@ static void GenerateHeaderSearchArgs(const HeaderSearchOptions &Opts,
   if (Opts.UseLibcxx)
     GenerateArg(Consumer, OPT_stdlib_EQ, "libc++");
 
+  if (!Opts.ModuleCachePath.empty())
+    GenerateArg(Consumer, OPT_fmodules_cache_path, Opts.ModuleCachePath);
+
   for (const auto &File : Opts.PrebuiltModuleFiles)
     GenerateArg(Consumer, OPT_fmodule_file, File.first + "=" + File.second);
 
@@ -3647,7 +3691,8 @@ static void GenerateHeaderSearchArgs(const HeaderSearchOptions &Opts,
 }
 
 static bool ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
-                                  DiagnosticsEngine &Diags) {
+                                  DiagnosticsEngine &Diags,
+                                  const std::string &WorkingDir) {
   unsigned NumErrorsBefore = Diags.getNumErrors();
 
   HeaderSearchOptions *HeaderSearchOpts = &Opts;
@@ -3660,6 +3705,17 @@ static bool ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
   if (const Arg *A = Args.getLastArg(OPT_stdlib_EQ))
     Opts.UseLibcxx = (strcmp(A->getValue(), "libc++") == 0);
 
+  // Canonicalize -fmodules-cache-path before storing it.
+  SmallString<128> P(Args.getLastArgValue(OPT_fmodules_cache_path));
+  if (!(P.empty() || llvm::sys::path::is_absolute(P))) {
+    if (WorkingDir.empty())
+      llvm::sys::fs::make_absolute(P);
+    else
+      llvm::sys::fs::make_absolute(WorkingDir, P);
+  }
+  llvm::sys::path::remove_dots(P);
+  Opts.ModuleCachePath = std::string(P);
+
   // Only the -fmodule-file=<name>=<file> form.
   for (const auto *A : Args.filtered(OPT_fmodule_file)) {
     StringRef Val = A->getValue();
@@ -4217,6 +4273,9 @@ void CompilerInvocationBase::GenerateLangArgs(const LangOptions &Opts,
     GenerateArg(Consumer, OPT_offload_targets_EQ, Targets);
   }
 
+  if (!Opts.OMPHostIRFile.empty())
+    GenerateArg(Consumer, OPT_fopenmp_host_ir_file_path, Opts.OMPHostIRFile);
+
   if (Opts.OpenMPCUDAMode)
     GenerateArg(Consumer, OPT_fopenmp_cuda_mode);
 
@@ -4842,6 +4901,15 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
     }
   }
 
+  // Get OpenMP host file path if any and report if a non existent file is
+  // found
+  if (Arg *A = Args.getLastArg(options::OPT_fopenmp_host_ir_file_path)) {
+    Opts.OMPHostIRFile = A->getValue();
+    if (!llvm::sys::fs::exists(Opts.OMPHostIRFile))
+      Diags.Report(diag::err_drv_omp_host_ir_file_not_found)
+          << Opts.OMPHostIRFile;
+  }
+
   // Set CUDA mode for OpenMP target NVPTX/AMDGCN if specified in options
   Opts.OpenMPCUDAMode = Opts.OpenMPIsTargetDevice &&
                         (T.isNVPTX() || T.isAMDGCN()) &&
@@ -5514,7 +5582,8 @@ bool CompilerInvocation::CreateFromArgsImpl(
   InputKind DashX = Res.getFrontendOpts().DashX;
   ParseTargetArgs(Res.getTargetOpts(), Args, Diags);
   llvm::Triple T(Res.getTargetOpts().Triple);
-  ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args, Diags);
+  ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args, Diags,
+                        Res.getFileSystemOpts().WorkingDir);
   if (Res.getFrontendOpts().GenReducedBMI ||
       Res.getFrontendOpts().ProgramAction ==
           frontend::GenerateReducedModuleInterface ||
@@ -5610,11 +5679,6 @@ bool CompilerInvocation::CreateFromArgsImpl(
     append_range(Res.getCodeGenOpts().CommandLineArgs, CommandLineArgs);
   }
 
-  if (!Res.getCodeGenOpts().ProfileInstrumentUsePath.empty() &&
-      Res.getCodeGenOpts().getProfileUse() ==
-          llvm::driver::ProfileInstrKind::ProfileNone)
-    Diags.Report(diag::err_drv_profile_instrument_use_path_with_no_kind);
-
   FixupInvocation(Res, Diags, Args, DashX);
 
   return Diags.getNumErrors() == NumErrorsBefore;
@@ -5853,19 +5917,17 @@ clang::createVFSFromCompilerInvocation(
     const CompilerInvocation &CI, DiagnosticsEngine &Diags,
     std::shared_ptr<llvm::cas::ObjectStore> OverrideCAS) {
   return createVFSFromCompilerInvocation(
-      CI, Diags, llvm::vfs::getRealFileSystem(), std::move(OverrideCAS));
+      CI, Diags,
+      createBaseFS(CI.getFileSystemOpts(), CI.getFrontendOpts(),
+                   CI.getCASOpts(), Diags, std::move(OverrideCAS)));
 }
 
 IntrusiveRefCntPtr<llvm::vfs::FileSystem>
 clang::createVFSFromCompilerInvocation(
     const CompilerInvocation &CI, DiagnosticsEngine &Diags,
-    IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
-    std::shared_ptr<llvm::cas::ObjectStore> OverrideCAS) {
-  return createVFSFromOverlayFiles(
-      CI.getHeaderSearchOpts().VFSOverlayFiles, Diags,
-      createBaseFS(CI.getFileSystemOpts(), CI.getFrontendOpts(),
-                   CI.getCASOpts(), Diags, std::move(BaseFS),
-                   std::move(OverrideCAS)));
+    IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS) {
+  return createVFSFromOverlayFiles(CI.getHeaderSearchOpts().VFSOverlayFiles,
+                                   Diags, std::move(BaseFS));
 }
 
 IntrusiveRefCntPtr<llvm::vfs::FileSystem> clang::createVFSFromOverlayFiles(
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index ca54599b41613..269dba1745d73 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -904,8 +904,7 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
 
     std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromASTFile(
         InputFile, CI.getPCHContainerReader(), ASTUnit::LoadPreprocessorOnly,
-        CI.getVirtualFileSystemPtr(), nullptr, ASTDiags, CI.getFileSystemOpts(),
-        CI.getHeaderSearchOpts());
+        nullptr, ASTDiags, CI.getFileSystemOpts(), CI.getHeaderSearchOpts());
     if (!AST)
       return false;
 
@@ -917,9 +916,8 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
 
     // Set the shared objects, these are reset when we finish processing the
     // file, otherwise the CompilerInstance will happily destroy them.
-    CI.setVirtualFileSystem(AST->getFileManager().getVirtualFileSystemPtr());
     CI.setFileManager(&AST->getFileManager());
-    CI.createSourceManager();
+    CI.createSourceManager(CI.getFileManager());
     CI.getSourceManager().initializeForReplay(AST->getSourceManager());
 
     // Preload all the module files loaded transitively by the AST unit. Also
@@ -972,9 +970,9 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
     StringRef InputFile = Input.getFile();
 
     std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromASTFile(
-        InputFile, CI.getPCHContainerReader(), ASTUnit::LoadEverything,
-        CI.getVirtualFileSystemPtr(), nullptr, Diags, CI.getFileSystemOpts(),
-        CI.getHeaderSearchOpts(), &CI.getLangOpts());
+        InputFile, CI.getPCHContainerReader(), ASTUnit::LoadEverything, nullptr,
+        Diags, CI.getFileSystemOpts(), CI.getHeaderSearchOpts(),
+        &CI.getLangOpts());
 
     if (!AST)
       return false;
@@ -985,7 +983,6 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
 
     // Set the shared objects, these are reset when we finish processing the
     // file, otherwise the CompilerInstance will happily destroy them.
-    CI.setVirtualFileSystem(AST->getFileManager().getVirtualFileSystemPtr());
     CI.setFileManager(&AST->getFileManager());
     CI.setSourceManager(&AST->getSourceManager());
     CI.setPreprocessor(AST->getPreprocessorPtr());
@@ -1009,13 +1006,14 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
     return true;
   }
 
-  // Set up the file system, file and source managers, if needed.
-  if (!CI.hasVirtualFileSystem())
-    CI.createVirtualFileSystem();
-  if (!CI.hasFileManager())
-    CI.createFileManager();
+  // Set up the file and source managers, if needed.
+  if (!CI.hasFileManager()) {
+    if (!CI.createFileManager()) {
+      return false;
+    }
+  }
   if (!CI.hasSourceManager()) {
-    CI.createSourceManager();
+    CI.createSourceManager(CI.getFileManager());
     if (CI.getDiagnosticOpts().getFormat() == DiagnosticOptions::SARIF) {
       static_cast<SARIFDiagnosticPrinter *>(&CI.getDiagnosticClient())
           ->setSarifWriter(
diff --git a/clang/lib/Frontend/ModuleDependencyCollector.cpp b/clang/lib/Frontend/ModuleDependencyCollector.cpp
index ff37065885289..3b363f948a3a8 100644
--- a/clang/lib/Frontend/ModuleDependencyCollector.cpp
+++ b/clang/lib/Frontend/ModuleDependencyCollector.cpp
@@ -91,10 +91,10 @@ void ModuleDependencyCollector::attachToPreprocessor(Preprocessor &PP) {
       std::make_unique<ModuleDependencyMMCallbacks>(*this));
 }
 
-static bool isCaseSensitivePath(llvm::vfs::FileSystem &VFS, StringRef Path) {
+static bool isCaseSensitivePath(StringRef Path) {
   SmallString<256> TmpDest = Path, UpperDest, RealDest;
   // Remove component traversals, links, etc.
-  if (VFS.getRealPath(Path, TmpDest))
+  if (llvm::sys::fs::real_path(Path, TmpDest))
     return true; // Current default value in vfs.yaml
   Path = TmpDest;
 
@@ -104,7 +104,7 @@ static bool isCaseSensitivePath(llvm::vfs::FileSystem &VFS, StringRef Path) {
   // already expects when sensitivity isn't setup.
   for (auto &C : Path)
     UpperDest.push_back(toUppercase(C));
-  if (!VFS.getRealPath(UpperDest, RealDest) && Path == RealDest)
+  if (!llvm::sys::fs::real_path(UpperDest, RealDest) && Path == RealDest)
     return false;
   return true;
 }
@@ -121,8 +121,7 @@ void ModuleDependencyCollector::writeFileMap() {
 
   // Explicitly set case sensitivity for the YAML writer. For that, find out
   // the sensitivity at the path where the headers all collected to.
-  VFSWriter.setCaseSensitivity(
-      isCaseSensitivePath(Canonicalizer.getFileSystem(), VFSDir));
+  VFSWriter.setCaseSensitivity(isCaseSensitivePath(VFSDir));
 
   // Do not rely on real path names when executing the crash reproducer scripts
   // since we only want to actually use the files we have on the VFS cache.
@@ -154,7 +153,7 @@ std::error_code ModuleDependencyCollector::copyToRoot(StringRef Src,
   } else {
     // When collecting entries from input vfsoverlays, copy the external
     // contents into the cache but still map from the source.
-    if (!Canonicalizer.getFileSystem().exists(Dst))
+    if (!fs::exists(Dst))
       return std::error_code();
     path::append(CacheDst, Dst);
     Paths.CopyFrom = Dst;
diff --git a/clang/lib/Frontend/PrecompiledPreamble.cpp b/clang/lib/Frontend/PrecompiledPreamble.cpp
index efa6d11a6f1d2..3f3fe3c9937e4 100644
--- a/clang/lib/Frontend/PrecompiledPreamble.cpp
+++ b/clang/lib/Frontend/PrecompiledPreamble.cpp
@@ -479,10 +479,11 @@ llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
   Diagnostics.Reset();
   ProcessWarningOptions(Diagnostics, Clang->getDiagnosticOpts(), *VFS);
 
-  Clang->createVirtualFileSystem(VFS, Diagnostics.getClient());
+  VFS =
+      createVFSFromCompilerInvocation(Clang->getInvocation(), Diagnostics, VFS);
 
   // Create a file manager object to provide access to and cache the filesystem.
-  Clang->createFileManager();
+  Clang->setFileManager(new FileManager(Clang->getFileSystemOpts(), VFS));
 
   // Create the source manager.
   Clang->setSourceManager(
diff --git a/clang/lib/Frontend/Rewrite/FrontendActions.cpp b/clang/lib/Frontend/Rewrite/FrontendActions.cpp
index e47aa4eba4f0e..9d82af8ac7f91 100644
--- a/clang/lib/Frontend/Rewrite/FrontendActions.cpp
+++ b/clang/lib/Frontend/Rewrite/FrontendActions.cpp
@@ -250,8 +250,8 @@ class RewriteIncludesAction::RewriteImportsListener : public ASTReaderListener {
     CompilerInstance Instance(
         std::make_shared<CompilerInvocation>(CI.getInvocation()),
         CI.getPCHContainerOperations(), &CI.getModuleCache());
-    Instance.setVirtualFileSystem(CI.getVirtualFileSystemPtr());
     Instance.createDiagnostics(
+        CI.getVirtualFileSystem(),
         new ForwardingDiagnosticConsumer(CI.getDiagnosticClient()),
         /*ShouldOwnClient=*/true);
     Instance.getFrontendOpts().DisableFree = false;
diff --git a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index b17f5860a8682..a084b883e1b6a 100644
--- a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -214,8 +214,6 @@ CreateFrontendAction(CompilerInstance &CI) {
 }
 
 bool ExecuteCompilerInvocation(CompilerInstance *Clang) {
-  unsigned NumErrorsBefore = Clang->getDiagnostics().getNumErrors();
-
   // Honor -help.
   if (Clang->getFrontendOpts().ShowHelp) {
     driver::getDriverOptTable().printHelp(
@@ -260,9 +258,7 @@ bool ExecuteCompilerInvocation(CompilerInstance *Clang) {
     for (unsigned i = 0; i != NumArgs; ++i)
       Args[i + 1] = Clang->getFrontendOpts().LLVMArgs[i].c_str();
     Args[NumArgs + 1] = nullptr;
-    llvm::cl::ParseCommandLineOptions(NumArgs + 1, Args.get(), /*Overview=*/"",
-                                      /*Errs=*/nullptr,
-                                      /*VFS=*/&Clang->getVirtualFileSystem());
+    llvm::cl::ParseCommandLineOptions(NumArgs + 1, Args.get());
   }
 
 #if CLANG_ENABLE_STATIC_ANALYZER
@@ -313,12 +309,9 @@ bool ExecuteCompilerInvocation(CompilerInstance *Clang) {
   }
 #endif
 
-  // If there were errors in the above, don't do anything else.
-  // This intentionally ignores errors emitted before this function to
-  // accommodate lenient callers that decided to make progress despite errors.
-  if (Clang->getDiagnostics().getNumErrors() != NumErrorsBefore)
+  // If there were errors in processing arguments, don't do anything else.
+  if (Clang->getDiagnostics().hasErrorOccurred())
     return false;
-
   // Create and execute the frontend action.
   std::unique_ptr<FrontendAction> Act(CreateFrontendAction(*Clang));
   if (!Act)
diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
index 030a7ace92c31..ed3bae59a144c 100644
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -108,10 +108,8 @@ CreateCI(const llvm::opt::ArgStringList &Argv) {
     Clang->getHeaderSearchOpts().ResourceDir =
         CompilerInvocation::GetResourcesPath(Argv[0], nullptr);
 
-  Clang->createVirtualFileSystem();
-
   // Create the actual diagnostics engine.
-  Clang->createDiagnostics();
+  Clang->createDiagnostics(*llvm::vfs::getRealFileSystem());
   if (!Clang->hasDiagnostics())
     return llvm::createStringError(llvm::errc::not_supported,
                                    "Initialization failed. "
@@ -491,8 +489,7 @@ Interpreter::createWithCUDA(std::unique_ptr<CompilerInstance> CI,
       std::make_unique<llvm::vfs::OverlayFileSystem>(
           llvm::vfs::getRealFileSystem());
   OverlayVFS->pushOverlay(IMVFS);
-  CI->createVirtualFileSystem(OverlayVFS);
-  CI->createFileManager();
+  CI->createFileManager(OverlayVFS);
 
   llvm::Expected<std::unique_ptr<Interpreter>> InterpOrErr =
       Interpreter::create(std::move(CI));
diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index a703fbd00488c..2665580e5afce 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -672,8 +672,9 @@ OptionalFileEntryRef DirectoryLookup::DoFrameworkLookup(
     if (getDirCharacteristic() == SrcMgr::C_User) {
       SmallString<1024> SystemFrameworkMarker(FrameworkName);
       SystemFrameworkMarker += ".system_framework";
-      if (FileMgr.getOptionalFileRef(SystemFrameworkMarker))
+      if (llvm::sys::fs::exists(SystemFrameworkMarker)) {
         CacheEntry.IsUserSpecifiedSystemFramework = true;
+      }
     }
   }
 
@@ -1989,7 +1990,7 @@ std::string HeaderSearch::suggestPathToFileForDiagnostics(
 
   llvm::SmallString<32> FilePath = File;
   if (!WorkingDir.empty() && !path::is_absolute(FilePath))
-    path::make_absolute(WorkingDir, FilePath);
+    fs::make_absolute(WorkingDir, FilePath);
   // remove_dots switches to backslashes on windows as a side-effect!
   // We always want to suggest forward slashes for includes.
   // (not remove_dots(..., posix) as that misparses windows paths).
@@ -2003,7 +2004,7 @@ std::string HeaderSearch::suggestPathToFileForDiagnostics(
   // `BestPrefixLength` accordingly.
   auto CheckDir = [&](llvm::SmallString<32> Dir) -> bool {
     if (!WorkingDir.empty() && !path::is_absolute(Dir))
-      path::make_absolute(WorkingDir, Dir);
+      fs::make_absolute(WorkingDir, Dir);
     path::remove_dots(Dir, /*remove_dot_dot=*/true);
     for (auto NI = path::begin(File), NE = path::end(File),
               DI = path::begin(Dir), DE = path::end(Dir);
@@ -2094,10 +2095,3 @@ std::string HeaderSearch::suggestPathToFileForDiagnostics(
   }
   return path::convert_to_slash(Filename);
 }
-
-void clang::normalizeModuleCachePath(FileManager &FileMgr, StringRef Path,
-                                     SmallVectorImpl<char> &NormalizedPath) {
-  NormalizedPath.assign(Path.begin(), Path.end());
-  FileMgr.makeAbsolutePath(NormalizedPath);
-  llvm::sys::path::remove_dots(NormalizedPath);
-}
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index c4108dc5c8e68..ca1053a44e4d5 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -57,7 +57,6 @@
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/TargetOptions.h"
 #include "clang/Basic/Version.h"
-#include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/HeaderSearchOptions.h"
 #include "clang/Lex/MacroInfo.h"
@@ -1732,13 +1731,9 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, StringRef isysroot) {
   const HeaderSearchOptions &HSOpts =
       PP.getHeaderSearchInfo().getHeaderSearchOpts();
 
-  SmallString<256> HSOpts_ModuleCachePath;
-  normalizeModuleCachePath(PP.getFileManager(), HSOpts.ModuleCachePath,
-                           HSOpts_ModuleCachePath);
-
   AddString(HSOpts.Sysroot, Record);
   AddString(HSOpts.ResourceDir, Record);
-  AddString(HSOpts_ModuleCachePath, Record);
+  AddString(HSOpts.ModuleCachePath, Record);
   AddString(HSOpts.ModuleUserBuildPath, Record);
   Record.push_back(HSOpts.DisableModuleHash);
   Record.push_back(HSOpts.ImplicitModuleMaps);
diff --git a/clang/lib/Serialization/ModuleCache.cpp b/clang/lib/Serialization/ModuleCache.cpp
index 9850956380423..88ad8dd6495dd 100644
--- a/clang/lib/Serialization/ModuleCache.cpp
+++ b/clang/lib/Serialization/ModuleCache.cpp
@@ -16,87 +16,6 @@
 
 using namespace clang;
 
-/// Write a new timestamp file with the given path.
-static void writeTimestampFile(StringRef TimestampFile) {
-  std::error_code EC;
-  llvm::raw_fd_ostream Out(TimestampFile.str(), EC, llvm::sys::fs::OF_None);
-}
-
-void clang::maybePruneImpl(StringRef Path, time_t PruneInterval,
-                           time_t PruneAfter) {
-  if (PruneInterval <= 0 || PruneAfter <= 0)
-    return;
-
-  llvm::SmallString<128> TimestampFile(Path);
-  llvm::sys::path::append(TimestampFile, "modules.timestamp");
-
-  // Try to stat() the timestamp file.
-  llvm::sys::fs::file_status StatBuf;
-  if (std::error_code EC = llvm::sys::fs::status(TimestampFile, StatBuf)) {
-    // If the timestamp file wasn't there, create one now.
-    if (EC == std::errc::no_such_file_or_directory)
-      writeTimestampFile(TimestampFile);
-    return;
-  }
-
-  // Check whether the time stamp is older than our pruning interval.
-  // If not, do nothing.
-  time_t TimestampModTime =
-      llvm::sys::toTimeT(StatBuf.getLastModificationTime());
-  time_t CurrentTime = time(nullptr);
-  if (CurrentTime - TimestampModTime <= PruneInterval)
-    return;
-
-  // Write a new timestamp file so that nobody else attempts to prune.
-  // There is a benign race condition here, if two Clang instances happen to
-  // notice at the same time that the timestamp is out-of-date.
-  writeTimestampFile(TimestampFile);
-
-  // Walk the entire module cache, looking for unused module files and module
-  // indices.
-  std::error_code EC;
-  for (llvm::sys::fs::directory_iterator Dir(Path, EC), DirEnd;
-       Dir != DirEnd && !EC; Dir.increment(EC)) {
-    // If we don't have a directory, there's nothing to look into.
-    if (!llvm::sys::fs::is_directory(Dir->path()))
-      continue;
-
-    // Walk all the files within this directory.
-    for (llvm::sys::fs::directory_iterator File(Dir->path(), EC), FileEnd;
-         File != FileEnd && !EC; File.increment(EC)) {
-      // We only care about module and global module index files.
-      StringRef Extension = llvm::sys::path::extension(File->path());
-      if (Extension != ".pcm" && Extension != ".timestamp" &&
-          llvm::sys::path::filename(File->path()) != "modules.idx")
-        continue;
-
-      // Look at this file. If we can't stat it, there's nothing interesting
-      // there.
-      if (llvm::sys::fs::status(File->path(), StatBuf))
-        continue;
-
-      // If the file has been used recently enough, leave it there.
-      time_t FileAccessTime = llvm::sys::toTimeT(StatBuf.getLastAccessedTime());
-      if (CurrentTime - FileAccessTime <= PruneAfter)
-        continue;
-
-      // Remove the file.
-      llvm::sys::fs::remove(File->path());
-
-      // Remove the timestamp file.
-      std::string TimpestampFilename = File->path() + ".timestamp";
-      llvm::sys::fs::remove(TimpestampFilename);
-    }
-
-    // If we removed all the files in the directory, remove the directory
-    // itself.
-    if (llvm::sys::fs::directory_iterator(Dir->path(), EC) ==
-            llvm::sys::fs::directory_iterator() &&
-        !EC)
-      llvm::sys::fs::remove(Dir->path());
-  }
-}
-
 namespace {
 class CrossProcessModuleCache : public ModuleCache {
   InMemoryModuleCache InMemory;
@@ -136,11 +55,6 @@ class CrossProcessModuleCache : public ModuleCache {
     OS.clear_error(); // Avoid triggering a fatal error.
   }
 
-  void maybePrune(StringRef Path, time_t PruneInterval,
-                  time_t PruneAfter) override {
-    maybePruneImpl(Path, PruneInterval, PruneAfter);
-  }
-
   InMemoryModuleCache &getInMemoryModuleCache() override { return InMemory; }
   const InMemoryModuleCache &getInMemoryModuleCache() const override {
     return InMemory;
diff --git a/clang/lib/StaticAnalyzer/Checkers/Yaml.h b/clang/lib/StaticAnalyzer/Checkers/Yaml.h
index ec521cbfcdc8e..b2d17420686ee 100644
--- a/clang/lib/StaticAnalyzer/Checkers/Yaml.h
+++ b/clang/lib/StaticAnalyzer/Checkers/Yaml.h
@@ -14,7 +14,6 @@
 #ifndef LLVM_CLANG_LIB_STATICANALYZER_CHECKER_YAML_H
 #define LLVM_CLANG_LIB_STATICANALYZER_CHECKER_YAML_H
 
-#include "clang/Basic/SourceManager.h"
 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
 #include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/YAMLTraits.h"
@@ -32,12 +31,9 @@ std::optional<T> getConfiguration(CheckerManager &Mgr, Checker *Chk,
   if (ConfigFile.trim().empty())
     return std::nullopt;
 
-  auto &VFS = Mgr.getASTContext()
-                  .getSourceManager()
-                  .getFileManager()
-                  .getVirtualFileSystem();
+  llvm::vfs::FileSystem *FS = llvm::vfs::getRealFileSystem().get();
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Buffer =
-      VFS.getBufferForFile(ConfigFile.str());
+      FS->getBufferForFile(ConfigFile.str());
 
   if (Buffer.getError()) {
     Mgr.reportInvalidCheckerOptionValue(Chk, Option,
diff --git a/clang/lib/StaticAnalyzer/Frontend/ModelInjector.cpp b/clang/lib/StaticAnalyzer/Frontend/ModelInjector.cpp
index f2a05f835396d..5d392afcb9825 100644
--- a/clang/lib/StaticAnalyzer/Frontend/ModelInjector.cpp
+++ b/clang/lib/StaticAnalyzer/Frontend/ModelInjector.cpp
@@ -9,7 +9,6 @@
 #include "ModelInjector.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclObjC.h"
-#include "clang/Basic/DiagnosticDriver.h"
 #include "clang/Basic/LangStandard.h"
 #include "clang/Basic/Stack.h"
 #include "clang/Frontend/ASTUnit.h"
@@ -25,15 +24,7 @@
 using namespace clang;
 using namespace ento;
 
-ModelInjector::ModelInjector(CompilerInstance &CI) : CI(CI) {
-  if (CI.getAnalyzerOpts().ShouldEmitErrorsOnInvalidConfigValue &&
-      !CI.getAnalyzerOpts().ModelPath.empty()) {
-    auto S = CI.getVirtualFileSystem().status(CI.getAnalyzerOpts().ModelPath);
-    if (!S || S->getType() != llvm::sys::fs::file_type::directory_file)
-      CI.getDiagnostics().Report(diag::err_analyzer_config_invalid_input)
-          << "model-path" << "a filename";
-  }
-}
+ModelInjector::ModelInjector(CompilerInstance &CI) : CI(CI) {}
 
 Stmt *ModelInjector::getBody(const FunctionDecl *D) {
   onBodySynthesis(D);
@@ -65,7 +56,7 @@ void ModelInjector::onBodySynthesis(const NamedDecl *D) {
   else
     fileName = llvm::StringRef(D->getName().str() + ".model");
 
-  if (!CI.getVirtualFileSystem().exists(fileName)) {
+  if (!llvm::sys::fs::exists(fileName.str())) {
     Bodies[D->getName()] = nullptr;
     return;
   }
@@ -84,8 +75,8 @@ void ModelInjector::onBodySynthesis(const NamedDecl *D) {
   // behavior for models
   CompilerInstance Instance(std::move(Invocation),
                             CI.getPCHContainerOperations());
-  Instance.setVirtualFileSystem(CI.getVirtualFileSystemPtr());
   Instance.createDiagnostics(
+      CI.getVirtualFileSystem(),
       new ForwardingDiagnosticConsumer(CI.getDiagnosticClient()),
       /*ShouldOwnClient=*/true);
 
diff --git a/clang/lib/Testing/TestAST.cpp b/clang/lib/Testing/TestAST.cpp
index d3338956f3043..b59a8d55129de 100644
--- a/clang/lib/Testing/TestAST.cpp
+++ b/clang/lib/Testing/TestAST.cpp
@@ -54,14 +54,12 @@ class StoreDiagnostics : public DiagnosticConsumer {
 // Fills in the bits of a CompilerInstance that weren't initialized yet.
 // Provides "empty" ASTContext etc if we fail before parsing gets started.
 void createMissingComponents(CompilerInstance &Clang) {
-  if (!Clang.hasVirtualFileSystem())
-    Clang.createVirtualFileSystem();
   if (!Clang.hasDiagnostics())
-    Clang.createDiagnostics();
+    Clang.createDiagnostics(*llvm::vfs::getRealFileSystem());
   if (!Clang.hasFileManager())
     Clang.createFileManager();
   if (!Clang.hasSourceManager())
-    Clang.createSourceManager();
+    Clang.createSourceManager(Clang.getFileManager());
   if (!Clang.hasTarget())
     Clang.createTarget();
   if (!Clang.hasPreprocessor())
@@ -100,9 +98,7 @@ TestAST::TestAST(const TestInputs &In) {
 
   // Extra error conditions are reported through diagnostics, set that up first.
   bool ErrorOK = In.ErrorOK || llvm::StringRef(In.Code).contains("error-ok");
-  auto DiagConsumer = new StoreDiagnostics(Diagnostics, !ErrorOK);
-  Clang->createVirtualFileSystem(std::move(VFS), DiagConsumer);
-  Clang->createDiagnostics(DiagConsumer);
+  Clang->createDiagnostics(*VFS, new StoreDiagnostics(Diagnostics, !ErrorOK));
 
   // Parse cc1 argv, (typically [-std=c++20 input.cc]) into CompilerInvocation.
   std::vector<const char *> Argv;
@@ -119,7 +115,7 @@ TestAST::TestAST(const TestInputs &In) {
   }
   assert(!Clang->getInvocation().getFrontendOpts().DisableFree);
 
-  Clang->createFileManager();
+  Clang->createFileManager(VFS);
 
   // Running the FrontendAction creates the other components: SourceManager,
   // Preprocessor, ASTContext, Sema. Preprocessor needs TargetInfo to be set.
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
index 487d43dc4ec52..0420a83191922 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -28,6 +28,7 @@
 #include "clang/Tooling/DependencyScanning/InProcessModuleCache.h"
 #include "clang/Tooling/DependencyScanning/ModuleDepCollector.h"
 #include "clang/Tooling/DependencyScanning/ScanAndUpdateArgs.h"
+#include "clang/Tooling/Tooling.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/CAS/CASProvidingFileSystem.h"
 #include "llvm/CAS/CachingOnDiskFileSystem.h"
@@ -61,7 +62,7 @@ class DependencyConsumerForwarder : public DependencyFileGenerator {
     for (const auto &File : getDependencies()) {
       CanonPath = File;
       llvm::sys::path::remove_dots(CanonPath, /*remove_dot_dot=*/true);
-      llvm::sys::path::make_absolute(WorkingDirectory, CanonPath);
+      llvm::sys::fs::make_absolute(WorkingDirectory, CanonPath);
       C.handleFileDependency(CanonPath);
     }
     if (EmitDependencyFile)
@@ -505,7 +506,7 @@ class CASDependencyDirectivesGetter : public DependencyDirectivesGetter {
 
 /// A clang tool that runs the preprocessor in a mode that's optimized for
 /// dependency scanning for the given compiler invocation.
-class DependencyScanningAction {
+class DependencyScanningAction : public tooling::ToolAction {
 public:
   DependencyScanningAction(
       DependencyScanningService &Service, StringRef WorkingDirectory,
@@ -513,23 +514,26 @@ class DependencyScanningAction {
       llvm::IntrusiveRefCntPtr<DependencyScanningWorkerFilesystem> DepFS,
       llvm::IntrusiveRefCntPtr<DependencyScanningCASFilesystem> DepCASFS,
       llvm::IntrusiveRefCntPtr<llvm::cas::CachingOnDiskFileSystem> CacheFS,
-      bool EmitDependencyFile,
+      bool DisableFree, bool EmitDependencyFile,
       bool DiagGenerationAsCompilation, const CASOptions &CASOpts,
       std::optional<StringRef> ModuleName = std::nullopt,
       raw_ostream *VerboseOS = nullptr)
       : Service(Service), WorkingDirectory(WorkingDirectory), Consumer(Consumer),
         Controller(Controller), DepFS(std::move(DepFS)),
         DepCASFS(std::move(DepCASFS)), CacheFS(std::move(CacheFS)),
+        DisableFree(DisableFree),
         CASOpts(CASOpts), EmitDependencyFile(EmitDependencyFile),
         DiagGenerationAsCompilation(DiagGenerationAsCompilation),
         ModuleName(ModuleName), VerboseOS(VerboseOS) {}
 
   bool runInvocation(std::shared_ptr<CompilerInvocation> Invocation,
-                     IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
+                     FileManager *DriverFileMgr,
                      std::shared_ptr<PCHContainerOperations> PCHContainerOps,
-                     DiagnosticConsumer *DiagConsumer) {
+                     DiagnosticConsumer *DiagConsumer) override {
     // Make a deep copy of the original Clang invocation.
     CompilerInvocation OriginalInvocation(*Invocation);
+    // Restore the value of DisableFree, which may be modified by Tooling.
+    OriginalInvocation.getFrontendOpts().DisableFree = DisableFree;
     if (any(Service.getOptimizeArgs() & ScanningOptimizations::Macros))
       canonicalizeDefines(OriginalInvocation.getPreprocessorOpts());
 
@@ -566,13 +570,12 @@ class DependencyScanningAction {
     ScanInstance.getInvocation().getCASOpts() = CASOpts;
     ScanInstance.setBuildingModule(false);
 
-    ScanInstance.createVirtualFileSystem(FS, DiagConsumer);
-
     // Create the compiler's actual diagnostics engine.
     if (!DiagGenerationAsCompilation)
       sanitizeDiagOpts(ScanInstance.getDiagnosticOpts());
     assert(!DiagConsumerFinished && "attempt to reuse finished consumer");
-    ScanInstance.createDiagnostics(DiagConsumer, /*ShouldOwnClient=*/false);
+    ScanInstance.createDiagnostics(DriverFileMgr->getVirtualFileSystem(),
+                                   DiagConsumer, /*ShouldOwnClient=*/false);
     if (!ScanInstance.hasDiagnostics())
       return false;
     if (VerboseOS)
@@ -585,7 +588,6 @@ class DependencyScanningAction {
       ScanInstance.getHeaderSearchOpts().BuildSessionTimestamp =
           Service.getBuildSessionTimestamp();
 
-    ScanInstance.getFrontendOpts().DisableFree = false;
     ScanInstance.getFrontendOpts().GenerateGlobalModuleIndex = false;
     ScanInstance.getFrontendOpts().UseGlobalModuleIndex = false;
     // This will prevent us compiling individual modules asynchronously since
@@ -597,24 +599,25 @@ class DependencyScanningAction {
     ScanInstance.getHeaderSearchOpts().ModulesIncludeVFSUsage =
         any(Service.getOptimizeArgs() & ScanningOptimizations::VFS);
 
+    // Support for virtual file system overlays.
+    auto FS = createVFSFromCompilerInvocation(
+        ScanInstance.getInvocation(), ScanInstance.getDiagnostics(),
+        DriverFileMgr->getVirtualFileSystemPtr());
+
     // Create a new FileManager to match the invocation's FileSystemOptions.
-    ScanInstance.createFileManager();
+    auto *FileMgr = ScanInstance.createFileManager(FS);
 
     // Use the dependency scanning optimized file system if requested to do so.
     if (DepFS) {
+      StringRef ModulesCachePath =
+          ScanInstance.getHeaderSearchOpts().ModuleCachePath;
+
       DepFS->resetBypassedPathPrefix();
-      if (!ScanInstance.getHeaderSearchOpts().ModuleCachePath.empty()) {
-        SmallString<256> ModulesCachePath;
-        normalizeModuleCachePath(
-            ScanInstance.getFileManager(),
-            ScanInstance.getHeaderSearchOpts().ModuleCachePath,
-            ModulesCachePath);
+      if (!ModulesCachePath.empty())
         DepFS->setBypassedPathPrefix(ModulesCachePath);
-      }
 
       ScanInstance.setDependencyDirectivesGetter(
-          std::make_unique<ScanningDependencyDirectivesGetter>(
-              ScanInstance.getFileManager()));
+          std::make_unique<ScanningDependencyDirectivesGetter>(*FileMgr));
     }
 
     // CAS Implementation.
@@ -622,7 +625,7 @@ class DependencyScanningAction {
       ScanInstance.setDependencyDirectivesGetter(
           std::make_unique<CASDependencyDirectivesGetter>(DepCASFS.get()));
 
-    ScanInstance.createSourceManager();
+    ScanInstance.createSourceManager(*FileMgr);
 
     // Create a collection of stable directories derived from the ScanInstance
     // for determining whether module dependencies would fully resolve from
@@ -773,6 +776,9 @@ class DependencyScanningAction {
     LastCC1Arguments = OriginalInvocation.getCC1CommandLine();
     LastCC1CacheKey = Controller.getCacheKey(OriginalInvocation);
 
+    // Propagate the statistics to the parent FileManager.
+    DriverFileMgr->AddStats(ScanInstance.getFileManager());
+
     return true;
   }
 
@@ -813,6 +819,7 @@ class DependencyScanningAction {
   llvm::IntrusiveRefCntPtr<DependencyScanningWorkerFilesystem> DepFS;
   llvm::IntrusiveRefCntPtr<DependencyScanningCASFilesystem> DepCASFS;
   llvm::IntrusiveRefCntPtr<llvm::cas::CachingOnDiskFileSystem> CacheFS;
+  bool DisableFree;
   const CASOptions &CASOpts;
   bool EmitDependencyFile = false;
   bool DiagGenerationAsCompilation;
@@ -915,14 +922,15 @@ llvm::Error DependencyScanningWorker::computeDependencies(
 }
 
 static bool forEachDriverJob(
-    ArrayRef<std::string> ArgStrs, DiagnosticsEngine &Diags,
-    IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
+    ArrayRef<std::string> ArgStrs, DiagnosticsEngine &Diags, FileManager &FM,
     llvm::function_ref<bool(const driver::Command &Cmd)> Callback) {
   SmallVector<const char *, 256> Argv;
   Argv.reserve(ArgStrs.size());
   for (const std::string &Arg : ArgStrs)
     Argv.push_back(Arg.c_str());
 
+  llvm::vfs::FileSystem *FS = &FM.getVirtualFileSystem();
+
   std::unique_ptr<driver::Driver> Driver = std::make_unique<driver::Driver>(
       Argv[0], llvm::sys::getDefaultTargetTriple(), Diags,
       "clang LLVM compiler", FS);
@@ -932,8 +940,7 @@ static bool forEachDriverJob(
   bool CLMode = driver::IsClangCL(
       driver::getDriverMode(Argv[0], ArrayRef(Argv).slice(1)));
 
-  if (llvm::Error E =
-          driver::expandResponseFiles(Argv, CLMode, Alloc, FS.get())) {
+  if (llvm::Error E = driver::expandResponseFiles(Argv, CLMode, Alloc, FS)) {
     Diags.Report(diag::err_drv_expand_response_file)
         << llvm::toString(std::move(E));
     return false;
@@ -956,25 +963,17 @@ static bool forEachDriverJob(
 
 static bool createAndRunToolInvocation(
     std::vector<std::string> CommandLine, DependencyScanningAction &Action,
-    IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
+    FileManager &FM,
     std::shared_ptr<clang::PCHContainerOperations> &PCHContainerOps,
     DiagnosticsEngine &Diags, DependencyConsumer &Consumer) {
 
   // Save executable path before providing CommandLine to ToolInvocation
   std::string Executable = CommandLine[0];
-
-  llvm::opt::ArgStringList Argv;
-  for (const std::string &Str : ArrayRef(CommandLine).drop_front())
-    Argv.push_back(Str.c_str());
-
-  auto Invocation = std::make_shared<CompilerInvocation>();
-  if (!CompilerInvocation::CreateFromArgs(*Invocation, Argv, Diags)) {
-    // FIXME: Should we just go on like cc1_main does?
-    return false;
-  }
-
-  if (!Action.runInvocation(std::move(Invocation), std::move(FS),
-                            PCHContainerOps, Diags.getClient()))
+  ToolInvocation Invocation(std::move(CommandLine), &Action, &FM,
+                            PCHContainerOps);
+  Invocation.setDiagnosticConsumer(Diags.getClient());
+  Invocation.setDiagnosticOptions(&Diags.getDiagnosticOptions());
+  if (!Invocation.run())
     return false;
 
   std::vector<std::string> Args = Action.takeLastCC1Arguments();
@@ -989,26 +988,40 @@ bool DependencyScanningWorker::scanDependencies(
     DependencyConsumer &Consumer, DependencyActionController &Controller,
     DiagnosticConsumer &DC, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
     std::optional<StringRef> ModuleName) {
+  auto FileMgr =
+      llvm::makeIntrusiveRefCnt<FileManager>(FileSystemOptions{}, FS);
+
   std::vector<const char *> CCommandLine(CommandLine.size(), nullptr);
   llvm::transform(CommandLine, CCommandLine.begin(),
                   [](const std::string &Str) { return Str.c_str(); });
   auto DiagOpts = CreateAndPopulateDiagOpts(CCommandLine);
   sanitizeDiagOpts(*DiagOpts);
-  auto Diags = CompilerInstance::createDiagnostics(*FS, *DiagOpts, &DC,
-                                                   /*ShouldOwnClient=*/false);
-
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
+      CompilerInstance::createDiagnostics(FileMgr->getVirtualFileSystem(),
+                                          *DiagOpts, &DC,
+                                          /*ShouldOwnClient=*/false);
+
+  // Although `Diagnostics` are used only for command-line parsing, the
+  // custom `DiagConsumer` might expect a `SourceManager` to be present.
+  SourceManager SrcMgr(*Diags, *FileMgr);
+  Diags->setSourceManager(&SrcMgr);
+  // DisableFree is modified by Tooling for running
+  // in-process; preserve the original value, which is
+  // always true for a driver invocation.
+  bool DisableFree = true;
   DependencyScanningAction Action(Service, WorkingDirectory, Consumer, Controller, DepFS,
                                   DepCASFS, CacheFS,
+                                  DisableFree,
                                   /*EmitDependencyFile=*/false,
                                   /*DiagGenerationAsCompilation=*/false, getCASOpts(),
                                   ModuleName);
   bool Success = false;
   if (CommandLine[1] == "-cc1") {
-    Success = createAndRunToolInvocation(CommandLine, Action, FS,
+    Success = createAndRunToolInvocation(CommandLine, Action, *FileMgr,
                                          PCHContainerOps, *Diags, Consumer);
   } else {
     Success = forEachDriverJob(
-        CommandLine, *Diags, FS, [&](const driver::Command &Cmd) {
+        CommandLine, *Diags, *FileMgr, [&](const driver::Command &Cmd) {
           if (StringRef(Cmd.getCreator().getName()) != "clang") {
             // Non-clang command. Just pass through to the dependency
             // consumer.
@@ -1028,7 +1041,7 @@ bool DependencyScanningWorker::scanDependencies(
           // system to ensure that any file system requests that
           // are made by the driver do not go through the
           // dependency scanning filesystem.
-          return createAndRunToolInvocation(std::move(Argv), Action, FS,
+          return createAndRunToolInvocation(std::move(Argv), Action, *FileMgr,
                                             PCHContainerOps, *Diags, Consumer);
         });
   }
@@ -1150,7 +1163,7 @@ void DependencyScanningWorker::computeDependenciesFromCompilerInvocation(
     // FIXME: On Windows, WorkingDirectory is insufficient for making an
     // absolute path if OutputFile has a root name.
     llvm::SmallString<128> Path = StringRef(DepFile);
-    llvm::sys::path::make_absolute(WorkingDirectory, Path);
+    llvm::sys::fs::make_absolute(WorkingDirectory, Path);
     DepFile = Path.str().str();
   }
 
@@ -1158,6 +1171,7 @@ void DependencyScanningWorker::computeDependenciesFromCompilerInvocation(
   // compilation.
   DependencyScanningAction Action(Service, WorkingDirectory, DepsConsumer,
                                   Controller, DepFS, DepCASFS, CacheFS,
+                                  /*DisableFree=*/false,
                                   /*EmitDependencyFile=*/!DepFile.empty(),
                                   DiagGenerationAsCompilation, getCASOpts(),
                                   /*ModuleName=*/std::nullopt, VerboseOS);
@@ -1165,6 +1179,8 @@ void DependencyScanningWorker::computeDependenciesFromCompilerInvocation(
   // Ignore result; we're just collecting dependencies.
   //
   // FIXME: will clients other than -cc1scand care?
-  (void)Action.runInvocation(std::move(Invocation), BaseFS,
+  IntrusiveRefCntPtr<FileManager> ActiveFiles =
+      new FileManager(Invocation->getFileSystemOpts(), BaseFS);
+  (void)Action.runInvocation(std::move(Invocation), ActiveFiles.get(),
                              PCHContainerOps, &DiagsConsumer);
 }
diff --git a/clang/lib/Tooling/DependencyScanning/InProcessModuleCache.cpp b/clang/lib/Tooling/DependencyScanning/InProcessModuleCache.cpp
index d1e543b438225..80db2d47d940e 100644
--- a/clang/lib/Tooling/DependencyScanning/InProcessModuleCache.cpp
+++ b/clang/lib/Tooling/DependencyScanning/InProcessModuleCache.cpp
@@ -100,13 +100,6 @@ class InProcessModuleCache : public ModuleCache {
     Timestamp.store(llvm::sys::toTimeT(std::chrono::system_clock::now()));
   }
 
-  void maybePrune(StringRef Path, time_t PruneInterval,
-                  time_t PruneAfter) override {
-    // FIXME: This only needs to be ran once per build, not in every
-    // compilation. Call it once per service.
-    maybePruneImpl(Path, PruneInterval, PruneAfter);
-  }
-
   InMemoryModuleCache &getInMemoryModuleCache() override { return InMemory; }
   const InMemoryModuleCache &getInMemoryModuleCache() const override {
     return InMemory;
diff --git a/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp b/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp
index da1855ed4dd87..90ea9bef9afaa 100644
--- a/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp
+++ b/clang/lib/Tooling/DependencyScanning/IncludeTreeActionController.cpp
@@ -282,11 +282,10 @@ void dependencies::addReversePrefixMappingFileSystem(
   llvm::PrefixMapper ReverseMapper;
   ReverseMapper.addInverseRange(PrefixMapper.getMappings());
   ReverseMapper.sort();
-  IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS =
+  std::unique_ptr<llvm::vfs::FileSystem> FS =
       llvm::vfs::createPrefixMappingFileSystem(
           std::move(ReverseMapper), &ScanInstance.getVirtualFileSystem());
 
-  ScanInstance.setVirtualFileSystem(FS);
   ScanInstance.getFileManager().setVirtualFileSystem(std::move(FS));
 }
 
diff --git a/clang/lib/Tooling/Tooling.cpp b/clang/lib/Tooling/Tooling.cpp
index af4a0a25127a0..53339566e310e 100644
--- a/clang/lib/Tooling/Tooling.cpp
+++ b/clang/lib/Tooling/Tooling.cpp
@@ -453,11 +453,12 @@ bool FrontendActionFactory::runInvocation(
   std::unique_ptr<FrontendAction> ScopedToolAction(create());
 
   // Create the compiler's actual diagnostics engine.
-  Compiler.createDiagnostics(DiagConsumer, /*ShouldOwnClient=*/false);
+  Compiler.createDiagnostics(Files->getVirtualFileSystem(), DiagConsumer,
+                             /*ShouldOwnClient=*/false);
   if (!Compiler.hasDiagnostics())
     return false;
 
-  Compiler.createSourceManager();
+  Compiler.createSourceManager(*Files);
 
   const bool Success = Compiler.ExecuteAction(*ScopedToolAction);
 
diff --git a/clang/test/Analysis/Inputs/taint-generic-config-vfs.json b/clang/test/Analysis/Inputs/taint-generic-config-vfs.json
deleted file mode 100644
index 74f3cd99a9707..0000000000000
--- a/clang/test/Analysis/Inputs/taint-generic-config-vfs.json
+++ /dev/null
@@ -1,17 +0,0 @@
-{
-  'version': 0,
-  'use-external-names': true,
-  'roots': [
-    {
-      'name': 'DIR',
-      'type': 'directory',
-      'contents': [
-        {
-          'name': 'taint-generic-config-virtual.yaml',
-          'type': 'file',
-          'external-contents': 'DIR/taint-generic-config.yaml'
-        }
-      ]
-    }
-  ]
-}
diff --git a/clang/test/Analysis/model-file-missing.cpp b/clang/test/Analysis/model-file-missing.cpp
deleted file mode 100644
index c9dfb4ec1b244..0000000000000
--- a/clang/test/Analysis/model-file-missing.cpp
+++ /dev/null
@@ -1,3 +0,0 @@
-// RUN: not %clang_analyze_cc1 -analyzer-checker=core -analyzer-config model-path=%t/blah %s -o - 2>&1 | FileCheck %s
-// CHECK: error: invalid input for analyzer-config option 'model-path', that expects a filename value
-// CHECK-NEXT: 1 error generated
diff --git a/clang/test/Analysis/taint-generic.c b/clang/test/Analysis/taint-generic.c
index 6017483f06b6d..9d6d2942df4a9 100644
--- a/clang/test/Analysis/taint-generic.c
+++ b/clang/test/Analysis/taint-generic.c
@@ -1,6 +1,3 @@
-// RUN: rm -rf %t && mkdir %t
-// RUN: sed -e "s|DIR|%/S/Inputs|g" %S/Inputs/taint-generic-config-vfs.json > %t/taint-generic-config-vfs.json
-
 // RUN: %clang_analyze_cc1 -Wno-format-security -Wno-pointer-to-int-cast \
 // RUN:   -Wno-incompatible-library-redeclaration -verify %s \
 // RUN:   -analyzer-checker=optin.taint.GenericTaint \
@@ -9,8 +6,7 @@
 // RUN:   -analyzer-checker=security.ArrayBound \
 // RUN:   -analyzer-checker=debug.ExprInspection \
 // RUN:   -analyzer-config \
-// RUN:     optin.taint.TaintPropagation:Config=%S/Inputs/taint-generic-config-virtual.yaml \
-// RUN:   -ivfsoverlay %t/taint-generic-config-vfs.json
+// RUN:     optin.taint.TaintPropagation:Config=%S/Inputs/taint-generic-config.yaml
 
 // RUN: %clang_analyze_cc1 -Wno-format-security -Wno-pointer-to-int-cast \
 // RUN:   -Wno-incompatible-library-redeclaration -verify %s \
diff --git a/clang/test/CAS/output-path-error.c b/clang/test/CAS/output-path-error.c
index a221f3bb29bf0..b217ba48402cf 100644
--- a/clang/test/CAS/output-path-error.c
+++ b/clang/test/CAS/output-path-error.c
@@ -19,4 +19,4 @@
 // RUN: cat %t/output.txt | FileCheck %s --check-prefix=ERROR
 
 // CACHE-MISS: remark: compile job cache miss
-// ERROR: fatal error: CAS filesystem cannot be initialized from root-id 'llvmcas://{{.*}}': cannot get reference to root FS
+// ERROR: fatal error: CAS missing expected root-id
diff --git a/clang/test/CAS/pgo-profile-with-pch.c b/clang/test/CAS/pgo-profile-with-pch.c
index e1d40f29665db..03ed10cc46047 100644
--- a/clang/test/CAS/pgo-profile-with-pch.c
+++ b/clang/test/CAS/pgo-profile-with-pch.c
@@ -4,7 +4,7 @@
 
 // RUN: llvm-profdata merge -o %t.profdata %S/Inputs/pgo.profraw
 // RUN: %clang -cc1depscan -fdepscan=inline -fdepscan-include-tree -o %t-pch.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-pch -O3 -Rcompile-job-cache \
-// RUN:   -x c-header %s -o %t.h.pch -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata
+// RUN:   -x c-header %s -o %t.h.pch -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.profdata
 // RUN: %clang @%t-pch.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-MISS
 // RUN: FileCheck %s -check-prefix=PCHPROF -input-file %t-pch.rsp
 // PCHPROF-NOT: -fprofile-instrument-use-path
@@ -14,14 +14,14 @@
 
 // Use the modified profdata file for the main file along with the PCH.
 // RUN: %clang -cc1depscan -fdepscan=inline -fdepscan-include-tree -o %t.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -include-pch %t.h.pch
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.profdata -include-pch %t.h.pch
 // RUN: %clang @%t.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-MISS
 // RUN: FileCheck %s -check-prefix=TUPROF -input-file %t.rsp
 // TUPROF: -fprofile-instrument-use-path
 
 // Check that the modified profdata is ignored when re-scanning for the PCH.
 // RUN: %clang -cc1depscan -fdepscan=inline -fdepscan-include-tree -o %t-pch2.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-pch -O3 -Rcompile-job-cache \
-// RUN:   -x c-header %s -o %t.h.pch -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata
+// RUN:   -x c-header %s -o %t.h.pch -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.profdata
 // RUN: diff -u %t-pch.rsp %t-pch2.rsp
 
 // CACHE-MISS: remark: compile job cache miss
diff --git a/clang/test/CAS/pgo-profile.c b/clang/test/CAS/pgo-profile.c
index a474754d69726..cf0f024f2aae0 100644
--- a/clang/test/CAS/pgo-profile.c
+++ b/clang/test/CAS/pgo-profile.c
@@ -3,7 +3,7 @@
 /// Check use pgo profile.
 // RUN: llvm-profdata merge -o %t.profdata %S/Inputs/pgo.profraw
 // RUN: %clang -cc1depscan -fdepscan=inline -o %t.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.profdata
 
 /// Remove profile data to make sure the cc1 command is not reading from file system.
 // RUN: rm %t.profdata
@@ -13,7 +13,7 @@
 /// Check include tree.
 // RUN: llvm-profdata merge -o %t.profdata %S/Inputs/pgo.profraw
 // RUN: %clang -cc1depscan -fdepscan=inline -fdepscan-include-tree -o %t1.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.profdata
 // RUN: rm %t.profdata
 // RUN: %clang @%t1.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-MISS
 // RUN: %clang @%t1.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-HIT
@@ -21,12 +21,12 @@
 /// Check change profile data will cause cache miss.
 // RUN: llvm-profdata merge -o %t.profdata %S/Inputs/pgo2.profraw
 // RUN: %clang -cc1depscan -fdepscan=inline -o %t2.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.profdata
 // RUN: not diff %t.rsp %t2.rsp
 // RUN: %clang @%t2.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-MISS
 
 // RUN: %clang -cc1depscan -fdepscan=inline -fdepscan-include-tree -o %t3.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.profdata
 // RUN: not diff %t1.rsp %t3.rsp
 // RUN: %clang @%t3.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-MISS
 
@@ -38,9 +38,9 @@
 // RUN: cp %t.profdata %t.dir/a/a.profdata
 // RUN: cp %t.profdata %t.dir/b/a.profdata
 // RUN: %clang -cc1depscan -fdepscan=inline -o %t4.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache -fdepscan-prefix-map %t.dir/a /^testdir  \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.dir/a/a.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.dir/a/a.profdata
 // RUN: %clang -cc1depscan -fdepscan=inline -o %t5.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache -fdepscan-prefix-map %t.dir/b /^testdir \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.dir/b/a.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.dir/b/a.profdata
 // RUN: cat %t4.rsp | FileCheck %s --check-prefix=REMAP
 // RUN: %clang @%t4.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-MISS
 // RUN: %clang @%t5.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-HIT
@@ -55,9 +55,9 @@
 // RUN: diff -u %t.dir/cache-key1 %t.dir/cache-key2
 
 // RUN: %clang -cc1depscan -fdepscan=inline -fdepscan-include-tree -o %t4.inc.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache -fdepscan-prefix-map %t.dir/a /^testdir \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.dir/a/a.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.dir/a/a.profdata
 // RUN: %clang -cc1depscan -fdepscan=inline -fdepscan-include-tree -o %t5.inc.rsp -cc1-args -cc1 -triple x86_64-apple-macosx12.0.0 -emit-obj -O3 -Rcompile-job-cache -fdepscan-prefix-map %t.dir/b /^testdir \
-// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.dir/b/a.profdata
+// RUN:   -x c %s -o %t.o -fcas-path %t.dir/cas -fprofile-instrument-use-path=%t.dir/b/a.profdata
 // RUN: cat %t4.inc.rsp | FileCheck %s --check-prefix=REMAP
 // RUN: %clang @%t4.inc.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-MISS
 // RUN: %clang @%t5.inc.rsp 2>&1 | FileCheck %s --check-prefix=CACHE-HIT
diff --git a/clang/test/CodeGen/cspgo-instrumentation.c b/clang/test/CodeGen/cspgo-instrumentation.c
index f42d68aba0eaa..3f90bb4396d70 100644
--- a/clang/test/CodeGen/cspgo-instrumentation.c
+++ b/clang/test/CodeGen/cspgo-instrumentation.c
@@ -9,19 +9,19 @@
 // RUN: llvm-profdata merge -o %t/noncs.profdata %S/Inputs/pgotestir.proftext
 //
 // Ensure Pass PGOInstrumentationUsePass and PGOInstrumentationGenPass are invoked.
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t/noncs.profdata -fprofile-instrument=csllvm -fprofile-instrument-path=default.profraw  %s -fdebug-pass-manager  -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN2
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t/noncs.profdata -fprofile-instrument=csllvm -fprofile-instrument-path=default.profraw  %s -fdebug-pass-manager  -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN2
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN2: Running pass: PGOInstrumentationUse
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN2: Running pass: PGOInstrumentationGenCreateVar on
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN2: Running pass: PGOInstrumentationGen on
 
 // Ensure Pass PGOInstrumentationUsePass is invoked only once.
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t/noncs.profdata %s -fdebug-pass-manager -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-USE
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t/noncs.profdata %s -fdebug-pass-manager -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-USE
 // CHECK-PGOUSEPASS-INVOKED-USE: Running pass: PGOInstrumentationUse
 // CHECK-PGOUSEPASS-INVOKED-USE-NOT: Running pass: PGOInstrumentationGenCreateVar
 // CHECK-PGOUSEPASS-INVOKED-USE-NOT: Running pass: PGOInstrumentationUse
 //
 // Ensure Pass PGOInstrumentationUsePass is invoked twice.
 // RUN: llvm-profdata merge -o %t/cs.profdata %S/Inputs/pgotestir_cs.proftext
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=csllvm -fprofile-instrument-use-path=%t/cs.profdata %s -fdebug-pass-manager  -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-USE2
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t/cs.profdata %s -fdebug-pass-manager  -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-USE2
 // CHECK-PGOUSEPASS-INVOKED-USE2: Running pass: PGOInstrumentationUse
 // CHECK-PGOUSEPASS-INVOKED-USE2: Running pass: PGOInstrumentationUse
diff --git a/clang/test/CodeGen/cspgo-instrumentation_lto.c b/clang/test/CodeGen/cspgo-instrumentation_lto.c
index 5d541c6688a1f..c4296842ae50e 100644
--- a/clang/test/CodeGen/cspgo-instrumentation_lto.c
+++ b/clang/test/CodeGen/cspgo-instrumentation_lto.c
@@ -4,7 +4,7 @@
 // RUN: llvm-profdata merge -o %t/noncs.profdata %S/Inputs/pgotestir.proftext
 //
 // Ensure Pass PGOInstrumentationGenPass is not invoked in PreLink.
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t/noncs.profdata -fprofile-instrument=csllvm %s -flto -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t/noncs.profdata -fprofile-instrument=csllvm %s -flto -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE: Running pass: PGOInstrumentationUse
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE: Running pass: PGOInstrumentationGenCreateVar
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE-NOT: Running pass: PGOInstrumentationGen on
@@ -18,12 +18,12 @@
 // RUN: llvm-profdata merge -o %t/cs.profdata %S/Inputs/pgotestir_cs.proftext
 //
 // Ensure Pass PGOInstrumentationUsePass is invoked Once in PreLink.
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=csllvm -fprofile-instrument-use-path=%t/cs.profdata %s -flto -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t/cs.profdata %s -flto -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE: Running pass: PGOInstrumentationUse
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE-NOT: Running pass: PGOInstrumentationGenCreateVar
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE-NOT: Running pass: PGOInstrumentationUse
 //
 // Ensure Pass PGOInstrumentationUSEPass is invoked in PostLink.
-// RUN: %clang_cc1 -O2 -x ir %t/foo_fe_pm.bc -fdebug-pass-manager -fprofile-instrument-use=csllvm -fprofile-instrument-use-path=%t/cs.profdata -flto -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST
+// RUN: %clang_cc1 -O2 -x ir %t/foo_fe_pm.bc -fdebug-pass-manager -fprofile-instrument-use-path=%t/cs.profdata -flto -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST: Running pass: PGOInstrumentationUse
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST-NOT: Running pass: PGOInstrumentationUse
diff --git a/clang/test/CodeGen/cspgo-instrumentation_thinlto.c b/clang/test/CodeGen/cspgo-instrumentation_thinlto.c
index 0627f64a69728..f79433827ce17 100644
--- a/clang/test/CodeGen/cspgo-instrumentation_thinlto.c
+++ b/clang/test/CodeGen/cspgo-instrumentation_thinlto.c
@@ -4,7 +4,7 @@
 // RUN: llvm-profdata merge -o %t/noncs.profdata %S/Inputs/pgotestir.proftext
 //
 // Ensure Pass PGOInstrumentationGenPass is not invoked in PreLink.
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t/noncs.profdata -fprofile-instrument=csllvm %s -fprofile-instrument-path=default.profraw  -flto=thin -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t/noncs.profdata -fprofile-instrument=csllvm %s -fprofile-instrument-path=default.profraw  -flto=thin -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE: Running pass: PGOInstrumentationUse
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE: Running pass: PGOInstrumentationGenCreateVar
 // CHECK-CSPGOGENPASS-INVOKED-INSTR-GEN-PRE-NOT: Running pass: PGOInstrumentationGen on
@@ -19,16 +19,16 @@
 // RUN: llvm-profdata merge -o %t/cs.profdata %S/Inputs/pgotestir_cs.proftext
 //
 // Ensure Pass PGOInstrumentationUsePass is invoked Once in PreLink.
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=csllvm -fprofile-instrument-use-path=%t/cs.profdata %s -flto=thin -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t/cs.profdata %s -flto=thin -fdebug-pass-manager -emit-llvm-bc -o %t/foo_fe_pm.bc 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE: Running pass: PGOInstrumentationUse
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-PRE-NOT: Running pass: PGOInstrumentationUse
 //
 // RUN: llvm-lto -thinlto -o %t/foo_pm %t/foo_fe_pm.bc
 // Ensure Pass PGOInstrumentationUSEPass is invoked in PostLink.
-// RUN: %clang_cc1 -O2 -x ir %t/foo_fe_pm.bc -fthinlto-index=%t/foo_pm.thinlto.bc -fdebug-pass-manager -fprofile-instrument-use=csllvm -fprofile-instrument-use-path=%t/cs.profdata -flto=thin -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST
+// RUN: %clang_cc1 -O2 -x ir %t/foo_fe_pm.bc -fthinlto-index=%t/foo_pm.thinlto.bc -fdebug-pass-manager -fprofile-instrument-use-path=%t/cs.profdata -flto=thin -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST: Running pass: PGOInstrumentationUse
 // CHECK-CSPGOUSEPASS-INVOKED-INSTR-USE-POST-NOT: Running pass: PGOInstrumentationUse
 //
 // Finally, test if a non-cs profile is passed to PostLink passes, PGO UsePass is not invoked.
-// RUN: %clang_cc1 -O2 -x ir %t/foo_fe_pm.bc -fthinlto-index=%t/foo_pm.thinlto.bc -fdebug-pass-manager -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t/noncs.profdata -flto=thin -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-INSTR-USE-POST
+// RUN: %clang_cc1 -O2 -x ir %t/foo_fe_pm.bc -fthinlto-index=%t/foo_pm.thinlto.bc -fdebug-pass-manager -fprofile-instrument-use-path=%t/noncs.profdata -flto=thin -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-INSTR-USE-POST
 // CHECK-PGOUSEPASS-INVOKED-INSTR-USE-POST-NOT: Running pass: PGOInstrumentationUse
diff --git a/clang/test/CodeGen/opt-record.c b/clang/test/CodeGen/opt-record.c
index f54a6225760aa..391c14b7bbcc2 100644
--- a/clang/test/CodeGen/opt-record.c
+++ b/clang/test/CodeGen/opt-record.c
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -O3 -triple x86_64-unknown-linux-gnu -target-cpu x86-64 %s -o %t -opt-record-file %t.yaml -emit-obj
 // RUN: cat %t.yaml | FileCheck %s
 // RUN: llvm-profdata merge %S/Inputs/opt-record.proftext -o %t.profdata
-// RUN: %clang_cc1 -O3 -triple x86_64-unknown-linux-gnu -target-cpu x86-64 -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata %s -o %t -opt-record-file %t.yaml -emit-obj
+// RUN: %clang_cc1 -O3 -triple x86_64-unknown-linux-gnu -target-cpu x86-64 -fprofile-instrument-use-path=%t.profdata %s -o %t -opt-record-file %t.yaml -emit-obj
 // RUN: cat %t.yaml | FileCheck -check-prefix=CHECK -check-prefix=CHECK-PGO %s
 // RUN: %clang_cc1 -O3 -triple x86_64-unknown-linux-gnu -target-cpu x86-64 %s -o %t -opt-record-file %t.yaml -opt-record-passes inline -emit-obj
 // RUN: cat %t.yaml | FileCheck -check-prefix=CHECK-PASSES %s
diff --git a/clang/test/CodeGen/pgo-instrumentation.c b/clang/test/CodeGen/pgo-instrumentation.c
index 7c878250ae33e..c01658065497e 100644
--- a/clang/test/CodeGen/pgo-instrumentation.c
+++ b/clang/test/CodeGen/pgo-instrumentation.c
@@ -15,10 +15,10 @@
 
 // Ensure Pass PGOInstrumentationUsePass is invoked.
 // RUN: llvm-profdata merge -o %t.profdata %S/Inputs/pgotestir.profraw
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t.profdata %s -fdebug-pass-manager -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-INSTR-USE
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t.profdata %s -fdebug-pass-manager -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-INSTR-USE
 // CHECK-PGOUSEPASS-INVOKED-INSTR-USE: Running pass: PGOInstrumentationUse on
 //
 // Ensure Pass PGOInstrumentationUsePass is not invoked.
 // RUN: llvm-profdata merge -o %t.profdata %S/Inputs/pgotestclang.profraw
-// RUN: %clang_cc1 -O2 -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata %s -fdebug-pass-manager -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-USE-CLANG
+// RUN: %clang_cc1 -O2 -fprofile-instrument-use-path=%t.profdata %s -fdebug-pass-manager -emit-llvm -o - 2>&1 | FileCheck %s -check-prefix=CHECK-PGOUSEPASS-INVOKED-USE-CLANG
 // CHECK-PGOUSEPASS-INVOKED-USE-CLANG-NOT: Running pass: PGOInstrumentationUse on
diff --git a/clang/test/CodeGen/thinlto-clang-diagnostic-handler-in-be.c b/clang/test/CodeGen/thinlto-clang-diagnostic-handler-in-be.c
index a12574d28c731..efbcc851ad770 100644
--- a/clang/test/CodeGen/thinlto-clang-diagnostic-handler-in-be.c
+++ b/clang/test/CodeGen/thinlto-clang-diagnostic-handler-in-be.c
@@ -7,7 +7,7 @@
 // RUN: llvm-lto -thinlto -o %t %t1.bo
 // RUN: %clang_cc1 -triple x86_64-linux-gnu -O2 -x ir %t1.bo -fthinlto-index=%t.thinlto.bc -emit-obj -Rpass-analysis=info 2>&1 | FileCheck %s -check-prefix=CHECK-REMARK
 // RUN: llvm-profdata merge -o %t2.profdata %S/Inputs/thinlto_expect2.proftext
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -O2 -x ir %t1.bo -fthinlto-index=%t.thinlto.bc -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t2.profdata -emit-obj 2>&1 | FileCheck %s -allow-empty -check-prefix=CHECK-NOWARNING
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -O2 -x ir %t1.bo -fthinlto-index=%t.thinlto.bc -fprofile-instrument-use-path=%t2.profdata -emit-obj 2>&1 | FileCheck %s -allow-empty -check-prefix=CHECK-NOWARNING
 
 int sum;
 __attribute__((noinline)) void bar(void) {
diff --git a/clang/test/CodeGenCXX/fdebug-info-for-profiling.cpp b/clang/test/CodeGenCXX/fdebug-info-for-profiling.cpp
index 63de73c90bd2f..e468a8098d7c8 100644
--- a/clang/test/CodeGenCXX/fdebug-info-for-profiling.cpp
+++ b/clang/test/CodeGenCXX/fdebug-info-for-profiling.cpp
@@ -13,7 +13,7 @@
 
 // RUN: echo > %t.proftext
 // RUN: llvm-profdata merge %t.proftext -o %t.profdata
-// RUN: %clang_cc1 -emit-llvm -fdebug-pass-manager -O1 -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -fdebug-info-for-profiling %s -o - 2>&1 | FileCheck %s --check-prefix=DISCR
+// RUN: %clang_cc1 -emit-llvm -fdebug-pass-manager -O1 -fprofile-instrument-use-path=%t.profdata -fdebug-info-for-profiling %s -o - 2>&1 | FileCheck %s --check-prefix=DISCR
 // RUN: %clang_cc1 -emit-llvm -fdebug-pass-manager -O1 -fdebug-info-for-profiling -fpseudo-probe-for-profiling %s -o - 2>&1 | FileCheck %s --check-prefix=PROBE
 
 // NODISCR-NOT: Running pass: AddDiscriminatorsPass
diff --git a/clang/test/CodeGenCXX/profile-remap.cpp b/clang/test/CodeGenCXX/profile-remap.cpp
index f077f929f406d..b27f67da58ff9 100644
--- a/clang/test/CodeGenCXX/profile-remap.cpp
+++ b/clang/test/CodeGenCXX/profile-remap.cpp
@@ -2,9 +2,9 @@
 //
 // RUN: %clang_cc1 -triple x86_64-linux-gnu -fprofile-sample-use=%S/Inputs/profile-remap.samples -fprofile-remapping-file=%S/Inputs/profile-remap.map -O2 %s -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,CHECK-SAMPLES
 // RUN: llvm-profdata merge -output %T.profdata %S/Inputs/profile-remap.proftext
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%T.profdata -fprofile-remapping-file=%S/Inputs/profile-remap.map -O2 %s -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,CHECK-INSTR
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fprofile-instrument-use-path=%T.profdata -fprofile-remapping-file=%S/Inputs/profile-remap.map -O2 %s -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,CHECK-INSTR
 // RUN: llvm-profdata merge -output %T.profdata %S/Inputs/profile-remap_entry.proftext
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%T.profdata -fprofile-remapping-file=%S/Inputs/profile-remap.map -O2 %s -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,CHECK-INSTR
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fprofile-instrument-use-path=%T.profdata -fprofile-remapping-file=%S/Inputs/profile-remap.map -O2 %s -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,CHECK-INSTR
 
 namespace Foo {
   struct X {};
diff --git a/clang/test/Driver/Inputs/a.proftext b/clang/test/Driver/Inputs/a.proftext
deleted file mode 100644
index 05ab839db07c7..0000000000000
--- a/clang/test/Driver/Inputs/a.proftext
+++ /dev/null
@@ -1,2 +0,0 @@
-# IR level Instrumentation Flag
-:ir
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 22cb04bc95530..57e16e8795a28 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -90,21 +90,16 @@
 // RUN: not %clang_cl -### /FAcsu -fprofile-instr-generate -fprofile-instr-use=file -- %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MIX-GEN-USE %s
 // CHECK-NO-MIX-GEN-USE: '{{[a-z=-]*}}' not allowed with '{{[a-z=-]*}}'
 
-// RUN: rm -rf %t && mkdir %t
-// RUN: llvm-profdata merge -o %t/somefile.prof %S/Inputs/a.proftext
-// RUN: llvm-profdata merge -o %t/default.profdata %S/Inputs/a.proftext
-// RUN: cd %t
-
 // RUN: %clang_cl -### /FA -fprofile-instr-use -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE %s
 // RUN: %clang_cl -### /FA -fprofile-use -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE %s
-// RUN: %clang_cl -### /FA -fprofile-instr-use=%t/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
-// RUN: %clang_cl -### /FA -fprofile-use=%t/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
+// RUN: %clang_cl -### /FA -fprofile-instr-use=/tmp/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
+// RUN: %clang_cl -### /FA -fprofile-use=/tmp/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
 // RUN: %clang_cl -### /FAcsu -fprofile-instr-use -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE %s
 // RUN: %clang_cl -### /FAcsu -fprofile-use -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE %s
-// RUN: %clang_cl -### /FAcsu -fprofile-instr-use=%t/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
-// RUN: %clang_cl -### /FAcsu -fprofile-use=%t/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
-// CHECK-PROFILE-USE: "-fprofile-instrument-use-path={{.*}}default.profdata"
-// CHECK-PROFILE-USE-FILE: "-fprofile-instrument-use-path={{.*}}somefile.prof"
+// RUN: %clang_cl -### /FAcsu -fprofile-instr-use=/tmp/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
+// RUN: %clang_cl -### /FAcsu -fprofile-use=/tmp/somefile.prof -- %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
+// CHECK-PROFILE-USE: "-fprofile-instrument-use-path=default.profdata"
+// CHECK-PROFILE-USE-FILE: "-fprofile-instrument-use-path=/tmp/somefile.prof"
 
 // RUN: %clang_cl /GA -### -- %s 2>&1 | FileCheck -check-prefix=GA %s
 // GA: -ftls-model=local-exec
diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
index a68e60f2a9738..ee7ded265769b 100644
--- a/clang/test/Driver/clang_f_opts.c
+++ b/clang/test/Driver/clang_f_opts.c
@@ -122,22 +122,16 @@
 // CHECK-DISABLE-COVERAGE-NOT: "-fcoverage-mapping"
 // CHECK-PROFILE-REMAP: "-fprofile-remapping-file=foo/bar.txt"
 
-// RUN: rm -rf %t && mkdir %t
-// RUN: llvm-profdata merge -o %t/somefile.prof %S/Inputs/a.proftext
-// RUN: llvm-profdata merge -o %t/default.profdata %S/Inputs/a.proftext
-// RUN: cd %t
-
 // RUN: %clang -### -S -fprofile-use %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE %s
 // RUN: %clang -### -S -fprofile-instr-use %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE %s
-// RUN: mkdir -p %t/some/dir
-// RUN: cp %t/default.profdata %t/some/dir
-// RUN: %clang -### -S -fprofile-use=%t/some/dir %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-DIR %s
-// RUN: %clang -### -S -fprofile-instr-use=%t/somefile.prof %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
+// RUN: mkdir -p %t.d/some/dir
+// RUN: %clang -### -S -fprofile-use=%t.d/some/dir %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-DIR %s
+// RUN: %clang -### -S -fprofile-instr-use=/tmp/somefile.prof %s 2>&1 | FileCheck -check-prefix=CHECK-PROFILE-USE-FILE %s
 // CHECK-PROFILE-USE: "-fprofile-instrument-use-path=default.profdata"
-// CHECK-PROFILE-USE-DIR: "-fprofile-instrument-use-path={{.*}}some/dir{{/|\\\\}}default.profdata"
-// CHECK-PROFILE-USE-FILE: "-fprofile-instrument-use-path={{.*}}somefile.prof"
+// CHECK-PROFILE-USE-DIR: "-fprofile-instrument-use-path={{.*}}.d/some/dir{{/|\\\\}}default.profdata"
+// CHECK-PROFILE-USE-FILE: "-fprofile-instrument-use-path=/tmp/somefile.prof"
 
-// RUN: %clang -### -S -fprofile-instr-use=%t/somefile.prof -fdiagnostics-misexpect-tolerance=10 -Wmisexpect %s 2>&1 | FileCheck %s --check-prefix=CHECK-MISEXPECT-TOLLERANCE
+// RUN: %clang -### -S -fprofile-instr-use=%t.profdata -fdiagnostics-misexpect-tolerance=10 -Wmisexpect %s 2>&1 | FileCheck %s --check-prefix=CHECK-MISEXPECT-TOLLERANCE
 // CHECK-MISEXPECT-TOLLERANCE: "-fdiagnostics-misexpect-tolerance=10"
 // CHECK-MISEXPECT-TOLLERANCE-NOT: argument unused
 
diff --git a/clang/test/Driver/fcs-profile-generate.c b/clang/test/Driver/fcs-profile-generate.c
index ecb5aad58fd46..f69fa44be873e 100644
--- a/clang/test/Driver/fcs-profile-generate.c
+++ b/clang/test/Driver/fcs-profile-generate.c
@@ -1,14 +1,10 @@
-// RUN: rm -rf %t && mkdir %t
-// RUN: llvm-profdata merge -o %t/a.profdata %S/Inputs/a.proftext
-
-// RUN: %clang -### -c -fprofile-use=%t/a.profdata -fcs-profile-generate %s 2>&1 | FileCheck %s
+// RUN: %clang -### -c -fprofile-use=a.profdata -fcs-profile-generate %s 2>&1 | FileCheck %s
 // CHECK:      "-fprofile-instrument=csllvm"
 // CHECK-NOT:  "-fprofile-instrument-path=
-// CHECK-SAME: "-fprofile-instrument-use=llvm"
-// CHECK-SAME: "-fprofile-instrument-use-path={{.*}}a.profdata"
+// CHECK-SAME: "-fprofile-instrument-use-path=a.profdata"
 
-// RUN: %clang -### -c -fprofile-use=%t/a.profdata -fcs-profile-generate=dir %s 2>&1 | FileCheck %s --check-prefix=CHECK1
-// CHECK1: "-fprofile-instrument=csllvm"{{.*}} "-fprofile-instrument-path=dir{{/|\\\\}}default_%m.profraw" "-fprofile-instrument-use=llvm" "-fprofile-instrument-use-path={{.*}}a.profdata"
+// RUN: %clang -### -c -fprofile-use=a.profdata -fcs-profile-generate=dir %s 2>&1 | FileCheck %s --check-prefix=CHECK1
+// CHECK1: "-fprofile-instrument=csllvm"{{.*}} "-fprofile-instrument-path=dir{{/|\\\\}}default_%m.profraw" "-fprofile-instrument-use-path=a.profdata"
 
 /// Degradation case. This usage does not make much sense.
 // RUN: %clang -### -c -fcs-profile-generate %s 2>&1 | FileCheck %s --check-prefix=NOUSE
diff --git a/clang/test/Driver/fsplit-machine-functions.c b/clang/test/Driver/fsplit-machine-functions.c
index 153aafba8fbd0..02bab476e831d 100644
--- a/clang/test/Driver/fsplit-machine-functions.c
+++ b/clang/test/Driver/fsplit-machine-functions.c
@@ -1,13 +1,9 @@
-// RUN: rm -rf %t && mkdir %t
-// RUN: llvm-profdata merge -o %t/default.profdata %S/Inputs/a.proftext
-
-// RUN: %clang -### --target=x86_64 -fprofile-use=%t/default.profdata -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefixes=CHECK,LTO-NEG
-// RUN: %clang -### --target=aarch64 -fprofile-use=%t/default.profdata -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefixes=CHECK,LTO-NEG
-// RUN: %clang -### --target=x86_64 -fprofile-use=%t/default.profdata -fsplit-machine-functions -fno-split-machine-functions %s -c 2>&1 | FileCheck -check-prefix=NEG %s
+// RUN: %clang -### --target=x86_64 -fprofile-use=default.profdata -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefixes=CHECK,LTO-NEG
+// RUN: %clang -### --target=aarch64 -fprofile-use=default.profdata -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefixes=CHECK,LTO-NEG
+// RUN: %clang -### --target=x86_64 -fprofile-use=default.profdata -fsplit-machine-functions -fno-split-machine-functions %s -c 2>&1 | FileCheck -check-prefix=NEG %s
 
 // CHECK:      "-fsplit-machine-functions"
-// CHECK-SAME: "-fprofile-instrument-use=llvm"
-// CHECK-SAME: "-fprofile-instrument-use-path={{.*}}default.profdata"
+// CHECK-SAME: "-fprofile-instrument-use-path=default.profdata"
 
 // NEG-NOT:    "-fsplit-machine-functions"
 
diff --git a/clang/test/Frontend/optimization-remark-with-hotness-new-pm.c b/clang/test/Frontend/optimization-remark-with-hotness-new-pm.c
index 0c7e96182aebf..173b43ba41bfe 100644
--- a/clang/test/Frontend/optimization-remark-with-hotness-new-pm.c
+++ b/clang/test/Frontend/optimization-remark-with-hotness-new-pm.c
@@ -15,8 +15,7 @@
 //
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
 // RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
-// RUN:     -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata \
-// RUN:     -Rpass=inline \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
 // RUN:     -O1 \
 // RUN:     -Rpass-analysis=inline -Rpass-missed=inline \
 // RUN:     -fdiagnostics-show-hotness -verify
@@ -35,24 +34,24 @@
 // RUN:     -verify
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
 // RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
-// RUN:     -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
 // RUN:     -O1 \
 // RUN:     -Rpass-analysis=inline -Rpass-missed=inline \
 // RUN:     -fdiagnostics-show-hotness -fdiagnostics-hotness-threshold=10 -verify
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
 // RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
-// RUN:     -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
 // RUN:     -O1 \
 // RUN:     -Rpass-analysis=inline 2>&1 | FileCheck -check-prefix=HOTNESS_OFF %s
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
 // RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
-// RUN:     -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
 // RUN:     -O1 \
 // RUN:     -Rpass-analysis=inline -Rno-pass-with-hotness 2>&1 | FileCheck \
 // RUN:     -check-prefix=HOTNESS_OFF %s
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name \
 // RUN:     optimization-remark-with-hotness.c %s -emit-llvm-only \
-// RUN:     -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
+// RUN:     -fprofile-instrument-use-path=%t.profdata -Rpass=inline \
 // RUN:     -Rpass-analysis=inline -fdiagnostics-show-hotness \
 // RUN:     -fdiagnostics-hotness-threshold=100  2>&1 \
 // RUN:     | FileCheck -allow-empty -check-prefix=THRESHOLD %s
diff --git a/clang/test/Modules/modules-cache-path-canonicalization-output.c b/clang/test/Modules/modules-cache-path-canonicalization-output.c
deleted file mode 100644
index ad71b69e5299e..0000000000000
--- a/clang/test/Modules/modules-cache-path-canonicalization-output.c
+++ /dev/null
@@ -1,18 +0,0 @@
-// This checks that implicitly-built modules produce identical PCM
-// files regardless of the spelling of the same module cache path.
-
-// RUN: rm -rf %t
-// RUN: split-file %s %t
-
-// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fsyntax-only %t/tu.c \
-// RUN:   -fmodules-cache-path=%t/cache -fdisable-module-hash
-// RUN: mv %t/cache/M.pcm %t/M.pcm
-// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fsyntax-only %t/tu.c \
-// RUN:   -fmodules-cache-path=%t/./cache -fdisable-module-hash
-// RUN: diff %t/./cache/M.pcm %t/M.pcm
-
-//--- tu.c
-#include "M.h"
-//--- M.h
-//--- module.modulemap
-module M { header "M.h" }
diff --git a/clang/test/OpenMP/amdgcn_save_temps.c b/clang/test/OpenMP/amdgcn_save_temps.c
deleted file mode 100644
index d838bb1166b6b..0000000000000
--- a/clang/test/OpenMP/amdgcn_save_temps.c
+++ /dev/null
@@ -1,23 +0,0 @@
-
-// REQUIRES: amdgpu-registered-target
-
-// RUN: %clang_cc1 -E -fopenmp -x c -triple amdgcn-amd-amdhsa -fopenmp-targets=amdgcn-amd-amdhsa -save-temps=cwd %s -o %t-openmp-amdgcn-amd-amdhsa-gfx90a.i
-// RUN: %clang_cc1 -fopenmp  -x c -triple x86_64-unknown-unknown -fopenmp-targets=amdgcn-amd-amdhsa -save-temps=cwd -emit-llvm-bc %s -o %t-x86_64-unknown-unknown.bc
-// RUN: %clang_cc1 -fopenmp -x c -triple amdgcn-amd-amdhsa -fopenmp-targets=amdgcn-amd-amdhsa -save-temps=cwd -emit-llvm -fopenmp-is-target-device -x cpp-output %t-openmp-amdgcn-amd-amdhsa-gfx90a.i -fopenmp-host-ir-file-path %t-x86_64-unknown-unknown.bc -o - | FileCheck %s
-// expected-no-diagnostics
-#ifndef HEADER
-#define HEADER
-
-#define N 1000
-
-int test_amdgcn_save_temps() {
-  int arr[N];
-#pragma omp target
-  for (int i = 0; i < N; i++) {
-    arr[i] = 1;
-  }
-  return arr[0];
-}
-#endif
-
-// CHECK: define {{[^@]+}}@{{__omp_offloading_[0-9a-z]+_[0-9a-z]+}}_test_amdgcn_save_temps
diff --git a/clang/test/OpenMP/host-ir-file-vfs.c b/clang/test/OpenMP/host-ir-file-vfs.c
deleted file mode 100644
index 394d8fbcc94ac..0000000000000
--- a/clang/test/OpenMP/host-ir-file-vfs.c
+++ /dev/null
@@ -1,33 +0,0 @@
-// This test checks that the OpenMP host IR file goes through VFS overlays.
-
-// RUN: rm -rf %t
-// RUN: split-file %s %t
-
-// RUN: sed -e "s|DIR|%/t|g" %t/vfs.json.in > %t/vfs.json
-// RUN: %clang_cc1 -fopenmp-simd -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-llvm-bc %t/host.c -o %t/host.bc
-
-// RUN: %clang_cc1 -fopenmp-simd -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-llvm %t/device.c -o - \
-// RUN:   -fopenmp-is-target-device -fopenmp-host-ir-file-path %t/virtual/host.bc -ivfsoverlay %t/vfs.json -verify
-
-//--- vfs.json.in
-{
-  'version': 0,
-  'use-external-names': true,
-  'roots': [
-    {
-      'name': 'DIR/virtual',
-      'type': 'directory',
-      'contents': [
-        {
-          'name': 'host.bc',
-          'type': 'file',
-          'external-contents': 'DIR/host.bc'
-        }
-      ]
-    }
-  ]
-}
-
-//--- host.c
-//--- device.c
-// expected-no-diagnostics
diff --git a/clang/test/Profile/c-captured.c b/clang/test/Profile/c-captured.c
index e38798983b6c2..3a802494eb6a6 100644
--- a/clang/test/Profile/c-captured.c
+++ b/clang/test/Profile/c-captured.c
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-captured.c %s -o - -emit-llvm -fprofile-instrument=clang | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOGEN -check-prefix=PGOALL %s
 
 // RUN: llvm-profdata merge %S/Inputs/c-captured.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-captured.c %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE -check-prefix=PGOALL %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-captured.c %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE -check-prefix=PGOALL %s
 
 // PGOGEN: @[[DCC:__profc_debug_captured]] = private global [3 x i64] zeroinitializer
 // PGOGEN: @[[CSC:__profc_c_captured.c___captured_stmt]] = private global [2 x i64] zeroinitializer
diff --git a/clang/test/Profile/c-counter-overflows.c b/clang/test/Profile/c-counter-overflows.c
index bc12865b32b5d..5cb32bbc30af4 100644
--- a/clang/test/Profile/c-counter-overflows.c
+++ b/clang/test/Profile/c-counter-overflows.c
@@ -2,7 +2,7 @@
 // truncated.
 
 // RUN: llvm-profdata merge %S/Inputs/c-counter-overflows.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-counter-overflows.c %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-counter-overflows.c %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata | FileCheck %s
 
 typedef unsigned long long uint64_t;
 
diff --git a/clang/test/Profile/c-general.c b/clang/test/Profile/c-general.c
index ee36a43dac081..2f621ec9b0bf9 100644
--- a/clang/test/Profile/c-general.c
+++ b/clang/test/Profile/c-general.c
@@ -3,11 +3,11 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument=clang | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOGEN %s
 
 // RUN: llvm-profdata merge %S/Inputs/c-general.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%S/Inputs/c-general.profdata.v5 | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%S/Inputs/c-general.profdata.v3 | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use-path=%S/Inputs/c-general.profdata.v5 | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use-path=%S/Inputs/c-general.profdata.v3 | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
 // Also check compatibility with older profiles.
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%S/Inputs/c-general.profdata.v1 | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-general.c %s -o - -emit-llvm -fprofile-instrument-use-path=%S/Inputs/c-general.profdata.v1 | FileCheck -allow-deprecated-dag-overlap  -check-prefix=PGOUSE %s
 
 // RUN: %clang -fprofile-generate -E -dM %s | FileCheck -match-full-lines -check-prefix=PROFGENMACRO %s
 // RUN: %clang -fprofile-instr-generate -E -dM %s | FileCheck -match-full-lines -check-prefix=PROFGENMACRO %s
diff --git a/clang/test/Profile/c-outdated-data.c b/clang/test/Profile/c-outdated-data.c
index 7071401599b89..454e4d799e0bb 100644
--- a/clang/test/Profile/c-outdated-data.c
+++ b/clang/test/Profile/c-outdated-data.c
@@ -4,8 +4,8 @@
 // doesn't play well with warnings that have no line number.
 
 // RUN: llvm-profdata merge %S/Inputs/c-outdated-data.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-outdated-data.c %s -o /dev/null -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -check-prefix=NO_MISSING
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-outdated-data.c %s -o /dev/null -emit-llvm -Wprofile-instr-missing -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -check-prefix=WITH_MISSING
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-outdated-data.c %s -o /dev/null -emit-llvm -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -check-prefix=NO_MISSING
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-outdated-data.c %s -o /dev/null -emit-llvm -Wprofile-instr-missing -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -check-prefix=WITH_MISSING
 
 // NO_MISSING: warning: profile data may be out of date: of 3 functions, 2 have mismatched data that will be ignored
 // NO_MISSING-NOT: 1 has no data
diff --git a/clang/test/Profile/c-unprofiled-blocks.c b/clang/test/Profile/c-unprofiled-blocks.c
index bcf3e06371e09..e25bbc50de2ba 100644
--- a/clang/test/Profile/c-unprofiled-blocks.c
+++ b/clang/test/Profile/c-unprofiled-blocks.c
@@ -2,7 +2,7 @@
 // runs) shouldn't have any branch weight metadata added.
 
 // RUN: llvm-profdata merge %S/Inputs/c-unprofiled-blocks.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-unprofiled-blocks.c %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata | FileCheck -check-prefix=PGOUSE %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-unprofiled-blocks.c %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata | FileCheck -check-prefix=PGOUSE %s
 
 // PGOUSE-LABEL: @never_called(i32 noundef %i)
 int never_called(int i) {
diff --git a/clang/test/Profile/c-unprofiled.c b/clang/test/Profile/c-unprofiled.c
index 3f52d773e1c06..3466079f69bd8 100644
--- a/clang/test/Profile/c-unprofiled.c
+++ b/clang/test/Profile/c-unprofiled.c
@@ -7,7 +7,7 @@
 // doesn't play well with warnings that have no line number.
 
 // RUN: llvm-profdata merge %S/Inputs/c-unprofiled.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-unprofiled.c -I %S/Inputs/ %s -o /dev/null -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -Wprofile-instr-unprofiled 2>&1 | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-unprofiled.c -I %S/Inputs/ %s -o /dev/null -emit-llvm -fprofile-instrument-use-path=%t.profdata -Wprofile-instr-unprofiled 2>&1 | FileCheck %s
 
 // CHECK: warning: no profile data available for file "c-unprofiled.c"
 
diff --git a/clang/test/Profile/cxx-class.cpp b/clang/test/Profile/cxx-class.cpp
index ce9ddcfc4553f..c38a81e0d86e8 100644
--- a/clang/test/Profile/cxx-class.cpp
+++ b/clang/test/Profile/cxx-class.cpp
@@ -9,7 +9,7 @@
 // RUN: FileCheck --input-file=%tgen -check-prefix=VDTRGEN %s
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-class.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -triple %itanium_abi_triple > %tuse
+// RUN: %clang_cc1 %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -triple %itanium_abi_triple > %tuse
 // RUN: FileCheck --input-file=%tuse -check-prefix=CTRUSE %s
 // RUN: FileCheck --input-file=%tuse -check-prefix=DTRUSE %s
 // RUN: FileCheck --input-file=%tuse -check-prefix=MTHUSE %s
diff --git a/clang/test/Profile/cxx-hash-v2.cpp b/clang/test/Profile/cxx-hash-v2.cpp
index 0696b20bdcac3..995fe008f5236 100644
--- a/clang/test/Profile/cxx-hash-v2.cpp
+++ b/clang/test/Profile/cxx-hash-v2.cpp
@@ -8,8 +8,8 @@
 // RUN: diff %t.hashes %t.hashes.unique
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-hash-v2.proftext -o %t.profdata
-// RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -triple x86_64-apple-macosx10.9 -main-file-name cxx-hash-v2.mm %s -o /dev/null -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -allow-empty
-// RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -triple x86_64-apple-macosx10.9 -main-file-name cxx-hash-v2.mm %s -o /dev/null -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%S/Inputs/cxx-hash-v2.profdata.v5 2>&1 | FileCheck %s -allow-empty
+// RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -triple x86_64-apple-macosx10.9 -main-file-name cxx-hash-v2.mm %s -o /dev/null -emit-llvm -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck %s -allow-empty
+// RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -triple x86_64-apple-macosx10.9 -main-file-name cxx-hash-v2.mm %s -o /dev/null -emit-llvm -fprofile-instrument-use-path=%S/Inputs/cxx-hash-v2.profdata.v5 2>&1 | FileCheck %s -allow-empty
 
 // CHECK-NOT: warning: profile data may be out of date
 
diff --git a/clang/test/Profile/cxx-lambda.cpp b/clang/test/Profile/cxx-lambda.cpp
index b05fdd3d26b7c..589f922c70782 100644
--- a/clang/test/Profile/cxx-lambda.cpp
+++ b/clang/test/Profile/cxx-lambda.cpp
@@ -5,7 +5,7 @@
 // RUN: FileCheck -allow-deprecated-dag-overlap  --input-file=%tgen -check-prefix=LMBGEN %s
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-lambda.proftext -o %t.profdata
-// RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-lambda.cpp -std=c++11 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata > %tuse
+// RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-lambda.cpp -std=c++11 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata > %tuse
 // RUN: FileCheck -allow-deprecated-dag-overlap  --input-file=%tuse -check-prefix=PGOUSE %s
 // RUN: FileCheck -allow-deprecated-dag-overlap  --input-file=%tuse -check-prefix=LMBUSE %s
 
diff --git a/clang/test/Profile/cxx-missing-bodies.cpp b/clang/test/Profile/cxx-missing-bodies.cpp
index 87541c2825b25..6d34fca482c99 100644
--- a/clang/test/Profile/cxx-missing-bodies.cpp
+++ b/clang/test/Profile/cxx-missing-bodies.cpp
@@ -2,7 +2,7 @@
 //
 // Don't crash when presented profile data for functions without bodies:
 // RUN: llvm-profdata merge %S/Inputs/cxx-missing-bodies.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -std=c++11 -emit-llvm-only -triple=i386-pc-win32 -fno-rtti -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -w
+// RUN: %clang_cc1 %s -std=c++11 -emit-llvm-only -triple=i386-pc-win32 -fno-rtti -fprofile-instrument-use-path=%t.profdata -w
 
 // GEN-NOT: __profn{{.*}}??_GA@@UAEPAXI@Z
 // GEN-NOT: __profn{{.*}}??_DA@@QAEXXZ
diff --git a/clang/test/Profile/cxx-never-executed-branch.cpp b/clang/test/Profile/cxx-never-executed-branch.cpp
index d7bdd3c67a15d..812f65f3996d3 100644
--- a/clang/test/Profile/cxx-never-executed-branch.cpp
+++ b/clang/test/Profile/cxx-never-executed-branch.cpp
@@ -1,7 +1,7 @@
 // Test that clang doesn't emit llvm.expect when the counter is 0
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-never-executed-branch.proftext -o %t.profdata
-// RUN: %clang_cc1 -std=c++20 %s -triple %itanium_abi_triple -O2 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -disable-llvm-passes | FileCheck %s
+// RUN: %clang_cc1 -std=c++20 %s -triple %itanium_abi_triple -O2 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -disable-llvm-passes | FileCheck %s
 
 int rand();
 
diff --git a/clang/test/Profile/cxx-rangefor.cpp b/clang/test/Profile/cxx-rangefor.cpp
index 43bdaa9b70aeb..58c578c3c1017 100644
--- a/clang/test/Profile/cxx-rangefor.cpp
+++ b/clang/test/Profile/cxx-rangefor.cpp
@@ -4,7 +4,7 @@
 // RUN: FileCheck --input-file=%tgen -check-prefix=CHECK -check-prefix=PGOGEN %s
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-rangefor.proftext -o %t.profdata
-// RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-rangefor.cpp -std=c++11 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata > %tuse
+// RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-rangefor.cpp -std=c++11 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata > %tuse
 // RUN: FileCheck --input-file=%tuse -check-prefix=CHECK -check-prefix=PGOUSE %s
 
 // PGOGEN: @[[RFC:__profc__Z9range_forv]] = {{(private|internal)}} global [5 x i64] zeroinitializer
diff --git a/clang/test/Profile/cxx-templates.cpp b/clang/test/Profile/cxx-templates.cpp
index 09cf11e841dc4..51c8f1f6d1edd 100644
--- a/clang/test/Profile/cxx-templates.cpp
+++ b/clang/test/Profile/cxx-templates.cpp
@@ -6,7 +6,7 @@
 // RUN: FileCheck --input-file=%tgen -check-prefix=T100GEN -check-prefix=ALL %s
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-templates.proftext -o %t.profdata
-// RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-templates.cpp -std=c++11 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata > %tuse
+// RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-templates.cpp -std=c++11 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata > %tuse
 // RUN: FileCheck --input-file=%tuse -check-prefix=T0USE -check-prefix=ALL %s
 // RUN: FileCheck --input-file=%tuse -check-prefix=T100USE -check-prefix=ALL %s
 
diff --git a/clang/test/Profile/cxx-throws.cpp b/clang/test/Profile/cxx-throws.cpp
index fc04add24b97d..e989c2d39dfbb 100644
--- a/clang/test/Profile/cxx-throws.cpp
+++ b/clang/test/Profile/cxx-throws.cpp
@@ -7,8 +7,8 @@
 // RUN: %clang_cc1 %s -o - -emit-llvm -fprofile-instrument=clang -fexceptions -fcxx-exceptions -triple %itanium_abi_triple | FileCheck -check-prefix=PGOGEN-EXC %s
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-throws.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -fexceptions -fcxx-exceptions -triple %itanium_abi_triple | FileCheck -check-prefix=PGOUSE %s
-// RUN: %clang_cc1 %s -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -fexceptions -fcxx-exceptions -triple %itanium_abi_triple | FileCheck -check-prefix=PGOUSE-EXC %s
+// RUN: %clang_cc1 %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -fexceptions -fcxx-exceptions -triple %itanium_abi_triple | FileCheck -check-prefix=PGOUSE %s
+// RUN: %clang_cc1 %s -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -fexceptions -fcxx-exceptions -triple %itanium_abi_triple | FileCheck -check-prefix=PGOUSE-EXC %s
 
 // PGOGEN: @[[THC:__profc__Z6throwsv]] = {{(private|internal)}} global [9 x i64] zeroinitializer
 // PGOGEN-EXC: @[[THC:__profc__Z6throwsv]] = {{(private|internal)}} global [9 x i64] zeroinitializer
diff --git a/clang/test/Profile/func-entry.c b/clang/test/Profile/func-entry.c
index 27d11cc254ea8..4a4ca2288352b 100644
--- a/clang/test/Profile/func-entry.c
+++ b/clang/test/Profile/func-entry.c
@@ -1,7 +1,7 @@
 // Test that function entry counts are set correctly.
 
 // RUN: llvm-profdata merge %S/Inputs/func-entry.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata | FileCheck %s
+// RUN: %clang_cc1 %s -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use-path=%t.profdata | FileCheck %s
 
 void foo(void);
 
diff --git a/clang/test/Profile/misexpect-branch-cold.c b/clang/test/Profile/misexpect-branch-cold.c
index 43ef3fcdda0ba..6d34f92a25454 100644
--- a/clang/test/Profile/misexpect-branch-cold.c
+++ b/clang/test/Profile/misexpect-branch-cold.c
@@ -1,7 +1,7 @@
 // Test that misexpect emits no warning when prediction is correct
 
 // RUN: llvm-profdata merge %S/Inputs/misexpect-branch.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect
+// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect
 
 // expected-no-diagnostics
 #define likely(x) __builtin_expect(!!(x), 1)
diff --git a/clang/test/Profile/misexpect-branch-nonconst-expected-val.c b/clang/test/Profile/misexpect-branch-nonconst-expected-val.c
index fa2b4f1755040..c5167b9a2a0b7 100644
--- a/clang/test/Profile/misexpect-branch-nonconst-expected-val.c
+++ b/clang/test/Profile/misexpect-branch-nonconst-expected-val.c
@@ -1,7 +1,7 @@
 // Test that misexpect emits no warning when condition is not a compile-time constant
 
 // RUN: llvm-profdata merge %S/Inputs/misexpect-branch-nonconst-expect-arg.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect
+// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect
 
 // expected-no-diagnostics
 int foo(int);
diff --git a/clang/test/Profile/misexpect-branch-unpredictable.c b/clang/test/Profile/misexpect-branch-unpredictable.c
index ffaf25aed82bd..6c4f90146a2ae 100644
--- a/clang/test/Profile/misexpect-branch-unpredictable.c
+++ b/clang/test/Profile/misexpect-branch-unpredictable.c
@@ -1,7 +1,7 @@
 // Test that misexpect emits no warning when prediction is correct
 
 // RUN: llvm-profdata merge %S/Inputs/misexpect-branch.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect
+// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect
 
 // expected-no-diagnostics
 #define unpredictable(x) __builtin_unpredictable(!!(x))
diff --git a/clang/test/Profile/misexpect-branch.c b/clang/test/Profile/misexpect-branch.c
index fb7225047fcb0..5c4394405e178 100644
--- a/clang/test/Profile/misexpect-branch.c
+++ b/clang/test/Profile/misexpect-branch.c
@@ -2,12 +2,12 @@
 
 // test diagnostics are issued when profiling data mis-matches annotations
 // RUN: llvm-profdata merge %S/Inputs/misexpect-branch.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify=imprecise -Wmisexpect
-// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify=exact -Wmisexpect -debug-info-kind=line-tables-only
+// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify=imprecise -Wmisexpect
+// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify=exact -Wmisexpect -debug-info-kind=line-tables-only
 
 // there should be no diagnostics when the tolerance is sufficiently high, or when -Wmisexpect is not requested
-// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify=foo -fdiagnostics-misexpect-tolerance=10 -Wmisexpect -debug-info-kind=line-tables-only
-// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify=foo
+// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify=foo -fdiagnostics-misexpect-tolerance=10 -Wmisexpect -debug-info-kind=line-tables-only
+// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify=foo
 
 // Ensure we emit an error when we don't use pgo with tolerance threshold
 // RUN: %clang_cc1 %s -O2 -o - -emit-llvm  -fdiagnostics-misexpect-tolerance=10 -Wmisexpect -debug-info-kind=line-tables-only 2>&1 | FileCheck -check-prefix=NO_PGO %s
diff --git a/clang/test/Profile/misexpect-switch-default.c b/clang/test/Profile/misexpect-switch-default.c
index 89eb64fea420b..cd337b9430171 100644
--- a/clang/test/Profile/misexpect-switch-default.c
+++ b/clang/test/Profile/misexpect-switch-default.c
@@ -1,7 +1,7 @@
 // Test that misexpect detects mis-annotated switch statements for default case
 
 // RUN: llvm-profdata merge %S/Inputs/misexpect-switch-default.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect -debug-info-kind=line-tables-only
+// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect -debug-info-kind=line-tables-only
 
 #define inner_loop 1000
 #define outer_loop 20
diff --git a/clang/test/Profile/misexpect-switch-nonconst.c b/clang/test/Profile/misexpect-switch-nonconst.c
index f18baea83cc1d..cff3bce0d6d0a 100644
--- a/clang/test/Profile/misexpect-switch-nonconst.c
+++ b/clang/test/Profile/misexpect-switch-nonconst.c
@@ -1,7 +1,7 @@
 // Test that misexpect emits no warning when switch condition is non-const
 
 // RUN: llvm-profdata merge %S/Inputs/misexpect-switch-nonconst.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify
+// RUN: %clang_cc1 %s -O2 -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify
 
 // expected-no-diagnostics
 
diff --git a/clang/test/Profile/misexpect-switch-only-default-case.c b/clang/test/Profile/misexpect-switch-only-default-case.c
index ef0f124305625..26e8564c81b54 100644
--- a/clang/test/Profile/misexpect-switch-only-default-case.c
+++ b/clang/test/Profile/misexpect-switch-only-default-case.c
@@ -1,7 +1,7 @@
 // Test that misexpect emits no warning when there is only one switch case
 
 // RUN: llvm-profdata merge %S/Inputs/misexpect-switch-default-only.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect -debug-info-kind=line-tables-only
+// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect -debug-info-kind=line-tables-only
 
 // expected-no-diagnostics
 
diff --git a/clang/test/Profile/misexpect-switch.c b/clang/test/Profile/misexpect-switch.c
index ae13cf7675706..84a7174f635fd 100644
--- a/clang/test/Profile/misexpect-switch.c
+++ b/clang/test/Profile/misexpect-switch.c
@@ -1,7 +1,7 @@
 // Test that misexpect detects mis-annotated switch statements
 
 // RUN: llvm-profdata merge %S/Inputs/misexpect-switch.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect -debug-info-kind=line-tables-only
+// RUN: %clang_cc1 %s -O2 -o - -emit-llvm -fprofile-instrument-use-path=%t.profdata -verify -Wmisexpect -debug-info-kind=line-tables-only
 
 #define inner_loop 1000
 #define outer_loop 20
diff --git a/clang/test/Profile/objc-general.m b/clang/test/Profile/objc-general.m
index a711645e7c833..a3dcb1b2128c6 100644
--- a/clang/test/Profile/objc-general.m
+++ b/clang/test/Profile/objc-general.m
@@ -3,7 +3,7 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name objc-general.m %s -o - -emit-llvm -fblocks -fprofile-instrument=clang | FileCheck -check-prefix=PGOGEN %s
 
 // RUN: llvm-profdata merge %S/Inputs/objc-general.proftext -o %t.profdata
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name objc-general.m %s -o - -emit-llvm -fblocks -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck -check-prefix=PGOUSE %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name objc-general.m %s -o - -emit-llvm -fblocks -fprofile-instrument-use-path=%t.profdata 2>&1 | FileCheck -check-prefix=PGOUSE %s
 
 // PGOUSE-NOT: warning: profile data may be out of date
 
diff --git a/clang/test/Profile/profile-does-not-exist-ir.c b/clang/test/Profile/profile-does-not-exist-ir.c
index cb7bef2b7043b..842a3d44a387b 100644
--- a/clang/test/Profile/profile-does-not-exist-ir.c
+++ b/clang/test/Profile/profile-does-not-exist-ir.c
@@ -1,8 +1,4 @@
-; RUN: not %clang_cc1 -emit-llvm -x ir %s -o - -fprofile-instrument-use=llvm -fprofile-instrument-use-path=%t.nonexistent.profdata 2>&1 | FileCheck %s
+// RUN: not %clang_cc1 -emit-llvm -x ir %s -o - -fprofile-instrument-use-path=%t.nonexistent.profdata 2>&1 | FileCheck %s
 
-; CHECK: error: {{.*}}.nonexistent.profdata:
-; CHECK-NOT: Assertion failed
-
-define i32 @main() {
-  ret i32 0
-}
+// CHECK: error: Error in reading profile {{.*}}.nonexistent.profdata:
+// CHECK-NOT: Assertion failed
diff --git a/clang/test/Profile/profile-does-not-exist.c b/clang/test/Profile/profile-does-not-exist.c
index e9e04bed19b84..88d55d8668ef8 100644
--- a/clang/test/Profile/profile-does-not-exist.c
+++ b/clang/test/Profile/profile-does-not-exist.c
@@ -1,8 +1,4 @@
-// RUN: not %clang_cc1 -emit-llvm %s -o - -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.nonexistent.profdata 2>&1 | FileCheck %s
+// RUN: not %clang_cc1 -emit-llvm %s -o - -fprofile-instrument-use-path=%t.nonexistent.profdata 2>&1 | FileCheck %s
 
 // CHECK: error: Error in reading profile {{.*}}.nonexistent.profdata:
 // CHECK-NOT: Assertion failed
-
-int main() {
-  return 0;
-}
diff --git a/clang/test/Profile/profile-summary.c b/clang/test/Profile/profile-summary.c
index 31e8497ed6398..47fd9e85a4539 100644
--- a/clang/test/Profile/profile-summary.c
+++ b/clang/test/Profile/profile-summary.c
@@ -1,7 +1,7 @@
 // Test that profile summary is set correctly.
 
 // RUN: llvm-profdata merge %S/Inputs/max-function-count.proftext -o %t.profdata
-// RUN: %clang_cc1 %s -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use=clang -fprofile-instrument-use-path=%t.profdata | FileCheck %s
+// RUN: %clang_cc1 %s -o - -disable-llvm-passes -emit-llvm -fprofile-instrument-use-path=%t.profdata | FileCheck %s
 //
 int begin(int i) {
   if (i)
diff --git a/clang/test/VFS/broken-vfs-module-dep.c b/clang/test/VFS/broken-vfs-module-dep.c
index 1c371a13e85c9..2336306de8c6d 100644
--- a/clang/test/VFS/broken-vfs-module-dep.c
+++ b/clang/test/VFS/broken-vfs-module-dep.c
@@ -2,5 +2,6 @@
 // RUN: mkdir -p %t
 // RUN: not %clang_cc1 -module-dependency-dir %t -ivfsoverlay %S/Inputs/invalid-yaml.yaml %s 2>&1 | FileCheck %s
 
+// CHECK: error: Unexpected token
 // CHECK: error: Unexpected token
 // CHECK: 1 error generated
diff --git a/clang/tools/c-index-test/core_main.cpp b/clang/tools/c-index-test/core_main.cpp
index c5dc54b98f3bd..100e708feb721 100644
--- a/clang/tools/c-index-test/core_main.cpp
+++ b/clang/tools/c-index-test/core_main.cpp
@@ -369,13 +369,12 @@ static bool printSourceSymbolsFromModule(StringRef modulePath,
 
   HeaderSearchOptions HSOpts;
 
-  auto VFS = llvm::vfs::getRealFileSystem();
-
   auto DiagOpts = std::make_shared<DiagnosticOptions>();
   IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(*VFS, *DiagOpts);
+      CompilerInstance::createDiagnostics(*llvm::vfs::getRealFileSystem(),
+                                          *DiagOpts);
   std::unique_ptr<ASTUnit> AU = ASTUnit::LoadFromASTFile(
-      modulePath, *pchRdr, ASTUnit::LoadASTOnly, VFS, DiagOpts, Diags,
+      modulePath, *pchRdr, ASTUnit::LoadASTOnly, DiagOpts, Diags,
       FileSystemOpts, HSOpts, /*LangOpts=*/nullptr,
       /*OnlyLocalDecls=*/true, CaptureDiagsKind::None,
       /*AllowASTWithCompilerErrors=*/true,
diff --git a/clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp b/clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp
index 64cb012788548..0b621b849e92f 100644
--- a/clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp
+++ b/clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp
@@ -158,8 +158,8 @@ static bool HandleAST(StringRef AstPath) {
 
   std::unique_ptr<ASTUnit> Unit = ASTUnit::LoadFromASTFile(
       AstPath, CI->getPCHContainerOperations()->getRawReader(),
-      ASTUnit::LoadASTOnly, CI->getVirtualFileSystemPtr(), DiagOpts, DiagEngine,
-      CI->getFileSystemOpts(), CI->getHeaderSearchOpts());
+      ASTUnit::LoadASTOnly, DiagOpts, DiagEngine, CI->getFileSystemOpts(),
+      CI->getHeaderSearchOpts());
 
   if (!Unit)
     return false;
diff --git a/clang/tools/clang-import-test/clang-import-test.cpp b/clang/tools/clang-import-test/clang-import-test.cpp
index 2ad194f8e170b..7f5df9259889b 100644
--- a/clang/tools/clang-import-test/clang-import-test.cpp
+++ b/clang/tools/clang-import-test/clang-import-test.cpp
@@ -207,8 +207,8 @@ std::unique_ptr<CompilerInstance> BuildCompilerInstance() {
 
   auto Ins = std::make_unique<CompilerInstance>(std::move(Inv));
 
-  Ins->createVirtualFileSystem(llvm::vfs::getRealFileSystem(), DC.get());
-  Ins->createDiagnostics(DC.release(), /*ShouldOwnClient=*/true);
+  Ins->createDiagnostics(*llvm::vfs::getRealFileSystem(), DC.release(),
+                         /*ShouldOwnClient=*/true);
 
   TargetInfo *TI = TargetInfo::CreateTargetInfo(
       Ins->getDiagnostics(), Ins->getInvocation().getTargetOpts());
@@ -216,7 +216,7 @@ std::unique_ptr<CompilerInstance> BuildCompilerInstance() {
   Ins->getTarget().adjust(Ins->getDiagnostics(), Ins->getLangOpts(),
                           /*AuxTarget=*/nullptr);
   Ins->createFileManager();
-  Ins->createSourceManager();
+  Ins->createSourceManager(Ins->getFileManager());
   Ins->createPreprocessor(TU_Complete);
 
   return Ins;
diff --git a/clang/tools/clang-installapi/ClangInstallAPI.cpp b/clang/tools/clang-installapi/ClangInstallAPI.cpp
index 49d84069e86f4..6bc642f971a48 100644
--- a/clang/tools/clang-installapi/ClangInstallAPI.cpp
+++ b/clang/tools/clang-installapi/ClangInstallAPI.cpp
@@ -114,7 +114,7 @@ static bool run(ArrayRef<const char *> Args, const char *ProgName) {
   // Set up compilation.
   std::unique_ptr<CompilerInstance> CI(new CompilerInstance());
   CI->setFileManager(FM.get());
-  CI->createDiagnostics();
+  CI->createDiagnostics(FM->getVirtualFileSystem());
   if (!CI->hasDiagnostics())
     return EXIT_FAILURE;
 
diff --git a/clang/tools/driver/cc1_main.cpp b/clang/tools/driver/cc1_main.cpp
index 49bb7e5e63d19..d5fc4db7a0e68 100644
--- a/clang/tools/driver/cc1_main.cpp
+++ b/clang/tools/driver/cc1_main.cpp
@@ -275,11 +275,8 @@ int cc1_main(ArrayRef<const char *> Argv, const char *Argv0, void *MainAddr) {
     Clang->getHeaderSearchOpts().ResourceDir =
       CompilerInvocation::GetResourcesPath(Argv0, MainAddr);
 
-  /// Create the actual file system.
-  Clang->createVirtualFileSystem(llvm::vfs::getRealFileSystem(), DiagsBuffer);
-
   // Create the actual diagnostics engine.
-  Clang->createDiagnostics();
+  Clang->createDiagnostics(*llvm::vfs::getRealFileSystem());
   if (!Clang->hasDiagnostics())
     return 1;
 
@@ -350,7 +347,8 @@ int cc1_main(ArrayRef<const char *> Argv, const char *Argv0, void *MainAddr) {
     // options are stored in the compiler invocation and we can recreate the VFS
     // from the compiler invocation.
     if (!Clang->hasFileManager())
-      Clang->createFileManager();
+      Clang->createFileManager(createVFSFromCompilerInvocation(
+          Clang->getInvocation(), Clang->getDiagnostics()));
 
     llvm::vfs::OnDiskOutputBackend Backend;
     if (std::optional<llvm::vfs::OutputFile> profilerOutput =
diff --git a/clang/tools/driver/cc1as_main.cpp b/clang/tools/driver/cc1as_main.cpp
index 207f9f11c4de9..3b4a4b54392df 100644
--- a/clang/tools/driver/cc1as_main.cpp
+++ b/clang/tools/driver/cc1as_main.cpp
@@ -429,8 +429,7 @@ getOutputStream(StringRef Path, DiagnosticsEngine &Diags, bool Binary) {
 }
 
 static bool ExecuteAssemblerImpl(AssemblerInvocation &Opts,
-                                 DiagnosticsEngine &Diags,
-                                 IntrusiveRefCntPtr<vfs::FileSystem> VFS) {
+                                 DiagnosticsEngine &Diags) {
   // Get the target specific parser.
   std::string Error;
   const Target *TheTarget = TargetRegistry::lookupTarget(Opts.Triple, Error);
@@ -453,7 +452,6 @@ static bool ExecuteAssemblerImpl(AssemblerInvocation &Opts,
   // Record the location of the include directories so that the lexer can find
   // it later.
   SrcMgr.setIncludeDirs(Opts.IncludePaths);
-  SrcMgr.setVirtualFileSystem(VFS);
 
   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(Opts.Triple));
   assert(MRI && "Unable to create target register info!");
@@ -649,9 +647,8 @@ static bool ExecuteAssemblerImpl(AssemblerInvocation &Opts,
 }
 
 static bool ExecuteAssembler(AssemblerInvocation &Opts,
-                             DiagnosticsEngine &Diags,
-                             IntrusiveRefCntPtr<vfs::FileSystem> VFS) {
-  bool Failed = ExecuteAssemblerImpl(Opts, Diags, VFS);
+                             DiagnosticsEngine &Diags) {
+  bool Failed = ExecuteAssemblerImpl(Opts, Diags);
 
   // Delete output file if there were errors.
   if (Failed) {
@@ -688,8 +685,6 @@ int cc1as_main(ArrayRef<const char *> Argv, const char *Argv0, void *MainAddr) {
   IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
   DiagnosticsEngine Diags(DiagID, DiagOpts, DiagClient);
 
-  auto VFS = vfs::getRealFileSystem();
-
   // Set an error handler, so that any LLVM backend diagnostics go through our
   // error handler.
   ScopedFatalErrorHandler FatalErrorHandler
@@ -728,12 +723,11 @@ int cc1as_main(ArrayRef<const char *> Argv, const char *Argv0, void *MainAddr) {
     for (unsigned i = 0; i != NumArgs; ++i)
       Args[i + 1] = Asm.LLVMArgs[i].c_str();
     Args[NumArgs + 1] = nullptr;
-    llvm::cl::ParseCommandLineOptions(NumArgs + 1, Args.get(), /*Overview=*/"",
-                                      /*Errs=*/nullptr, /*VFS=*/VFS.get());
+    llvm::cl::ParseCommandLineOptions(NumArgs + 1, Args.get());
   }
 
   // Execute the invocation, unless there were parsing errors.
-  bool Failed = Diags.hasErrorOccurred() || ExecuteAssembler(Asm, Diags, VFS);
+  bool Failed = Diags.hasErrorOccurred() || ExecuteAssembler(Asm, Diags);
 
   // If any timers were active but haven't been destroyed yet, print their
   // results now.
diff --git a/clang/tools/driver/driver.cpp b/clang/tools/driver/driver.cpp
index 987fec0bdfb29..aca3577b410b0 100644
--- a/clang/tools/driver/driver.cpp
+++ b/clang/tools/driver/driver.cpp
@@ -217,8 +217,7 @@ static void FixupDiagPrefixExeName(TextDiagnosticPrinter *DiagClient,
 }
 
 static int ExecuteCC1Tool(SmallVectorImpl<const char *> &ArgV,
-                          const llvm::ToolContext &ToolContext,
-                          IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
+                          const llvm::ToolContext &ToolContext) {
   // If we call the cc1 tool from the clangDriver library (through
   // Driver::CC1Main), we need to clean up the options usage count. The options
   // are currently global, and they might have been used previously by the
@@ -226,8 +225,7 @@ static int ExecuteCC1Tool(SmallVectorImpl<const char *> &ArgV,
   llvm::cl::ResetAllOptionOccurrences();
 
   llvm::BumpPtrAllocator A;
-  llvm::cl::ExpansionContext ECtx(A, llvm::cl::TokenizeGNUCommandLine,
-                                  VFS.get());
+  llvm::cl::ExpansionContext ECtx(A, llvm::cl::TokenizeGNUCommandLine);
   if (llvm::Error Err = ECtx.expandResponseFiles(ArgV)) {
     llvm::errs() << toString(std::move(Err)) << '\n';
     return 1;
@@ -295,16 +293,14 @@ int clang_main(int Argc, char **Argv, const llvm::ToolContext &ToolContext) {
 
   bool ClangCLMode = IsClangCL(DriverMode);
 
-  auto VFS = llvm::vfs::getRealFileSystem();
-
-  if (llvm::Error Err = expandResponseFiles(Args, ClangCLMode, A, VFS.get())) {
+  if (llvm::Error Err = expandResponseFiles(Args, ClangCLMode, A)) {
     llvm::errs() << toString(std::move(Err)) << '\n';
     return 1;
   }
 
   // Handle -cc1 integrated tools.
   if (Args.size() >= 2 && StringRef(Args[1]).starts_with("-cc1"))
-    return ExecuteCC1Tool(Args, ToolContext, VFS);
+    return ExecuteCC1Tool(Args, ToolContext);
 
   // Handle options that need handling before the real command line parsing in
   // Driver::BuildCompilation()
@@ -386,6 +382,7 @@ int clang_main(int Argc, char **Argv, const llvm::ToolContext &ToolContext) {
         Diags.takeClient(), std::move(SerializedConsumer)));
   }
 
+  auto VFS = llvm::vfs::getRealFileSystem();
   ProcessWarningOptions(Diags, *DiagOpts, *VFS, /*ReportDiags=*/false);
 
   Driver TheDriver(Path, llvm::sys::getDefaultTargetTriple(), Diags,
@@ -405,10 +402,10 @@ int clang_main(int Argc, char **Argv, const llvm::ToolContext &ToolContext) {
   if (!SetBackdoorDriverOutputsFromEnvVars(TheDriver))
     return 1;
 
-  auto ExecuteCC1WithContext = [&ToolContext,
-                                &VFS](SmallVectorImpl<const char *> &ArgV) {
-    return ExecuteCC1Tool(ArgV, ToolContext, VFS);
-  };
+  auto ExecuteCC1WithContext =
+      [&ToolContext](SmallVectorImpl<const char *> &ArgV) {
+        return ExecuteCC1Tool(ArgV, ToolContext);
+      };
   if (!UseNewCC1Process) {
     TheDriver.CC1Main = ExecuteCC1WithContext;
     // Ensure the CC1Command actually catches cc1 crashes
diff --git a/clang/tools/libclang/CDependencies.cpp b/clang/tools/libclang/CDependencies.cpp
index 26c8b92435e48..6f765c281c07d 100644
--- a/clang/tools/libclang/CDependencies.cpp
+++ b/clang/tools/libclang/CDependencies.cpp
@@ -856,14 +856,11 @@ enum CXErrorCode clang_experimental_DependencyScanner_generateReproducer(
   for (const Command &BuildCommand : TU.Commands)
     PrintArguments(ScriptOS, BuildCommand.Arguments);
 
-  auto RealFS = llvm::vfs::getRealFileSystem();
-  RealFS->setCurrentWorkingDirectory(*Opts.WorkingDirectory);
-
   SmallString<128> VFSCachePath = FileCachePath;
   llvm::sys::path::append(VFSCachePath, "vfs");
   std::string VFSCachePathStr = VFSCachePath.str().str();
   llvm::FileCollector FileCollector(VFSCachePathStr,
-                                    /*OverlayRoot=*/VFSCachePathStr, RealFS);
+                                    /*OverlayRoot=*/VFSCachePathStr);
   for (const auto &FileDep : TU.FileDeps) {
     FileCollector.addFile(FileDep);
   }
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index ee87cd66b308b..a3d9340a2db73 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -4243,14 +4243,13 @@ enum CXErrorCode clang_createTranslationUnit2(CXIndex CIdx,
   FileSystemOptions FileSystemOpts;
   HeaderSearchOptions HSOpts;
 
-  auto VFS = llvm::vfs::getRealFileSystem();
-
   auto DiagOpts = std::make_shared<DiagnosticOptions>();
   IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-      CompilerInstance::createDiagnostics(*VFS, *DiagOpts);
+      CompilerInstance::createDiagnostics(*llvm::vfs::getRealFileSystem(),
+                                          *DiagOpts);
   std::unique_ptr<ASTUnit> AU = ASTUnit::LoadFromASTFile(
       ast_filename, CXXIdx->getPCHContainerOperations()->getRawReader(),
-      ASTUnit::LoadEverything, VFS, DiagOpts, Diags, FileSystemOpts, HSOpts,
+      ASTUnit::LoadEverything, DiagOpts, Diags, FileSystemOpts, HSOpts,
       /*LangOpts=*/nullptr, CXXIdx->getOnlyLocalDecls(), CaptureDiagsKind::All,
       /*AllowASTWithCompilerErrors=*/true,
       /*UserFilesAreVolatile=*/true);
diff --git a/clang/unittests/AST/ExternalASTSourceTest.cpp b/clang/unittests/AST/ExternalASTSourceTest.cpp
index 98d708707bc99..11715bb8ce7cd 100644
--- a/clang/unittests/AST/ExternalASTSourceTest.cpp
+++ b/clang/unittests/AST/ExternalASTSourceTest.cpp
@@ -57,8 +57,7 @@ bool testExternalASTSource(ExternalASTSource *Source, StringRef FileContents) {
   CompilerInvocation::CreateFromArgs(*Invocation, Args, *InvocationDiags);
 
   CompilerInstance Compiler(std::move(Invocation));
-  Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestFrontendAction Action(Source);
   return Compiler.ExecuteAction(Action);
diff --git a/clang/unittests/CodeGen/TestCompiler.h b/clang/unittests/CodeGen/TestCompiler.h
index 1dec035f185c7..a6fec7fb0945d 100644
--- a/clang/unittests/CodeGen/TestCompiler.h
+++ b/clang/unittests/CodeGen/TestCompiler.h
@@ -36,8 +36,7 @@ struct TestCompiler {
                clang::CodeGenOptions CGO = clang::CodeGenOptions()) {
     compiler.getLangOpts() = LO;
     compiler.getCodeGenOpts() = CGO;
-    compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-    compiler.createDiagnostics();
+    compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
     std::string TrStr = llvm::Triple::normalize(llvm::sys::getProcessTriple());
     llvm::Triple Tr(TrStr);
@@ -52,7 +51,7 @@ struct TestCompiler {
     PtrSize = TInfo.getPointerWidth(clang::LangAS::Default) / 8;
 
     compiler.createFileManager();
-    compiler.createSourceManager();
+    compiler.createSourceManager(compiler.getFileManager());
     compiler.createPreprocessor(clang::TU_Prefix);
 
     compiler.createASTContext();
diff --git a/clang/unittests/Driver/ToolChainTest.cpp b/clang/unittests/Driver/ToolChainTest.cpp
index 56a961370c0be..670090a01b0d3 100644
--- a/clang/unittests/Driver/ToolChainTest.cpp
+++ b/clang/unittests/Driver/ToolChainTest.cpp
@@ -579,8 +579,7 @@ TEST(CompilerInvocation, SplitSwarfSingleCrash) {
 
 TEST(ToolChainTest, UEFICallingConventionTest) {
   clang::CompilerInstance compiler;
-  compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   std::string TrStr = "x86_64-unknown-uefi";
   llvm::Triple Tr(TrStr);
diff --git a/clang/unittests/Frontend/ASTUnitTest.cpp b/clang/unittests/Frontend/ASTUnitTest.cpp
index 268dab2b169a3..afa64b5e90a6d 100644
--- a/clang/unittests/Frontend/ASTUnitTest.cpp
+++ b/clang/unittests/Frontend/ASTUnitTest.cpp
@@ -97,8 +97,7 @@ TEST_F(ASTUnitTest, SaveLoadPreservesLangOptionsInPrintingPolicy) {
 
   std::unique_ptr<ASTUnit> AU = ASTUnit::LoadFromASTFile(
       ASTFileName, PCHContainerOps->getRawReader(), ASTUnit::LoadEverything,
-      llvm::vfs::getRealFileSystem(), DiagOpts, Diags, FileSystemOptions(),
-      HSOpts);
+      DiagOpts, Diags, FileSystemOptions(), HSOpts);
 
   if (!AU)
     FAIL() << "failed to load ASTUnit";
diff --git a/clang/unittests/Frontend/CodeGenActionTest.cpp b/clang/unittests/Frontend/CodeGenActionTest.cpp
index 182afdc7ea313..b2792c44ba5fe 100644
--- a/clang/unittests/Frontend/CodeGenActionTest.cpp
+++ b/clang/unittests/Frontend/CodeGenActionTest.cpp
@@ -52,8 +52,7 @@ TEST(CodeGenTest, TestNullCodeGen) {
   Invocation->getFrontendOpts().ProgramAction = EmitLLVM;
   Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance Compiler(std::move(Invocation));
-  Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
   EXPECT_TRUE(Compiler.hasDiagnostics());
 
   std::unique_ptr<FrontendAction> Act(new NullCodeGenAction);
@@ -70,8 +69,7 @@ TEST(CodeGenTest, CodeGenFromIRMemBuffer) {
   Invocation->getFrontendOpts().ProgramAction = frontend::EmitLLVMOnly;
   Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance Compiler(std::move(Invocation));
-  Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
   EXPECT_TRUE(Compiler.hasDiagnostics());
 
   EmitLLVMOnlyAction Action;
diff --git a/clang/unittests/Frontend/CompilerInstanceTest.cpp b/clang/unittests/Frontend/CompilerInstanceTest.cpp
index e0f228668b884..459a3864887e1 100644
--- a/clang/unittests/Frontend/CompilerInstanceTest.cpp
+++ b/clang/unittests/Frontend/CompilerInstanceTest.cpp
@@ -33,7 +33,7 @@ TEST(CompilerInstance, DefaultVFSOverlayFromInvocation) {
 
   SmallString<256> CurrentPath;
   sys::fs::current_path(CurrentPath);
-  sys::path::make_absolute(CurrentPath, FileName);
+  sys::fs::make_absolute(CurrentPath, FileName);
 
   // Mount the VFS file itself on the path 'virtual.file'. Makes this test
   // a bit shorter than creating a new dummy file just for this purpose.
@@ -72,7 +72,6 @@ TEST(CompilerInstance, DefaultVFSOverlayFromInvocation) {
   // in the CompilerInvocation (as we don't explicitly set our own).
   CompilerInstance Instance(std::move(CInvok));
   Instance.setDiagnostics(Diags.get());
-  Instance.createVirtualFileSystem();
   Instance.createFileManager();
 
   // Check if the virtual file exists which means that our VFS is used by the
@@ -136,9 +135,8 @@ TEST(CompilerInstance, MultipleInputsCleansFileIDs) {
   ASSERT_TRUE(CInvok) << "could not create compiler invocation";
 
   CompilerInstance Instance(std::move(CInvok));
-  Instance.setVirtualFileSystem(VFS);
   Instance.setDiagnostics(Diags.get());
-  Instance.createFileManager();
+  Instance.createFileManager(VFS);
 
   // Run once for `a.cc` and then for `a.h`. This makes sure we get the same
   // file ID for `b.h` in the second run as `a.h` from first run.
diff --git a/clang/unittests/Frontend/FrontendActionTest.cpp b/clang/unittests/Frontend/FrontendActionTest.cpp
index 125940b44170c..4e040783c923e 100644
--- a/clang/unittests/Frontend/FrontendActionTest.cpp
+++ b/clang/unittests/Frontend/FrontendActionTest.cpp
@@ -91,8 +91,7 @@ TEST(ASTFrontendAction, Sanity) {
   invocation->getFrontendOpts().ProgramAction = frontend::ParseSyntaxOnly;
   invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance compiler(std::move(invocation));
-  compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestASTFrontendAction test_action;
   ASSERT_TRUE(compiler.ExecuteAction(test_action));
@@ -111,8 +110,7 @@ TEST(ASTFrontendAction, IncrementalParsing) {
   invocation->getFrontendOpts().ProgramAction = frontend::ParseSyntaxOnly;
   invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance compiler(std::move(invocation));
-  compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestASTFrontendAction test_action(/*enableIncrementalProcessing=*/true);
   ASSERT_TRUE(compiler.ExecuteAction(test_action));
@@ -138,8 +136,7 @@ TEST(ASTFrontendAction, LateTemplateIncrementalParsing) {
   invocation->getFrontendOpts().ProgramAction = frontend::ParseSyntaxOnly;
   invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance compiler(std::move(invocation));
-  compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  compiler.createDiagnostics();
+  compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestASTFrontendAction test_action(/*enableIncrementalProcessing=*/true,
                                     /*actOnEndOfTranslationUnit=*/true);
@@ -184,8 +181,7 @@ TEST(PreprocessorFrontendAction, EndSourceFile) {
   Invocation->getFrontendOpts().ProgramAction = frontend::ParseSyntaxOnly;
   Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance Compiler(std::move(Invocation));
-  Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   TestPPCallbacks *Callbacks = new TestPPCallbacks;
   TestPPCallbacksFrontendAction TestAction(Callbacks);
@@ -246,8 +242,8 @@ TEST(ASTFrontendAction, ExternalSemaSource) {
   Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
   CompilerInstance Compiler(std::move(Invocation));
   auto *TDC = new TypoDiagnosticConsumer;
-  Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  Compiler.createDiagnostics(TDC, /*ShouldOwnClient=*/true);
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem(), TDC,
+                             /*ShouldOwnClient=*/true);
   Compiler.setExternalSemaSource(new TypoExternalSemaSource(Compiler));
 
   SyntaxOnlyAction TestAction;
@@ -278,8 +274,7 @@ TEST(GeneratePCHFrontendAction, CacheGeneratedPCH) {
     Invocation->getFrontendOpts().ProgramAction = frontend::GeneratePCH;
     Invocation->getTargetOpts().Triple = "x86_64-apple-darwin19.0.0";
     CompilerInstance Compiler(std::move(Invocation));
-    Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-    Compiler.createDiagnostics();
+    Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
     GeneratePCHAction TestAction;
     ASSERT_TRUE(Compiler.ExecuteAction(TestAction));
diff --git a/clang/unittests/Frontend/OutputStreamTest.cpp b/clang/unittests/Frontend/OutputStreamTest.cpp
index 9e288f86351ca..dfb5a544cb88a 100644
--- a/clang/unittests/Frontend/OutputStreamTest.cpp
+++ b/clang/unittests/Frontend/OutputStreamTest.cpp
@@ -38,8 +38,7 @@ TEST(FrontendOutputTests, TestOutputStream) {
       new raw_svector_ostream(IRBuffer));
 
   Compiler.setOutputStream(std::move(IRStream));
-  Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  Compiler.createDiagnostics();
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem());
 
   bool Success = ExecuteCompilerInvocation(&Compiler);
   EXPECT_TRUE(Success);
@@ -63,8 +62,8 @@ TEST(FrontendOutputTests, TestVerboseOutputStreamShared) {
 
   Compiler.setOutputStream(std::make_unique<raw_null_ostream>());
   DiagnosticOptions DiagOpts;
-  Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
-  Compiler.createDiagnostics(new TextDiagnosticPrinter(llvm::nulls(), DiagOpts),
+  Compiler.createDiagnostics(*llvm::vfs::getRealFileSystem(),
+                             new TextDiagnosticPrinter(llvm::nulls(), DiagOpts),
                              true);
   Compiler.setVerboseOutputStream(VerboseStream);
 
@@ -93,8 +92,8 @@ TEST(FrontendOutputTests, TestVerboseOutputStreamOwned) {
 
     Compiler.setOutputStream(std::make_unique<raw_null_ostream>());
     DiagnosticOptions DiagOpts;
-    Compiler.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
     Compiler.createDiagnostics(
+        *llvm::vfs::getRealFileSystem(),
         new TextDiagnosticPrinter(llvm::nulls(), DiagOpts), true);
     Compiler.setVerboseOutputStream(std::move(VerboseStream));
 
diff --git a/clang/unittests/Serialization/ForceCheckFileInputTest.cpp b/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
index 70e9fad858767..970eeef3c953e 100644
--- a/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
+++ b/clang/unittests/Serialization/ForceCheckFileInputTest.cpp
@@ -91,8 +91,10 @@ export int aa = 43;
 
     Instance.getFrontendOpts().OutputFile = BMIPath;
 
-    Instance.createVirtualFileSystem(CIOpts.VFS);
-    Instance.createFileManager();
+    if (auto VFSWithRemapping = createVFSFromCompilerInvocation(
+            Instance.getInvocation(), Instance.getDiagnostics(), CIOpts.VFS))
+      CIOpts.VFS = VFSWithRemapping;
+    Instance.createFileManager(CIOpts.VFS);
 
     Instance.getHeaderSearchOpts().ValidateASTInputFilesContent = true;
 
@@ -121,9 +123,8 @@ export int aa = 43;
     CompilerInstance Clang(std::move(Invocation));
 
     Clang.setDiagnostics(Diags.get());
-    Clang.createVirtualFileSystem(CIOpts.VFS);
-    Clang.createFileManager();
-    Clang.createSourceManager();
+    FileManager *FM = Clang.createFileManager(CIOpts.VFS);
+    Clang.createSourceManager(*FM);
 
     EXPECT_TRUE(Clang.createTarget());
     Clang.createPreprocessor(TU_Complete);
diff --git a/clang/unittests/Serialization/ModuleCacheTest.cpp b/clang/unittests/Serialization/ModuleCacheTest.cpp
index dbf2076b40396..de6e13a738cb8 100644
--- a/clang/unittests/Serialization/ModuleCacheTest.cpp
+++ b/clang/unittests/Serialization/ModuleCacheTest.cpp
@@ -121,7 +121,6 @@ TEST_F(ModuleCacheTest, CachedModuleNewPath) {
       createInvocationAndEnableFree(Args, CIOpts);
   ASSERT_TRUE(Invocation);
   CompilerInstance Instance(std::move(Invocation));
-  Instance.setVirtualFileSystem(CIOpts.VFS);
   Instance.setDiagnostics(Diags.get());
   SyntaxOnlyAction Action;
   ASSERT_TRUE(Instance.ExecuteAction(Action));
@@ -146,7 +145,6 @@ TEST_F(ModuleCacheTest, CachedModuleNewPath) {
   CompilerInstance Instance2(std::move(Invocation2),
                              Instance.getPCHContainerOperations(),
                              &Instance.getModuleCache());
-  Instance2.setVirtualFileSystem(CIOpts.VFS);
   Instance2.setDiagnostics(Diags.get());
   SyntaxOnlyAction Action2;
   ASSERT_FALSE(Instance2.ExecuteAction(Action2));
@@ -173,7 +171,6 @@ TEST_F(ModuleCacheTest, CachedModuleNewPathAllowErrors) {
       createInvocationAndEnableFree(Args, CIOpts);
   ASSERT_TRUE(Invocation);
   CompilerInstance Instance(std::move(Invocation));
-  Instance.setVirtualFileSystem(CIOpts.VFS);
   Instance.setDiagnostics(Diags.get());
   SyntaxOnlyAction Action;
   ASSERT_TRUE(Instance.ExecuteAction(Action));
@@ -192,7 +189,6 @@ TEST_F(ModuleCacheTest, CachedModuleNewPathAllowErrors) {
   CompilerInstance Instance2(std::move(Invocation2),
                              Instance.getPCHContainerOperations(),
                              &Instance.getModuleCache());
-  Instance2.setVirtualFileSystem(CIOpts.VFS);
   Instance2.setDiagnostics(Diags.get());
   SyntaxOnlyAction Action2;
   ASSERT_FALSE(Instance2.ExecuteAction(Action2));
diff --git a/clang/unittests/Serialization/NoCommentsTest.cpp b/clang/unittests/Serialization/NoCommentsTest.cpp
index f091e51e86c93..05efeef990d43 100644
--- a/clang/unittests/Serialization/NoCommentsTest.cpp
+++ b/clang/unittests/Serialization/NoCommentsTest.cpp
@@ -99,7 +99,6 @@ void foo() {}
   ASSERT_TRUE(Invocation);
 
   CompilerInstance Instance(std::move(Invocation));
-  Instance.createVirtualFileSystem(CIOpts.VFS);
   Instance.setDiagnostics(Diags.get());
   Instance.getFrontendOpts().OutputFile = CacheBMIPath;
   GenerateReducedModuleInterfaceAction Action;
diff --git a/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp b/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp
index 9f7ec8182f748..c43520f79b02c 100644
--- a/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp
+++ b/clang/unittests/Serialization/PreambleInNamedModulesTest.cpp
@@ -113,8 +113,12 @@ export using ::E;
 
   auto Clang = std::make_unique<CompilerInstance>(std::move(Invocation));
   Clang->setDiagnostics(Diags.get());
-  Clang->createVirtualFileSystem(VFS);
-  Clang->createFileManager();
+
+  if (auto VFSWithRemapping = createVFSFromCompilerInvocation(
+          Clang->getInvocation(), Clang->getDiagnostics(), VFS))
+    VFS = VFSWithRemapping;
+
+  Clang->createFileManager(VFS);
   EXPECT_TRUE(Clang->createTarget());
 
   Buffer.release();
diff --git a/clang/unittests/Support/TimeProfilerTest.cpp b/clang/unittests/Support/TimeProfilerTest.cpp
index d85743da31358..85d36b5d21423 100644
--- a/clang/unittests/Support/TimeProfilerTest.cpp
+++ b/clang/unittests/Support/TimeProfilerTest.cpp
@@ -53,6 +53,8 @@ bool compileFromString(StringRef Code, StringRef Standard, StringRef File,
     FS->addFile(Header.getKey(), 0,
                 MemoryBuffer::getMemBuffer(Header.getValue()));
   }
+  llvm::IntrusiveRefCntPtr<FileManager> Files(
+      new FileManager(FileSystemOptions(), FS));
 
   auto Invocation = std::make_shared<CompilerInvocation>();
   std::vector<const char *> Args = {Standard.data(), File.data()};
@@ -62,9 +64,8 @@ bool compileFromString(StringRef Code, StringRef Standard, StringRef File,
   CompilerInvocation::CreateFromArgs(*Invocation, Args, *InvocationDiags);
 
   CompilerInstance Compiler(std::move(Invocation));
-  Compiler.setVirtualFileSystem(std::move(FS));
-  Compiler.createDiagnostics();
-  Compiler.createFileManager();
+  Compiler.createDiagnostics(Files->getVirtualFileSystem());
+  Compiler.setFileManager(Files.get());
 
   class TestFrontendAction : public ASTFrontendAction {
   private:
diff --git a/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp b/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp
index b2583441f1ecd..80d47658daafb 100644
--- a/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp
+++ b/clang/unittests/Tooling/DependencyScanning/DependencyScannerTest.cpp
@@ -65,11 +65,12 @@ class TestDependencyScanningAction : public tooling::ToolAction {
                               std::move(PCHContainerOps));
     Compiler.setFileManager(FileMgr);
 
-    Compiler.createDiagnostics(DiagConsumer, /*ShouldOwnClient=*/false);
+    Compiler.createDiagnostics(FileMgr->getVirtualFileSystem(), DiagConsumer,
+                               /*ShouldOwnClient=*/false);
     if (!Compiler.hasDiagnostics())
       return false;
 
-    Compiler.createSourceManager();
+    Compiler.createSourceManager(*FileMgr);
     Compiler.addDependencyCollector(std::make_shared<TestFileCollector>(
         Compiler.getInvocation().getDependencyOutputOpts(), Deps));
 
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index acb2a4dc0cd5e..f55d866435997 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -22,7 +22,6 @@
 #include "flang/Tools/TargetSetup.h"
 #include "flang/Version.inc"
 #include "clang/Basic/DiagnosticDriver.h"
-#include "clang/Basic/DiagnosticFrontend.h"
 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Driver/CommonArgs.h"
 #include "clang/Driver/Driver.h"
@@ -1216,7 +1215,7 @@ static bool parseOpenMPArgs(CompilerInvocation &res, llvm::opt::ArgList &args,
             clang::driver::options::OPT_fopenmp_host_ir_file_path)) {
       res.getLangOpts().OMPHostIRFile = arg->getValue();
       if (!llvm::sys::fs::exists(res.getLangOpts().OMPHostIRFile))
-        diags.Report(clang::diag::err_omp_host_ir_file_not_found)
+        diags.Report(clang::diag::err_drv_omp_host_ir_file_not_found)
             << res.getLangOpts().OMPHostIRFile;
     }
 
diff --git a/flang/lib/Frontend/FrontendActions.cpp b/flang/lib/Frontend/FrontendActions.cpp
index 692fbb1aea147..b5f4f9421f633 100644
--- a/flang/lib/Frontend/FrontendActions.cpp
+++ b/flang/lib/Frontend/FrontendActions.cpp
@@ -926,18 +926,20 @@ void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
     pgoOpt = llvm::PGOOptions(opts.InstrProfileOutput.empty()
                                   ? llvm::driver::getDefaultProfileGenName()
                                   : opts.InstrProfileOutput,
-                              "", "", opts.MemoryProfileUsePath,
+                              "", "", opts.MemoryProfileUsePath, nullptr,
                               llvm::PGOOptions::IRInstr,
                               llvm::PGOOptions::NoCSAction,
                               llvm::PGOOptions::ColdFuncOpt::Default, false,
                               /*PseudoProbeForProfiling=*/false, false);
   } else if (opts.hasProfileIRUse()) {
+    llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS =
+        llvm::vfs::getRealFileSystem();
     // -fprofile-use.
     auto CSAction = opts.hasProfileCSIRUse() ? llvm::PGOOptions::CSIRUse
                                              : llvm::PGOOptions::NoCSAction;
     pgoOpt = llvm::PGOOptions(
         opts.ProfileInstrumentUsePath, "", opts.ProfileRemappingFile,
-        opts.MemoryProfileUsePath, llvm::PGOOptions::IRUse, CSAction,
+        opts.MemoryProfileUsePath, VFS, llvm::PGOOptions::IRUse, CSAction,
         llvm::PGOOptions::ColdFuncOpt::Default, false);
   }
 
diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index 62d245734c288..dbebbbd38093e 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -2210,9 +2210,7 @@ class CommandObjectTargetModulesDumpClangPCMInfo : public CommandObjectParsed {
 
     const char *clang_args[] = {"clang", pcm_path};
     clang::CompilerInstance compiler(clang::createInvocation(clang_args));
-    compiler.setVirtualFileSystem(
-        FileSystem::Instance().GetVirtualFileSystem());
-    compiler.createDiagnostics();
+    compiler.createDiagnostics(*FileSystem::Instance().GetVirtualFileSystem());
 
     // Pass empty deleter to not attempt to free memory that was allocated
     // outside of the current scope, possibly statically.
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
index 2f267fa0b724b..8f88e4a2f1726 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
@@ -801,16 +801,14 @@ ClangExpressionParser::ClangExpressionParser(
   m_compiler = std::make_unique<CompilerInstance>();
 
   // Make sure clang uses the same VFS as LLDB.
-  m_compiler->setVirtualFileSystem(
-      FileSystem::Instance().GetVirtualFileSystem());
-  m_compiler->createFileManager();
+  m_compiler->createFileManager(FileSystem::Instance().GetVirtualFileSystem());
 
   // 2. Configure the compiler with a set of default options that are
   // appropriate for most situations.
   SetupTargetOpts(*m_compiler, *target_sp);
 
   // 3. Create and install the target on the compiler.
-  m_compiler->createDiagnostics();
+  m_compiler->createDiagnostics(m_compiler->getVirtualFileSystem());
   // Limit the number of error diagnostics we emit.
   // A value of 0 means no limit for both LLDB and Clang.
   m_compiler->getDiagnostics().setErrorLimit(target_sp->GetExprErrorLimit());
@@ -873,7 +871,7 @@ ClangExpressionParser::ClangExpressionParser(
   // 6. Set up the source management objects inside the compiler
   m_compiler->createFileManager();
   if (!m_compiler->hasSourceManager())
-    m_compiler->createSourceManager();
+    m_compiler->createSourceManager(m_compiler->getFileManager());
   m_compiler->createPreprocessor(TU_Complete);
 
   switch (expr.Language().AsLanguageType()) {
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
index 14f08d3039b81..e314ffb1260dd 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
@@ -745,8 +745,7 @@ ClangModulesDeclVendor::Create(Target &target) {
   auto instance = std::make_unique<clang::CompilerInstance>(invocation);
 
   // Make sure clang uses the same VFS as LLDB.
-  instance->setVirtualFileSystem(FileSystem::Instance().GetVirtualFileSystem());
-  instance->createFileManager();
+  instance->createFileManager(FileSystem::Instance().GetVirtualFileSystem());
   instance->setDiagnostics(diagnostics_engine.get());
 
   std::unique_ptr<clang::FrontendAction> action(new clang::SyntaxOnlyAction);
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ModuleDependencyCollector.h b/lldb/source/Plugins/ExpressionParser/Clang/ModuleDependencyCollector.h
index dcba0d9c34962..4fe727460fdb9 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ModuleDependencyCollector.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ModuleDependencyCollector.h
@@ -19,8 +19,8 @@ class ModuleDependencyCollectorAdaptor
 public:
   ModuleDependencyCollectorAdaptor(
       std::shared_ptr<llvm::FileCollectorBase> file_collector)
-      : clang::ModuleDependencyCollector("", llvm::vfs::getRealFileSystem()),
-        m_file_collector(file_collector) {}
+      : clang::ModuleDependencyCollector(""), m_file_collector(file_collector) {
+  }
 
   void addFile(llvm::StringRef Filename,
                llvm::StringRef FileDst = {}) override {
diff --git a/llvm/include/llvm/CodeGen/AsmPrinter.h b/llvm/include/llvm/CodeGen/AsmPrinter.h
index 0982820e69a35..dafe887bc0f3b 100644
--- a/llvm/include/llvm/CodeGen/AsmPrinter.h
+++ b/llvm/include/llvm/CodeGen/AsmPrinter.h
@@ -16,7 +16,6 @@
 #define LLVM_CODEGEN_ASMPRINTER_H
 
 #include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
@@ -89,10 +88,6 @@ namespace remarks {
 class RemarkStreamer;
 }
 
-namespace vfs {
-class FileSystem;
-}
-
 /// This class is intended to be used as a driving class for all asm writers.
 class LLVM_ABI AsmPrinter : public MachineFunctionPass {
 public:
@@ -111,9 +106,6 @@ class LLVM_ABI AsmPrinter : public MachineFunctionPass {
   /// generating (such as the current section etc).
   std::unique_ptr<MCStreamer> OutStreamer;
 
-  /// The VFS to resolve asm include directives.
-  IntrusiveRefCntPtr<vfs::FileSystem> VFS;
-
   /// The current machine function.
   MachineFunction *MF = nullptr;
 
diff --git a/llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h b/llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h
index 21f4a9ef313c0..206ad4a4ef85f 100644
--- a/llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h
+++ b/llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h
@@ -38,10 +38,6 @@ class Loop;
 class LoopAnalysis;
 class LoopInfo;
 
-namespace vfs {
-class FileSystem;
-} // namespace vfs
-
 /// Move the instruction after an InsertPoint to the beginning of another
 /// BasicBlock.
 ///
@@ -1350,7 +1346,7 @@ class OpenMPIRBuilder {
   /// any.
   LLVM_ABI static TargetRegionEntryInfo
   getTargetEntryUniqueInfo(FileIdentifierInfoCallbackTy CallBack,
-                           vfs::FileSystem &VFS, StringRef ParentName = "");
+                           StringRef ParentName = "");
 
   /// Enum class for the RedctionGen CallBack type to be used.
   enum class ReductionGenCBKind { Clang, MLIR };
@@ -3495,8 +3491,7 @@ class OpenMPIRBuilder {
   /// \param HostFilePath The path to the host IR file,
   /// used to load in offload metadata for the device, allowing host and device
   /// to maintain the same metadata mapping.
-  LLVM_ABI void loadOffloadInfoMetadata(vfs::FileSystem &VFS,
-                                        StringRef HostFilePath);
+  LLVM_ABI void loadOffloadInfoMetadata(StringRef HostFilePath);
 
   /// Gets (if variable with the given name already exist) or creates
   /// internal global variable with the specified Name. The created variable has
diff --git a/llvm/include/llvm/Passes/PassBuilder.h b/llvm/include/llvm/Passes/PassBuilder.h
index 1567307ed14bd..e60a04067d102 100644
--- a/llvm/include/llvm/Passes/PassBuilder.h
+++ b/llvm/include/llvm/Passes/PassBuilder.h
@@ -36,6 +36,10 @@ class StringRef;
 class AAManager;
 class TargetMachine;
 class ModuleSummaryIndex;
+template <typename T> class IntrusiveRefCntPtr;
+namespace vfs {
+class FileSystem;
+} // namespace vfs
 
 /// Tunable parameters for passes in the default pipelines.
 class PipelineTuningOptions {
@@ -109,7 +113,6 @@ class PassBuilder {
   PipelineTuningOptions PTO;
   std::optional<PGOOptions> PGOOpt;
   PassInstrumentationCallbacks *PIC;
-  IntrusiveRefCntPtr<vfs::FileSystem> FS;
 
 public:
   /// A struct to capture parsed pass pipeline names.
@@ -129,8 +132,7 @@ class PassBuilder {
       TargetMachine *TM = nullptr,
       PipelineTuningOptions PTO = PipelineTuningOptions(),
       std::optional<PGOOptions> PGOOpt = std::nullopt,
-      PassInstrumentationCallbacks *PIC = nullptr,
-      IntrusiveRefCntPtr<vfs::FileSystem> FS = vfs::getRealFileSystem());
+      PassInstrumentationCallbacks *PIC = nullptr);
 
   /// Cross register the analysis managers through their proxies.
   ///
@@ -632,7 +634,8 @@ class PassBuilder {
                                        bool RunProfileGen, bool IsCS,
                                        bool AtomicCounterUpdate,
                                        std::string ProfileFile,
-                                       std::string ProfileRemappingFile);
+                                       std::string ProfileRemappingFile,
+                                       IntrusiveRefCntPtr<vfs::FileSystem> FS);
 
   /// Returns PIC. External libraries can use this to register pass
   /// instrumentation callbacks.
@@ -640,11 +643,6 @@ class PassBuilder {
     return PIC;
   }
 
-  /// Returns the virtual file system.
-  IntrusiveRefCntPtr<vfs::FileSystem> getVirtualFileSystemPtr() const {
-    return FS;
-  }
-
   // Invoke the callbacks registered for the various extension points.
   // Custom pipelines should use these to invoke the callbacks registered
   // by TargetMachines and other clients.
@@ -776,7 +774,8 @@ class PassBuilder {
   void addPGOInstrPasses(ModulePassManager &MPM, OptimizationLevel Level,
                          bool RunProfileGen, bool IsCS,
                          bool AtomicCounterUpdate, std::string ProfileFile,
-                         std::string ProfileRemappingFile);
+                         std::string ProfileRemappingFile,
+                         IntrusiveRefCntPtr<vfs::FileSystem> FS);
   void addPostPGOLoopRotation(ModulePassManager &MPM, OptimizationLevel Level);
 
   bool isInstrumentedPGOUse() const;
diff --git a/llvm/include/llvm/Support/CommandLine.h b/llvm/include/llvm/Support/CommandLine.h
index b81df756247c9..ca725b8ac8712 100644
--- a/llvm/include/llvm/Support/CommandLine.h
+++ b/llvm/include/llvm/Support/CommandLine.h
@@ -69,7 +69,6 @@ namespace cl {
 LLVM_ABI bool ParseCommandLineOptions(int argc, const char *const *argv,
                                       StringRef Overview = "",
                                       raw_ostream *Errs = nullptr,
-                                      vfs::FileSystem *VFS = nullptr,
                                       const char *EnvVar = nullptr,
                                       bool LongOptionsUseDoubleDash = false);
 
@@ -2193,8 +2192,7 @@ class ExpansionContext {
                                  SmallVectorImpl<const char *> &NewArgv);
 
 public:
-  LLVM_ABI ExpansionContext(BumpPtrAllocator &A, TokenizerCallback T,
-                            vfs::FileSystem *FS = nullptr);
+  LLVM_ABI ExpansionContext(BumpPtrAllocator &A, TokenizerCallback T);
 
   ExpansionContext &setMarkEOLs(bool X) {
     MarkEOLs = X;
diff --git a/llvm/include/llvm/Support/FileCollector.h b/llvm/include/llvm/Support/FileCollector.h
index 9fa11ba362241..b00bf3174e654 100644
--- a/llvm/include/llvm/Support/FileCollector.h
+++ b/llvm/include/llvm/Support/FileCollector.h
@@ -81,28 +81,19 @@ class LLVM_ABI FileCollector : public FileCollectorBase {
     /// Canonicalize a pair of virtual and real paths.
     LLVM_ABI PathStorage canonicalize(StringRef SrcPath);
 
-    /// Return the underlying file system.
-    vfs::FileSystem &getFileSystem() const { return *VFS; };
-
-    explicit PathCanonicalizer(IntrusiveRefCntPtr<vfs::FileSystem> VFS)
-        : VFS(std::move(VFS)) {}
-
   private:
     /// Replace with a (mostly) real path, or don't modify. Resolves symlinks
     /// in the directory, using \a CachedDirs to avoid redundant lookups, but
     /// leaves the filename as a possible symlink.
     void updateWithRealPath(SmallVectorImpl<char> &Path);
 
-    IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS;
-
     StringMap<std::string> CachedDirs;
   };
 
   /// \p Root is the directory where collected files are will be stored.
   /// \p OverlayRoot is VFS mapping root.
   /// \p Root directory gets created in copyFiles unless it already exists.
-  FileCollector(std::string Root, std::string OverlayRoot,
-                IntrusiveRefCntPtr<vfs::FileSystem> VFS);
+  FileCollector(std::string Root, std::string OverlayRoot);
 
   /// Write the yaml mapping (for the VFS) to the given file.
   std::error_code writeMapping(StringRef MappingFile);
diff --git a/llvm/include/llvm/Support/FileSystem.h b/llvm/include/llvm/Support/FileSystem.h
index a8cea9d787510..3228dcec13a76 100644
--- a/llvm/include/llvm/Support/FileSystem.h
+++ b/llvm/include/llvm/Support/FileSystem.h
@@ -266,6 +266,18 @@ class file_status : public basic_file_status {
 /// @name Physical Operators
 /// @{
 
+/// Make \a path an absolute path.
+///
+/// Makes \a path absolute using the \a current_directory if it is not already.
+/// An empty \a path will result in the \a current_directory.
+///
+/// /absolute/path   => /absolute/path
+/// relative/../path => <current-directory>/relative/../path
+///
+/// @param path A path that is modified to be an absolute path.
+LLVM_ABI void make_absolute(const Twine &current_directory,
+                            SmallVectorImpl<char> &path);
+
 /// Make \a path an absolute path.
 ///
 /// Makes \a path absolute using the current directory if it is not already. An
diff --git a/llvm/include/llvm/Support/PGOOptions.h b/llvm/include/llvm/Support/PGOOptions.h
index fb1dc0cf4aa0a..6527a18258bf8 100644
--- a/llvm/include/llvm/Support/PGOOptions.h
+++ b/llvm/include/llvm/Support/PGOOptions.h
@@ -14,10 +14,16 @@
 #ifndef LLVM_SUPPORT_PGOOPTIONS_H
 #define LLVM_SUPPORT_PGOOPTIONS_H
 
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Error.h"
 
 namespace llvm {
+
+namespace vfs {
+class FileSystem;
+} // namespace vfs
+
 /// A struct capturing PGO tunables.
 struct PGOOptions {
   enum PGOAction { NoAction, IRInstr, IRUse, SampleUse };
@@ -25,7 +31,9 @@ struct PGOOptions {
   enum class ColdFuncOpt { Default, OptSize, MinSize, OptNone };
   LLVM_ABI PGOOptions(std::string ProfileFile, std::string CSProfileGenFile,
                       std::string ProfileRemappingFile,
-                      std::string MemoryProfile, PGOAction Action = NoAction,
+                      std::string MemoryProfile,
+                      IntrusiveRefCntPtr<vfs::FileSystem> FS,
+                      PGOAction Action = NoAction,
                       CSPGOAction CSAction = NoCSAction,
                       ColdFuncOpt ColdType = ColdFuncOpt::Default,
                       bool DebugInfoForProfiling = false,
@@ -45,6 +53,7 @@ struct PGOOptions {
   bool DebugInfoForProfiling;
   bool PseudoProbeForProfiling;
   bool AtomicCounterUpdate;
+  IntrusiveRefCntPtr<vfs::FileSystem> FS;
 };
 } // namespace llvm
 
diff --git a/llvm/include/llvm/Support/Path.h b/llvm/include/llvm/Support/Path.h
index a8e0f338ec203..0cb517146c04b 100644
--- a/llvm/include/llvm/Support/Path.h
+++ b/llvm/include/llvm/Support/Path.h
@@ -566,18 +566,6 @@ LLVM_ABI bool is_absolute_gnu(const Twine &path, Style style = Style::native);
 /// @result True if the path is relative, false if it is not.
 LLVM_ABI bool is_relative(const Twine &path, Style style = Style::native);
 
-/// Make \a path an absolute path.
-///
-/// Makes \a path absolute using the \a current_directory if it is not already.
-/// An empty \a path will result in the \a current_directory.
-///
-/// /absolute/path   => /absolute/path
-/// relative/../path => <current-directory>/relative/../path
-///
-/// @param path A path that is modified to be an absolute path.
-LLVM_ABI void make_absolute(const Twine &current_directory,
-                            SmallVectorImpl<char> &path);
-
 } // end namespace path
 } // end namespace sys
 } // end namespace llvm
diff --git a/llvm/include/llvm/Support/SourceMgr.h b/llvm/include/llvm/Support/SourceMgr.h
index 8320006ff5f6e..e4a27ade1f6bb 100644
--- a/llvm/include/llvm/Support/SourceMgr.h
+++ b/llvm/include/llvm/Support/SourceMgr.h
@@ -96,25 +96,22 @@ class SourceMgr {
   DiagHandlerTy DiagHandler = nullptr;
   void *DiagContext = nullptr;
 
-  // Optional file system for finding include files.
+  // Filesystem for finding includes, if not the real FS.
   IntrusiveRefCntPtr<vfs::FileSystem> FS;
 
   bool isValidBufferID(unsigned i) const { return i && i <= Buffers.size(); }
 
 public:
-  /// Create new source manager without support for include files.
   SourceMgr();
-  /// Create new source manager with the capability of finding include files
-  /// via the provided file system.
-  explicit SourceMgr(IntrusiveRefCntPtr<vfs::FileSystem> FS);
   SourceMgr(const SourceMgr &) = delete;
   SourceMgr &operator=(const SourceMgr &) = delete;
   SourceMgr(SourceMgr &&);
   SourceMgr &operator=(SourceMgr &&);
   ~SourceMgr();
 
-  IntrusiveRefCntPtr<vfs::FileSystem> getVirtualFileSystem() const;
-  void setVirtualFileSystem(IntrusiveRefCntPtr<vfs::FileSystem> FS);
+  /// Specify a \a vfs::FileSystem for finding includes.
+  explicit SourceMgr(IntrusiveRefCntPtr<vfs::FileSystem> FS);
+  void setFileSystem(IntrusiveRefCntPtr<vfs::FileSystem> FS);
 
   /// Return the include directories of this source manager.
   ArrayRef<std::string> getIncludeDirs() const { return IncludeDirectories; }
diff --git a/llvm/include/llvm/Support/VirtualFileSystem.h b/llvm/include/llvm/Support/VirtualFileSystem.h
index 9dfd122fb4cb3..64a2a3ea1609c 100644
--- a/llvm/include/llvm/Support/VirtualFileSystem.h
+++ b/llvm/include/llvm/Support/VirtualFileSystem.h
@@ -1164,10 +1164,14 @@ class LLVM_ABI RedirectingFileSystem
 };
 
 /// Collect all pairs of <virtual path, real path> entries from the
-/// \p VFS. This is used by the module dependency collector to forward
+/// \p YAMLFilePath. This is used by the module dependency collector to forward
 /// the entries into the reproducer output VFS YAML file.
-void collectVFSEntries(RedirectingFileSystem &VFS,
-                       SmallVectorImpl<YAMLVFSEntry> &CollectedEntries);
+LLVM_ABI void collectVFSFromYAML(
+    std::unique_ptr<llvm::MemoryBuffer> Buffer,
+    llvm::SourceMgr::DiagHandlerTy DiagHandler, StringRef YAMLFilePath,
+    SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
+    void *DiagContext = nullptr,
+    IntrusiveRefCntPtr<FileSystem> ExternalFS = getRealFileSystem());
 
 class YAMLVFSWriter {
   std::vector<YAMLVFSEntry> Mappings;
diff --git a/llvm/include/llvm/Transforms/Instrumentation/DataFlowSanitizer.h b/llvm/include/llvm/Transforms/Instrumentation/DataFlowSanitizer.h
index 9c9d6afe1872f..af3662e4a6565 100644
--- a/llvm/include/llvm/Transforms/Instrumentation/DataFlowSanitizer.h
+++ b/llvm/include/llvm/Transforms/Instrumentation/DataFlowSanitizer.h
@@ -10,7 +10,6 @@
 
 #include "llvm/IR/PassManager.h"
 #include "llvm/Support/Compiler.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include <string>
 #include <vector>
 
@@ -20,13 +19,11 @@ class Module;
 class DataFlowSanitizerPass : public PassInfoMixin<DataFlowSanitizerPass> {
 private:
   std::vector<std::string> ABIListFiles;
-  IntrusiveRefCntPtr<vfs::FileSystem> FS;
 
 public:
   DataFlowSanitizerPass(
-      const std::vector<std::string> &ABIListFiles = std::vector<std::string>(),
-      IntrusiveRefCntPtr<vfs::FileSystem> FS = vfs::getRealFileSystem())
-      : ABIListFiles(ABIListFiles), FS(std::move(FS)) {}
+      const std::vector<std::string> &ABIListFiles = std::vector<std::string>())
+      : ABIListFiles(ABIListFiles) {}
   LLVM_ABI PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
   static bool isRequired() { return true; }
 };
diff --git a/llvm/include/llvm/Transforms/Instrumentation/GCOVProfiler.h b/llvm/include/llvm/Transforms/Instrumentation/GCOVProfiler.h
index 43ef86b08517a..4d3ead29af0d2 100644
--- a/llvm/include/llvm/Transforms/Instrumentation/GCOVProfiler.h
+++ b/llvm/include/llvm/Transforms/Instrumentation/GCOVProfiler.h
@@ -14,22 +14,17 @@
 
 #include "llvm/IR/PassManager.h"
 #include "llvm/Support/Compiler.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Transforms/Utils/Instrumentation.h"
 
 namespace llvm {
 /// The gcov-style instrumentation pass
 class GCOVProfilerPass : public PassInfoMixin<GCOVProfilerPass> {
 public:
-  GCOVProfilerPass(
-      const GCOVOptions &Options = GCOVOptions::getDefault(),
-      IntrusiveRefCntPtr<vfs::FileSystem> VFS = vfs::getRealFileSystem())
-      : GCOVOpts(Options), VFS(std::move(VFS)) {}
+  GCOVProfilerPass(const GCOVOptions &Options = GCOVOptions::getDefault()) : GCOVOpts(Options) { }
   LLVM_ABI PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
 
 private:
   GCOVOptions GCOVOpts;
-  IntrusiveRefCntPtr<vfs::FileSystem> VFS;
 };
 
 } // namespace llvm
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 725d362ebe4c6..be0a1c3b0a0c2 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -117,7 +117,6 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/VCSRevision.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
 #include "llvm/Target/TargetMachine.h"
@@ -464,7 +463,6 @@ void AsmPrinter::getAnalysisUsage(AnalysisUsage &AU) const {
 }
 
 bool AsmPrinter::doInitialization(Module &M) {
-  VFS = vfs::getRealFileSystem();
   auto *MMIWP = getAnalysisIfAvailable<MachineModuleInfoWrapperPass>();
   MMI = MMIWP ? &MMIWP->getMMI() : nullptr;
   HasSplitStack = false;
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
index 8dd8b9da9c50c..c364ffc6eb8c1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
@@ -36,7 +36,6 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SourceMgr.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 using namespace llvm;
@@ -99,7 +98,6 @@ void AsmPrinter::emitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
   unsigned BufNum = addInlineAsmDiagBuffer(Str, LocMDNode);
   SourceMgr &SrcMgr = *MMI->getContext().getInlineSourceManager();
   SrcMgr.setIncludeDirs(MCOptions.IASSearchPaths);
-  SrcMgr.setVirtualFileSystem(VFS);
 
   std::unique_ptr<MCAsmParser> Parser(
       createMCAsmParser(SrcMgr, OutContext, *OutStreamer, *MAI, BufNum));
diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
index 3dbbe8dec26cd..840ca8364e218 100644
--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
@@ -51,7 +51,6 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
@@ -9849,19 +9848,17 @@ void OffloadEntriesInfoManager::getTargetRegionEntryFnName(
 
 TargetRegionEntryInfo
 OpenMPIRBuilder::getTargetEntryUniqueInfo(FileIdentifierInfoCallbackTy CallBack,
-                                          vfs::FileSystem &VFS,
                                           StringRef ParentName) {
   sys::fs::UniqueID ID(0xdeadf17e, 0);
   auto FileIDInfo = CallBack();
   uint64_t FileID = 0;
-  if (ErrorOr<vfs::Status> Status = VFS.status(std::get<0>(FileIDInfo))) {
-    ID = Status->getUniqueID();
-    FileID = Status->getUniqueID().getFile();
-  } else {
-    // If the inode ID could not be determined, create a hash value
-    // the current file name and use that as an ID.
+  std::error_code EC = sys::fs::getUniqueID(std::get<0>(FileIDInfo), ID);
+  // If the inode ID could not be determined, create a hash value
+  // the current file name and use that as an ID.
+  if (EC)
     FileID = hash_value(std::get<0>(FileIDInfo));
-  }
+  else
+    FileID = ID.getFile();
 
   return TargetRegionEntryInfo(ParentName, ID.getDevice(), FileID,
                                std::get<1>(FileIDInfo));
@@ -10086,12 +10083,11 @@ void OpenMPIRBuilder::loadOffloadInfoMetadata(Module &M) {
   }
 }
 
-void OpenMPIRBuilder::loadOffloadInfoMetadata(vfs::FileSystem &VFS,
-                                              StringRef HostFilePath) {
+void OpenMPIRBuilder::loadOffloadInfoMetadata(StringRef HostFilePath) {
   if (HostFilePath.empty())
     return;
 
-  auto Buf = VFS.getBufferForFile(HostFilePath);
+  auto Buf = MemoryBuffer::getFile(HostFilePath);
   if (std::error_code Err = Buf.getError()) {
     report_fatal_error(("error opening host file from host file path inside of "
                         "OpenMPIRBuilder: " +
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index 783514eae9011..5e8cd12fe040b 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -240,26 +240,27 @@ static void runNewPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
                            unsigned OptLevel, bool IsThinLTO,
                            ModuleSummaryIndex *ExportSummary,
                            const ModuleSummaryIndex *ImportSummary) {
+  auto FS = vfs::getRealFileSystem();
   std::optional<PGOOptions> PGOOpt;
   if (!Conf.SampleProfile.empty())
     PGOOpt = PGOOptions(Conf.SampleProfile, "", Conf.ProfileRemapping,
-                        /*MemoryProfile=*/"", PGOOptions::SampleUse,
+                        /*MemoryProfile=*/"", FS, PGOOptions::SampleUse,
                         PGOOptions::NoCSAction,
                         PGOOptions::ColdFuncOpt::Default, true);
   else if (Conf.RunCSIRInstr) {
     PGOOpt = PGOOptions("", Conf.CSIRProfile, Conf.ProfileRemapping,
-                        /*MemoryProfile=*/"", PGOOptions::IRUse,
+                        /*MemoryProfile=*/"", FS, PGOOptions::IRUse,
                         PGOOptions::CSIRInstr, PGOOptions::ColdFuncOpt::Default,
                         Conf.AddFSDiscriminator);
   } else if (!Conf.CSIRProfile.empty()) {
-    PGOOpt =
-        PGOOptions(Conf.CSIRProfile, "", Conf.ProfileRemapping,
-                   /*MemoryProfile=*/"", PGOOptions::IRUse, PGOOptions::CSIRUse,
-                   PGOOptions::ColdFuncOpt::Default, Conf.AddFSDiscriminator);
+    PGOOpt = PGOOptions(Conf.CSIRProfile, "", Conf.ProfileRemapping,
+                        /*MemoryProfile=*/"", FS, PGOOptions::IRUse,
+                        PGOOptions::CSIRUse, PGOOptions::ColdFuncOpt::Default,
+                        Conf.AddFSDiscriminator);
     NoPGOWarnMismatch = !Conf.PGOWarnMismatch;
   } else if (Conf.AddFSDiscriminator) {
-    PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", PGOOptions::NoAction,
-                        PGOOptions::NoCSAction,
+    PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", nullptr,
+                        PGOOptions::NoAction, PGOOptions::NoCSAction,
                         PGOOptions::ColdFuncOpt::Default, true);
   }
   TM->setPGOOption(PGOOpt);
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index b3f884481c643..8968ffa3a5c4b 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -479,9 +479,8 @@ class RequireAllMachineFunctionPropertiesPass
 
 PassBuilder::PassBuilder(TargetMachine *TM, PipelineTuningOptions PTO,
                          std::optional<PGOOptions> PGOOpt,
-                         PassInstrumentationCallbacks *PIC,
-                         IntrusiveRefCntPtr<vfs::FileSystem> FS)
-    : TM(TM), PTO(PTO), PGOOpt(PGOOpt), PIC(PIC), FS(std::move(FS)) {
+                         PassInstrumentationCallbacks *PIC)
+    : TM(TM), PTO(PTO), PGOOpt(PGOOpt), PIC(PIC) {
   if (TM)
     TM->registerPassBuilderCallbacks(*this);
   if (PIC) {
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 6e9c20fa7db2c..27718be09a0f0 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -856,7 +856,8 @@ void PassBuilder::addPGOInstrPasses(ModulePassManager &MPM,
                                     OptimizationLevel Level, bool RunProfileGen,
                                     bool IsCS, bool AtomicCounterUpdate,
                                     std::string ProfileFile,
-                                    std::string ProfileRemappingFile) {
+                                    std::string ProfileRemappingFile,
+                                    IntrusiveRefCntPtr<vfs::FileSystem> FS) {
   assert(Level != OptimizationLevel::O0 && "Not expecting O0 here!");
 
   if (!RunProfileGen) {
@@ -891,11 +892,10 @@ void PassBuilder::addPGOInstrPasses(ModulePassManager &MPM,
   MPM.addPass(InstrProfilingLoweringPass(Options, IsCS));
 }
 
-void PassBuilder::addPGOInstrPassesForO0(ModulePassManager &MPM,
-                                         bool RunProfileGen, bool IsCS,
-                                         bool AtomicCounterUpdate,
-                                         std::string ProfileFile,
-                                         std::string ProfileRemappingFile) {
+void PassBuilder::addPGOInstrPassesForO0(
+    ModulePassManager &MPM, bool RunProfileGen, bool IsCS,
+    bool AtomicCounterUpdate, std::string ProfileFile,
+    std::string ProfileRemappingFile, IntrusiveRefCntPtr<vfs::FileSystem> FS) {
   if (!RunProfileGen) {
     assert(!ProfileFile.empty() && "Profile use expecting a profile file!");
     MPM.addPass(
@@ -1141,8 +1141,8 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   if (LoadSampleProfile) {
     // Annotate sample profile right after early FPM to ensure freshness of
     // the debug info.
-    MPM.addPass(SampleProfileLoaderPass(
-        PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile, Phase, FS));
+    MPM.addPass(SampleProfileLoaderPass(PGOOpt->ProfileFile,
+                                        PGOOpt->ProfileRemappingFile, Phase));
     // Cache ProfileSummaryAnalysis once to avoid the potential need to insert
     // RequireAnalysisPass for PSI before subsequent non-module passes.
     MPM.addPass(RequireAnalysisPass<ProfileSummaryAnalysis, Module>());
@@ -1238,7 +1238,8 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
     addPGOInstrPasses(MPM, Level,
                       /*RunProfileGen=*/IsPGOInstrGen,
                       /*IsCS=*/false, PGOOpt->AtomicCounterUpdate,
-                      PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile);
+                      PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile,
+                      PGOOpt->FS);
   } else if (IsCtxProfGen || IsCtxProfUse) {
     MPM.addPass(PGOInstrumentationGen(PGOInstrumentationType::CTXPROF));
     // In pre-link, we just want the instrumented IR. We use the contextual
@@ -1261,10 +1262,10 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
     addPostPGOLoopRotation(MPM, Level);
     MPM.addPass(PGOCtxProfLoweringPass());
   } else if (IsColdFuncOnlyInstrGen) {
-    addPGOInstrPasses(MPM, Level, /* RunProfileGen */ true, /* IsCS */ false,
-                      /* AtomicCounterUpdate */ false,
-                      InstrumentColdFuncOnlyPath,
-                      /* ProfileRemappingFile */ "");
+    addPGOInstrPasses(
+        MPM, Level, /* RunProfileGen */ true, /* IsCS */ false,
+        /* AtomicCounterUpdate */ false, InstrumentColdFuncOnlyPath,
+        /* ProfileRemappingFile */ "", IntrusiveRefCntPtr<vfs::FileSystem>());
   }
 
   if (IsPGOInstrGen || IsPGOInstrUse || IsCtxProfGen)
@@ -1275,7 +1276,7 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
                                                EnableSampledInstr));
 
   if (IsMemprofUse)
-    MPM.addPass(MemProfUsePass(PGOOpt->MemoryProfile, FS));
+    MPM.addPass(MemProfUsePass(PGOOpt->MemoryProfile, PGOOpt->FS));
 
   if (PGOOpt && (PGOOpt->Action == PGOOptions::IRUse ||
                  PGOOpt->Action == PGOOptions::SampleUse))
@@ -1484,11 +1485,13 @@ PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
     if (PGOOpt->CSAction == PGOOptions::CSIRInstr)
       addPGOInstrPasses(MPM, Level, /*RunProfileGen=*/true,
                         /*IsCS=*/true, PGOOpt->AtomicCounterUpdate,
-                        PGOOpt->CSProfileGenFile, PGOOpt->ProfileRemappingFile);
+                        PGOOpt->CSProfileGenFile, PGOOpt->ProfileRemappingFile,
+                        PGOOpt->FS);
     else if (PGOOpt->CSAction == PGOOptions::CSIRUse)
       addPGOInstrPasses(MPM, Level, /*RunProfileGen=*/false,
                         /*IsCS=*/true, PGOOpt->AtomicCounterUpdate,
-                        PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile);
+                        PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile,
+                        PGOOpt->FS);
   }
 
   // Re-compute GlobalsAA here prior to function passes. This is particularly
@@ -2088,11 +2091,13 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
     if (PGOOpt->CSAction == PGOOptions::CSIRInstr)
       addPGOInstrPasses(MPM, Level, /*RunProfileGen=*/true,
                         /*IsCS=*/true, PGOOpt->AtomicCounterUpdate,
-                        PGOOpt->CSProfileGenFile, PGOOpt->ProfileRemappingFile);
+                        PGOOpt->CSProfileGenFile, PGOOpt->ProfileRemappingFile,
+                        PGOOpt->FS);
     else if (PGOOpt->CSAction == PGOOptions::CSIRUse)
       addPGOInstrPasses(MPM, Level, /*RunProfileGen=*/false,
                         /*IsCS=*/true, PGOOpt->AtomicCounterUpdate,
-                        PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile);
+                        PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile,
+                        PGOOpt->FS);
   }
 
   // Break up allocas
@@ -2254,7 +2259,7 @@ PassBuilder::buildO0DefaultPipeline(OptimizationLevel Level,
         MPM,
         /*RunProfileGen=*/(PGOOpt->Action == PGOOptions::IRInstr),
         /*IsCS=*/false, PGOOpt->AtomicCounterUpdate, PGOOpt->ProfileFile,
-        PGOOpt->ProfileRemappingFile);
+        PGOOpt->ProfileRemappingFile, PGOOpt->FS);
 
   // Instrument function entry and exit before all inlining.
   MPM.addPass(createModuleToFunctionPassAdaptor(
diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index 134df0df4cd99..8491633df97e8 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -188,7 +188,6 @@ class CommandLineParser {
 
   bool ParseCommandLineOptions(int argc, const char *const *argv,
                                StringRef Overview, raw_ostream *Errs = nullptr,
-                               vfs::FileSystem *VFS = nullptr,
                                bool LongOptionsUseDoubleDash = false);
 
   void forEachSubCommand(Option &Opt, function_ref<void(SubCommand &)> Action) {
@@ -1402,9 +1401,8 @@ bool cl::ExpandResponseFiles(StringSaver &Saver, TokenizerCallback Tokenizer,
   return true;
 }
 
-ExpansionContext::ExpansionContext(BumpPtrAllocator &A, TokenizerCallback T,
-                                   vfs::FileSystem *FS)
-    : Saver(A), Tokenizer(T), FS(FS ? FS : vfs::getRealFileSystem().get()) {}
+ExpansionContext::ExpansionContext(BumpPtrAllocator &A, TokenizerCallback T)
+    : Saver(A), Tokenizer(T), FS(vfs::getRealFileSystem().get()) {}
 
 bool ExpansionContext::findConfigFile(StringRef FileName,
                                       SmallVectorImpl<char> &FilePath) {
@@ -1463,7 +1461,7 @@ Error ExpansionContext::readConfigFile(StringRef CfgFile,
 static void initCommonOptions();
 bool cl::ParseCommandLineOptions(int argc, const char *const *argv,
                                  StringRef Overview, raw_ostream *Errs,
-                                 vfs::FileSystem *VFS, const char *EnvVar,
+                                 const char *EnvVar,
                                  bool LongOptionsUseDoubleDash) {
   initCommonOptions();
   SmallVector<const char *, 20> NewArgv;
@@ -1484,8 +1482,8 @@ bool cl::ParseCommandLineOptions(int argc, const char *const *argv,
   int NewArgc = static_cast<int>(NewArgv.size());
 
   // Parse all options.
-  return GlobalParser->ParseCommandLineOptions(
-      NewArgc, &NewArgv[0], Overview, Errs, VFS, LongOptionsUseDoubleDash);
+  return GlobalParser->ParseCommandLineOptions(NewArgc, &NewArgv[0], Overview,
+                                               Errs, LongOptionsUseDoubleDash);
 }
 
 /// Reset all options at least once, so that we can parse different options.
@@ -1505,17 +1503,17 @@ void CommandLineParser::ResetAllOptionOccurrences() {
   }
 }
 
-bool CommandLineParser::ParseCommandLineOptions(
-    int argc, const char *const *argv, StringRef Overview, raw_ostream *Errs,
-    vfs::FileSystem *VFS, bool LongOptionsUseDoubleDash) {
+bool CommandLineParser::ParseCommandLineOptions(int argc,
+                                                const char *const *argv,
+                                                StringRef Overview,
+                                                raw_ostream *Errs,
+                                                bool LongOptionsUseDoubleDash) {
   assert(hasOptions() && "No options specified!");
 
   ProgramOverview = Overview;
   bool IgnoreErrors = Errs;
   if (!Errs)
     Errs = &errs();
-  if (!VFS)
-    VFS = vfs::getRealFileSystem().get();
   bool ErrorParsing = false;
 
   // Expand response files.
@@ -1526,7 +1524,7 @@ bool CommandLineParser::ParseCommandLineOptions(
 #else
   auto Tokenize = cl::TokenizeGNUCommandLine;
 #endif
-  ExpansionContext ECtx(A, Tokenize, VFS);
+  ExpansionContext ECtx(A, Tokenize);
   if (Error Err = ECtx.expandResponseFiles(newArgv)) {
     *Errs << toString(std::move(Err)) << '\n';
     return false;
diff --git a/llvm/lib/Support/FileCollector.cpp b/llvm/lib/Support/FileCollector.cpp
index bf236171c1cf3..29436f85c2f23 100644
--- a/llvm/lib/Support/FileCollector.cpp
+++ b/llvm/lib/Support/FileCollector.cpp
@@ -49,9 +49,8 @@ static bool isCaseSensitivePath(StringRef Path) {
   return true;
 }
 
-FileCollector::FileCollector(std::string Root, std::string OverlayRoot,
-                             IntrusiveRefCntPtr<vfs::FileSystem> VFS)
-    : Root(Root), OverlayRoot(OverlayRoot), Canonicalizer(std::move(VFS)) {
+FileCollector::FileCollector(std::string Root, std::string OverlayRoot)
+    : Root(Root), OverlayRoot(OverlayRoot) {
   assert(sys::path::is_absolute(Root) && "Root not absolute");
   assert(sys::path::is_absolute(OverlayRoot) && "OverlayRoot not absolute");
 }
@@ -68,8 +67,9 @@ void FileCollector::PathCanonicalizer::updateWithRealPath(
   SmallString<256> RealPath;
   auto DirWithSymlink = CachedDirs.find(Directory);
   if (DirWithSymlink == CachedDirs.end()) {
-    // FIXME: What if there is nothing on disk?
-    if (VFS->getRealPath(Directory, RealPath))
+    // FIXME: Should this be a call to FileSystem::getRealpath(), in some
+    // cases? What if there is nothing on disk?
+    if (sys::fs::real_path(Directory, RealPath))
       return;
     CachedDirs[Directory] = std::string(RealPath);
   } else {
@@ -88,9 +88,9 @@ void FileCollector::PathCanonicalizer::updateWithRealPath(
 }
 
 /// Make Path absolute.
-static void makeAbsolute(vfs::FileSystem &VFS, SmallVectorImpl<char> &Path) {
+static void makeAbsolute(SmallVectorImpl<char> &Path) {
   // We need an absolute src path to append to the root.
-  VFS.makeAbsolute(Path);
+  sys::fs::make_absolute(Path);
 
   // Canonicalize src to a native path to avoid mixed separator styles.
   sys::path::native(Path);
@@ -105,7 +105,7 @@ FileCollector::PathCanonicalizer::PathStorage
 FileCollector::PathCanonicalizer::canonicalize(StringRef SrcPath) {
   PathStorage Paths;
   Paths.VirtualPath = SrcPath;
-  makeAbsolute(*VFS, Paths.VirtualPath);
+  makeAbsolute(Paths.VirtualPath);
 
   // If a ".." component is present after a symlink component, remove_dots may
   // lead to the wrong real destination path. Let the source be canonicalized
diff --git a/llvm/lib/Support/PGOOptions.cpp b/llvm/lib/Support/PGOOptions.cpp
index ecfb0ca33f16c..5981dff9e0946 100644
--- a/llvm/lib/Support/PGOOptions.cpp
+++ b/llvm/lib/Support/PGOOptions.cpp
@@ -13,7 +13,8 @@ using namespace llvm;
 
 PGOOptions::PGOOptions(std::string ProfileFile, std::string CSProfileGenFile,
                        std::string ProfileRemappingFile,
-                       std::string MemoryProfile, PGOAction Action,
+                       std::string MemoryProfile,
+                       IntrusiveRefCntPtr<vfs::FileSystem> FS, PGOAction Action,
                        CSPGOAction CSAction, ColdFuncOpt ColdType,
                        bool DebugInfoForProfiling, bool PseudoProbeForProfiling,
                        bool AtomicCounterUpdate)
@@ -23,7 +24,7 @@ PGOOptions::PGOOptions(std::string ProfileFile, std::string CSProfileGenFile,
       DebugInfoForProfiling(DebugInfoForProfiling ||
                             (Action == SampleUse && !PseudoProbeForProfiling)),
       PseudoProbeForProfiling(PseudoProbeForProfiling),
-      AtomicCounterUpdate(AtomicCounterUpdate) {
+      AtomicCounterUpdate(AtomicCounterUpdate), FS(std::move(FS)) {
   // Note, we do allow ProfileFile.empty() for Action=IRUse LTO can
   // callback with IRUse action without ProfileFile.
 
@@ -46,6 +47,10 @@ PGOOptions::PGOOptions(std::string ProfileFile, std::string CSProfileGenFile,
   assert(this->Action != NoAction || this->CSAction != NoCSAction ||
          !this->MemoryProfile.empty() || this->DebugInfoForProfiling ||
          this->PseudoProbeForProfiling);
+
+  // If we need to use the profile, the VFS cannot be nullptr.
+  assert(this->FS || !(this->Action == IRUse || this->CSAction == CSIRUse ||
+                       !this->MemoryProfile.empty()));
 }
 
 PGOOptions::PGOOptions(const PGOOptions &) = default;
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 3e066665f4155..761d29e960887 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -700,55 +700,6 @@ bool is_relative(const Twine &path, Style style) {
   return !is_absolute(path, style);
 }
 
-void make_absolute(const Twine &current_directory,
-                   SmallVectorImpl<char> &path) {
-  StringRef p(path.data(), path.size());
-
-  bool rootDirectory = has_root_directory(p);
-  bool rootName = has_root_name(p);
-
-  // Already absolute.
-  if ((rootName || is_style_posix(Style::native)) && rootDirectory)
-    return;
-
-  // All the following conditions will need the current directory.
-  SmallString<128> current_dir;
-  current_directory.toVector(current_dir);
-
-  // Relative path. Prepend the current directory.
-  if (!rootName && !rootDirectory) {
-    // Append path to the current directory.
-    append(current_dir, p);
-    // Set path to the result.
-    path.swap(current_dir);
-    return;
-  }
-
-  if (!rootName && rootDirectory) {
-    StringRef cdrn = root_name(current_dir);
-    SmallString<128> curDirRootName(cdrn.begin(), cdrn.end());
-    append(curDirRootName, p);
-    // Set path to the result.
-    path.swap(curDirRootName);
-    return;
-  }
-
-  if (rootName && !rootDirectory) {
-    StringRef pRootName = root_name(p);
-    StringRef bRootDirectory = root_directory(current_dir);
-    StringRef bRelativePath = relative_path(current_dir);
-    StringRef pRelativePath = relative_path(p);
-
-    SmallString<128> res;
-    append(res, pRootName, bRootDirectory, bRelativePath, pRelativePath);
-    path.swap(res);
-    return;
-  }
-
-  llvm_unreachable("All rootName and rootDirectory combinations should have "
-                   "occurred above!");
-}
-
 StringRef remove_leading_dotslash(StringRef Path, Style style) {
   // Remove leading "./" (or ".//" or "././" etc.)
   while (Path.size() > 2 && Path[0] == '.' && is_separator(Path[1], style)) {
@@ -952,6 +903,55 @@ getPotentiallyUniqueTempFileName(const Twine &Prefix, StringRef Suffix,
   return createTemporaryFile(Prefix, Suffix, Dummy, ResultPath, FS_Name);
 }
 
+void make_absolute(const Twine &current_directory,
+                   SmallVectorImpl<char> &path) {
+  StringRef p(path.data(), path.size());
+
+  bool rootDirectory = path::has_root_directory(p);
+  bool rootName = path::has_root_name(p);
+
+  // Already absolute.
+  if ((rootName || is_style_posix(Style::native)) && rootDirectory)
+    return;
+
+  // All of the following conditions will need the current directory.
+  SmallString<128> current_dir;
+  current_directory.toVector(current_dir);
+
+  // Relative path. Prepend the current directory.
+  if (!rootName && !rootDirectory) {
+    // Append path to the current directory.
+    path::append(current_dir, p);
+    // Set path to the result.
+    path.swap(current_dir);
+    return;
+  }
+
+  if (!rootName && rootDirectory) {
+    StringRef cdrn = path::root_name(current_dir);
+    SmallString<128> curDirRootName(cdrn.begin(), cdrn.end());
+    path::append(curDirRootName, p);
+    // Set path to the result.
+    path.swap(curDirRootName);
+    return;
+  }
+
+  if (rootName && !rootDirectory) {
+    StringRef pRootName      = path::root_name(p);
+    StringRef bRootDirectory = path::root_directory(current_dir);
+    StringRef bRelativePath  = path::relative_path(current_dir);
+    StringRef pRelativePath  = path::relative_path(p);
+
+    SmallString<128> res;
+    path::append(res, pRootName, bRootDirectory, bRelativePath, pRelativePath);
+    path.swap(res);
+    return;
+  }
+
+  llvm_unreachable("All rootName and rootDirectory combinations should have "
+                   "occurred above!");
+}
+
 std::error_code make_absolute(SmallVectorImpl<char> &path) {
   if (path::is_absolute(path))
     return {};
@@ -960,7 +960,7 @@ std::error_code make_absolute(SmallVectorImpl<char> &path) {
   if (std::error_code ec = current_path(current_dir))
     return ec;
 
-  path::make_absolute(current_dir, path);
+  make_absolute(current_dir, path);
   return {};
 }
 
diff --git a/llvm/lib/Support/SourceMgr.cpp b/llvm/lib/Support/SourceMgr.cpp
index 708b7668ed7a0..4a69ccc7605bc 100644
--- a/llvm/lib/Support/SourceMgr.cpp
+++ b/llvm/lib/Support/SourceMgr.cpp
@@ -41,17 +41,14 @@ static const size_t TabStop = 8;
 
 // Out of line to avoid needing definition of vfs::FileSystem in header.
 SourceMgr::SourceMgr() = default;
-SourceMgr::SourceMgr(IntrusiveRefCntPtr<vfs::FileSystem> FS)
-    : FS(std::move(FS)) {}
+SourceMgr::~SourceMgr() = default;
 SourceMgr::SourceMgr(SourceMgr &&) = default;
 SourceMgr &SourceMgr::operator=(SourceMgr &&) = default;
-SourceMgr::~SourceMgr() = default;
 
-IntrusiveRefCntPtr<vfs::FileSystem> SourceMgr::getVirtualFileSystem() const {
-  return FS;
-}
+SourceMgr::SourceMgr(IntrusiveRefCntPtr<vfs::FileSystem> FS)
+    : FS(std::move(FS)) {}
 
-void SourceMgr::setVirtualFileSystem(IntrusiveRefCntPtr<vfs::FileSystem> FS) {
+void SourceMgr::setFileSystem(IntrusiveRefCntPtr<vfs::FileSystem> FS) {
   this->FS = std::move(FS);
 }
 
@@ -69,11 +66,10 @@ unsigned SourceMgr::AddIncludeFile(const std::string &Filename,
 ErrorOr<std::unique_ptr<MemoryBuffer>>
 SourceMgr::OpenIncludeFile(const std::string &Filename,
                            std::string &IncludedFile) {
-  auto GetFile = [this](StringRef Path) {
+  auto getFile = [this](StringRef Path) {
     return FS ? FS->getBufferForFile(Path) : MemoryBuffer::getFile(Path);
   };
-
-  ErrorOr<std::unique_ptr<MemoryBuffer>> NewBufOrErr = GetFile(Filename);
+  ErrorOr<std::unique_ptr<MemoryBuffer>> NewBufOrErr = getFile(Filename);
 
   SmallString<64> Buffer(Filename);
   // If the file didn't exist directly, see if it's in an include path.
@@ -81,7 +77,7 @@ SourceMgr::OpenIncludeFile(const std::string &Filename,
        ++i) {
     Buffer = IncludeDirectories[i];
     sys::path::append(Buffer, Filename);
-    NewBufOrErr = GetFile(Buffer);
+    NewBufOrErr = getFile(Buffer);
   }
 
   if (NewBufOrErr)
diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
index 8a27110b88876..312e930f967e7 100644
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -135,7 +135,7 @@ std::error_code FileSystem::makeAbsolute(SmallVectorImpl<char> &Path) const {
   if (!WorkingDir)
     return WorkingDir.getError();
 
-  sys::path::make_absolute(WorkingDir.get(), Path);
+  llvm::sys::fs::make_absolute(WorkingDir.get(), Path);
   return {};
 }
 
@@ -302,7 +302,7 @@ class RealFileSystem : public FileSystem {
     if (!WD || !*WD)
       return Path;
     Path.toVector(Storage);
-    sys::path::make_absolute(WD->get().Resolved, Storage);
+    sys::fs::make_absolute(WD->get().Resolved, Storage);
     return Storage;
   }
 
@@ -1909,12 +1909,7 @@ class llvm::vfs::RedirectingFileSystemParser {
           FullPath = FS->getOverlayFileDir();
           assert(!FullPath.empty() &&
                  "External contents prefix directory must exist");
-          SmallString<256> AbsFullPath = Value;
-          if (FS->makeAbsolute(FullPath, AbsFullPath)) {
-            error(N, "failed to make 'external-contents' absolute");
-            return nullptr;
-          }
-          FullPath = AbsFullPath;
+          llvm::sys::path::append(FullPath, Value);
         } else {
           FullPath = Value;
         }
@@ -1979,7 +1974,7 @@ class llvm::vfs::RedirectingFileSystemParser {
           EC = FS->makeAbsolute(FullPath, Name);
           Name = canonicalize(Name);
         } else {
-          EC = FS->makeAbsolute(Name);
+          EC = sys::fs::make_absolute(Name);
         }
         if (EC) {
           assert(NameValueNode && "Name presence should be checked earlier");
@@ -2210,7 +2205,7 @@ RedirectingFileSystem::create(std::unique_ptr<MemoryBuffer> Buffer,
     //  FS->OverlayFileDir => /<absolute_path_to>/dummy.cache/vfs
     //
     SmallString<256> OverlayAbsDir = sys::path::parent_path(YAMLFilePath);
-    std::error_code EC = FS->makeAbsolute(OverlayAbsDir);
+    std::error_code EC = llvm::sys::fs::make_absolute(OverlayAbsDir);
     assert(!EC && "Overlay dir final path must be absolute");
     (void)EC;
     FS->setOverlayFileDir(OverlayAbsDir);
@@ -2746,9 +2741,19 @@ static void getVFSEntries(RedirectingFileSystem::Entry *SrcE,
   Entries.push_back(YAMLVFSEntry(VPath.c_str(), FE->getExternalContentsPath()));
 }
 
-void vfs::collectVFSEntries(RedirectingFileSystem &VFS,
-                            SmallVectorImpl<YAMLVFSEntry> &CollectedEntries) {
-  ErrorOr<RedirectingFileSystem::LookupResult> RootResult = VFS.lookupPath("/");
+void vfs::collectVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
+                             SourceMgr::DiagHandlerTy DiagHandler,
+                             StringRef YAMLFilePath,
+                             SmallVectorImpl<YAMLVFSEntry> &CollectedEntries,
+                             void *DiagContext,
+                             IntrusiveRefCntPtr<FileSystem> ExternalFS) {
+  std::unique_ptr<RedirectingFileSystem> VFS = RedirectingFileSystem::create(
+      std::move(Buffer), DiagHandler, YAMLFilePath, DiagContext,
+      std::move(ExternalFS));
+  if (!VFS)
+    return;
+  ErrorOr<RedirectingFileSystem::LookupResult> RootResult =
+      VFS->lookupPath("/");
   if (!RootResult)
     return;
   SmallVector<StringRef, 8> Components;
diff --git a/llvm/lib/TableGen/Main.cpp b/llvm/lib/TableGen/Main.cpp
index ce43123da883c..f545706d6fe30 100644
--- a/llvm/lib/TableGen/Main.cpp
+++ b/llvm/lib/TableGen/Main.cpp
@@ -26,7 +26,6 @@
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Record.h"
@@ -131,7 +130,6 @@ int llvm::TableGenMain(const char *argv0,
   // Record the location of the include directory so that the lexer can find
   // it later.
   SrcMgr.setIncludeDirs(IncludeDirs);
-  SrcMgr.setVirtualFileSystem(vfs::getRealFileSystem());
 
   TGParser Parser(SrcMgr, MacroNames, Records, NoWarnOnUnusedTemplateArgs);
 
diff --git a/llvm/lib/TableGen/Parser.cpp b/llvm/lib/TableGen/Parser.cpp
index db45054061524..2c3726a339bb8 100644
--- a/llvm/lib/TableGen/Parser.cpp
+++ b/llvm/lib/TableGen/Parser.cpp
@@ -9,7 +9,6 @@
 #include "llvm/TableGen/Parser.h"
 #include "TGParser.h"
 #include "llvm/Support/MemoryBuffer.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TableGen/Record.h"
 
 using namespace llvm;
@@ -22,7 +21,6 @@ bool llvm::TableGenParseFile(SourceMgr &InputSrcMgr, RecordKeeper &Records) {
   SrcMgr = SourceMgr();
   SrcMgr.takeSourceBuffersFrom(InputSrcMgr);
   SrcMgr.setIncludeDirs(InputSrcMgr.getIncludeDirs());
-  SrcMgr.setVirtualFileSystem(InputSrcMgr.getVirtualFileSystem());
   SrcMgr.setDiagHandler(InputSrcMgr.getDiagHandler(),
                         InputSrcMgr.getDiagContext());
 
diff --git a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
index 9f34375c9feaf..52302241fe365 100644
--- a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
+++ b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
@@ -27,8 +27,6 @@
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/Support/Debug.h"
 
-#include <atomic>
-
 using namespace llvm;
 
 #define DEBUG_TYPE "arm-pseudo"
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index 5e103185fa906..abf365eedec39 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -44,7 +44,6 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetOptions.h"
-#include <atomic>
 #include <optional>
 
 using namespace llvm;
diff --git a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
index 480ff4a8c3cb9..61fef1387d82a 100644
--- a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -572,8 +572,7 @@ class DataFlowSanitizer {
   const uint64_t NumOfElementsInArgOrgTLS = ArgTLSSize / OriginWidthBytes;
 
 public:
-  DataFlowSanitizer(const std::vector<std::string> &ABIListFiles,
-                    IntrusiveRefCntPtr<vfs::FileSystem> FS);
+  DataFlowSanitizer(const std::vector<std::string> &ABIListFiles);
 
   bool runImpl(Module &M,
                llvm::function_ref<TargetLibraryInfo &(Function &)> GetTLI);
@@ -868,11 +867,12 @@ bool LibAtomicFunction(const Function &F) {
 } // end anonymous namespace
 
 DataFlowSanitizer::DataFlowSanitizer(
-    const std::vector<std::string> &ABIListFiles,
-    IntrusiveRefCntPtr<vfs::FileSystem> FS) {
+    const std::vector<std::string> &ABIListFiles) {
   std::vector<std::string> AllABIListFiles(std::move(ABIListFiles));
   llvm::append_range(AllABIListFiles, ClABIListFiles);
-  ABIList.set(SpecialCaseList::createOrDie(AllABIListFiles, *FS));
+  // FIXME: should we propagate vfs::FileSystem to this constructor?
+  ABIList.set(
+      SpecialCaseList::createOrDie(AllABIListFiles, *vfs::getRealFileSystem()));
 
   CombineTaintLookupTableNames.insert_range(ClCombineTaintLookupTables);
 }
@@ -3471,7 +3471,7 @@ PreservedAnalyses DataFlowSanitizerPass::run(Module &M,
         AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
     return FAM.getResult<TargetLibraryAnalysis>(F);
   };
-  if (!DataFlowSanitizer(ABIListFiles, FS).runImpl(M, GetTLI))
+  if (!DataFlowSanitizer(ABIListFiles).runImpl(M, GetTLI))
     return PreservedAnalyses::all();
 
   PreservedAnalyses PA = PreservedAnalyses::none();
diff --git a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
index d8422755c28b8..e5bf2d1187a89 100644
--- a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
@@ -35,7 +35,6 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Regex.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Instrumentation/CFGMST.h"
 #include "llvm/Transforms/Instrumentation/GCOVProfiler.h"
@@ -93,10 +92,8 @@ class GCOVFunction;
 
 class GCOVProfiler {
 public:
-  GCOVProfiler()
-      : GCOVProfiler(GCOVOptions::getDefault(), *vfs::getRealFileSystem()) {}
-  GCOVProfiler(const GCOVOptions &Opts, vfs::FileSystem &VFS)
-      : Options(Opts), VFS(VFS) {}
+  GCOVProfiler() : GCOVProfiler(GCOVOptions::getDefault()) {}
+  GCOVProfiler(const GCOVOptions &Opts) : Options(Opts) {}
   bool
   runOnModule(Module &M, function_ref<BlockFrequencyInfo *(Function &F)> GetBFI,
               function_ref<BranchProbabilityInfo *(Function &F)> GetBPI,
@@ -113,7 +110,6 @@ class GCOVProfiler {
     os->write_zeros(4 - s.size() % 4);
   }
   void writeBytes(const char *Bytes, int Size) { os->write(Bytes, Size); }
-  vfs::FileSystem &getVirtualFileSystem() const { return VFS; }
 
 private:
   // Create the .gcno files for the Module based on DebugInfo.
@@ -170,7 +166,6 @@ class GCOVProfiler {
   std::vector<Regex> ExcludeRe;
   DenseSet<const BasicBlock *> ExecBlocks;
   StringMap<bool> InstrumentedFiles;
-  vfs::FileSystem &VFS;
 };
 
 struct BBInfo {
@@ -219,10 +214,10 @@ static StringRef getFunctionName(const DISubprogram *SP) {
 /// Prefer relative paths in the coverage notes. Clang also may split
 /// up absolute paths into a directory and filename component. When
 /// the relative path doesn't exist, reconstruct the absolute path.
-static SmallString<128> getFilename(const DIScope *SP, vfs::FileSystem &VFS) {
+static SmallString<128> getFilename(const DIScope *SP) {
   SmallString<128> Path;
   StringRef RelPath = SP->getFilename();
-  if (VFS.exists(RelPath))
+  if (sys::fs::exists(RelPath))
     Path = RelPath;
   else
     sys::path::append(Path, SP->getDirectory(), SP->getFilename());
@@ -362,7 +357,7 @@ namespace {
 
     void writeOut(uint32_t CfgChecksum) {
       write(GCOV_TAG_FUNCTION);
-      SmallString<128> Filename = getFilename(SP, P->getVirtualFileSystem());
+      SmallString<128> Filename = getFilename(SP);
       uint32_t BlockLen = 3 + wordsOfString(getFunctionName(SP));
       BlockLen += 1 + wordsOfString(Filename) + 4;
 
@@ -460,7 +455,7 @@ bool GCOVProfiler::isFunctionInstrumented(const Function &F) {
   if (FilterRe.empty() && ExcludeRe.empty()) {
     return true;
   }
-  SmallString<128> Filename = getFilename(F.getSubprogram(), VFS);
+  SmallString<128> Filename = getFilename(F.getSubprogram());
   auto It = InstrumentedFiles.find(Filename);
   if (It != InstrumentedFiles.end()) {
     return It->second;
@@ -472,7 +467,7 @@ bool GCOVProfiler::isFunctionInstrumented(const Function &F) {
   // Path can be
   // /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/bits/*.h so for
   // such a case we must get the real_path.
-  if (VFS.getRealPath(Filename, RealPath)) {
+  if (sys::fs::real_path(Filename, RealPath)) {
     // real_path can fail with path like "foo.c".
     RealFilename = Filename;
   } else {
@@ -529,10 +524,9 @@ std::string GCOVProfiler::mangleName(const DICompileUnit *CU,
   SmallString<128> Filename = CU->getFilename();
   sys::path::replace_extension(Filename, Notes ? "gcno" : "gcda");
   StringRef FName = sys::path::filename(Filename);
-  ErrorOr<std::string> CWD = VFS.getCurrentWorkingDirectory();
-  if (!CWD)
+  SmallString<128> CurPath;
+  if (sys::fs::current_path(CurPath))
     return std::string(FName);
-  SmallString<128> CurPath{*CWD};
   sys::path::append(CurPath, FName);
   return std::string(CurPath);
 }
@@ -560,7 +554,7 @@ bool GCOVProfiler::runOnModule(
 PreservedAnalyses GCOVProfilerPass::run(Module &M,
                                         ModuleAnalysisManager &AM) {
 
-  GCOVProfiler Profiler(GCOVOpts, *VFS);
+  GCOVProfiler Profiler(GCOVOpts);
   FunctionAnalysisManager &FAM =
       AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
 
@@ -795,7 +789,7 @@ bool GCOVProfiler::emitProfileNotes(
       // Add the function line number to the lines of the entry block
       // to have a counter for the function definition.
       uint32_t Line = SP->getLine();
-      auto Filename = getFilename(SP, VFS);
+      auto Filename = getFilename(SP);
 
       BranchProbabilityInfo *BPI = GetBPI(F);
       BlockFrequencyInfo *BFI = GetBFI(F);
@@ -887,7 +881,7 @@ bool GCOVProfiler::emitProfileNotes(
           if (SP != getDISubprogram(Scope))
             continue;
 
-          GCOVLines &Lines = Block.getFile(getFilename(Loc->getScope(), VFS));
+          GCOVLines &Lines = Block.getFile(getFilename(Loc->getScope()));
           Lines.addLine(Loc.getLine());
         }
         Line = 0;
diff --git a/llvm/tools/dsymutil/Reproducer.cpp b/llvm/tools/dsymutil/Reproducer.cpp
index 0c1d3f90af299..31e49cdd0518c 100644
--- a/llvm/tools/dsymutil/Reproducer.cpp
+++ b/llvm/tools/dsymutil/Reproducer.cpp
@@ -37,10 +37,9 @@ ReproducerGenerate::ReproducerGenerate(std::error_code &EC, int Argc,
                                        char **Argv, bool GenerateOnExit)
     : Root(createReproducerDir(EC)), GenerateOnExit(GenerateOnExit) {
   llvm::append_range(Args, ArrayRef(Argv, Argc));
-  auto RealFS = vfs::getRealFileSystem();
   if (!Root.empty())
-    FC = std::make_shared<FileCollector>(Root, Root, RealFS);
-  VFS = FileCollector::createCollectorVFS(std::move(RealFS), FC);
+    FC = std::make_shared<FileCollector>(Root, Root);
+  VFS = FileCollector::createCollectorVFS(vfs::getRealFileSystem(), FC);
 }
 
 ReproducerGenerate::~ReproducerGenerate() {
diff --git a/llvm/tools/llvm-config/llvm-config.cpp b/llvm/tools/llvm-config/llvm-config.cpp
index 7f8c55ab00989..49df8fdcb7f79 100644
--- a/llvm/tools/llvm-config/llvm-config.cpp
+++ b/llvm/tools/llvm-config/llvm-config.cpp
@@ -357,18 +357,18 @@ int main(int argc, char **argv) {
     ActivePrefix = CurrentExecPrefix;
     {
       SmallString<256> Path(LLVM_INSTALL_INCLUDEDIR);
-      sys::path::make_absolute(ActivePrefix, Path);
+      sys::fs::make_absolute(ActivePrefix, Path);
       ActiveIncludeDir = std::string(Path);
     }
     {
       SmallString<256> Path(LLVM_TOOLS_INSTALL_DIR);
-      sys::path::make_absolute(ActivePrefix, Path);
+      sys::fs::make_absolute(ActivePrefix, Path);
       ActiveBinDir = std::string(Path);
     }
     ActiveLibDir = ActivePrefix + "/lib" + LLVM_LIBDIR_SUFFIX;
     {
       SmallString<256> Path(LLVM_INSTALL_PACKAGE_DIR);
-      sys::path::make_absolute(ActivePrefix, Path);
+      sys::fs::make_absolute(ActivePrefix, Path);
       ActiveCMakeDir = std::string(Path);
     }
     ActiveIncludeOption = "-I" + ActiveIncludeDir;
diff --git a/llvm/tools/llvm-dwp/llvm-dwp.cpp b/llvm/tools/llvm-dwp/llvm-dwp.cpp
index 1fb2a654381d1..e34fcadfde5fc 100644
--- a/llvm/tools/llvm-dwp/llvm-dwp.cpp
+++ b/llvm/tools/llvm-dwp/llvm-dwp.cpp
@@ -94,7 +94,7 @@ getDWOFilenames(StringRef ExecFilename) {
         dwarf::toString(Die.find(dwarf::DW_AT_comp_dir), "");
     if (!DWOCompDir.empty()) {
       SmallString<16> DWOPath(DWOName);
-      sys::path::make_absolute(DWOCompDir, DWOPath);
+      sys::fs::make_absolute(DWOCompDir, DWOPath);
       if (!sys::fs::exists(DWOPath) && sys::fs::exists(DWOName))
         DWOPaths.push_back(std::move(DWOName));
       else
diff --git a/llvm/tools/llvm-mc-assemble-fuzzer/llvm-mc-assemble-fuzzer.cpp b/llvm/tools/llvm-mc-assemble-fuzzer/llvm-mc-assemble-fuzzer.cpp
index 5b4d3cd13c2b8..615a39ee9bb4d 100644
--- a/llvm/tools/llvm-mc-assemble-fuzzer/llvm-mc-assemble-fuzzer.cpp
+++ b/llvm/tools/llvm-mc-assemble-fuzzer/llvm-mc-assemble-fuzzer.cpp
@@ -31,7 +31,6 @@
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TargetParser/Host.h"
 #include "llvm/TargetParser/SubtargetFeature.h"
@@ -143,7 +142,6 @@ int AssembleOneInput(const uint8_t *Data, size_t Size) {
 
   static const std::vector<std::string> NoIncludeDirs;
   SrcMgr.setIncludeDirs(NoIncludeDirs);
-  SrcMgr.setVirtualFileSystem(vfs::getRealFileSystem());
 
   static std::string ArchName;
   std::string Error;
diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index b5746fdeb7a00..fd7fd399d15af 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -41,7 +41,6 @@
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/TargetParser/Host.h"
 #include <memory>
@@ -435,7 +434,6 @@ int main(int argc, char **argv) {
   // Record the location of the include directories so that the lexer can find
   // it later.
   SrcMgr.setIncludeDirs(IncludeDirs);
-  SrcMgr.setVirtualFileSystem(vfs::getRealFileSystem());
 
   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
   assert(MRI && "Unable to create target register info!");
diff --git a/llvm/tools/llvm-ml/llvm-ml.cpp b/llvm/tools/llvm-ml/llvm-ml.cpp
index 504ac9d12486d..c8e49edd34e04 100644
--- a/llvm/tools/llvm-ml/llvm-ml.cpp
+++ b/llvm/tools/llvm-ml/llvm-ml.cpp
@@ -41,7 +41,6 @@
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/TargetParser/Host.h"
 #include <ctime>
@@ -316,7 +315,6 @@ int llvm_ml_main(int Argc, char **Argv, const llvm::ToolContext &) {
     }
   }
   SrcMgr.setIncludeDirs(IncludeDirs);
-  SrcMgr.setVirtualFileSystem(vfs::getRealFileSystem());
 
   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
   assert(MRI && "Unable to create target register info!");
diff --git a/llvm/tools/llvm-opt-report/OptReport.cpp b/llvm/tools/llvm-opt-report/OptReport.cpp
index e4b4fc287b8c1..68ed92c8bacea 100644
--- a/llvm/tools/llvm-opt-report/OptReport.cpp
+++ b/llvm/tools/llvm-opt-report/OptReport.cpp
@@ -274,7 +274,7 @@ static bool writeReport(LocationInfoTy &LocationInfo) {
   for (auto &FI : LocationInfo) {
     SmallString<128> FileName(FI.first);
     if (!InputRelDir.empty())
-      sys::path::make_absolute(InputRelDir, FileName);
+      sys::fs::make_absolute(InputRelDir, FileName);
 
     const auto &FileInfo = FI.second;
 
diff --git a/llvm/tools/obj2yaml/obj2yaml.cpp b/llvm/tools/obj2yaml/obj2yaml.cpp
index 94c38d1032c22..63c8cc55ee2d4 100644
--- a/llvm/tools/obj2yaml/obj2yaml.cpp
+++ b/llvm/tools/obj2yaml/obj2yaml.cpp
@@ -104,7 +104,7 @@ int main(int argc, char *argv[]) {
   cl::HideUnrelatedOptions(Cat);
   cl::ParseCommandLineOptions(
       argc, argv, "Dump a YAML description from an object file", nullptr,
-      nullptr, nullptr, /*LongOptionsUseDoubleDash=*/true);
+      nullptr, /*LongOptionsUseDoubleDash=*/true);
 
   std::error_code EC;
   std::unique_ptr<ToolOutputFile> Out(
diff --git a/llvm/tools/opt/NewPMDriver.cpp b/llvm/tools/opt/NewPMDriver.cpp
index a32af1d787269..7d168a6ceb17c 100644
--- a/llvm/tools/opt/NewPMDriver.cpp
+++ b/llvm/tools/opt/NewPMDriver.cpp
@@ -357,25 +357,27 @@ bool llvm::runPassPipeline(
     bool ShouldPreserveBitcodeUseListOrder, bool EmitSummaryIndex,
     bool EmitModuleHash, bool EnableDebugify, bool VerifyDIPreserve,
     bool UnifiedLTO) {
+  auto FS = vfs::getRealFileSystem();
   std::optional<PGOOptions> P;
   switch (PGOKindFlag) {
   case InstrGen:
-    P = PGOOptions(ProfileFile, "", "", MemoryProfileFile, PGOOptions::IRInstr,
-                   PGOOptions::NoCSAction, PGOColdFuncAttr);
+    P = PGOOptions(ProfileFile, "", "", MemoryProfileFile, FS,
+                   PGOOptions::IRInstr, PGOOptions::NoCSAction,
+                   PGOColdFuncAttr);
     break;
   case InstrUse:
-    P = PGOOptions(ProfileFile, "", ProfileRemappingFile, MemoryProfileFile,
+    P = PGOOptions(ProfileFile, "", ProfileRemappingFile, MemoryProfileFile, FS,
                    PGOOptions::IRUse, PGOOptions::NoCSAction, PGOColdFuncAttr);
     break;
   case SampleUse:
-    P = PGOOptions(ProfileFile, "", ProfileRemappingFile, MemoryProfileFile,
+    P = PGOOptions(ProfileFile, "", ProfileRemappingFile, MemoryProfileFile, FS,
                    PGOOptions::SampleUse, PGOOptions::NoCSAction,
                    PGOColdFuncAttr);
     break;
   case NoPGO:
     if (DebugInfoForProfiling || PseudoProbeForProfiling ||
         !MemoryProfileFile.empty())
-      P = PGOOptions("", "", "", MemoryProfileFile, PGOOptions::NoAction,
+      P = PGOOptions("", "", "", MemoryProfileFile, FS, PGOOptions::NoAction,
                      PGOOptions::NoCSAction, PGOColdFuncAttr,
                      DebugInfoForProfiling, PseudoProbeForProfiling);
     else
@@ -397,7 +399,7 @@ bool llvm::runPassPipeline(
         P->CSProfileGenFile = CSProfileGenFile;
       } else
         P = PGOOptions("", CSProfileGenFile, ProfileRemappingFile,
-                       /*MemoryProfile=*/"", PGOOptions::NoAction,
+                       /*MemoryProfile=*/"", FS, PGOOptions::NoAction,
                        PGOOptions::CSIRInstr);
     } else /* CSPGOKindFlag == CSInstrUse */ {
       if (!P) {
diff --git a/llvm/tools/yaml2obj/yaml2obj.cpp b/llvm/tools/yaml2obj/yaml2obj.cpp
index 662648b599954..dcd6dfcd3de2a 100644
--- a/llvm/tools/yaml2obj/yaml2obj.cpp
+++ b/llvm/tools/yaml2obj/yaml2obj.cpp
@@ -115,7 +115,7 @@ int main(int argc, char **argv) {
   cl::HideUnrelatedOptions(Cat);
   cl::ParseCommandLineOptions(
       argc, argv, "Create an object file from a YAML description", nullptr,
-      nullptr, nullptr, /*LongOptionsUseDoubleDash=*/true);
+      nullptr, /*LongOptionsUseDoubleDash=*/true);
 
   constexpr StringRef ProgName = "yaml2obj";
   auto ErrHandler = [&](const Twine &Msg) {
diff --git a/llvm/unittests/Support/CommandLineTest.cpp b/llvm/unittests/Support/CommandLineTest.cpp
index 15d47a7642980..3df4107ebf439 100644
--- a/llvm/unittests/Support/CommandLineTest.cpp
+++ b/llvm/unittests/Support/CommandLineTest.cpp
@@ -1901,20 +1901,20 @@ TEST(CommandLineTest, LongOptions) {
 
   // Fails because `-ab` is treated as `-a -b`, so `-a` is seen twice, and
   // `val1` is unexpected.
-  EXPECT_FALSE(cl::ParseCommandLineOptions(4, args1, StringRef(), &OS, nullptr,
-                                           nullptr, true));
+  EXPECT_FALSE(cl::ParseCommandLineOptions(4, args1, StringRef(),
+                                           &OS, nullptr, true));
   EXPECT_FALSE(Errs.empty()); Errs.clear();
   cl::ResetAllOptionOccurrences();
 
   // Works because `-a` is treated differently than `--ab`.
-  EXPECT_TRUE(cl::ParseCommandLineOptions(4, args2, StringRef(), &OS, nullptr,
-                                          nullptr, true));
+  EXPECT_TRUE(cl::ParseCommandLineOptions(4, args2, StringRef(),
+                                           &OS, nullptr, true));
   EXPECT_TRUE(Errs.empty()); Errs.clear();
   cl::ResetAllOptionOccurrences();
 
   // Works because `-ab` is treated as `-a -b`, and `--ab` is a long option.
-  EXPECT_TRUE(cl::ParseCommandLineOptions(4, args3, StringRef(), &OS, nullptr,
-                                          nullptr, true));
+  EXPECT_TRUE(cl::ParseCommandLineOptions(4, args3, StringRef(),
+                                           &OS, nullptr, true));
   EXPECT_TRUE(OptA);
   EXPECT_TRUE(OptBLong);
   EXPECT_STREQ("val1", OptAB.c_str());
diff --git a/llvm/unittests/Support/FileCollectorTest.cpp b/llvm/unittests/Support/FileCollectorTest.cpp
index 0ece86947b4f2..184d0e3fdfd17 100644
--- a/llvm/unittests/Support/FileCollectorTest.cpp
+++ b/llvm/unittests/Support/FileCollectorTest.cpp
@@ -43,8 +43,7 @@ class TestingFileCollector : public FileCollector {
 TEST(FileCollectorTest, addFile) {
   TempDir root("add_file_root", /*Unique*/ true);
   std::string root_fs(root.path());
-  TestingFileCollector FileCollector(root_fs, root_fs,
-                                     vfs::getRealFileSystem());
+  TestingFileCollector FileCollector(root_fs, root_fs);
 
   FileCollector.addFile("/path/to/a");
   FileCollector.addFile("/path/to/b");
@@ -78,8 +77,7 @@ TEST(FileCollectorTest, addDirectory) {
   TempFile c(ccc.str());
 
   std::string root_fs(file_root.path());
-  TestingFileCollector FileCollector(root_fs, root_fs,
-                                     vfs::getRealFileSystem());
+  TestingFileCollector FileCollector(root_fs, root_fs);
 
   FileCollector.addDirectory(file_root.path());
 
@@ -107,8 +105,7 @@ TEST(FileCollectorTest, copyFiles) {
   // Create file collector and add files.
   TempDir root("copy_files_root", /*Unique*/ true);
   std::string root_fs(root.path());
-  TestingFileCollector FileCollector(root_fs, root_fs,
-                                     vfs::getRealFileSystem());
+  TestingFileCollector FileCollector(root_fs, root_fs);
   FileCollector.addFile(a.path());
   FileCollector.addFile(b.path());
   FileCollector.addFile(c.path());
@@ -136,8 +133,7 @@ TEST(FileCollectorTest, recordAndConstructDirectory) {
   // Create file collector and add files.
   TempDir root("copy_files_root", /*Unique*/ true);
   std::string root_fs(root.path());
-  TestingFileCollector FileCollector(root_fs, root_fs,
-                                     vfs::getRealFileSystem());
+  TestingFileCollector FileCollector(root_fs, root_fs);
   FileCollector.addFile(a.path());
 
   // The empty directory isn't seen until we add it.
@@ -173,8 +169,7 @@ TEST(FileCollectorTest, recordVFSAccesses) {
   // Create file collector and add files.
   TempDir root("copy_files_root", /*Unique*/ true);
   std::string root_fs(root.path());
-  auto Collector = std::make_shared<TestingFileCollector>(
-      root_fs, root_fs, vfs::getRealFileSystem());
+  auto Collector = std::make_shared<TestingFileCollector>(root_fs, root_fs);
   auto VFS =
       FileCollector::createCollectorVFS(vfs::getRealFileSystem(), Collector);
   VFS->status(a.path());
@@ -221,8 +216,7 @@ TEST(FileCollectorTest, Symlinks) {
   // Root where files are copied to.
   TempDir reproducer_root("reproducer_root", /*Unique*/ true);
   std::string root_fs(reproducer_root.path());
-  TestingFileCollector FileCollector(root_fs, root_fs,
-                                     vfs::getRealFileSystem());
+  TestingFileCollector FileCollector(root_fs, root_fs);
 
   // Add all the files to the collector.
   FileCollector.addFile(a.path());
@@ -270,8 +264,7 @@ TEST(FileCollectorTest, recordVFSSymlinkAccesses) {
   // Create file collector and add files.
   TempDir root("copy_files_root", true);
   std::string root_fs(root.path());
-  auto Collector = std::make_shared<TestingFileCollector>(
-      root_fs, root_fs, vfs::getRealFileSystem());
+  auto Collector = std::make_shared<TestingFileCollector>(root_fs, root_fs);
   auto VFS =
       FileCollector::createCollectorVFS(vfs::getRealFileSystem(), Collector);
   SmallString<256> Output;
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index e6d411d1babe4..355aa6b9ade06 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -255,14 +255,14 @@ TEST(Support, Path) {
 
   {
     SmallString<32> Relative("foo.cpp");
-    path::make_absolute("/root", Relative);
+    sys::fs::make_absolute("/root", Relative);
     Relative[5] = '/'; // Fix up windows paths.
     ASSERT_EQ("/root/foo.cpp", Relative);
   }
 
   {
     SmallString<32> Relative("foo.cpp");
-    path::make_absolute("//root", Relative);
+    sys::fs::make_absolute("//root", Relative);
     Relative[6] = '/'; // Fix up windows paths.
     ASSERT_EQ("//root/foo.cpp", Relative);
   }
diff --git a/llvm/unittests/Support/SourceMgrTest.cpp b/llvm/unittests/Support/SourceMgrTest.cpp
index 8121d339f6fa4..41d09ab5adc75 100644
--- a/llvm/unittests/Support/SourceMgrTest.cpp
+++ b/llvm/unittests/Support/SourceMgrTest.cpp
@@ -566,13 +566,3 @@ TEST_F(SourceMgrTest, PrintWithoutLoc) {
   Diag.print(nullptr, OS, false, false, false);
   EXPECT_EQ("message\n", Output);
 }
-
-TEST_F(SourceMgrTest, IncludeDirs) {
-  auto VFS = makeIntrusiveRefCnt<vfs::InMemoryFileSystem>();
-  VFS->addFile("include/file", 0, MemoryBuffer::getMemBuffer("contents"));
-  SM.setVirtualFileSystem(std::move(VFS));
-  SM.setIncludeDirs({"include"});
-  std::string ResolvedPath;
-  unsigned NumBuffers = SM.AddIncludeFile("file", SMLoc(), ResolvedPath);
-  EXPECT_EQ(NumBuffers, 1u);
-}
diff --git a/llvm/unittests/Support/VirtualFileSystemTest.cpp b/llvm/unittests/Support/VirtualFileSystemTest.cpp
index e740784cb9acd..c150d12338b1f 100644
--- a/llvm/unittests/Support/VirtualFileSystemTest.cpp
+++ b/llvm/unittests/Support/VirtualFileSystemTest.cpp
@@ -1954,30 +1954,7 @@ TEST_F(VFSFromYAMLTest, ReturnsExternalPathVFSHit) {
   EXPECT_EQ(0, NumDiagnostics);
 }
 
-TEST_F(VFSFromYAMLTest, RelativeFileDirWithOverlayRelativeSetting) {
-  auto Lower = makeIntrusiveRefCnt<DummyFileSystem>();
-  Lower->addDirectory("//root/foo/bar");
-  Lower->addRegularFile("//root/foo/bar/a");
-  Lower->setCurrentWorkingDirectory("//root/foo");
-  IntrusiveRefCntPtr<vfs::FileSystem> FS =
-      getFromYAMLString("{\n"
-                        "  'case-sensitive': false,\n"
-                        "  'overlay-relative': true,\n"
-                        "  'roots': [\n"
-                        "    { 'name': '//root/foo/bar/b', 'type': 'file',\n"
-                        "      'external-contents': 'a'\n"
-                        "    }\n"
-                        "  ]\n"
-                        "}",
-                        Lower, "bar/overlay");
-
-  ASSERT_NE(FS.get(), nullptr);
-  ErrorOr<vfs::Status> S = FS->status("//root/foo/bar/b");
-  ASSERT_FALSE(S.getError());
-  EXPECT_EQ("//root/foo/bar/a", S->getName());
-}
-
-TEST_F(VFSFromYAMLTest, RootRelativeToOverlayDirTest) {
+TEST_F(VFSFromYAMLTest, RootRelativeTest) {
   IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
   Lower->addDirectory("//root/foo/bar");
   Lower->addRegularFile("//root/foo/bar/a");
@@ -2040,35 +2017,6 @@ TEST_F(VFSFromYAMLTest, RootRelativeToOverlayDirTest) {
 #endif
 }
 
-TEST_F(VFSFromYAMLTest, RootRelativeToCWDTest) {
-  auto Lower = makeIntrusiveRefCnt<DummyFileSystem>();
-  Lower->addDirectory("//root/foo/bar");
-  Lower->addRegularFile("//root/foo/bar/a");
-  Lower->addDirectory("//root/foo/bar/cwd");
-  Lower->addRegularFile("//root/foo/bar/cwd/a");
-  Lower->setCurrentWorkingDirectory("//root/foo/bar/cwd");
-  IntrusiveRefCntPtr<vfs::FileSystem> FS =
-      getFromYAMLString("{\n"
-                        "  'case-sensitive': false,\n"
-                        "  'root-relative': 'cwd',\n"
-                        "  'roots': [\n"
-                        "    { 'name': 'b', 'type': 'file',\n"
-                        "      'external-contents': '//root/foo/bar/a'\n"
-                        "    }\n"
-                        "  ]\n"
-                        "}",
-                        Lower, "//root/foo/bar/overlay");
-
-  ASSERT_NE(FS.get(), nullptr);
-
-  ErrorOr<vfs::Status> S1 = FS->status("//root/foo/bar/b");
-  ASSERT_TRUE(S1.getError());
-
-  ErrorOr<vfs::Status> S2 = FS->status("//root/foo/bar/cwd/b");
-  ASSERT_FALSE(S2.getError());
-  EXPECT_EQ("//root/foo/bar/a", S2->getName());
-}
-
 TEST_F(VFSFromYAMLTest, ReturnsInternalPathVFSHit) {
   IntrusiveRefCntPtr<vfs::InMemoryFileSystem> BaseFS(
       new vfs::InMemoryFileSystem);
@@ -2560,7 +2508,6 @@ TEST_F(VFSFromYAMLTest, RelativePaths) {
   SmallString<128> CWD;
   EC = llvm::sys::fs::current_path(CWD);
   ASSERT_FALSE(EC);
-  Lower->setCurrentWorkingDirectory(CWD);
 
   // Filename at root level without a parent directory.
   IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
diff --git a/llvm/utils/FileCheck/FileCheck.cpp b/llvm/utils/FileCheck/FileCheck.cpp
index 185b6b30994fc..9cf3a3164dfec 100644
--- a/llvm/utils/FileCheck/FileCheck.cpp
+++ b/llvm/utils/FileCheck/FileCheck.cpp
@@ -735,7 +735,7 @@ int main(int argc, char **argv) {
 
   InitLLVM X(argc, argv);
   cl::ParseCommandLineOptions(argc, argv, /*Overview*/ "", /*Errs*/ nullptr,
-                              /*VFS*/ nullptr, "FILECHECK_OPTS");
+                              "FILECHECK_OPTS");
 
   // Select -dump-input* values.  The -help documentation specifies the default
   // value and which value to choose if an option is specified multiple times.
diff --git a/llvm/utils/split-file/split-file.cpp b/llvm/utils/split-file/split-file.cpp
index c7e9ff4b2b682..672877adaba31 100644
--- a/llvm/utils/split-file/split-file.cpp
+++ b/llvm/utils/split-file/split-file.cpp
@@ -148,7 +148,6 @@ int main(int argc, const char **argv) {
       "Split input into multiple parts separated by regex '^(.|//)--- ' and "
       "extract the part specified by '^(.|//)--- <part>'\n",
       nullptr,
-      /*VFS=*/nullptr,
       /*EnvVar=*/nullptr,
       /*LongOptionsUseDoubleDash=*/true);
 
diff --git a/mlir/lib/IR/Diagnostics.cpp b/mlir/lib/IR/Diagnostics.cpp
index 2467441eb7071..3e337951bcd3f 100644
--- a/mlir/lib/IR/Diagnostics.cpp
+++ b/mlir/lib/IR/Diagnostics.cpp
@@ -378,10 +378,8 @@ struct SourceMgrDiagnosticHandlerImpl {
     }
 
     // Otherwise, try to load the source file.
-    auto bufferOrErr = llvm::MemoryBuffer::getFile(filename);
-    if (!bufferOrErr)
-      return 0;
-    unsigned id = mgr.AddNewSourceBuffer(std::move(*bufferOrErr), SMLoc());
+    std::string ignored;
+    unsigned id = mgr.AddIncludeFile(std::string(filename), SMLoc(), ignored);
     filenameToBufId[filename] = id;
     return id;
   }
diff --git a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
index e8a057b686c61..f8ea6ee07447b 100644
--- a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
@@ -36,7 +36,6 @@
 #include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/ReplaceConstant.h"
 #include "llvm/Support/FileSystem.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TargetParser/Triple.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
 
@@ -3534,10 +3533,8 @@ getDeclareTargetRefPtrSuffix(LLVM::GlobalOp globalOp,
           llvm::StringRef(loc.getFilename()), loc.getLine());
     };
 
-    auto vfs = llvm::vfs::getRealFileSystem();
     os << llvm::format(
-        "_%x",
-        ompBuilder.getTargetEntryUniqueInfo(fileInfoCallBack, *vfs).FileID);
+        "_%x", ompBuilder.getTargetEntryUniqueInfo(fileInfoCallBack).FileID);
   }
   os << "_decl_tgt_ref_ptr";
 
@@ -5811,12 +5808,10 @@ convertDeclareTargetAttr(Operation *op, mlir::omp::DeclareTargetAttr attribute,
                                                      lineNo);
       };
 
-      auto vfs = llvm::vfs::getRealFileSystem();
-
       ompBuilder->registerTargetGlobalVariable(
           captureClause, deviceClause, isDeclaration, isExternallyVisible,
-          ompBuilder->getTargetEntryUniqueInfo(fileInfoCallBack, *vfs),
-          mangledName, generatedRefs, /*OpenMPSimd*/ false, targetTriple,
+          ompBuilder->getTargetEntryUniqueInfo(fileInfoCallBack), mangledName,
+          generatedRefs, /*OpenMPSimd*/ false, targetTriple,
           /*GlobalInitializer*/ nullptr, /*VariableLinkage*/ nullptr,
           gVal->getType(), gVal);
 
@@ -5826,9 +5821,9 @@ convertDeclareTargetAttr(Operation *op, mlir::omp::DeclareTargetAttr attribute,
            ompBuilder->Config.hasRequiresUnifiedSharedMemory())) {
         ompBuilder->getAddrOfDeclareTargetVar(
             captureClause, deviceClause, isDeclaration, isExternallyVisible,
-            ompBuilder->getTargetEntryUniqueInfo(fileInfoCallBack, *vfs),
-            mangledName, generatedRefs, /*OpenMPSimd*/ false, targetTriple,
-            gVal->getType(), /*GlobalInitializer*/ nullptr,
+            ompBuilder->getTargetEntryUniqueInfo(fileInfoCallBack), mangledName,
+            generatedRefs, /*OpenMPSimd*/ false, targetTriple, gVal->getType(),
+            /*GlobalInitializer*/ nullptr,
             /*VariableLinkage*/ nullptr);
       }
     }
@@ -6190,9 +6185,7 @@ LogicalResult OpenMPDialectLLVMIRTranslationInterface::amendOperation(
               if (auto filepathAttr = dyn_cast<StringAttr>(attr)) {
                 llvm::OpenMPIRBuilder *ompBuilder =
                     moduleTranslation.getOpenMPBuilder();
-                auto VFS = llvm::vfs::getRealFileSystem();
-                ompBuilder->loadOffloadInfoMetadata(*VFS,
-                                                    filepathAttr.getValue());
+                ompBuilder->loadOffloadInfoMetadata(filepathAttr.getValue());
                 return success();
               }
               return failure();
diff --git a/mlir/lib/Tools/PDLL/Parser/Parser.cpp b/mlir/lib/Tools/PDLL/Parser/Parser.cpp
index f6d665b6e0162..50e10447ee468 100644
--- a/mlir/lib/Tools/PDLL/Parser/Parser.cpp
+++ b/mlir/lib/Tools/PDLL/Parser/Parser.cpp
@@ -28,7 +28,6 @@
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/Support/ScopedPrinter.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Parser.h"
 #include <optional>
@@ -829,7 +828,6 @@ LogicalResult Parser::parseTdInclude(StringRef filename, llvm::SMRange fileLoc,
   llvm::SourceMgr tdSrcMgr;
   tdSrcMgr.AddNewSourceBuffer(std::move(*includeBuffer), SMLoc());
   tdSrcMgr.setIncludeDirs(parserSrcMgr.getIncludeDirs());
-  tdSrcMgr.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
 
   // This class provides a context argument for the llvm::SourceMgr diagnostic
   // handler.
diff --git a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
index acc84a8b98f2f..84f529ae16401 100644
--- a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
+++ b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
@@ -31,7 +31,6 @@
 #include "llvm/ADT/TypeSwitch.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include <optional>
 
 using namespace mlir;
@@ -390,7 +389,6 @@ PDLDocument::PDLDocument(const lsp::URIForFile &uri, StringRef contents,
   llvm::append_range(includeDirs, extraDirs);
 
   sourceMgr.setIncludeDirs(includeDirs);
-  sourceMgr.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
   sourceMgr.AddNewSourceBuffer(std::move(memBuffer), SMLoc());
 
   astContext.getDiagEngine().setHandlerFn([&](const ast::Diagnostic &diag) {
diff --git a/mlir/lib/Tools/tblgen-lsp-server/TableGenServer.cpp b/mlir/lib/Tools/tblgen-lsp-server/TableGenServer.cpp
index fa30674282394..5faeeae839f44 100644
--- a/mlir/lib/Tools/tblgen-lsp-server/TableGenServer.cpp
+++ b/mlir/lib/Tools/tblgen-lsp-server/TableGenServer.cpp
@@ -17,7 +17,6 @@
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Support/Path.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/TableGen/Parser.h"
 #include "llvm/TableGen/Record.h"
 #include <optional>
@@ -438,7 +437,6 @@ void TableGenTextFile::initialize(const lsp::URIForFile &uri,
     return;
   }
   sourceMgr.setIncludeDirs(includeDirs);
-  sourceMgr.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
   sourceMgr.AddNewSourceBuffer(std::move(memBuffer), SMLoc());
 
   // This class provides a context argument for the SourceMgr diagnostic
diff --git a/mlir/tools/mlir-pdll/mlir-pdll.cpp b/mlir/tools/mlir-pdll/mlir-pdll.cpp
index 905becd7745f3..88a5f3639c962 100644
--- a/mlir/tools/mlir-pdll/mlir-pdll.cpp
+++ b/mlir/tools/mlir-pdll/mlir-pdll.cpp
@@ -19,7 +19,6 @@
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/VirtualFileSystem.h"
 #include <set>
 
 using namespace mlir;
@@ -42,7 +41,6 @@ processBuffer(raw_ostream &os, std::unique_ptr<llvm::MemoryBuffer> chunkBuffer,
               bool dumpODS, std::set<std::string> *includedFiles) {
   llvm::SourceMgr sourceMgr;
   sourceMgr.setIncludeDirs(includeDirs);
-  sourceMgr.setVirtualFileSystem(llvm::vfs::getRealFileSystem());
   sourceMgr.AddNewSourceBuffer(std::move(chunkBuffer), SMLoc());
 
   // If we are dumping ODS information, also enable documentation to ensure the