diff --git a/bolt/test/AArch64/ifunc.test b/bolt/test/AArch64/ifunc.test
@@ -0,0 +1,49 @@
+// With -O0 indirect call is performed on IPLT trampoline. IPLT trampoline
+// has IFUNC symbol.
+// RUN: %clang %cflags -nostdlib -O0 -no-pie %p/../Inputs/ifunc.c -fuse-ld=lld \
+// RUN:    -o %t.O0.exe -Wl,-q
+// RUN: llvm-bolt %t.O0.exe -o %t.O0.bolt.exe \
+// RUN:   --print-disasm --print-only=_start | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.O0.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// Non-pie static executable doesn't generate PT_DYNAMIC, check relocation
+// is readed successfully and IPLT trampoline has been identified by bolt.
+// RUN: %clang %cflags -nostdlib -O3 %p/../Inputs/ifunc.c -fuse-ld=lld -no-pie \
+// RUN:   -o %t.O3_nopie.exe -Wl,-q
+// RUN: llvm-readelf -l %t.O3_nopie.exe | \
+// RUN:   FileCheck --check-prefix=NON_DYN_CHECK %s
+// RUN: llvm-bolt %t.O3_nopie.exe -o %t.O3_nopie.bolt.exe  \
+// RUN:   --print-disasm --print-only=_start | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.O3_nopie.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// With -O3 direct call is performed on IPLT trampoline. IPLT trampoline
+// doesn't have associated symbol. The ifunc symbol has the same address as
+// IFUNC resolver function.
+// RUN: %clang %cflags -nostdlib -O3 %p/../Inputs/ifunc.c -fuse-ld=lld -fPIC -pie \
+// RUN:   -o %t.O3_pie.exe -Wl,-q
+// RUN: llvm-bolt %t.O3_pie.exe -o %t.O3_pie.bolt.exe  \
+// RUN:   --print-disasm --print-only=_start | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.O3_pie.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// Check that IPLT trampoline located in .plt section are normally handled by
+// BOLT. The gnu-ld linker doesn't use separate .iplt section.
+// RUN: %clang %cflags -nostdlib -O3 %p/../Inputs/ifunc.c -fuse-ld=lld -fPIC -pie \
+// RUN:   -T %p/../Inputs/iplt.ld -o %t.iplt_O3_pie.exe -Wl,-q
+// RUN: llvm-bolt %t.iplt_O3_pie.exe -o %t.iplt_O3_pie.bolt.exe  \
+// RUN:   --print-disasm --print-only=_start  | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.iplt_O3_pie.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// NON_DYN_CHECK-NOT: DYNAMIC
+
+// CHECK: {{(bl? "(resolver_foo|ifoo).*@PLT"|adr x[0-9]+, ifoo)}}
+
+// REL_CHECK: R_AARCH64_IRELATIVE [[#%x,REL_SYMB_ADDR:]]
+// REL_CHECK: [[#REL_SYMB_ADDR]] {{.*}} FUNC {{.*}} resolver_foo
diff --git a/bolt/test/AArch64/update-weak-reference-symbol.s b/bolt/test/AArch64/update-weak-reference-symbol.s
@@ -3,7 +3,7 @@
 // RUN: %clang %cflags -Wl,-z,notext -shared -Wl,-q %s -o %t.so
 // RUN: llvm-bolt %t.so -o %t.so.bolt
 // RUN: llvm-nm -n %t.so.bolt > %t.out.txt
-// RUN: llvm-objdump -dj .rodata %t.so.bolt >> %t.out.txt
+// RUN: llvm-objdump -z -dj .rodata %t.so.bolt >> %t.out.txt
 // RUN: FileCheck %s --input-file=%t.out.txt
 
 # CHECK: w func_1

diff --git a/bolt/test/Inputs/ifunc.c b/bolt/test/Inputs/ifunc.c
@@ -0,0 +1,12 @@
+// This test checks that IFUNC trampoline is properly recognised by BOLT
+
+static void foo() {}
+static void bar() {}
+
+extern int use_foo;
+
+static void *resolver_foo(void) { return use_foo ? foo : bar; }
+
+__attribute__((ifunc("resolver_foo"))) void ifoo();
+
+void _start() { ifoo(); }
diff --git a/bolt/test/AArch64/Inputs/iplt.ld → bolt/test/Inputs/iplt.ld b/bolt/test/AArch64/Inputs/iplt.ld → bolt/test/Inputs/iplt.ld
diff --git a/bolt/test/X86/ifunc.test b/bolt/test/X86/ifunc.test
@@ -0,0 +1,47 @@
+// Check if BOLT can process ifunc symbols from .plt section
+// RUN: %clang %cflags -nostdlib -no-pie %p/../Inputs/ifunc.c -fuse-ld=lld \
+// RUN:    -o %t.exe -Wl,-q
+// RUN: llvm-bolt %t.exe -o %t.bolt.exe \
+// RUN:   --print-disasm --print-only=_start | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// Check if BOLT can process ifunc symbols from .plt section in non-pie static
+// executable case.
+// RUN: %clang %cflags -nostdlib %p/../Inputs/ifunc.c -fuse-ld=lld -no-pie \
+// RUN:   -o %t.nopie.exe -Wl,-q
+// RUN: llvm-readelf -l %t.nopie.exe | \
+// RUN:   FileCheck --check-prefix=NON_DYN_CHECK %s
+// RUN: llvm-bolt %t.nopie.exe -o %t.nopie.bolt.exe  \
+// RUN:   --print-disasm --print-only=_start | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.nopie.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// Check if BOLT can process ifunc symbols from .plt section in pie executable
+// case.
+// RUN: %clang %cflags -nostdlib %p/../Inputs/ifunc.c -fuse-ld=lld -fPIC -pie \
+// RUN:   -o %t.pie.exe -Wl,-q
+// RUN: llvm-bolt %t.pie.exe -o %t.pie.bolt.exe  \
+// RUN:   --print-disasm --print-only=_start | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.pie.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// Check that IPLT trampoline located in .plt section are normally handled by
+// BOLT. The gnu-ld linker doesn't use separate .iplt section.
+// RUN: %clang %cflags -nostdlib %p/../Inputs/ifunc.c -fuse-ld=lld -fPIC -pie \
+// RUN:   -T %p/../Inputs/iplt.ld -o %t.iplt_pie.exe -Wl,-q
+// RUN: llvm-bolt %t.iplt_pie.exe -o %t.iplt_pie.bolt.exe  \
+// RUN:   --print-disasm --print-only=_start  | \
+// RUN:   FileCheck --check-prefix=CHECK %s
+// RUN: llvm-readelf -aW %t.iplt_pie.bolt.exe | \
+// RUN:   FileCheck --check-prefix=REL_CHECK %s
+
+// NON_DYN_CHECK-NOT: DYNAMIC
+
+// CHECK: callq "resolver_foo/1@PLT"
+
+// REL_CHECK: R_X86_64_IRELATIVE [[#%x,REL_SYMB_ADDR:]]
+// REL_CHECK: [[#REL_SYMB_ADDR]] {{.*}} FUNC {{.*}} resolver_foo
diff --git a/bolt/test/X86/log.test b/bolt/test/X86/log.test
@@ -6,7 +6,7 @@ RUN: yaml2obj %p/Inputs/blarge.yaml &> %t.exe
 RUN: llvm-bolt %t.exe -o %t.null --data %p/Inputs/blarge.fdata -v=2 \
 RUN:   --reorder-blocks=normal --print-finalized --log-file=%t.log  2>&1 \
 RUN:   | FileCheck --check-prefix=CHECK --allow-empty %s
-RUN: cat %t.log | FileCheck %s --check-prefix=CHECK-LOG
+RUN: FileCheck %s --check-prefix=CHECK-LOG --input-file %t.log
 
 CHECK-NOT: BOLT-INFO
 CHECK-NOT: BOLT-WARNING
@@ -16,4 +16,4 @@ CHECK-NOT: BOLT-ERROR
 CHECK-LOG: BOLT-INFO: Target architecture
 CHECK-LOG: BOLT-INFO: BOLT version
 CHECK-LOG: BOLT-INFO: basic block reordering modified layout
-CHECK-LOG:    Binary Function "usqrt"
+CHECK-LOG:    Binary Function "main"
diff --git a/bolt/test/X86/print-only-section.s b/bolt/test/X86/print-only-section.s
@@ -0,0 +1,29 @@
+## Check that --print-only flag works with sections.
+
+# REQUIRES: system-linux
+
+# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-linux %s -o %t.o
+# RUN: ld.lld %t.o -o %t.exe
+# RUN: llvm-bolt %t.exe -o %t.out --print-cfg --print-only=unused_code 2>&1 \
+# RUN:   | FileCheck %s
+
+# CHECK: Binary Function "foo"
+# CHECK-NOT: Binary Function "_start"
+
+  .text
+  .globl _start
+  .type _start, %function
+_start:
+  .cfi_startproc
+  ret
+  .cfi_endproc
+  .size _start, .-_start
+
+  .section unused_code,"ax",@progbits
+  .globl foo
+  .type foo, %function
+foo:
+  .cfi_startproc
+  ret
+  .cfi_endproc
+  .size foo, .-foo
diff --git a/bolt/test/lit.local.cfg b/bolt/test/lit.local.cfg
@@ -1,6 +1,6 @@
 host_linux_triple = config.target_triple.split("-")[0] + "-unknown-linux-gnu"
-common_linker_flags = "-fuse-ld=lld -Wl,--unresolved-symbols=ignore-all"
-flags = f"--target={host_linux_triple} {common_linker_flags}"
+common_linker_flags = "-fuse-ld=lld -Wl,--unresolved-symbols=ignore-all -pie"
+flags = f"--target={host_linux_triple} -fPIE {common_linker_flags}"
 
 config.substitutions.insert(0, ("%cflags", f"%cflags {flags}"))
 config.substitutions.insert(0, ("%cxxflags", f"%cxxflags {flags}"))
diff --git a/bolt/test/merge-fdata-uninitialized-header.test b/bolt/test/merge-fdata-uninitialized-header.test
@@ -0,0 +1,45 @@
+## Test that merge-fdata correctly handles YAML header with an uninitialized
+## fields. a.yaml does not have hash-func set and it used to crash merge-fdata.
+
+# REQUIRES: system-linux
+
+# RUN: split-file %s %t
+# RUN: not merge-fdata %t/a.yaml %t/b.yaml 2>&1 | FileCheck %s
+
+# CHECK: cannot merge profiles with different hash functions
+
+#--- a.yaml
+---
+header:
+  profile-version: 1
+  binary-name:     'a.out'
+  binary-build-id: '<unknown>'
+  profile-flags:   [ lbr ]
+  profile-origin:  branch profile reader
+  profile-events:  ''
+  dfs-order:       false
+functions:
+  - name:            'main'
+    fid:             1
+    hash:            0x50BBA3441D436491
+    exec:            1
+    nblocks:         0
+...
+#--- b.yaml
+---
+header:
+  profile-version: 1
+  binary-name:     'a.out'
+  binary-build-id: '<unknown>'
+  profile-flags:   [ lbr ]
+  profile-origin:  branch profile reader
+  profile-events:  ''
+  dfs-order:       false
+  hash-func: xxh3
+functions:
+  - name:            'main'
+    fid:             1
+    hash:            0x50BBA3441D436491
+    exec:            1
+    nblocks:         0
+...
diff --git a/bolt/test/perf2bolt/lit.local.cfg b/bolt/test/perf2bolt/lit.local.cfg
@@ -1,4 +1,5 @@
 import shutil
+import subprocess
 
-if shutil.which("perf") is not None:
-    config.available_features.add("perf")
+if shutil.which("perf") is not None and subprocess.run(["perf", "record", "-e", "cycles:u", "-o", "/dev/null", "--", "perf", "--version"], capture_output=True).returncode == 0:
+    config.available_features.add("perf")
diff --git a/bolt/test/perf2bolt/perf_test.test b/bolt/test/perf2bolt/perf_test.test
@@ -3,15 +3,12 @@
 REQUIRES: system-linux, perf
 
 RUN: %clang %S/Inputs/perf_test.c -fuse-ld=lld -Wl,--script=%S/Inputs/perf_test.lds -o %t
-RUN: perf record -e cycles:u -o %t2 -- %t
+RUN: perf record -Fmax -e cycles:u -o %t2 -- %t
 RUN: perf2bolt %t -p=%t2 -o %t3 -nl -ignore-build-id 2>&1 | FileCheck %s
 
 CHECK-NOT: PERF2BOLT-ERROR
 CHECK-NOT: !! WARNING !! This high mismatch ratio indicates the input binary is probably not the same binary used during profiling collection.
 
 RUN: %clang %S/Inputs/perf_test.c -no-pie -fuse-ld=lld -o %t4
-RUN: perf record -e cycles:u -o %t5 -- %t4
-RUN: perf2bolt %t4 -p=%t5 -o %t6 -nl -ignore-build-id 2>&1 | FileCheck %s --check-prefix=CHECK-NO-PIE
-
-CHECK-NO-PIE-NOT: PERF2BOLT-ERROR
-CHECK-NO-PIE-NOT: !! WARNING !! This high mismatch ratio indicates the input binary is probably not the same binary used during profiling collection.
+RUN: perf record -Fmax -e cycles:u -o %t5 -- %t4
+RUN: perf2bolt %t4 -p=%t5 -o %t6 -nl -ignore-build-id 2>&1 | FileCheck %s
diff --git a/bolt/tools/merge-fdata/merge-fdata.cpp b/bolt/tools/merge-fdata/merge-fdata.cpp
@@ -145,6 +145,10 @@ void mergeProfileHeaders(BinaryProfileHeader &MergedHeader,
     errs() << "WARNING: merging profiles with different sampling events\n";
     MergedHeader.EventNames += "," + Header.EventNames;
   }
+
+  if (MergedHeader.HashFunction != Header.HashFunction)
+    report_error("merge conflict",
+                 "cannot merge profiles with different hash functions");
 }
 
 void mergeBasicBlockProfile(BinaryBasicBlockProfile &MergedBB,
@@ -386,6 +390,7 @@ int main(int argc, char **argv) {
   // Merged information for all functions.
   StringMap<BinaryFunctionProfile> MergedBFs;
 
+  bool FirstHeader = true;
   for (std::string &InputDataFilename : Inputs) {
     ErrorOr<std::unique_ptr<MemoryBuffer>> MB =
         MemoryBuffer::getFileOrSTDIN(InputDataFilename);
@@ -409,7 +414,12 @@ int main(int argc, char **argv) {
     }
 
     // Merge the header.
-    mergeProfileHeaders(MergedHeader, BP.Header);
+    if (FirstHeader) {
+      MergedHeader = BP.Header;
+      FirstHeader = false;
+    } else {
+      mergeProfileHeaders(MergedHeader, BP.Header);
+    }
 
     // Do the function merge.
     for (BinaryFunctionProfile &BF : BP.Functions) {

diff --git a/bolt/unittests/Core/BinaryContext.cpp b/bolt/unittests/Core/BinaryContext.cpp
@@ -160,13 +160,14 @@ TEST_P(BinaryContextTester, FlushPendingRelocJUMP26) {
 TEST_P(BinaryContextTester, BaseAddress) {
   // Check that  base address calculation is correct for a binary with the
   // following segment layout:
-  BC->SegmentMapInfo[0] = SegmentInfo{0, 0x10e8c2b4, 0, 0x10e8c2b4, 0x1000};
+  BC->SegmentMapInfo[0] =
+      SegmentInfo{0, 0x10e8c2b4, 0, 0x10e8c2b4, 0x1000, true};
   BC->SegmentMapInfo[0x10e8d2b4] =
-      SegmentInfo{0x10e8d2b4, 0x3952faec, 0x10e8c2b4, 0x3952faec, 0x1000};
+      SegmentInfo{0x10e8d2b4, 0x3952faec, 0x10e8c2b4, 0x3952faec, 0x1000, true};
   BC->SegmentMapInfo[0x4a3bddc0] =
-      SegmentInfo{0x4a3bddc0, 0x148e828, 0x4a3bbdc0, 0x148e828, 0x1000};
+      SegmentInfo{0x4a3bddc0, 0x148e828, 0x4a3bbdc0, 0x148e828, 0x1000, true};
   BC->SegmentMapInfo[0x4b84d5e8] =
-      SegmentInfo{0x4b84d5e8, 0x294f830, 0x4b84a5e8, 0x3d3820, 0x1000};
+      SegmentInfo{0x4b84d5e8, 0x294f830, 0x4b84a5e8, 0x3d3820, 0x1000, true};
 
   std::optional<uint64_t> BaseAddress =
       BC->getBaseAddressForMapping(0x7f13f5556000, 0x10e8c000);
@@ -181,13 +182,13 @@ TEST_P(BinaryContextTester, BaseAddress2) {
   // Check that base address calculation is correct for a binary if the
   // alignment in ELF file are different from pagesize.
   // The segment layout is as follows:
-  BC->SegmentMapInfo[0] = SegmentInfo{0, 0x2177c, 0, 0x2177c, 0x10000};
+  BC->SegmentMapInfo[0] = SegmentInfo{0, 0x2177c, 0, 0x2177c, 0x10000, true};
   BC->SegmentMapInfo[0x31860] =
-      SegmentInfo{0x31860, 0x370, 0x21860, 0x370, 0x10000};
+      SegmentInfo{0x31860, 0x370, 0x21860, 0x370, 0x10000, true};
   BC->SegmentMapInfo[0x41c20] =
-      SegmentInfo{0x41c20, 0x1f8, 0x21c20, 0x1f8, 0x10000};
+      SegmentInfo{0x41c20, 0x1f8, 0x21c20, 0x1f8, 0x10000, true};
   BC->SegmentMapInfo[0x54e18] =
-      SegmentInfo{0x54e18, 0x51, 0x24e18, 0x51, 0x10000};
+      SegmentInfo{0x54e18, 0x51, 0x24e18, 0x51, 0x10000, true};
 
   std::optional<uint64_t> BaseAddress =
       BC->getBaseAddressForMapping(0xaaaaea444000, 0x21000);
@@ -197,3 +198,22 @@ TEST_P(BinaryContextTester, BaseAddress2) {
   BaseAddress = BC->getBaseAddressForMapping(0xaaaaea444000, 0x11000);
   ASSERT_FALSE(BaseAddress.has_value());
 }
+
+TEST_P(BinaryContextTester, BaseAddressSegmentsSmallerThanAlignment) {
+  // Check that the correct segment is used to compute the base address
+  // when multiple segments are close together in the ELF file (closer
+  // than the required alignment in the process space).
+  // See https://github.com/llvm/llvm-project/issues/109384
+  BC->SegmentMapInfo[0] = SegmentInfo{0, 0x1d1c, 0, 0x1d1c, 0x10000, false};
+  BC->SegmentMapInfo[0x11d40] =
+      SegmentInfo{0x11d40, 0x11e0, 0x1d40, 0x11e0, 0x10000, true};
+  BC->SegmentMapInfo[0x22f20] =
+      SegmentInfo{0x22f20, 0x10e0, 0x2f20, 0x1f0, 0x10000, false};
+  BC->SegmentMapInfo[0x33110] =
+      SegmentInfo{0x33110, 0x89, 0x3110, 0x88, 0x10000, false};
+
+  std::optional<uint64_t> BaseAddress =
+      BC->getBaseAddressForMapping(0xaaaaaaab1000, 0x1000);
+  ASSERT_TRUE(BaseAddress.has_value());
+  ASSERT_EQ(*BaseAddress, 0xaaaaaaaa0000ULL);
+}
diff --git a/clang-tools-extra/CMakeLists.txt b/clang-tools-extra/CMakeLists.txt
@@ -27,7 +27,6 @@ add_subdirectory(clang-move)
 add_subdirectory(clang-query)
 add_subdirectory(include-cleaner)
 add_subdirectory(pp-trace)
-add_subdirectory(pseudo)
 add_subdirectory(tool-template)
 
 option(CLANG_TOOLS_EXTRA_INCLUDE_DOCS "Generate build targets for the Clang Extra Tools docs."

diff --git a/clang-tools-extra/CODE_OWNERS.TXT b/clang-tools-extra/CODE_OWNERS.TXT
@@ -23,7 +23,7 @@ D: clang-tidy
 
 N: Manuel Klimek
 E: klimek@google.com
-D: clang-rename, all parts of clang-tools-extra not covered by someone else
+D: all parts of clang-tools-extra not covered by someone else
 
 N: Sam McCall
 E: sammccall@google.com

diff --git a/clang-tools-extra/clang-move/HelperDeclRefGraph.cpp b/clang-tools-extra/clang-move/HelperDeclRefGraph.cpp
@@ -76,11 +76,10 @@ HelperDeclRefGraph::getReachableNodes(const Decl *Root) const {
   llvm::DenseSet<const CallGraphNode *> ConnectedNodes;
   std::function<void(const CallGraphNode *)> VisitNode =
       [&](const CallGraphNode *Node) {
-        if (ConnectedNodes.count(Node))
+        if (!ConnectedNodes.insert(Node).second)
           return;
-        ConnectedNodes.insert(Node);
-        for (auto It = Node->begin(), End = Node->end(); It != End; ++It)
-          VisitNode(*It);
+        for (const CallGraphNode::CallRecord &Callee : *Node)
+          VisitNode(Callee);
       };
 
   VisitNode(RootNode);

diff --git a/clang-tools-extra/clang-move/tool/ClangMove.cpp b/clang-tools-extra/clang-move/tool/ClangMove.cpp
@@ -199,7 +199,7 @@ int main(int argc, const char **argv) {
       for (auto I = Files.begin(), E = Files.end(); I != E; ++I) {
         OS << "  {\n";
         OS << "    \"FilePath\": \"" << *I << "\",\n";
-        const auto Entry = FileMgr.getFile(*I);
+        const auto Entry = FileMgr.getOptionalFileRef(*I);
         auto ID = SM.translateFile(*Entry);
         std::string Content;
         llvm::raw_string_ostream ContentStream(Content);

diff --git a/clang-tools-extra/clang-query/Query.cpp b/clang-tools-extra/clang-query/Query.cpp
@@ -146,7 +146,7 @@ bool MatchQuery::run(llvm::raw_ostream &OS, QuerySession &QS) const {
             TD.emitDiagnostic(
                 FullSourceLoc(R.getBegin(), AST->getSourceManager()),
                 DiagnosticsEngine::Note, "\"" + BI->first + "\" binds here",
-                CharSourceRange::getTokenRange(R), std::nullopt);
+                CharSourceRange::getTokenRange(R), {});
           }
         }
         if (QS.PrintOutput) {

diff --git a/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp b/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -380,7 +380,6 @@ void ClangTidyDiagnosticConsumer::HandleDiagnostic(
     ++Context.Stats.ErrorsIgnoredNOLINT;
     // Ignored a warning, should ignore related notes as well
     LastErrorWasIgnored = true;
-    Context.DiagEngine->Clear();
     for (const auto &Error : SuppressionErrors)
       Context.diag(Error);
     return;
@@ -457,7 +456,6 @@ void ClangTidyDiagnosticConsumer::HandleDiagnostic(
   if (Info.hasSourceManager())
     checkFilters(Info.getLocation(), Info.getSourceManager());
 
-  Context.DiagEngine->Clear();
   for (const auto &Error : SuppressionErrors)
     Context.diag(Error);
 }

diff --git a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
@@ -116,9 +116,8 @@ void ExpandModularHeadersPPCallbacks::handleModuleFile(
   if (!MF)
     return;
   // Avoid processing a ModuleFile more than once.
-  if (VisitedModules.count(MF))
+  if (!VisitedModules.insert(MF).second)
     return;
-  VisitedModules.insert(MF);
 
   // Visit all the input files of this module and mark them to record their
   // contents later.

diff --git a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
@@ -78,6 +78,7 @@
 #include "SuspiciousStringviewDataUsageCheck.h"
 #include "SwappedArgumentsCheck.h"
 #include "SwitchMissingDefaultCaseCheck.h"
+#include "TaggedUnionMemberCountCheck.h"
 #include "TerminatingContinueCheck.h"
 #include "ThrowKeywordMissingCheck.h"
 #include "TooSmallLoopVariableCheck.h"
@@ -229,6 +230,8 @@ class BugproneModule : public ClangTidyModule {
         "bugprone-suspicious-stringview-data-usage");
     CheckFactories.registerCheck<SwappedArgumentsCheck>(
         "bugprone-swapped-arguments");
+    CheckFactories.registerCheck<TaggedUnionMemberCountCheck>(
+        "bugprone-tagged-union-member-count");
     CheckFactories.registerCheck<TerminatingContinueCheck>(
         "bugprone-terminating-continue");
     CheckFactories.registerCheck<ThrowKeywordMissingCheck>(

diff --git a/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt b/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
@@ -73,6 +73,7 @@ add_clang_library(clangTidyBugproneModule
   SuspiciousSemicolonCheck.cpp
   SuspiciousStringCompareCheck.cpp
   SwappedArgumentsCheck.cpp
+  TaggedUnionMemberCountCheck.cpp
   TerminatingContinueCheck.cpp
   ThrowKeywordMissingCheck.cpp
   TooSmallLoopVariableCheck.cpp

diff --git a/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.cpp
@@ -97,8 +97,8 @@ DanglingHandleCheck::DanglingHandleCheck(StringRef Name,
                                          ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
       HandleClasses(utils::options::parseStringList(Options.get(
-          "HandleClasses",
-          "std::basic_string_view;std::experimental::basic_string_view"))),
+          "HandleClasses", "std::basic_string_view;std::experimental::basic_"
+                           "string_view;std::span"))),
       IsAHandle(cxxRecordDecl(hasAnyName(HandleClasses)).bind("handle")) {}
 
 void DanglingHandleCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {

diff --git a/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ForwardDeclarationNamespaceCheck.cpp
@@ -107,7 +107,6 @@ static std::string getNameOfNamespace(const CXXRecordDecl *Decl) {
   std::string Ns;
   llvm::raw_string_ostream OStream(Ns);
   NsDecl->printQualifiedName(OStream);
-  OStream.flush();
   return Ns.empty() ? "(global)" : Ns;
 }
 

diff --git a/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/ForwardingReferenceOverloadCheck.cpp
@@ -9,7 +9,6 @@
 #include "ForwardingReferenceOverloadCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
-#include <algorithm>
 
 using namespace clang::ast_matchers;
 
@@ -19,14 +18,14 @@ namespace {
 // Check if the given type is related to std::enable_if.
 AST_MATCHER(QualType, isEnableIf) {
   auto CheckTemplate = [](const TemplateSpecializationType *Spec) {
-    if (!Spec || !Spec->getTemplateName().getAsTemplateDecl()) {
+    if (!Spec)
       return false;
-    }
-    const NamedDecl *TypeDecl =
-        Spec->getTemplateName().getAsTemplateDecl()->getTemplatedDecl();
-    return TypeDecl->isInStdNamespace() &&
-           (TypeDecl->getName() == "enable_if" ||
-            TypeDecl->getName() == "enable_if_t");
+
+    const TemplateDecl *TDecl = Spec->getTemplateName().getAsTemplateDecl();
+
+    return TDecl && TDecl->isInStdNamespace() &&
+           (TDecl->getName() == "enable_if" ||
+            TDecl->getName() == "enable_if_t");
   };
   const Type *BaseType = Node.getTypePtr();
   // Case: pointer or reference to enable_if.

diff --git a/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/PosixReturnCheck.cpp
@@ -7,52 +7,58 @@
 //===----------------------------------------------------------------------===//
 
 #include "PosixReturnCheck.h"
-#include "../utils/Matchers.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Lex/Lexer.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang::tidy::bugprone {
 
-static StringRef getFunctionSpelling(const MatchFinder::MatchResult &Result,
-                                     const char *BindingStr) {
-  const CallExpr *MatchedCall = cast<CallExpr>(
-      (Result.Nodes.getNodeAs<BinaryOperator>(BindingStr))->getLHS());
+static StringRef getFunctionSpelling(const MatchFinder::MatchResult &Result) {
+  const auto *MatchedCall = Result.Nodes.getNodeAs<CallExpr>("call");
   const SourceManager &SM = *Result.SourceManager;
   return Lexer::getSourceText(CharSourceRange::getTokenRange(
                                   MatchedCall->getCallee()->getSourceRange()),
                               SM, Result.Context->getLangOpts());
 }
 
 void PosixReturnCheck::registerMatchers(MatchFinder *Finder) {
+  const auto PosixCall =
+      callExpr(callee(functionDecl(
+                   anyOf(matchesName("^::posix_"), matchesName("^::pthread_")),
+                   unless(hasName("::posix_openpt")))))
+          .bind("call");
+  const auto ZeroIntegerLiteral = integerLiteral(equals(0));
+  const auto NegIntegerLiteral =
+      unaryOperator(hasOperatorName("-"), hasUnaryOperand(integerLiteral()));
+
   Finder->addMatcher(
       binaryOperator(
-          hasOperatorName("<"),
-          hasLHS(callExpr(callee(functionDecl(
-              anyOf(matchesName("^::posix_"), matchesName("^::pthread_")),
-              unless(hasName("::posix_openpt")))))),
-          hasRHS(integerLiteral(equals(0))))
+          anyOf(allOf(hasOperatorName("<"), hasLHS(PosixCall),
+                      hasRHS(ZeroIntegerLiteral)),
+                allOf(hasOperatorName(">"), hasLHS(ZeroIntegerLiteral),
+                      hasRHS(PosixCall))))
           .bind("ltzop"),
       this);
   Finder->addMatcher(
       binaryOperator(
-          hasOperatorName(">="),
-          hasLHS(callExpr(callee(functionDecl(
-              anyOf(matchesName("^::posix_"), matchesName("^::pthread_")),
-              unless(hasName("::posix_openpt")))))),
-          hasRHS(integerLiteral(equals(0))))
+          anyOf(allOf(hasOperatorName(">="), hasLHS(PosixCall),
+                      hasRHS(ZeroIntegerLiteral)),
+                allOf(hasOperatorName("<="), hasLHS(ZeroIntegerLiteral),
+                      hasRHS(PosixCall))))
           .bind("atop"),
       this);
+  Finder->addMatcher(binaryOperator(hasAnyOperatorName("==", "!="),
+                                    hasOperands(PosixCall, NegIntegerLiteral))
+                         .bind("binop"),
+                     this);
   Finder->addMatcher(
-      binaryOperator(
-          hasAnyOperatorName("==", "!=", "<=", "<"),
-          hasLHS(callExpr(callee(functionDecl(
-              anyOf(matchesName("^::posix_"), matchesName("^::pthread_")),
-              unless(hasName("::posix_openpt")))))),
-          hasRHS(unaryOperator(hasOperatorName("-"),
-                               hasUnaryOperand(integerLiteral()))))
+      binaryOperator(anyOf(allOf(hasAnyOperatorName("<=", "<"),
+                                 hasLHS(PosixCall), hasRHS(NegIntegerLiteral)),
+                           allOf(hasAnyOperatorName(">", ">="),
+                                 hasLHS(NegIntegerLiteral), hasRHS(PosixCall))))
           .bind("binop"),
       this);
 }
@@ -61,23 +67,26 @@ void PosixReturnCheck::check(const MatchFinder::MatchResult &Result) {
   if (const auto *LessThanZeroOp =
           Result.Nodes.getNodeAs<BinaryOperator>("ltzop")) {
     SourceLocation OperatorLoc = LessThanZeroOp->getOperatorLoc();
+    StringRef NewBinOp =
+        LessThanZeroOp->getOpcode() == BinaryOperator::Opcode::BO_LT ? ">"
+                                                                     : "<";
     diag(OperatorLoc, "the comparison always evaluates to false because %0 "
                       "always returns non-negative values")
-        << getFunctionSpelling(Result, "ltzop")
-        << FixItHint::CreateReplacement(OperatorLoc, Twine(">").str());
+        << getFunctionSpelling(Result)
+        << FixItHint::CreateReplacement(OperatorLoc, NewBinOp);
     return;
   }
   if (const auto *AlwaysTrueOp =
           Result.Nodes.getNodeAs<BinaryOperator>("atop")) {
     diag(AlwaysTrueOp->getOperatorLoc(),
          "the comparison always evaluates to true because %0 always returns "
          "non-negative values")
-        << getFunctionSpelling(Result, "atop");
+        << getFunctionSpelling(Result);
     return;
   }
   const auto *BinOp = Result.Nodes.getNodeAs<BinaryOperator>("binop");
   diag(BinOp->getOperatorLoc(), "%0 only returns non-negative values")
-      << getFunctionSpelling(Result, "binop");
+      << getFunctionSpelling(Result);
 }
 
 } // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.cpp
@@ -48,6 +48,8 @@ AST_MATCHER_P2(Expr, hasSizeOfDescendant, int, Depth,
   return false;
 }
 
+AST_MATCHER(Expr, offsetOfExpr) { return isa<OffsetOfExpr>(Node); }
+
 CharUnits getSizeOfType(const ASTContext &Ctx, const Type *Ty) {
   if (!Ty || Ty->isIncompleteType() || Ty->isDependentType() ||
       isa<DependentSizedArrayType>(Ty) || !Ty->isConstantSizeType())
@@ -221,17 +223,15 @@ void SizeofExpressionCheck::registerMatchers(MatchFinder *Finder) {
   const auto ElemType =
       arrayType(hasElementType(recordType().bind("elem-type")));
   const auto ElemPtrType = pointerType(pointee(type().bind("elem-ptr-type")));
+  const auto SizeofDivideExpr = binaryOperator(
+      hasOperatorName("/"),
+      hasLHS(
+          ignoringParenImpCasts(sizeOfExpr(hasArgumentOfType(hasCanonicalType(
+              type(anyOf(ElemType, ElemPtrType, type())).bind("num-type")))))),
+      hasRHS(ignoringParenImpCasts(sizeOfExpr(
+          hasArgumentOfType(hasCanonicalType(type().bind("denom-type")))))));
 
-  Finder->addMatcher(
-      binaryOperator(
-          hasOperatorName("/"),
-          hasLHS(ignoringParenImpCasts(sizeOfExpr(hasArgumentOfType(
-              hasCanonicalType(type(anyOf(ElemType, ElemPtrType, type()))
-                                   .bind("num-type")))))),
-          hasRHS(ignoringParenImpCasts(sizeOfExpr(
-              hasArgumentOfType(hasCanonicalType(type().bind("denom-type")))))))
-          .bind("sizeof-divide-expr"),
-      this);
+  Finder->addMatcher(SizeofDivideExpr.bind("sizeof-divide-expr"), this);
 
   // Detect expression like: sizeof(...) * sizeof(...)); most likely an error.
   Finder->addMatcher(binaryOperator(hasOperatorName("*"),
@@ -257,8 +257,9 @@ void SizeofExpressionCheck::registerMatchers(MatchFinder *Finder) {
                          .bind("sizeof-sizeof-expr"),
                      this);
 
-  // Detect sizeof in pointer arithmetic like: N * sizeof(S) == P1 - P2 or
-  // (P1 - P2) / sizeof(S) where P1 and P2 are pointers to type S.
+  // Detect sizeof usage in comparisons involving pointer arithmetics, such as
+  // N * sizeof(T) == P1 - P2 or (P1 - P2) / sizeof(T), where P1 and P2 are
+  // pointers to a type T.
   const auto PtrDiffExpr = binaryOperator(
       hasOperatorName("-"),
       hasLHS(hasType(hasUnqualifiedDesugaredType(pointerType(pointee(
@@ -285,6 +286,47 @@ void SizeofExpressionCheck::registerMatchers(MatchFinder *Finder) {
           hasRHS(ignoringParenImpCasts(SizeOfExpr.bind("sizeof-ptr-div-expr"))))
           .bind("sizeof-in-ptr-arithmetic-div"),
       this);
+
+  // SEI CERT ARR39-C. Do not add or subtract a scaled integer to a pointer.
+  // Detect sizeof, alignof and offsetof usage in pointer arithmetics where
+  // they are used to scale the numeric distance, which is scaled again by
+  // the pointer arithmetic operator. This can result in forming invalid
+  // offsets.
+  //
+  // Examples, where P is a pointer, N is some integer (both compile-time and
+  // run-time): P + sizeof(T), P + sizeof(*P), P + N * sizeof(*P).
+  //
+  // This check does not warn on cases where the pointee type is "1 byte",
+  // as those cases can often come from generics and also do not constitute a
+  // problem because the size does not affect the scale used.
+  const auto InterestingPtrTyForPtrArithmetic =
+      pointerType(pointee(qualType().bind("pointee-type")));
+  const auto SizeofLikeScaleExpr =
+      expr(anyOf(unaryExprOrTypeTraitExpr(ofKind(UETT_SizeOf)),
+                 unaryExprOrTypeTraitExpr(ofKind(UETT_AlignOf)),
+                 offsetOfExpr()))
+          .bind("sizeof-in-ptr-arithmetic-scale-expr");
+  const auto PtrArithmeticIntegerScaleExpr = binaryOperator(
+      hasAnyOperatorName("*", "/"),
+      // sizeof(...) * sizeof(...) and sizeof(...) / sizeof(...) is handled
+      // by this check on another path.
+      hasOperands(expr(hasType(isInteger()), unless(SizeofLikeScaleExpr)),
+                  SizeofLikeScaleExpr));
+  const auto PtrArithmeticScaledIntegerExpr =
+      expr(anyOf(SizeofLikeScaleExpr, PtrArithmeticIntegerScaleExpr),
+           unless(SizeofDivideExpr));
+
+  Finder->addMatcher(
+      expr(anyOf(
+          binaryOperator(hasAnyOperatorName("+", "-"),
+                         hasOperands(hasType(InterestingPtrTyForPtrArithmetic),
+                                     PtrArithmeticScaledIntegerExpr))
+              .bind("sizeof-in-ptr-arithmetic-plusminus"),
+          binaryOperator(hasAnyOperatorName("+=", "-="),
+                         hasLHS(hasType(InterestingPtrTyForPtrArithmetic)),
+                         hasRHS(PtrArithmeticScaledIntegerExpr))
+              .bind("sizeof-in-ptr-arithmetic-plusminus"))),
+      this);
 }
 
 void SizeofExpressionCheck::check(const MatchFinder::MatchResult &Result) {
@@ -409,6 +451,43 @@ void SizeofExpressionCheck::check(const MatchFinder::MatchResult &Result) {
           << SizeOfExpr->getSourceRange() << E->getOperatorLoc()
           << E->getLHS()->getSourceRange() << E->getRHS()->getSourceRange();
     }
+  } else if (const auto *E = Result.Nodes.getNodeAs<BinaryOperator>(
+                 "sizeof-in-ptr-arithmetic-plusminus")) {
+    const auto *PointeeTy = Result.Nodes.getNodeAs<QualType>("pointee-type");
+    const auto *ScaleExpr =
+        Result.Nodes.getNodeAs<Expr>("sizeof-in-ptr-arithmetic-scale-expr");
+    const CharUnits PointeeSize = getSizeOfType(Ctx, PointeeTy->getTypePtr());
+    const int ScaleKind = [ScaleExpr]() {
+      if (const auto *UTTE = dyn_cast<UnaryExprOrTypeTraitExpr>(ScaleExpr))
+        switch (UTTE->getKind()) {
+        case UETT_SizeOf:
+          return 0;
+        case UETT_AlignOf:
+          return 1;
+        default:
+          return -1;
+        }
+
+      if (isa<OffsetOfExpr>(ScaleExpr))
+        return 2;
+
+      return -1;
+    }();
+
+    if (ScaleKind != -1 && PointeeSize > CharUnits::One()) {
+      diag(E->getExprLoc(),
+           "suspicious usage of '%select{sizeof|alignof|offsetof}0(...)' in "
+           "pointer arithmetic; this scaled value will be scaled again by the "
+           "'%1' operator")
+          << ScaleKind << E->getOpcodeStr() << ScaleExpr->getSourceRange();
+      diag(E->getExprLoc(),
+           "'%0' in pointer arithmetic internally scales with 'sizeof(%1)' == "
+           "%2",
+           DiagnosticIDs::Note)
+          << E->getOpcodeStr()
+          << PointeeTy->getAsString(Ctx.getPrintingPolicy())
+          << PointeeSize.getQuantity();
+    }
   }
 }
 

diff --git a/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.h b/clang-tools-extra/clang-tidy/bugprone/SizeofExpressionCheck.h
@@ -13,7 +13,7 @@
 
 namespace clang::tidy::bugprone {
 
-/// Find suspicious usages of sizeof expression.
+/// Find suspicious usages of sizeof expressions.
 ///
 /// For the user-facing documentation see:
 /// http://clang.llvm.org/extra/clang-tidy/checks/bugprone/sizeof-expression.html

diff --git a/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.cpp
@@ -0,0 +1,199 @@
+//===--- TaggedUnionMemberCountCheck.cpp - clang-tidy ---------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "TaggedUnionMemberCountCheck.h"
+#include "../utils/OptionsUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+static constexpr llvm::StringLiteral StrictModeOptionName = "StrictMode";
+static constexpr llvm::StringLiteral EnableCountingEnumHeuristicOptionName =
+    "EnableCountingEnumHeuristic";
+static constexpr llvm::StringLiteral CountingEnumPrefixesOptionName =
+    "CountingEnumPrefixes";
+static constexpr llvm::StringLiteral CountingEnumSuffixesOptionName =
+    "CountingEnumSuffixes";
+
+static constexpr bool StrictModeOptionDefaultValue = false;
+static constexpr bool EnableCountingEnumHeuristicOptionDefaultValue = true;
+static constexpr llvm::StringLiteral CountingEnumPrefixesOptionDefaultValue =
+    "";
+static constexpr llvm::StringLiteral CountingEnumSuffixesOptionDefaultValue =
+    "count";
+
+static constexpr llvm::StringLiteral RootMatchBindName = "root";
+static constexpr llvm::StringLiteral UnionMatchBindName = "union";
+static constexpr llvm::StringLiteral TagMatchBindName = "tags";
+
+namespace {
+
+AST_MATCHER_P2(RecordDecl, fieldCountOfKindIsOne,
+               ast_matchers::internal::Matcher<FieldDecl>, InnerMatcher,
+               StringRef, BindName) {
+  // BoundNodesTreeBuilder resets itself when a match occurs.
+  // So to avoid losing previously saved binds, a temporary instance
+  // is used for matching.
+  //
+  // For precedence, see commit: 5b07de1a5faf4a22ae6fd982b877c5e7e3a76559
+  clang::ast_matchers::internal::BoundNodesTreeBuilder TempBuilder;
+
+  const FieldDecl *FirstMatch = nullptr;
+  for (const FieldDecl *Field : Node.fields()) {
+    if (InnerMatcher.matches(*Field, Finder, &TempBuilder)) {
+      if (FirstMatch) {
+        return false;
+      } else {
+        FirstMatch = Field;
+      }
+    }
+  }
+
+  if (FirstMatch) {
+    Builder->setBinding(BindName, clang::DynTypedNode::create(*FirstMatch));
+    return true;
+  }
+  return false;
+}
+
+} // namespace
+
+TaggedUnionMemberCountCheck::TaggedUnionMemberCountCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      StrictMode(
+          Options.get(StrictModeOptionName, StrictModeOptionDefaultValue)),
+      EnableCountingEnumHeuristic(
+          Options.get(EnableCountingEnumHeuristicOptionName,
+                      EnableCountingEnumHeuristicOptionDefaultValue)),
+      CountingEnumPrefixes(utils::options::parseStringList(
+          Options.get(CountingEnumPrefixesOptionName,
+                      CountingEnumPrefixesOptionDefaultValue))),
+      CountingEnumSuffixes(utils::options::parseStringList(
+          Options.get(CountingEnumSuffixesOptionName,
+                      CountingEnumSuffixesOptionDefaultValue))) {
+  if (!EnableCountingEnumHeuristic) {
+    if (Options.get(CountingEnumPrefixesOptionName))
+      configurationDiag("%0: Counting enum heuristic is disabled but "
+                        "%1 is set")
+          << Name << CountingEnumPrefixesOptionName;
+    if (Options.get(CountingEnumSuffixesOptionName))
+      configurationDiag("%0: Counting enum heuristic is disabled but "
+                        "%1 is set")
+          << Name << CountingEnumSuffixesOptionName;
+  }
+}
+
+void TaggedUnionMemberCountCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, StrictModeOptionName, StrictMode);
+  Options.store(Opts, EnableCountingEnumHeuristicOptionName,
+                EnableCountingEnumHeuristic);
+  Options.store(Opts, CountingEnumPrefixesOptionName,
+                utils::options::serializeStringList(CountingEnumPrefixes));
+  Options.store(Opts, CountingEnumSuffixesOptionName,
+                utils::options::serializeStringList(CountingEnumSuffixes));
+}
+
+void TaggedUnionMemberCountCheck::registerMatchers(MatchFinder *Finder) {
+
+  auto UnionField = fieldDecl(hasType(qualType(
+      hasCanonicalType(recordType(hasDeclaration(recordDecl(isUnion())))))));
+
+  auto EnumField = fieldDecl(hasType(
+      qualType(hasCanonicalType(enumType(hasDeclaration(enumDecl()))))));
+
+  auto hasOneUnionField = fieldCountOfKindIsOne(UnionField, UnionMatchBindName);
+  auto hasOneEnumField = fieldCountOfKindIsOne(EnumField, TagMatchBindName);
+
+  Finder->addMatcher(recordDecl(anyOf(isStruct(), isClass()), hasOneUnionField,
+                                hasOneEnumField, unless(isImplicit()))
+                         .bind(RootMatchBindName),
+                     this);
+}
+
+bool TaggedUnionMemberCountCheck::isCountingEnumLikeName(StringRef Name) const {
+  if (llvm::any_of(CountingEnumPrefixes, [Name](StringRef Prefix) -> bool {
+        return Name.starts_with_insensitive(Prefix);
+      }))
+    return true;
+  if (llvm::any_of(CountingEnumSuffixes, [Name](StringRef Suffix) -> bool {
+        return Name.ends_with_insensitive(Suffix);
+      }))
+    return true;
+  return false;
+}
+
+std::pair<const std::size_t, const EnumConstantDecl *>
+TaggedUnionMemberCountCheck::getNumberOfEnumValues(const EnumDecl *ED) {
+  llvm::SmallSet<llvm::APSInt, 16> EnumValues;
+
+  const EnumConstantDecl *LastEnumConstant = nullptr;
+  for (const EnumConstantDecl *Enumerator : ED->enumerators()) {
+    EnumValues.insert(Enumerator->getInitVal());
+    LastEnumConstant = Enumerator;
+  }
+
+  if (EnableCountingEnumHeuristic && LastEnumConstant &&
+      isCountingEnumLikeName(LastEnumConstant->getName()) &&
+      (LastEnumConstant->getInitVal() == (EnumValues.size() - 1))) {
+    return {EnumValues.size() - 1, LastEnumConstant};
+  }
+
+  return {EnumValues.size(), nullptr};
+}
+
+void TaggedUnionMemberCountCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Root = Result.Nodes.getNodeAs<RecordDecl>(RootMatchBindName);
+  const auto *UnionField =
+      Result.Nodes.getNodeAs<FieldDecl>(UnionMatchBindName);
+  const auto *TagField = Result.Nodes.getNodeAs<FieldDecl>(TagMatchBindName);
+
+  assert(Root && "Root is missing!");
+  assert(UnionField && "UnionField is missing!");
+  assert(TagField && "TagField is missing!");
+  if (!Root || !UnionField || !TagField)
+    return;
+
+  const auto *UnionDef =
+      UnionField->getType().getCanonicalType().getTypePtr()->getAsRecordDecl();
+  const auto *EnumDef = llvm::dyn_cast<EnumDecl>(
+      TagField->getType().getCanonicalType().getTypePtr()->getAsTagDecl());
+
+  assert(UnionDef && "UnionDef is missing!");
+  assert(EnumDef && "EnumDef is missing!");
+  if (!UnionDef || !EnumDef)
+    return;
+
+  const std::size_t UnionMemberCount = llvm::range_size(UnionDef->fields());
+  auto [TagCount, CountingEnumConstantDecl] = getNumberOfEnumValues(EnumDef);
+
+  if (UnionMemberCount > TagCount) {
+    diag(Root->getLocation(),
+         "tagged union has more data members (%0) than tags (%1)!")
+        << UnionMemberCount << TagCount;
+  } else if (StrictMode && UnionMemberCount < TagCount) {
+    diag(Root->getLocation(),
+         "tagged union has fewer data members (%0) than tags (%1)!")
+        << UnionMemberCount << TagCount;
+  }
+
+  if (CountingEnumConstantDecl) {
+    diag(CountingEnumConstantDecl->getLocation(),
+         "assuming that this constant is just an auxiliary value and not "
+         "used for indicating a valid union data member",
+         DiagnosticIDs::Note);
+  }
+}
+
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.h b/clang-tools-extra/clang-tidy/bugprone/TaggedUnionMemberCountCheck.h
@@ -0,0 +1,41 @@
+//===--- TaggedUnionMemberCountCheck.h - clang-tidy -------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TAGGEDUNIONMEMBERCOUNTCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TAGGEDUNIONMEMBERCOUNTCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::bugprone {
+
+/// Gives warnings for tagged unions, where the number of tags is
+/// different from the number of data members inside the union.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/bugprone/tagged-union-member-count.html
+class TaggedUnionMemberCountCheck : public ClangTidyCheck {
+public:
+  TaggedUnionMemberCountCheck(StringRef Name, ClangTidyContext *Context);
+  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+
+private:
+  const bool StrictMode;
+  const bool EnableCountingEnumHeuristic;
+  const std::vector<StringRef> CountingEnumPrefixes;
+  const std::vector<StringRef> CountingEnumSuffixes;
+
+  std::pair<const std::size_t, const EnumConstantDecl *>
+  getNumberOfEnumValues(const EnumDecl *ED);
+  bool isCountingEnumLikeName(StringRef Name) const;
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_TAGGEDUNIONMEMBERCOUNTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "UnsafeFunctionsCheck.h"
+#include "../utils/OptionsUtils.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/PPCallbacks.h"
@@ -18,6 +19,10 @@ using namespace llvm;
 
 namespace clang::tidy::bugprone {
 
+static constexpr llvm::StringLiteral OptionNameCustomFunctions =
+    "CustomFunctions";
+static constexpr llvm::StringLiteral OptionNameReportDefaultFunctions =
+    "ReportDefaultFunctions";
 static constexpr llvm::StringLiteral OptionNameReportMoreUnsafeFunctions =
     "ReportMoreUnsafeFunctions";
 
@@ -26,6 +31,8 @@ static constexpr llvm::StringLiteral FunctionNamesWithAnnexKReplacementId =
 static constexpr llvm::StringLiteral FunctionNamesId = "FunctionsNames";
 static constexpr llvm::StringLiteral AdditionalFunctionNamesId =
     "AdditionalFunctionsNames";
+static constexpr llvm::StringLiteral CustomFunctionNamesId =
+    "CustomFunctionNames";
 static constexpr llvm::StringLiteral DeclRefId = "DRE";
 
 static std::optional<std::string>
@@ -127,57 +134,128 @@ static bool isAnnexKAvailable(std::optional<bool> &CacheVar, Preprocessor *PP,
   return CacheVar.value();
 }
 
+static std::vector<UnsafeFunctionsCheck::CheckedFunction>
+parseCheckedFunctions(StringRef Option, ClangTidyContext *Context) {
+  const std::vector<StringRef> Functions =
+      utils::options::parseStringList(Option);
+  std::vector<UnsafeFunctionsCheck::CheckedFunction> Result;
+  Result.reserve(Functions.size());
+
+  for (StringRef Function : Functions) {
+    if (Function.empty())
+      continue;
+
+    const auto [Name, Rest] = Function.split(',');
+    const auto [Replacement, Reason] = Rest.split(',');
+
+    if (Name.trim().empty()) {
+      Context->configurationDiag("invalid configuration value for option '%0'; "
+                                 "expected the name of an unsafe function")
+          << OptionNameCustomFunctions;
+      continue;
+    }
+
+    Result.push_back(
+        {Name.trim().str(),
+         matchers::MatchesAnyListedNameMatcher::NameMatcher(Name.trim()),
+         Replacement.trim().str(), Reason.trim().str()});
+  }
+
+  return Result;
+}
+
+static std::string serializeCheckedFunctions(
+    const std::vector<UnsafeFunctionsCheck::CheckedFunction> &Functions) {
+  std::vector<std::string> Result;
+  Result.reserve(Functions.size());
+
+  for (const auto &Entry : Functions) {
+    if (Entry.Reason.empty())
+      Result.push_back(Entry.Name + "," + Entry.Replacement);
+    else
+      Result.push_back(Entry.Name + "," + Entry.Replacement + "," +
+                       Entry.Reason);
+  }
+
+  return llvm::join(Result, ";");
+}
+
 UnsafeFunctionsCheck::UnsafeFunctionsCheck(StringRef Name,
                                            ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
+      CustomFunctions(parseCheckedFunctions(
+          Options.get(OptionNameCustomFunctions, ""), Context)),
+      ReportDefaultFunctions(
+          Options.get(OptionNameReportDefaultFunctions, true)),
       ReportMoreUnsafeFunctions(
           Options.get(OptionNameReportMoreUnsafeFunctions, true)) {}
 
 void UnsafeFunctionsCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, OptionNameCustomFunctions,
+                serializeCheckedFunctions(CustomFunctions));
+  Options.store(Opts, OptionNameReportDefaultFunctions, ReportDefaultFunctions);
   Options.store(Opts, OptionNameReportMoreUnsafeFunctions,
                 ReportMoreUnsafeFunctions);
 }
 
 void UnsafeFunctionsCheck::registerMatchers(MatchFinder *Finder) {
-  if (getLangOpts().C11) {
-    // Matching functions with safe replacements only in Annex K.
-    auto FunctionNamesWithAnnexKReplacementMatcher = hasAnyName(
-        "::bsearch", "::ctime", "::fopen", "::fprintf", "::freopen", "::fscanf",
-        "::fwprintf", "::fwscanf", "::getenv", "::gmtime", "::localtime",
-        "::mbsrtowcs", "::mbstowcs", "::memcpy", "::memmove", "::memset",
-        "::printf", "::qsort", "::scanf", "::snprintf", "::sprintf", "::sscanf",
-        "::strcat", "::strcpy", "::strerror", "::strlen", "::strncat",
-        "::strncpy", "::strtok", "::swprintf", "::swscanf", "::vfprintf",
-        "::vfscanf", "::vfwprintf", "::vfwscanf", "::vprintf", "::vscanf",
-        "::vsnprintf", "::vsprintf", "::vsscanf", "::vswprintf", "::vswscanf",
-        "::vwprintf", "::vwscanf", "::wcrtomb", "::wcscat", "::wcscpy",
-        "::wcslen", "::wcsncat", "::wcsncpy", "::wcsrtombs", "::wcstok",
-        "::wcstombs", "::wctomb", "::wmemcpy", "::wmemmove", "::wprintf",
-        "::wscanf");
+  if (ReportDefaultFunctions) {
+    if (getLangOpts().C11) {
+      // Matching functions with safe replacements only in Annex K.
+      auto FunctionNamesWithAnnexKReplacementMatcher = hasAnyName(
+          "::bsearch", "::ctime", "::fopen", "::fprintf", "::freopen",
+          "::fscanf", "::fwprintf", "::fwscanf", "::getenv", "::gmtime",
+          "::localtime", "::mbsrtowcs", "::mbstowcs", "::memcpy", "::memmove",
+          "::memset", "::printf", "::qsort", "::scanf", "::snprintf",
+          "::sprintf", "::sscanf", "::strcat", "::strcpy", "::strerror",
+          "::strlen", "::strncat", "::strncpy", "::strtok", "::swprintf",
+          "::swscanf", "::vfprintf", "::vfscanf", "::vfwprintf", "::vfwscanf",
+          "::vprintf", "::vscanf", "::vsnprintf", "::vsprintf", "::vsscanf",
+          "::vswprintf", "::vswscanf", "::vwprintf", "::vwscanf", "::wcrtomb",
+          "::wcscat", "::wcscpy", "::wcslen", "::wcsncat", "::wcsncpy",
+          "::wcsrtombs", "::wcstok", "::wcstombs", "::wctomb", "::wmemcpy",
+          "::wmemmove", "::wprintf", "::wscanf");
+      Finder->addMatcher(
+          declRefExpr(to(functionDecl(FunctionNamesWithAnnexKReplacementMatcher)
+                             .bind(FunctionNamesWithAnnexKReplacementId)))
+              .bind(DeclRefId),
+          this);
+    }
+
+    // Matching functions with replacements without Annex K.
+    auto FunctionNamesMatcher =
+        hasAnyName("::asctime", "asctime_r", "::gets", "::rewind", "::setbuf");
     Finder->addMatcher(
-        declRefExpr(to(functionDecl(FunctionNamesWithAnnexKReplacementMatcher)
-                           .bind(FunctionNamesWithAnnexKReplacementId)))
+        declRefExpr(
+            to(functionDecl(FunctionNamesMatcher).bind(FunctionNamesId)))
             .bind(DeclRefId),
         this);
+
+    if (ReportMoreUnsafeFunctions) {
+      // Matching functions with replacements without Annex K, at user request.
+      auto AdditionalFunctionNamesMatcher =
+          hasAnyName("::bcmp", "::bcopy", "::bzero", "::getpw", "::vfork");
+      Finder->addMatcher(
+          declRefExpr(to(functionDecl(AdditionalFunctionNamesMatcher)
+                             .bind(AdditionalFunctionNamesId)))
+              .bind(DeclRefId),
+          this);
+    }
   }
 
-  // Matching functions with replacements without Annex K.
-  auto FunctionNamesMatcher =
-      hasAnyName("::asctime", "asctime_r", "::gets", "::rewind", "::setbuf");
-  Finder->addMatcher(
-      declRefExpr(to(functionDecl(FunctionNamesMatcher).bind(FunctionNamesId)))
-          .bind(DeclRefId),
-      this);
-
-  if (ReportMoreUnsafeFunctions) {
-    // Matching functions with replacements without Annex K, at user request.
-    auto AdditionalFunctionNamesMatcher =
-        hasAnyName("::bcmp", "::bcopy", "::bzero", "::getpw", "::vfork");
-    Finder->addMatcher(
-        declRefExpr(to(functionDecl(AdditionalFunctionNamesMatcher)
-                           .bind(AdditionalFunctionNamesId)))
-            .bind(DeclRefId),
-        this);
+  if (!CustomFunctions.empty()) {
+    std::vector<llvm::StringRef> FunctionNames;
+    FunctionNames.reserve(CustomFunctions.size());
+
+    for (const auto &Entry : CustomFunctions)
+      FunctionNames.push_back(Entry.Name);
+
+    auto CustomFunctionsMatcher = matchers::matchesAnyListedName(FunctionNames);
+
+    Finder->addMatcher(declRefExpr(to(functionDecl(CustomFunctionsMatcher)
+                                          .bind(CustomFunctionNamesId)))
+                           .bind(DeclRefId),
+                       this);
   }
 }
 
@@ -186,16 +264,46 @@ void UnsafeFunctionsCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *FuncDecl = cast<FunctionDecl>(DeclRef->getDecl());
   assert(DeclRef && FuncDecl && "No valid matched node in check()");
 
+  // Only one of these are matched at a time.
   const auto *AnnexK = Result.Nodes.getNodeAs<FunctionDecl>(
       FunctionNamesWithAnnexKReplacementId);
   const auto *Normal = Result.Nodes.getNodeAs<FunctionDecl>(FunctionNamesId);
   const auto *Additional =
       Result.Nodes.getNodeAs<FunctionDecl>(AdditionalFunctionNamesId);
-  assert((AnnexK || Normal || Additional) && "No valid match category.");
+  const auto *Custom =
+      Result.Nodes.getNodeAs<FunctionDecl>(CustomFunctionNamesId);
+  assert((AnnexK || Normal || Additional || Custom) &&
+         "No valid match category.");
 
   bool AnnexKIsAvailable =
       isAnnexKAvailable(IsAnnexKAvailable, PP, getLangOpts());
   StringRef FunctionName = FuncDecl->getName();
+
+  if (Custom) {
+    for (const auto &Entry : CustomFunctions) {
+      if (Entry.Pattern.match(*FuncDecl)) {
+        StringRef Reason =
+            Entry.Reason.empty() ? "is marked as unsafe" : Entry.Reason.c_str();
+
+        if (Entry.Replacement.empty()) {
+          diag(DeclRef->getExprLoc(), "function %0 %1; it should not be used")
+              << FuncDecl << Reason << Entry.Replacement
+              << DeclRef->getSourceRange();
+        } else {
+          diag(DeclRef->getExprLoc(),
+               "function %0 %1; '%2' should be used instead")
+              << FuncDecl << Reason << Entry.Replacement
+              << DeclRef->getSourceRange();
+        }
+
+        return;
+      }
+    }
+
+    llvm_unreachable("No custom function was matched.");
+    return;
+  }
+
   const std::optional<std::string> ReplacementFunctionName =
       [&]() -> std::optional<std::string> {
     if (AnnexK) {

diff --git a/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.h b/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_UNSAFEFUNCTIONSCHECK_H
 
 #include "../ClangTidyCheck.h"
+#include "../utils/Matchers.h"
 #include <optional>
 
 namespace clang::tidy::bugprone {
@@ -32,7 +33,18 @@ class UnsafeFunctionsCheck : public ClangTidyCheck {
                            Preprocessor *ModuleExpanderPP) override;
   void onEndOfTranslationUnit() override;
 
+  struct CheckedFunction {
+    std::string Name;
+    matchers::MatchesAnyListedNameMatcher::NameMatcher Pattern;
+    std::string Replacement;
+    std::string Reason;
+  };
+
 private:
+  const std::vector<CheckedFunction> CustomFunctions;
+
+  // If true, the default set of functions are reported.
+  const bool ReportDefaultFunctions;
   /// If true, additional functions from widely used API-s (such as POSIX) are
   /// added to the list of reported functions.
   const bool ReportMoreUnsafeFunctions;

diff --git a/clang-tools-extra/clang-tidy/cert/CERTTidyModule.cpp b/clang-tools-extra/clang-tidy/cert/CERTTidyModule.cpp
@@ -14,6 +14,7 @@
 #include "../bugprone/ReservedIdentifierCheck.h"
 #include "../bugprone/SignalHandlerCheck.h"
 #include "../bugprone/SignedCharMisuseCheck.h"
+#include "../bugprone/SizeofExpressionCheck.h"
 #include "../bugprone/SpuriouslyWakeUpFunctionsCheck.h"
 #include "../bugprone/SuspiciousMemoryComparisonCheck.h"
 #include "../bugprone/UnhandledSelfAssignmentCheck.h"
@@ -281,6 +282,9 @@ class CERTModule : public ClangTidyModule {
         "cert-oop58-cpp");
 
     // C checkers
+    // ARR
+    CheckFactories.registerCheck<bugprone::SizeofExpressionCheck>(
+        "cert-arr39-c");
     // CON
     CheckFactories.registerCheck<bugprone::SpuriouslyWakeUpFunctionsCheck>(
         "cert-con36-c");
@@ -332,6 +336,12 @@ class CERTModule : public ClangTidyModule {
   ClangTidyOptions getModuleOptions() override {
     ClangTidyOptions Options;
     ClangTidyOptions::OptionMap &Opts = Options.CheckOptions;
+    Opts["cert-arr39-c.WarnOnSizeOfConstant"] = "false";
+    Opts["cert-arr39-c.WarnOnSizeOfIntegerExpression"] = "false";
+    Opts["cert-arr39-c.WarnOnSizeOfThis"] = "false";
+    Opts["cert-arr39-c.WarnOnSizeOfCompareToConstant"] = "false";
+    Opts["cert-arr39-c.WarnOnSizeOfPointer"] = "false";
+    Opts["cert-arr39-c.WarnOnSizeOfPointerToAggregate"] = "false";
     Opts["cert-dcl16-c.NewSuffixes"] = "L;LL;LU;LLU";
     Opts["cert-err33-c.CheckedFunctions"] = CertErr33CCheckedFunctions;
     Opts["cert-err33-c.AllowCastToVoid"] = "true";

diff --git a/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.cpp b/clang-tools-extra/clang-tidy/cert/FloatLoopCounter.cpp
@@ -9,22 +9,38 @@
 #include "FloatLoopCounter.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang::tidy::cert {
 
 void FloatLoopCounter::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
-      forStmt(hasIncrement(expr(hasType(realFloatingPointType())))).bind("for"),
+      forStmt(hasIncrement(forEachDescendant(
+                  declRefExpr(hasType(realFloatingPointType()),
+                              to(varDecl().bind("var")))
+                      .bind("inc"))),
+              hasCondition(forEachDescendant(
+                  declRefExpr(hasType(realFloatingPointType()),
+                              to(varDecl(equalsBoundNode("var"))))
+                      .bind("cond"))))
+          .bind("for"),
       this);
 }
 
 void FloatLoopCounter::check(const MatchFinder::MatchResult &Result) {
   const auto *FS = Result.Nodes.getNodeAs<ForStmt>("for");
 
-  diag(FS->getInc()->getExprLoc(), "loop induction expression should not have "
-                                   "floating-point type");
+  diag(FS->getInc()->getBeginLoc(), "loop induction expression should not have "
+                                    "floating-point type")
+      << Result.Nodes.getNodeAs<DeclRefExpr>("inc")->getSourceRange()
+      << Result.Nodes.getNodeAs<DeclRefExpr>("cond")->getSourceRange();
+
+  if (!FS->getInc()->getType()->isRealFloatingType())
+    if (const auto *V = Result.Nodes.getNodeAs<VarDecl>("var"))
+      diag(V->getBeginLoc(), "floating-point type loop induction variable",
+           DiagnosticIDs::Note);
 }
 
 } // namespace clang::tidy::cert
diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
@@ -83,7 +83,7 @@ static void updateAssignmentLevel(
       memberExpr(hasObjectExpression(cxxThisExpr()),
                  member(fieldDecl(indexNotLessThan(Field->getFieldIndex()))));
   auto DeclMatcher = declRefExpr(
-      to(varDecl(unless(parmVarDecl()), hasDeclContext(equalsNode(Ctor)))));
+      to(valueDecl(unless(parmVarDecl()), hasDeclContext(equalsNode(Ctor)))));
   const bool HasDependence = !match(expr(anyOf(MemberMatcher, DeclMatcher,
                                                hasDescendant(MemberMatcher),
                                                hasDescendant(DeclMatcher))),

diff --git a/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp b/clang-tools-extra/clang-tidy/misc/DefinitionsInHeadersCheck.cpp
@@ -102,7 +102,7 @@ void DefinitionsInHeadersCheck::check(const MatchFinder::MatchResult &Result) {
     // inline is not allowed for main function.
     if (FD->isMain())
       return;
-    diag(FD->getLocation(), /*Description=*/"make as 'inline'",
+    diag(FD->getLocation(), "mark the definition as 'inline'",
          DiagnosticIDs::Note)
         << FixItHint::CreateInsertion(FD->getInnerLocStart(), "inline ");
   } else if (const auto *VD = dyn_cast<VarDecl>(ND)) {

diff --git a/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.cpp b/clang-tools-extra/clang-tidy/misc/UnusedUsingDeclsCheck.cpp
@@ -25,6 +25,13 @@ AST_MATCHER_P(DeducedTemplateSpecializationType, refsToTemplatedDecl,
   return false;
 }
 
+AST_MATCHER_P(Type, asTagDecl, clang::ast_matchers::internal::Matcher<TagDecl>,
+              DeclMatcher) {
+  if (const TagDecl *ND = Node.getAsTagDecl())
+    return DeclMatcher.matches(*ND, Finder, Builder);
+  return false;
+}
+
 } // namespace
 
 // A function that helps to tell whether a TargetDecl in a UsingDecl will be
@@ -61,7 +68,8 @@ void UnusedUsingDeclsCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(userDefinedLiteral().bind("used"), this);
   Finder->addMatcher(
       loc(elaboratedType(unless(hasQualifier(nestedNameSpecifier())),
-                         hasUnqualifiedDesugaredType(type().bind("usedType")))),
+                         hasUnqualifiedDesugaredType(
+                             type(asTagDecl(tagDecl().bind("used")))))),
       this);
   // Cases where we can identify the UsingShadowDecl directly, rather than
   // just its target.
@@ -139,12 +147,6 @@ void UnusedUsingDeclsCheck::check(const MatchFinder::MatchResult &Result) {
     return;
   }
 
-  if (const auto *T = Result.Nodes.getNodeAs<Type>("usedType")) {
-    if (const auto *ND = T->getAsTagDecl())
-      RemoveNamedDecl(ND);
-    return;
-  }
-
   if (const auto *UsedShadow =
           Result.Nodes.getNodeAs<UsingShadowDecl>("usedShadow")) {
     removeFromFoundDecls(UsedShadow->getTargetDecl());

diff --git a/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp b/clang-tools-extra/clang-tidy/modernize/AvoidCArraysCheck.cpp
@@ -9,6 +9,7 @@
 #include "AvoidCArraysCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
 
 using namespace clang::ast_matchers;
 
@@ -60,6 +61,7 @@ void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) {
 
   Finder->addMatcher(
       typeLoc(hasValidBeginLoc(), hasType(arrayType()),
+              optionally(hasParent(parmVarDecl().bind("param_decl"))),
               unless(anyOf(hasParent(parmVarDecl(isArgvOfMain())),
                            hasParent(varDecl(isExternC())),
                            hasParent(fieldDecl(
@@ -72,11 +74,28 @@ void AvoidCArraysCheck::registerMatchers(MatchFinder *Finder) {
 
 void AvoidCArraysCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *ArrayType = Result.Nodes.getNodeAs<TypeLoc>("typeloc");
-
+  const bool IsInParam =
+      Result.Nodes.getNodeAs<ParmVarDecl>("param_decl") != nullptr;
+  const bool IsVLA = ArrayType->getTypePtr()->isVariableArrayType();
+  enum class RecommendType { Array, Vector, Span };
+  llvm::SmallVector<const char *> RecommendTypes{};
+  if (IsVLA) {
+    RecommendTypes.push_back("'std::vector'");
+  } else if (ArrayType->getTypePtr()->isIncompleteArrayType() && IsInParam) {
+    // in function parameter, we also don't know the size of
+    // IncompleteArrayType.
+    if (Result.Context->getLangOpts().CPlusPlus20)
+      RecommendTypes.push_back("'std::span'");
+    else {
+      RecommendTypes.push_back("'std::array'");
+      RecommendTypes.push_back("'std::vector'");
+    }
+  } else {
+    RecommendTypes.push_back("'std::array'");
+  }
   diag(ArrayType->getBeginLoc(),
-       "do not declare %select{C-style|C VLA}0 arrays, use "
-       "%select{std::array<>|std::vector<>}0 instead")
-      << ArrayType->getTypePtr()->isVariableArrayType();
+       "do not declare %select{C-style|C VLA}0 arrays, use %1 instead")
+      << IsVLA << llvm::join(RecommendTypes, " or ");
 }
 
 } // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
@@ -262,7 +262,7 @@ StatementMatcher makeIteratorLoopMatcher(bool IsReverse) {
 ///     EndVarName: 'j' (as a VarDecl)
 ///   In the second example only:
 ///     EndCallName: 'container.size()' (as a CXXMemberCallExpr) or
-///     'size(contaner)' (as a CallExpr)
+///     'size(container)' (as a CallExpr)
 ///
 /// Client code will need to make sure that:
 ///   - The containers on which 'size()' is called is the container indexed.
@@ -491,7 +491,7 @@ static bool isDirectMemberExpr(const Expr *E) {
 }
 
 /// Given an expression that represents an usage of an element from the
-/// containter that we are iterating over, returns false when it can be
+/// container that we are iterating over, returns false when it can be
 /// guaranteed this element cannot be modified as a result of this usage.
 static bool canBeModified(ASTContext *Context, const Expr *E) {
   if (E->getType().isConstQualified())
@@ -922,7 +922,7 @@ bool LoopConvertCheck::isConvertible(ASTContext *Context,
                                      const ast_matchers::BoundNodes &Nodes,
                                      const ForStmt *Loop,
                                      LoopFixerKind FixerKind) {
-  // In self contained diagnosics mode we don't want dependancies on other
+  // In self contained diagnostic mode we don't want dependencies on other
   // loops, otherwise, If we already modified the range of this for loop, don't
   // do any further updates on this iteration.
   if (areDiagsSelfContained())

diff --git a/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.cpp
@@ -72,7 +72,11 @@ static FindArgsResult findArgs(const CallExpr *Call) {
   return Result;
 }
 
-static SmallVector<FixItHint>
+// Returns `true` as `first` only if a nested call to `std::min` or
+// `std::max` was found. Checking if `FixItHint`s were generated is not enough,
+// as the explicit casts that the check introduces may be generated without a
+// nested `std::min` or `std::max` call.
+static std::pair<bool, SmallVector<FixItHint>>
 generateReplacements(const MatchFinder::MatchResult &Match,
                      const CallExpr *TopCall, const FindArgsResult &Result,
                      const bool IgnoreNonTrivialTypes,
@@ -91,13 +95,15 @@ generateReplacements(const MatchFinder::MatchResult &Match,
   const bool IsResultTypeTrivial = ResultType.isTrivialType(*Match.Context);
 
   if ((!IsResultTypeTrivial && IgnoreNonTrivialTypes))
-    return FixItHints;
+    return {false, FixItHints};
 
   if (IsResultTypeTrivial &&
       static_cast<std::uint64_t>(
           Match.Context->getTypeSizeInChars(ResultType).getQuantity()) >
           IgnoreTrivialTypesOfSizeAbove)
-    return FixItHints;
+    return {false, FixItHints};
+
+  bool FoundNestedCall = false;
 
   for (const Expr *Arg : Result.Args) {
     const auto *InnerCall = dyn_cast<CallExpr>(Arg->IgnoreParenImpCasts());
@@ -146,6 +152,9 @@ generateReplacements(const MatchFinder::MatchResult &Match,
                                        *Match.Context))
       continue;
 
+    // We have found a nested call
+    FoundNestedCall = true;
+
     // remove the function call
     FixItHints.push_back(
         FixItHint::CreateRemoval(InnerCall->getCallee()->getSourceRange()));
@@ -168,7 +177,7 @@ generateReplacements(const MatchFinder::MatchResult &Match,
           CharSourceRange::getTokenRange(InnerResult.First->getEndLoc())));
     }
 
-    const SmallVector<FixItHint> InnerReplacements = generateReplacements(
+    const auto [_, InnerReplacements] = generateReplacements(
         Match, InnerCall, InnerResult, IgnoreNonTrivialTypes,
         IgnoreTrivialTypesOfSizeAbove);
 
@@ -189,7 +198,7 @@ generateReplacements(const MatchFinder::MatchResult &Match,
     }
   }
 
-  return FixItHints;
+  return {FoundNestedCall, FixItHints};
 }
 
 MinMaxUseInitializerListCheck::MinMaxUseInitializerListCheck(
@@ -238,11 +247,11 @@ void MinMaxUseInitializerListCheck::check(
   const auto *TopCall = Match.Nodes.getNodeAs<CallExpr>("topCall");
 
   const FindArgsResult Result = findArgs(TopCall);
-  const SmallVector<FixItHint> Replacements =
+  const auto [FoundNestedCall, Replacements] =
       generateReplacements(Match, TopCall, Result, IgnoreNonTrivialTypes,
                            IgnoreTrivialTypesOfSizeAbove);
 
-  if (Replacements.empty())
+  if (!FoundNestedCall)
     return;
 
   const DiagnosticBuilder Diagnostic =

diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -35,10 +35,20 @@ AST_MATCHER(Type, sugaredNullptrType) {
 /// to null within.
 /// Finding sequences of explicit casts is necessary so that an entire sequence
 /// can be replaced instead of just the inner-most implicit cast.
+///
+/// TODO/NOTE: The second "anyOf" below discards matches on a substituted type,
+/// since we don't know if that would _always_ be a pointer type for all other
+/// specializations, unless the expression was "__null", in which case we assume
+/// that all specializations are expected to be for pointer types. Ideally this
+/// would check for the "NULL" macro instead, but that'd be harder to express.
+/// In practice, "NULL" is often defined as "__null", and this is a useful
+/// condition.
 StatementMatcher makeCastSequenceMatcher(llvm::ArrayRef<StringRef> NameList) {
   auto ImplicitCastToNull = implicitCastExpr(
       anyOf(hasCastKind(CK_NullToPointer), hasCastKind(CK_NullToMemberPointer)),
-      unless(hasImplicitDestinationType(qualType(substTemplateTypeParmType()))),
+      anyOf(hasSourceExpression(gnuNullExpr()),
+            unless(hasImplicitDestinationType(
+                qualType(substTemplateTypeParmType())))),
       unless(hasSourceExpression(hasType(sugaredNullptrType()))),
       unless(hasImplicitDestinationType(
           qualType(matchers::matchesAnyListedTypeName(NameList)))));

diff --git a/clang-tools-extra/clang-tidy/readability/AvoidUnconditionalPreprocessorIfCheck.cpp b/clang-tools-extra/clang-tidy/readability/AvoidUnconditionalPreprocessorIfCheck.cpp
@@ -84,7 +84,8 @@ struct AvoidUnconditionalPreprocessorIfPPCallbacks : public PPCallbacks {
       return (Tok.getRawIdentifier() == "true" ||
               Tok.getRawIdentifier() == "false");
     default:
-      return Tok.getKind() >= tok::l_square && Tok.getKind() <= tok::caretcaret;
+      return Tok.getKind() >= tok::l_square &&
+             Tok.getKind() <= tok::greatergreatergreater;
     }
   }
 

diff --git a/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.cpp b/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.cpp
@@ -13,30 +13,40 @@
 using namespace clang::ast_matchers;
 
 namespace clang::tidy::readability {
-
 void ContainerContainsCheck::registerMatchers(MatchFinder *Finder) {
-  const auto SupportedContainers = hasType(
-      hasUnqualifiedDesugaredType(recordType(hasDeclaration(cxxRecordDecl(
-          hasAnyName("::std::set", "::std::unordered_set", "::std::map",
-                     "::std::unordered_map", "::std::multiset",
-                     "::std::unordered_multiset", "::std::multimap",
-                     "::std::unordered_multimap"))))));
+  const auto HasContainsMatchingParamType = hasMethod(
+      cxxMethodDecl(isConst(), parameterCountIs(1), returns(booleanType()),
+                    hasName("contains"), unless(isDeleted()), isPublic(),
+                    hasParameter(0, hasType(hasUnqualifiedDesugaredType(
+                                        equalsBoundNode("parameterType"))))));
 
   const auto CountCall =
-      cxxMemberCallExpr(on(SupportedContainers),
-                        callee(cxxMethodDecl(hasName("count"))),
-                        argumentCountIs(1))
+      cxxMemberCallExpr(
+          argumentCountIs(1),
+          callee(cxxMethodDecl(
+              hasName("count"),
+              hasParameter(0, hasType(hasUnqualifiedDesugaredType(
+                                  type().bind("parameterType")))),
+              ofClass(cxxRecordDecl(HasContainsMatchingParamType)))))
           .bind("call");
 
   const auto FindCall =
-      cxxMemberCallExpr(on(SupportedContainers),
-                        callee(cxxMethodDecl(hasName("find"))),
-                        argumentCountIs(1))
+      cxxMemberCallExpr(
+          argumentCountIs(1),
+          callee(cxxMethodDecl(
+              hasName("find"),
+              hasParameter(0, hasType(hasUnqualifiedDesugaredType(
+                                  type().bind("parameterType")))),
+              ofClass(cxxRecordDecl(HasContainsMatchingParamType)))))
           .bind("call");
 
-  const auto EndCall = cxxMemberCallExpr(on(SupportedContainers),
-                                         callee(cxxMethodDecl(hasName("end"))),
-                                         argumentCountIs(0));
+  const auto EndCall = cxxMemberCallExpr(
+      argumentCountIs(0),
+      callee(
+          cxxMethodDecl(hasName("end"),
+                        // In the matchers below, FindCall should always appear
+                        // before EndCall so 'parameterType' is properly bound.
+                        ofClass(cxxRecordDecl(HasContainsMatchingParamType)))));
 
   const auto Literal0 = integerLiteral(equals(0));
   const auto Literal1 = integerLiteral(equals(1));
@@ -52,10 +62,7 @@ void ContainerContainsCheck::registerMatchers(MatchFinder *Finder) {
                          .bind("positiveComparison"),
                      this);
   AddSimpleMatcher(
-      binaryOperator(hasLHS(CountCall), hasOperatorName("!="), hasRHS(Literal0))
-          .bind("positiveComparison"));
-  AddSimpleMatcher(
-      binaryOperator(hasLHS(Literal0), hasOperatorName("!="), hasRHS(CountCall))
+      binaryOperator(hasOperatorName("!="), hasOperands(CountCall, Literal0))
           .bind("positiveComparison"));
   AddSimpleMatcher(
       binaryOperator(hasLHS(CountCall), hasOperatorName(">"), hasRHS(Literal0))
@@ -72,10 +79,7 @@ void ContainerContainsCheck::registerMatchers(MatchFinder *Finder) {
 
   // Find inverted membership tests which use `count()`.
   AddSimpleMatcher(
-      binaryOperator(hasLHS(CountCall), hasOperatorName("=="), hasRHS(Literal0))
-          .bind("negativeComparison"));
-  AddSimpleMatcher(
-      binaryOperator(hasLHS(Literal0), hasOperatorName("=="), hasRHS(CountCall))
+      binaryOperator(hasOperatorName("=="), hasOperands(CountCall, Literal0))
           .bind("negativeComparison"));
   AddSimpleMatcher(
       binaryOperator(hasLHS(CountCall), hasOperatorName("<="), hasRHS(Literal0))
@@ -92,10 +96,10 @@ void ContainerContainsCheck::registerMatchers(MatchFinder *Finder) {
 
   // Find membership tests based on `find() == end()`.
   AddSimpleMatcher(
-      binaryOperator(hasLHS(FindCall), hasOperatorName("!="), hasRHS(EndCall))
+      binaryOperator(hasOperatorName("!="), hasOperands(FindCall, EndCall))
           .bind("positiveComparison"));
   AddSimpleMatcher(
-      binaryOperator(hasLHS(FindCall), hasOperatorName("=="), hasRHS(EndCall))
+      binaryOperator(hasOperatorName("=="), hasOperands(FindCall, EndCall))
           .bind("negativeComparison"));
 }
 

diff --git a/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.h b/clang-tools-extra/clang-tidy/readability/ContainerContainsCheck.h
@@ -13,8 +13,9 @@
 
 namespace clang::tidy::readability {
 
-/// Finds usages of `container.count()` and `find() == end()` which should be
-/// replaced by a call to the `container.contains()` method introduced in C++20.
+/// Finds usages of `container.count()` and
+/// `container.find() == container.end()` which should be replaced by a call
+/// to the `container.contains()` method.
 ///
 /// For the user-facing documentation see:
 /// http://clang.llvm.org/extra/clang-tidy/checks/readability/container-contains.html
@@ -24,10 +25,11 @@ class ContainerContainsCheck : public ClangTidyCheck {
       : ClangTidyCheck(Name, Context) {}
   void registerMatchers(ast_matchers::MatchFinder *Finder) final;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) final;
-
-protected:
   bool isLanguageVersionSupported(const LangOptions &LO) const final {
-    return LO.CPlusPlus20;
+    return LO.CPlusPlus;
+  }
+  std::optional<TraversalKind> getCheckTraversalKind() const override {
+    return TK_AsIs;
   }
 };
 

diff --git a/clang-tools-extra/clang-tidy/readability/EnumInitialValueCheck.cpp b/clang-tools-extra/clang-tidy/readability/EnumInitialValueCheck.cpp
@@ -141,16 +141,18 @@ void EnumInitialValueCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
 }
 
 void EnumInitialValueCheck::registerMatchers(MatchFinder *Finder) {
-  Finder->addMatcher(
-      enumDecl(unless(isMacro()), unless(hasConsistentInitialValues()))
-          .bind("inconsistent"),
-      this);
+  Finder->addMatcher(enumDecl(isDefinition(), unless(isMacro()),
+                              unless(hasConsistentInitialValues()))
+                         .bind("inconsistent"),
+                     this);
   if (!AllowExplicitZeroFirstInitialValue)
     Finder->addMatcher(
-        enumDecl(hasZeroInitialValueForFirstEnumerator()).bind("zero_first"),
+        enumDecl(isDefinition(), hasZeroInitialValueForFirstEnumerator())
+            .bind("zero_first"),
         this);
   if (!AllowExplicitSequentialInitialValues)
-    Finder->addMatcher(enumDecl(unless(isMacro()), hasSequentialInitialValues())
+    Finder->addMatcher(enumDecl(isDefinition(), unless(isMacro()),
+                                hasSequentialInitialValues())
                            .bind("sequential"),
                        this);
 }
@@ -159,7 +161,7 @@ void EnumInitialValueCheck::check(const MatchFinder::MatchResult &Result) {
   if (const auto *Enum = Result.Nodes.getNodeAs<EnumDecl>("inconsistent")) {
     DiagnosticBuilder Diag =
         diag(Enum->getBeginLoc(),
-             "inital values in enum %0 are not consistent, consider explicit "
+             "initial values in enum %0 are not consistent, consider explicit "
              "initialization of all, none or only the first enumerator")
         << Enum;
     for (const EnumConstantDecl *ECD : Enum->enumerators())

diff --git a/clang-tools-extra/clang-tidy/utils/Matchers.h b/clang-tools-extra/clang-tidy/utils/Matchers.h
@@ -85,15 +85,7 @@ class MatchesAnyListedNameMatcher
         NameList.begin(), NameList.end(), std::back_inserter(NameMatchers),
         [](const llvm::StringRef Name) { return NameMatcher(Name); });
   }
-  bool matches(
-      const NamedDecl &Node, ast_matchers::internal::ASTMatchFinder *Finder,
-      ast_matchers::internal::BoundNodesTreeBuilder *Builder) const override {
-    return llvm::any_of(NameMatchers, [&Node](const NameMatcher &NM) {
-      return NM.match(Node);
-    });
-  }
 
-private:
   class NameMatcher {
     llvm::Regex Regex;
     enum class MatchMode {
@@ -136,6 +128,15 @@ class MatchesAnyListedNameMatcher
     }
   };
 
+  bool matches(
+      const NamedDecl &Node, ast_matchers::internal::ASTMatchFinder *Finder,
+      ast_matchers::internal::BoundNodesTreeBuilder *Builder) const override {
+    return llvm::any_of(NameMatchers, [&Node](const NameMatcher &NM) {
+      return NM.match(Node);
+    });
+  }
+
+private:
   std::vector<NameMatcher> NameMatchers;
 };
 

diff --git a/clang-tools-extra/clangd/AST.cpp b/clang-tools-extra/clangd/AST.cpp
@@ -187,7 +187,6 @@ std::string printQualifiedName(const NamedDecl &ND) {
   // In clangd, context is usually available and paths are mostly noise.
   Policy.AnonymousTagLocations = false;
   ND.printQualifiedName(OS, Policy);
-  OS.flush();
   assert(!StringRef(QName).starts_with("::"));
   return QName;
 }
@@ -270,7 +269,6 @@ std::string printTemplateSpecializationArgs(const NamedDecl &ND) {
     // location information.
     printTemplateArgumentList(OS, Cls->getTemplateArgs().asArray(), Policy);
   }
-  OS.flush();
   return TemplateArgs;
 }
 
@@ -303,7 +301,6 @@ std::string printObjCMethod(const ObjCMethodDecl &Method) {
     OS << ", ...";
 
   OS << ']';
-  OS.flush();
   return Name;
 }
 
@@ -314,15 +311,13 @@ std::string printObjCContainer(const ObjCContainerDecl &C) {
     const ObjCInterfaceDecl *Class = Category->getClassInterface();
     OS << getNameOrErrForObjCInterface(Class) << '(' << Category->getName()
        << ')';
-    OS.flush();
     return Name;
   }
   if (const ObjCCategoryImplDecl *CID = dyn_cast<ObjCCategoryImplDecl>(&C)) {
     std::string Name;
     llvm::raw_string_ostream OS(Name);
     const ObjCInterfaceDecl *Class = CID->getClassInterface();
     OS << getNameOrErrForObjCInterface(Class) << '(' << CID->getName() << ')';
-    OS.flush();
     return Name;
   }
   return C.getNameAsString();

diff --git a/clang-tools-extra/clangd/CMakeLists.txt b/clang-tools-extra/clangd/CMakeLists.txt
@@ -183,7 +183,6 @@ target_link_libraries(clangDaemon
   ${LLVM_PTHREAD_LIB}
 
   clangIncludeCleaner
-  clangPseudo
   clangTidy
   clangTidyUtils
 

diff --git a/clang-tools-extra/clangd/CodeComplete.cpp b/clang-tools-extra/clangd/CodeComplete.cpp
@@ -1409,6 +1409,9 @@ bool semaCodeComplete(std::unique_ptr<CodeCompleteConsumer> Consumer,
   Clang->getPreprocessorOpts().SingleFileParseMode = CompletingInPreamble;
   Clang->setCodeCompletionConsumer(Consumer.release());
 
+  if (Input.Preamble.RequiredModules)
+    Input.Preamble.RequiredModules->adjustHeaderSearchOptions(Clang->getHeaderSearchOpts());
+
   SyntaxOnlyAction Action;
   if (!Action.BeginSourceFile(*Clang, Clang->getFrontendOpts().Inputs[0])) {
     log("BeginSourceFile() failed when running codeComplete for {0}",
@@ -2122,7 +2125,7 @@ clang::CodeCompleteOptions CodeCompleteOptions::getClangCompleteOpts() const {
   // When an is used, Sema is responsible for completing the main file,
   // the index can provide results from the preamble.
   // Tell Sema not to deserialize the preamble to look for results.
-  Result.LoadExternal = !Index;
+  Result.LoadExternal = ForceLoadPreamble || !Index;
   Result.IncludeFixIts = IncludeFixIts;
 
   return Result;

diff --git a/clang-tools-extra/clangd/CodeComplete.h b/clang-tools-extra/clangd/CodeComplete.h
@@ -52,6 +52,11 @@ struct CodeCompleteOptions {
   /// For example, private members are usually inaccessible.
   bool IncludeIneligibleResults = false;
 
+  /// Force sema to load decls from preamble even if an index is provided.
+  /// This is helpful for cases the index can't provide symbols, e.g. with
+  /// experimental c++20 modules
+  bool ForceLoadPreamble = false;
+
   /// Combine overloads into a single completion item where possible.
   /// If none, the implementation may choose an appropriate behavior.
   /// (In practice, ClangdLSPServer enables bundling if the client claims

diff --git a/clang-tools-extra/clangd/Diagnostics.cpp b/clang-tools-extra/clangd/Diagnostics.cpp
@@ -319,7 +319,6 @@ std::string mainMessage(const Diag &D, const ClangdDiagnosticOptions &Opts) {
       OS << "\n\n";
       printDiag(OS, Note);
     }
-  OS.flush();
   return capitalize(std::move(Result));
 }
 
@@ -335,7 +334,6 @@ std::string noteMessage(const Diag &Main, const DiagBase &Note,
     OS << "\n\n";
     printDiag(OS, Main);
   }
-  OS.flush();
   return capitalize(std::move(Result));
 }
 
@@ -579,17 +577,7 @@ std::vector<Diag> StoreDiags::take(const clang::tidy::ClangTidyContext *Tidy) {
   for (auto &Diag : Output) {
     if (const char *ClangDiag = getDiagnosticCode(Diag.ID)) {
       // Warnings controlled by -Wfoo are better recognized by that name.
-      const StringRef Warning = [&] {
-        if (OrigSrcMgr) {
-          return OrigSrcMgr->getDiagnostics()
-              .getDiagnosticIDs()
-              ->getWarningOptionForDiag(Diag.ID);
-        }
-        if (!DiagnosticIDs::IsCustomDiag(Diag.ID))
-          return DiagnosticIDs{}.getWarningOptionForDiag(Diag.ID);
-        return StringRef{};
-      }();
-
+      StringRef Warning = DiagnosticIDs::getWarningOptionForDiag(Diag.ID);
       if (!Warning.empty()) {
         Diag.Name = ("-W" + Warning).str();
       } else {
@@ -906,23 +894,20 @@ void StoreDiags::flushLastDiag() {
   Output.push_back(std::move(*LastDiag));
 }
 
-bool isDiagnosticSuppressed(const clang::Diagnostic &Diag,
-                            const llvm::StringSet<> &Suppress,
-                            const LangOptions &LangOpts) {
+bool isBuiltinDiagnosticSuppressed(unsigned ID,
+                                   const llvm::StringSet<> &Suppress,
+                                   const LangOptions &LangOpts) {
   // Don't complain about header-only stuff in mainfiles if it's a header.
   // FIXME: would be cleaner to suppress in clang, once we decide whether the
   //        behavior should be to silently-ignore or respect the pragma.
-  if (Diag.getID() == diag::pp_pragma_sysheader_in_main_file &&
-      LangOpts.IsHeaderFile)
+  if (ID == diag::pp_pragma_sysheader_in_main_file && LangOpts.IsHeaderFile)
     return true;
 
-  if (const char *CodePtr = getDiagnosticCode(Diag.getID())) {
+  if (const char *CodePtr = getDiagnosticCode(ID)) {
     if (Suppress.contains(normalizeSuppressedCode(CodePtr)))
       return true;
   }
-  StringRef Warning =
-      Diag.getDiags()->getDiagnosticIDs()->getWarningOptionForDiag(
-          Diag.getID());
+  StringRef Warning = DiagnosticIDs::getWarningOptionForDiag(ID);
   if (!Warning.empty() && Suppress.contains(Warning))
     return true;
   return false;

diff --git a/clang-tools-extra/clangd/Diagnostics.h b/clang-tools-extra/clangd/Diagnostics.h
@@ -181,11 +181,11 @@ class StoreDiags : public DiagnosticConsumer {
 };
 
 /// Determine whether a (non-clang-tidy) diagnostic is suppressed by config.
-bool isDiagnosticSuppressed(const clang::Diagnostic &Diag,
-                            const llvm::StringSet<> &Suppressed,
-                            const LangOptions &);
+bool isBuiltinDiagnosticSuppressed(unsigned ID,
+                                   const llvm::StringSet<> &Suppressed,
+                                   const LangOptions &);
 /// Take a user-specified diagnostic code, and convert it to a normalized form
-/// stored in the config and consumed by isDiagnosticsSuppressed.
+/// stored in the config and consumed by isBuiltinDiagnosticsSuppressed.
 ///
 /// (This strips err_ and -W prefix so we can match with or without them.)
 llvm::StringRef normalizeSuppressedCode(llvm::StringRef);

diff --git a/clang-tools-extra/clangd/FindSymbols.cpp b/clang-tools-extra/clangd/FindSymbols.cpp
@@ -182,7 +182,6 @@ std::string getSymbolName(ASTContext &Ctx, const NamedDecl &ND) {
     OS << (Method->isInstanceMethod() ? '-' : '+');
     Method->getSelector().print(OS);
 
-    OS.flush();
     return Name;
   }
   return printName(Ctx, ND);

diff --git a/clang-tools-extra/clangd/Hover.cpp b/clang-tools-extra/clangd/Hover.cpp
@@ -150,7 +150,6 @@ std::string printDefinition(const Decl *D, PrintingPolicy PP,
   std::string Definition;
   llvm::raw_string_ostream OS(Definition);
   D->print(OS, PP);
-  OS.flush();
   return Definition;
 }
 
@@ -179,7 +178,6 @@ HoverInfo::PrintedType printType(QualType QT, ASTContext &ASTCtx,
       OS << TT->getDecl()->getKindName() << " ";
   }
   QT.print(OS, PP);
-  OS.flush();
 
   const Config &Cfg = Config::current();
   if (!QT.isNull() && Cfg.Hover.ShowAKA) {
@@ -229,7 +227,6 @@ HoverInfo::PrintedType printType(const TemplateTemplateParmDecl *TTP,
   // FIXME: TemplateTemplateParameter doesn't store the info on whether this
   // param was a "typename" or "class".
   OS << "> class";
-  OS.flush();
   return Result;
 }
 
@@ -821,7 +818,6 @@ std::string typeAsDefinition(const HoverInfo::PrintedType &PType) {
   OS << PType.Type;
   if (PType.AKA)
     OS << " // aka: " << *PType.AKA;
-  OS.flush();
   return Result;
 }
 

diff --git a/clang-tools-extra/clangd/ParsedAST.cpp b/clang-tools-extra/clangd/ParsedAST.cpp
@@ -280,6 +280,8 @@ class TidyDiagnosticGroups {
     llvm::StringRef Check;
     while (!Checks.empty()) {
       std::tie(Check, Checks) = Checks.split(',');
+      Check = Check.trim();
+
       if (Check.empty())
         continue;
 
@@ -340,7 +342,7 @@ void applyWarningOptions(llvm::ArrayRef<std::string> ExtraArgs,
       if (Enable) {
         if (Diags.getDiagnosticLevel(ID, SourceLocation()) <
             DiagnosticsEngine::Warning) {
-          auto Group = Diags.getDiagnosticIDs()->getGroupForDiag(ID);
+          auto Group = DiagnosticIDs::getGroupForDiag(ID);
           if (!Group || !EnabledGroups(*Group))
             continue;
           Diags.setSeverity(ID, diag::Severity::Warning, SourceLocation());
@@ -583,8 +585,8 @@ ParsedAST::build(llvm::StringRef Filename, const ParseInputs &Inputs,
     ASTDiags.setLevelAdjuster([&](DiagnosticsEngine::Level DiagLevel,
                                   const clang::Diagnostic &Info) {
       if (Cfg.Diagnostics.SuppressAll ||
-          isDiagnosticSuppressed(Info, Cfg.Diagnostics.Suppress,
-                                 Clang->getLangOpts()))
+          isBuiltinDiagnosticSuppressed(Info.getID(), Cfg.Diagnostics.Suppress,
+                                        Clang->getLangOpts()))
         return DiagnosticsEngine::Ignored;
 
       auto It = OverriddenSeverity.find(Info.getID());

diff --git a/clang-tools-extra/clangd/Preamble.cpp b/clang-tools-extra/clangd/Preamble.cpp
@@ -621,8 +621,8 @@ buildPreamble(PathRef FileName, CompilerInvocation CI,
   PreambleDiagnostics.setLevelAdjuster([&](DiagnosticsEngine::Level DiagLevel,
                                            const clang::Diagnostic &Info) {
     if (Cfg.Diagnostics.SuppressAll ||
-        isDiagnosticSuppressed(Info, Cfg.Diagnostics.Suppress,
-                               CI.getLangOpts()))
+        isBuiltinDiagnosticSuppressed(Info.getID(), Cfg.Diagnostics.Suppress,
+                                      CI.getLangOpts()))
       return DiagnosticsEngine::Ignored;
     switch (Info.getID()) {
     case diag::warn_no_newline_eof:
@@ -913,7 +913,6 @@ PreamblePatch PreamblePatch::create(llvm::StringRef FileName,
   PP.PatchedMarks = std::move(ModifiedScan->Marks);
   PP.PatchedMacros = std::move(ModifiedScan->Macros);
   dlog("Created preamble patch: {0}", Patch.str());
-  Patch.flush();
   return PP;
 }
 

diff --git a/clang-tools-extra/clangd/Quality.cpp b/clang-tools-extra/clangd/Quality.cpp
@@ -554,7 +554,6 @@ std::string sortText(float Score, llvm::StringRef Name) {
   llvm::write_hex(OS, encodeFloat(-Score), llvm::HexPrintStyle::Lower,
                   /*Width=*/2 * sizeof(Score));
   OS << Name;
-  OS.flush();
   return S;
 }
 

diff --git a/clang-tools-extra/clangd/SemanticSelection.cpp b/clang-tools-extra/clangd/SemanticSelection.cpp
@@ -11,9 +11,6 @@
 #include "Protocol.h"
 #include "Selection.h"
 #include "SourceCode.h"
-#include "clang-pseudo/Bracket.h"
-#include "clang-pseudo/DirectiveTree.h"
-#include "clang-pseudo/Token.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/SourceManager.h"
@@ -25,6 +22,9 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
+#include "support/Bracket.h"
+#include "support/DirectiveTree.h"
+#include "support/Token.h"
 #include <optional>
 #include <queue>
 #include <vector>
@@ -181,16 +181,16 @@ llvm::Expected<std::vector<FoldingRange>> getFoldingRanges(ParsedAST &AST) {
 // Related issue: https://github.com/clangd/clangd/issues/310
 llvm::Expected<std::vector<FoldingRange>>
 getFoldingRanges(const std::string &Code, bool LineFoldingOnly) {
-  auto OrigStream = pseudo::lex(Code, clang::pseudo::genericLangOpts());
+  auto OrigStream = lex(Code, genericLangOpts());
 
-  auto DirectiveStructure = pseudo::DirectiveTree::parse(OrigStream);
-  pseudo::chooseConditionalBranches(DirectiveStructure, OrigStream);
+  auto DirectiveStructure = DirectiveTree::parse(OrigStream);
+  chooseConditionalBranches(DirectiveStructure, OrigStream);
 
   // FIXME: Provide ranges in the disabled-PP regions as well.
   auto Preprocessed = DirectiveStructure.stripDirectives(OrigStream);
 
-  auto ParseableStream = cook(Preprocessed, clang::pseudo::genericLangOpts());
-  pseudo::pairBrackets(ParseableStream);
+  auto ParseableStream = cook(Preprocessed, genericLangOpts());
+  pairBrackets(ParseableStream);
 
   std::vector<FoldingRange> Result;
   auto AddFoldingRange = [&](Position Start, Position End,
@@ -205,19 +205,19 @@ getFoldingRanges(const std::string &Code, bool LineFoldingOnly) {
     FR.kind = Kind.str();
     Result.push_back(FR);
   };
-  auto OriginalToken = [&](const pseudo::Token &T) {
+  auto OriginalToken = [&](const Token &T) {
     return OrigStream.tokens()[T.OriginalIndex];
   };
-  auto StartOffset = [&](const pseudo::Token &T) {
+  auto StartOffset = [&](const Token &T) {
     return OriginalToken(T).text().data() - Code.data();
   };
-  auto StartPosition = [&](const pseudo::Token &T) {
+  auto StartPosition = [&](const Token &T) {
     return offsetToPosition(Code, StartOffset(T));
   };
-  auto EndOffset = [&](const pseudo::Token &T) {
+  auto EndOffset = [&](const Token &T) {
     return StartOffset(T) + OriginalToken(T).Length;
   };
-  auto EndPosition = [&](const pseudo::Token &T) {
+  auto EndPosition = [&](const Token &T) {
     return offsetToPosition(Code, EndOffset(T));
   };
   auto Tokens = ParseableStream.tokens();
@@ -235,7 +235,7 @@ getFoldingRanges(const std::string &Code, bool LineFoldingOnly) {
       }
     }
   }
-  auto IsBlockComment = [&](const pseudo::Token &T) {
+  auto IsBlockComment = [&](const Token &T) {
     assert(T.Kind == tok::comment);
     return OriginalToken(T).Length >= 2 &&
            Code.substr(StartOffset(T), 2) == "/*";
@@ -246,10 +246,10 @@ getFoldingRanges(const std::string &Code, bool LineFoldingOnly) {
       T++;
       continue;
     }
-    pseudo::Token *FirstComment = T;
+    Token *FirstComment = T;
     // Show starting sentinals (// and /*) of the comment.
     Position Start = offsetToPosition(Code, 2 + StartOffset(*FirstComment));
-    pseudo::Token *LastComment = T;
+    Token *LastComment = T;
     Position End = EndPosition(*T);
     while (T != Tokens.end() && T->Kind == tok::comment &&
            StartPosition(*T).line <= End.line + 1) {

diff --git a/clang-tools-extra/clangd/SourceCode.cpp b/clang-tools-extra/clangd/SourceCode.cpp
@@ -814,8 +814,8 @@ llvm::SmallVector<llvm::StringRef> ancestorNamespaces(llvm::StringRef NS) {
 
 // Checks whether \p FileName is a valid spelling of main file.
 bool isMainFile(llvm::StringRef FileName, const SourceManager &SM) {
-  auto FE = SM.getFileManager().getFile(FileName);
-  return FE && *FE == SM.getFileEntryForID(SM.getMainFileID());
+  auto FE = SM.getFileManager().getOptionalFileRef(FileName);
+  return FE && FE == SM.getFileEntryRefForID(SM.getMainFileID());
 }
 
 } // namespace

diff --git a/clang-tools-extra/clangd/SystemIncludeExtractor.cpp b/clang-tools-extra/clangd/SystemIncludeExtractor.cpp
@@ -483,7 +483,6 @@ std::string convertGlobToRegex(llvm::StringRef Glob) {
     }
   }
   RegStream << '$';
-  RegStream.flush();
   return RegText;
 }
 

diff --git a/clang-tools-extra/clangd/index/StdLib.cpp b/clang-tools-extra/clangd/index/StdLib.cpp
@@ -87,7 +87,6 @@ std::string buildUmbrella(llvm::StringLiteral Mandatory,
                         "#endif\n",
                         Header);
   }
-  OS.flush();
   return Result;
 }
 

diff --git a/clang-tools-extra/clangd/index/Symbol.h b/clang-tools-extra/clangd/index/Symbol.h
@@ -145,9 +145,11 @@ struct Symbol {
     ImplementationDetail = 1 << 2,
     /// Symbol is visible to other files (not e.g. a static helper function).
     VisibleOutsideFile = 1 << 3,
+    /// Symbol has an attached documentation comment.
+    HasDocComment = 1 << 4
   };
-
   SymbolFlag Flags = SymbolFlag::None;
+
   /// FIXME: also add deprecation message and fixit?
 };
 

diff --git a/clang-tools-extra/clangd/index/SymbolCollector.cpp b/clang-tools-extra/clangd/index/SymbolCollector.cpp
@@ -41,6 +41,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
@@ -75,18 +76,62 @@ bool isPrivateProtoDecl(const NamedDecl &ND) {
   if (ND.getIdentifier() == nullptr)
     return false;
   auto Name = ND.getIdentifier()->getName();
-  if (!Name.contains('_'))
-    return false;
-  // Nested proto entities (e.g. Message::Nested) have top-level decls
-  // that shouldn't be used (Message_Nested). Ignore them completely.
-  // The nested entities are dangling type aliases, we may want to reconsider
-  // including them in the future.
-  // For enum constants, SOME_ENUM_CONSTANT is not private and should be
-  // indexed. Outer_INNER is private. This heuristic relies on naming style, it
-  // will include OUTER_INNER and exclude some_enum_constant.
-  // FIXME: the heuristic relies on naming style (i.e. no underscore in
-  // user-defined names) and can be improved.
-  return (ND.getKind() != Decl::EnumConstant) || llvm::any_of(Name, islower);
+  // There are some internal helpers like _internal_set_foo();
+  if (Name.contains("_internal_"))
+    return true;
+
+  // https://protobuf.dev/reference/cpp/cpp-generated/#nested-types
+  // Nested entities (messages/enums) has two names, one at the top-level scope,
+  // with a mangled name created by prepending all the outer types. These names
+  // are almost never preferred by the developers, so exclude them from index.
+  // e.g.
+  //   message Foo {
+  //    message Bar {}
+  //    enum E { A }
+  //   }
+  //
+  // yields:
+  //   class Foo_Bar {};
+  //   enum Foo_E { Foo_E_A };
+  //   class Foo {
+  //    using Bar = Foo_Bar;
+  //    static constexpr Foo_E A = Foo_E_A;
+  //   };
+
+  // We get rid of Foo_Bar and Foo_E by discarding any top-level entries with
+  // `_` in the name. This relies on original message/enum not having `_` in the
+  // name. Hence might go wrong in certain cases.
+  if (ND.getDeclContext()->isNamespace()) {
+    // Strip off some known public suffix helpers for enums, rest of the helpers
+    // are generated inside record decls so we don't care.
+    // https://protobuf.dev/reference/cpp/cpp-generated/#enum
+    Name.consume_back("_descriptor");
+    Name.consume_back("_IsValid");
+    Name.consume_back("_Name");
+    Name.consume_back("_Parse");
+    Name.consume_back("_MIN");
+    Name.consume_back("_MAX");
+    Name.consume_back("_ARRAYSIZE");
+    return Name.contains('_');
+  }
+
+  // EnumConstantDecls need some special attention, despite being nested in a
+  // TagDecl, they might still have mangled names. We filter those by checking
+  // if it has parent's name as a prefix.
+  // This might go wrong if a nested entity has a name that starts with parent's
+  // name, e.g: enum Foo { Foo_X }.
+  if (llvm::isa<EnumConstantDecl>(&ND)) {
+    auto *DC = llvm::cast<EnumDecl>(ND.getDeclContext());
+    if (!DC || !DC->getIdentifier())
+      return false;
+    auto CtxName = DC->getIdentifier()->getName();
+    return !CtxName.empty() && Name.consume_front(CtxName) &&
+           Name.consume_front("_");
+  }
+
+  // Now we're only left with fields/methods without an `_internal_` in the
+  // name, they're intended for public use.
+  return false;
 }
 
 // We only collect #include paths for symbols that are suitable for global code
@@ -635,17 +680,21 @@ bool SymbolCollector::handleDeclOccurrence(
     return true;
 
   const Symbol *BasicSymbol = Symbols.find(ID);
-  if (isPreferredDeclaration(*OriginalDecl, Roles))
+  bool SkipDocCheckInDef = false;
+  if (isPreferredDeclaration(*OriginalDecl, Roles)) {
     // If OriginalDecl is preferred, replace/create the existing canonical
     // declaration (e.g. a class forward declaration). There should be at most
     // one duplicate as we expect to see only one preferred declaration per
     // TU, because in practice they are definitions.
     BasicSymbol = addDeclaration(*OriginalDecl, std::move(ID), IsMainFileOnly);
-  else if (!BasicSymbol || DeclIsCanonical)
+    SkipDocCheckInDef = true;
+  } else if (!BasicSymbol || DeclIsCanonical) {
     BasicSymbol = addDeclaration(*ND, std::move(ID), IsMainFileOnly);
+    SkipDocCheckInDef = true;
+  }
 
   if (Roles & static_cast<unsigned>(index::SymbolRole::Definition))
-    addDefinition(*OriginalDecl, *BasicSymbol);
+    addDefinition(*OriginalDecl, *BasicSymbol, SkipDocCheckInDef);
 
   return true;
 }
@@ -1025,16 +1074,28 @@ const Symbol *SymbolCollector::addDeclaration(const NamedDecl &ND, SymbolID ID,
       *ASTCtx, *PP, CodeCompletionContext::CCC_Symbol, *CompletionAllocator,
       *CompletionTUInfo,
       /*IncludeBriefComments*/ false);
-  std::string Documentation =
-      formatDocumentation(*CCS, getDocComment(Ctx, SymbolCompletion,
-                                              /*CommentsFromHeaders=*/true));
+  std::string DocComment;
+  std::string Documentation;
+  bool AlreadyHasDoc = S.Flags & Symbol::HasDocComment;
+  if (!AlreadyHasDoc) {
+    DocComment = getDocComment(Ctx, SymbolCompletion,
+                               /*CommentsFromHeaders=*/true);
+    Documentation = formatDocumentation(*CCS, DocComment);
+  }
+  const auto UpdateDoc = [&] {
+    if (!AlreadyHasDoc) {
+      if (!DocComment.empty())
+        S.Flags |= Symbol::HasDocComment;
+      S.Documentation = Documentation;
+    }
+  };
   if (!(S.Flags & Symbol::IndexedForCodeCompletion)) {
     if (Opts.StoreAllDocumentation)
-      S.Documentation = Documentation;
+      UpdateDoc();
     Symbols.insert(S);
     return Symbols.find(S.ID);
   }
-  S.Documentation = Documentation;
+  UpdateDoc();
   std::string Signature;
   std::string SnippetSuffix;
   getSignature(*CCS, &Signature, &SnippetSuffix, SymbolCompletion.Kind,
@@ -1058,8 +1119,8 @@ const Symbol *SymbolCollector::addDeclaration(const NamedDecl &ND, SymbolID ID,
   return Symbols.find(S.ID);
 }
 
-void SymbolCollector::addDefinition(const NamedDecl &ND,
-                                    const Symbol &DeclSym) {
+void SymbolCollector::addDefinition(const NamedDecl &ND, const Symbol &DeclSym,
+                                    bool SkipDocCheck) {
   if (DeclSym.Definition)
     return;
   const auto &SM = ND.getASTContext().getSourceManager();
@@ -1074,6 +1135,27 @@ void SymbolCollector::addDefinition(const NamedDecl &ND,
   Symbol S = DeclSym;
   // FIXME: use the result to filter out symbols.
   S.Definition = *DefLoc;
+
+  std::string DocComment;
+  std::string Documentation;
+  if (!SkipDocCheck && !(S.Flags & Symbol::HasDocComment) &&
+      (llvm::isa<FunctionDecl>(ND) || llvm::isa<CXXMethodDecl>(ND))) {
+    CodeCompletionResult SymbolCompletion(&getTemplateOrThis(ND), 0);
+    const auto *CCS = SymbolCompletion.CreateCodeCompletionString(
+        *ASTCtx, *PP, CodeCompletionContext::CCC_Symbol, *CompletionAllocator,
+        *CompletionTUInfo,
+        /*IncludeBriefComments*/ false);
+    DocComment = getDocComment(ND.getASTContext(), SymbolCompletion,
+                               /*CommentsFromHeaders=*/true);
+    if (!S.Documentation.empty())
+      Documentation = S.Documentation.str() + '\n' + DocComment;
+    else
+      Documentation = formatDocumentation(*CCS, DocComment);
+    if (!DocComment.empty())
+      S.Flags |= Symbol::HasDocComment;
+    S.Documentation = Documentation;
+  }
+
   Symbols.insert(S);
 }
 

diff --git a/clang-tools-extra/clangd/index/SymbolCollector.h b/clang-tools-extra/clangd/index/SymbolCollector.h
@@ -161,7 +161,8 @@ class SymbolCollector : public index::IndexDataConsumer {
 private:
   const Symbol *addDeclaration(const NamedDecl &, SymbolID,
                                bool IsMainFileSymbol);
-  void addDefinition(const NamedDecl &, const Symbol &DeclSymbol);
+  void addDefinition(const NamedDecl &, const Symbol &DeclSymbol,
+                     bool SkipDocCheck);
   void processRelations(const NamedDecl &ND, const SymbolID &ID,
                         ArrayRef<index::SymbolRelation> Relations);
 

diff --git a/clang-tools-extra/pseudo/lib/Bracket.cpp → clang-tools-extra/clangd/support/Bracket.cpp b/clang-tools-extra/pseudo/lib/Bracket.cpp → clang-tools-extra/clangd/support/Bracket.cpp
@@ -62,10 +62,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang-pseudo/Bracket.h"
+#include "Bracket.h"
 
 namespace clang {
-namespace pseudo {
+namespace clangd {
 namespace {
 
 struct Bracket {
@@ -83,7 +83,7 @@ struct Bracket {
 // Find brackets in the stream and convert to Bracket struct.
 std::vector<Bracket> findBrackets(const TokenStream &Stream) {
   std::vector<Bracket> Brackets;
-  auto Add = [&](const pseudo::Token &Tok, Bracket::BracketKind K,
+  auto Add = [&](const Token &Tok, Bracket::BracketKind K,
                  Bracket::Direction D) {
     Brackets.push_back(
         {K, D, Tok.Line, Tok.Indent, Stream.index(Tok), Bracket::None});
@@ -151,5 +151,5 @@ void pairBrackets(TokenStream &Stream) {
   applyPairings(Brackets, Stream);
 }
 
-} // namespace pseudo
+} // namespace clangd
 } // namespace clang
diff --git a/...tra/pseudo/include/clang-pseudo/Bracket.h → clang-tools-extra/clangd/support/Bracket.h b/...tra/pseudo/include/clang-pseudo/Bracket.h → clang-tools-extra/clangd/support/Bracket.h
@@ -23,19 +23,19 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef CLANG_PSEUDO_BRACKET_H
-#define CLANG_PSEUDO_BRACKET_H
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_BRACKET_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_BRACKET_H
 
-#include "clang-pseudo/Token.h"
+#include "Token.h"
 
 namespace clang {
-namespace pseudo {
+namespace clangd {
 
 /// Identifies bracket token in the stream which should be paired.
 /// Sets Token::Pair accordingly.
 void pairBrackets(TokenStream &);
 
-} // namespace pseudo
+} // namespace clangd
 } // namespace clang
 
-#endif
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_BRACKET_H
diff --git a/clang-tools-extra/clangd/support/CMakeLists.txt b/clang-tools-extra/clangd/support/CMakeLists.txt
@@ -16,9 +16,12 @@ if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB OR NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
 endif()
 
 add_clang_library(clangdSupport
+  Bracket.cpp
   Cancellation.cpp
   Context.cpp
+  DirectiveTree.cpp
   FileCache.cpp
+  Lex.cpp
   Logger.cpp
   Markup.cpp
   MemoryTree.cpp
@@ -27,9 +30,16 @@ add_clang_library(clangdSupport
   ThreadCrashReporter.cpp
   Threading.cpp
   ThreadsafeFS.cpp
+  Token.cpp
   Trace.cpp
 
   LINK_LIBS
   ${LLVM_PTHREAD_LIB}
   ${CLANGD_ATOMIC_LIB}
   )
+
+clang_target_link_libraries(clangdSupport
+  PRIVATE
+  clangBasic
+  clangLex
+  )
diff --git a/...-tools-extra/pseudo/lib/DirectiveTree.cpp → ...ls-extra/clangd/support/DirectiveTree.cpp b/...-tools-extra/pseudo/lib/DirectiveTree.cpp → ...ls-extra/clangd/support/DirectiveTree.cpp
@@ -6,15 +6,15 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang-pseudo/DirectiveTree.h"
+#include "DirectiveTree.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/TokenKinds.h"
 #include "llvm/Support/FormatVariadic.h"
 #include <optional>
 #include <variant>
 
 namespace clang {
-namespace pseudo {
+namespace clangd {
 namespace {
 
 class DirectiveParser {
@@ -353,5 +353,5 @@ TokenStream DirectiveTree::stripDirectives(const TokenStream &In) const {
   return Out;
 }
 
-} // namespace pseudo
+} // namespace clangd
 } // namespace clang
diff --git a/...eudo/include/clang-pseudo/DirectiveTree.h → ...ools-extra/clangd/support/DirectiveTree.h b/...eudo/include/clang-pseudo/DirectiveTree.h → ...ools-extra/clangd/support/DirectiveTree.h
@@ -25,17 +25,17 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef CLANG_PSEUDO_DIRECTIVETREE_H
-#define CLANG_PSEUDO_DIRECTIVETREE_H
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_DIRECTIVETREE_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_DIRECTIVETREE_H
 
-#include "clang-pseudo/Token.h"
+#include "Token.h"
 #include "clang/Basic/TokenKinds.h"
 #include <optional>
 #include <variant>
 #include <vector>
 
 namespace clang {
-namespace pseudo {
+namespace clangd {
 
 /// Describes the structure of a source file, as seen by the preprocessor.
 ///
@@ -124,7 +124,7 @@ llvm::raw_ostream &operator<<(llvm::raw_ostream &,
 /// The choices are stored in Conditional::Taken nodes.
 void chooseConditionalBranches(DirectiveTree &, const TokenStream &Code);
 
-} // namespace pseudo
+} // namespace clangd
 } // namespace clang
 
-#endif // CLANG_PSEUDO_DIRECTIVETREE_H
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_DIRECTIVETREE_H
-Original file line number
+Diff line change
@@ Expand Up / @@ -483,7 +483,6 @@ std::string convertGlobToRegex(llvm::StringRef Glob) { @@
         }
       }
       RegStream << '$';
-      RegStream.flush();
       return RegText;
     }
@@ Expand Down @@