diff --git a/lib/DriverTool/sil_llvm_gen_main.cpp b/lib/DriverTool/sil_llvm_gen_main.cpp
index 9bc9a2debe961..6acb9fd1d9fee 100644
--- a/lib/DriverTool/sil_llvm_gen_main.cpp
+++ b/lib/DriverTool/sil_llvm_gen_main.cpp
@@ -22,6 +22,7 @@
 #include "swift/AST/SILOptions.h"
 #include "swift/Basic/Assertions.h"
 #include "swift/Basic/LLVMInitialize.h"
+#include "swift/Basic/QuotedString.h"
 #include "swift/Frontend/DiagnosticVerifier.h"
 #include "swift/Frontend/Frontend.h"
 #include "swift/Frontend/PrintingDiagnosticConsumer.h"
@@ -49,6 +50,29 @@
 #include <cstdio>
 using namespace swift;
 
+namespace {
+enum class SILOptStrictConcurrency {
+  None = 0,
+  Complete,
+  Targeted,
+  Minimal,
+};
+}
+
+static std::optional<StrictConcurrency>
+convertSILOptToRawStrictConcurrencyLevel(SILOptStrictConcurrency level) {
+  switch (level) {
+  case SILOptStrictConcurrency::None:
+    return {};
+  case SILOptStrictConcurrency::Complete:
+    return StrictConcurrency::Complete;
+  case SILOptStrictConcurrency::Targeted:
+    return StrictConcurrency::Targeted;
+  case SILOptStrictConcurrency::Minimal:
+    return StrictConcurrency::Minimal;
+  }
+}
+
 struct SILLLVMGenOptions {
   llvm::cl::opt<std::string>
     InputFilename = llvm::cl::opt<std::string>(llvm::cl::desc("input file"),
@@ -66,12 +90,29 @@ struct SILLLVMGenOptions {
     FrameworkPaths = llvm::cl::list<std::string>(
       "F", llvm::cl::desc("add a directory to the framework search path"));
 
+  llvm::cl::list<std::string> VFSOverlays = llvm::cl::list<std::string>(
+      "vfsoverlay", llvm::cl::desc("add a VFS overlay"));
+
   llvm::cl::opt<std::string>
     ModuleName = llvm::cl::opt<std::string>("module-name",
                  llvm::cl::desc("The name of the module if processing"
                                 " a module. Necessary for processing "
                                 "stdin."));
 
+  llvm::cl::opt<bool> StrictImplicitModuleContext = llvm::cl::opt<bool>(
+      "strict-implicit-module-context",
+      llvm::cl::desc("Enable the strict forwarding of compilation "
+                     "context to downstream implicit module dependencies"));
+
+  llvm::cl::opt<bool> DisableImplicitModules =
+      llvm::cl::opt<bool>("disable-implicit-swift-modules",
+                          llvm::cl::desc("Disable implicit swift modules."));
+
+  llvm::cl::opt<std::string> ExplicitSwiftModuleMapPath =
+      llvm::cl::opt<std::string>(
+          "explicit-swift-module-map-file",
+          llvm::cl::desc("Explict swift module map file path"));
+
   llvm::cl::opt<std::string>
     ResourceDir = llvm::cl::opt<std::string>(
       "resource-dir",
@@ -96,27 +137,94 @@ struct SILLLVMGenOptions {
   llvm::cl::opt<bool>
     PerformWMO = llvm::cl::opt<bool>("wmo", llvm::cl::desc("Enable whole-module optimizations"));
 
-  llvm::cl::opt<IRGenOutputKind>
-    OutputKind = llvm::cl::opt<IRGenOutputKind>(
+  llvm::cl::opt<IRGenOutputKind> OutputKind = llvm::cl::opt<IRGenOutputKind>(
       "output-kind", llvm::cl::desc("Type of output to produce"),
-      llvm::cl::values(clEnumValN(IRGenOutputKind::LLVMAssemblyAfterOptimization,
-                                  "llvm-as", "Emit llvm assembly"),
-                       clEnumValN(IRGenOutputKind::LLVMBitcode, "llvm-bc",
-                                  "Emit llvm bitcode"),
-                       clEnumValN(IRGenOutputKind::NativeAssembly, "as",
-                                  "Emit native assembly"),
-                       clEnumValN(IRGenOutputKind::ObjectFile, "object",
-                                  "Emit an object file")),
+      llvm::cl::values(
+          clEnumValN(IRGenOutputKind::LLVMAssemblyBeforeOptimization, "llvm-as",
+                     "Emit llvm assembly before optimization"),
+          clEnumValN(IRGenOutputKind::LLVMAssemblyAfterOptimization,
+                     "llvm-as-opt", "Emit llvm assembly after optimization"),
+          clEnumValN(IRGenOutputKind::LLVMBitcode, "llvm-bc",
+                     "Emit llvm bitcode"),
+          clEnumValN(IRGenOutputKind::NativeAssembly, "as",
+                     "Emit native assembly"),
+          clEnumValN(IRGenOutputKind::ObjectFile, "object",
+                     "Emit an object file")),
       llvm::cl::init(IRGenOutputKind::ObjectFile));
 
   llvm::cl::opt<bool>
     DisableLegacyTypeInfo = llvm::cl::opt<bool>("disable-legacy-type-info",
           llvm::cl::desc("Don't try to load backward deployment layouts"));
+
+  llvm::cl::opt<std::string> SwiftVersionString = llvm::cl::opt<std::string>(
+      "swift-version",
+      llvm::cl::desc(
+          "The swift version to assume AST declarations correspond to"));
+
+  llvm::cl::opt<bool> EnableExperimentalConcurrency = llvm::cl::opt<bool>(
+      "enable-experimental-concurrency",
+      llvm::cl::desc("Enable experimental concurrency model."));
+
+  llvm::cl::opt<llvm::cl::boolOrDefault> EnableExperimentalMoveOnly =
+      llvm::cl::opt<llvm::cl::boolOrDefault>(
+          "enable-experimental-move-only", llvm::cl::init(llvm::cl::BOU_UNSET),
+          llvm::cl::desc("Enable experimental move-only semantics."));
+
+  llvm::cl::list<std::string> ExperimentalFeatures =
+      llvm::cl::list<std::string>(
+          "enable-experimental-feature",
+          llvm::cl::desc("Enable the given experimental feature."));
+
+  llvm::cl::list<std::string> UpcomingFeatures = llvm::cl::list<std::string>(
+      "enable-upcoming-feature",
+      llvm::cl::desc("Enable the given upcoming feature."));
+
+  llvm::cl::opt<bool> EnableCxxInterop = llvm::cl::opt<bool>(
+      "enable-experimental-cxx-interop", llvm::cl::desc("Enable C++ interop."),
+      llvm::cl::init(false));
+
+  llvm::cl::opt<bool> EnableObjCInterop = llvm::cl::opt<bool>(
+      "enable-objc-interop",
+      llvm::cl::desc("Enable Objective-C interoperability."));
+
+  llvm::cl::opt<bool> DisableObjCInterop = llvm::cl::opt<bool>(
+      "disable-objc-interop",
+      llvm::cl::desc("Disable Objective-C interoperability."));
+
+  // Strict Concurrency
+  llvm::cl::opt<SILOptStrictConcurrency> StrictConcurrencyLevel =
+      llvm::cl::opt<SILOptStrictConcurrency>(
+          "strict-concurrency", llvm::cl::desc("strict concurrency level"),
+          llvm::cl::init(SILOptStrictConcurrency::None),
+          llvm::cl::values(
+              clEnumValN(SILOptStrictConcurrency::Complete, "complete",
+                         "Enable complete strict concurrency"),
+              clEnumValN(SILOptStrictConcurrency::Targeted, "targeted",
+                         "Enable targeted strict concurrency"),
+              clEnumValN(SILOptStrictConcurrency::Minimal, "minimal",
+                         "Enable minimal strict concurrency"),
+              clEnumValN(SILOptStrictConcurrency::None, "disabled",
+                         "Strict concurrency disabled")));
 };
 
+static std::optional<bool> toOptionalBool(llvm::cl::boolOrDefault defaultable) {
+  switch (defaultable) {
+  case llvm::cl::BOU_TRUE:
+    return true;
+  case llvm::cl::BOU_FALSE:
+    return false;
+  case llvm::cl::BOU_UNSET:
+    return std::nullopt;
+  }
+  llvm_unreachable("Bad case for llvm::cl::boolOrDefault!");
+}
+
 int sil_llvm_gen_main(ArrayRef<const char *> argv, void *MainAddr) {
   INITIALIZE_LLVM();
 
+  llvm::setBugReportMsg(SWIFT_CRASH_BUG_REPORT_MESSAGE "\n");
+  llvm::EnablePrettyStackTraceOnSigInfoForThisThread();
+
   SILLLVMGenOptions options;
 
   llvm::cl::ParseCommandLineOptions(argv.size(), argv.data(), "Swift LLVM IR Generator\n");
@@ -139,6 +247,9 @@ int sil_llvm_gen_main(ArrayRef<const char *> argv, void *MainAddr) {
     FramePaths.push_back({path, /*isSystem=*/false});
   }
   Invocation.setFrameworkSearchPaths(FramePaths);
+
+  Invocation.setVFSOverlays(options.VFSOverlays);
+
   // Set the SDK path and target if given.
   if (options.SDKPath.getNumOccurrences() == 0) {
     const char *SDKROOT = getenv("SDKROOT");
@@ -151,17 +262,110 @@ int sil_llvm_gen_main(ArrayRef<const char *> argv, void *MainAddr) {
     Invocation.setTargetTriple(options.Target);
   if (!options.ResourceDir.empty())
     Invocation.setRuntimeResourcePath(options.ResourceDir);
+
+  Invocation.getFrontendOptions().StrictImplicitModuleContext =
+      options.StrictImplicitModuleContext;
+
+  Invocation.getFrontendOptions().DisableImplicitModules =
+      options.DisableImplicitModules;
+  Invocation.getSearchPathOptions().ExplicitSwiftModuleMapPath =
+      options.ExplicitSwiftModuleMapPath;
+
   // Set the module cache path. If not passed in we use the default swift module
   // cache.
   Invocation.getClangImporterOptions().ModuleCachePath = options.ModuleCachePath;
   Invocation.setParseStdlib();
 
   // Setup the language options
-  auto &LangOpts = Invocation.getLangOptions();
-  LangOpts.DisableAvailabilityChecking = true;
-  LangOpts.EnableAccessControl = false;
-  LangOpts.EnableObjCAttrRequiresFoundation = false;
-  LangOpts.EnableObjCInterop = LangOpts.Target.isOSDarwin();
+  if (options.SwiftVersionString.size()) {
+    auto vers = VersionParser::parseVersionString(options.SwiftVersionString,
+                                                  SourceLoc(), nullptr);
+    bool isValid = false;
+    if (vers.has_value()) {
+      if (auto effectiveVers = vers.value().getEffectiveLanguageVersion()) {
+        Invocation.getLangOptions().EffectiveLanguageVersion =
+            effectiveVers.value();
+        isValid = true;
+      }
+    }
+    if (!isValid) {
+      llvm::errs() << "error: invalid swift version "
+                   << options.SwiftVersionString << '\n';
+      exit(-1);
+    }
+  }
+  Invocation.getLangOptions().DisableAvailabilityChecking = true;
+  Invocation.getLangOptions().EnableAccessControl = false;
+  Invocation.getLangOptions().EnableObjCAttrRequiresFoundation = false;
+  Invocation.getLangOptions().EnableDeserializationSafety = false;
+  Invocation.getLangOptions().EnableExperimentalConcurrency =
+      options.EnableExperimentalConcurrency;
+  std::optional<bool> enableExperimentalMoveOnly =
+      toOptionalBool(options.EnableExperimentalMoveOnly);
+  if (enableExperimentalMoveOnly && *enableExperimentalMoveOnly) {
+    // FIXME: drop addition of Feature::MoveOnly once its queries are gone.
+    Invocation.getLangOptions().enableFeature(Feature::MoveOnly);
+    Invocation.getLangOptions().enableFeature(Feature::NoImplicitCopy);
+    Invocation.getLangOptions().enableFeature(
+        Feature::OldOwnershipOperatorSpellings);
+  }
+
+  for (auto &featureName : options.UpcomingFeatures) {
+    auto feature = Feature::getUpcomingFeature(featureName);
+    if (!feature) {
+      llvm::errs() << "error: unknown upcoming feature "
+                   << QuotedString(featureName) << "\n";
+      exit(-1);
+    }
+
+    if (auto firstVersion = feature->getLanguageVersion()) {
+      if (Invocation.getLangOptions().isSwiftVersionAtLeast(*firstVersion)) {
+        llvm::errs() << "error: upcoming feature " << QuotedString(featureName)
+                     << " is already enabled as of Swift version "
+                     << *firstVersion << '\n';
+        exit(-1);
+      }
+    }
+    Invocation.getLangOptions().enableFeature(*feature);
+  }
+
+  for (auto &featureName : options.ExperimentalFeatures) {
+    if (auto feature = Feature::getExperimentalFeature(featureName)) {
+      Invocation.getLangOptions().enableFeature(*feature);
+    } else {
+      llvm::errs() << "error: unknown experimental feature "
+                   << QuotedString(featureName) << "\n";
+      exit(-1);
+    }
+  }
+
+  // Enable strict concurrency if we have the feature specified or if it was
+  // specified via a command line option to sil-opt.
+  if (Invocation.getLangOptions().hasFeature(Feature::StrictConcurrency)) {
+    Invocation.getLangOptions().StrictConcurrencyLevel =
+        StrictConcurrency::Complete;
+  } else if (auto level = convertSILOptToRawStrictConcurrencyLevel(
+                 options.StrictConcurrencyLevel)) {
+    // If strict concurrency was enabled from the cmdline so the feature flag as
+    // well.
+    if (*level == StrictConcurrency::Complete)
+      Invocation.getLangOptions().enableFeature(Feature::StrictConcurrency);
+    Invocation.getLangOptions().StrictConcurrencyLevel = *level;
+  }
+
+  // If we have strict concurrency set as a feature and were told to turn off
+  // region-based isolation... do so now.
+  if (Invocation.getLangOptions().hasFeature(Feature::StrictConcurrency)) {
+    Invocation.getLangOptions().enableFeature(Feature::RegionBasedIsolation);
+  }
+
+  Invocation.getLangOptions().EnableObjCInterop =
+      options.EnableObjCInterop    ? true
+      : options.DisableObjCInterop ? false
+                                   : llvm::Triple(options.Target).isOSDarwin();
+
+  Invocation.getLangOptions().EnableCXXInterop = options.EnableCxxInterop;
+  Invocation.computeCXXStdlibOptions();
 
   // Setup the IRGen Options.
   IRGenOptions &Opts = Invocation.getIRGenOptions();
@@ -216,16 +420,26 @@ int sil_llvm_gen_main(ArrayRef<const char *> argv, void *MainAddr) {
       return IRGenDescriptor::forWholeModule(
           mod, Opts, TBDOpts, SILOpts, SILTypes,
           /*SILMod*/ nullptr, moduleName, PSPs);
-    } else {
-      return IRGenDescriptor::forFile(
-          mod->getFiles()[0], Opts, TBDOpts, SILOpts, SILTypes,
-          /*SILMod*/ nullptr, moduleName, PSPs, /*discriminator*/ "");
     }
+
+    return IRGenDescriptor::forFile(
+        mod->getFiles()[0], Opts, TBDOpts, SILOpts, SILTypes,
+        /*SILMod*/ nullptr, moduleName, PSPs, /*discriminator*/ "");
   };
 
   auto &eval = CI.getASTContext().evaluator;
   auto desc = getDescriptor();
   desc.out = &outFile->getOS();
+
+  if (options.OutputKind == IRGenOutputKind::LLVMAssemblyBeforeOptimization) {
+    auto generatedMod = evaluateOrFatal(eval, IRGenRequest{desc});
+    if (!generatedMod)
+      return 1;
+
+    generatedMod.getModule()->print(*outFile, nullptr);
+    return 0;
+  }
+
   auto generatedMod = evaluateOrFatal(eval, OptimizedIRRequest{desc});
   if (!generatedMod)
     return 1;
diff --git a/test/sil-llvm-gen/alloc.sil b/test/sil-llvm-gen/alloc.sil
index b39802a90cfea..385ee8ee9780c 100644
--- a/test/sil-llvm-gen/alloc.sil
+++ b/test/sil-llvm-gen/alloc.sil
@@ -1,12 +1,12 @@
-// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as -target x86_64-apple-macosx10.9 -module-name main %s -o - | %FileCheck %s
-// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as -target i386-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
-// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as -target x86_64-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
-// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as -target armv7-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
-// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as -target arm64-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
-// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as -target x86_64-unknown-linux-gnu %s -module-name main -o - | %FileCheck %s
+// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as-opt -target x86_64-apple-macosx10.9 -module-name main %s -o - | %FileCheck %s
+// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as-opt -target i386-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
+// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as-opt -target x86_64-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
+// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as-opt -target armv7-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
+// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as-opt -target arm64-apple-ios7.0 %s -module-name main -o - | %FileCheck %s
+// RUN: %sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as-opt -target x86_64-unknown-linux-gnu %s -module-name main -o - | %FileCheck %s
 
 // Use this testfile to check if the `swift-frontend -sil-llvm-gen` option works.
-// RUN: %swift_frontend_plain -sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as -target x86_64-apple-macosx10.9 -module-name main %s -o - | %FileCheck %s
+// RUN: %swift_frontend_plain -sil-llvm-gen -disable-legacy-type-info -output-kind=llvm-as-opt -target x86_64-apple-macosx10.9 -module-name main %s -o - | %FileCheck %s
 
 // REQUIRES: CODEGENERATOR=X86
 // REQUIRES: CODEGENERATOR=ARM