https://github.com/benlangmuir created 
https://github.com/llvm/llvm-project/pull/124003

With the changes in 48d0eb518, the CodeGenOptions used to emit .pcm files with 
-fmodule-format=obj (-gmodules) were the ones from the original invocation, 
rather than the ones specifically crafted for outputting the pcm. This was 
causing the pcm to be written with only the debug info and without the 
__clangast section in some cases (e.g. -O2). This unforunately was not covered 
by existing tests, because compiling and loading a module within a single 
compilation load the ast content from the in-memory module cache rather than 
reading it from the pcm file that was written.  This broke bootstrapping a 
build of clang with modules enabled on Darwin.

rdar://143418834

>From 40879d967ff8b7463f3eb56d437cacde6e2689ef Mon Sep 17 00:00:00 2001
From: Ben Langmuir <blangm...@apple.com>
Date: Wed, 22 Jan 2025 12:52:53 -0800
Subject: [PATCH] [clang][modules] Partially revert 48d0eb518 to fix -gmodules
 output

With the changes in 48d0eb518, the CodeGenOptions used to emit .pcm
files with -fmodule-format=obj (-gmodules) were the ones from the
original invocation, rather than the ones specifically crafted for
outputting the pcm. This was causing the pcm to be written with only the
debug info and without the __clangast section in some cases (e.g. -O2).
This unforunately was not covered by existing tests, because compiling
and loading a module within a single compilation load the ast content
from the in-memory module cache rather than reading it from the pcm file
that was written.  This broke bootstrapping a build of clang with
modules enabled on Darwin.

rdar://143418834
---
 clang/include/clang/CodeGen/BackendUtil.h      |  4 ++--
 clang/lib/CodeGen/BackendUtil.cpp              | 13 +++++++------
 clang/lib/CodeGen/CodeGenAction.cpp            |  8 +++++---
 .../CodeGen/ObjectFilePCHContainerWriter.cpp   |  8 ++++----
 clang/test/Modules/gmodules-codegenopts.c      | 18 ++++++++++++++++++
 5 files changed, 36 insertions(+), 15 deletions(-)
 create mode 100644 clang/test/Modules/gmodules-codegenopts.c

diff --git a/clang/include/clang/CodeGen/BackendUtil.h 
b/clang/include/clang/CodeGen/BackendUtil.h
index 78d1e5ee8e6d59..92e0d13bf25b69 100644
--- a/clang/include/clang/CodeGen/BackendUtil.h
+++ b/clang/include/clang/CodeGen/BackendUtil.h
@@ -39,8 +39,8 @@ enum BackendAction {
   Backend_EmitObj       ///< Emit native object files
 };
 
-void emitBackendOutput(CompilerInstance &CI, StringRef TDesc, llvm::Module *M,
-                       BackendAction Action,
+void emitBackendOutput(CompilerInstance &CI, CodeGenOptions &CGOpts,
+                       StringRef TDesc, llvm::Module *M, BackendAction Action,
                        llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
                        std::unique_ptr<raw_pwrite_stream> OS,
                        BackendConsumer *BC = nullptr);
diff --git a/clang/lib/CodeGen/BackendUtil.cpp 
b/clang/lib/CodeGen/BackendUtil.cpp
index 3951ad01497cca..4bbcd22d4fc030 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -206,9 +206,10 @@ class EmitAssemblyHelper {
   }
 
 public:
-  EmitAssemblyHelper(CompilerInstance &CI, llvm::Module *M,
+  EmitAssemblyHelper(CompilerInstance &CI, CodeGenOptions &CGOpts,
+                     llvm::Module *M,
                      IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS)
-      : CI(CI), Diags(CI.getDiagnostics()), CodeGenOpts(CI.getCodeGenOpts()),
+      : CI(CI), Diags(CI.getDiagnostics()), CodeGenOpts(CGOpts),
         TargetOpts(CI.getTargetOpts()), LangOpts(CI.getLangOpts()),
         TheModule(M), VFS(std::move(VFS)),
         TargetTriple(TheModule->getTargetTriple()) {}
@@ -1363,14 +1364,14 @@ runThinLTOBackend(CompilerInstance &CI, 
ModuleSummaryIndex *CombinedIndex,
   }
 }
 
-void clang::emitBackendOutput(CompilerInstance &CI, StringRef TDesc,
-                              llvm::Module *M, BackendAction Action,
+void clang::emitBackendOutput(CompilerInstance &CI, CodeGenOptions &CGOpts,
+                              StringRef TDesc, llvm::Module *M,
+                              BackendAction Action,
                               IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
                               std::unique_ptr<raw_pwrite_stream> OS,
                               BackendConsumer *BC) {
   llvm::TimeTraceScope TimeScope("Backend");
   DiagnosticsEngine &Diags = CI.getDiagnostics();
-  const auto &CGOpts = CI.getCodeGenOpts();
 
   std::unique_ptr<llvm::Module> EmptyModule;
   if (!CGOpts.ThinLTOIndexFile.empty()) {
@@ -1410,7 +1411,7 @@ void clang::emitBackendOutput(CompilerInstance &CI, 
StringRef TDesc,
     }
   }
 
-  EmitAssemblyHelper AsmHelper(CI, M, VFS);
+  EmitAssemblyHelper AsmHelper(CI, CGOpts, M, VFS);
   AsmHelper.emitAssembly(Action, std::move(OS), BC);
 
   // Verify clang's TargetInfo DataLayout against the LLVM TargetMachine's
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp 
b/clang/lib/CodeGen/CodeGenAction.cpp
index 15311fb2078101..7aa3639cabf392 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -312,7 +312,8 @@ void BackendConsumer::HandleTranslationUnit(ASTContext &C) {
 
   EmbedBitcode(getModule(), CodeGenOpts, llvm::MemoryBufferRef());
 
-  emitBackendOutput(CI, C.getTargetInfo().getDataLayoutString(), getModule(),
+  emitBackendOutput(CI, CI.getCodeGenOpts(),
+                    C.getTargetInfo().getDataLayoutString(), getModule(),
                     Action, FS, std::move(AsmOutStream), this);
 
   Ctx.setDiagnosticHandler(std::move(OldDiagnosticHandler));
@@ -1173,8 +1174,9 @@ void CodeGenAction::ExecuteAction() {
   std::unique_ptr<llvm::ToolOutputFile> OptRecordFile =
       std::move(*OptRecordFileOrErr);
 
-  emitBackendOutput(CI, CI.getTarget().getDataLayoutString(), TheModule.get(),
-                    BA, CI.getFileManager().getVirtualFileSystemPtr(),
+  emitBackendOutput(CI, CI.getCodeGenOpts(),
+                    CI.getTarget().getDataLayoutString(), TheModule.get(), BA,
+                    CI.getFileManager().getVirtualFileSystemPtr(),
                     std::move(OS));
   if (OptRecordFile)
     OptRecordFile->keep();
diff --git a/clang/lib/CodeGen/ObjectFilePCHContainerWriter.cpp 
b/clang/lib/CodeGen/ObjectFilePCHContainerWriter.cpp
index 02635ce235a12b..788c8b932ab524 100644
--- a/clang/lib/CodeGen/ObjectFilePCHContainerWriter.cpp
+++ b/clang/lib/CodeGen/ObjectFilePCHContainerWriter.cpp
@@ -322,16 +322,16 @@ class PCHContainerGenerator : public ASTConsumer {
       // Print the IR for the PCH container to the debug output.
       llvm::SmallString<0> Buffer;
       clang::emitBackendOutput(
-          CI, Ctx.getTargetInfo().getDataLayoutString(), M.get(),
+          CI, CodeGenOpts, Ctx.getTargetInfo().getDataLayoutString(), M.get(),
           BackendAction::Backend_EmitLL, FS,
           std::make_unique<llvm::raw_svector_ostream>(Buffer));
       llvm::dbgs() << Buffer;
     });
 
     // Use the LLVM backend to emit the pch container.
-    clang::emitBackendOutput(CI, Ctx.getTargetInfo().getDataLayoutString(),
-                             M.get(), BackendAction::Backend_EmitObj, FS,
-                             std::move(OS));
+    clang::emitBackendOutput(CI, CodeGenOpts,
+                             Ctx.getTargetInfo().getDataLayoutString(), 
M.get(),
+                             BackendAction::Backend_EmitObj, FS, 
std::move(OS));
 
     // Free the memory for the temporary buffer.
     llvm::SmallVector<char, 0> Empty;
diff --git a/clang/test/Modules/gmodules-codegenopts.c 
b/clang/test/Modules/gmodules-codegenopts.c
new file mode 100644
index 00000000000000..417bbb9cecefc1
--- /dev/null
+++ b/clang/test/Modules/gmodules-codegenopts.c
@@ -0,0 +1,18 @@
+// UNSUPPORTED: target={{.*}}-zos{{.*}}, target={{.*}}-aix{{.*}}
+// Check that the output from -gmodules can be loaded back by the compiler in
+// the presence of certain options like optimization level that could break
+// output. Note: without compiling twice the module is loaded from the 
in-memory
+// module cache not load it from the object container.
+
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x objective-c -fmodules -fmodule-format=obj \
+// RUN:   -fimplicit-module-maps -fmodules-cache-path=%t %s \
+// RUN:   -I %S/Inputs -verify -O2
+
+// Compile again, confirming we can load the module.
+// RUN: %clang_cc1 -x objective-c -fmodules -fmodule-format=obj \
+// RUN:   -fimplicit-module-maps -fmodules-cache-path=%t %s \
+// RUN:   -I %S/Inputs -verify -O2
+
+@import DebugObjC;
+// expected-no-diagnostics
\ No newline at end of file

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