[CIR] Correctly handle annotate attribute on C++ constructors/destructors

[Sharp0802]

This PR fixes an issue where the [[clang::annotate]] attribute on C++ constructors (CXXConstructorDecl) was not correctly lowered, and resolves a subsequent crash in the cir-to-llvm pipeline caused by the initial fix.

1. The Problem

There were two distinct problems:

• Initial Bug: The [[clang::annotate]] attribute was completely ignored when applied to a C++ constructor. While it worked for regular functions, the specific code path for handling CXXConstructorDecl in CIRGenModule did not process this attribute.

• Downstream Crash: After fixing the initial bug to generate the correct annotations and cir.global_annotations in the CIR dialect, the cir-translate tool would crash with a "redefinition of symbol" error for the annotation string (e.g., .str.annotation).

2. Analysis and Root Cause

• Cause of Initial Bug: In CIRGenModule::emitGlobalDefinition, the code path for constructors and destructors branches to ABI->emitCXXStructor. This path was missing the logic to check for an AnnotateAttr and add it to the deferredAnnotations map, which is correctly handled for regular FunctionDecls.

• Cause of Downstream Crash: The cir-to-llvm lowering pipeline has two mechanisms for handling annotations:

  1. The LoweringPrepare pass processes the cir.global_annotations attribute on the ModuleOp and generates the corresponding @llvm.global.annotations array and its associated global string constants.
  2. A later stage in the cir-translate binary also attempts to process the same cir.global_annotations attribute.

  The issue was that LoweringPreparePass did not consume (remove) the cir.global_annotations attribute after processing it. This left the attribute on the module, causing the later stage in cir-translate to re-process it, leading to the symbol redefinition crash.

3. Implementation

This PR addresses both issues with two key changes:

1. In CIRGenModule.cpp:

   • The logic to handle AnnotateAttr has been added to the CXXConstructorDecl / CXXDestructorDecl path within emitGlobalDefinition. This ensures that constructor annotations are correctly identified and deferred for processing, just like regular functions.

2. In LoweringPreparePass:

   • After the buildGlobalAnnotationValues() function successfully processes the cir.global_annotations attribute and generates the necessary LLVM globals, the pass now removes the cir.global_annotations attribute from the ModuleOp. This "consumes" the attribute, preventing any subsequent pass from redundantly processing it.

4. Verification

With these changes, a C++ constructor with a [[clang::annotate]] attribute is now correctly lowered through the entire pipeline:

• The ClangIR (cir dialect) correctly contains both the local annotations on the cir.func and the module-level cir.global_annotations.
• The cir-opt -cir-to-llvm pass successfully lowers this to the LLVM dialect.
• The cir-translate tool successfully converts the LLVM dialect to LLVM IR text without crashing.
• The final LLVM IR contains the expected @llvm.global.annotations metadata for the constructor.

This fix ensures that annotation metadata is preserved correctly and robustly for C++ constructors.

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff HEAD~1 HEAD --extensions cpp,c,h -- clang/include/clang/CIR/Dialect/IR/CIRTraits.h clang/test/CIR/CodeGen/X86/avx-shuffle-builtins.c clang/test/CIR/CodeGen/X86/avx2-builtins.c clang/test/CIR/CodeGen/X86/palignr.c clang/test/CIR/CodeGen/X86/sse3-builtins.c clang/test/CIR/CodeGen/aapcs-volatile-bitfields.c clang/test/CIR/CodeGen/builtin-bcopy.cpp clang/test/CIR/CodeGen/builtin-types.c clang/test/CIR/CodeGen/builtin-x86-pshufd.cpp clang/test/CIR/CodeGen/builtin-x86-pslldqi.cpp clang/test/CIR/CodeGen/class_cast.cpp clang/test/CIR/CodeGen/hot-attr.cpp clang/test/CIR/CodeGen/mms-bitfields.c clang/test/CIR/CodeGen/static_class_ref.cpp clang/test/CIR/CodeGen/type-trait.cpp clang/test/CIR/CodeGen/virtual-destructor-explicit-unqualified-call.cpp clang/test/CIR/Transforms/setjmp-longjmp-lower.c clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h clang/include/clang/CIR/Dialect/IR/CIRDataLayout.h clang/include/clang/CIR/Dialect/IR/CIRDialect.h clang/include/clang/CIR/MissingFeatures.h clang/lib/CIR/CodeGen/CIRGenAtomic.cpp clang/lib/CIR/CodeGen/CIRGenBuilder.h clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp clang/lib/CIR/CodeGen/CIRGenBuiltinNVPTX.cpp clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp clang/lib/CIR/CodeGen/CIRGenExpr.cpp clang/lib/CIR/CodeGen/CIRGenExprAgg.cpp clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp clang/lib/CIR/CodeGen/CIRGenExprComplex.cpp clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp clang/lib/CIR/CodeGen/CIRGenFunction.cpp clang/lib/CIR/CodeGen/CIRGenFunction.h clang/lib/CIR/CodeGen/CIRGenModule.cpp clang/lib/CIR/CodeGen/CIRGenModule.h clang/lib/CIR/CodeGen/CIRRecordLayoutBuilder.cpp clang/lib/CIR/Dialect/IR/CIRDialect.cpp clang/lib/CIR/Dialect/Transforms/LifetimeCheck.cpp clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerTypes.cpp clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.h clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVMIR.cpp clang/test/CIR/CodeGen/AArch64/neon-misc.c clang/test/CIR/CodeGen/X86/avx-builtins.c clang/test/CIR/CodeGen/X86/avx512bw-builtins.c clang/test/CIR/CodeGen/X86/avx512dq-builtins.c clang/test/CIR/CodeGen/X86/avx512f-builtins.c clang/test/CIR/CodeGen/X86/avx512vl-builtins.c clang/test/CIR/CodeGen/X86/avx512vlbw-buiiltins.c clang/test/CIR/CodeGen/X86/avx512vldq-builtins.c clang/test/CIR/CodeGen/X86/sse-builtins.c clang/test/CIR/CodeGen/X86/sse2-builtins.c clang/test/CIR/CodeGen/X86/sse41-builtins.c clang/test/CIR/CodeGen/address-space-conversion.cpp clang/test/CIR/CodeGen/agg-copy.c clang/test/CIR/CodeGen/applearm64-array-cookies.cpp clang/test/CIR/CodeGen/array-init-destroy.cpp clang/test/CIR/CodeGen/array-init.c clang/test/CIR/CodeGen/array-init.cpp clang/test/CIR/CodeGen/array-new-init.cpp clang/test/CIR/CodeGen/array.cpp clang/test/CIR/CodeGen/assign-operator.cpp clang/test/CIR/CodeGen/builtin-setjmp-longjmp.c clang/test/CIR/CodeGen/builtins-memory.c clang/test/CIR/CodeGen/complex-cast.cpp clang/test/CIR/CodeGen/complex.cpp clang/test/CIR/CodeGen/dynamic-cast-relative-layout.cpp clang/test/CIR/CodeGen/dynamic-cast.cpp clang/test/CIR/CodeGen/globals.cpp clang/test/CIR/CodeGen/initlist-ptr-ptr.cpp clang/test/CIR/CodeGen/move.cpp clang/test/CIR/CodeGen/new.cpp clang/test/CIR/CodeGen/pointer-arith-ext.c clang/test/CIR/CodeGen/pointers.cpp clang/test/CIR/CodeGen/unary.cpp clang/test/CIR/CodeGen/var-arg-float.c clang/test/CIR/CodeGen/var-arg-scope.c clang/test/CIR/CodeGen/var-arg.c clang/test/CIR/CodeGen/vectype-ext.cpp clang/test/CIR/CodeGen/virtual-base-cast.cpp clang/test/CIR/CodeGen/vtt.cpp clang/test/CIR/Lowering/var-arg-x86_64.c clang/test/CIR/Transforms/mem2reg.c

View the diff from clang-format here.

diff --git a/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp b/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp
index 5c01706447..ca55565f93 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp
@@ -302,7 +302,7 @@ RValue CIRGenFunction::emitCXXMemberOrOperatorMemberCallExpr(
            "Destructor shouldn't have explicit parameters");
     assert(ReturnValue.isNull() && "Destructor shouldn't have return value");
     if (useVirtualCall) {
-      CIRGenFunction* CGF = CGM.getCurrCIRGenFun();
+      CIRGenFunction *CGF = CGM.getCurrCIRGenFun();
       CGM.getCXXABI().emitVirtualDestructorCall(
           *CGF, dtor, Dtor_Complete, This.getAddress(),
           dyn_cast<CXXMemberCallExpr>(CE));

[bcardosolopes]

Thanks for the detailed explanation, some comments but this mostly ready to go

[bcardosolopes]

Seems like some clang-format is needed

[bcardosolopes]

looks like clang-format is failing, you also need to add a testcase

[Sharp0802]

Testcases added:

• clang/test/CIR/CodeGen/attr-annotate-constructor.cpp
• clang/test/CIR/CodeGen/attr-annotate-destructor.cpp

clang-format passes for changed files.

[xlauko]

Is this also a problem in classical codegen, because at quick glance I don't see path there handling the AnnotateAttr for ctors/dtors. If it is somewhere deeper we should probably follow the classical codegen not adhoc patch like this.

@erichkeane might have better insight on how this works in clang?

[erichkeane]

Is this also a problem in classical codegen, because at quick glance I don't see path there handling the AnnotateAttr for ctors/dtors. If it is somewhere deeper we should probably follow the classical codegen not adhoc patch like this.

@erichkeane might have better insight on how this works in clang?

I don't really have any idea unfortunately, I haven't dug into the codegen parts of this. I wouldn't doubt that this needs help in Classic codegen either

[bcardosolopes]

Are you sure you need to add this here? It might just work as is. EmitGlobal both in OG and in the incubator handles it generically for FunctionDecl

[bcardosolopes]

@xlauko ^

[xlauko]

I got the same feeling, thats why I was asking the question above.

[bcardosolopes]

Yea, I'm just pointing out how this work (as an answer to your question) via a rhetoric question. @Sharp0802 please remove this bit, if that doesn't do the job, you need to debug and find out what you are missing elsewhere.