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[X86_32] Teach X86_32 va_arg to ignore empty structs. #86075

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Merged
merged 1 commit into from
Apr 3, 2024
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[X86_32] Teach X86_32 va_arg to ignore empty structs. #86075

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6 changes: 6 additions & 0 deletions clang/lib/CodeGen/Targets/X86.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1069,6 +1069,12 @@ Address X86_32ABIInfo::EmitVAArg(CodeGenFunction &CGF,

auto TypeInfo = getContext().getTypeInfoInChars(Ty);

CCState State(*const_cast<CGFunctionInfo *>(CGF.CurFnInfo));
ABIArgInfo AI = classifyArgumentType(Ty, State, /*ArgIndex*/ 0);
// Empty records are ignored for parameter passing purposes.
if (AI.isIgnore())
return CGF.CreateMemTemp(Ty);
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I'd prefer to use classifyArgumentType, like we do for the 64-bit case, instead of trying to duplicate the logic.

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classifyArgumentType in X86_32 need CCState parameter, but we can not get it in this scope, because the CCState is temporarily calculated in X86_32ABIInfo::computeInfo.

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If it doesn't work with the code as-is, please refactor to the code to make it work. Scattered checks like this are hard to maintain.

The simplest thing here would be to just construct a CCState here, I think? Or if that doesn't work for some reason, make the CCState parameter to classifyArgumentType optional.


// x86-32 changes the alignment of certain arguments on the stack.
//
// Just messing with TypeInfo like this works because we never pass
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21 changes: 21 additions & 0 deletions clang/test/CodeGenCXX/x86_32-vaarg.cpp
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@@ -0,0 +1,21 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
// RUN: %clang_cc1 -triple i386-linux-gnu -emit-llvm -o - %s | FileCheck %s

typedef struct {} empty;

// CHECK-LABEL: @_Z17empty_record_testiz(
// CHECK-NEXT: entry:
// CHECK-NEXT: [[RESULT_PTR:%.*]] = alloca ptr, align 4
// CHECK-NEXT: [[Z_ADDR:%.*]] = alloca i32, align 4
// CHECK-NEXT: [[LIST:%.*]] = alloca ptr, align 4
// CHECK-NEXT: [[TMP:%.*]] = alloca [[STRUCT_EMPTY:%.*]], align 1
// CHECK-NEXT: store ptr [[AGG_RESULT:%.*]], ptr [[RESULT_PTR]], align 4
// CHECK-NEXT: store i32 [[Z:%.*]], ptr [[Z_ADDR]], align 4
// CHECK-NEXT: call void @llvm.va_start.p0(ptr [[LIST]])
// CHECK-NEXT: ret void
//
empty empty_record_test(int z, ...) {
__builtin_va_list list;
__builtin_va_start(list, z);
return __builtin_va_arg(list, empty);
}