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[X86_64] fix empty structure vaarg in c++ #77907

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Merged
merged 1 commit into from
Mar 21, 2024
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[X86_64] fix empty structure vaarg in c++ #77907

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4 changes: 4 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 @@ -3014,6 +3014,10 @@ Address X86_64ABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
ABIArgInfo AI = classifyArgumentType(Ty, 0, neededInt, neededSSE,
/*isNamedArg*/false);

// Empty records are ignored for parameter passing purposes.
if (AI.isIgnore())
return CGF.CreateMemTemp(Ty);

// AMD64-ABI 3.5.7p5: Step 1. Determine whether type may be passed
// in the registers. If not go to step 7.
if (!neededInt && !neededSSE)
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23 changes: 23 additions & 0 deletions clang/test/CodeGenCXX/x86_64-vaarg.cpp
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@@ -0,0 +1,23 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -o - %s | FileCheck %s
// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -x c -o - %s | FileCheck %s

typedef struct { struct {} a; } empty;

// CHECK-LABEL: @{{.*}}empty_record_test
// CHECK-NEXT: entry:
// CHECK-NEXT: [[RETVAL:%.*]] = alloca [[STRUCT_EMPTY:%.*]], align 1
// CHECK-NEXT: [[Z_ADDR:%.*]] = alloca i32, align 4
// CHECK-NEXT: [[LIST:%.*]] = alloca [1 x %struct.__va_list_tag], align 16
// CHECK-NEXT: [[TMP:%.*]] = alloca [[STRUCT_EMPTY]], align 1
// CHECK-NEXT: store i32 [[Z:%.*]], ptr [[Z_ADDR]], align 4
// CHECK-NEXT: [[ARRAYDECAY:%.*]] = getelementptr inbounds [1 x %struct.__va_list_tag], ptr [[LIST]], i64 0, i64 0
// CHECK-NEXT: call void @llvm.va_start(ptr [[ARRAYDECAY]])
// CHECK-NEXT: [[ARRAYDECAY1:%.*]] = getelementptr inbounds [1 x %struct.__va_list_tag], ptr [[LIST]], i64 0, i64 0
// CHECK-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 1 [[RETVAL]], ptr align 1 [[TMP]], i64 {{.*}}, i1 false)
// 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);
}