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Merged
merged 1 commit into from
Nov 29, 2022
Merged

PR for llvm/llvm-project#58794 #218

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8 changes: 4 additions & 4 deletions clang/lib/CodeGen/TargetInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7047,10 +7047,10 @@ Address ARMABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,

// Empty records are ignored for parameter passing purposes.
if (isEmptyRecord(getContext(), Ty, true)) {
Address Addr = Address(CGF.Builder.CreateLoad(VAListAddr),
getVAListElementType(CGF), SlotSize);
Addr = CGF.Builder.CreateElementBitCast(Addr, CGF.ConvertTypeForMem(Ty));
return Addr;
VAListAddr = CGF.Builder.CreateElementBitCast(VAListAddr, CGF.Int8PtrTy);
auto *Load = CGF.Builder.CreateLoad(VAListAddr);
Address Addr = Address(Load, CGF.Int8Ty, SlotSize);
return CGF.Builder.CreateElementBitCast(Addr, CGF.ConvertTypeForMem(Ty));
}

CharUnits TySize = getContext().getTypeSizeInChars(Ty);
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23 changes: 23 additions & 0 deletions clang/test/CodeGen/arm-vaarg.c
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@@ -0,0 +1,23 @@
// RUN: %clang -Xclang -no-opaque-pointers -mfloat-abi=soft -target arm-linux-gnu -emit-llvm -S -o - %s | FileCheck %s

struct Empty {};

struct Empty emptyvar;

void take_args(int a, ...) {
// CHECK: [[ALLOCA_VA_LIST:%[a-zA-Z0-9._]+]] = alloca %struct.__va_list, align 4
// CHECK: call void @llvm.va_start
// CHECK-NEXT: [[AP_ADDR:%[a-zA-Z0-9._]+]] = bitcast %struct.__va_list* [[ALLOCA_VA_LIST]] to i8**
// CHECK-NEXT: [[LOAD_AP:%[a-zA-Z0-9._]+]] = load i8*, i8** [[AP_ADDR]], align 4
// CHECK-NEXT: [[EMPTY_PTR:%[a-zA-Z0-9._]+]] = bitcast i8* [[LOAD_AP]] to %struct.Empty*

// It's conceivable that EMPTY_PTR may not actually be a valid pointer
// (e.g. it's at the very bottom of the stack and the next page is
// invalid). This doesn't matter provided it's never loaded (there's no
// well-defined way to tell), but it becomes a problem if we do try to use it.
// CHECK-NOT: load %struct.Empty, %struct.Empty* [[EMPTY_PTR]]
__builtin_va_list l;
__builtin_va_start(l, a);
emptyvar = __builtin_va_arg(l, struct Empty);
__builtin_va_end(l);
}