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[WebAssembly] Make clang emit correct va_arg code for structs 

Summary:
In the WebAssembly backend, when lowering variadic function calls, non-single
member aggregate type arguments are always passed by pointer.

However, when emitting va_arg code in clang, the arguments are instead read as
if they are passed directly. This results in the pointer being read as the
actual structure.

Fixes https://github.com/emscripten-core/emscripten/issues/9042.

Reviewers: tlively, sbc100, kripken, aheejin, dschuff

Reviewed By: dschuff

Subscribers: dschuff, jgravelle-google, sunfish, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66168

llvm-svn: 368750
This commit is contained in:
Guanzhong Chen 2019-08-13 21:41:11 +00:00
parent 10f0668b57
commit 8a503e439d
2 changed files with 10 additions and 7 deletions
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6
clang/lib/CodeGen/TargetInfo.cpp
View File

@ -833,10 +833,12 @@ ABIArgInfo WebAssemblyABIInfo::classifyReturnType(QualType RetTy) const {
Address WebAssemblyABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
QualType Ty) const {
return emitVoidPtrVAArg(CGF, VAListAddr, Ty, /*IsIndirect=*/ false,
bool IsIndirect =
isAggregateTypeForABI(Ty) && !isSingleElementStruct(Ty, getContext());
return emitVoidPtrVAArg(CGF, VAListAddr, Ty, IsIndirect,
getContext().getTypeInfoInChars(Ty),
CharUnits::fromQuantity(4),
/*AllowHigherAlign=*/ true);
/*AllowHigherAlign=*/true);
}
//===----------------------------------------------------------------------===//

11
clang/test/CodeGen/wasm-varargs.c
View File

@ -87,12 +87,13 @@ struct S test_struct(char *fmt, ...) {
// CHECK: [[VA1:%[^,=]+]] = bitcast i8** [[VA]] to i8*
// CHECK: call void @llvm.va_start(i8* [[VA1]])
// CHECK: [[ARGP_CUR:%[^,=]+]] = load i8*, i8** [[VA]], align 4
// CHECK: [[ARGP_NEXT:%[^,=]+]] = getelementptr inbounds i8, i8* [[ARGP_CUR]], i32 12
// CHECK: [[ARGP_NEXT:%[^,=]+]] = getelementptr inbounds i8, i8* [[ARGP_CUR]], i32 4
// CHECK: store i8* [[ARGP_NEXT]], i8** [[VA]], align 4
// CHECK: [[R3:%[^,=]+]] = bitcast i8* [[ARGP_CUR]] to [[STRUCT_S]]*
// CHECK: [[R4:%[^,=]+]] = bitcast [[STRUCT_S]]* [[AGG_RESULT]] to i8*
// CHECK: [[R5:%[^,=]+]] = bitcast [[STRUCT_S]]* [[R3]] to i8*
// CHECK: call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 [[R4]], i8* align 4 [[R5]], i32 12, i1 false)
// CHECK: [[R3:%[^,=]+]] = bitcast i8* [[ARGP_CUR]] to [[STRUCT_S]]**
// CHECK: [[R4:%[^,=]+]] = load [[STRUCT_S]]*, [[STRUCT_S]]** %0, align 4
// CHECK: [[R5:%[^,=]+]] = bitcast [[STRUCT_S]]* [[AGG_RESULT]] to i8*
// CHECK: [[R6:%[^,=]+]] = bitcast [[STRUCT_S]]* [[R4]] to i8*
// CHECK: call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 [[R5]], i8* align 4 [[R6]], i32 12, i1 false)
// CHECK: [[VA2:%[^,=]+]] = bitcast i8** [[VA]] to i8*
// CHECK: call void @llvm.va_end(i8* [[VA2]])
// CHECK: ret void