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Differential D66168

[WebAssembly] Make clang emit correct va_arg code for structs
ClosedPublic

Authored by quantum on Aug 13 2019, 2:06 PM.

Details

Reviewers
tlively
sbc100
kripken
aheejin
dschuff
Commits
rG8a503e439d0d: [WebAssembly] Make clang emit correct va_arg code for structs
rL368750: [WebAssembly] Make clang emit correct va_arg code for structs
rC368750: [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.

Diff Detail

Event Timeline

quantum created this revision.Aug 13 2019, 2:06 PM
Herald added a project: Restricted Project. · View Herald TranscriptAug 13 2019, 2:06 PM
Herald added subscribers: cfe-commits, sunfish, jgravelle-google, dschuff. · View Herald Transcript
Harbormaster completed remote builds in B36694: Diff 214916.Aug 13 2019, 2:07 PM
dschuff accepted this revision.Aug 13 2019, 2:14 PM

LGTM. Nice that we had a test which tested the wrong thing.

This revision is now accepted and ready to land.Aug 13 2019, 2:14 PM
Closed by commit rL368750: [WebAssembly] Make clang emit correct va_arg code for structs (authored by quantum). · Explain WhyAug 13 2019, 2:41 PM
This revision was automatically updated to reflect the committed changes.
Herald added a project: Restricted Project. · View Herald TranscriptAug 13 2019, 2:41 PM
Herald added a subscriber: llvm-commits. · View Herald Transcript
quantum mentioned this in D66255: [WebAssembly] Correctly handle va_arg of zero-sized structures.Aug 14 2019, 2:04 PM
quantum mentioned this in rL369042: [WebAssembly] Correctly handle va_arg of zero-sized structures.Aug 15 2019, 12:33 PM
quantum mentioned this in rG82bfd1d25712: [WebAssembly] Correctly handle va_arg of zero-sized structures.

Revision Contents

PathSize
clang/
lib/
CodeGen/
6 lines
test/
CodeGen/
11 lines

Diff 214916

clang/lib/CodeGen/TargetInfo.cpp

  • This file is larger than 256 KB, so syntax highlighting is disabled by default.
Show First 20 Lines • Show All 827 Lines • ▼ Show 20 LinesABIArgInfo WebAssemblyABIInfo::classifyReturnType(QualType RetTy) const {
} }
// Otherwise just do the default thing. // Otherwise just do the default thing.
return defaultInfo.classifyReturnType(RetTy); return defaultInfo.classifyReturnType(RetTy);
} }
Address WebAssemblyABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr, Address WebAssemblyABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
QualType Ty) const { 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), getContext().getTypeInfoInChars(Ty),
CharUnits::fromQuantity(4), CharUnits::fromQuantity(4),
/*AllowHigherAlign=*/ true); /*AllowHigherAlign=*/true);
} }
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
// le32/PNaCl bitcode ABI Implementation // le32/PNaCl bitcode ABI Implementation
// //
// This is a simplified version of the x86_32 ABI. Arguments and return values // This is a simplified version of the x86_32 ABI. Arguments and return values
// are always passed on the stack. // are always passed on the stack.
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
▲ Show 20 Lines • Show All 9,082 Lines • Show Last 20 Lines

clang/test/CodeGen/wasm-varargs.c

Show First 20 Lines • Show All 81 Lines • ▼ Show 20 Lines
// CHECK: define void @test_struct([[STRUCT_S:%[^,=]+]]*{{.*}} noalias sret [[AGG_RESULT:%.*]], i8*{{.*}} %fmt, ...) {{.*}} { // CHECK: define void @test_struct([[STRUCT_S:%[^,=]+]]*{{.*}} noalias sret [[AGG_RESULT:%.*]], i8*{{.*}} %fmt, ...) {{.*}} {
// CHECK: [[FMT_ADDR:%[^,=]+]] = alloca i8*, align 4 // CHECK: [[FMT_ADDR:%[^,=]+]] = alloca i8*, align 4
// CHECK: [[VA:%[^,=]+]] = alloca i8*, align 4 // CHECK: [[VA:%[^,=]+]] = alloca i8*, align 4
// CHECK: store i8* %fmt, i8** [[FMT_ADDR]], align 4 // CHECK: store i8* %fmt, i8** [[FMT_ADDR]], align 4
// CHECK: [[VA1:%[^,=]+]] = bitcast i8** [[VA]] to i8* // CHECK: [[VA1:%[^,=]+]] = bitcast i8** [[VA]] to i8*
// CHECK: call void @llvm.va_start(i8* [[VA1]]) // CHECK: call void @llvm.va_start(i8* [[VA1]])
// CHECK: [[ARGP_CUR:%[^,=]+]] = load i8*, i8** [[VA]], align 4 // 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: store i8* [[ARGP_NEXT]], i8** [[VA]], align 4
// CHECK: [[R3:%[^,=]+]] = bitcast i8* [[ARGP_CUR]] to [[STRUCT_S]]* // CHECK: [[R3:%[^,=]+]] = bitcast i8* [[ARGP_CUR]] to [[STRUCT_S]]**
// CHECK: [[R4:%[^,=]+]] = bitcast [[STRUCT_S]]* [[AGG_RESULT]] to i8* // CHECK: [[R4:%[^,=]+]] = load [[STRUCT_S]]*, [[STRUCT_S]]** %0, align 4
// CHECK: [[R5:%[^,=]+]] = bitcast [[STRUCT_S]]* [[R3]] to i8* // CHECK: [[R5:%[^,=]+]] = bitcast [[STRUCT_S]]* [[AGG_RESULT]] to i8*
// CHECK: call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 [[R4]], i8* align 4 [[R5]], i32 12, i1 false) // 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: [[VA2:%[^,=]+]] = bitcast i8** [[VA]] to i8*
// CHECK: call void @llvm.va_end(i8* [[VA2]]) // CHECK: call void @llvm.va_end(i8* [[VA2]])
// CHECK: ret void // CHECK: ret void
// CHECK: } // CHECK: }