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Add option to use older clang ABI behavior when passing certain union types as function arguments 

Recently commit D78699 (commit 26cfb6e562), fixed clang's behavior with respect
to passing a union type through a register to correctly follow the ABI. However,
this is an ABI breaking change with earlier versions of the clang compiler, so we
should add an -fclang-abi-compat option to address this. Additionally, the PS4 ABI
requires the older behavior, so that is added as well.

This change adds a Ver11 value to the ClangABI enum that when it is set (or the
target is the PS4 triple), we skip the ABI fix introduced in D78699.

Differential Revision: https://reviews.llvm.org/D89747
This commit is contained in:
Douglas Yung 2020-10-19 18:17:34 -07:00
parent ae9d040028
commit 774ab60125
4 changed files with 24 additions and 5 deletions
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5
clang/include/clang/Basic/LangOptions.h
View File

@ -153,6 +153,11 @@ public:
/// NetBSD.
Ver9,
/// Attempt to be ABI-compatible with code generated by Clang 11.0.x
/// (git 2e10b7a39b93). This causes clang to pass unions with a 256-bit
/// vector member on the stack instead of using registers.
Ver11,
/// Conform to the underlying platform's C and C++ ABIs as closely
/// as we can.
Latest

6
clang/lib/CodeGen/TargetInfo.cpp
View File

@ -3061,7 +3061,11 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
// Classify the fields one at a time, merging the results.
unsigned idx = 0;
bool IsUnion = RT->isUnionType();
bool UseClang11Compat = getContext().getLangOpts().getClangABICompat() <=
LangOptions::ClangABI::Ver11 ||
getContext().getTargetInfo().getTriple().isPS4();
bool IsUnion = RT->isUnionType() && !UseClang11Compat;
for (RecordDecl::field_iterator i = RD->field_begin(), e = RD->field_end();
i != e; ++i, ++idx) {
uint64_t Offset = OffsetBase + Layout.getFieldOffset(idx);

2
clang/lib/Frontend/CompilerInvocation.cpp
View File

@ -3460,6 +3460,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
Opts.setClangABICompat(LangOptions::ClangABI::Ver7);
else if (Major <= 9)
Opts.setClangABICompat(LangOptions::ClangABI::Ver9);
else if (Major <= 11)
Opts.setClangABICompat(LangOptions::ClangABI::Ver11);
} else if (Ver != "latest") {
Diags.Report(diag::err_drv_invalid_value)
<< A->getAsString(Args) << A->getValue();

16
clang/test/CodeGen/X86/avx-union.c
View File

@ -1,5 +1,11 @@
// RUN: %clang_cc1 -w -ffreestanding -triple x86_64-linux-gnu -target-feature +avx -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=AVX
// RUN: %clang_cc1 -w -ffreestanding -triple x86_64-linux-gnu -target-feature +avx512f -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=AVX512
// Test Clang 11 and earlier behavior
// RUN: %clang_cc1 -w -ffreestanding -triple x86_64-linux-gnu -target-feature +avx -fclang-abi-compat=10.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=AVX --check-prefix=CHECK-LEGACY
// RUN: %clang_cc1 -w -ffreestanding -triple x86_64-linux-gnu -target-feature +avx512f -fclang-abi-compat=11.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK-LEGACY --check-prefix=AVX512-LEGACY
// RUN: %clang_cc1 -w -ffreestanding -triple x86_64-scei-ps4 -target-feature +avx -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK-LEGACY --check-prefix=AVX-LEGACY
// This tests verifies that a union parameter should pass by a vector regitster whose first eightbyte is SSE and the other eightbytes are SSEUP.
typedef int __m256 __attribute__ ((__vector_size__ (32)));
@ -19,10 +25,12 @@ extern void foo1(union M256 A);
extern void foo2(union M512 A);
union M256 m1;
union M512 m2;
// CHECK-LABEL: define void @test()
// CHECK: call void @foo1(<4 x double>
// AVX: call void @foo2(%union.M512* byval(%union.M512) align 64
// AVX512: call void @foo2(<8 x double>
// CHECK-LABEL: define void @test()
// CHECK: call void @foo1(<4 x double>
// CHECK-LEGACY: call void @foo1(%union.M256* byval(%union.M256) align 32
// AVX: call void @foo2(%union.M512* byval(%union.M512) align 64
// AVX512: call void @foo2(<8 x double>
// AVX512-LEGACY: call void @foo2(%union.M512* byval(%union.M512) align 64
void test() {
foo1(m1);
foo2(m2);