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[X86] Passing union type through register 

For example:

  union M256 {
    double d;
    __m256 m;
  };
  extern void foo1(union M256 A);
  union M256 m1;
  void test() {
    foo1(m1);
  }

clang will pass m1 through stack which does not follow the ABI.

Differential Revision: https://reviews.llvm.org/D78699
This commit is contained in:
Liu, Chen3 2020-10-09 11:20:29 +08:00
parent c1489ee5a7
commit 26cfb6e562
2 changed files with 39 additions and 6 deletions
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14
clang/lib/CodeGen/TargetInfo.cpp
View File

@ -3061,6 +3061,7 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
// Classify the fields one at a time, merging the results. // Classify the fields one at a time, merging the results.
unsigned idx = 0; unsigned idx = 0;
bool IsUnion = RT->isUnionType();
for (RecordDecl::field_iterator i = RD->field_begin(), e = RD->field_end(); for (RecordDecl::field_iterator i = RD->field_begin(), e = RD->field_end();
i != e; ++i, ++idx) { i != e; ++i, ++idx) {
uint64_t Offset = OffsetBase + Layout.getFieldOffset(idx); uint64_t Offset = OffsetBase + Layout.getFieldOffset(idx);
@ -3071,13 +3072,16 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
continue; continue;
// AMD64-ABI 3.2.3p2: Rule 1. If the size of an object is larger than // AMD64-ABI 3.2.3p2: Rule 1. If the size of an object is larger than
// four eightbytes, or it contains unaligned fields, it has class MEMORY. // eight eightbytes, or it contains unaligned fields, it has class MEMORY.
// //
// The only case a 256-bit wide vector could be used is when the struct // The only case a 256-bit or a 512-bit wide vector could be used is when
// contains a single 256-bit element. Since Lo and Hi logic isn't extended // the struct contains a single 256-bit or 512-bit element. Early check
// to work for sizes wider than 128, early check and fallback to memory. // and fallback to memory.
// //
if (Size > 128 && (Size != getContext().getTypeSize(i->getType()) || // FIXME: Extended the Lo and Hi logic properly to work for size wider
// than 128.
if (Size > 128 &&
((!IsUnion && Size != getContext().getTypeSize(i->getType())) ||
Size > getNativeVectorSizeForAVXABI(AVXLevel))) { Size > getNativeVectorSizeForAVXABI(AVXLevel))) {
Lo = Memory; Lo = Memory;
postMerge(Size, Lo, Hi); postMerge(Size, Lo, Hi);

29
clang/test/CodeGen/X86/avx-union.c Normal file
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@ -0,0 +1,29 @@
// RUN: %clang_cc1 -w -ffreestanding -triple x86_64-linux-gnu -target-feature +avx -emit-llvm -o %t %s || FileCheck < %t %s --check-prefix=CHECK, AVX
// RUN: %clang_cc1 -w -ffreestanding -triple x86_64-linux-gnu -target-feature +avx512f -emit-llvm -o %t %s || FileCheck < %t %s --check-prefix=CHECK, AVX512
// 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)));
typedef int __m512 __attribute__ ((__vector_size__ (64)));
union M256 {
double d;
__m256 m;
};
union M512 {
double d;
__m512 m;
};
extern void foo1(union M256 A);
extern void foo2(union M512 A);
union M256 m1;
union M512 m2;
// CHECK-LABEL: define dso_local void @test()
// CHECK: void @foo1(<4 x double>
// AVX: call void @foo2(%union.M512* byval(%union.M512) align 64
// AVX512: call void @foo2(<8 x double>
void test() {
foo1(m1);
foo2(m2);
}