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[MS] Zero out ECX in __cpuid in intrin.h 

Summary:
Some CPUID leafs depend on the value of ECX as well as EAX, but we left
it uninitialized.

Originally reported as https://crbug.com/901547

Reviewers: craig.topper, hans

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D54171

llvm-svn: 346265
This commit is contained in:
Reid Kleckner 2018-11-06 20:45:26 +00:00
parent b23fded901
commit 902fa41188
2 changed files with 19 additions and 1 deletions
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2
clang/lib/Headers/intrin.h
View File

@ -535,7 +535,7 @@ __stosq(unsigned __int64 *__dst, unsigned __int64 __x, size_t __n) {
static __inline__ void __DEFAULT_FN_ATTRS
__cpuid(int __info[4], int __level) {
__asm__ ("cpuid" : "=a"(__info[0]), "=b" (__info[1]), "=c"(__info[2]), "=d"(__info[3])
: "a"(__level));
: "a"(__level), "c"(0));
}
static __inline__ void __DEFAULT_FN_ATTRS
__cpuidex(int __info[4], int __level, int __ecx) {

18
clang/test/CodeGen/ms-intrinsics-cpuid.c Normal file
View File

@ -0,0 +1,18 @@
// RUN: %clang_cc1 -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
// RUN: -triple i686-windows-msvc -emit-llvm %s -o - | FileCheck %s
// RUN: %clang_cc1 -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
// RUN: -triple x86_64-windows-msvc -emit-llvm %s -o - | FileCheck %s
// intrin.h needs size_t, but -ffreestanding prevents us from getting it from
// stddef.h. Work around it with this typedef.
typedef __SIZE_TYPE__ size_t;
#include <intrin.h>
void test__cpuid(int *info, int level) {
__cpuid(info, level);
}
// CHECK-LABEL: define {{.*}} @test__cpuid(i32* %{{.*}}, i32 %{{.*}})
// CHECK: call { i32, i32, i32, i32 } asm "cpuid",
// CHECK-SAME: "={ax},={bx},={cx},={dx},{ax},{cx},~{dirflag},~{fpsr},~{flags}"
// CHECK-SAME: (i32 %{{.*}}, i32 0)