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Revert "Partial revert of r21901"

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This reverts r21927.

Reason: broke the build.

BUG=
TBR=jochen@chromium.org, bmeurer@chromium.org

Review URL: https://codereview.chromium.org/347423002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21928 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
marja@chromium.org 2014-06-23 10:31:12 +00:00
parent 2880181fb8
commit 5ef3f06029
2 changed files with 1 additions and 35 deletions
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6
src/base/atomicops_internals_x86_gcc.cc
View File

@ -42,7 +42,6 @@ namespace base {
// default values should hopefully be pretty safe.
struct AtomicOps_x86CPUFeatureStruct AtomicOps_Internalx86CPUFeatures = {
false, // bug can't exist before process spawns multiple threads
false, // no SSE2
};
} } // namespace v8::base
@ -88,11 +87,6 @@ void AtomicOps_Internalx86CPUFeaturesInit() {
} else {
AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug = false;
}
#if !defined(__SSE2__)
// edx bit 26 is SSE2 which we use to tell use whether we can use mfence
AtomicOps_Internalx86CPUFeatures.has_sse2 = ((edx >> 26) & 1);
#endif
}
class AtomicOpsx86Initializer {

30
src/base/atomicops_internals_x86_gcc.h
View File

@ -17,9 +17,6 @@ namespace base {
struct AtomicOps_x86CPUFeatureStruct {
bool has_amd_lock_mb_bug; // Processor has AMD memory-barrier bug; do lfence
// after acquire compare-and-swap.
#if !defined(__SSE2__)
bool has_sse2; // Processor has SSE2.
#endif
};
extern struct AtomicOps_x86CPUFeatureStruct AtomicOps_Internalx86CPUFeatures;
@ -94,10 +91,7 @@ inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
*ptr = value;
}
#if defined(__x86_64__) || defined(__SSE2__)
// 64-bit implementations of memory barrier can be simpler, because it
// "mfence" is guaranteed to exist.
// We require SSE2, so mfence is guaranteed to exist.
inline void MemoryBarrier() {
__asm__ __volatile__("mfence" : : : "memory");
}
@ -107,28 +101,6 @@ inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
MemoryBarrier();
}
#else
inline void MemoryBarrier() {
if (AtomicOps_Internalx86CPUFeatures.has_sse2) {
__asm__ __volatile__("mfence" : : : "memory");
} else { // mfence is faster but not present on PIII
Atomic32 x = 0;
NoBarrier_AtomicExchange(&x, 0); // acts as a barrier on PIII
}
}
inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
if (AtomicOps_Internalx86CPUFeatures.has_sse2) {
*ptr = value;
__asm__ __volatile__("mfence" : : : "memory");
} else {
NoBarrier_AtomicExchange(ptr, value);
// acts as a barrier on PIII
}
}
#endif
inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
ATOMICOPS_COMPILER_BARRIER();
*ptr = value; // An x86 store acts as a release barrier.