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Dynamically choose SSE 4.2

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Summary: Otherwise, if we compile on machine with SSE4.2 support and run it on machine without the support, we will fail.

Test Plan: compiles, verified that isSse42() gets called.

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17505
This commit is contained in:
Igor Canadi 2014-04-04 14:03:19 -07:00
parent 51023c3911
commit 318eace49d
1 changed files with 17 additions and 7 deletions
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24
util/crc32c.cc
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@ -313,12 +313,14 @@ static inline void Slow_CRC32(uint64_t* l, uint8_t const **p) {
table0_[c >> 24];
}
#ifdef __SSE4_2__
static inline void Fast_CRC32(uint64_t* l, uint8_t const **p) {
#ifdef __SSE4_2__
*l = _mm_crc32_u64(*l, LE_LOAD64(*p));
*p += 8;
}
#else
Slow_CRC32(l, p);
#endif
}
template<void (*CRC32)(uint64_t*, uint8_t const**)>
uint32_t ExtendImpl(uint32_t crc, const char* buf, size_t size) {
@ -363,14 +365,22 @@ uint32_t ExtendImpl(uint32_t crc, const char* buf, size_t size) {
return l ^ 0xffffffffu;
}
// Detect if SS42 or not.
static bool isSSE42() {
#if defined(__GNUC__) && defined(__x86_64__) && !defined(IOS_CROSS_COMPILE)
uint32_t c_;
uint32_t d_;
__asm__("cpuid" : "=c"(c_), "=d"(d_) : "a"(1) : "ebx");
return c_ & (1U << 20); // copied from CpuId.h in Folly.
#else
return false;
#endif
}
typedef uint32_t (*Function)(uint32_t, const char*, size_t);
static inline Function Choose_Extend() {
#ifdef __SSE4_2__
return ExtendImpl<Fast_CRC32>;
#else
return ExtendImpl<Slow_CRC32>;
#endif
return isSSE42() ? ExtendImpl<Fast_CRC32> : ExtendImpl<Slow_CRC32>;
}
Function ChosenExtend = Choose_Extend();