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crc32: build a whole special Extend function for SSE 4.2.

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Disassembling the Extend function shows something that looks
much more healthy now. The SSE 4.2 instructions are right
there in the body of the function.

Intel(R) Core(TM) i7-3540M CPU @ 3.00GHz

Before:

crc32c: 1.305 micros/op 766260 ops/sec; 2993.2 MB/s (4K per op)

After:

crc32c: 0.442 micros/op 2263843 ops/sec; 8843.1 MB/s (4K per op)
This commit is contained in:
Albert Strasheim 2014-04-02 15:15:57 -07:00
parent 284c365b77
commit 56ca75e89e
1 changed files with 14 additions and 13 deletions
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27
util/crc32c.cc
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@ -334,19 +334,8 @@ static bool isSSE42() {
#endif
}
typedef void (*Function)(uint64_t*, uint8_t const**);
static inline Function Choose_CRC32() {
return isSSE42() ? Fast_CRC32 : Slow_CRC32;
}
static Function func = Choose_CRC32();
static inline void CRC32(uint64_t* l, uint8_t const **p) {
func(l, p);
}
uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
template<void (*CRC32)(uint64_t*, uint8_t const**)>
uint32_t ExtendImpl(uint32_t crc, const char* buf, size_t size) {
const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
const uint8_t *e = p + size;
uint64_t l = crc ^ 0xffffffffu;
@ -388,5 +377,17 @@ uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
return l ^ 0xffffffffu;
}
typedef uint32_t (*Function)(uint32_t, const char*, size_t);
static inline Function Choose_Extend() {
return isSSE42() ? ExtendImpl<Fast_CRC32> : ExtendImpl<Slow_CRC32>;
}
Function ChosenExtend = Choose_Extend();
uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
return ChosenExtend(crc, buf, size);
}
} // namespace crc32c
} // namespace rocksdb