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Optimize for lp64

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Summary:
Some code reorganization in-preparation for replacing with a hardware
instruction.

* Use u64 for some of the key types
* Use an ALIGN macro so code is easier to read

Test Plan: crc32c_test

Reviewers: dhruba

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D3135
This commit is contained in:
Arun Sharma 2012-05-04 00:26:14 +00:00
parent 37d0dcb9b1
commit 921a48428e
1 changed files with 14 additions and 8 deletions
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22
util/crc32c.cc
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@ -286,7 +286,10 @@ static inline uint32_t LE_LOAD32(const uint8_t *p) {
uint32_t Extend(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;
uint32_t l = crc ^ 0xffffffffu;
uint64_t l = crc ^ 0xffffffffu;
// Align n to (1 << m) byte boundary
#define ALIGN(n, m) ((n + ((1 << m) - 1)) & ~((1 << m) - 1))
#define STEP1 do { \
int c = (l & 0xff) ^ *p++; \
@ -300,31 +303,34 @@ uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
table1_[(c >> 16) & 0xff] ^ \
table0_[c >> 24]; \
} while (0)
#define STEP8 do { STEP4; STEP4; } while(0)
// Point x at first 4-byte aligned byte in string. This might be
// Point x at first 16-byte aligned byte in string. This might be
// just past the end of the string.
const uintptr_t pval = reinterpret_cast<uintptr_t>(p);
const uint8_t* x = reinterpret_cast<const uint8_t*>(((pval + 3) >> 2) << 2);
const uint8_t* x = reinterpret_cast<const uint8_t*>(ALIGN(pval, 4));
if (x <= e) {
// Process bytes until finished or p is 4-byte aligned
// Process bytes until finished or p is 16-byte aligned
while (p != x) {
STEP1;
}
}
// Process bytes 16 at a time
while ((e-p) >= 16) {
STEP4; STEP4; STEP4; STEP4;
STEP8; STEP8;
}
// Process bytes 4 at a time
while ((e-p) >= 4) {
STEP4;
// Process bytes 8 at a time
while ((e-p) >= 8) {
STEP8;
}
// Process the last few bytes
while (p != e) {
STEP1;
}
#undef STEP8
#undef STEP4
#undef STEP1
#undef ALIGN
return l ^ 0xffffffffu;
}