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Decompose step into Two Variables

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This avoids an additional addition, at the cost of an additional variable.
This commit is contained in:
W. Felix Handte 2021-12-10 15:52:30 -05:00
parent 22501cd283
commit ace6a7e746
1 changed files with 12 additions and 9 deletions
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21
lib/compress/zstd_fast.c
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@ -99,7 +99,7 @@ ZSTD_compressBlock_fast_noDict_generic(
U32* const hashTable = ms->hashTable;
U32 const hlog = cParams->hashLog;
/* support stepSize of 0 */
size_t const stepSize = cParams->targetLength + !(cParams->targetLength) - 1;
size_t const stepSize = cParams->targetLength + !(cParams->targetLength);
const BYTE* const base = ms->window.base;
const BYTE* const istart = (const BYTE*)src;
const U32 endIndex = (U32)((size_t)(istart - base) + srcSize);
@ -128,7 +128,8 @@ ZSTD_compressBlock_fast_noDict_generic(
const BYTE* match0;
size_t mLength;
size_t step;
size_t step0;
size_t step1;
const BYTE* nextStep;
const size_t kStepIncr = (1 << (kSearchStrength - 1));
@ -144,13 +145,14 @@ ZSTD_compressBlock_fast_noDict_generic(
/* start each op */
_start: /* Requires: ip0 */
step = 1;
step0 = 1;
step1 = stepSize;
nextStep = ip0 + kStepIncr;
/* calculate positions, ip0 - anchor == 0, so we skip step calc */
ip1 = ip0 + step;
ip2 = ip1 + step + stepSize;
ip3 = ip2 + step;
ip1 = ip0 + step0;
ip2 = ip1 + step1;
ip3 = ip2 + step0;
if (ip3 >= ilimit) {
goto _cleanup;
@ -234,15 +236,16 @@ _start: /* Requires: ip0 */
if (ip2 >= nextStep) {
PREFETCH_L1(ip1 + 64);
PREFETCH_L1(ip1 + 128);
step++;
step0++;
step1++;
nextStep += kStepIncr;
}
/* advance to next positions */
ip0 = ip1;
ip1 = ip2;
ip2 = ip2 + step + stepSize;
ip3 = ip2 + step;
ip2 = ip2 + step1;
ip3 = ip2 + step0;
} while (ip3 < ilimit);
_cleanup: