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| author | Yann Collet <cyan@fb.com> | 2018-02-12 05:03:39 (GMT) |
|---|---|---|
| committer | Yann Collet <cyan@fb.com> | 2018-02-12 08:01:58 (GMT) |
| commit | d3a13397d921d9d2ebae56d0503d23c73fee39b1 (patch) | |
| tree | 402e1509f6e2a5965a142e7af9c526ededa2a2d0 /lib | |
| parent | 2b674bf02f698b565b4525a36cdf4651899b88d1 (diff) | |
| download | lz4-d3a13397d921d9d2ebae56d0503d23c73fee39b1.zip lz4-d3a13397d921d9d2ebae56d0503d23c73fee39b1.tar.gz lz4-d3a13397d921d9d2ebae56d0503d23c73fee39b1.tar.bz2 | |
slight hc speed benefit (~+1%)
by optimizing countback
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/lz4hc.c | 31 |
1 files changed, 10 insertions, 21 deletions
diff --git a/lib/lz4hc.c b/lib/lz4hc.c index 9f59e80..c888ee1 100644 --- a/lib/lz4hc.c +++ b/lib/lz4hc.c @@ -123,10 +123,12 @@ LZ4_FORCE_INLINE int LZ4HC_countBack(const BYTE* const ip, const BYTE* const match, const BYTE* const iMin, const BYTE* const mMin) { - int back=0; - while ( (ip+back > iMin) - && (match+back > mMin) - && (ip[back-1] == match[back-1])) + int back = 0; + int const min = (int)MAX(iMin - ip, mMin - match); + assert(ip >= iMin); assert((size_t)(ip-iMin) < (1U<<31)); + assert(match >= mMin); assert((size_t)(match - mMin) < (1U<<31)); + while ( (back > min) + && (ip[back-1] == match[back-1]) ) back--; return back; } @@ -223,17 +225,7 @@ LZ4_FORCE_INLINE int LZ4HC_InsertAndGetWiderMatch ( if (LZ4_read16(iLowLimit + longest - 1) == LZ4_read16(matchPtr - delta + longest - 1)) { if (LZ4_read32(matchPtr) == pattern) { int mlt = MINMATCH + LZ4_count(ip+MINMATCH, matchPtr+MINMATCH, iHighLimit); - #if 0 - /* more generic but unfortunately slower on clang */ - int const back = LZ4HC_countBack(ip, matchPtr, iLowLimit, lowPrefixPtr); - #else - int back = 0; - while ( (ip+back > iLowLimit) - && (matchPtr+back > lowPrefixPtr) - && (ip[back-1] == matchPtr[back-1])) { - back--; - } - #endif + int const back = delta ? LZ4HC_countBack(ip, matchPtr, iLowLimit, lowPrefixPtr) : 0; mlt -= back; if (mlt > longest) { @@ -252,10 +244,7 @@ LZ4_FORCE_INLINE int LZ4HC_InsertAndGetWiderMatch ( mlt = LZ4_count(ip+MINMATCH, matchPtr+MINMATCH, vLimit) + MINMATCH; if ((ip+mlt == vLimit) && (vLimit < iHighLimit)) mlt += LZ4_count(ip+mlt, base+dictLimit, iHighLimit); - while ( (ip+back > iLowLimit) - && (matchIndex+back > lowLimit) - && (ip[back-1] == matchPtr[back-1])) - back--; + back = delta ? LZ4HC_countBack(ip, matchPtr, iLowLimit, dictBase+lowLimit) : 0; mlt -= back; if (mlt > longest) { longest = mlt; @@ -333,7 +322,7 @@ LZ4_FORCE_INLINE int LZ4HC_encodeSequence ( size_t length; BYTE* const token = (*op)++; -#if defined(LZ4_DEBUG) && (LZ4_DEBUG >= 2) +#if defined(LZ4_DEBUG) && (LZ4_DEBUG >= 6) static const BYTE* start = NULL; static U32 totalCost = 0; U32 const pos = (start==NULL) ? 0 : (U32)(*anchor - start); @@ -343,7 +332,7 @@ LZ4_FORCE_INLINE int LZ4HC_encodeSequence ( U32 const cost = 1 + llAdd + ll + 2 + mlAdd; if (start==NULL) start = *anchor; /* only works for single segment */ //g_debuglog_enable = (pos >= 2228) & (pos <= 2262); - DEBUGLOG(2, "pos:%7u -- literals:%3u, match:%4i, offset:%5u, cost:%3u + %u", + DEBUGLOG(6, "pos:%7u -- literals:%3u, match:%4i, offset:%5u, cost:%3u + %u", pos, (U32)(*ip - *anchor), matchLength, (U32)(*ip-match), cost, totalCost); |