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Even if SSE doesn't gain us anything, going 32bit is a clear win.

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Alcaro 2014-02-22 18:33:47 +01:00
parent 9d8bf3cffa
commit 30477c2518
1 changed files with 23 additions and 11 deletions
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34
rewind.c
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@ -340,23 +340,35 @@ static inline size_t find_same(const uint16_t * a, const uint16_t * b)
static inline size_t find_same(const uint16_t * a, const uint16_t * b)
{
const uint16_t * a_org=a;
//Comparing two or three words makes no real difference.
//With two, the smaller blocks are less likely to be chopped up elsewhere due to 64KB;
// with three, we get larger blocks which should be a minuscle bit faster to decompress,
// but probably a little slower to compress. Since compression is more bottleneck than decompression is, we favor that.
while (a[0]!=b[0] || a[1]!=b[1])
#ifdef NO_UNALIGNED_MEM
if ((uintptr_t)a & (sizeof(uint32_t)-1) && *a!=*b)
{
a++;
b++;
//Optimize this by only checking one at the time for as long as possible.
while (*a!=*b)
}
if (*a!=*b)
#endif
{
//With this, it's random whether two consecutive identical words are caught.
//Luckily, compression rate is the same for both cases, and three is always caught.
//(We prefer to miss two-word blocks, anyways; fewer iterations of the outer loop, as well as in the decompressor.)
const uint32_t* a_big=(const uint32_t*)a;
const uint32_t* b_big=(const uint32_t*)b;
while (*a_big!=*b_big)
{
a++;
b++;
a_big++;
b_big++;
}
a=(const uint16_t*)a_big;
b=(const uint16_t*)b_big;
if (a!=a_org && a[-1]==b[-1])
{
a--;
b--;
}
}
return a-a_org;
}
#endif