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Merge branch 'tr/xdiff-fast-hash' into next

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Use word-at-a-time comparison to find end of line or NUL (end of buffer),
borrowed from the linux-kernel discussion.

By Thomas Rast
* tr/xdiff-fast-hash:
  xdiff: choose XDL_FAST_HASH code on sizeof(long) instead of __WORDSIZE
This commit is contained in:
Junio C Hamano
2012-05-01 16:30:43 -07:00
parent b20428cbfe 6f1af028ce
commit 5155b9870c
1 changed files with 23 additions and 29 deletions
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52
xdiff/xutils.c
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@@ -290,39 +290,33 @@ static inline unsigned long has_zero(unsigned long a)
return ((a - ONEBYTES) & ~a) & HIGHBITS;
}
#if __WORDSIZE == 64
/*
* Jan Achrenius on G+: microoptimized version of
* the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
* that works for the bytemasks without having to
* mask them first.
*/
static inline long count_masked_bytes(unsigned long mask)
{
return mask * 0x0001020304050608 >> 56;
if (sizeof(long) == 8) {
/*
* Jan Achrenius on G+: microoptimized version of
* the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
* that works for the bytemasks without having to
* mask them first.
*/
return mask * 0x0001020304050608 >> 56;
} else {
/*
* Modified Carl Chatfield G+ version for 32-bit *
*
* (a) gives us
* -1 (0, ff), 0 (ffff) or 1 (ffffff)
* (b) gives us
* 0 for 0, 1 for (ff ffff ffffff)
* (a+b+1) gives us
* correct 0-3 bytemask count result
*/
long a = (mask - 256) >> 23;
long b = mask & 1;
return a + b + 1;
}
}
#else /* 32-bit case */
/* Modified Carl Chatfield G+ version for 32-bit */
static inline long count_masked_bytes(long mask)
{
/*
* (a) gives us
* -1 (0, ff), 0 (ffff) or 1 (ffffff)
* (b) gives us
* 0 for 0, 1 for (ff ffff ffffff)
* (a+b+1) gives us
* correct 0-3 bytemask count result
*/
long a = (mask - 256) >> 23;
long b = mask & 1;
return a + b + 1;
}
#endif
unsigned long xdl_hash_record(char const **data, char const *top, long flags)
{
unsigned long hash = 5381;