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xdiff: choose XDL_FAST_HASH code on sizeof(long) instead of __WORDSIZE

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Darwin does not define __WORDSIZE, and compiles the 32-bit code path
on 64-bit systems, resulting in a totally broken git.

I could not find an alternative -- other than the platform symbols
(__x86_64__ etc.) -- that does the test in the preprocessor.  However,
we can also just test for the size of a 'long', which is what really
matters here.  Any compiler worth its salt will leave only the branch
relevant for its platform, and indeed on Linux/GCC the numbers don't
change:

 Test                                  tr/darwin-xdl-fast-hash   origin/next              origin/master
 ------------------------------------------------------------------------------------------------------------------
 4000.1: log -3000 (baseline)          0.09(0.07+0.01)           0.09(0.07+0.01) -5.5%*   0.09(0.07+0.01) -4.1%
 4000.2: log --raw -3000 (tree-only)   0.47(0.41+0.05)           0.47(0.40+0.05) -0.5%    0.45(0.38+0.06) -3.5%.
 4000.3: log -p -3000 (Myers)          1.81(1.67+0.12)           1.81(1.67+0.13) +0.3%    1.99(1.84+0.12) +10.2%***
 4000.4: log -p -3000 --histogram      1.79(1.66+0.11)           1.80(1.67+0.11) +0.4%    1.96(1.82+0.10) +9.2%***
 4000.5: log -p -3000 --patience       2.17(2.02+0.13)           2.20(2.04+0.13) +1.3%.   2.33(2.18+0.13) +7.4%***
 ------------------------------------------------------------------------------------------------------------------
 Significance hints:  '.' 0.1  '*' 0.05  '**' 0.01  '***' 0.001

Noticed-by: Brian Gernhardt <brian@gernhardtsoftware.com>
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Thomas Rast 2012-05-01 12:23:20 +02:00 committed by Junio C Hamano
parent 6942efcfa9
commit 6f1af028ce
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;