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

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>

diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index e05b5c96aaa274f79f7d512459b35885be9e8d4d..1b3b471ac86a30474e3acabea3d2df3b6da072d8 100644 (file)
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c
@@ -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;
-}
-
-#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;
+       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;
+       }
 }
 
-#endif
-
 unsigned long xdl_hash_record(char const **data, char const *top, long flags)
 {
        unsigned long hash = 5381;