@matheusbsbs / matheus-bagliano / commits / 6f1af028ce

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>

Thomas Rast committed May 1, 2012 at 12:23 UTC 6f1af028ce0654ef6233dff06701a989d5703bc4
1 file changed +23 -29
xdiff/xutils.c
+23 -29
@@ -290,39 +290,33 @@ static inline unsigned long has_zero(unsigned long a)
290 return ((a - ONEBYTES) & ~a) & HIGHBITS;
291 }
292
293 -#if __WORDSIZE == 64
294 -
295 -/*
296 - * Jan Achrenius on G+: microoptimized version of
297 - * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
298 - * that works for the bytemasks without having to
299 - * mask them first.
300 - */
293 static inline long count_masked_bytes(unsigned long mask)
294 {
303 - return mask * 0x0001020304050608 >> 56;
304 -}
305 -
306 -#else /* 32-bit case */
307 -
308 -/* Modified Carl Chatfield G+ version for 32-bit */
309 -static inline long count_masked_bytes(long mask)
310 -{
311 - /*
312 - * (a) gives us
313 - * -1 (0, ff), 0 (ffff) or 1 (ffffff)
314 - * (b) gives us
315 - * 0 for 0, 1 for (ff ffff ffffff)
316 - * (a+b+1) gives us
317 - * correct 0-3 bytemask count result
318 - */
319 - long a = (mask - 256) >> 23;
320 - long b = mask & 1;
321 - return a + b + 1;
295 + if (sizeof(long) == 8) {
296 + /*
297 + * Jan Achrenius on G+: microoptimized version of
298 + * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
299 + * that works for the bytemasks without having to
300 + * mask them first.
301 + */
302 + return mask * 0x0001020304050608 >> 56;
303 + } else {
304 + /*
305 + * Modified Carl Chatfield G+ version for 32-bit *
306 + *
307 + * (a) gives us
308 + * -1 (0, ff), 0 (ffff) or 1 (ffffff)
309 + * (b) gives us
310 + * 0 for 0, 1 for (ff ffff ffffff)
311 + * (a+b+1) gives us
312 + * correct 0-3 bytemask count result
313 + */
314 + long a = (mask - 256) >> 23;
315 + long b = mask & 1;
316 + return a + b + 1;
317 + }
318 }
319
324 -#endif
325 -
320 unsigned long xdl_hash_record(char const **data, char const *top, long flags)
321 {
322 unsigned long hash = 5381;