From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Rast Subject: [PATCH] Choose XDL_FAST_HASH code on sizeof(long) instead of __WORDSIZE Date: Tue, 1 May 2012 10:36:51 +0200 Message-ID: <399c9a1f0dd548da3144eff3c50d04a8f343ab24.1335860033.git.trast@student.ethz.ch> References: <7v4ns0cy3l.fsf@alter.siamese.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain Cc: Brian Gernhardt , , Thomas Rast To: Junio C Hamano X-From: git-owner@vger.kernel.org Tue May 01 10:37:03 2012 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1SP8Zx-0005Ox-A2 for gcvg-git-2@plane.gmane.org; Tue, 01 May 2012 10:37:01 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753450Ab2EAIg5 (ORCPT ); Tue, 1 May 2012 04:36:57 -0400 Received: from edge10.ethz.ch ([82.130.75.186]:20123 "EHLO edge10.ethz.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752561Ab2EAIgz (ORCPT ); Tue, 1 May 2012 04:36:55 -0400 Received: from CAS21.d.ethz.ch (172.31.51.111) by edge10.ethz.ch (82.130.75.186) with Microsoft SMTP Server (TLS) id 14.2.283.3; Tue, 1 May 2012 10:36:51 +0200 Received: from thomas.inf.ethz.ch (188.155.176.28) by CAS21.d.ethz.ch (172.31.51.111) with Microsoft SMTP Server (TLS) id 14.1.355.2; Tue, 1 May 2012 10:36:51 +0200 X-Mailer: git-send-email 1.7.10.512.g5bfc6 In-Reply-To: <7v4ns0cy3l.fsf@alter.siamese.dyndns.org> X-Originating-IP: [188.155.176.28] Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: 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 Signed-off-by: Thomas Rast --- Incidentally, on the OS X machine I have access to, the difference is even bigger, something like 14% for 'log -p -3000'. I'm too lazy to work out the exact numbers since the perf code doesn't work there. xdiff/xutils.c | 52 +++++++++++++++++++++++----------------------------- 1 file changed, 23 insertions(+), 29 deletions(-) diff --git a/xdiff/xutils.c b/xdiff/xutils.c index e05b5c9..1b3b471 100644 --- 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; -- 1.7.10.512.g5bfc6