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bug#17229: [PATCH 2/2] grep: speed-up by using memchr() in Boyer-Moore s

From: Paul Eggert
Subject: bug#17229: [PATCH 2/2] grep: speed-up by using memchr() in Boyer-Moore searching
Date: Sun, 27 Apr 2014 13:32:57 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

Norihiro Tanaka wrote:
Could you try above cases?

Thanks, you're observing a 2.7x performance speedup with macros on your platform and your benchmark. With the same patch, I observed only a 1.18x speedup on the same benchmark. As usual, I'm testing with AMD Phenom II X4 910e + GCC 4.9.0 + Fedora 20 + default (-O2) optimization. I'm curious about why you're observing a much bigger performance difference with macros. What platform are you using?

Anyway, an 18% speedup is still a speedup, so I looked into it. GCC 4.9.0 misses a non-obvious opportunity for function inlining. I installed a tweak (attached) that should make the inlining opportunity obvious to compilers nowadays. On my platform this gave a 28% speedup, i.e., a bit better than the macro-using patch would have.

Attachment: 0001-kwset-improve-performance-by-inlining-more.patch
Description: Text document

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