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SubjectRe: Big git diff speedup by avoiding x86 "fast string" memcmp
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From: Boaz Harrosh <bharrosh@panasas.com>
Date: Wed, 15 Dec 2010 15:15:09 +0200

> I agree that the byte-compare or long-compare should give you very close
> results in modern pipeline CPUs. But surly 12 increments-and-test should
> show up against 3 (or even 2). I would say it must be a better plan.

For strings of these lengths the setup code necessary to initialize
the inner loop and the tail code to handle the sub-word ending cases
eliminate whatever gains there are.

I know this as I've been hacking on assembler optimized strcmp() and
memcmp() in my spare time over the past year or so.


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