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Re: String Functions for x86-64

From: Ulrich Drepper <drepper at redhat dot com>
To: "Menezes, Evandro" <evandro dot menezes at amd dot com>
Cc: libc-alpha at sourceware dot org, "Meissner, Michael" <michael dot meissner at amd dot com>
Date: Tue, 02 May 2006 10:10:38 -0700
Subject: Re: String Functions for x86-64
References: <84EA05E2CA77634C82730353CBE3A84304BA4116@SAUSEXMB1.amd.com>

Menezes, Evandro wrote:
> Here are the remaining routines bundled with the others previously submitted.  Their performance is generally better than the existing ones on x86-64 processors.

Where is the (reproducible) data to support that claim?  I have no
reason to believe you.

What are the boundary conditions?  E.g., what alignment of the
parameters did of use during the tests, etc.

>  strncmp, however, can perform a tad slower for some tiny blocks, but is faster, up to several times, for blocks 16 bytes long or larger.

But the strings passed to strncmp during normal operation are in 99% of
all cases <= 16 chars.  I have data to prove that.  The fact that you
gloss over this problem means you haven't done your homework.  You are
optimizing for the wrong use cases.

-- 
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â

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References:
- RE: String Functions for x86-64
  - From: Menezes, Evandro

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