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Date: Mon, 13 Mar 2006 01:34:31 -0800
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To: Marcus Boerger <helly@php.net>
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Subject: Re: [PHP-DEV] Calling performance geeks
From: rasmus@lerdorf.com (Rasmus Lerdorf)

Marcus Boerger wrote:
> Hello Rasmus,
> 
>   not a thing for 5.1 or 4.4 but in 5.2 we could change to a case
> insensitive comparison function. That would allow us to change nearly
> all of strcasecmp to memcmp. And in may cases it means one less
> allocation. And it also means a lot of less code. The casinsensitive
> comparision is pretty easy because we can use a 256 byte translation
> table that can be provided as a static const table. On a X86 systems
> we could also provide that in assembler. That would give us the
> possibility to use the XLAT instruction that would otherwise not be
> used (maybe newer optimizing compiler know about it though).
> 
> Maybe it is worse trying to bring it in and checking how much slower
> we are getting with it. If the numbers look promising we could go for
> the change then.
> 
> A word on HEAD/Unicode. If we use a case insensitivity semantics where
> only the normal ascii characters are lowercased we can use the same
> table based approach.
> 
> Anyway from looking at the output the best optimization was brought up by
> you already. Using jit for the ap_* stuff.

Well, that doesn't come anywhere near the radar here actually.  The 
300k+ strcasecmp calls are coming from the qsort in Apache, not from 
PHP.  Even then, 300k strcasecmp calls is minor here.  So I doubt you 
could even measure the effect of that change.

-Rasmus