[RFC] Add fast path for strcoll and strcasecmp

[Leonhard Holz]

Am 24.11.2014 00:47, schrieb Ondřej Bílka:
> On Sun, Nov 23, 2014 at 11:52:06PM +0100, Leonhard Holz wrote:
>> Hi Ondřej,
>>
>> as far as I understood, the current strcoll implementation scans
>> both strings for collation sequences and compares the weights of
>> them, whereby a collation sequence can be multiple bytes long. So
>> whatever strcmp_l returns as index, you would need a general way of
>> finding the start of the collation sequence this index is in.
>> Unfortunately I cannot tell if or how this can be done.
>>
> As I wrote below you do not have to do that. Just precompute a table that
> is zero for characters that are part of some collation sequence and use
> old method when one of compared characters is in that table.
>

Ok, I understand the idea and it would be great if it worked. BTW do you 
know how UTF-8 chars above 7F are handled?

>  From performance perspective these are not problem as they should be
> infrequent enough. Ignored ones are worse as they could make otherwise
> identical long prefixes different.
>
>
>> BTW I have implemented a benchmark for strcoll that is
>> not-yet-pushed because I didn't manage to patch the bench-tests
>> Makefile to generate additionally needed locales
>> (https://sourceware.org/ml/libc-alpha/2014-10/msg00431.html).
>>

I can send you the test files if you like.

Leonhard