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Re: [PATCH] Faster strlen
On Tue, Oct 9, 2012 at 8:37 AM, OndÅej BÃlka <neleai@seznam.cz> wrote:
> On Tue, Oct 09, 2012 at 08:02:33AM -0700, H.J. Lu wrote:
>> On Sun, Oct 7, 2012 at 10:27 AM, OndÅej BÃlka <neleai@seznam.cz> wrote:
>> > Hello, I investigated strlen bit more and improved pminub variant.
>> >
>> > I got upto 10% speedup by unrolling main loop. I did not measured
>> > difference when I unrolled loop more.
>> >
>> > I also benchmarked atom and added variant which is identical to
>> > strlen-sse2-pminub except bsf is replaced by table lookup.
>> >
>> > Last addition is attempt to generate VEX encoded strlen. I need only to
>> > pass -mavx flag when compiling strlen_avx.S but do not know how.
>> >
>>
>> Please rename strlen_atom.S to strlen-no-bsf.S since it
>> depends on bit_Slow_BSF, not Atom.
>
> Perhaps we could add bit_Atom or something similar.
> I plan to use other atom specific optimizations like instruction
> pairing. Strlen is bad example for this, all that I could get are
> perhaps 2 cycles when zeroing xmm registers.
>
IFUNC feature name should be processor independent.
Please don't use processor name in IFUNC features.
--
H.J.