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Re: [PATCH] Atom: Enabling unroll at O2 optimization level


On Tue, Apr 10, 2012 at 8:43 PM, Igor Zamyatin <izamyatin@gmail.com> wrote:
> Hi All!
>
> Here is a patch that enables unroll at O2 for Atom.
>
> This gives good performance boost on EEMBC 2.0 (~+8% in Geomean for 32
> bits) with quite moderate code size increase (~5% for EEMBC2.0, 32
> bits).

5% is not moderate.  Your patch does enable unrolling at -O2 but not -O3,
why? Why do you disable register renaming?  check_imull requires a function
comment.

This completely looks like a hack for EEMBC2.0, so it's definitely not ok.

-O2 is not supposed to give best benchmark results.

Thanks,
Richard.

>
> Tested for i386 and x86-64, ok for trunk?
>
> Thanks,
> Igor
>
> ChangeLog:
>
> 2012-04-10 ?Yakovlev Vladimir ?<vladimir.b.yakovlev@intel.com>
>
> ? ? ? ?* gcc/config/i386/i386.c (check_imull): New routine.
> ? ? ? ?(ix86_loop_unroll_adjust): New target hook.
> ? ? ? ?(ix86_option_override_internal): Enable unrolling on Atom at -O2.
> ? ? ? ?(TARGET_LOOP_UNROLL_ADJUST): New define.


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