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Re: Enabling -ftree-slp-vectorize on -O2/Os
- From: Allan Sandfeld Jensen <linux at carewolf dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: GCC Development <gcc at gcc dot gnu dot org>
- Date: Mon, 28 May 2018 17:50:57 +0200
- Subject: Re: Enabling -ftree-slp-vectorize on -O2/Os
- References: <2659301.XPQk3P0qmd@twilight> <5A85555D-FF52-4666-88EE-FFBD8C498294@gmail.com> <CAFiYyc1Lp8v0W2zpR-pG1At=WbqruHPOAPchRYZcn+c1cSGfcA@mail.gmail.com>
On Montag, 28. Mai 2018 12:58:20 CEST Richard Biener wrote:
> compile-time effects of the patch on that. Embedded folks may want to rhn
> their favorite benchmark and report results as well.
>
> So I did a -O2 -march=haswell [-ftree-slp-vectorize] SPEC CPU 2006 compile
> and run and the compile-time
> effect where measurable (SPEC records on a second granularity) is within
> one second per benchmark
> apart from 410.bwaves (from 3s to 5s) and 481.wrf (76s to 78s).
> Performance-wise I notice significant
> slowdowns for SPEC FP and some for SPEC INT (I only did a train run
> sofar). I'll re-run with ref input now
> and will post those numbers.
>
If you continue to see slowdowns, could you check with either no avx, or with
-mprefer-avx128? The occational AVX256 instructions might be downclocking the
CPU. But yes that would be a problem for this change on its own.
'Allan