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RE: [PATCH][AArch64] Enable -frename-registers at -O2 and higher
- From: Evandro Menezes <e dot menezes at samsung dot com>
- To: 'James Greenhalgh' <james dot greenhalgh at arm dot com>, 'Kyrill Tkachov' <kyrylo dot tkachov at foss dot arm dot com>
- Cc: 'GCC Patches' <gcc-patches at gcc dot gnu dot org>, 'Marcus Shawcroft' <marcus dot shawcroft at arm dot com>, 'Richard Earnshaw' <Richard dot Earnshaw at arm dot com>, nd at arm dot com, philipp dot tomsich at theobroma-systems dot com, pinskia at gmail dot com, jim dot wilson at linaro dot org, benedikt dot huber at theobroma-systems dot com, 'Wilco Dijkstra' <Wilco dot Dijkstra at arm dot com>
- Date: Wed, 15 Jun 2016 14:39:58 -0500
- Subject: RE: [PATCH][AArch64] Enable -frename-registers at -O2 and higher
- Authentication-results: sourceware.org; auth=none
- References: <57485097 dot 4040704 at foss dot arm dot com> <20160531095640 dot GA17686 at arm dot com>
> On Fri, May 27, 2016 at 02:50:15PM +0100, Kyrill Tkachov wrote:
> >
> > As mentioned in
> > https://gcc.gnu.org/ml/gcc-patches/2016-05/msg00297.html,
> > frename-registers registers can be beneficial for aarch64 and the
> > patch at https://gcc.gnu.org/ml/gcc-patches/2016-05/msg01618.html
> > resolves the AESE/AESMC fusion issue that it exposed in the aarch64
> > backend. So this patch enables the pass for aarch64 at -O2 and above.
> >
> > Ok for trunk?
>
> As you're proposing to have this on by default, I'd like to give a chance
to
> hear whether there is consensus as to this being the right choice for the
> thunderx, xgene1, exynos-m1 and qdf24xx subtargets.
Though there's a slight (<1%) overall improvement on Exynos M1, there just
were too many significant (<-3%) regressions for a few significant
improvements for me to be comfortable with -frename-registers being a
generic default for AArch64.
I'll run some larger benchmarks tonight, but I'm leaning towards having it
as a target specific extra tuning option.
Thank you,
--
Evandro Menezes Austin, TX
PS: I'm fine with refactoring aarch_option_optimization_table to
aarch64_option_optimization_table.