[PATCH 2/4][AArch64] Increase the loop peeling limit

James Greenhalgh james.greenhalgh@arm.com
Fri Nov 20 11:53:00 GMT 2015

On Thu, Nov 19, 2015 at 04:04:41PM -0600, Evandro Menezes wrote:
> On 11/05/2015 02:51 PM, Evandro Menezes wrote:
> >2015-11-05  Evandro Menezes <e.menezes@samsung.com>
> >
> >   gcc/
> >
> >       * config/aarch64/aarch64.c (aarch64_override_options_internal):
> >       Increase loop peeling limit.
> >
> >This patch increases the limit for the number of peeled insns.
> >With this change, I noticed no major regression in either
> >Geekbench v3 or SPEC CPU2000 while some benchmarks, typically FP
> >ones, improved significantly.
> >
> >I tested this tuning on Exynos M1 and on A57.  ThunderX seems to
> >benefit from this tuning too.  However, I'd appreciate comments
> >from other stakeholders.
> Ping.

I'd like to leave this for a call from the port maintainers. I can see why
this leads to more opportunities for vectorization, but I'm concerned about
the wider impact on code size. Certainly I wouldn't expect this to be our
default at -O2 and below.

My gut feeling is that this doesn't really belong in the back-end (there are
presumably good reasons why the default for this parameter across GCC has
fluctuated from 400 to 100 to 200 over recent years), but as I say, I'd
like Marcus or Richard to make the call as to whether or not we take this

For now, I'd drop it from the series (it stands alone anyway).


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