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Re: [PATCH][AArch64] Enable AES fusion with -mcpu=generic
- From: James Greenhalgh <james dot greenhalgh at arm dot com>
- To: Jim Wilson <jim dot wilson at linaro dot org>
- Cc: Andrew Pinski <apinski at cavium dot com>, Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, "Evandro Menezes" <e dot menezes at samsung dot com>, "Andrew dot pinski at cavium dot com" <Andrew dot pinski at cavium dot com>, nd <nd at arm dot com>
- Date: Fri, 17 Mar 2017 10:55:26 +0000
- Subject: Re: [PATCH][AArch64] Enable AES fusion with -mcpu=generic
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On Thu, Mar 16, 2017 at 08:26:42PM -0700, Jim Wilson wrote:
> On Thu, Mar 16, 2017 at 11:01 AM, Andrew Pinski <apinski@cavium.com> wrote:
> > On Thu, Mar 16, 2017 at 10:22 AM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote:
> >> Many supported cores implement fusion of AES instructions. When fusion
> >> happens it can give a significant performance gain. If not, scheduling
> >> fusion candidates next to each other has almost no effect on performance.
> >> Due to the high benefit/low cost it makes sense to enable AES fusion with
> >> -mcpu=generic so that cores that support it always benefit. Any objections?
>
> No objection. I'm not currently tracking performance of -mcpu=generic
> on falkor, so I'm not very concerned about changes to the generic
> tuning structure.
Thanks for the feedback Jim, Andrew.
This patch is OK for trunk. As Richard pointed out on the branch costs
thread, if we had a bug here we'd likely have seen it by now on those
cores which do enable the fusion.
Thanks,
James