[PATCH][AArch64] Enable AES fusion with -mcpu=generic

James Greenhalgh james.greenhalgh@arm.com
Fri Mar 17 10:56:00 GMT 2017


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



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