Re: [AArch64] Cortex-A57 Choose some new branch costs.

[James Greenhalgh <james.greenhalgh@arm.com>]

On Fri, Nov 13, 2015 at 11:40:56AM +0100, Richard Biener wrote:
> On Fri, Nov 13, 2015 at 11:13 AM, James Greenhalgh
> <james.greenhalgh@arm.com> wrote:
> >
> > Hi,
> >
> > With all the work that has recently gone in to ifcvt, I thought I'd revisit
> > the branch cost settings for Cortex-A57. After a run of experiments [1],
> > I found {1, 3} to be the sweet spot, giving a small set of performance
> > improvements across some popular benchmarks.
> >
> > I'd therefore like to propose changing the branch cost to those numbers.
> >
> > Patch bootstrapped tuning for Cortex-A57 with no issues. I'll revisit
> > the same for Cortex-A53.
> >
> > OK?
> 
> Can you re-do the experiment with adding a LOGICAL_OP_NON_SHORT_CIRCUIT
> target macro for aarch64?  It's fallback uses BRANCH_COST (see fold-const.c
> and tree-ssa-ifcombine.c)

This didn't drastically change the results for the workloads I was
using as benchmarks. I'd still pick {1, 3} out as the winner.

Thanks,
James

> > ---
> > 2015-11-12  James Greenhalgh  <james.greenhalgh@arm.com>
> >
> >         * config/aarch64/aarch64.c (cortexa57_branch_costs): New.
> >         (cortexa57_tunings): Use it.
> >
>