Re: [AArch64] Remove AARCH64_EXTRA_TUNE_RECIP_SQRT from Cortex-A57 tuning

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

On Mon, Feb 01, 2016 at 02:00:01PM +0000, James Greenhalgh wrote:
> On Mon, Jan 25, 2016 at 11:20:46AM +0000, James Greenhalgh wrote:
> > On Mon, Jan 11, 2016 at 12:04:43PM +0000, James Greenhalgh wrote:
> > > 
> > > Hi,
> > > 
> > > I've seen a couple of large performance issues caused by expanding
> > > the high-precision reciprocal square root for Cortex-A57, so I'd like
> > > to turn it off by default.
> > > 
> > > This is good for art (~2%) from Spec2000, bad (~3.5%) for fma3d from
> > > Spec2000, good (~5.5%) for gromcas from Spec2006, and very good (>10%) for
> > > some private microbenchmark kernels which stress the divide/sqrt/multiply
> > > units. It therefore seems to me to be the correct choice to make across
> > > a number of workloads.
> > > 
> > > Bootstrapped and tested on aarch64-none-linux-gnu with no issues.
> > > 
> > > OK?
> > 
> > *Ping*
> 
> *pingx2*

*ping^3*

Thanks,
James

> > > ---
> > > 2015-12-11  James Greenhalgh  <james.greenhalgh@arm.com>
> > > 
> > > 	* config/aarch64/aarch64.c (cortexa57_tunings): Remove
> > > 	AARCH64_EXTRA_TUNE_RECIP_SQRT.
> > > 
> > 
> > > diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> > > index 1d5d898..999c9fc 100644
> > > --- a/gcc/config/aarch64/aarch64.c
> > > +++ b/gcc/config/aarch64/aarch64.c
> > > @@ -484,8 +484,7 @@ static const struct tune_params cortexa57_tunings =
> > >    0,	/* max_case_values.  */
> > >    0,	/* cache_line_size.  */
> > >    tune_params::AUTOPREFETCHER_WEAK,	/* autoprefetcher_model.  */
> > > -  (AARCH64_EXTRA_TUNE_RENAME_FMA_REGS
> > > -   | AARCH64_EXTRA_TUNE_RECIP_SQRT)	/* tune_flags.  */
> > > +  (AARCH64_EXTRA_TUNE_RENAME_FMA_REGS)	/* tune_flags.  */
> > >  };
> > >  
> > >  static const struct tune_params cortexa72_tunings =
> > 
>