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* Thanks, James > --- > 2015-12-11 James Greenhalgh <james.greenha...@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 =
