On Thu, Jul 14, 2022 at 04:12:14PM -0500, Segher Boessenkool wrote:
> On Thu, Jul 14, 2022 at 11:20:56AM -0400, Michael Meissner wrote:
> > I have applied the patch to GCC 12.
> >
> > | From 22736f3d0d4fb8ce4afb3230023f8accdb03a623 Mon Sep 17 00:00:00 2001
> > | From: Michael Meissner <meiss...@linux.ibm.com>
> > | Date: Thu, 14 Jul 2022 11:16:08 -0400
> > | Subject: [PATCH] [BACKPORT] Disable generating load/store vector pairs
> > for block copies.
> >
> > Testing has found that using load and store vector pair for block copies
> > can result in a slow down on power10. This patch disables using the
> > vector pair instructions for block copies if we are tuning for power10.
> >
> > 2022-06-11 Michael Meissner <meiss...@linux.ibm.com>
> >
> > gcc/
> >
> > * config/rs6000/rs6000.cc (rs6000_option_override_internal): Do
> > not generate block copies with vector pair instructions if we are
> > tuning for power10. Back port from master branch.
>
> You never posted the trunk version of this, so that never was approved
> either.
I did post the trunk version on June 10th, and your only comment was fix the
commit message, which I thought I did in the commit.
> > +++ b/gcc/config/rs6000/rs6000.cc
> > @@ -4151,7 +4151,10 @@ rs6000_option_override_internal (bool global_init_p)
> >
> > if (!(rs6000_isa_flags_explicit & OPTION_MASK_BLOCK_OPS_VECTOR_PAIR))
> > {
> > - if (TARGET_MMA && TARGET_EFFICIENT_UNALIGNED_VSX)
> > + /* Do not generate lxvp and stxvp on power10 since there are some
> > + performance issues. */
> > + if (TARGET_MMA && TARGET_EFFICIENT_UNALIGNED_VSX
> > + && rs6000_tune != PROCESSOR_POWER10)
> > rs6000_isa_flags |= OPTION_MASK_BLOCK_OPS_VECTOR_PAIR;
> > else
> > rs6000_isa_flags &= ~OPTION_MASK_BLOCK_OPS_VECTOR_PAIR;
>
> The TARGET_MMA in that should not be there. Please fix that (that
> probably needs more changes).
All of the movoo and movxo support require TARGET_MMA as does the code in
rs6000-string.cc that could possibly generate load/store vector pair. To
remove the check here would mean also fixing all of the vector load and store
pairs in mma.md.
> This statement does the opposite of what the comment says.
>
> Please fix this. On trunk, first.
--
Michael Meissner, IBM
PO Box 98, Ayer, Massachusetts, USA, 01432
email: meiss...@linux.ibm.com
