Hi!
On Fri, Jun 30, 2023 at 02:26:35PM -0500, Pat Haugen wrote:
> gcc/
> * config/rs6000/rs6000.cc (rs6000_rtx_costs): Check if disabling
> scalar modulo.
"Check whether the modulo instruction is disabled?"
> * config/rs6000/rs6000.md (mod<mode>3, *mod<mode>3): Disable.
> (define_expand umod<mode>3): New.
> (define_insn umod<mode>3): Rename to *umod<mode>3 and disable.
> (umodti3, modti3): Disable.
None of these patterns are disabled! Instead, the new TARGET_* thing
is used.
> +/* Disable generation of scalar modulo instructions due to performance issues
> + with certain input values. This can be removed in the future when the
> + issues have been resolved. */
> +#define RS6000_DISABLE_SCALAR_MODULO 1
I think that is a bit optimistic -- in the future we will still want to
support older cores ;-)
> - "TARGET_POWER10 && TARGET_POWERPC64"
> + "TARGET_POWER10 && TARGET_POWERPC64 && !RS6000_DISABLE_SCALAR_MODULO"
> "vmoduq %0,%1,%2"
Did we ever test if this insn in fact is slower as well? I don't mean
either way, orthogonality is good, but just for my enlightenment.
> +++ b/gcc/testsuite/gcc.target/powerpc/clone1.c
> +/* { Fail due to RS6000_DISABLE_SCALAR_MODULO. */
Xfail, but heh. No need to change that.
> +/* { dg-final { scan-assembler-times {\mdivd\M} 1 { xfail *-*-* } } } */
> +/* { Fail due to RS6000_DISABLE_SCALAR_MODULO. */
> +/* { dg-final { scan-assembler-times {\mmodsw\M} 1 { xfail *-*-* } } } */
Thanks for the \m \M, it is much harder to determine if the tests
actually work, without that :-)
With improved changelog: okay for trunk. Okay for all backports as
well (after some soak time).
Thank you!
Segher
