On Thu, May 20, 2021 at 02:27:06PM -0500, will schmidt wrote:
> > diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
> > index fdaf12aeda0..ef1ebaaee05 100644
> > --- a/gcc/config/rs6000/rs6000.c
> > +++ b/gcc/config/rs6000/rs6000.c
> > @@ -15706,8 +15706,8 @@ rs6000_emit_vector_cond_expr (rtx dest, rtx
> > op_true, rtx op_false,
> > return 1;
> > }
> >
> > -/* Possibly emit the xsmaxcdp and xsmincdp instructions to emit a maximum
> > or
> > - minimum with "C" semantics.
> > +/* Possibly emit the xsmaxc{dp,qp} and xsminc{dp,qp} instructions to emit a
> > + maximum or minimum with "C" semantics.
> >
> > Unless you use -ffast-math, you can't use these instructions to replace
> > conditions that implicitly reverse the condition because the comparison
> > @@ -15783,6 +15783,7 @@ rs6000_maybe_emit_fp_cmove (rtx dest, rtx op, rtx
> > true_cond, rtx false_cond)
> > enum rtx_code code = GET_CODE (op);
> > rtx op0 = XEXP (op, 0);
> > rtx op1 = XEXP (op, 1);
> > + machine_mode compare_mode = GET_MODE (op0);
> > machine_mode result_mode = GET_MODE (dest);
> > rtx compare_rtx;
> > rtx cmove_rtx;
> > @@ -15791,6 +15792,35 @@ rs6000_maybe_emit_fp_cmove (rtx dest, rtx op, rtx
> > true_cond, rtx false_cond)
> > if (!can_create_pseudo_p ())
> > return 0;
> >
> > + /* We allow the comparison to be either SFmode/DFmode and the true/false
> > + condition to be either SFmode/DFmode. I.e. we allow:
> > +
> > + float a, b;
> > + double c, d, r;
> > +
> > + r = (a == b) ? c : d;
> > +
> > + and:
> > +
> > + double a, b;
> > + float c, d, r;
> > +
> > + r = (a == b) ? c : d;
>
>
> This new comment does not seem to align with the comments in the
> description, which statee "But you can't do ..."
Yes, the comment is perhaps a little unclear.
> > +
> > + but we don't allow intermixing the IEEE 128-bit floating point types
> > with
> > + the 32/64-bit scalar types.
> > +
> > + It gets too messy where SFmode/DFmode can use any register and
> > TFmode/KFmode
> > + can only use Altivec registers. In addtion, we would need to do a
> > XXPERMDI
> > + if we compare SFmode/DFmode and move TFmode/KFmode. */
> > +
> > + if (compare_mode == result_mode
> > + || (compare_mode == SFmode && result_mode == DFmode)
> > + || (compare_mode == DFmode && result_mode == SFmode))
> > + ;
> > + else
> > + return false;
>
> Interesting if/else block. May want to reverse the logic. I defer if
> this way is notably simpler than inverting it.
I originally tried inverting it, and it just got messy.
> > +++ b/gcc/testsuite/gcc.target/powerpc/float128-minmax-3.c
> > @@ -0,0 +1,15 @@
> > +/* { dg-require-effective-target ppc_float128_hw } */
> > +/* { dg-require-effective-target power10_ok } */
> > +/* { dg-options "-mdejagnu-cpu=power10 -O2" } */
> > +
> > +#ifndef TYPE
> > +#define TYPE _Float128
> > +#endif
> > +
> > +/* Test that the fminf128/fmaxf128 functions generate if/then/else and not
> > a
> > + call. */
>
> s/"if/then/else"/"minmax"/ ?
Thanks.
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: [email protected], phone: +1 (978) 899-4797
