Hi!
On Sun, Nov 01, 2020 at 06:32:02PM -0500, Vladimir Makarov wrote:
> On 2020-10-30 7:36 p.m., Segher Boessenkool wrote:
> >Thanks for the patch! But it has a problem:
> >
> >>diff --git a/gcc/config/rs6000/vsx.md b/gcc/config/rs6000/vsx.md
> >>index 67e4f2fd037..78de85ccbbb 100644
> >>--- a/gcc/config/rs6000/vsx.md
> >>+++ b/gcc/config/rs6000/vsx.md
> >>@@ -3717,7 +3717,7 @@
> >> (vec_select:<VS_scalar>
> >> (match_operand:VSX_EXTRACT_I 1 "gpc_reg_operand" "<VSX_EX>,v")
> >> (parallel [(match_operand:QI 2 "const_int_operand" "n,n")])))
> >>- (clobber (match_scratch:<VS_scalar> 3 "=<VSX_EX>,&r"))
> >>+ (clobber (match_scratch:<VS_scalar> 3 "=*<VSX_EX>,&*r"))
> >> (clobber (match_scratch:SI 4 "=X,&r"))]
> >> "VECTOR_MEM_VSX_P (<MODE>mode) && TARGET_VEXTRACTUB"
> >> "#"
> >You add * to both alternatives here? I would expect adding it to only
> >the second alternative, does it work better with both?
> No. It works the same. When the both alternatives use the hint, the
> scratch pseudo got the class ALL_REGS. When only the 2nd use the hint,
> the class is VSX_REGS. As I understand now the preferable alternative
> is the 1st one (with <VSX> for the scratch). In this case using the
> hint only for the 2nd alternative has more sense.
> >That also avoids a different problem: *<VSX_EX> won't work as expected.
> >'*' in IRA skips one constraint character, but <VSX_EX> can be "wa", a
> >two-letter constraint (and we do have an "a" constraint as well,
> >something wholly different: "wa" means a VSX register, while "a" is an
> >indexed address).
> >
> > case '*':
> > /* Ignore the next letter for this pass. */
> > c = *++p;
> > break;
> >
> >
> I see. Thanks for pointing this out. Definitely it is better to use the
> hint only for the second alternative ("&*r") then. Is this solution ok
> for you?
Yes, certainly. And thanks!
(Should "*" be changed so that it skips a whole constraint if it can,
instead of only a single char always?)
Segher
