Re: [PATCH PR96357][GCC][AArch64]: could not split insn UNSPEC_COND_FSUB with AArch64 SVE

[Richard Sandiford <richard.sandiford@arm.com>]

Przemyslaw Wirkus <Przemyslaw.Wirkus@arm.com> writes:
> Hi,
>
> Problem is related to that operand 4 (In original pattern
> *cond_sub<mode>_any_const) is no longer the same as operand 1, and so
> the pattern doesn't match the split condition.
>
> Pattern *cond_sub<mode>_any_const is being split by this patch into two
> separate patterns:
> * Pattern *cond_sub<mode>_relaxed_const now matches const_int
>   SVE_RELAXED_GP operand.
> * Pattern *cond_sub<mode>_strict_const now matches const_int
>   SVE_STRICT_GP operand.
> * Remove aarch64_sve_pred_dominates_p condition from both patterns.

Thanks for doing this.

> @@ -5271,6 +5270,43 @@ (define_insn_and_rewrite "*cond_sub<mode>_any_const"
>    [(set_attr "movprfx" "yes")]
>  )
>  
> +;; Predicated floating-point subtraction from a constant, merging with an
> +;; independent value.

The previous pattern had the same comment.  Maybe add:

  The subtraction predicate and the merge predicate are allowed to be
  different.

to the relaxed one and:

  The subtraction predicate and the merge predicate must be the same.

to this one.

> +(define_insn_and_rewrite "*cond_sub<mode>_strict_const"
> +  [(set (match_operand:SVE_FULL_F 0 "register_operand" "=w, w, ?w")
> +	(unspec:SVE_FULL_F
> +	  [(match_operand:<VPRED> 1 "register_operand" "Upl, Upl, Upl")
> +	   (unspec:SVE_FULL_F
> +	     [(match_dup 1)
> +	      (const_int SVE_STRICT_GP)
> +	      (match_operand:SVE_FULL_F 2 "aarch64_sve_float_arith_immediate")
> +	      (match_operand:SVE_FULL_F 3 "register_operand" "w, w, w")]
> +	     UNSPEC_COND_FSUB)
> +	   (match_operand:SVE_FULL_F 4 "aarch64_simd_reg_or_zero" "Dz, 0, w")]
> +	  UNSPEC_SEL))]
> +  "TARGET_SVE
> +   && !rtx_equal_p (operands[3], operands[4])"

Very minor, but the file generally puts conditions on a single line
if they'll fit.  Same for the relaxed version.

> +  "@
> +   movprfx\t%0.<Vetype>, %1/z, %3.<Vetype>\;fsubr\t%0.<Vetype>, %1/m, %0.<Vetype>, #%2
> +   movprfx\t%0.<Vetype>, %1/m, %3.<Vetype>\;fsubr\t%0.<Vetype>, %1/m, %0.<Vetype>, #%2
> +   #"
> +  "&& 1"
> +  {
> +    if (reload_completed
> +        && register_operand (operands[4], <MODE>mode)
> +        && !rtx_equal_p (operands[0], operands[4]))
> +      {
> +	emit_insn (gen_vcond_mask_<mode><vpred> (operands[0], operands[3],
> +						 operands[4], operands[1]));
> +	operands[4] = operands[3] = operands[0];
> +      }
> +    else if (!rtx_equal_p (operands[1], operands[5]))
> +      operands[5] = copy_rtx (operands[1]);

The last two lines are a hold-over from the relaxed version, where there
were two predicates.  There's no operand 5 in this pattern, so we should
just delete the lines.

Thanks,
Richard