Re: [PATCH] middle-end/114189 - drop uses of vcond{,u,eq}_optab

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

Richard Biener <rguenther@suse.de> writes:
> The following retires vcond{,u,eq} optabs by stopping to use them
> from the middle-end.  Targets instead (should) implement vcond_mask
> and vec_cmp{,u,eq} optabs.  The PR this change refers to lists
> possibly affected targets - those implementing these patterns,
> and in particular it lists mips, sparc and ia64 as targets that
> most definitely will regress while others might simply remove
> their vcond{,u,eq} patterns.
>
> I'd appreciate testing, I do not expect fallout for x86 or arm/aarch64.
> I know riscv doesn't implement any of the legacy optabs.  But less
> maintained vector targets might need adjustments.
>
> I want to get rid of those optabs for GCC 15.  If I don't hear from
> you I will assume your target is fine.

Great!  Thanks for doing this.

Is there a plan for how we should handle vector comparisons that
have to be done as the inverse of the negated condition?  Should
targets simply not provide vec_cmp for such conditions and leave
the target-independent code to deal with the fallout?  (For a
standalone comparison, it would invert the result.  For a VEC_COND_EXPR
it would swap the true and false values.)

Richard

>
> Thanks,
> Richard.
>
> 	PR middle-end/114189
> 	* optabs-query.h (get_vcond_icode): Always return CODE_FOR_nothing.
> 	(get_vcond_eq_icode): Likewise.
> ---
>  gcc/optabs-query.h | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/gcc/optabs-query.h b/gcc/optabs-query.h
> index 0cb2c21ba85..31fbce80175 100644
> --- a/gcc/optabs-query.h
> +++ b/gcc/optabs-query.h
> @@ -112,14 +112,9 @@ get_vec_cmp_eq_icode (machine_mode vmode, machine_mode mask_mode)
>     mode CMODE, unsigned if UNS is true, resulting in a value of mode VMODE.  */
>  
>  inline enum insn_code
> -get_vcond_icode (machine_mode vmode, machine_mode cmode, bool uns)
> +get_vcond_icode (machine_mode, machine_mode, bool)
>  {
> -  enum insn_code icode = CODE_FOR_nothing;
> -  if (uns)
> -    icode = convert_optab_handler (vcondu_optab, vmode, cmode);
> -  else
> -    icode = convert_optab_handler (vcond_optab, vmode, cmode);
> -  return icode;
> +  return CODE_FOR_nothing;
>  }
>  
>  /* Return insn code for a conditional operator with a mask mode
> @@ -135,9 +130,9 @@ get_vcond_mask_icode (machine_mode vmode, machine_mode mmode)
>     mode CMODE (only EQ/NE), resulting in a value of mode VMODE.  */
>  
>  inline enum insn_code
> -get_vcond_eq_icode (machine_mode vmode, machine_mode cmode)
> +get_vcond_eq_icode (machine_mode, machine_mode)
>  {
> -  return convert_optab_handler (vcondeq_optab, vmode, cmode);
> +  return CODE_FOR_nothing;
>  }
>  
>  /* Enumerates the possible extraction_insn operations.  */