Re: [PATCH] MATCH: Port CLRSB part of builtin_zero_pattern

[Richard Biener <richard.guenther@gmail.com>]

On Sun, Apr 30, 2023 at 11:13 PM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This ports the clrsb builtin part of builtin_zero_pattern
> to match.pd. A simple pattern to port.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>
> gcc/ChangeLog:
>
>         * match.pd (a != 0 ? CLRSB(a) : CST -> CLRSB(a)): New
>         pattern.
> ---
>  gcc/match.pd | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 0e782cde71d..bf918ba70ce 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -7787,6 +7787,14 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>    (cond (ne @0 integer_zerop@1) (func@4 (convert? @2)) integer_zerop@3)
>    @4))
>
> +/* a != 0 ? FUN(a) : CST -> Fun(a) for some CLRSB builtins
> +   where CST is precision-1. */
> +(for func (CLRSB)
> + (simplify
> +  (cond (ne @0 integer_zerop@1) (func@5 (convert?@4 @2)) INTEGER_CST@3)

As you don't seem to use @2 why not match (func@5 @4) only?

Otherwise LGTM.

> +  (if (wi::to_widest (@3) == TYPE_PRECISION (TREE_TYPE (@4)) - 1)
> +   @5)))
> +
>  #if GIMPLE
>  /* a != 0 ? CLZ(a) : CST -> .CLZ(a) where CST is the result of the internal function for 0. */
>  (for func (CLZ)
> --
> 2.31.1
>