On Fri, Jun 16, 2023 at 4:46 AM Richard Biener via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> The following adds two patterns simplifying comparisons,
> uns < (typeof uns)(uns != 0) is always false and x != (typeof x)(x == 0)
> is always true.
A few more that should be done (I will file a bug in a few minutes):
`x == (typeof x)(x == 0)` is always false.
`x == (typeof x)(x != 0)` is `(unsigned_type)x <= 1`
`x != (typeof x)(x != 0)` is `(unsigned_type)x > 1`
`uns <= (typeof uns)(uns != 0)` -> `uns <= 1`
`uns > (typeof uns)(uns != 0)` is `uns > 1`
`uns >= (typeof uns)(uns != 0)` is always true
That should be all of them I think and I think I did it correctly.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
>
> PR tree-optimization/110278
> * match.pd (uns < (typeof uns)(uns != 0) -> false): New.
> (x != (typeof x)(x == 0) -> true): Likewise.
> ---
> gcc/match.pd | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 264f9cb8a40..48b76e6a051 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -6410,6 +6410,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (if (cmp == GT_EXPR)
> (lt (view_convert:st @0) { build_zero_cst (st); })))))))))))
>
> +/* unsigned < (typeof unsigned)(unsigned != 0) is always false. */
> +(simplify
> + (lt:c @0 (convert (ne @0 integer_zerop)))
> + (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
> + { constant_boolean_node (false, type); }))
> +
> +/* x != (typeof x)(x == 0) is always true. */
> +(simplify
> + (ne:c @0 (convert (eq @0 integer_zerop)))
> + { constant_boolean_node (true, type); })
> +
> (for cmp (unordered ordered unlt unle ungt unge uneq ltgt)
> /* If the second operand is NaN, the result is constant. */
> (simplify
> --
> 2.35.3
