On Sat, Jun 27, 2026 at 5:25 AM Kael Andrew Franco
<[email protected]> wrote:
>
> From 2ad702b7838e5f8962e8c3a917d6834f089ac097 Mon Sep 17 00:00:00 2001
> From: Kael Andrew Alonzo Franco <[email protected]>
> Date: Fri, 26 Jun 2026 15:17:50 -0400
> Subject: [PATCH] match: Use tree_expr_nonnegative_p instead of TYPE_UNSIGNED
> for MAX (A, B) (==,!=) 0 -> (A|B) (==,!=) 0 [PR125749]
>
> tree_expr_nonnegative_p covers non negative signed type variables, unlike
> TYPE_UNSIGNED.
>
> Bootstrapped and tested on x86_64-pc-linux-gnu
>
> PR tree-optimization/125749
>
> gcc/ChangeLog:
>
> PR tree-optimization/125749
> * match.pd: Use tree_expr_nonnegative_p for MAX (A, B) (==,!=) 0 -> (A|B)
> (==,!=) 0.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/125749
> * gcc.dg/pr125749.c: New test.
>
> Signed-off-by: Kael Franco <[email protected]>
> ---
> gcc/match.pd | 14 +++++++-------
> gcc/testsuite/gcc.dg/pr125749.c | 20 ++++++++++++++++++++
> 2 files changed, 27 insertions(+), 7 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/pr125749.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 615ce9b1963..b5587326c88 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -4738,15 +4738,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (cmp (minmax @0 INTEGER_CST@1) INTEGER_CST@2)
> (comb (cmp @0 @2) (cmp @1 @2))))
>
> -/* MAX (A, B) == 0 -> (A|B) == 0 iff unsigned.
> - MAX (A, B) != 0 -> (A|B) != 0 iff unsigned. */
> +/* If A >= 0 and B >= 0:
> + MAX (A, B) == 0 -> (A|B) == 0.
> + MAX (A, B) != 0 -> (A|B) != 0. */
Add "for non-negative" instead of just removing `iff unsigned`.
Otherwise, looks good.
Thanks,
Andrea
> (for cmp (eq ne)
> (simplify
> - (cmp (max @0 @1) integer_zerop)
> - (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
> - (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
> - (cmp (bit_ior (convert:utype @0) (convert:utype @1))
> - { build_zero_cst (utype); } )))))
> + (cmp (max tree_expr_nonnegative_p@0 tree_expr_nonnegative_p@1)
> integer_zerop)
> + (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
> + (cmp (bit_ior (convert:utype @0) (convert:utype @1))
> + { build_zero_cst (utype); } ))))
>
> /* Undo fancy ways of writing max/min or other ?: expressions, like
> a - ((a - b) & -(a < b)) and a - (a - b) * (a < b) into (a < b) ? b : a.
> diff --git a/gcc/testsuite/gcc.dg/pr125749.c b/gcc/testsuite/gcc.dg/pr125749.c
> new file mode 100644
> index 00000000000..cf0fc1e8675
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr125749.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +_Bool
> +max_eq_zero (unsigned short a, unsigned short b) {
> + int aa = a;
> + int bb = b;
> + int t = aa > bb ? aa : bb;
> + return (t == 0) == ((a | b) == 0);
> +}
> +
> +_Bool
> +max_ne_zero (unsigned short a, unsigned short b) {
> + int aa = a;
> + int bb = b;
> + int t = aa > bb ? aa : bb;
> + return (t != 0) == ((a | b) != 0);
> +}
> +
> +/* { dg-final { scan-tree-dump-times "return 1;" 2 "optimized" } } */
> --
> 2.54.0
>
>
