https://gcc.gnu.org/g:86a6d4ff7844e54cb8e685b6ea0782ceca618888
commit r17-1572-g86a6d4ff7844e54cb8e685b6ea0782ceca618888 Author: Kael Andrew Franco <[email protected]> Date: Mon Jun 15 11:13:18 2026 -0600 [PATCH] match: For nonnegative X, relax condition on X < (typeof X)(X != 0) to false [PR125756] From 0d094722ecdb86aa8373134a36392c60e6bb2b69 Mon Sep 17 00:00:00 2001 From: Kael Andrew Alonzo Franco <[email protected]> Date: Sat, 13 Jun 2026 08:56:34 -0400 Subject: [PATCH] match: For nonnegative X, relax condition on X < (typeof X)(X != 0) to false [PR125756] tree_expr_nonnegative_p covers both TYPE_UNSIGNED (type) or when X is known to be nonnegative. Bootstrapped and tested on x86_64-pc-linux-gnu PR tree-optimization/125756 gcc/ChangeLog: * match.pd: Use tree_expr_nonnegative_p for X < (typeof X)(X != 0) to false. gcc/testsuite/ChangeLog: * gcc.dg/pr125756.c: New test. Diff: --- gcc/match.pd | 7 +++---- gcc/testsuite/gcc.dg/pr125756.c | 21 +++++++++++++++++++++ 2 files changed, 24 insertions(+), 4 deletions(-) diff --git a/gcc/match.pd b/gcc/match.pd index d0d37116ddf1..f2503b35dca0 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -8272,11 +8272,10 @@ 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. */ +/* For nonnegative x, x < (typeof x)(x != 0) is always false. */ (simplify - (lt:c @0 (convert (ne @0 integer_zerop))) - (if (TYPE_UNSIGNED (TREE_TYPE (@0))) - { constant_boolean_node (false, type); })) + (lt:c @0 (convert (ne tree_expr_nonnegative_p@0 integer_zerop))) + { constant_boolean_node (false, type); }) /* x != (typeof x)(x == CST) -> CST == 0 ? 1 : (CST == 1 ? (x!=0&&x!=1) : x != 0) */ /* x != (typeof x)(x != CST) -> CST == 1 ? 1 : (CST == 0 ? (x!=0&&x!=1) : x != 1) */ diff --git a/gcc/testsuite/gcc.dg/pr125756.c b/gcc/testsuite/gcc.dg/pr125756.c new file mode 100644 index 000000000000..3be98d901aaf --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr125756.c @@ -0,0 +1,21 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + +bool +f1 (unsigned short aa) +{ + int a = aa; + bool t = a != 0; + int tu = t; + return a < tu; +} + +bool +f2 (unsigned short a) +{ + bool t = a != 0; + unsigned short tu = t; + return a < tu; +} + +/* { dg-final { scan-tree-dump-times "return 0;" 2 "optimized" } } */
