From ad64e807ffca93e927b68f1aa0cea54dacbe9afd Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Mon, 4 Jan 2021 10:37:12 +0100 Subject: match.pd: Fold x == ~x to false [PR96782] x is never equal to ~x, so we can fold such comparisons to constants. 2021-01-04 Jakub Jelinek PR tree-optimization/96782 * match.pd (x == ~x -> false, x != ~x -> true): New simplifications. * gcc.dg/tree-ssa/pr96782.c: New test. --- gcc/match.pd | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'gcc/match.pd') diff --git a/gcc/match.pd b/gcc/match.pd index f5020d8..56fb583 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -4045,6 +4045,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (if (!flag_trapping_math) { constant_boolean_node (false, type); })) +/* x == ~x -> false */ +/* x != ~x -> true */ +(for cmp (eq ne) + (simplify + (cmp:c @0 (bit_not @0)) + { constant_boolean_node (cmp == NE_EXPR, type); })) + /* Fold ~X op ~Y as Y op X. */ (for cmp (simple_comparison) (simplify -- cgit v1.1