https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114009
--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:95b6ee96348041eaee9133f082b57f3e57ef0b11 commit r14-9350-g95b6ee96348041eaee9133f082b57f3e57ef0b11 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Mar 7 08:43:16 2024 +0100 match.pd: Optimize a * !a to 0 [PR114009] The following patch attempts to fix an optimization regression through adding a simple simplification. We already have the /* (m1 CMP m2) * d -> (m1 CMP m2) ? d : 0 */ (if (!canonicalize_math_p ()) (for cmp (tcc_comparison) (simplify (mult:c (convert (cmp@0 @1 @2)) @3) (if (INTEGRAL_TYPE_P (type) && INTEGRAL_TYPE_P (TREE_TYPE (@0))) (cond @0 @3 { build_zero_cst (type); }))) optimization which otherwise triggers during the a * !a multiplication, but that is done only late and we aren't able through range assumptions optimize it yet anyway. The patch adds a specific simplification for it. If a is zero, then a * !a will be 0 * 1 (or for signed 1-bit 0 * -1) and so 0. If a is non-zero, then a * !a will be a * 0 and so again 0. THe pattern is valid for scalar integers, complex integers and vector types, but I think will actually trigger only for the scalar integers. For vector types I've added other two with VEC_COND_EXPR in it, for complex there are different GENERIC trees to match and it is something that likely would be never matched in GIMPLE, so I didn't handle that. 2024-03-07 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/114009 * genmatch.cc (decision_tree::gen): Emit ARG_UNUSED for captures argument even for GENERIC, not just for GIMPLE. * match.pd (a * !a -> 0): New simplifications. * gcc.dg/tree-ssa/pr114009.c: New test.
