https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123038
--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Biener <[email protected]>: https://gcc.gnu.org/g:5584b489341924d042988ad27a2dc25fa8fda62a commit r16-5957-g5584b489341924d042988ad27a2dc25fa8fda62a Author: Richard Biener <[email protected]> Date: Sun Dec 7 11:30:48 2025 +0100 tree-optimization/123038 - FFS/CTZ pattern incompatible with reductions The pattern ends up using the argument more than one time which isn't supported. When FFS directly maps to CTZ + 1 it works though. PR tree-optimization/123038 * tree-vect-patterns.cc (vect_recog_ctz_ffs_pattern): Reject pattern for reductions when the call argument is used multiple times. * gcc.dg/vect/pr123038.c: New testcase.
