https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118521
--- Comment #11 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Biener <rgue...@gcc.gnu.org>: https://gcc.gnu.org/g:a2755339c6c9832467c573d956e91565943ecdc1 commit r15-7652-ga2755339c6c9832467c573d956e91565943ecdc1 Author: Richard Biener <rguent...@suse.de> Date: Thu Feb 20 13:37:05 2025 +0100 tree-optimization/118521 - bogus diagnostic from unreachable code When SCCP does final value replacement we end up with unfolded IL like __result_274 = _150 + 1; ... __new_finish_106 = __result_274 + 3; <-- from SCCP _115 = _150 + 4; if (__new_finish_106 != _115) this does only get rectified by the next full folding which happens in forwprop4 which is after the strlen pass emitting the unwanted diagnostic. The following mitigates this case in a similar way as r15-7472 did for PR118817 - by ensuring we have the IL folded. This is done by simply folding all immediate uses of the former PHI def that SCCP replaces. All other more general approaches have too much fallout at this point. PR tree-optimization/118521 * tree-scalar-evolution.cc (final_value_replacement_loop): Fold uses of the replaced PHI def. * g++.dg/torture/pr118521.C: New testcase.
