https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105218
--- Comment #5 from CVS 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:1774ab84863202f5db694914b67e3aef8c6dd807 commit r12-8090-g1774ab84863202f5db694914b67e3aef8c6dd807 Author: Jakub Jelinek <ja...@redhat.com> Date: Mon Apr 11 19:06:59 2022 +0200 phiopt: Fix up debug handling in the (x != cst1 ? x : cst2) != cst3 opt [PR105218] In the PR104639 optimization, I've added code to emit # DEBUG D#1 => arg != carg ? arg : oarg instruction and replace debug uses of the phi with that debug temp, so that the debug info is still accurrate. Unfortunately, that is only correct if the middle-bb and phi bb contain 1 and 2 predecessors, i.e. the ones that we are using in the optimization (in particular middle-bb has cond-bb as pred and phi bb cond-bb and middle-bb). If that is not the case, then we can reach these from another bb and so the arg SSA_NAME might not be valid there (its definition doesn't dominate all incoming edges), or, even if it is valid, might be wrong-debug, e.g. phi argument from some unrelated other incoming edge might have the carg value that the debug stmt remaps to oarg. In theory we could check for that case and if middle-bb doesn't have a single pred or phi bb 2 preds check if arg SSA_NAME dominates the phi bb and if all other phi arguments are expr_not_equal_to the carg value, but this patch just uses a simpler approach and resets already if we have some extra incoming edges. 2022-04-11 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/105218 * tree-ssa-phiopt.cc (value_replacement): If middle_bb has more than one predecessor or phi's bb more than 2 predecessors, reset phi result uses instead of adding a debug temp. * gcc.dg/pr105218.c: New test.
