https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116343
--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Richard Sandiford <rsand...@gcc.gnu.org>: https://gcc.gnu.org/g:70ae0daeb76f28a3135f4a74d6e440fb1d9821fa commit r15-2936-g70ae0daeb76f28a3135f4a74d6e440fb1d9821fa Author: Richard Sandiford <richard.sandif...@arm.com> Date: Thu Aug 15 16:54:02 2024 +0100 late-combine: Preserve INSN_CODE when modifying notes [PR116343] When it removes a definition, late-combine tries to update all uses in notes. It does this using the same insn_propagation class that it uses for patterns. However, insn_propagation uses validate_change, which in turn resets the INSN_CODE. This is inefficient in the best case, since it forces the pattern to be rerecognised even though changing a note can't affect the INSN_CODE. But in the PR it's a correctness problem: resetting INSN_CODE means we lose the NOOP_INSN_MOVE_CODE, which in turn means that rtl-ssa doesn't queue it for deletion. This patch adds a routine specifically for propagating into notes. A belt-and-braces fix would be to rerecognise noop moves in function_info::change_insns, but I can't think of a good reason why that would be necessary, and it could paper over latent bugs. gcc/ PR testsuite/116343 * recog.h (insn_propagation::apply_to_note): Declare. * recog.cc (insn_propagation::apply_to_note): New function. * late-combine.cc (insn_combination::substitute_note): Use apply_to_note instead of apply_to_rvalue. * rtl-ssa/changes.cc (rtl_ssa::changes_are_worthwhile): Improve dumping of costs for noop moves. gcc/testsuite/ PR testsuite/116343 * gcc.dg/torture/pr116343.c: New test.
