https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118914
--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Andrew Pinski <pins...@gcc.gnu.org>: https://gcc.gnu.org/g:e8a5f747cfa9c79ab7d95ff95d17d3e31afede50 commit r15-8478-ge8a5f747cfa9c79ab7d95ff95d17d3e31afede50 Author: Andrew Pinski <quic_apin...@quicinc.com> Date: Wed Feb 19 16:10:31 2025 -0800 combine: Add REG_DEAD notes to the last instruction after a split [PR118914] So gcc.target/aarch64/rev16_2.c started to fail after r15-268-g9dbff9c05520a7, the problem is combine now rejects the instruction combine. This happens because after a different combine which uses a define_split and that define_split creates a new pseudo register. That new pseudo register is dead after the last instruction in the stream BUT combine never creates a REG_DEAD for it. So combine thinks it is still needed after and now with the i2 not changing, combine rejects the combine. Now combine should be creating a REG_DEAD for the new pseudo registers for the last instruction of the split. This fixes rev16_2.c and also improves the situtation in other cases by removing other dead instructions. Bootstrapped and tested on aarch64-linux-gnu and x86_64-linux-gnu. gcc/ChangeLog: PR rtl-optimization/118914 * combine.cc (recog_for_combine): Add old_nregs and new_nregs argument (defaulting to 0). Update call to recog_for_combine_1. (combine_split_insns): Add old_nregs and new_nregs arguments, store the old and new max registers to them. (try_combine): Update calls to combine_split_insns and pass old_nregs and new_nregs for the i3 call to recog_for_combine. (find_split_point): Update call to combine_split_insns; ignoring the values there. (recog_for_combine_1): Add old_nregs and new_nregs arguments, if the insn was recognized (and not to no-op move), add the REG_DEAD notes to pnotes argument. Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
