https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114674
--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Alex Coplan <acop...@gcc.gnu.org>: https://gcc.gnu.org/g:74690ff96b263b8609639b7fbc5d6afd3f19cb98 commit r15-282-g74690ff96b263b8609639b7fbc5d6afd3f19cb98 Author: Alex Coplan <alex.cop...@arm.com> Date: Wed Apr 10 16:30:36 2024 +0100 aarch64: Preserve mem info on change of base for ldp/stp [PR114674] The ldp/stp fusion pass can change the base of an access so that the two accesses end up using a common base register. So far we have been using adjust_address_nv to do this, but this means that we don't preserve other properties of the mem we're replacing. It seems better to use replace_equiv_address_nv, as this will preserve e.g. the MEM_ALIGN of the mem whose address we're changing. The PR shows that by adjusting the other mem we lose alignment information about the original access and therefore end up rejecting an otherwise viable pair when --param=aarch64-stp-policy=aligned is passed. This patch fixes that by using replace_equiv_address_nv instead. Notably this is the same approach as taken by aarch64_check_consecutive_mems when a change of base is required, so this at least makes things more consistent between the ldp fusion pass and the peepholes. gcc/ChangeLog: PR target/114674 * config/aarch64/aarch64-ldp-fusion.cc (ldp_bb_info::fuse_pair): Use replace_equiv_address_nv on a change of base instead of adjust_address_nv on the other access. gcc/testsuite/ChangeLog: PR target/114674 * gcc.target/aarch64/pr114674.c: New test.
