https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113077
--- Comment #13 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:5400778f69d19a94017561c7de02510d9c0899e6 commit r14-7132-g5400778f69d19a94017561c7de02510d9c0899e6 Author: Alex Coplan <alex.cop...@arm.com> Date: Thu Jan 11 10:16:24 2024 +0000 aarch64: Fix dwarf2cfi ICEs due to recent CFI note changes [PR113077] In r14-6604-gd7ee988c491cde43d04fe25f2b3dbad9d85ded45 we changed the CFI notes attached to callee saves (in aarch64_save_callee_saves). That patch changed the ldp/stp representation to use unspecs instead of PARALLEL moves. This meant that we needed to attach CFI notes to all frame-related pair saves such that dwarf2cfi could still emit the appropriate CFI (it cannot interpret the unspecs directly). The patch also attached REG_CFA_OFFSET notes to individual saves so that the ldp/stp pass could easily preserve them when forming stps. In that change I chose to use REG_CFA_OFFSET, but as the PR shows, that choice was problematic in that REG_CFA_OFFSET requires the attached store to be expressed in terms of the current CFA register at all times. This means that even scheduling of frame-related insns can break this invariant, leading to ICEs in dwarf2cfi. The old behaviour (before that change) allowed dwarf2cfi to interpret the RTL directly for sp-relative saves. This change restores that behaviour by using REG_FRAME_RELATED_EXPR instead of REG_CFA_OFFSET. REG_FRAME_RELATED_EXPR effectively just gives a different pattern for dwarf2cfi to look at instead of the main insn pattern. That allows us to attach the old-style PARALLEL move representation in a REG_FRAME_RELATED_EXPR note and means we are free to always express the save addresses in terms of the stack pointer. Since the ldp/stp fusion pass can combine frame-related stores, this patch also updates it to preserve REG_FRAME_RELATED_EXPR notes, and additionally gives it the ability to synthesize those notes when combining sp-relative saves into an stp (the latter always needs a note due to the unspec representation, the former does not). gcc/ChangeLog: PR target/113077 * config/aarch64/aarch64-ldp-fusion.cc (filter_notes): Add fr_expr param to extract REG_FRAME_RELATED_EXPR notes. (combine_reg_notes): Handle REG_FRAME_RELATED_EXPR notes, and synthesize these if needed. Update caller ... (ldp_bb_info::fuse_pair): ... here. (ldp_bb_info::try_fuse_pair): Punt if either insn has writeback and either insn is frame-related. (find_trailing_add): Punt on frame-related insns. * config/aarch64/aarch64.cc (aarch64_save_callee_saves): Use REG_FRAME_RELATED_EXPR instead of REG_CFA_OFFSET. gcc/testsuite/ChangeLog: PR target/113077 * gcc.target/aarch64/pr113077.c: New test.
