[Bug target/113077] [14 Regression] ICE in dwarf2out_frame_debug_cfa_offset with `-O2 -fstack-protector-strong -fstack-clash-protection`

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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 <acoplan@gcc.gnu.org>:

https://gcc.gnu.org/g:5400778f69d19a94017561c7de02510d9c0899e6

commit r14-7132-g5400778f69d19a94017561c7de02510d9c0899e6
Author: Alex Coplan <alex.coplan@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.