[Bug target/114936] [14 Regression] Typo in aarch64-ldp-fusion.cc:combine_reg_notes

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114936

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-14 branch has been updated by Alex Coplan
<acoplan@gcc.gnu.org>:

https://gcc.gnu.org/g:8eb469546f7f32dcec5d3376dfb419c1d4f21e4a

commit r14-10369-g8eb469546f7f32dcec5d3376dfb419c1d4f21e4a
Author: Alex Coplan <alex.coplan@arm.com>
Date:   Fri May 3 14:12:32 2024 +0000

    aarch64: Fix typo in aarch64-ldp-fusion.cc:combine_reg_notes [PR114936]

    This fixes a typo in combine_reg_notes in the load/store pair fusion
    pass.  As it stands, the calls to filter_notes store any
    REG_FRAME_RELATED_EXPR to fr_expr with the following association:

     - i2 -> fr_expr[0]
     - i1 -> fr_expr[1]

    but then the checks inside the following if statement expect the
    opposite (more natural) association, i.e.:

     - i2 -> fr_expr[1]
     - i1 -> fr_expr[0]

    this patch fixes the oversight by swapping the fr_expr indices in the
    calls to filter_notes.

    In hindsight it would probably have been less confusing / error-prone to
    have combine_reg_notes take an array of two insns, then we wouldn't have
    to mix 1-based and 0-based indexing as well as remembering to call
    filter_notes in reverse program order.  This however is a minimal fix
    for backporting purposes.

    gcc/ChangeLog:

            PR target/114936
            * config/aarch64/aarch64-ldp-fusion.cc (combine_reg_notes):
            Ensure insn iN has its REG_FRAME_RELATED_EXPR (if any) stored in
            FR_EXPR[N-1], thus matching the correspondence expected by the
            copy_rtx calls.

    (cherry picked from commit 73c8e24b692e691c665d0f1f5424432837bd8c06)