[Bug tree-optimization/124405] cselim sometimes does not handle conditional store elimination

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124405

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pengxuan Zheng <pzheng@gcc.gnu.org>:

https://gcc.gnu.org/g:391ee229b737eb9a0cf3b705f41476f56d12d1e3

commit r17-1273-g391ee229b737eb9a0cf3b705f41476f56d12d1e3
Author: Pengxuan Zheng <pengxuan.zheng@oss.qualcomm.com>
Date:   Wed Apr 8 18:09:48 2026 -0700

    cselim: Allow middle_bb to have more than one statement [PR124405]

    Currently, cselim requires the middle_bb to have only a single statement.
This
    patch relaxes this restriction as long as all uses (except the rhs) in the
    single stmatement are also available where we insert to.

    Bootstrapped and tested on x86_64-linux-gnu and aarch64-linux-gnu.

    Changes since v1:
    * v2: Revert changes to trailing_store_in_bb and do not call
          trailing_store_in_bb to get split_assign.
          Remove some unnecessary checks in cselim_candidate.
          Pass the result of cselim_candidate which is the candidate store for
          cselim as an argument to cond_store_replacement instead.
    * v3: Simplify cselim_candidate by always calling trailing_store_in_bb and
          removing the legality checks.
          Generalize the cond_store_replacement legality checks to account for
the
          case when the middle_bb can have more than one statement.

            PR tree-optimization/124405

    gcc/ChangeLog:

            * tree-ssa-phiopt.cc (cond_store_replacement): Make ASSIGN (the
            candidate store for cselim) an argument of the function instead.
Update
            legality check due to relaxing the restriction that middle_bb can
have
            only a single statement.
            (cselim_candidate): New.
            (pass_cselim::execute): Call cselim_candidate and pass the result
to
            cond_store_replacement.

    gcc/testsuite/ChangeLog:

            * gcc.dg/tree-ssa/pr124405.c: New test.

    Signed-off-by: Pengxuan Zheng <pengxuan.zheng@oss.qualcomm.com>