[Bug tree-optimization/122083] [15/16 Regression] Bogus -Wnonnull for call to memcmp with length determined using <=> operator

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122083

--- Comment #14 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Andrew Pinski <pinskia@gcc.gnu.org>:

https://gcc.gnu.org/g:decd4277e97114922ce60786a4587a31545dba94

commit r16-4260-gdecd4277e97114922ce60786a4587a31545dba94
Author: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
Date:   Fri Oct 3 20:18:07 2025 -0700

    phiopt/cselim: Improve cselim-limited to commonalize all stores [PR122083]

    cselim (and the phiopt's cselim-limited) can commonalize a single
    store which makes this too limited in some/many cases. Instead let's
    commonalize all trailing stores as much as possible (only in the same
    order).
    The change is smallish, basically the restriction on being the only store
    is removed from single_trailing_store_in_bb (renamed too). And also
    looping to remove all of the trailing stores instead of just doing one for
    the pass.

    Note sink will do the same optimization so doing it earlier seems like a
good
    idea because it improve change inlining size estimates.
    For an example with this change, early inlining can happen for min_cmp<long
int>
    in g++.dg/opt/pr122083-1.C now; that avoids a -Wnonnull warning as the
memcmp with
    the null argument is optimized early. It can also catch some min in phiopt1
in some
    cases.

    Bootstrapped and tested on x86_64-linux-gnu.

    Changes since v1:
    * v2: For !flag_expensive_optimizations, handle the only store rather than
just the last
          store.

            PR tree-optimization/122083

    gcc/ChangeLog:

            * tree-ssa-phiopt.cc (single_trailing_store_in_bb): Rename to ...
            (trailing_store_in_bb): This and take new argument to check for
            only store.
            (cond_if_else_store_replacement_limited): Update to use
            trailing_store_in_bb.
            (cond_if_else_store_replacement): Loop until
            cond_if_else_store_replacement_limited returns false.
            (pass_phiopt::execute): Instead of calling
cond_if_else_store_replacement_limited
            once, also loop on it.

    gcc/testsuite/ChangeLog:

            * gcc.dg/tree-ssa/ssa-pre-19.c: Disable phiopt and cselim.
            * g++.dg/opt/pr122083-1.C: New test.
            * gcc.dg/tree-ssa/cselim-1.c: New test.
            * gcc.dg/tree-ssa/cselim-2.c: New test.

    Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>