[Bug tree-optimization/117876] get_later_stmt used on stmts not in the same BB

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117876

--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:5ab3f091b3eb42795340d3c9cea8aaec2060693c

commit r15-5863-g5ab3f091b3eb42795340d3c9cea8aaec2060693c
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Dec 2 11:07:46 2024 +0100

    tree-optimization/116352 - SLP scheduling and stmt order

    The PR uncovers unchecked constraints on the ability to code-generate
    with SLP but also latent issues with regard to stmt order checking
    since loop (early-break) and BB (for quite some time) vectorization
    are no longer constraint to single-BBs.  In particular get_later_stmt
    simply compares UIDs of stmts, but that's only reliable when they
    are in the same BB.

    For the PR in question the problematical case is demoting a SLP node
    to external which fails to check we can actually code generate this
    in the way we do (using get_later_stmt).  The following thus adds
    checking that we demote to external only when all defs are from
    the same BB.

    We no longer vectorize gcc.dg/vect/bb-slp-49.c but the testcase was
    for a wrong-code issue and the vectorization done is a no-op.

            PR tree-optimization/116352
            PR tree-optimization/117876
            * tree-vect-slp.cc (vect_slp_can_convert_to_external): New.
            (vect_slp_convert_to_external): Call it.
            (vect_build_slp_tree_2): Likewise.

            * gcc.dg/vect/pr116352.c: New testcase.
            * gcc.dg/vect/bb-slp-49.c: Remove vectorization check.