[Bug tree-optimization/126028] GCC trunk vs ICX : Missed SLP vectorization

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126028

--- Comment #7 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:5e63fb58f84e3ce19cb336710f69094ecbd4b63d

commit r17-3220-g5e63fb58f84e3ce19cb336710f69094ecbd4b63d
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Jul 15 15:33:31 2026 +0200

    tree-optimization/126028 - vector placement and live lane extracts

    We currently conservatively assume vector stmt placement when
    determining whether we can place a lane extraction for a live
    scalar value.  The following attempts to improve this by
    pre-computing an insertion place for all nodes and using that
    to improve live lane extract feasibility computation.

    While we'd like to re-use such computation for the actual insertion
    there are issues preventing that such as scalar stmts eventually
    getting elided and thus iterators invalidated.  So the following
    re-computes the scheduling again but at least validates the earlier
    schedule against it.

    For PR126099 I have to turn this into schedule validation, but
    not as part of this initial work.

    The major pain-point of chosing a gimple * as scheduling anchor
    are that for placement in empty BBs that is NULL (this hits us
    with region boundaries), a gsi would be able to handle this
    case.  But then, as you can see in the blob that attempts to
    verify the early schedule constraints hold at transform time
    there's issues like the scalar stmts vanishing and statements
    being inserted.  As most viable and ugly option I briefly
    considered inserting GIMPLE_NOPs as anchors.  Instead of
    vect_schedule_slp_node computing the insertion place this
    could be also handled (or just overridden?) by vectorizable_*
    which sometimes has its own idea where to place.

            PR tree-optimization/126028
            * tree-vectorizer.h (_slp_tree::si): New member.
            (vect_schedule_slp): Adjust prototype.
            * tree-vect-loop.cc (vect_transform_loop): Adjust.
            * tree-vect-slp.cc (_slp_tree::_slp_tree): Initialize si.
            (vect_bb_slp_mark_live_stmts): Use vector stmt placement
            constraint computed by pre-scheduling of SLP nodes.
            (vect_slp_analyze_bb_1): Pre-schedule SLP nodes before
            computing live lane extraction points.
            (vect_slp_region): Adjust.
            (vect_schedule_slp_node): Add parameter indicating to whether
            we should perform pre-scehduling or not.  Compute the
            insertion place suitable for dominance checks when
            pre-scheduling.
            (vect_schedule_scc): Adjust.
            (vect_schedule_slp): Likewise.

            * gcc.dg/vect/bb-slp-46.c: Un-XFAIL.
            * gcc.dg/vect/bb-slp-pr126053.c: New testcase.
            * gcc.dg/vect/costmodel/x86_64/costmodel-pr126028.c: Likewise.