[Bug tree-optimization/33315] stores not commoned by sinking

cvs-commit at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Fri May 15 06:56:33 GMT 2020


--- Comment #15 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:


commit r11-408-g84935c9822183ce403bb361c5f405711b9a808c6
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Apr 15 12:09:01 2020 +0200

    tree-optimization/33315 - common stores during sinking

    This implements commoning of stores to a common successor in
    a simple ad-hoc way.  I've decided to put it into the code sinking
    pass since, well, it sinks stores.  It's still separate since
    it does not really sink code into less executed places.

    It's ad-hoc since it does not perform any dataflow or alias analysis
    but simply only considers trailing stores in a block, iteratively
    though.  If the stores are from different values a PHI node is
    inserted to merge them.  gcc.dg/tree-ssa/split-path-7.c shows
    that path splitting will eventually undo this very transform,
    I've decided to not bother with it and simply disable sinking for
    the particular testcase.

    Doing this transform is good for code size when the stores are
    from constants, once we have to insert PHIs the situation becomes
    less clear but it's a transform we do elsewhere as well
    (cselim for one), and reversing the transform should be easy.

    2020-05-15  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/33315
            * tree-ssa-sink.c: Include tree-eh.h.
            (sink_stats): Add commoned member.
            (sink_common_stores_to_bb): New function implementing store
            commoning by sinking to the successor.
            (sink_code_in_bb): Call it, pass down TODO_cleanup_cfg returned.
            (pass_sink_code::execute): Likewise.  Record commoned stores
            in statistics.

            * gcc.dg/tree-ssa/ssa-sink-13.c: New testcase.
            * gcc.dg/tree-ssa/ssa-sink-14.c: Likewise.
            * gcc.dg/tree-ssa/split-path-7.c: Disable sinking.

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