[Bug tree-optimization/105142] [12 Regression] Wrong code with -O2 since r12-2591

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105142

--- Comment #12 from CVS 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:fc8d9e4497032dd295aac9414042163f92250b77

commit r12-8012-gfc8d9e4497032dd295aac9414042163f92250b77
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Apr 4 12:23:28 2022 +0200

    tree-optimization/105142 - wrong code with maybe_fold_{and,or}_comparisons

    The following avoids expanding definitions in regions conditionally
    executed under the condition A when simplifying A && B or A || B.
    This is done by passing down the basic-block of the outer condition
    to maybe_fold_{and,or}_comparisons, through the various helpers
    in gimple-fold.cc that might call back to maybe_fold_{and,or}_comparisons
    and ultimatively to maybe_fold_comparisons_from_match_pd where the
    fix is to provide a custom valueization hook to
    gimple_match_op::resimplify that avoids looking at definitions
    that do not dominate the outer block.

    For the testcase this avoids combining a stmt that invokes undefined
    integer overflow when the outer condition is false but it also
    aovids combining stmts with range information that is derived from
    the outer condition.

    The new parameter to maybe_fold_{and,or}_comparisons is defaulted
    to nullptr and I only adjusted the if-combine to pass down the
    outer block.  I think other callers like tree-if-conv have the
    same issue but it's not straight-forward as to what to do there.

    2022-04-05  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/105142
            * gimple-fold.h (maybe_fold_and_comparisons): Add defaulted
            basic-block parameter.
            (maybe_fold_or_comparisons): Likewise.
            * gimple-fold.cc (follow_outer_ssa_edges): New.
            (maybe_fold_comparisons_from_match_pd): Use follow_outer_ssa_edges
            when an outer condition basic-block is specified.
            (and_comparisons_1, and_var_with_comparison,
            and_var_with_comparison_1, or_comparisons_1,
            or_var_with_comparison, or_var_with_comparison_1): Receive and pass
            down the outer condition basic-block.
            * tree-ssa-ifcombine.cc (ifcombine_ifandif): Pass down the
            basic-block of the outer condition.

            * g++.dg/torture/pr105142.C: New testcase.