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Subject: [Bug tree-optimization/103721] [12 regression] wrong code generated
 for loop with conditional since r12-4790-g4b3a325f07acebf4
Date: Fri, 21 Jan 2022 10:19:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103721

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

https://gcc.gnu.org/g:eb5ee6464809e051e0292471597931a660485658

commit r12-6787-geb5ee6464809e051e0292471597931a660485658
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Thu Jan 20 10:28:26 2022 +0100

    Reset relations when crossing backedges.

    As discussed in PR103721, the problem here is that we are crossing a
    backedge and causing us to use relations from a previous iteration of a
    loop.

    This handles the testcases in both PR103721 and PR104067 which are vari=
ants
    of the same thing.

    Tested on x86-64 Linux with the usual regstrap as well as verifying the
    thread count before and after the patch.  The number of threads is
    reduced by a miniscule amount.

    gcc/ChangeLog:

            PR tree-optimization/103721
            * gimple-range-path.cc
            (path_range_query::relations_may_be_invalidated): New.
            (path_range_query::compute_ranges_in_block): Reset relations if
            they may be invalidated.
            (path_range_query::maybe_register_phi_relation): Exit if relati=
ons
            may be invalidated on incoming edge.
            (path_range_query::compute_phi_relations): Pass incoming PHI ed=
ge
            to maybe_register_phi_relation.
            * gimple-range-path.h (relations_may_be_invalidated): New.
            (maybe_register_phi_relation): Pass edge instead of tree.
            * tree-ssa-threadbackward.cc (back_threader::back_threader):
            Mark DFS edges.
            * value-relation.cc (path_oracle::path_oracle): Call
            mark_dfs_back_edges.
            (path_oracle::register_relation): Add SSA names to m_registered
            bitmap.
            (path_oracle::reset_path): Clear m_registered bitmap.
            * value-relation.h (path_oracle::set_root_oracle): New.

    gcc/testsuite/ChangeLog:

            * gcc.dg/pr103721-2.c: New test.
            * gcc.dg/pr103721.c: New test.=