[Bug tree-optimization/106809] [12 regression] large bison grammars compilation got a lot slower, mainly due to -Wuninitialized

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106809

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:e08dd36f90e74cd5be615b1ca82a38896434d48c

commit r12-8751-ge08dd36f90e74cd5be615b1ca82a38896434d48c
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Sep 2 13:36:13 2022 +0200

    tree-optimization/106809 - compile time hog in VN

    The dominated_by_p_w_unex function is prone to high compile time.
    With GCC 12 we introduced a VN run for uninit diagnostics which now
    runs into a degenerate case with bison generated code.  Fortunately
    this case is easy to fix with a simple extra check - a more
    general fix needs more work.

            PR tree-optimization/106809
            * tree-ssa-sccvn.cc (dominaged_by_p_w_unex): Check we have
            more than one successor before doing extra work.

            * gcc.dg/torture/pr106809.c: New testcase.

    (cherry picked from commit be1b42de9c151d46c89f9a8f82d4c5839a19ea94)