[Bug tree-optimization/87176] [9 Regression] wrong code at -Os and above on x86-64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87176

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Tue Sep  4 10:55:46 2018
New Revision: 264077

URL: https://gcc.gnu.org/viewcvs?rev=264077&root=gcc&view=rev
Log:
2018-09-04  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/87176
        * tree-ssa-sccvn.c (visit_phi): Remove redundant allsame
        variable.  When value-numbering a virtual PHI node make sure
        to not value-number to the backedge value.

        * gcc.dg/torture/pr87176.c: New testcase.
        * gcc.dg/torture/ssa-fre-1.c: Likewise.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr87176.c
    trunk/gcc/testsuite/gcc.dg/torture/ssa-fre-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-sccvn.c