[Bug tree-optimization/87147] [9 Regression] GCC miscompiles at -O3 on valid code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87147

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Thu Aug 30 12:37:10 2018
New Revision: 263980

URL: https://gcc.gnu.org/viewcvs?rev=263980&root=gcc&view=rev
Log:
2018-08-30  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/87147
        * tree-ssa-sccvn.c (SSA_VISITED): New function.
        (visit_phi): When the degenerate result is from the backedge and
        we didn't visit its definition yet drop to VARYING.
        (do_rpo_vn): Properly mark blocks with incoming backedges as
executable.

        * gcc.dg/torture/pr87147.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr87147.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-sccvn.c