[Bug tree-optimization/23094] store ccp, or store copy prop misses an optimization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=23094

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Thu Nov 23 09:05:11 2017
New Revision: 255093

URL: https://gcc.gnu.org/viewcvs?rev=255093&root=gcc&view=rev
Log:
2017-11-23  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/23094
        * tree-ssa-sccvn.c (vuse_ssa_val): Handle VN_TOP when we
        come here from walking over backedges in the first iteration.
        (vn_reference_lookup_3): Skip clobbers that store the same value.

        * gcc.dg/tree-ssa/ssa-fre-61.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-61.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-sccvn.c