[Bug tree-optimization/66502] SCCVN can't handle PHIs optimistically optimally

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66502

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Thu Aug 13 07:06:10 2015
New Revision: 226850

URL: https://gcc.gnu.org/viewcvs?rev=226850&root=gcc&view=rev
Log:
2015-08-13  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/66502
        PR tree-optimization/67167
        * tree-ssa-sccvn.c (vn_phi_compute_hash): Do not include
        backedge arguments.
        (vn_phi_lookup): Adjust.
        (vn_phi_insert): Likewise.
        (visit_phi): Prefer to value-number to another PHI node
        over value-numbering to a PHI argument.
        (init_scc_vn): Mark DFS back edges.

        * gcc.dg/tree-ssa/ssa-fre-46.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-46.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-sccvn.c