[Bug rtl-optimization/78200] [7 Regression] 429.mcf of cpu2006 regresses in GCC trunk for avx2 target.

[venkataramanan.kumar at amd dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78200

--- Comment #7 from Venkataramanan <venkataramanan.kumar at amd dot com> ---
Bisecting shows non canonical gimple generation at r238370.

--snip--
commit f3dce1cdd016e16cf9dc051d127bdf6eb58430fc
Author: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Fri Jul 15 10:53:29 2016 +0000

    2016-07-15  Richard Biener  <rguenther@suse.de>

        * tree-ssa-pre.c (get_representative_for): Make sure to return
        the value number of SSA names.
        (phi_translate_1): get_representative_for cannot return NULL.
        (do_pre_regular_insertion): Remove redundant call to
        fully_constant_expression.
        (do_pre_partial_partial_insertion): Likewise.


    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@238370
138bc75d-0d04-0410-961f-82ee72b054a4
--snip--

r238370 test.c.148t.ifcvt
    ;;   basic block 30, loop depth 1, count 0, freq 407, maybe hot
    ;;    prev block 29, next block 31, flags: (NEW, REACHABLE)
    ;;    pred:       28 [64.0%]  (FALSE_VALUE,EXECUTABLE)
      _71 = _109 == 2;
      _15 = if_conversion_var_108 > 0;
      _70 = _71 & _15;
      if (_70 != 0)
        goto <bb 31>;
      else
        goto <bb 32>;


r238369 test.c.148t.ifcvt

  ;;   basic block 30, loop depth 1, count 0, freq 407, maybe hot
    ;;    prev block 29, next block 31, flags: (NEW, REACHABLE)
    ;;    pred:       28 [64.0%]  (FALSE_VALUE,EXECUTABLE)
      _26 = _73 == 2;
      _38 = if_conversion_var_72 > 0;
      _86 = _26 & _38;
      if (_86 != 0)
        goto <bb 31>;
      else
        goto <bb 32>;
    ;;    succ:       31 [34.0%]  (TRUE_VALUE,EXECUTABLE)
    ;;                32 [66.0%]  (FALSE_VALUE,EXECUTABLE)