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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/63844] [4.8/4.9/5 Regression] open mp parallelization prevents vectorization
Date: Tue, 18 Nov 2014 10:59:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63844

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|jakub at gcc dot gnu.org           |rguenth at gcc dot gnu.org

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
The issue here is the induction variable is shared?

  <bb 5>:
  # _17 = PHI <0(2), _11(4)>
  _6 = b[_17];
  _7 = c[_17];
  _8 = _6 + _7;
  a[_17] = _8;
  _10 = .omp_data_i_3(D)->i;
  _11 = _10 + 1;
  .omp_data_i_3(D)->i = _11;
  if (_11 <= 9999999)
    goto <bb 4>;
  else
    goto <bb 3>;

and we didn't apply store-motion to it:

Memory reference 1: b[_17]
Memory reference 2: c[_17]
Memory reference 3: a[_17]
Memory reference 4: .omp_data_i_3(D)->i
...
Querying dependency of refs 4 and 1: dependent.
Querying dependencies of ref 4 in loop 1: dependent

I think the static chain never points to global decls thus we could
special-case this.  We could also treat members of the frame as
non-allocated and thus not worry about trailing arrays and such.
Unfortunately the .omp_data_i is a regular function parameter and
not a static chain :/