Hi All,

Here is a patch for 481.wrf preformance regression for avx2 which is
sligthly modified mask store optimization. This transformation allows
perform unpredication for semi-hammock containing masked stores, other
words if we have a loop like
for (i=0; i<n; i++)
  if (c[i]) {
    p1[i] += 1;
    p2[i] = p3[i] +2;
  }

then it will be transformed to
   if (!mask__ifc__42.18_165 == { 0, 0, 0, 0, 0, 0, 0, 0 }) {
     vect__11.19_170 = MASK_LOAD (vectp_p1.20_168, 0B, mask__ifc__42.18_165);
     vect__12.22_172 = vect__11.19_170 + vect_cst__171;
     MASK_STORE (vectp_p1.23_175, 0B, mask__ifc__42.18_165, vect__12.22_172);
     vect__18.25_182 = MASK_LOAD (vectp_p3.26_180, 0B, mask__ifc__42.18_165);
     vect__19.28_184 = vect__18.25_182 + vect_cst__183;
     MASK_STORE (vectp_p2.29_187, 0B, mask__ifc__42.18_165, vect__19.28_184);
   }
i.e. it will put all computations related to masked stores to semi-hammock.

Bootstrapping and regression testing did not show any new failures.

ChangeLog:
2015-11-30  Yuri Rumyantsev  <ysrumyan@gmail.com>

PR middle-end/68542
* config/i386/i386.c (ix86_expand_branch): Implement integral vector
comparison with boolean result.
* config/i386/sse.md (define_expand "cbranch<mode>4): Add define-expand
for vector comparion with eq/ne only.
* fold-const.c (fold_relational_const): Add handling of vector
comparison with boolean result.
* tree-cfg.c (verify_gimple_comparison): Add argument CODE, allow
comparison of vector operands with boolean result for EQ/NE only.
(verify_gimple_assign_binary): Adjust call for verify_gimple_comparison.
(verify_gimple_cond): Likewise.
* tree-ssa-forwprop.c (combine_cond_expr_cond): Do not perform
combining for non-compatible vector types.
* tree-vect-loop.c (is_valid_sink): New function.
(optimize_mask_stores): Likewise.
* tree-vect-stmts.c (vectorizable_mask_load_store): Initialize
has_mask_store field of vect_info.
* tree-vectorizer.c (vectorize_loops): Invoke optimaze_mask_stores for
vectorized loops having masked stores.
* tree-vectorizer.h (loop_vec_info): Add new has_mask_store field and
correspondent macros.
(optimize_mask_stores): Add prototype.
* tree-vrp.c (register_edge_assert_for): Do not handle NAME with vector
type.

gcc/testsuite/ChangeLog:
* gcc.target/i386/avx2-vect-mask-store-move1.c: New test.