[x64/ia32] Deal with the non-transitivity of InstructionSelector::CanCover() when folding loads int…

test/cctest/compiler/test-branch-combine.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "test/cctest/cctest.h"
 #include "test/cctest/compiler/codegen-tester.h"
 #include "test/cctest/compiler/value-helper.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 439 matching lines @@
                                                              : eq_constant)
                      : (cmp.Float64Compare(input_a, input_b) ? eq_constant
                                                              : ne_constant);
           CHECK_EQ(expected, m.Call());
         }
       }
     }
   }
 }
 
+TEST(BranchCombineEffectLevel) {
+  // Test that the load doesn't get folded into the branch, as there's a store
+  // between them. See http://crbug.com/611976.
+  int32_t input = 0;
+
+  RawMachineAssemblerTester<int32_t> m;
+  Node* a = m.LoadFromPointer(&input, MachineType::Int32());
+  Node* compare = m.Word32And(a, m.Int32Constant(1));
+  Node* equal = m.Word32Equal(compare, m.Int32Constant(0));
+  m.StoreToPointer(&input, MachineRepresentation::kWord32, m.Int32Constant(1));
+
+  RawMachineLabel blocka, blockb;
+  m.Branch(equal, &blocka, &blockb);
+  m.Bind(&blocka);
+  m.Return(m.Int32Constant(42));
+  m.Bind(&blockb);
+  m.Return(m.Int32Constant(0));
+
+  CHECK_EQ(42, m.Call());
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8