[turbofan] Eliminate redundant masking operations for word8/word16 stores.

test/unittests/compiler/machine-operator-reducer-unittest.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 "src/base/bits.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/compiler/typer.h"
 #include "test/unittests/compiler/graph-unittest.h"
 
@@ skipping 636 matching lines @@
       EXPECT_THAT(r.replacement(),
                   IsInt32Constant(base::bits::SignedSubOverflow32(x, y, &z)));
 
       r = Reduce(graph()->NewNode(common()->Projection(0), add));
       ASSERT_TRUE(r.Changed());
       EXPECT_THAT(r.replacement(), IsInt32Constant(z));
     }
   }
 }
 
+
+// -----------------------------------------------------------------------------
+// Store
+
+
+TEST_F(MachineOperatorReducerTest, StoreRepWord8WithWord32And) {
+  const StoreRepresentation rep(kRepWord8, kNoWriteBarrier);
+  Node* const base = Parameter(0);
+  Node* const index = Parameter(1);
+  Node* const value = Parameter(2);
+  Node* const effect = graph()->start();
+  Node* const control = graph()->start();
+  TRACED_FOREACH(uint32_t, x, kUint32Values) {
+    Node* const node =
+        graph()->NewNode(machine()->Store(rep), base, index,
+                         graph()->NewNode(machine()->Word32And(), value,
+                                          Uint32Constant(x | 0xffu)),
+                         effect, control);
+
+    Reduction r = Reduce(node);
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(),
+                IsStore(rep, base, index, value, effect, control));
+  }
+}
+
+
+TEST_F(MachineOperatorReducerTest, StoreRepWord16WithWord32And) {
+  const StoreRepresentation rep(kRepWord16, kNoWriteBarrier);
+  Node* const base = Parameter(0);
+  Node* const index = Parameter(1);
+  Node* const value = Parameter(2);
+  Node* const effect = graph()->start();
+  Node* const control = graph()->start();
+  TRACED_FOREACH(uint32_t, x, kUint32Values) {
+    Node* const node =
+        graph()->NewNode(machine()->Store(rep), base, index,
+                         graph()->NewNode(machine()->Word32And(), value,
+                                          Uint32Constant(x | 0xffffu)),
+                         effect, control);
+
+    Reduction r = Reduce(node);
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(),
+                IsStore(rep, base, index, value, effect, control));
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8