[turbofan] Strip useless sign-extension for store8/store16.

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/base/division-by-constant.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 1114 matching lines @@
                          effect, control);
 
     Reduction r = Reduce(node);
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(),
                 IsStore(rep, base, index, value, effect, control));
   }
 }
 
 
+TEST_F(MachineOperatorReducerTest, StoreRepWord8WithWord32SarAndWord32Shl) {
+  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_FORRANGE(int32_t, x, 1, 24) {
+    Node* const node = graph()->NewNode(
+        machine()->Store(rep), base, index,
+        graph()->NewNode(
+            machine()->Word32Sar(),
+            graph()->NewNode(machine()->Word32Shl(), value, Int32Constant(x)),
+            Int32Constant(x)),
+        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));
   }
 }
 
+
+TEST_F(MachineOperatorReducerTest, StoreRepWord16WithWord32SarAndWord32Shl) {
+  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_FORRANGE(int32_t, x, 1, 16) {
+    Node* const node = graph()->NewNode(
+        machine()->Store(rep), base, index,
+        graph()->NewNode(
+            machine()->Word32Sar(),
+            graph()->NewNode(machine()->Word32Shl(), value, Int32Constant(x)),
+            Int32Constant(x)),
+        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