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

test/unittests/compiler/machine-operator-reducer-unittest.cc

Index: test/unittests/compiler/machine-operator-reducer-unittest.cc
diff --git a/test/unittests/compiler/machine-operator-reducer-unittest.cc b/test/unittests/compiler/machine-operator-reducer-unittest.cc
index 51697163ae6f17fda9213e0adf7b98f34c9cbb7c..268afc4b275135aa2e407eb98f935a8ab3fe5b13 100644
--- a/test/unittests/compiler/machine-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/machine-operator-reducer-unittest.cc
@@ -1132,6 +1132,30 @@ TEST_F(MachineOperatorReducerTest, StoreRepWord8WithWord32And) {
 }
 
 
+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);
@@ -1153,6 +1177,30 @@ TEST_F(MachineOperatorReducerTest, StoreRepWord16WithWord32And) {
   }
 }
 
+
+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