[turbofan] Optimize ToName conversion.

ToName conversion, i.e., ToPropertykey() is the
identify for strings and symbols.

BUG=v8:5623

Review-Url: https://codereview.chromium.org/2494073002
Cr-Commit-Position: refs/heads/master@{#40924}

src/compiler/js-typed-lowering.cc

@@ -985,6 +985,17 @@ Reduction JSTypedLowering::ReduceJSToInteger(Node* node) {
   return NoChange();
 }
 
+Reduction JSTypedLowering::ReduceJSToName(Node* node) {
+  Node* const input = NodeProperties::GetValueInput(node, 0);
+  Type* const input_type = NodeProperties::GetType(input);
+  if (input_type->Is(Type::Name())) {
+    // JSToName(x:name) => x
+    ReplaceWithValue(node, input);
+    return Replace(input);
+  }
+  return NoChange();
+}
+
 Reduction JSTypedLowering::ReduceJSToLength(Node* node) {
   Node* input = NodeProperties::GetValueInput(node, 0);
   Type* input_type = NodeProperties::GetType(input);
@@ -2193,6 +2204,8 @@ Reduction JSTypedLowering::Reduce(Node* node) {
       return ReduceJSToInteger(node);
     case IrOpcode::kJSToLength:
       return ReduceJSToLength(node);
+    case IrOpcode::kJSToName:
+      return ReduceJSToName(node);
     case IrOpcode::kJSToNumber:
       return ReduceJSToNumber(node);
     case IrOpcode::kJSToString:

src/compiler/js-typed-lowering.h

@@ -63,6 +63,7 @@ class V8_EXPORT_PRIVATE JSTypedLowering final
   Reduction ReduceJSToBoolean(Node* node);
   Reduction ReduceJSToInteger(Node* node);
   Reduction ReduceJSToLength(Node* node);
+  Reduction ReduceJSToName(Node* node);
   Reduction ReduceJSToNumberInput(Node* input);
   Reduction ReduceJSToNumber(Node* node);
   Reduction ReduceJSToStringInput(Node* input);

test/unittests/compiler/js-typed-lowering-unittest.cc

@@ -121,8 +121,42 @@ TEST_F(JSTypedLoweringTest, JSToBooleanWithAny) {
 
 
 // -----------------------------------------------------------------------------
-// JSToNumber
+// JSToName
+
+TEST_F(JSTypedLoweringTest, JSToNameWithString) {
+  Node* const input = Parameter(Type::String(), 0);
+  Node* const context = Parameter(Type::Any(), 1);
+  Node* const effect = graph()->start();
+  Node* const control = graph()->start();
+  Reduction r = Reduce(graph()->NewNode(javascript()->ToName(), input, context,
+                                        EmptyFrameState(), effect, control));
+  ASSERT_TRUE(r.Changed());
+  EXPECT_EQ(input, r.replacement());
+}
 
+TEST_F(JSTypedLoweringTest, JSToNameWithSymbol) {
+  Node* const input = Parameter(Type::Symbol(), 0);
+  Node* const context = Parameter(Type::Any(), 1);
+  Node* const effect = graph()->start();
+  Node* const control = graph()->start();
+  Reduction r = Reduce(graph()->NewNode(javascript()->ToName(), input, context,
+                                        EmptyFrameState(), effect, control));
+  ASSERT_TRUE(r.Changed());
+  EXPECT_EQ(input, r.replacement());
+}
+
+TEST_F(JSTypedLoweringTest, JSToNameWithAny) {
+  Node* const input = Parameter(Type::Any(), 0);
+  Node* const context = Parameter(Type::Any(), 1);
+  Node* const effect = graph()->start();
+  Node* const control = graph()->start();
+  Reduction r = Reduce(graph()->NewNode(javascript()->ToName(), input, context,
+                                        EmptyFrameState(), effect, control));
+  ASSERT_FALSE(r.Changed());
+}
+
+// -----------------------------------------------------------------------------
+// JSToNumber
 
 TEST_F(JSTypedLoweringTest, JSToNumberWithPlainPrimitive) {
   Node* const input = Parameter(Type::PlainPrimitive(), 0);