[turbofan] Introduce ObjectIsString operator.

src/compiler/change-lowering.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/compiler/change-lowering.h"
 
 #include "src/address-map.h"
 #include "src/code-factory.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/linkage.h"
@@ skipping 31 matching lines @@
     case IrOpcode::kLoadField:
       return LoadField(node);
     case IrOpcode::kStoreField:
       return StoreField(node);
     case IrOpcode::kLoadElement:
       return LoadElement(node);
     case IrOpcode::kStoreElement:
       return StoreElement(node);
     case IrOpcode::kAllocate:
       return Allocate(node);
+    case IrOpcode::kObjectIsNumber:
+      return ObjectIsNumber(node);
     case IrOpcode::kObjectIsReceiver:
       return ObjectIsReceiver(node);
     case IrOpcode::kObjectIsSmi:
       return ObjectIsSmi(node);
-    case IrOpcode::kObjectIsNumber:
-      return ObjectIsNumber(node);
+    case IrOpcode::kObjectIsString:
+      return ObjectIsString(node);
     case IrOpcode::kObjectIsUndetectable:
       return ObjectIsUndetectable(node);
     default:
       return NoChange();
   }
   UNREACHABLE();
   return NoChange();
 }
 
 
@@ skipping 681 matching lines @@
 
 Reduction ChangeLowering::ObjectIsSmi(Node* node) {
   node->ReplaceInput(0,
                      graph()->NewNode(machine()->WordAnd(), node->InputAt(0),
                                       jsgraph()->IntPtrConstant(kSmiTagMask)));
   node->AppendInput(graph()->zone(), jsgraph()->IntPtrConstant(kSmiTag));
   NodeProperties::ChangeOp(node, machine()->WordEqual());
   return Changed(node);
 }
 
+Reduction ChangeLowering::ObjectIsString(Node* node) {
+  Node* input = NodeProperties::GetValueInput(node, 0);
+  Node* check = IsSmi(input);
+  Node* branch = graph()->NewNode(common()->Branch(), check, graph()->start());
+  Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+  Node* vtrue = jsgraph()->Int32Constant(0);
+  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+  Node* vfalse =
+      graph()->NewNode(machine()->Uint32LessThan(),
+                       LoadMapInstanceType(LoadHeapObjectMap(input, if_false)),
+                       jsgraph()->Uint32Constant(FIRST_NONSTRING_TYPE));
+  Node* control = graph()->NewNode(common()->Merge(2), if_true, if_false);
+  node->ReplaceInput(0, vtrue);
+  node->AppendInput(graph()->zone(), vfalse);
+  node->AppendInput(graph()->zone(), control);
+  NodeProperties::ChangeOp(node, common()->Phi(MachineRepresentation::kBit, 2));
+  return Changed(node);
+}
+
 Isolate* ChangeLowering::isolate() const { return jsgraph()->isolate(); }
 
 
 Graph* ChangeLowering::graph() const { return jsgraph()->graph(); }
 
 
 CommonOperatorBuilder* ChangeLowering::common() const {
   return jsgraph()->common();
 }
 
 
 MachineOperatorBuilder* ChangeLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8