[turbofan] Properly implement %_ClassOf intrinsic.

src/compiler/js-intrinsic-lowering.h

 // Copyright 2015 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.
 
 #ifndef V8_COMPILER_JS_INTRINSIC_LOWERING_H_
 #define V8_COMPILER_JS_INTRINSIC_LOWERING_H_
 
 #include "src/base/compiler-specific.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph-reducer.h"
@@ skipping 49 matching lines @@
   Reduction ReduceToString(Node* node);
   Reduction ReduceCall(Node* node);
   Reduction ReduceGetSuperConstructor(Node* node);
 
   // TODO(turbofan): collection.js support; drop once Maps and Sets are
   // converted to proper CodeStubAssembler based builtins.
   Reduction ReduceJSCollectionGetTable(Node* node);
   Reduction ReduceStringGetRawHashField(Node* node);
   Reduction ReduceTheHole(Node* node);
 
+  // TODO(turbofan): JavaScript builtins support; drop once all uses of
+  // %_ClassOf in JavaScript builtins are eliminated.
+  Reduction ReduceClassOf(Node* node);
+
   Reduction Change(Node* node, const Operator* op);
   Reduction Change(Node* node, const Operator* op, Node* a, Node* b);
   Reduction Change(Node* node, const Operator* op, Node* a, Node* b, Node* c);
   Reduction Change(Node* node, const Operator* op, Node* a, Node* b, Node* c,
                    Node* d);
   Reduction Change(Node* node, Callable const& callable,
                    int stack_parameter_count);
 
   Graph* graph() const;
   JSGraph* jsgraph() const { return jsgraph_; }
   Isolate* isolate() const;
   CommonOperatorBuilder* common() const;
   JSOperatorBuilder* javascript() const;
   SimplifiedOperatorBuilder* simplified() const;
   DeoptimizationMode mode() const { return mode_; }
 
   JSGraph* const jsgraph_;
   DeoptimizationMode const mode_;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_INTRINSIC_LOWERING_H_