[turbofan] Optimize JSConvertReceiver if we know something about the receiver.

src/compiler/js-operator.h

 // Copyright 2013 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_OPERATOR_H_
 #define V8_COMPILER_JS_OPERATOR_H_
 
 #include "src/runtime/runtime.h"
 
 namespace v8 {
@@ skipping 26 matching lines @@
 };
 
 bool operator==(VectorSlotPair const&, VectorSlotPair const&);
 bool operator!=(VectorSlotPair const&, VectorSlotPair const&);
 
 size_t hash_value(VectorSlotPair const&);
 
 
 // Defines hints about receiver values based on structural knowledge. This is
 // used as a parameter by JSConvertReceiver operators.
-enum class ConvertReceiverMode {
+enum class ConvertReceiverMode : int {
   kNullOrUndefined,     // Guaranteed to be null or undefined.
   kNotNullOrUndefined,  // Guaranteed to never be null or undefined.
   kAny                  // No specific knowledge about receiver.
 };
 
-size_t hash_value(ConvertReceiverMode const&);
+size_t hash_value(ConvertReceiverMode);
 
-std::ostream& operator<<(std::ostream&, ConvertReceiverMode const&);
+std::ostream& operator<<(std::ostream&, ConvertReceiverMode);
 
-const ConvertReceiverMode& ConvertReceiverModeOf(const Operator* op);
+ConvertReceiverMode ConvertReceiverModeOf(const Operator* op);
 
 
 // Defines whether tail call optimization is allowed.
 enum TailCallMode { NO_TAIL_CALLS, ALLOW_TAIL_CALLS };
 
 
 // Defines the arity and the call flags for a JavaScript function call. This is
 // used as a parameter by JSCallFunction operators.
 class CallFunctionParameters final {
  public:
@@ skipping 459 matching lines @@
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(JSOperatorBuilder);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_OPERATOR_H_