[turbofan] optimize moves into merges

src/compiler/instruction.h

 // 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.
 
 #ifndef V8_COMPILER_INSTRUCTION_H_
 #define V8_COMPILER_INSTRUCTION_H_
 
 #include <deque>
 #include <iosfwd>
 #include <map>
@@ skipping 64 matching lines @@
 #undef INSTRUCTION_OPERAND_PREDICATE
   bool Equals(const InstructionOperand* other) const {
     return value_ == other->value_;
   }
 
   void ConvertTo(Kind kind, int index) {
     DCHECK(kind != UNALLOCATED && kind != INVALID);
     ConvertTo(kind, index, kInvalidVirtualRegister);
   }
 
+  // Useful for map/set keys.
+  bool operator<(const InstructionOperand& op) const {
+    return value_ < op.value_;
+  }
+
  protected:
   template <typename SubKindOperand>
   static SubKindOperand* New(Zone* zone, const SubKindOperand& op) {
     void* buffer = zone->New(sizeof(op));
     return new (buffer) SubKindOperand(op);
   }
 
   InstructionOperand(Kind kind, int index, int virtual_register) {
     ConvertTo(kind, index, virtual_register);
   }
@@ skipping 967 matching lines @@
 
 
 std::ostream& operator<<(std::ostream& os,
                          const PrintableInstructionSequence& code);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_H_