[turbofan] Add streaming operator for opcodes to ease debugging.

src/compiler/opcodes.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_OPCODES_H_
 #define V8_COMPILER_OPCODES_H_
 
+#include <iosfwd>
+
 // Opcodes for control operators.
 #define CONTROL_OP_LIST(V) \
   V(Start)                 \
   V(Dead)                  \
   V(Loop)                  \
   V(Branch)                \
   V(Switch)                \
   V(IfTrue)                \
   V(IfFalse)               \
   V(IfSuccess)             \
@@ skipping 323 matching lines @@
   }
 
   // Returns true if opcode for comparison operator.
   static bool IsComparisonOpcode(Value value) {
     return (kJSEqual <= value && value <= kJSGreaterThanOrEqual) ||
            (kNumberEqual <= value && value <= kStringLessThanOrEqual) ||
            (kWord32Equal <= value && value <= kFloat64LessThanOrEqual);
   }
 };
 
+std::ostream& operator<<(std::ostream&, IrOpcode::Value);
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPCODES_H_