[turbofan] Turn IrOpcode::Mnemonic() into a table lookup.

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_
 
 // Opcodes for control operators.
 #define INNER_CONTROL_OP_LIST(V) \
   V(Dead)                        \
@@ skipping 250 matching lines @@
 #define DECLARE_OPCODE(x) k##x,
     ALL_OP_LIST(DECLARE_OPCODE)
 #undef DECLARE_OPCODE
     kLast = -1
 #define COUNT_OPCODE(x) +1
             ALL_OP_LIST(COUNT_OPCODE)
 #undef COUNT_OPCODE
   };
 
   // Returns the mnemonic name of an opcode.
-  static const char* Mnemonic(Value val) {
-    // TODO(turbofan): make this a table lookup.
-    switch (val) {
-#define RETURN_NAME(x) \
-  case k##x:           \
-    return #x;
-      ALL_OP_LIST(RETURN_NAME)
-#undef RETURN_NAME
-      default:
-        return "UnknownOpcode";
-    }
-  }
+  static char const* Mnemonic(Value value);
 
   static bool IsJsOpcode(Value val) {
     switch (val) {
 // TODO(turbofan): make this a range check.
 #define RETURN_NAME(x) \
   case k##x:           \
     return true;
       JS_OP_LIST(RETURN_NAME)
 #undef RETURN_NAME
       default:
@@ skipping 40 matching lines @@
         return false;
     }
   }
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPCODES_H_