[turbofan] Make sure Operator is really immutable.

src/compiler/simplified-operator.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_SIMPLIFIED_OPERATOR_H_
 #define V8_COMPILER_SIMPLIFIED_OPERATOR_H_
 
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/opcodes.h"
 #include "src/zone.h"
@@ skipping 63 matching lines @@
   static OStream& PrintTo(OStream& os, const ElementAccess& val) {  // NOLINT
     return os << val.header_size;
   }
   static int HashCode(const ElementAccess& val) {
     return (val.header_size < 16) | (val.machine_type & 0xffff);
   }
   static bool Equals(const ElementAccess& lhs, const ElementAccess& rhs);
 };
 
 
-inline const FieldAccess FieldAccessOf(Operator* op) {
+inline const FieldAccess FieldAccessOf(const Operator* op) {
   DCHECK(op->opcode() == IrOpcode::kLoadField ||
          op->opcode() == IrOpcode::kStoreField);
-  return static_cast<Operator1<FieldAccess>*>(op)->parameter();
+  return OpParameter<FieldAccess>(op);
 }
 
 
-inline const ElementAccess ElementAccessOf(Operator* op) {
+inline const ElementAccess ElementAccessOf(const Operator* op) {
   DCHECK(op->opcode() == IrOpcode::kLoadElement ||
          op->opcode() == IrOpcode::kStoreElement);
-  return static_cast<Operator1<ElementAccess>*>(op)->parameter();
+  return OpParameter<ElementAccess>(op);
 }
 
 
 // Interface for building simplified operators, which represent the
 // medium-level operations of V8, including adding numbers, allocating objects,
 // indexing into objects and arrays, etc.
 // All operators are typed but many are representation independent.
 
 // Number values from JS can be in one of these representations:
 //   - Tagged: word-sized integer that is either
@@ skipping 76 matching lines @@
 #undef SIMPLE
 
  private:
   Zone* zone_;
 };
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_COMPILER_SIMPLIFIED_OPERATOR_H_