[turbofan] Some common operators are globally shared singletons.

src/compiler/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_OPERATOR_H_
 #define V8_COMPILER_OPERATOR_H_
 
 #include "src/base/flags.h"
 #include "src/ostreams.h"
 #include "src/unique.h"
 
 namespace v8 {
 namespace internal {
-
-// Forward declarations.
-class ExternalReference;
-
-
 namespace compiler {
 
 // An operator represents description of the "computation" of a node in the
 // compiler IR. A computation takes values (i.e. data) as input and produces
 // zero or more values as output. The side-effects of a computation must be
 // captured by additional control and data dependencies which are part of the
 // IR graph.
 // Operators are immutable and describe the statically-known parts of a
 // computation. Thus they can be safely shared by many different nodes in the
 // IR graph, or even globally between graphs. Operators can have "static
@@ skipping 111 matching lines @@
 struct StaticParameterTraits {
   static OStream& PrintTo(OStream& os, T val) {  // NOLINT
     return os << "??";
   }
   static int HashCode(T a) { return 0; }
   static bool Equals(T a, T b) {
     return false;  // Not every T has a ==. By default, be conservative.
   }
 };
 
-template <>
-struct StaticParameterTraits<ExternalReference> {
-  static OStream& PrintTo(OStream& os, ExternalReference reference);  // NOLINT
-  static int HashCode(ExternalReference reference);
-  static bool Equals(ExternalReference lhs, ExternalReference rhs);
-};
-
 // Specialization for static parameters of type {int}.
 template <>
 struct StaticParameterTraits<int> {
   static OStream& PrintTo(OStream& os, int val) {  // NOLINT
     return os << val;
   }
   static int HashCode(int a) { return a; }
   static bool Equals(int a, int b) { return a == b; }
 };
 
@@ skipping 98 matching lines @@
 template <typename T>
 static inline const T& OpParameter(const Operator* op) {
   return reinterpret_cast<const Operator1<T>*>(op)->parameter();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPERATOR_H_