[turbofan] Introduce an ExternalPointer type.

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>
 
 #include "src/globals.h"
@@ skipping 23 matching lines @@
   V(End)
 
 // Opcodes for constant operators.
 #define CONSTANT_OP_LIST(V)   \
   V(Int32Constant)            \
   V(Int64Constant)            \
   V(Float32Constant)          \
   V(Float64Constant)          \
   V(ExternalConstant)         \
   V(NumberConstant)           \
+  V(PointerConstant)          \
   V(HeapConstant)             \
   V(RelocatableInt32Constant) \
   V(RelocatableInt64Constant)
 
 #define INNER_OP_LIST(V)  \
   V(Select)               \
   V(Phi)                  \
   V(EffectPhi)            \
   V(InductionVariablePhi) \
   V(Checkpoint)           \
@@ skipping 738 matching lines @@
   }
 };
 
 V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream&, IrOpcode::Value);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPCODES_H_