[turbofan] Introduce an ExternalPointer type.

src/compiler/js-graph.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_JS_GRAPH_H_
 #define V8_COMPILER_JS_GRAPH_H_
 
 #include "src/base/compiler-specific.h"
 #include "src/compiler/common-node-cache.h"
 #include "src/compiler/common-operator.h"
@@ skipping 90 matching lines @@
   }
 
   // Creates a Int32Constant/Int64Constant node, depending on the word size of
   // the target machine.
   // TODO(turbofan): Code using Int32Constant/Int64Constant to store pointer
   // constants is probably not serializable.
   Node* IntPtrConstant(intptr_t value) {
     return machine()->Is32() ? Int32Constant(static_cast<int32_t>(value))
                              : Int64Constant(static_cast<int64_t>(value));
   }
-  template <typename T>
-  Node* PointerConstant(T* value) {
-    return IntPtrConstant(bit_cast<intptr_t>(value));
-  }
 
   Node* RelocatableInt32Constant(int32_t value, RelocInfo::Mode rmode);
   Node* RelocatableInt64Constant(int64_t value, RelocInfo::Mode rmode);
   Node* RelocatableIntPtrConstant(intptr_t value, RelocInfo::Mode rmode);
 
   // Creates a Float32Constant node, usually canonicalized.
   Node* Float32Constant(float value);
 
   // Creates a Float64Constant node, usually canonicalized.
   Node* Float64Constant(double value);
 
+  // Creates a PointerConstant node (asm.js only).
+  Node* PointerConstant(intptr_t value);
+  template <typename T>
+  Node* PointerConstant(T* value) {
+    return PointerConstant(bit_cast<intptr_t>(value));
+  }
+
   // Creates an ExternalConstant node, usually canonicalized.
   Node* ExternalConstant(ExternalReference ref);
   Node* ExternalConstant(Runtime::FunctionId function_id);
 
   Node* SmiConstant(int32_t immediate) {
     DCHECK(Smi::IsValid(immediate));
     return Constant(immediate);
   }
 
   // Creates a dummy Constant node, used to satisfy calling conventions of
@@ skipping 58 matching lines @@
   Node* NumberConstant(double value);
 
   DISALLOW_COPY_AND_ASSIGN(JSGraph);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif