diff --git a/src/assembler.h b/src/assembler.h
index 4ef61e4..b089b09 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -181,11 +181,10 @@
   enum Mode {
     // Please note the order is important (see IsCodeTarget, IsGCRelocMode).
     CONSTRUCT_CALL,  // code target that is a call to a JavaScript constructor.
-    CODE_TARGET_CONTEXT,  // Code target used for contextual loads.
+    CODE_TARGET_CONTEXT,  // Code target used for contextual loads and stores.
     DEBUG_BREAK,  // Code target for the debugger statement.
     CODE_TARGET,  // Code target which is not any of the above.
     EMBEDDED_OBJECT,
-
     GLOBAL_PROPERTY_CELL,
 
     // Everything after runtime_entry (inclusive) is not GC'ed.
@@ -203,7 +202,7 @@
     NUMBER_OF_MODES,  // must be no greater than 14 - see RelocInfoWriter
     NONE,  // never recorded
     LAST_CODE_ENUM = CODE_TARGET,
-    LAST_GCED_ENUM = EMBEDDED_OBJECT
+    LAST_GCED_ENUM = GLOBAL_PROPERTY_CELL
   };
 
 
@@ -460,9 +459,6 @@
 #endif
 
 
-typedef void* ExternalReferenceRedirector(void* original, bool fp_return);
-
-
 // An ExternalReference represents a C++ address used in the generated
 // code. All references to C++ functions and variables must be encapsulated in
 // an ExternalReference instance. This is done in order to track the origin of
@@ -470,9 +466,29 @@
 // addresses when deserializing a heap.
 class ExternalReference BASE_EMBEDDED {
  public:
+  // Used in the simulator to support different native api calls.
+  //
+  // BUILTIN_CALL - builtin call.
+  // MaybeObject* f(v8::internal::Arguments).
+  //
+  // FP_RETURN_CALL - builtin call that returns floating point.
+  // double f(double, double).
+  //
+  // DIRECT_CALL - direct call to API function native callback
+  // from generated code.
+  // Handle<Value> f(v8::Arguments&)
+  //
+  enum Type {
+    BUILTIN_CALL,  // default
+    FP_RETURN_CALL,
+    DIRECT_CALL
+  };
+
+  typedef void* ExternalReferenceRedirector(void* original, Type type);
+
   explicit ExternalReference(Builtins::CFunctionId id);
 
-  explicit ExternalReference(ApiFunction* ptr);
+  explicit ExternalReference(ApiFunction* ptr, Type type);
 
   explicit ExternalReference(Builtins::Name name);
 
@@ -600,17 +616,19 @@
 
   static ExternalReferenceRedirector* redirector_;
 
-  static void* Redirect(void* address, bool fp_return = false) {
+  static void* Redirect(void* address,
+                        Type type = ExternalReference::BUILTIN_CALL) {
     if (redirector_ == NULL) return address;
-    void* answer = (*redirector_)(address, fp_return);
+    void* answer = (*redirector_)(address, type);
     return answer;
   }
 
-  static void* Redirect(Address address_arg, bool fp_return = false) {
+  static void* Redirect(Address address_arg,
+                        Type type = ExternalReference::BUILTIN_CALL) {
     void* address = reinterpret_cast<void*>(address_arg);
     void* answer = (redirector_ == NULL) ?
                    address :
-                   (*redirector_)(address, fp_return);
+                   (*redirector_)(address, type);
     return answer;
   }