Refactor type checks in v8natives.js and runtime.js....

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
===================================================================
--- src/x64/codegen-x64.cc	(revision 5085)
+++ src/x64/codegen-x64.cc	(working copy)
@@ -5723,6 +5723,25 @@
 }
 
 
+void CodeGenerator::GenerateIsSpecObject(ZoneList<Expression*>* args) {
+  // This generates a fast version of:
+  // (typeof(arg) === 'object' || %_ClassOf(arg) == 'RegExp' ||
+  // typeof(arg) == function).
+  // It includes undetectable objects (as opposed to IsObject).
+  ASSERT(args->length() == 1);
+  Load(args->at(0));
+  Result value = frame_->Pop();
+  value.ToRegister();
+  ASSERT(value.is_valid());
+  Condition is_smi = masm_->CheckSmi(value.reg());
+  destination()->false_target()->Branch(is_smi);
+  // Check that this is an object.
+  __ CmpObjectType(value.reg(), FIRST_JS_OBJECT_TYPE, kScratchRegister);
+  value.Unuse();
+  destination()->Split(above_equal);
+}
+
+
 void CodeGenerator::GenerateIsFunction(ZoneList<Expression*>* args) {
   // This generates a fast version of:
   // (%_ClassOf(arg) === 'Function')