Simplify test for typeof x == 'Object' on all platforms.

src/x64/lithium-codegen-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3478 matching lines @@
              Immediate(1 << Map::kIsUndetectable));
     final_branch_condition = not_zero;
 
   } else if (type_name->Equals(Heap::function_symbol())) {
     __ JumpIfSmi(input, false_label);
     __ CmpObjectType(input, FIRST_FUNCTION_CLASS_TYPE, input);
     final_branch_condition = above_equal;
 
   } else if (type_name->Equals(Heap::object_symbol())) {
     __ JumpIfSmi(input, false_label);
-    __ Cmp(input, Factory::null_value());
+    __ CompareRoot(input, Heap::kNullValueRootIndex);
     __ j(equal, true_label);
+    __ CmpObjectType(input, FIRST_JS_OBJECT_TYPE, input);
+    __ j(below, false_label);
+    __ CmpInstanceType(input, FIRST_FUNCTION_CLASS_TYPE);
+    __ j(above_equal, false_label);
     // Check for undetectable objects => false.
     __ testb(FieldOperand(input, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
-    __ j(not_zero, false_label);
-    // Check for JS objects that are not RegExp or Function => true.
-    __ CmpInstanceType(input, FIRST_JS_OBJECT_TYPE);
-    __ j(below, false_label);
-    __ CmpInstanceType(input, FIRST_FUNCTION_CLASS_TYPE);
-    final_branch_condition = below_equal;
+    final_branch_condition = zero;
 
   } else {
     final_branch_condition = never;
     __ jmp(false_label);
   }
 
   return final_branch_condition;
 }
 
 
@@ skipping 116 matching lines @@
   RegisterEnvironmentForDeoptimization(environment);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64