Always require exact maps.

src/x64/macro-assembler-x64.h

 // Copyright 2012 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 874 matching lines @@
                                    XMMRegister xmm_scratch,
                                    Label* fail,
                                    int elements_offset = 0);
 
   // Compare an object's map with the specified map and its transitioned
   // elements maps if mode is ALLOW_ELEMENT_TRANSITION_MAPS. FLAGS are set with
   // result of map compare. If multiple map compares are required, the compare
   // sequences branches to early_success.
   void CompareMap(Register obj,
                   Handle<Map> map,
-                  Label* early_success,
-                  CompareMapMode mode = REQUIRE_EXACT_MAP);
+                  Label* early_success);
 
   // Check if the map of an object is equal to a specified map and branch to
   // label if not. Skip the smi check if not required (object is known to be a
   // heap object). If mode is ALLOW_ELEMENT_TRANSITION_MAPS, then also match
   // against maps that are ElementsKind transition maps of the specified map.
   void CheckMap(Register obj,
                 Handle<Map> map,
                 Label* fail,
-                SmiCheckType smi_check_type,
-                CompareMapMode mode = REQUIRE_EXACT_MAP);
+                SmiCheckType smi_check_type);
 
   // Check if the map of an object is equal to a specified map and branch to a
   // specified target if equal. Skip the smi check if not required (object is
   // known to be a heap object)
   void DispatchMap(Register obj,
                    Register unused,
                    Handle<Map> map,
                    Handle<Code> success,
                    SmiCheckType smi_check_type);
 
@@ skipping 593 matching lines @@
     masm->popfq();                                                           \
   }                                                                          \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_