With >= 64 non-string instance types, I removed an optimization

src/x64/macro-assembler-x64.cc

 // 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
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@@ skipping 2298 matching lines @@
        Immediate(kFlatAsciiStringTag + (kFlatAsciiStringTag << 3)));
   j(not_equal, on_fail, near_jump);
 }
 
 
 template<class T>
 static void JumpIfNotUniqueNameHelper(MacroAssembler* masm,
                                       T operand_or_register,
                                       Label* not_unique_name,
                                       Label::Distance distance) {
-  STATIC_ASSERT(((SYMBOL_TYPE - 1) & kIsInternalizedMask) == kInternalizedTag);
-  masm->cmpb(operand_or_register, Immediate(kInternalizedTag));
-  masm->j(less, not_unique_name, distance);
-  masm->cmpb(operand_or_register, Immediate(SYMBOL_TYPE));
-  masm->j(greater, not_unique_name, distance);
+  STATIC_ASSERT(kInternalizedTag == 0 && kStringTag == 0);
+  Label succeed;
+  masm->testb(operand_or_register,
+              Immediate(kIsNotStringMask | kIsNotInternalizedMask));
+  masm->j(zero, &succeed, Label::kNear);
+  masm->cmpb(operand_or_register, Immediate(static_cast<uint8_t>(SYMBOL_TYPE)));
+  masm->j(not_equal, not_unique_name, distance);
+
+  masm->bind(&succeed);
 }
 
 
 void MacroAssembler::JumpIfNotUniqueName(Operand operand,
                                          Label* not_unique_name,
                                          Label::Distance distance) {
   JumpIfNotUniqueNameHelper<Operand>(this, operand, not_unique_name, distance);
 }
 
 
@@ skipping 2352 matching lines @@
   j(greater, &no_info_available);
   CompareRoot(MemOperand(scratch_reg, -AllocationSiteInfo::kSize),
               Heap::kAllocationSiteInfoMapRootIndex);
   bind(&no_info_available);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64