Also fix cast warnings on Win64

src/x64/code-stubs-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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6243 matching lines @@
     // Check for the hole and skip.
     __ CompareRoot(entity_name, Heap::kTheHoleValueRootIndex);
     __ j(equal, &good, Label::kNear);
 
     // Check if the entry name is not a unique name.
     __ movq(entity_name, FieldOperand(entity_name, HeapObject::kMapOffset));
     __ testb(FieldOperand(entity_name, Map::kInstanceTypeOffset),
              Immediate(kIsInternalizedMask));
     __ j(not_zero, &good, Label::kNear);
     __ cmpb(FieldOperand(entity_name, Map::kInstanceTypeOffset),
-            Immediate(static_cast<int8_t>(SYMBOL_TYPE)));
+            Immediate(static_cast<uint8_t>(SYMBOL_TYPE)));
     __ j(not_equal, miss);
 
     __ bind(&good);
   }
 
   NameDictionaryLookupStub stub(properties, r0, r0, NEGATIVE_LOOKUP);
   __ Push(Handle<Object>(name));
   __ push(Immediate(name->Hash()));
   __ CallStub(&stub);
   __ testq(r0, r0);
@@ skipping 113 matching lines @@
       // lookup we have to bailout as this key might be equal to the
       // key we are looking for.
 
       // Check if the entry name is not a unique name.
       Label cont;
       __ movq(scratch, FieldOperand(scratch, HeapObject::kMapOffset));
       __ testb(FieldOperand(scratch, Map::kInstanceTypeOffset),
                Immediate(kIsInternalizedMask));
       __ j(not_zero, &cont);
       __ cmpb(FieldOperand(scratch, Map::kInstanceTypeOffset),
-              Immediate(static_cast<int8_t>(SYMBOL_TYPE)));
+              Immediate(static_cast<uint8_t>(SYMBOL_TYPE)));
       __ j(not_equal, &maybe_in_dictionary);
       __ bind(&cont);
     }
   }
 
   __ bind(&maybe_in_dictionary);
   // If we are doing negative lookup then probing failure should be
   // treated as a lookup success. For positive lookup probing failure
   // should be treated as lookup failure.
   if (mode_ == POSITIVE_LOOKUP) {
@@ skipping 472 matching lines @@
 #endif
 
   __ Ret();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64