Convert ElementsKind into a BitField

src/x64/code-stubs-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "bootstrapper.h"
 #include "code-stubs.h"
@@ skipping 4877 matching lines @@
     __ Check(equal, kUnexpectedInitialMapForArrayFunction);
   }
 
   // Figure out the right elements kind
   __ movp(rcx, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
 
   // Load the map's "bit field 2" into |result|. We only need the first byte,
   // but the following masking takes care of that anyway.
   __ movzxbp(rcx, FieldOperand(rcx, Map::kBitField2Offset));
   // Retrieve elements_kind from bit field 2.
-  __ andp(rcx, Immediate(Map::kElementsKindMask));
-  __ shrp(rcx, Immediate(Map::kElementsKindShift));
+  __ DecodeField<Map::ElementsKindBits>(rcx);
 
   if (FLAG_debug_code) {
     Label done;
     __ cmpl(rcx, Immediate(FAST_ELEMENTS));
     __ j(equal, &done);
     __ cmpl(rcx, Immediate(FAST_HOLEY_ELEMENTS));
     __ Assert(equal,
               kInvalidElementsKindForInternalArrayOrInternalPackedArray);
     __ bind(&done);
   }
@@ skipping 185 matching lines @@
                               return_value_operand,
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64