Sharing of descriptor arrays.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 5268fe2a2e961c1069c38380bb60e6f86f659585..89b7962231c7f99edfb38ce8b398476dd9ec0131 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -949,13 +949,15 @@ class MacroAssembler: public Assembler {
 
   void LoadInstanceDescriptors(Register map, Register descriptors);
   void EnumLength(Register dst, Register map);
+  void NumberOfOwnDescriptors(Register dst, Register map);
 
   template<typename Field>
   void DecodeField(Register reg) {
-    static const int full_shift = Field::kShift + kSmiShift;
-    static const int low_mask = Field::kMask >> Field::kShift;
-    shr(reg, Immediate(full_shift));
-    and_(reg, Immediate(low_mask));
+    static const int shift = Field::kShift + kSmiShift;
+    static const int mask = Field::kMask >> Field::kShift;
+    shr(reg, Immediate(shift));
+    and_(reg, Immediate(mask));
+    shl(reg, Immediate(kSmiShift));
   }
 
   // Abort execution if argument is not a number. Used in debug code.