[generators] Create the fixed array holding the registers only once.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 12dd06e6ef1998bdcc7fe24667cd20439a6b1fe8..26ec78535a1e7e6a062922a68235ec29f964231e 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1009,7 +1009,8 @@ template <class C> inline bool Is(Object* obj);
   V(True)               \
   V(False)              \
   V(ArgumentsMarker)    \
-  V(OptimizedOut)
+  V(OptimizedOut)       \
+  V(Placeholder)

[Benedikt Meurer, 2016/04/27 17:46:02]

Can we call this guy EmptyRegister or StaleRegister or something like that?
Placeholder is not very specific.

 
 // The element types selection for CreateListFromArrayLike.
 enum class ElementTypes { kAll, kStringAndSymbol };
@@ -9492,6 +9493,7 @@ class Oddball: public HeapObject {
   static const byte kOther = 7;
   static const byte kException = 8;
   static const byte kOptimizedOut = 9;
+  static const byte kPlaceholder = 10;
 
   typedef FixedBodyDescriptor<kToStringOffset, kTypeOfOffset + kPointerSize,
                               kSize> BodyDescriptor;