Factor out handling of mixed objects preprocessing after migration

src/objects.h

 // Copyright 2012 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 1381 matching lines @@
  private:
   // HeapObject calls the private constructor and directly reads the value.
   friend class HeapObject;
 
   explicit MapWord(uintptr_t value) : value_(value) {}
 
   uintptr_t value_;
 };
 
 
+// The content of an heap object (except for the map pointer). kTaggedValues
+// objects can contain both heap pointers and Smis, kMixedValues can contain
+// heap pointers, Smis, and raw values (e.g. doubles or strings), and kRawValues
+// objects can contain raw values and Smis.
+enum class HeapObjectContents { kTaggedValues, kMixedValues, kRawValues };
+
+
 // HeapObject is the superclass for all classes describing heap allocated
 // objects.
 class HeapObject: public Object {
  public:
   // [map]: Contains a map which contains the object's reflective
   // information.
   inline Map* map() const;
   inline void set_map(Map* value);
   // The no-write-barrier version.  This is OK if the object is white and in
   // new space, or if the value is an immortal immutable object, like the maps
@@ skipping 31 matching lines @@
 
   // Iterates over all pointers contained in the object except the
   // first map pointer.  The object type is given in the first
   // parameter. This function does not access the map pointer in the
   // object, and so is safe to call while the map pointer is modified.
   void IterateBody(InstanceType type, int object_size, ObjectVisitor* v);
 
   // Returns the heap object's size in bytes
   inline int Size();
 
-  // Returns true if this heap object may contain raw values, i.e., values that
-  // look like pointers to heap objects.
-  inline bool MayContainRawValues();
+  // Indicates what type of values this heap object may contain.
+  inline HeapObjectContents ContentType();
 
   // Given a heap object's map pointer, returns the heap size in bytes
   // Useful when the map pointer field is used for other purposes.
   // GC internal.
   inline int SizeFromMap(Map* map);
 
   // Returns the field at offset in obj, as a read/write Object* reference.
   // Does no checking, and is safe to use during GC, while maps are invalid.
   // Does not invoke write barrier, so should only be assigned to
   // during marking GC.
@@ skipping 9407 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_