Factor out handling of mixed objects preprocessing after migration

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 700ae041cea4708833a419ec159145b042dd7ef2..3ff5e4402bd6f76cfd5b9260a67c214d579725be 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1529,20 +1529,36 @@ int HeapObject::Size() {
 }
 
 
-bool HeapObject::MayContainRawValues() {
+HeapObjectContents HeapObject::ContentType() {
   InstanceType type = map()->instance_type();
   if (type <= LAST_NAME_TYPE) {
     if (type == SYMBOL_TYPE) {
-      return false;
+      return HeapObjectContents::kTaggedValues;
     }
     DCHECK(type < FIRST_NONSTRING_TYPE);
     // There are four string representations: sequential strings, external
     // strings, cons strings, and sliced strings.
     // Only the former two contain raw values and no heap pointers (besides the
     // map-word).
-    return ((type & kIsIndirectStringMask) != kIsIndirectStringTag);
+    if (((type & kIsIndirectStringMask) != kIsIndirectStringTag))
+      return HeapObjectContents::kRawValues;
+    else
+      return HeapObjectContents::kTaggedValues;
+#if 0
+  // TODO(jochen): Enable eventually.
+  } else if (type == JS_FUNCTION_TYPE) {
+    return HeapObjectContents::kMixedValues;
+#endif
+  } else if (type <= LAST_DATA_TYPE) {
+    // TODO(jochen): Why do we claim that Code and Map contain only raw values?

[Igor Sheludko, 2015/06/08 10:45:12]

I guess because we never called MayContainRawValues() method for Code and Map
object before, but now we do during the slots filtering. So probably it makes
sense to return kTaggedValues for Code and Map here.

I'm not sure which way is the best: to reorder instance types or to add more
conditions here.

[jochen (gone - plz use gerrit), 2015/06/08 11:04:58]

I'd rather keep this patch as refactoring only, we can still do that in a
follow-up.

At least Code should be kMixedValues, no? It contains all the assembly...

+    return HeapObjectContents::kRawValues;
+  } else {
+#if V8_DOUBLE_FIELDS_UNBOXING

[Igor Sheludko, 2015/06/08 10:45:12]

I think it is better to use "if (FLAG_unbox_double_fields)" instead of
#if/#endif.

+    LayoutDescriptorHelper helper(map());
+    if (!helper.all_fields_tagged()) return HeapObjectContents::kMixedValues;
+#endif
+    return HeapObjectContents::kTaggedValues;
   }
-  return (type <= LAST_DATA_TYPE);
 }