Make it possible to assert that certain instance types are compatible wrt HAllocate.

src/hydrogen-instructions.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3474 matching lines @@
     // TODO(hpayer): This is a short-term hack to make allocation mementos
     // work again in new space.
     dominator_allocate->ClearNextMapWord(original_object_size);
   }
 #else
   // TODO(hpayer): This is a short-term hack to make allocation mementos
   // work again in new space.
   dominator_allocate->ClearNextMapWord(original_object_size);
 #endif
 
-  dominator_allocate->clear_next_map_word_ = clear_next_map_word_;
+  dominator_allocate->UpdateClearNextMapWord(MustClearNextMapWord());
 
   // After that replace the dominated allocate instruction.
   HInstruction* dominated_allocate_instr =
       HInnerAllocatedObject::New(zone,
                                  context(),
                                  dominator_allocate,
                                  dominator_size,
                                  type());
   dominated_allocate_instr->InsertBefore(this);
   DeleteAndReplaceWith(dominated_allocate_instr);
@@ skipping 115 matching lines @@
           Representation::Smi());
   HStoreNamedField* store_size = HStoreNamedField::New(zone, context(),
       free_space_instr, access, filler_size);
   store_size->SetFlag(HValue::kHasNoObservableSideEffects);
   store_size->InsertAfter(filler_size);
   filler_free_space_size_ = store_size;
 }
 
 
 void HAllocate::ClearNextMapWord(int offset) {
-  if (clear_next_map_word_) {
+  if (MustClearNextMapWord()) {
     Zone* zone = block()->zone();
     HObjectAccess access = HObjectAccess::ForJSObjectOffset(offset);
     HStoreNamedField* clear_next_map =
         HStoreNamedField::New(zone, context(), this, access,
             block()->graph()->GetConstantNull());
     clear_next_map->ClearAllSideEffects();
     clear_next_map->InsertAfter(this);
   }
 }
 
@@ skipping 780 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal