[RuntimeDyld] DenseMap -> std::unordered_map

[loladiro]

Summary

DenseMap is most applicable when both keys and values are small. In this case, the value violates that assumption, causing quite significant memory overhead. A std::map is more appropriate in this case (or at least fixed the memory problems I was seeing).

[dblaikie]

Any preference of map over unordered_map

[loladiro]

I don't think it should matter. Will try it out.

[loladiro]

Tested with unordered_map. Seems marginally better in my tests, but probably not statistically significant given my methodology. Still there's no reason the map should be ordered, so might as well use an unordered_map.

[lhames]

LGTM. Thanks Keno. :)

lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp

     // The Section here (Sections[i]) refers to the section in which the
     // symbol for the relocation is located.  The SectionID in the relocation
     // entry provides the section to which the relocation will be applied.
-    int Idx = it->getFirst();
+    int Idx = it->first;
     uint64_t Addr = Sections[Idx].LoadAddress;
     DEBUG(dbgs() << "Resolving relocations Section #" << Idx << "\t"
                  << format("%p", (uintptr_t)Addr) << "\n");
-    resolveRelocationList(it->getSecond(), Addr);
+    resolveRelocationList(it->second, Addr);
   }
   Relocations.clear();
 

lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h

   // Relocations to sections already loaded. Indexed by SectionID which is the
   // source of the address. The target where the address will be written is
   // SectionID/Offset in the relocation itself.
-  DenseMap<unsigned, RelocationList> Relocations;
+  std::map<unsigned, RelocationList> Relocations;
 
   // Relocations to external symbols that are not yet resolved.  Symbols are
   // external when they aren't found in the global symbol table of all loaded