Try using stack

runtime/src/main/cpp/Memory.cpp

@@ -451,9 +451,8 @@ struct MemoryState {
   uint64_t allocSinceLastGcThreshold;
 #endif // USE_GC
 
-  // This map is expected to be small, std::map consumes less memory than
-  // std::unordered_map and is just as efficient.
-  KStdOrderedMap<ObjHeader**, ObjHeader*> initializingSingletons;
+  // A stack of initializing singletons.
+  KStdVector<std::pair<ObjHeader**, ObjHeader*>> initializingSingletons;
 
 #if COLLECT_STATISTIC
   #define CONTAINER_ALLOC_STAT(state, size, container) state->statistic.incAlloc(size, container);
@@ -2029,9 +2028,11 @@ OBJ_GETTER(initSharedInstance,
   }
 #endif  // KONAN_NO_EXCEPTIONS
 #else  // KONAN_NO_THREADS
-  auto it = memoryState->initializingSingletons.find(location);
-  if (it != memoryState->initializingSingletons.end()) {
-    RETURN_OBJ(it->second);
+  // Search from the top of the stack.
+  for (auto it = memoryState->initializingSingletons.rbegin(); it != memoryState->initializingSingletons.rend(); ++it) {
+    if (it->first == location) {
+      RETURN_OBJ(it->second);
+    }
   }
 
   ObjHeader* initializing = reinterpret_cast<ObjHeader*>(1);
@@ -2044,8 +2045,7 @@ OBJ_GETTER(initSharedInstance,
     RETURN_OBJ(value);
   }
   ObjHeader* object = AllocInstance(typeInfo, OBJ_RESULT);
-  auto insertIt = memoryState->initializingSingletons.insert({location, object});
-  RuntimeCheck(insertIt.second, "object cannot be assigned twice into initializingSingletons");
+  memoryState->initializingSingletons.push_back(std::make_pair(location, object));
   addHeapRef(object);
 #if KONAN_NO_EXCEPTIONS
   ctor(object);
@@ -2053,7 +2053,7 @@ OBJ_GETTER(initSharedInstance,
     FreezeSubgraph(object);
   UpdateHeapRef(location, object);
   synchronize();
-  memoryState->initializingSingletons.erase(location);
+  memoryState->initializingSingletons.pop_back();
   releaseHeapRef<Strict>(object);
   return object;
 #else  // KONAN_NO_EXCEPTIONS
@@ -2063,13 +2063,13 @@ OBJ_GETTER(initSharedInstance,
       FreezeSubgraph(object);
     UpdateHeapRef(location, object);
     synchronize();
-    memoryState->initializingSingletons.erase(location);
+    memoryState->initializingSingletons.pop_back();
     releaseHeapRef<Strict>(object);
     return object;
   } catch (...) {
     UpdateReturnRef(OBJ_RESULT, nullptr);
     zeroHeapRef(location);
-    memoryState->initializingSingletons.erase(location);
+    memoryState->initializingSingletons.pop_back();
     releaseHeapRef<Strict>(object);
     synchronize();
     throw;