diff --git a/kotlin-native/runtime/src/legacymm/cpp/Memory.cpp b/kotlin-native/runtime/src/legacymm/cpp/Memory.cpp
index e46ef5aad73..54e7f287e7e 100644
--- a/kotlin-native/runtime/src/legacymm/cpp/Memory.cpp
+++ b/kotlin-native/runtime/src/legacymm/cpp/Memory.cpp
@@ -73,6 +73,10 @@
 
 namespace {
 
+ALWAYS_INLINE bool IsStrictMemoryModel() noexcept {
+    return CurrentMemoryModel == MemoryModel::kStrict;
+}
+
 typedef uint32_t container_size_t;
 
 // Granularity of arena container chunks.
@@ -1026,7 +1030,7 @@ inline void unlock(KInt* spinlock) {
 }
 
 inline bool canFreeze(ContainerHeader* container) {
-  if (IsStrictMemoryModel)
+  if (IsStrictMemoryModel())
     // In strict memory model we ignore permanent, frozen and shared object when recursively freezing.
     return container != nullptr && !container->shareable();
   else
@@ -1393,14 +1397,14 @@ inline void decrementRC(ContainerHeader* container) {
 
 inline void decrementRC(ContainerHeader* container) {
   auto* state = memoryState;
-  RuntimeAssert(!IsStrictMemoryModel || state->gcInProgress, "Must only be called during GC");
+  RuntimeAssert(!IsStrictMemoryModel() || state->gcInProgress, "Must only be called during GC");
   // TODO: enable me, once account for inner references in frozen objects correctly.
   // RuntimeAssert(container->refCount() > 0, "Must be positive");
   bool useCycleCollector = container->local();
   if (container->decRefCount() == 0) {
     freeContainer(container);
   } else if (useCycleCollector && state->toFree != nullptr) {
-      RuntimeAssert(IsStrictMemoryModel, "No cycle collector in relaxed mode yet");
+      RuntimeAssert(IsStrictMemoryModel(), "No cycle collector in relaxed mode yet");
       RuntimeAssert(container->refCount() > 0, "Must be positive");
       RuntimeAssert(!container->shareable(), "Cycle collector shalln't be used with shared objects yet");
       RuntimeAssert(container->objectCount() == 1, "cycle collector shall only work with single object containers");
@@ -1819,7 +1823,7 @@ void incrementStack(MemoryState* state) {
 }
 
 void processDecrements(MemoryState* state) {
-  RuntimeAssert(IsStrictMemoryModel, "Only works in strict model now");
+  RuntimeAssert(IsStrictMemoryModel(), "Only works in strict model now");
   auto* toRelease = state->toRelease;
   state->gcSuspendCount++;
   while (toRelease->size() > 0) {
@@ -1840,7 +1844,7 @@ void processDecrements(MemoryState* state) {
 }
 
 void decrementStack(MemoryState* state) {
-  RuntimeAssert(IsStrictMemoryModel, "Only works in strict model now");
+  RuntimeAssert(IsStrictMemoryModel(), "Only works in strict model now");
   state->gcSuspendCount++;
   FrameOverlay* frame = currentFrame;
   while (frame != nullptr) {
@@ -1868,7 +1872,7 @@ void garbageCollect(MemoryState* state, bool force) {
 #endif  // TRACE_GC
   state->allocSinceLastGc = 0;
 
-  if (!IsStrictMemoryModel) {
+  if (!IsStrictMemoryModel()) {
     // In relaxed model we just process finalizer queue and be done with it.
     processFinalizerQueue(state);
     return;
@@ -1988,7 +1992,7 @@ void garbageCollect() {
 #endif  // USE_GC
 
 ForeignRefManager* initLocalForeignRef(ObjHeader* object) {
-  if (!IsStrictMemoryModel) return nullptr;
+  if (!IsStrictMemoryModel()) return nullptr;
 
   return memoryState->foreignRefManager;
 }
@@ -1996,7 +2000,7 @@ ForeignRefManager* initLocalForeignRef(ObjHeader* object) {
 ForeignRefManager* initForeignRef(ObjHeader* object) {
   addHeapRef(object);
 
-  if (!IsStrictMemoryModel) return nullptr;
+  if (!IsStrictMemoryModel()) return nullptr;
 
   // Note: it is possible to return nullptr for shared object as an optimization,
   // but this will force the implementation to release objects on uninitialized threads
@@ -2007,7 +2011,7 @@ ForeignRefManager* initForeignRef(ObjHeader* object) {
 }
 
 bool isForeignRefAccessible(ObjHeader* object, ForeignRefManager* manager) {
-  if (!IsStrictMemoryModel) return true;
+  if (!IsStrictMemoryModel()) return true;
 
   if (manager == memoryState->foreignRefManager) {
     // Note: it is important that this code neither crashes nor returns false-negative result
@@ -2021,7 +2025,7 @@ bool isForeignRefAccessible(ObjHeader* object, ForeignRefManager* manager) {
 }
 
 void deinitForeignRef(ObjHeader* object, ForeignRefManager* manager) {
-  if (IsStrictMemoryModel) {
+  if (IsStrictMemoryModel()) {
     if (memoryState != nullptr && isForeignRefAccessible(object, manager)) {
       releaseHeapRef<true>(object);
     } else {
@@ -2127,13 +2131,13 @@ void deinitMemory(MemoryState* memoryState, bool destroyRuntime) {
   atomicAdd(&pendingDeinit, -1);
 
 #if TRACE_MEMORY
-  if (IsStrictMemoryModel && destroyRuntime && allocCount > 0) {
+  if (IsStrictMemoryModel() && destroyRuntime && allocCount > 0) {
     MEMORY_LOG("*** Memory leaks, leaked %d containers ***\n", allocCount);
     dumpReachable("", memoryState->containers);
   }
 #else
 #if USE_GC
-  if (IsStrictMemoryModel && allocCount > 0 && checkLeaks) {
+  if (IsStrictMemoryModel() && allocCount > 0 && checkLeaks) {
     konan::consoleErrorf(
         "Memory leaks detected, %d objects leaked!\n"
         "Use `Platform.isMemoryLeakCheckerActive = false` to avoid this check.\n", allocCount);
@@ -2441,7 +2445,7 @@ OBJ_GETTER(swapHeapRefLocked,
   lock(spinlock);
   ObjHeader* oldValue = *location;
   bool shallRemember = false;
-  if (IsStrictMemoryModel) {
+  if (IsStrictMemoryModel()) {
     auto realCookie = computeCookie();
     shallRemember = *cookie != realCookie;
     if (shallRemember) *cookie = realCookie;
@@ -2455,7 +2459,7 @@ OBJ_GETTER(swapHeapRefLocked,
   }
   UpdateReturnRef(OBJ_RESULT, oldValue);
 
-  if (IsStrictMemoryModel && shallRemember && oldValue != nullptr && oldValue != expectedValue) {
+  if (IsStrictMemoryModel() && shallRemember && oldValue != nullptr && oldValue != expectedValue) {
     // Only remember container if it is not known to this thread (i.e. != expectedValue).
     rememberNewContainer(containerFor(oldValue));
   }
@@ -2491,7 +2495,7 @@ OBJ_GETTER(readHeapRefLocked, ObjHeader** location, int32_t* spinlock, int32_t*
   if (shallRemember) *cookie = realCookie;
   UpdateReturnRef(OBJ_RESULT, value);
 #if USE_GC
-  if (IsStrictMemoryModel && shallRemember && value != nullptr) {
+  if (IsStrictMemoryModel() && shallRemember && value != nullptr) {
     auto* container = containerFor(value);
     rememberNewContainer(container);
   }
@@ -2506,7 +2510,7 @@ OBJ_GETTER(readHeapRefNoLock, ObjHeader* object, KInt index) {
     reinterpret_cast<uintptr_t>(object) + object->type_info()->objOffsets_[index]);
   ObjHeader* value = *location;
 #if USE_GC
-  if (IsStrictMemoryModel && (value != nullptr)) {
+  if (IsStrictMemoryModel() && (value != nullptr)) {
     // Maybe not so good to do that under lock.
     rememberNewContainer(containerFor(value));
   }
@@ -3300,7 +3304,7 @@ bool IsForeignRefAccessible(ObjHeader* object, ForeignRefContext context) {
 
 void AdoptReferenceFromSharedVariable(ObjHeader* object) {
 #if USE_GC
-  if (IsStrictMemoryModel && object != nullptr && isShareable(containerFor(object)))
+  if (IsStrictMemoryModel() && object != nullptr && isShareable(containerFor(object)))
     rememberNewContainer(containerFor(object));
 #endif  // USE_GC
 }
diff --git a/kotlin-native/runtime/src/main/cpp/KAssert.h b/kotlin-native/runtime/src/main/cpp/KAssert.h
index c111c1783fa..aa8edac245b 100644
--- a/kotlin-native/runtime/src/main/cpp/KAssert.h
+++ b/kotlin-native/runtime/src/main/cpp/KAssert.h
@@ -27,6 +27,19 @@
 
 RUNTIME_NORETURN void RuntimeAssertFailed(const char* location, const char* message);
 
+namespace internal {
+
+inline RUNTIME_NORETURN void TODOImpl(const char* location) {
+    RuntimeAssertFailed(location, "Unimplemented");
+}
+
+// TODO: Support format string when `RuntimeAssertFailed` supports it.
+inline RUNTIME_NORETURN void TODOImpl(const char* location, const char* message) {
+    RuntimeAssertFailed(location, message);
+}
+
+} // namespace internal
+
 // During codegeneration we set this constant to 1 or 0 to allow bitcode optimizer
 // to get rid of code behind condition.
 extern "C" const int KonanNeedDebugInfo;
@@ -48,4 +61,9 @@ if (KonanNeedDebugInfo && (!(condition))) {                         \
     RuntimeAssertFailed(nullptr, message); \
   }
 
+#define TODO(...) \
+    do { \
+        ::internal::TODOImpl(__FILE__ ":" TOSTRING(__LINE__), ##__VA_ARGS__); \
+    } while (false)
+
 #endif // RUNTIME_ASSERT_H
diff --git a/kotlin-native/runtime/src/main/cpp/KAssertTest.cpp b/kotlin-native/runtime/src/main/cpp/KAssertTest.cpp
new file mode 100644
index 00000000000..4460db8515a
--- /dev/null
+++ b/kotlin-native/runtime/src/main/cpp/KAssertTest.cpp
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+#include "KAssert.h"
+
+#include "gtest/gtest.h"
+
+TEST(TODODeathTest, EmptyTODO) {
+    EXPECT_DEATH({
+        TODO();
+    }, "KAssertTest.cpp:12: runtime assert: Unimplemented");
+}
+
+TEST(TODODeathTest, TODOWithMessage) {
+    EXPECT_DEATH({
+        TODO("Nope");
+    }, "KAssertTest.cpp:18: runtime assert: Nope");
+}
diff --git a/kotlin-native/runtime/src/main/cpp/Memory.h b/kotlin-native/runtime/src/main/cpp/Memory.h
index 82c58fde4b6..94b7a94b85d 100644
--- a/kotlin-native/runtime/src/main/cpp/Memory.h
+++ b/kotlin-native/runtime/src/main/cpp/Memory.h
@@ -173,8 +173,15 @@ void InitAndRegisterGlobal(ObjHeader** location, const ObjHeader* initialValue)
 //    in intermediate frames when throwing
 //
 
+// NOTE: Must match `MemoryModel` in `Platform.kt`
+enum class MemoryModel {
+    kStrict = 0,
+    kRelaxed = 1,
+    kExperimental = 2,
+};
+
 // Controls the current memory model, is compile-time constant.
-extern const bool IsStrictMemoryModel;
+extern const MemoryModel CurrentMemoryModel;
 
 // Sets stack location.
 void SetStackRef(ObjHeader** location, const ObjHeader* object) RUNTIME_NOTHROW;
diff --git a/kotlin-native/runtime/src/main/cpp/Runtime.cpp b/kotlin-native/runtime/src/main/cpp/Runtime.cpp
index faa29a629de..88ebcdf8e60 100644
--- a/kotlin-native/runtime/src/main/cpp/Runtime.cpp
+++ b/kotlin-native/runtime/src/main/cpp/Runtime.cpp
@@ -314,7 +314,7 @@ KInt Konan_Platform_getCpuArchitecture() {
 }
 
 KInt Konan_Platform_getMemoryModel() {
-  return IsStrictMemoryModel ? 0 : 1;
+    return static_cast<KInt>(CurrentMemoryModel);
 }
 
 KBoolean Konan_Platform_isDebugBinary() {
diff --git a/kotlin-native/runtime/src/main/kotlin/kotlin/native/Platform.kt b/kotlin-native/runtime/src/main/kotlin/kotlin/native/Platform.kt
index 6ca425e88fa..39da7b97961 100644
--- a/kotlin-native/runtime/src/main/kotlin/kotlin/native/Platform.kt
+++ b/kotlin-native/runtime/src/main/kotlin/kotlin/native/Platform.kt
@@ -36,9 +36,11 @@ public enum class CpuArchitecture(val bitness: Int) {
 /**
  * Memory model.
  */
+// NOTE: Must match `MemoryModel` in `Memory.h`
 public enum class MemoryModel {
     STRICT,
-    RELAXED
+    RELAXED,
+    EXPERIMENTAL,
 }
 
 /**
diff --git a/kotlin-native/runtime/src/mm/cpp/Memory.cpp b/kotlin-native/runtime/src/mm/cpp/Memory.cpp
index ba9ab725eeb..184736dc66d 100644
--- a/kotlin-native/runtime/src/mm/cpp/Memory.cpp
+++ b/kotlin-native/runtime/src/mm/cpp/Memory.cpp
@@ -6,6 +6,8 @@
 #include "Memory.h"
 
 #include "GlobalsRegistry.hpp"
+#include "KAssert.h"
+#include "Porting.h"
 #include "StableRefRegistry.hpp"
 #include "ThreadData.hpp"
 #include "ThreadRegistry.hpp"
@@ -55,6 +57,11 @@ ALWAYS_INLINE mm::ThreadData* GetThreadData(MemoryState* state) {
 
 } // namespace
 
+ALWAYS_INLINE bool isShareable(const ObjHeader* obj) {
+    // TODO: Remove when legacy MM is gone.
+    return true;
+}
+
 extern "C" MemoryState* InitMemory(bool firstRuntime) {
     return ToMemoryState(mm::ThreadRegistry::Instance().RegisterCurrentThread());
 }
@@ -63,21 +70,27 @@ extern "C" void DeinitMemory(MemoryState* state, bool destroyRuntime) {
     mm::ThreadRegistry::Instance().Unregister(FromMemoryState(state));
 }
 
+extern "C" void RestoreMemory(MemoryState*) {
+    // TODO: Remove when legacy MM is gone.
+}
+
 extern "C" OBJ_GETTER(InitSingleton, ObjHeader** location, const TypeInfo* typeInfo, void (*ctor)(ObjHeader*)) {
     auto* threadData = mm::ThreadRegistry::Instance().CurrentThreadData();
     // TODO: This should only be called if singleton is actually created here. It's possible that the
     // singleton will be created on a different thread and here we should check that, instead of creating
     // another one (and registering `location` twice).
     mm::GlobalsRegistry::Instance().RegisterStorageForGlobal(threadData, location);
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 extern "C" RUNTIME_NOTHROW void InitAndRegisterGlobal(ObjHeader** location, const ObjHeader* initialValue) {
     auto* threadData = mm::ThreadRegistry::Instance().CurrentThreadData();
     mm::GlobalsRegistry::Instance().RegisterStorageForGlobal(threadData, location);
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
+extern "C" const MemoryModel CurrentMemoryModel = MemoryModel::kExperimental;
+
 extern "C" RUNTIME_NOTHROW void AddTLSRecord(MemoryState* memory, void** key, int size) {
     GetThreadData(memory)->tls().AddRecord(key, size);
 }
@@ -94,6 +107,31 @@ extern "C" RUNTIME_NOTHROW ObjHeader** LookupTLS(void** key, int index) {
     return mm::ThreadRegistry::Instance().CurrentThreadData()->tls().Lookup(key, index);
 }
 
+extern "C" RUNTIME_NOTHROW void GC_RegisterWorker(void* worker) {
+    // TODO: Remove when legacy MM is gone.
+    // Nothing to do
+}
+
+extern "C" RUNTIME_NOTHROW void GC_UnregisterWorker(void* worker) {
+    // TODO: Remove when legacy MM is gone.
+    // Nothing to do
+}
+
+extern "C" RUNTIME_NOTHROW void GC_CollectorCallback(void* worker) {
+    // TODO: Remove when legacy MM is gone.
+    // Nothing to do
+}
+
+extern "C" bool Kotlin_Any_isShareable(ObjHeader* thiz) {
+    // TODO: Remove when legacy MM is gone.
+    return true;
+}
+
+extern "C" RUNTIME_NOTHROW bool ClearSubgraphReferences(ObjHeader* root, bool checked) {
+    // TODO: Remove when legacy MM is gone.
+    return true;
+}
+
 extern "C" RUNTIME_NOTHROW void* CreateStablePointer(ObjHeader* object) {
     auto* threadData = mm::ThreadRegistry::Instance().CurrentThreadData();
     return mm::StableRefRegistry::Instance().RegisterStableRef(threadData, object);
@@ -120,6 +158,14 @@ extern "C" RUNTIME_NOTHROW OBJ_GETTER(AdoptStablePointer, void* pointer) {
     return object;
 }
 
+extern "C" RUNTIME_NOTHROW void CheckLifetimesConstraint(ObjHeader* obj, ObjHeader* pointee) {
+    if (!obj->local() && pointee != nullptr && pointee->local()) {
+        konan::consolePrintf("Attempt to store a stack object %p into a heap object %p\n", pointee, obj);
+        konan::consolePrintf("This is a compiler bug, please report it to https://kotl.in/issue\n");
+        konan::abort();
+    }
+}
+
 extern "C" ForeignRefContext InitForeignRef(ObjHeader* object) {
     auto* threadData = mm::ThreadRegistry::Instance().CurrentThreadData();
     auto* node = mm::StableRefRegistry::Instance().RegisterStableRef(threadData, object);
@@ -142,3 +188,8 @@ extern "C" void AdoptReferenceFromSharedVariable(ObjHeader* object) {
     // TODO: Remove when legacy MM is gone.
     // Nothing to do.
 }
+
+void CheckGlobalsAccessible() {
+    // TODO: Remove when legacy MM is gone.
+    // Always accessible
+}
diff --git a/kotlin-native/runtime/src/mm/cpp/Stubs.cpp b/kotlin-native/runtime/src/mm/cpp/Stubs.cpp
index 5b67ff9f063..bc79217b2cd 100644
--- a/kotlin-native/runtime/src/mm/cpp/Stubs.cpp
+++ b/kotlin-native/runtime/src/mm/cpp/Stubs.cpp
@@ -5,181 +5,145 @@
 
 #include "Memory.h"
 
+#include "KAssert.h"
+
 ALWAYS_INLINE bool isFrozen(const ObjHeader* obj) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 ALWAYS_INLINE bool isPermanentOrFrozen(const ObjHeader* obj) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-ALWAYS_INLINE bool isShareable(const ObjHeader* obj) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 ObjHeader** ObjHeader::GetWeakCounterLocation() {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 #ifdef KONAN_OBJC_INTEROP
 
 void* ObjHeader::GetAssociatedObject() {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 void** ObjHeader::GetAssociatedObjectLocation() {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 void ObjHeader::SetAssociatedObject(void* obj) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 #endif // KONAN_OBJC_INTEROP
 
 static MetaObjHeader* createMetaObject(TypeInfo** location) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 static void destroyMetaObject(TypeInfo** location) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 extern "C" {
 
-void RestoreMemory(MemoryState*) {
-    // TODO: Remove this function when legacy MM is gone.
-}
-
 RUNTIME_NOTHROW OBJ_GETTER(AllocInstance, const TypeInfo* type_info) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 OBJ_GETTER(AllocArrayInstance, const TypeInfo* type_info, int32_t elements) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 OBJ_GETTER(InitThreadLocalSingleton, ObjHeader** location, const TypeInfo* typeInfo, void (*ctor)(ObjHeader*)) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
-extern const bool IsStrictMemoryModel = true;
-
 RUNTIME_NOTHROW void SetStackRef(ObjHeader** location, const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void SetHeapRef(ObjHeader** location, const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void ZeroHeapRef(ObjHeader** location) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void ZeroArrayRefs(ArrayHeader* array) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void ZeroStackRef(ObjHeader** location) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void UpdateStackRef(ObjHeader** location, const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void UpdateHeapRef(ObjHeader** location, const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void UpdateHeapRefIfNull(ObjHeader** location, const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void UpdateReturnRef(ObjHeader** returnSlot, const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW OBJ_GETTER(
         SwapHeapRefLocked, ObjHeader** location, ObjHeader* expectedValue, ObjHeader* newValue, int32_t* spinlock, int32_t* cookie) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void SetHeapRefLocked(ObjHeader** location, ObjHeader* newValue, int32_t* spinlock, int32_t* cookie) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW OBJ_GETTER(ReadHeapRefLocked, ObjHeader** location, int32_t* spinlock, int32_t* cookie) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void EnterFrame(ObjHeader** start, int parameters, int count) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void LeaveFrame(ObjHeader** start, int parameters, int count) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-RUNTIME_NOTHROW bool ClearSubgraphReferences(ObjHeader* root, bool checked) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 void MutationCheck(ObjHeader* obj) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-RUNTIME_NOTHROW void CheckLifetimesConstraint(ObjHeader* obj, ObjHeader* pointee) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 void FreezeSubgraph(ObjHeader* obj) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 void EnsureNeverFrozen(ObjHeader* obj) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-RUNTIME_NOTHROW void GC_RegisterWorker(void* worker) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-RUNTIME_NOTHROW void GC_UnregisterWorker(void* worker) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-RUNTIME_NOTHROW void GC_CollectorCallback(void* worker) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-bool Kotlin_Any_isShareable(ObjHeader* thiz) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void PerformFullGC(MemoryState* memory) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 bool TryAddHeapRef(const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void ReleaseHeapRef(const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 RUNTIME_NOTHROW void ReleaseHeapRefNoCollect(const ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
+    TODO();
 }
 
 ForeignRefContext InitLocalForeignRef(ObjHeader* object) {
-    RuntimeCheck(false, "Unimplemented");
-}
-
-void CheckGlobalsAccessible() {
-    // Globals are always accessible.
+    TODO();
 }
 
 } // extern "C"
diff --git a/kotlin-native/runtime/src/relaxed/cpp/MemoryImpl.cpp b/kotlin-native/runtime/src/relaxed/cpp/MemoryImpl.cpp
index 4bc24d38c6c..458d2177ae1 100644
--- a/kotlin-native/runtime/src/relaxed/cpp/MemoryImpl.cpp
+++ b/kotlin-native/runtime/src/relaxed/cpp/MemoryImpl.cpp
@@ -9,7 +9,7 @@
 
 extern "C" {
 
-const bool IsStrictMemoryModel = false;
+const MemoryModel CurrentMemoryModel = MemoryModel::kRelaxed;
 
 OBJ_GETTER(AllocInstance, const TypeInfo* typeInfo) {
   RETURN_RESULT_OF(AllocInstanceRelaxed, typeInfo);
diff --git a/kotlin-native/runtime/src/strict/cpp/MemoryImpl.cpp b/kotlin-native/runtime/src/strict/cpp/MemoryImpl.cpp
index 413b802258d..8c0b65891d3 100644
--- a/kotlin-native/runtime/src/strict/cpp/MemoryImpl.cpp
+++ b/kotlin-native/runtime/src/strict/cpp/MemoryImpl.cpp
@@ -9,7 +9,7 @@
 
 extern "C" {
 
-const bool IsStrictMemoryModel = true;
+const MemoryModel CurrentMemoryModel = MemoryModel::kStrict;
 
 OBJ_GETTER(AllocInstance, const TypeInfo* typeInfo) {
   RETURN_RESULT_OF(AllocInstanceStrict, typeInfo);