diff --git a/kotlin-native/runtime/src/main/cpp/Memory.h b/kotlin-native/runtime/src/main/cpp/Memory.h
index 5d1fe431a4a..dd5e7067212 100644
--- a/kotlin-native/runtime/src/main/cpp/Memory.h
+++ b/kotlin-native/runtime/src/main/cpp/Memory.h
@@ -220,6 +220,7 @@ void SetHeapRefLocked(ObjHeader** location, ObjHeader* newValue, int32_t* spinlo
     int32_t* cookie) RUNTIME_NOTHROW;
 // Reads reference with taken lock.
 OBJ_GETTER(ReadHeapRefLocked, ObjHeader** location, int32_t* spinlock, int32_t* cookie) RUNTIME_NOTHROW;
+OBJ_GETTER(ReadHeapRefNoLock, ObjHeader* object, int32_t index);
 // Called on frame enter, if it has object slots.
 void EnterFrame(ObjHeader** start, int parameters, int count) RUNTIME_NOTHROW;
 // Called on frame leave, if it has object slots.
@@ -257,7 +258,27 @@ void GC_RegisterWorker(void* worker) RUNTIME_NOTHROW;
 void GC_UnregisterWorker(void* worker) RUNTIME_NOTHROW;
 void GC_CollectorCallback(void* worker) RUNTIME_NOTHROW;
 
+void Kotlin_native_internal_GC_collect(ObjHeader*);
+void Kotlin_native_internal_GC_collectCyclic(ObjHeader*);
+void Kotlin_native_internal_GC_suspend(ObjHeader*);
+void Kotlin_native_internal_GC_resume(ObjHeader*);
+void Kotlin_native_internal_GC_stop(ObjHeader*);
+void Kotlin_native_internal_GC_start(ObjHeader*);
+void Kotlin_native_internal_GC_setThreshold(ObjHeader*, int32_t value);
+int32_t Kotlin_native_internal_GC_getThreshold(ObjHeader*);
+void Kotlin_native_internal_GC_setCollectCyclesThreshold(ObjHeader*, int64_t value);
+int64_t Kotlin_native_internal_GC_getCollectCyclesThreshold(ObjHeader*);
+void Kotlin_native_internal_GC_setThresholdAllocations(ObjHeader*, int64_t value);
+int64_t Kotlin_native_internal_GC_getThresholdAllocations(ObjHeader*);
+void Kotlin_native_internal_GC_setTuneThreshold(ObjHeader*, int32_t value);
+bool Kotlin_native_internal_GC_getTuneThreshold(ObjHeader*);
+OBJ_GETTER(Kotlin_native_internal_GC_detectCycles, ObjHeader*);
+OBJ_GETTER(Kotlin_native_internal_GC_findCycle, ObjHeader*, ObjHeader* root);
+bool Kotlin_native_internal_GC_getCyclicCollector(ObjHeader* gc);
+void Kotlin_native_internal_GC_setCyclicCollector(ObjHeader* gc, bool value);
+
 bool Kotlin_Any_isShareable(ObjHeader* thiz);
+void Kotlin_Any_share(ObjHeader* thiz);
 void PerformFullGC(MemoryState* memory) RUNTIME_NOTHROW;
 
 bool TryAddHeapRef(const ObjHeader* object);
diff --git a/kotlin-native/runtime/src/main/kotlin/kotlin/native/concurrent/MutableData.kt b/kotlin-native/runtime/src/main/kotlin/kotlin/native/concurrent/MutableData.kt
index 5f17ff70695..e097f883df3 100644
--- a/kotlin-native/runtime/src/main/kotlin/kotlin/native/concurrent/MutableData.kt
+++ b/kotlin-native/runtime/src/main/kotlin/kotlin/native/concurrent/MutableData.kt
@@ -31,7 +31,11 @@ public class MutableData constructor(capacity: Int = 16) {
 
     private var buffer_ = ByteArray(capacity).apply { share() }
     private var buffer: ByteArray
-        get() = readHeapRefNoLock(this, 0) as ByteArray
+        get() =
+            when (kotlin.native.Platform.memoryModel) {
+                kotlin.native.MemoryModel.EXPERIMENTAL -> buffer_
+                else -> readHeapRefNoLock(this, 0) as ByteArray
+            }
         set(value) { buffer_ = value}
     private var size_ = 0
     private val lock = Lock()
@@ -130,4 +134,4 @@ public class MutableData constructor(capacity: Int = 16) {
     public fun <R> withBufferLocked(block: (array: ByteArray, dataSize: Int) -> R) = locked(lock) {
         block(buffer, size)
     }
-}
\ No newline at end of file
+}
diff --git a/kotlin-native/runtime/src/mm/cpp/Memory.cpp b/kotlin-native/runtime/src/mm/cpp/Memory.cpp
index 75a76239c1b..0ea354c650f 100644
--- a/kotlin-native/runtime/src/mm/cpp/Memory.cpp
+++ b/kotlin-native/runtime/src/mm/cpp/Memory.cpp
@@ -142,6 +142,11 @@ extern "C" RUNTIME_NOTHROW void InitAndRegisterGlobal(ObjHeader** location, cons
 
 extern "C" const MemoryModel CurrentMemoryModel = MemoryModel::kExperimental;
 
+extern "C" OBJ_GETTER(ReadHeapRefNoLock, ObjHeader* object, int32_t index) {
+    // TODO: Remove when legacy MM is gone.
+    ThrowNotImplementedError();
+}
+
 extern "C" RUNTIME_NOTHROW void EnterFrame(ObjHeader** start, int parameters, int count) {
     auto* threadData = mm::ThreadRegistry::Instance().CurrentThreadData();
     threadData->shadowStack().EnterFrame(start, parameters, count);
@@ -183,11 +188,42 @@ extern "C" RUNTIME_NOTHROW void GC_CollectorCallback(void* worker) {
     // Nothing to do
 }
 
+extern "C" void Kotlin_native_internal_GC_collectCyclic(ObjHeader*) {
+    // TODO: Remove when legacy MM is gone.
+    ThrowIllegalArgumentException();
+}
+
+extern "C" OBJ_GETTER(Kotlin_native_internal_GC_detectCycles, ObjHeader*) {
+    // TODO: Remove when legacy MM is gone.
+    RETURN_OBJ(nullptr);
+}
+
+extern "C" OBJ_GETTER(Kotlin_native_internal_GC_findCycle, ObjHeader*, ObjHeader* root) {
+    // TODO: Remove when legacy MM is gone.
+    RETURN_OBJ(nullptr);
+}
+
+extern "C" bool Kotlin_native_internal_GC_getCyclicCollector(ObjHeader* gc) {
+    // TODO: Remove when legacy MM is gone.
+    return false;
+}
+
+extern "C" void Kotlin_native_internal_GC_setCyclicCollector(ObjHeader* gc, bool value) {
+    // TODO: Remove when legacy MM is gone.
+    if (value)
+        ThrowIllegalArgumentException();
+}
+
 extern "C" bool Kotlin_Any_isShareable(ObjHeader* thiz) {
     // TODO: Remove when legacy MM is gone.
     return true;
 }
 
+extern "C" void Kotlin_Any_share(ObjHeader* thiz) {
+    // TODO: Remove when legacy MM is gone.
+    // Nothing to do
+}
+
 extern "C" RUNTIME_NOTHROW bool ClearSubgraphReferences(ObjHeader* root, bool checked) {
     // TODO: Remove when legacy MM is gone.
     return true;
diff --git a/kotlin-native/runtime/src/mm/cpp/Stubs.cpp b/kotlin-native/runtime/src/mm/cpp/Stubs.cpp
index b2c2dabc5fe..cf53f4f8b73 100644
--- a/kotlin-native/runtime/src/mm/cpp/Stubs.cpp
+++ b/kotlin-native/runtime/src/mm/cpp/Stubs.cpp
@@ -82,6 +82,58 @@ void EnsureNeverFrozen(ObjHeader* obj) {
     TODO();
 }
 
+void Kotlin_native_internal_GC_collect(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_suspend(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_resume(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_stop(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_start(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_setThreshold(ObjHeader*, int32_t value) {
+    TODO();
+}
+
+int32_t Kotlin_native_internal_GC_getThreshold(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_setCollectCyclesThreshold(ObjHeader*, int64_t value) {
+    TODO();
+}
+
+int64_t Kotlin_native_internal_GC_getCollectCyclesThreshold(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_setThresholdAllocations(ObjHeader*, int64_t value) {
+    TODO();
+}
+
+int64_t Kotlin_native_internal_GC_getThresholdAllocations(ObjHeader*) {
+    TODO();
+}
+
+void Kotlin_native_internal_GC_setTuneThreshold(ObjHeader*, int32_t value) {
+    TODO();
+}
+
+bool Kotlin_native_internal_GC_getTuneThreshold(ObjHeader*) {
+    TODO();
+}
+
 RUNTIME_NOTHROW void PerformFullGC(MemoryState* memory) {
     TODO();
 }