[K/N] Do not CAS when marking newly allocated object

Merge-request: KT-MR-12038
Merged-by: Alexey Glushko <aleksei.glushko@jetbrains.com>

kotlin-native/runtime/src/gc/cms/cpp/Barriers.cpp

@@ -68,8 +68,7 @@ ALWAYS_INLINE void gc::BarriersThreadData::onAllocation(ObjHeader* allocated) {
         RuntimeAssert(shouldMark == barriersEnabled, "New allocations marking must happen with and only with weak ref barriers");
         if (shouldMark) {
             auto& objectData = alloc::objectDataForObject(allocated);
-            bool wasUnmarked = objectData.tryMark();
-            RuntimeAssert(wasUnmarked, "No one else could mark this newly allocated object before");
+            objectData.markUncontended();
             markHandle_->addObject();
         }
     }

kotlin-native/runtime/src/gc/cms/cpp/ObjectData.hpp

@@ -16,8 +16,16 @@
 namespace kotlin::gc {
 
 class GC::ObjectData {
+    static constexpr intptr_t kNoQueueMark = 1;
 public:
-    bool tryMark() noexcept { return trySetNext(reinterpret_cast<ObjectData*>(1)); }
+    bool tryMark() noexcept { return trySetNext(reinterpret_cast<ObjectData*>(kNoQueueMark)); }
+
+    void markUncontended() noexcept {
+        RuntimeAssert(!marked(), "Must not be marked previously");
+        auto nextVal = reinterpret_cast<ObjectData*>(kNoQueueMark);
+        setNext(nextVal);
+        RuntimeAssert(next() == nextVal, "Non-atomic marking must not be contended");
+    }
 
     bool marked() const noexcept { return next() != nullptr; }