[K/N] Benchmarks on weak references

Merge-request: KT-MR-7575
Merged-by: Alexander Shabalin <Alexander.Shabalin@jetbrains.com>

kotlin-native/performance/swiftinterop/swiftSrc/weakRefBenchmarks.swift

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2010-2022 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.
+ */
+
+import Foundation
+import benchmark
+
+private let REPEAT_COUNT = 10000
+private let REFERENCES_COUNT = 3
+
+private class ReferenceWrapper {
+    private weak var weakRef: KotlinData?
+    private var strongRef: KotlinData?
+
+    init() {
+        let data = KotlinData(x: Int32.random(in: 1 ... 1000))
+        self.strongRef = data
+        self.weakRef = data
+    }
+
+    // This function must not be inlined. We must ensure `weakRef` is accessed at each loop iteration.
+    @inline(never) func value() -> Int32 {
+        let ref: KotlinData? = self.weakRef
+        if ref == nil {
+            return 0
+        }
+        return ref!.x
+    }
+
+    func dispose() {
+        self.strongRef = nil
+    }
+
+    func stress() -> Int32 {
+        var counter: Int32 = 0
+        for _ in 1...REPEAT_COUNT {
+            counter += self.value()
+        }
+        return counter
+    }
+}
+
+private func deadReferenceWrapper() -> ReferenceWrapper {
+    let ref = ReferenceWrapper()
+    ref.dispose()
+    GCKt.collect()
+    return ref
+}
+
+class WeakRefBenchmark {
+    private let aliveRef = ReferenceWrapper()
+    private let deadRef = deadReferenceWrapper()
+
+    // Access alive reference.
+    func aliveReference() {
+        let counter = aliveRef.stress()
+        if counter == 0 {
+            fatalError()
+        }
+    }
+
+    // Access dead reference.
+    func deadReference() {
+        let counter = deadRef.stress()
+        if counter != 0 {
+            fatalError()
+        }
+    }
+
+    // Access reference that is nulled out in the middle.
+    func dyingReference() {
+        let ref = ReferenceWrapper()
+
+        ref.dispose()
+        GCKt.schedule()
+
+        let counter = ref.stress()
+        Blackhole.companion.consume(value: counter)
+    }
+}