[K/N] Add test for tls load optimisation

^KT-50139

kotlin-native/backend.native/tests/filecheck/single_tls_load.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+class Wrapper(x: Int)
+
+// CHECK-LABEL: "kfun:#f(kotlin.Int;kotlin.String){}"
+fun f(x: Int, s: String) {
+    // CHECK: _ZN6kotlin2mm14ThreadRegistry22currentThreadDataNode_E
+    // CHECK-NOT: _ZN6kotlin2mm14ThreadRegistry22currentThreadDataNode_E
+    if (x < 0) throw IllegalStateException()
+    if (x > 0) return f(x - 1, s)
+    val b = Wrapper(2)
+    val a = listOf(x, x, Wrapper(1), 2, x)
+    for (i in a) { println("$s i") }
+// CHECK: {{^}$}}
+}
+
+fun main() { f(10, "123456") }