[K/N] Add test for tls load optimisation

^KT-50139

kotlin-native/backend.native/tests/build.gradle

@@ -6037,6 +6037,12 @@ fileCheckTest("filecheck_adopted_function_reference") {
     annotatedSource = project.file('filecheck/adopted_function_reference.kt')
 }
 
+fileCheckTest("filecheck_single_tls_load") {
+    enabled = isExperimentalMM && project.globalTestArgs.contains("-opt")
+    annotatedSource = project.file('filecheck/single_tls_load.kt')
+    phaseToCheck = "OptimizeTLSDataLoads"
+}
+
 fileCheckTest("filecheck_signext_zeroext0") {
     annotatedSource = project.file('filecheck/signext_zeroext0.kt')
     if (project.testTarget == 'mingw_x64') {

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") }