[stdlib] Use merge sort for sortWith

backend.native/tests/build.gradle

@@ -1468,6 +1468,10 @@ task sort1(type: RunKonanTest) {
     source = "runtime/collections/sort1.kt"
 }
 
+task sortWith(type: RunKonanTest) {
+    source = "runtime/collections/SortWith.kt"
+}
+
 task if_else(type: RunKonanTest) {
     source = "codegen/branching/if_else.kt"
 }

backend.native/tests/runtime/collections/SortWith.kt

@@ -0,0 +1,83 @@
+package runtime.collections.SortWith
+
+import kotlin.test.*
+
+val correctIncreasing = Comparator<Int> { a, b ->  // correct one.
+    when {
+        a > b -> 1
+        a < b -> -1
+        else -> 0
+    }
+}
+
+val correctDecreasing = Comparator<Int> { a, b ->  // correct one.
+    when {
+        a < b -> 1
+        a > b -> -1
+        else -> 0
+    }
+}
+
+fun Array<Int>.assertSorted(cmp: Comparator<Int>, message: String = "") {
+    for (i in 1 until size) {
+        assertTrue(cmp.compare(this[i - 1], this[i]) <= 0, message)
+    }
+}
+
+data class ComparatorInfo(val name: String, val comparator: Comparator<Int>, val isCorrect: Boolean)
+
+// Assert that the array is sorted in terms of a comparator only for correct/partially correct cases
+val comparators = listOf<ComparatorInfo>(
+    ComparatorInfo("Correct increasing", correctIncreasing ,  true),
+    ComparatorInfo("Correct decreasing", correctDecreasing ,  true),
+    ComparatorInfo("Incorrect increasing", Comparator { a ,b -> if (a > b) 1 else -1 },  false),
+    ComparatorInfo("Incorrect decreasing", Comparator { a ,b -> if (a < b) 1 else -1 },  false),
+    ComparatorInfo("Always 1",  Comparator { a ,b ->  1  },  false),
+    ComparatorInfo("Always -1", Comparator { a ,b ->  -1 },  false),
+    ComparatorInfo("Alwasy 0",  Comparator { a ,b ->  0  },  false)
+)
+
+val arrays = listOf<Array<Int>>(
+    arrayOf(),
+    arrayOf(1),
+    arrayOf(Int.MIN_VALUE, 0, Int.MAX_VALUE),
+    arrayOf(Int.MAX_VALUE, 0, Int.MIN_VALUE),
+    arrayOf(1, 2, 3),
+    arrayOf(-2, -1, 99, 1, 2),
+    arrayOf(90, 91, 0, 98, 99),
+    arrayOf(2, 1, 99, -1, 2),
+    arrayOf(99, 98, 0, 91, 90),
+    arrayOf(42, 42, 42),
+    arrayOf(99, 42, 0, 42, 50),
+    arrayOf(
+        100000, 190001, 200002, 200003, 200004, 210005, 220006, 250007, 300008, 310009, 360010, 365011,
+        380012, 390013, 390014, 399015, 400016, 400017, 400018, 400019, 400020, 400021, 400022, 400023,
+        400024, 400025, 400026, 450027, 450028, 480029, 480030, 500031, 500032, 500033, 500034, 500035,
+        500036, 500037, 500038, 500039, 500040, 500041, 500042, 500043, 500044, 500045, 500046, 500047,
+        500048, 500049, 500050, 500051, 500052, 500053, 505054, 510055, 510056, 510057, 510058, 510059,
+        510060, 510061, 510062, 510063, 410064, 410065, 511066, 511067, 520068, 520069, 420070, 520071,
+        530072, 530073, 530074, 430075, 430076, 530077, 540078, 540079, 540080, 540081, 540082, 540083,
+        540084, 490085, 540086, 540087, 542088, 544089, 546090, 550091, 550092, 550093, 550094, 590095,
+        590096, 595097, 600098, 600099, 600100, 600101, 600102, 600103, 600104, 550105, 600106, 600107,
+        600108, 600109, 600110, 610111, 610112, 610113, 620114, 620115, 620116, 620117, 620118, 620119,
+        640120, 640121, 645122, 645123, 645124, 645125, 645126, 645127, 650128, 700129, 700130
+    )
+)
+
+
+@Test fun runTest() {
+    arrays.forEach { array ->
+        comparators.forEach {
+            val arrayUnderTest = array.copyOf()
+
+            arrayUnderTest.sortWith(it.comparator)
+            if (it.isCorrect) {
+                arrayUnderTest.assertSorted(it.comparator, """
+                    Assert sorted failed for comparator: "${it.name}"
+                    Array: ${array.joinToString()}
+                    Array after sorting: ${arrayUnderTest.joinToString()}
+                """.trimIndent())
+            }
+        }
+    }
+}