When by String constants:

Generate TABLESWITCH/LOOKUPSWITCH bytecode operation for when operator by String constants

compiler/testData/codegen/bytecodeText/whenStringOptimization/duplicatingItems.kt

@@ -0,0 +1,11 @@
+import kotlin.test.assertEquals
+
+fun foo(x : String) : String {
+    when (x) {
+        "abc" -> return "abc"
+        "efg", "ghi", "abc" -> return "efg_ghi"
+        else -> return "other"
+    }
+}
+
+// 1 LOOKUPSWITCH