When by String constants:

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

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

@@ -0,0 +1,16 @@
+import kotlin.test.assertEquals
+
+fun foo(x : String) : String {
+    assert("abz]".hashCode() == "aby|".hashCode())
+
+    when (x) {
+        "abz]" -> return "abz"
+        "ghi"  -> return "ghi"
+        "aby|" -> return "aby"
+        "abz]" -> return "fail"
+    }
+
+    return "other"
+}
+
+// 1 LOOKUPSWITCH