When by String constants:

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

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

@@ -0,0 +1,20 @@
+import kotlin.test.assertEquals
+
+fun foo(x : String) : String {
+    when (x) {
+        "abc" -> return "abc"
+        "efg", "ghi", "abc" -> return "efg_ghi"
+        else -> return "other"
+    }
+}
+
+fun box() : String {
+    assertEquals("abc", foo("abc"))
+    assertEquals("efg_ghi", foo("efg"))
+    assertEquals("efg_ghi", foo("ghi"))
+
+    assertEquals("other", foo("xyz"))
+
+    return "OK"
+}
+

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

@@ -0,0 +1,24 @@
+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"
+}
+
+fun box() : String {
+    assertEquals("abz", foo("abz]"))
+    assertEquals("aby", foo("aby|"))
+    assertEquals("ghi", foo("ghi"))
+
+    assertEquals("other", foo("xyz"))
+
+    return "OK"
+}

compiler/testData/codegen/boxWithStdlib/whenStringOptimization/expression.kt

@@ -0,0 +1,20 @@
+import kotlin.test.assertEquals
+
+fun foo(x : String) : String {
+    return when (x) {
+        "abc", "cde" -> "abc_cde"
+        "efg", "ghi" -> "efg_ghi"
+        else -> "other"
+    }
+}
+
+fun box() : String {
+    assertEquals("abc_cde", foo("abc"))
+    assertEquals("abc_cde", foo("cde"))
+    assertEquals("efg_ghi", foo("efg"))
+    assertEquals("efg_ghi", foo("ghi"))
+
+    assertEquals("other", foo("xyz"))
+
+    return "OK"
+}

compiler/testData/codegen/boxWithStdlib/whenStringOptimization/sameHashCode.kt

@@ -0,0 +1,23 @@
+import kotlin.test.assertEquals
+
+fun foo(x : String) : String {
+    assert("abz]".hashCode() == "aby|".hashCode())
+
+    when (x) {
+        "abz]", "cde" -> return "abz_cde"
+        "aby|", "ghi", "abz]" -> return "aby_ghi"
+    }
+
+    return "other"
+}
+
+fun box() : String {
+    assertEquals("abz_cde", foo("abz]"))
+    assertEquals("abz_cde", foo("cde"))
+    assertEquals("aby_ghi", foo("aby|"))
+    assertEquals("aby_ghi", foo("ghi"))
+
+    assertEquals("other", foo("xyz"))
+
+    return "OK"
+}

compiler/testData/codegen/boxWithStdlib/whenStringOptimization/statement.kt

@@ -0,0 +1,38 @@
+import kotlin.test.assertEquals
+
+fun foo1(x : String) : String {
+    when (x) {
+        "abc", "cde" -> return "abc_cde"
+        "efg", "ghi" -> return "efg_ghi"
+    }
+
+    return "other"
+}
+
+fun foo2(x : String) : String {
+    when (x) {
+        "abc", "cde" -> return "abc_cde"
+        "efg", "ghi" -> return "efg_ghi"
+        else -> return "other"
+    }
+}
+
+fun box() : String {
+    //foo1
+    assertEquals("abc_cde", foo1("abc"))
+    assertEquals("abc_cde", foo1("cde"))
+    assertEquals("efg_ghi", foo1("efg"))
+    assertEquals("efg_ghi", foo1("ghi"))
+
+    assertEquals("other", foo1("xyz"))
+
+    //foo2
+    assertEquals("abc_cde", foo2("abc"))
+    assertEquals("abc_cde", foo2("cde"))
+    assertEquals("efg_ghi", foo2("efg"))
+    assertEquals("efg_ghi", foo2("ghi"))
+
+    assertEquals("other", foo2("xyz"))
+
+    return "OK"
+}