When by String constants:

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

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

@@ -0,0 +1,15 @@
+
+fun foo() : Int {
+    val x : String = "dsa"
+    when (x) {
+        "a" -> return 1
+        "b" -> return 1
+        "c" -> return 1
+        "d" -> return 1
+        "e" -> return 1
+        "f" -> return 1
+        else -> return -1
+    }
+}
+
+// 1 TABLESWITCH

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

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

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

@@ -0,0 +1,9 @@
+fun foo(x : String) : String {
+    return when (x) {
+        "abc", "cde" -> "abc_cde"
+        "efg", "ghi" -> "efg_ghi"
+        else -> "other"
+    }
+}
+
+// 1 LOOKUPSWITCH

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

@@ -0,0 +1,11 @@
+fun foo(x : String) : String {
+    val y = "cde"
+    when (x) {
+        "abc", "${y}" -> return "abc_cde"
+        "e" + "fg", "ghi" -> return "efg_ghi"
+    }
+
+    return "other"
+}
+
+// 1 LOOKUPSWITCH

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

@@ -0,0 +1,12 @@
+fun foo(x : String) : String {
+    assert("abz]".hashCode() == "aby|".hashCode())
+
+    when (x) {
+        "abz]", "cde" -> return "abz_cde"
+        "aby|", "ghi" -> return "aby_ghi"
+    }
+
+    return "other"
+}
+
+// 1 LOOKUPSWITCH

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

@@ -0,0 +1,19 @@
+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"
+    }
+}
+
+// 2 LOOKUPSWITCH
+