Fix basic blocks order for WHEN expression

Merge-request: KT-MR-6833
Merged-by: Vladimir Sukharev <Vladimir.Sukharev@jetbrains.com>

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt

@@ -1283,12 +1283,16 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
      *  }
      *  we cannot determine if the result of when is assigned or not.
      */
-    private inner class WhenEmittingContext(val expression: IrWhen) {
+    private inner class WhenEmittingContext(val expression: IrWhen, val lastBBOfWhenCases: LLVMBasicBlockRef) {
         val needsPhi = expression.branches.last().isUnconditional() && !expression.type.isUnit()
         val llvmType = codegen.getLLVMType(expression.type)
 
-        val bbExit = lazy { functionGenerationContext.basicBlock("when_exit", expression.endLocation) }
-
+        val bbExit = lazy {
+            // bbExit must be positioned after all blocks of WHEN construct
+            functionGenerationContext.appendingTo(lastBBOfWhenCases) {
+                functionGenerationContext.basicBlock("when_exit", expression.endLocation)
+            }
+        }
         val resultPhi = lazy {
             functionGenerationContext.appendingTo(bbExit.value) {
                 functionGenerationContext.phi(llvmType)
@@ -1296,19 +1300,35 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
         }
     }
 
+    /** For WHEN { COND1 -> CASE1, COND2 -> CASE2, ELSE -> UNCONDITIONAL }
+     * the following sequence of basic blocks is generated:
+     * -- if COND1
+     * -- CASE1
+     * -- NEXT1(if COND2)
+     * -- CASE2
+     * -- NEXT2 (UNCONDITIONAL)
+     * -- EXIT
+     */
     private fun evaluateWhen(expression: IrWhen, resultSlot: LLVMValueRef?): LLVMValueRef {
         context.log{"evaluateWhen                   : ${ir2string(expression)}"}
 
-        val whenEmittingContext = WhenEmittingContext(expression)
-
         generateDebugTrambolineIf("when", expression)
-        expression.branches.forEach {
-            val bbNext = if (it == expression.branches.last())
-                             null
-                         else
-                             functionGenerationContext.basicBlock("when_next", it.startLocation, it.endLocation)
-            generateWhenCase(whenEmittingContext, it, bbNext, resultSlot)
+
+        // First, generate all empty basic blocks for conditions and variants
+        val bbOfFirstConditionCheck = functionGenerationContext.currentBlock
+        val branchInfos: List<BranchCaseNextInfo> = expression.branches.map {
+            // Carefully create empty basic blocks and position them one after another
+            val bbCase = if (it.isUnconditional()) null else
+                functionGenerationContext.basicBlock("when_case", it.startLocation, it.endLocation).apply { functionGenerationContext.positionAtEnd(this) }
+            val bbNext = if (it.isUnconditional() || it == expression.branches.last()) null else
+                functionGenerationContext.basicBlock("when_next", it.startLocation, it.endLocation).apply { functionGenerationContext.positionAtEnd(this) }
+            BranchCaseNextInfo(it, bbCase, bbNext, resultSlot)
         }
+        // Now, exit basic block can be positioned after all blocks of WHEN expression
+        val whenEmittingContext = WhenEmittingContext(expression, lastBBOfWhenCases = functionGenerationContext.currentBlock)
+        functionGenerationContext.positionAtEnd(bbOfFirstConditionCheck)
+
+        branchInfos.forEach { generateWhenCase(whenEmittingContext, it) }
 
         if (whenEmittingContext.bbExit.isInitialized())
             functionGenerationContext.positionAtEnd(whenEmittingContext.bbExit.value)
@@ -1330,25 +1350,26 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
         }
     }
 
-    private fun generateWhenCase(whenEmittingContext: WhenEmittingContext, branch: IrBranch, bbNext: LLVMBasicBlockRef?, resultSlot: LLVMValueRef?) {
-        val brResult = if (branch.isUnconditional())
-            evaluateExpression(branch.result, resultSlot)
-        else {
-            val bbCase = functionGenerationContext.basicBlock("when_case", branch.startLocation, branch.endLocation)
-            val condition = evaluateExpression(branch.condition)
-            functionGenerationContext.condBr(condition, bbCase, bbNext ?: whenEmittingContext.bbExit.value)
-            functionGenerationContext.positionAtEnd(bbCase)
-            evaluateExpression(branch.result, resultSlot)
-        }
-        if (!functionGenerationContext.isAfterTerminator()) {
-            if (whenEmittingContext.needsPhi)
-                functionGenerationContext.assignPhis(whenEmittingContext.resultPhi.value to brResult)
-            functionGenerationContext.br(whenEmittingContext.bbExit.value)
-        }
-        if (bbNext != null)
-            functionGenerationContext.positionAtEnd(bbNext)
-    }
+    private data class BranchCaseNextInfo(val branch: IrBranch, val bbCase: LLVMBasicBlockRef?, val bbNext: LLVMBasicBlockRef?,
+                                          val resultSlot: LLVMValueRef?)
 
+    private fun generateWhenCase(whenEmittingContext: WhenEmittingContext, branchCaseNextInfo: BranchCaseNextInfo) {
+        with(branchCaseNextInfo) {
+            if (!branch.isUnconditional()) {
+                val condition = evaluateExpression(branch.condition)
+                functionGenerationContext.condBr(condition, bbCase, bbNext ?: whenEmittingContext.bbExit.value)
+                functionGenerationContext.positionAtEnd(bbCase!!)
+            }
+            val brResult = evaluateExpression(branch.result, resultSlot)
+            if (!functionGenerationContext.isAfterTerminator()) {
+                if (whenEmittingContext.needsPhi)
+                    functionGenerationContext.assignPhis(whenEmittingContext.resultPhi.value to brResult)
+                functionGenerationContext.br(whenEmittingContext.bbExit.value)
+            }
+            if (bbNext != null)
+                functionGenerationContext.positionAtEnd(bbNext)
+        }
+    }
     //-------------------------------------------------------------------------//
 
     private fun evaluateWhileLoop(loop: IrWhileLoop): LLVMValueRef {

kotlin-native/backend.native/tests/build.gradle

@@ -6151,6 +6151,10 @@ fileCheckTest("filecheck_smoke0") {
     annotatedSource = project.file('filecheck/smoke0.kt')
 }
 
+fileCheckTest("filecheck_when") {
+    annotatedSource = project.file('filecheck/when.kt')
+}
+
 if (HostManager.@Companion.hostIsMac) {
     fileCheckTest("filecheck_force_arm_instruction_set") {
         enabled = enabled && cacheTesting == null

kotlin-native/backend.native/tests/codegen/stringConcatenationTypeNarrowing/kt53119_append_generated.kt

@@ -7,16 +7,14 @@ package codegen.stringConcatenationTypeNarrowing.kt53119_append_generated
 import kotlin.test.*
 
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated#maybeAnyMaybeAny
-// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
-// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String)
-// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
-// CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
-
-// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
-// CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
-
 // CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
 // CHECK-NOT: Foo#toString(){}kotlin.String"
+// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
+// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String)
+// CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
+
+// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
+// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 
 // CHECK: ret %struct.ObjHeader*
@@ -26,14 +24,13 @@ fun maybeAnyMaybeAny(maybeAny1: Any?, maybeAny2: Any?): String {
 }
 
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated#maybeAnyMaybeString
+// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String)
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 
-// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
-// CHECK-NOT: Foo#toString(){}kotlin.String"
-
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 // CHECK: ret %struct.ObjHeader*
 
@@ -42,14 +39,13 @@ fun maybeAnyMaybeString(maybeAny1: Any?, maybeString2: String?): String {
 }
 
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated#maybeAnyString
+// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String)
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String)
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 
-// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
-// CHECK-NOT: Foo#toString(){}kotlin.String"
-
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 // CHECK: ret %struct.ObjHeader*
 
@@ -60,6 +56,8 @@ fun maybeAnyString(maybeAny1: Any?, string: String): String {
 data class Foo(val bar: Int)
 
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated#maybeAnyFoo
+// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String)
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
@@ -68,9 +66,6 @@ data class Foo(val bar: Int)
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 
-// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
-// CHECK-NOT: Foo#toString(){}kotlin.String"
-
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 // CHECK: ret %struct.ObjHeader*
 
@@ -78,14 +73,15 @@ fun maybeAnyFoo(maybeAny: Any?, foo: Foo): String {
     return "$maybeAny,$foo"
 }
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated#maybeAnyMaybeFoo
+// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String)
+// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 
-// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
-// CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_generated.Foo#toString(){}kotlin.String"
-// CHECK-NOT: Foo#toString(){}kotlin.String"
 
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 // CHECK: ret %struct.ObjHeader*

kotlin-native/backend.native/tests/codegen/stringConcatenationTypeNarrowing/kt53119_append_manual.kt

@@ -7,11 +7,9 @@ package codegen.stringConcatenationTypeNarrowing.kt53119_append_manual
 import kotlin.test.*
 
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_manual#appendMaybeAny(kotlin.Any?)
-// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
-// CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
-
 // CHECK: %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_append_manual.Foo#toString(){}kotlin.String"
 // CHECK-NOT: Foo#toString(){}kotlin.String"
+// CHECK: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append(kotlin.String?)
 // CHECK-NOT: %struct.ObjHeader* @"kfun:kotlin.text.StringBuilder#append
 
 // CHECK: ret %struct.ObjHeader*

kotlin-native/backend.native/tests/codegen/stringConcatenationTypeNarrowing/kt53119_plus_extension.kt

@@ -9,17 +9,15 @@ import kotlin.test.*
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension#manualPlusExtensionAny
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
+// CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String"
+
 // CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
-// CHECK-NOT: call %struct.ObjHeader* @"kfun:kotlin.String#toString(){}kotlin.String"
-
-// CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension.Foo#toString(){}kotlin.String"
-
 // CHECK-NOT: call %struct.ObjHeader* @"kfun:kotlin.String#toString(){}kotlin.String"
 // CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK-NOT: call %struct.ObjHeader* @Kotlin_String_plusImpl
-// CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
 // CHECK: ret %struct.ObjHeader*
 
@@ -43,16 +41,12 @@ fun manualPlusExtensionString(maybeStr: String?, str: String): kotlin.String =
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension#generatedPlusExtensionAny
 // CHECK-NOT: kfun:kotlin#plus__at__kotlin.String?(kotlin.Any?)
 
+// CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: kfun:kotlin#plus__at__kotlin.String?(kotlin.Any?)
-
-// CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension.Foo#toString(){}kotlin.String"
-
-// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK-NOT: call %struct.ObjHeader* @"kfun:kotlin.String#toString(){}kotlin.String"
-// CHECK-NOT: kfun:kotlin#plus__at__kotlin.String?(kotlin.Any?)
-// CHECK-NOT: call %struct.ObjHeader* @Kotlin_String_plusImpl
 
 // CHECK: ret %struct.ObjHeader*
 
@@ -98,14 +92,12 @@ fun generatedPlusExtensionFoo(maybeStr: String?, foo: Foo): String {
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension#generatedPlusExtensionMaybeFoo
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
+// CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension.Foo#toString(){}kotlin.String"
+// CHECK-NOT: Foo#toString(){}kotlin.String
 // CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: call %struct.ObjHeader* @"kfun:kotlin.String#toString(){}kotlin.String"
 
-// CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_extension.Foo#toString(){}kotlin.String"
-// CHECK-NOT: Foo#toString(){}kotlin.String
-
-// CHECK-NOT: call %struct.ObjHeader* @"kfun:kotlin.String#toString(){}kotlin.String"
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
 // CHECK: ret %struct.ObjHeader*

kotlin-native/backend.native/tests/codegen/stringConcatenationTypeNarrowing/kt53119_plus_member.kt

@@ -9,11 +9,9 @@ import kotlin.test.*
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_member#manualPlusMemberAny
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
-// CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
-// CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
-
 // CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_member.Foo#toString(){}kotlin.String"
 // CHECK-NOT: Foo#toString(){}kotlin.String"
+// CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
 // CHECK: ret %struct.ObjHeader*
@@ -37,12 +35,9 @@ fun manualPlusMemberString(str1: String, str2: String): kotlin.String =
 // CHECK-LABEL: define %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_member#generatedPlusMemberAny
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
-// CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
-// CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
-
 // CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_member.Foo#toString(){}kotlin.String"
 // CHECK-NOT: Foo#toString(){}kotlin.String"
-
+// CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
 
 // CHECK: ret %struct.ObjHeader*
@@ -86,9 +81,10 @@ fun manualPlusMemberFoo(str1: String, foo: Foo): kotlin.String =
 // CHECK call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_member.Foo#toString(){}kotlin.String"
 // CHECK-NOT Foo#toString(){}kotlin.String
 
-// CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK: call %struct.ObjHeader* @"kfun:codegen.stringConcatenationTypeNarrowing.kt53119_plus_member.Foo#toString
+// CHECK-NOT: Foo#toString(){}kotlin.String"
 // CHECK-NOT: kfun:kotlin.String#plus(kotlin.Any?)
+// CHECK: call %struct.ObjHeader* @Kotlin_String_plusImpl
 // CHECK-NOT: Foo#toString(){}kotlin.String"
 
 // CHECK: ret %struct.ObjHeader*

kotlin-native/backend.native/tests/filecheck/when.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+var i = 1
+fun main() {
+    println(when(i) {
+        0 -> 10
+        1 -> 11
+        2 -> 12
+        else -> 13
+    })
+}
+// CHECK-LABEL: define void @"kfun:#main(){}"()
+// CHECK: when_case
+// CHECK: when_next
+// CHECK: when_case1
+// CHECK: when_next2
+// CHECK: when_case3
+// CHECK: when_next4
+// CHECK: when_exit
+// CHECK: call void @"kfun:kotlin.io#println(kotlin.Any?)
+// CHECK: ret void