Added phase RETURNS_INSERTION

Moved explicit insertion of return statement from code generator to a lowering

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanLower.kt

@@ -133,6 +133,9 @@ internal class KonanLower(val context: Context) {
             validateIrFile(context, irFile)
             Autoboxing(context).lower(irFile)
         }
+        phaser.phase(KonanPhase.RETURNS_INSERTION) {
+            ReturnsInsertionLowering(context).lower(irFile)
+        }
     }
 
 }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanPhases.kt

@@ -55,6 +55,7 @@ enum class KonanPhase(val description: String,
     /* ... ... */ LOWER_STRING_CONCAT("String concatenation lowering"),
     /* ... ... */ LOWER_DATA_CLASSES("Data classes lowering"),
     /* ... ... */ AUTOBOX("Autoboxing of primitive types", BRIDGES_BUILDING, LOWER_COROUTINES),
+    /* ... ... */ RETURNS_INSERTION("Returns insertion for Unit functions", AUTOBOX, LOWER_COROUTINES, LOWER_ENUMS),
     /* ... */ BITCODE("LLVM BitCode Generation"),
     /* ... ... */ RTTI("RTTI Generation"),
     /* ... ... */ ESCAPE_ANALYSIS("Escape analysis"),

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

@@ -78,12 +78,8 @@ internal inline fun<R> generateFunction(codegen: CodeGenerator, function: LLVMVa
 inline private fun <R> generateFunctionBody(functionGenerationContext: FunctionGenerationContext, code: FunctionGenerationContext.(FunctionGenerationContext) -> R) {
     functionGenerationContext.prologue()
     functionGenerationContext.code(functionGenerationContext)
-    if (!functionGenerationContext.isAfterTerminator()) {
-        if (functionGenerationContext.returnType == voidType)
-            functionGenerationContext.ret(null)
-        else
-            functionGenerationContext.unreachable()
-    }
+    if (!functionGenerationContext.isAfterTerminator())
+        functionGenerationContext.unreachable()
     functionGenerationContext.epilogue()
     functionGenerationContext.resetDebugLocation()
 }

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

@@ -338,6 +338,7 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
         val ctorFunction = LLVMAddFunction(context.llvmModule, ctorName, kVoidFuncType)!!   // Create constructor function.
         generateFunction(codegen, ctorFunction) {
             call(context.llvm.appendToInitalizersTail, listOf(initNodePtr))             // Add node to the tail of initializers list.
+            ret(null)
         }
         context.llvm.staticInitializers.add(ctorFunction)                                   // Push newly created constructor in staticInitializers list.
     }
@@ -2333,6 +2334,7 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
             // this function.
             val parameter = LLVMGetParam(selector, 0)!!
             callAtFunctionScope(entryPoint, listOf(parameter), Lifetime.IRRELEVANT)
+            ret(null)
         }
         return selector
     }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/ReturnsInsertionLowering.kt

@@ -0,0 +1,39 @@
+package org.jetbrains.kotlin.backend.konan.lower
+
+import org.jetbrains.kotlin.backend.common.FileLoweringPass
+import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
+import org.jetbrains.kotlin.backend.konan.Context
+import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
+import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.builders.irGetObject
+import org.jetbrains.kotlin.ir.builders.irReturn
+import org.jetbrains.kotlin.ir.declarations.IrFile
+import org.jetbrains.kotlin.ir.declarations.IrFunction
+import org.jetbrains.kotlin.ir.expressions.IrBlockBody
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
+import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
+import org.jetbrains.kotlin.ir.visitors.acceptVoid
+import org.jetbrains.kotlin.types.typeUtil.isUnit
+
+internal class ReturnsInsertionLowering(val context: Context) : FileLoweringPass {
+
+    override fun lower(irFile: IrFile) {
+        irFile.acceptVoid(object : IrElementVisitorVoid {
+            override fun visitElement(element: IrElement) {
+                element.acceptChildrenVoid(this)
+            }
+
+            override fun visitFunction(declaration: IrFunction) {
+                declaration.acceptChildrenVoid(this)
+
+                val body = declaration.body
+                if ((declaration.descriptor is ConstructorDescriptor || declaration.descriptor.returnType!!.isUnit()) && body != null) {
+                    val irBuilder = context.createIrBuilder(declaration.symbol, declaration.startOffset, declaration.endOffset)
+                    irBuilder.run {
+                         (body as IrBlockBody).statements += irReturn(irGetObject(this@ReturnsInsertionLowering.context.ir.symbols.unit))
+                    }
+                }
+            }
+        })
+    }
+}

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/SuspendFunctionsLowering.kt

@@ -25,7 +25,9 @@ import org.jetbrains.kotlin.backend.common.ir.createOverriddenDescriptor
 import org.jetbrains.kotlin.backend.common.lower.*
 import org.jetbrains.kotlin.backend.konan.Context
 import org.jetbrains.kotlin.backend.konan.descriptors.synthesizedName
-import org.jetbrains.kotlin.backend.konan.ir.*
+import org.jetbrains.kotlin.backend.konan.ir.IrSuspendableExpressionImpl
+import org.jetbrains.kotlin.backend.konan.ir.IrSuspensionPoint
+import org.jetbrains.kotlin.backend.konan.ir.IrSuspensionPointImpl
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.descriptors.impl.ClassConstructorDescriptorImpl

backend.native/tests/build.gradle

@@ -943,6 +943,18 @@ task coroutines_simple(type: RunKonanTest) {
     source = "codegen/coroutines/simple.kt"
 }
 
+task coroutines_degenerate1(type: RunKonanTest) {
+    disabled = (project.testTarget == 'wasm32') // llvm: 'WebAssembly hasn't implemented computed gotos'
+    goldValue = "s1\n"
+    source = "codegen/coroutines/degenerate1.kt"
+}
+
+task coroutines_degenerate2(type: RunKonanTest) {
+    disabled = (project.testTarget == 'wasm32') // llvm: 'WebAssembly hasn't implemented computed gotos'
+    goldValue = "s2\ns1\n"
+    source = "codegen/coroutines/degenerate2.kt"
+}
+
 task coroutines_withReceiver(type: RunKonanTest) {
     disabled = (project.testTarget == 'wasm32') // llvm: 'WebAssembly hasn't implemented computed gotos'
     goldValue = "42\n"

backend.native/tests/codegen/coroutines/degenerate1.kt

@@ -0,0 +1,22 @@
+import kotlin.coroutines.experimental.*
+import kotlin.coroutines.experimental.intrinsics.*
+
+open class EmptyContinuation(override val context: CoroutineContext = EmptyCoroutineContext) : Continuation<Any?> {
+    companion object : EmptyContinuation()
+    override fun resume(value: Any?) {}
+    override fun resumeWithException(exception: Throwable) { throw exception }
+}
+
+suspend fun s1() {
+    println("s1")
+}
+
+fun builder(c: suspend () -> Unit) {
+    c.startCoroutine(EmptyContinuation)
+}
+
+fun main(args: Array<String>) {
+    builder {
+        s1()
+    }
+}

backend.native/tests/codegen/coroutines/degenerate2.kt

@@ -0,0 +1,29 @@
+import kotlin.coroutines.experimental.*
+import kotlin.coroutines.experimental.intrinsics.*
+
+open class EmptyContinuation(override val context: CoroutineContext = EmptyCoroutineContext) : Continuation<Any?> {
+    companion object : EmptyContinuation()
+    override fun resume(value: Any?) {}
+    override fun resumeWithException(exception: Throwable) { throw exception }
+}
+
+suspend fun s1(): Unit = suspendCoroutineOrReturn { x ->
+    println("s1")
+    x.resume(Unit)
+    COROUTINE_SUSPENDED
+}
+
+suspend fun s2() {
+    println("s2")
+    s1()
+}
+
+fun builder(c: suspend () -> Unit) {
+    c.startCoroutine(EmptyContinuation)
+}
+
+fun main(args: Array<String>) {
+    builder {
+        s2()
+    }
+}