Implement unit suspend functions tail-call optimisation

Unlike previously, this optimisation works on every callee return type.
Tail-calls inside unit functions can be either
INVOKE...
ARETURN
or
INVOKE
POP
GETSTATIC kotlin/Unit.INSTANCE
ARETURN
The first pattern is already covered. The second one is a bit tricky,
since we cannot just assume than the function is tail-call, we also need
to check whether the callee returned COROUTINE_SUSPENDED marker.
Thus, resulting bytecode of function's 'epilogue' look like
DUP
INVOKESTATIC getCOROUTINE_SUSPENDED
IF_ACMPNE LN
ARETURN
LN:
POP

 #KT-28938 Fixed

compiler/testData/codegen/box/coroutines/tailCallOptimizations/crossinline.txt

@@ -17,12 +17,7 @@ public final class CrossinlineKt$box$1$filter$$inlined$source$1$1 {
 }
 
 @kotlin.Metadata
-@kotlin.coroutines.jvm.internal.DebugMetadata
 public final class CrossinlineKt$box$1$filter$$inlined$source$1$lambda$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: CrossinlineKt$box$1$filter$$inlined$source$1$lambda$1
@@ -102,28 +97,11 @@ public final class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$1 {
     public final @org.jetbrains.annotations.Nullable method invokeSuspend(@org.jetbrains.annotations.NotNull p0: java.lang.Object): java.lang.Object
 }
 
-@kotlin.Metadata
-@kotlin.coroutines.jvm.internal.DebugMetadata
-public final class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
-    field label: int
-    synthetic field result: java.lang.Object
-    synthetic final field this$0: CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2
-    inner class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2
-    inner class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2$1
-    public method <init>(p0: CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2, p1: kotlin.coroutines.Continuation): void
-    public final @org.jetbrains.annotations.Nullable method invokeSuspend(@org.jetbrains.annotations.NotNull p0: java.lang.Object): java.lang.Object
-}
-
 @kotlin.Metadata
 public final class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2 {
     synthetic final field $this_source$inlined: Sink
     synthetic final field this$0: CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1
     inner class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2
-    inner class CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1$2$1
     public method <init>(p0: Sink, p1: CrossinlineKt$box$1$invokeSuspend$$inlined$filter$1): void
     public method close(@org.jetbrains.annotations.Nullable p0: java.lang.Throwable): void
     public @org.jetbrains.annotations.Nullable method send(p0: java.lang.Object, @org.jetbrains.annotations.NotNull p1: kotlin.coroutines.Continuation): java.lang.Object
@@ -205,12 +183,7 @@ public final class CrossinlineKt$filter$$inlined$source$1$1 {
 }
 
 @kotlin.Metadata
-@kotlin.coroutines.jvm.internal.DebugMetadata
 public final class CrossinlineKt$filter$$inlined$source$1$lambda$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: CrossinlineKt$filter$$inlined$source$1$lambda$1

compiler/testData/codegen/box/coroutines/tailCallOptimizations/crossinline_1_2.txt

@@ -17,29 +17,11 @@ public final class CrossinlineKt$box$1$doResume$$inlined$filter$1$1 {
     synthetic final method setLabel(p0: int): void
 }
 
-@kotlin.Metadata
-public final class CrossinlineKt$box$1$doResume$$inlined$filter$1$2$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
-    synthetic field data: java.lang.Object
-    synthetic field exception: java.lang.Throwable
-    synthetic final field this$0: CrossinlineKt$box$1$doResume$$inlined$filter$1$2
-    inner class CrossinlineKt$box$1$doResume$$inlined$filter$1$2
-    inner class CrossinlineKt$box$1$doResume$$inlined$filter$1$2$1
-    public method <init>(p0: CrossinlineKt$box$1$doResume$$inlined$filter$1$2, p1: kotlin.coroutines.experimental.Continuation): void
-    public final @org.jetbrains.annotations.Nullable method doResume(@org.jetbrains.annotations.Nullable p0: java.lang.Object, @org.jetbrains.annotations.Nullable p1: java.lang.Throwable): java.lang.Object
-    synthetic final method getLabel(): int
-    synthetic final method setLabel(p0: int): void
-}
-
 @kotlin.Metadata
 public final class CrossinlineKt$box$1$doResume$$inlined$filter$1$2 {
     synthetic final field $this_source$inlined: Sink
     synthetic final field this$0: CrossinlineKt$box$1$doResume$$inlined$filter$1
     inner class CrossinlineKt$box$1$doResume$$inlined$filter$1$2
-    inner class CrossinlineKt$box$1$doResume$$inlined$filter$1$2$1
     public method <init>(p0: Sink, p1: CrossinlineKt$box$1$doResume$$inlined$filter$1): void
     public method close(@org.jetbrains.annotations.Nullable p0: java.lang.Throwable): void
     public @org.jetbrains.annotations.Nullable method send(p0: java.lang.Object, @org.jetbrains.annotations.NotNull p1: kotlin.coroutines.experimental.Continuation): java.lang.Object
@@ -84,10 +66,6 @@ public final class CrossinlineKt$box$1$filter$$inlined$source$1$1 {
 
 @kotlin.Metadata
 public final class CrossinlineKt$box$1$filter$$inlined$source$1$lambda$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     synthetic field data: java.lang.Object
     synthetic field exception: java.lang.Throwable
     synthetic final field this$0: CrossinlineKt$box$1$filter$$inlined$source$1$lambda$1
@@ -212,10 +190,6 @@ public final class CrossinlineKt$filter$$inlined$source$1$1 {
 
 @kotlin.Metadata
 public final class CrossinlineKt$filter$$inlined$source$1$lambda$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     synthetic field data: java.lang.Object
     synthetic field exception: java.lang.Throwable
     synthetic final field this$0: CrossinlineKt$filter$$inlined$source$1$lambda$1

compiler/testData/codegen/box/coroutines/tailCallOptimizations/innerObjectRetransformation.txt

@@ -26,26 +26,9 @@ public final class flow/InnerObjectRetransformationKt$check$$inlined$collect$1 {
     public @org.jetbrains.annotations.Nullable method emit(@org.jetbrains.annotations.NotNull p0: java.lang.Object, @org.jetbrains.annotations.NotNull p1: kotlin.coroutines.Continuation): java.lang.Object
 }
 
-@kotlin.Metadata
-@kotlin.coroutines.jvm.internal.DebugMetadata
-public final class flow/InnerObjectRetransformationKt$check$$inlined$flow$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
-    field label: int
-    synthetic field result: java.lang.Object
-    synthetic final field this$0: flow.InnerObjectRetransformationKt$check$$inlined$flow$1
-    inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1
-    inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1$1
-    public method <init>(p0: flow.InnerObjectRetransformationKt$check$$inlined$flow$1, p1: kotlin.coroutines.Continuation): void
-    public final @org.jetbrains.annotations.Nullable method invokeSuspend(@org.jetbrains.annotations.NotNull p0: java.lang.Object): java.lang.Object
-}
-
 @kotlin.Metadata
 public final class flow/InnerObjectRetransformationKt$check$$inlined$flow$1 {
     inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1
-    inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1$1
     public method <init>(): void
     public @org.jetbrains.annotations.Nullable method collect(@org.jetbrains.annotations.NotNull p0: flow.FlowCollector, @org.jetbrains.annotations.NotNull p1: kotlin.coroutines.Continuation): java.lang.Object
 }
@@ -112,12 +95,7 @@ public final class flow/InnerObjectRetransformationKt$flow$1 {
 }
 
 @kotlin.Metadata
-@kotlin.coroutines.jvm.internal.DebugMetadata
 public final class flow/InnerObjectRetransformationKt$flowWith$$inlined$flow$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: flow.InnerObjectRetransformationKt$flowWith$$inlined$flow$1
@@ -139,12 +117,7 @@ public final class flow/InnerObjectRetransformationKt$flowWith$$inlined$flow$1 {
 }
 
 @kotlin.Metadata
-@kotlin.coroutines.jvm.internal.DebugMetadata
 public final class flow/InnerObjectRetransformationKt$flowWith$$inlined$flow$2$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     field label: int
     synthetic field result: java.lang.Object
     synthetic final field this$0: flow.InnerObjectRetransformationKt$flowWith$$inlined$flow$2

compiler/testData/codegen/box/coroutines/tailCallOptimizations/innerObjectRetransformation_1_2.txt

@@ -24,27 +24,9 @@ public final class flow/InnerObjectRetransformationKt$check$$inlined$collect$1 {
     public @org.jetbrains.annotations.Nullable method emit(@org.jetbrains.annotations.NotNull p0: java.lang.Object, @org.jetbrains.annotations.NotNull p1: kotlin.coroutines.experimental.Continuation): java.lang.Object
 }
 
-@kotlin.Metadata
-public final class flow/InnerObjectRetransformationKt$check$$inlined$flow$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
-    synthetic field data: java.lang.Object
-    synthetic field exception: java.lang.Throwable
-    synthetic final field this$0: flow.InnerObjectRetransformationKt$check$$inlined$flow$1
-    inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1
-    inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1$1
-    public method <init>(p0: flow.InnerObjectRetransformationKt$check$$inlined$flow$1, p1: kotlin.coroutines.experimental.Continuation): void
-    public final @org.jetbrains.annotations.Nullable method doResume(@org.jetbrains.annotations.Nullable p0: java.lang.Object, @org.jetbrains.annotations.Nullable p1: java.lang.Throwable): java.lang.Object
-    synthetic final method getLabel(): int
-    synthetic final method setLabel(p0: int): void
-}
-
 @kotlin.Metadata
 public final class flow/InnerObjectRetransformationKt$check$$inlined$flow$1 {
     inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1
-    inner class flow/InnerObjectRetransformationKt$check$$inlined$flow$1$1
     public method <init>(): void
     public @org.jetbrains.annotations.Nullable method collect(@org.jetbrains.annotations.NotNull p0: flow.FlowCollector, @org.jetbrains.annotations.NotNull p1: kotlin.coroutines.experimental.Continuation): java.lang.Object
 }
@@ -117,10 +99,6 @@ public final class flow/InnerObjectRetransformationKt$flow$1 {
 
 @kotlin.Metadata
 public final class flow/InnerObjectRetransformationKt$flowWith$$inlined$flow$1$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     synthetic field data: java.lang.Object
     synthetic field exception: java.lang.Throwable
     synthetic final field this$0: flow.InnerObjectRetransformationKt$flowWith$$inlined$flow$1
@@ -145,10 +123,6 @@ public final class flow/InnerObjectRetransformationKt$flowWith$$inlined$flow$1 {
 
 @kotlin.Metadata
 public final class flow/InnerObjectRetransformationKt$flowWith$$inlined$flow$2$1 {
-    field L$0: java.lang.Object
-    field L$1: java.lang.Object
-    field L$2: java.lang.Object
-    field L$3: java.lang.Object
     synthetic field data: java.lang.Object
     synthetic field exception: java.lang.Throwable
     synthetic final field this$0: flow.InnerObjectRetransformationKt$flowWith$$inlined$flow$2

compiler/testData/codegen/box/coroutines/tailCallOptimizations/tailSuspendUnitFun.kt

@@ -17,9 +17,9 @@ suspend fun lambdaAsParameterNotTailCall(c: suspend ()->Unit) { c(); c() }
 suspend fun lambdaAsParameterReturn(c: suspend ()->Unit) { return c() }
 suspend fun returnsInt() = 42.also { TailCallOptimizationChecker.saveStackTrace() }
 // This should not be tail-call, since the caller should push Unit.INSTANCE on stack
-suspend fun callsIntNotTailCall() { returnsInt() }
+suspend fun callsIntTailCall() { returnsInt() }
 suspend fun multipleExitPoints(b: Boolean) { if (b) empty() else withoutReturn() }
-suspend fun multipleExitPointsNotTailCall(b: Boolean) { if (b) empty() else returnsInt() }
+suspend fun multipleExitPointsTailCall(b: Boolean) { if (b) empty() else returnsInt() }
 
 fun ordinary() = 1
 inline fun ordinaryInline() { ordinary() }
@@ -95,14 +95,14 @@ fun box(): String {
         lambdaAsParameterReturn { TailCallOptimizationChecker.saveStackTrace() }
         TailCallOptimizationChecker.checkNoStateMachineIn("lambdaAsParameterReturn")
 
-        callsIntNotTailCall()
-        TailCallOptimizationChecker.checkStateMachineIn("callsIntNotTailCall")
+        callsIntTailCall()
+        TailCallOptimizationChecker.checkNoStateMachineIn("callsIntTailCall")
 
         multipleExitPoints(false)
         TailCallOptimizationChecker.checkNoStateMachineIn("multipleExitPoints")
 
-        multipleExitPointsNotTailCall(false)
-        TailCallOptimizationChecker.checkStateMachineIn("multipleExitPointsNotTailCall")
+        multipleExitPointsTailCall(false)
+        TailCallOptimizationChecker.checkNoStateMachineIn("multipleExitPointsTailCall")
 
         multipleExitPointsWithOrdinaryInline(true)
         TailCallOptimizationChecker.checkNoStateMachineIn("multipleExitPointsWithOrdinaryInline")
@@ -120,7 +120,7 @@ fun box(): String {
         TailCallOptimizationChecker.checkNoStateMachineIn("useGenericInferType")
 
         useNullableUnit()
-        TailCallOptimizationChecker.checkStateMachineIn("useNullableUnit")
+        TailCallOptimizationChecker.checkNoStateMachineIn("useNullableUnit")
 
         useRunRunRunRunRun()
         TailCallOptimizationChecker.checkNoStateMachineIn("useRunRunRunRunRun")

compiler/testData/codegen/box/coroutines/tailCallOptimizations/unreachable.kt

@@ -40,8 +40,8 @@ suspend fun lambdaAsParameterReturn(c: suspend () -> Unit) {
 }
 
 suspend fun returnsInt() = 42.also { TailCallOptimizationChecker.saveStackTrace() }
-// This should not be tail-call, since the caller should push Unit.INSTANCE on stack
-suspend fun callsIntNotTailCall() {
+
+suspend fun callsIntTailCall() {
     returnsInt()
     return
     empty()
@@ -53,7 +53,7 @@ suspend fun multipleExitPoints(b: Boolean) {
     empty()
 }
 
-suspend fun multipleExitPointsNotTailCall(b: Boolean) {
+suspend fun multipleExitPointsTailCall(b: Boolean) {
     if (b) empty() else returnsInt()
     return
     empty()
@@ -153,14 +153,14 @@ fun box(): String {
         lambdaAsParameterReturn { TailCallOptimizationChecker.saveStackTrace() }
         TailCallOptimizationChecker.checkNoStateMachineIn("lambdaAsParameterReturn")
 
-        callsIntNotTailCall()
-        TailCallOptimizationChecker.checkStateMachineIn("callsIntNotTailCall")
+        callsIntTailCall()
+        TailCallOptimizationChecker.checkNoStateMachineIn("callsIntTailCall")
 
         multipleExitPoints(false)
         TailCallOptimizationChecker.checkNoStateMachineIn("multipleExitPoints")
 
-        multipleExitPointsNotTailCall(false)
-        TailCallOptimizationChecker.checkStateMachineIn("multipleExitPointsNotTailCall")
+        multipleExitPointsTailCall(false)
+        TailCallOptimizationChecker.checkNoStateMachineIn("multipleExitPointsTailCall")
 
         multipleExitPointsWithOrdinaryInline(true)
         TailCallOptimizationChecker.checkNoStateMachineIn("multipleExitPointsWithOrdinaryInline")
@@ -178,7 +178,7 @@ fun box(): String {
         TailCallOptimizationChecker.checkNoStateMachineIn("useGenericInferType")
 
         useNullableUnit()
-        TailCallOptimizationChecker.checkStateMachineIn("useNullableUnit")
+        TailCallOptimizationChecker.checkNoStateMachineIn("useNullableUnit")
 
         useRunRunRunRunRun()
         TailCallOptimizationChecker.checkNoStateMachineIn("useRunRunRunRunRun")