[modular_aot] Code generation for async/async*/sync*/await/yield/yield*

TEST=ci

Issue: https://github.com/dart-lang/sdk/issues/61635
Change-Id: Ie8da89e09bfad68c65980abc1df69f9273bd6d00
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/497400
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>

pkg/cfg/lib/front_end/ast_to_ir.dart

@@ -116,7 +116,7 @@ class AstToIr extends ast.RecursiveVisitor {
     }
     if (builder.hasOpenBlock) {
       builder.addNullConstant();
-      _buildReturn();
+      builder.addReturn();
     }
     return builder.done();
   }
@@ -152,13 +152,6 @@ class AstToIr extends ast.RecursiveVisitor {
     }
   }
 
-  void _buildReturn() {
-    if (function.isSuspendable) {
-      builder.addLeaveSuspendableFunction(function.returnType);
-    }
-    builder.addReturn();
-  }
-
   void _buildImplicitGetter(ast.Field node) {
     final field = CField(node);
     if (node.isStatic) {
@@ -506,7 +499,7 @@ class AstToIr extends ast.RecursiveVisitor {
     final value = builder.pop();
     _generateNonLocalControlTransfer(node, null, () {
       builder.push(value);
-      _buildReturn();
+      builder.addReturn();
     });
   }
 
@@ -1824,7 +1817,39 @@ class AstToIr extends ast.RecursiveVisitor {
       builder.pop();
       return;
     }
-    builder.addSuspend(node.isYieldStar ? .yieldStar : .yield, const TopType());
+    switch (function.asyncMarker) {
+      case .AsyncStar:
+        // yield/yield* statement acts as a return statement if subscription
+        // to the async* Stream is cancelled.
+        final canceledBlock = builder.newTargetBlock();
+        final continueBlock = builder.newTargetBlock();
+
+        // Suspend will evaluate to true if subscription to async* Stream is cancelled.
+        builder.addSuspend(
+          node.isYieldStar ? .asyncYieldStar : .asyncYield,
+          const BoolType(),
+        );
+        builder.addBranch(canceledBlock, continueBlock);
+
+        builder.startBlock(canceledBlock);
+        _generateNonLocalControlTransfer(node, null, () {
+          builder.addNullConstant();
+          builder.addReturn();
+        });
+
+        builder.startBlock(continueBlock);
+        break;
+
+      case .SyncStar:
+        builder.addSuspend(
+          node.isYieldStar ? .syncYieldStar : .syncYield,
+          const TopType(),
+        );
+        break;
+
+      default:
+        throw 'Unexpected YieldStatement in $function with ${function.asyncMarker}';
+    }
   }
 }
 

pkg/cfg/lib/ir/flow_graph_builder.dart

@@ -622,19 +622,6 @@ class FlowGraphBuilder {
     appendInstruction(instr);
   }
 
-  /// Append [LeaveSuspendableFunction] to the graph.
-  void addLeaveSuspendableFunction(CType type) {
-    final returnValue = pop();
-    final instr = LeaveSuspendableFunction(
-      graph,
-      currentSourcePosition,
-      type,
-      returnValue,
-    );
-    push(instr);
-    appendInstruction(instr);
-  }
-
   /// Append [Suspend] to the graph.
   Suspend addSuspend(SuspendOpcode op, CType type) {
     final typeArguments = (op == .awaitWithTypeCheck) ? pop() : null;

pkg/cfg/lib/ir/flow_graph_checker.dart

@@ -413,11 +413,6 @@ final class FlowGraphChecker extends Pass implements InstructionVisitor<void> {
     verifyTypeArgumentsInput(instr.typeArguments, instr);
   }
 
-  @override
-  void visitLeaveSuspendableFunction(LeaveSuspendableFunction instr) {
-    assert(graph.function.isSuspendable);
-  }
-
   @override
   void visitSuspend(Suspend instr) {
     assert(graph.function.isSuspendable);
@@ -426,8 +421,11 @@ final class FlowGraphChecker extends Pass implements InstructionVisitor<void> {
       case .await || .awaitWithTypeCheck:
         assert(asyncMarker == .Async || asyncMarker == .AsyncStar);
         break;
-      case .yield || .yieldStar:
-        assert(asyncMarker == .AsyncStar || asyncMarker == .SyncStar);
+      case .asyncYield || .asyncYieldStar:
+        assert(asyncMarker == .AsyncStar);
+        break;
+      case .syncYield || .syncYieldStar:
+        assert(asyncMarker == .SyncStar);
         break;
     }
     if (instr.op == .awaitWithTypeCheck) {

pkg/cfg/lib/ir/instructions.dart

@@ -605,6 +605,8 @@ final class Return extends Instruction
     setInputAt(0, value);
   }
 
+  Definition get value => inputDefAt(0);
+
   @override
   R accept<R>(InstructionVisitor<R> v) => v.visitReturn(this);
 }
@@ -1412,29 +1414,15 @@ final class EnterSuspendableFunction extends Instruction
   R accept<R>(InstructionVisitor<R> v) => v.visitEnterSuspendableFunction(this);
 }
 
-/// Leave a suspendable function.
-final class LeaveSuspendableFunction extends Definition
-    with CanThrow, HasSideEffects {
-  @override
-  final CType type;
-
-  LeaveSuspendableFunction(
-    super.graph,
-    super.sourcePosition,
-    this.type,
-    Definition returnValue,
-  ) : super(inputCount: 1) {
-    setInputAt(0, returnValue);
-  }
-
-  Definition get returnValue => inputDefAt(0);
-
-  @override
-  R accept<R>(InstructionVisitor<R> v) => v.visitLeaveSuspendableFunction(this);
+enum SuspendOpcode {
+  await,
+  awaitWithTypeCheck,
+  asyncYield,
+  asyncYieldStar,
+  syncYield,
+  syncYieldStar,
 }
 
-enum SuspendOpcode { await, awaitWithTypeCheck, yield, yieldStar }
-
 /// A point where execution of a suspendable function can be suspended
 /// and resumed (await, yield or yield*).
 final class Suspend extends Definition with CanThrow, HasSideEffects {

pkg/cfg/lib/ir/types.dart

@@ -75,6 +75,9 @@ sealed class CType {
   /// Return non-nullable variant of this type (if possible).
   CType get toNonNullableType;
 
+  /// Returns true if value of this type can be `Future`.
+  bool get canBeFuture;
+
   @override
   bool operator ==(Object other) =>
       other is CType &&
@@ -104,6 +107,9 @@ final class IntType extends CType {
   @override
   CType get toNonNullableType => this;
 
+  @override
+  bool get canBeFuture => false;
+
   @override
   String toString() => 'int';
 }
@@ -127,6 +133,9 @@ final class DoubleType extends CType {
   @override
   CType get toNonNullableType => this;
 
+  @override
+  bool get canBeFuture => false;
+
   @override
   String toString() => 'double';
 }
@@ -150,6 +159,9 @@ final class BoolType extends CType {
   @override
   CType get toNonNullableType => this;
 
+  @override
+  bool get canBeFuture => false;
+
   @override
   String toString() => 'bool';
 }
@@ -173,6 +185,9 @@ final class StringType extends CType {
   @override
   CType get toNonNullableType => this;
 
+  @override
+  bool get canBeFuture => false;
+
   @override
   String toString() => 'String';
 }
@@ -196,6 +211,9 @@ final class ObjectType extends CType {
   @override
   CType get toNonNullableType => this;
 
+  @override
+  bool get canBeFuture => true;
+
   @override
   String toString() => 'Object';
 }
@@ -216,6 +234,9 @@ final class NullType extends CType {
   @override
   CType get toNonNullableType => const NeverType();
 
+  @override
+  bool get canBeFuture => false;
+
   @override
   String toString() => 'Null';
 }
@@ -236,6 +257,9 @@ final class NeverType extends CType {
   @override
   CType get toNonNullableType => this;
 
+  @override
+  bool get canBeFuture => false;
+
   @override
   String toString() => 'Never';
 }
@@ -258,6 +282,9 @@ final class TopType extends CType {
   @override
   CType get toNonNullableType => const ObjectType();
 
+  @override
+  bool get canBeFuture => true;
+
   @override
   String toString() => '<top>';
 }
@@ -278,6 +305,9 @@ final class StaticType extends CType {
   @override
   CType get toNonNullableType => CType.fromStaticType(dartType.toNonNull());
 
+  @override
+  bool get canBeFuture => true;
+
   @override
   String toString() => dartType.getDisplayString();
 }
@@ -301,6 +331,9 @@ sealed class ExtendedType extends CType {
   @override
   CType get toNonNullableType => this;
 
+  @override
+  bool get canBeFuture => false;
+
   @override
   bool operator ==(Object other) =>
       other is ExtendedType && this.kind == other.kind;

pkg/cfg/lib/ir/visitor.dart

@@ -44,7 +44,6 @@ abstract interface class InstructionVisitor<R> {
   R visitAllocateMapLiteral(AllocateMapLiteral instr);
   R visitStringInterpolation(StringInterpolation instr);
   R visitEnterSuspendableFunction(EnterSuspendableFunction instr);
-  R visitLeaveSuspendableFunction(LeaveSuspendableFunction instr);
   R visitSuspend(Suspend instr);
   R visitBinaryIntOp(BinaryIntOp instr);
   R visitUnaryIntOp(UnaryIntOp instr);
@@ -120,8 +119,6 @@ abstract mixin class DefaultInstructionVisitor<R>
       defaultInstruction(instr);
   R visitEnterSuspendableFunction(EnterSuspendableFunction instr) =>
       defaultInstruction(instr);
-  R visitLeaveSuspendableFunction(LeaveSuspendableFunction instr) =>
-      defaultInstruction(instr);
   R visitSuspend(Suspend instr) => defaultInstruction(instr);
   R visitBinaryIntOp(BinaryIntOp instr) => defaultInstruction(instr);
   R visitUnaryIntOp(UnaryIntOp instr) => defaultInstruction(instr);

pkg/cfg/lib/passes/constant_propagation.dart

@@ -450,11 +450,6 @@ final class ConstantPropagation extends Pass
   @override
   void visitEnterSuspendableFunction(EnterSuspendableFunction instr) {}
 
-  @override
-  void visitLeaveSuspendableFunction(LeaveSuspendableFunction instr) {
-    _setNonConstant(instr);
-  }
-
   @override
   void visitSuspend(Suspend instr) {
     _setNonConstant(instr);

pkg/cfg/lib/passes/simplification.dart

@@ -280,10 +280,6 @@ final class Simplification extends Pass
   Instruction visitEnterSuspendableFunction(EnterSuspendableFunction instr) =>
       instr;
 
-  @override
-  Instruction visitLeaveSuspendableFunction(LeaveSuspendableFunction instr) =>
-      instr;
-
   @override
   Instruction visitSuspend(Suspend instr) => instr;
 

pkg/cfg/testcases/suspendable.dart

@@ -23,11 +23,25 @@ Future<void> async5<T>(T x) async {
 }
 
 Stream<int> asyncStar1(int a) async* {
+  print('before');
   yield a;
+  print('after');
 }
 
 Stream<int> asyncStar2(Stream<int> a) async* {
+  print('before');
   yield* a;
+  print('after');
+}
+
+Stream<int> asyncStar3(int a) async* {
+  try {
+    print('before');
+    yield a;
+    print('after');
+  } finally {
+    print('finally');
+  }
 }
 
 Iterable<int> syncStar1(int a) sync* {

pkg/cfg/testcases/suspendable.dart.expect

@@ -3,8 +3,7 @@ B0 = EntryBlock()
   v1 = Constant(<int>)
   v3 = Constant(42)
   EnterSuspendableFunction(v1)
-  v4 = LeaveSuspendableFunction(v3)
-  Return(v4)
+  Return(v3)
 
 --- async2
 B0 = EntryBlock()
@@ -15,8 +14,7 @@ B0 = EntryBlock()
   v6 = Suspend await(v1)
   v8 = Suspend await(v2)
   v9 = BinaryIntOp +(v6, v8)
-  v10 = LeaveSuspendableFunction(v9)
-  Return(v10)
+  Return(v9)
 
 --- async3
 B0 = EntryBlock()
@@ -27,8 +25,7 @@ B0 = EntryBlock()
   EnterSuspendableFunction(v2)
   v6 = Suspend awaitWithTypeCheck(v1, v5)
   DirectCall print(v6)
-  v11 = LeaveSuspendableFunction(v10)
-  Return(v11)
+  Return(v10)
 
 --- async4
 B0 = EntryBlock()
@@ -40,8 +37,7 @@ B0 = EntryBlock()
   EnterSuspendableFunction(v6)
   v8 = TypeArguments(v5, v4, <async4.T%>)
   v10 = DirectCall _GrowableList._literal1(v8, v2)
-  v11 = LeaveSuspendableFunction(v10)
-  Return(v11)
+  Return(v10)
 
 --- async5
 B0 = EntryBlock()
@@ -54,28 +50,72 @@ B0 = EntryBlock()
   v9 = TypeArguments(v8, v4, <async5.T%>)
   v10 = Suspend awaitWithTypeCheck(v2, v9)
   DirectCall print(v10)
-  v14 = LeaveSuspendableFunction(v8)
-  Return(v14)
+  Return(v8)
 
 --- asyncStar1
-B0 = EntryBlock()
+B0 = EntryBlock() dominates:(B8, B7)
   v2 = Constant(<int>)
-  v6 = Constant(null)
+  v4 = Constant("before")
+  v11 = Constant(null)
+  v13 = Constant("after")
   v1 = Parameter(a)
   EnterSuspendableFunction(v2)
-  Suspend yield(v1)
-  v7 = LeaveSuspendableFunction(v6)
-  Return(v7)
+  DirectCall print(v4)
+  v9 = Suspend asyncYield(v1)
+  Branch(v9, true: B7, false: B8)
+B7 = TargetBlock() idom:B0
+  Return(v11)
+B8 = TargetBlock() idom:B0
+  DirectCall print(v13)
+  Return(v11)
 
 --- asyncStar2
-B0 = EntryBlock()
+B0 = EntryBlock() dominates:(B8, B7)
   v2 = Constant(<int>)
-  v6 = Constant(null)
+  v4 = Constant("before")
+  v11 = Constant(null)
+  v13 = Constant("after")
   v1 = Parameter(a)
   EnterSuspendableFunction(v2)
-  Suspend yieldStar(v1)
-  v7 = LeaveSuspendableFunction(v6)
-  Return(v7)
+  DirectCall print(v4)
+  v9 = Suspend asyncYieldStar(v1)
+  Branch(v9, true: B7, false: B8)
+B7 = TargetBlock() idom:B0
+  Return(v11)
+B8 = TargetBlock() idom:B0
+  DirectCall print(v13)
+  Return(v11)
+
+--- asyncStar3
+B0 = EntryBlock() dominates:(B5, B4)
+  v2 = Constant(<int>)
+  v7 = Constant("before")
+  v16 = Constant("after")
+  v22 = Constant("finally")
+  v28 = Constant(null)
+  v1 = Parameter(a)
+  EnterSuspendableFunction(v2)
+  TryEntry(try-body: B4, catch-block: B5)
+B4 = TargetBlock() exception-handler:B5 idom:B0 dominates:(B11, B10)
+  DirectCall print(v7)
+  v12 = Suspend asyncYield(v1)
+  Branch(v12, true: B10, false: B11)
+B10 = TargetBlock() exception-handler:B5 idom:B4 dominates:(B14)
+  Goto(B14)
+B14 = JoinBlock(B10) idom:B10
+  DirectCall print(v22)
+  Return(v28)
+B11 = TargetBlock() exception-handler:B5 idom:B4 dominates:(B18)
+  DirectCall print(v16)
+  Goto(B18)
+B18 = JoinBlock(B11) idom:B11
+  DirectCall print(v22)
+  Return(v28)
+B5 = CatchBlock() idom:B0
+  v20 = Parameter(#exception)
+  v21 = Parameter(#stackTrace)
+  DirectCall print(v22)
+  Throw(v20, v21)
 
 --- syncStar1
 B0 = EntryBlock()
@@ -83,9 +123,8 @@ B0 = EntryBlock()
   v6 = Constant(null)
   v1 = Parameter(a)
   EnterSuspendableFunction(v2)
-  Suspend yield(v1)
-  v7 = LeaveSuspendableFunction(v6)
-  Return(v7)
+  Suspend syncYield(v1)
+  Return(v6)
 
 --- syncStar2
 B0 = EntryBlock()
@@ -93,9 +132,8 @@ B0 = EntryBlock()
   v6 = Constant(null)
   v1 = Parameter(a)
   EnterSuspendableFunction(v2)
-  Suspend yieldStar(v1)
-  v7 = LeaveSuspendableFunction(v6)
-  Return(v7)
+  Suspend syncYieldStar(v1)
+  Return(v6)
 
 --- main
 B0 = EntryBlock()