Binder refactoring, Monster refactoring
This commit is contained in:
Michael Schimmel
@@ -11,8 +11,7 @@ uses
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Myc.Ast.Visitor,
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Myc.Ast.Scope,
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Myc.Ast.Types,
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Myc.Ast,
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Myc.Ast.Binding.Nodes;
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Myc.Ast;
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type
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IAstTCO = interface(IAstVisitor)
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@@ -21,22 +20,27 @@ type
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// This transformer runs *after* the Lowerer (Phase 4).
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// Its sole responsibility is to identify tail calls (TCO)
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// and set the `IsTailCall` flag on TBoundFunctionCallNode.
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// and set the `IsTailCall` flag on TFunctionCallNode.
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TAstTCO = class(TAstTransformer, IAstTCO)
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private
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FIsTailStack: TStack<Boolean>;
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FNextIsTail: Boolean;
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protected
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function Accept(const Node: IAstNode): TDataValue; override;
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function Accept(const Node: IAstNode): IAstNode; override;
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// Overrides for TCO propagation
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function VisitBlockExpression(const Node: IBlockExpressionNode): TDataValue; override;
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function VisitIfExpression(const Node: IIfExpressionNode): TDataValue; override;
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function VisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue; override;
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function VisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue; override;
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function VisitRecurNode(const Node: IRecurNode): TDataValue; override;
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function VisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue; override;
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function VisitBlockExpression(const Node: IBlockExpressionNode): IAstNode; override;
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function VisitIfExpression(const Node: IIfExpressionNode): IAstNode; override;
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function VisitTernaryExpression(const Node: ITernaryExpressionNode): IAstNode; override;
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function VisitLambdaExpression(const Node: ILambdaExpressionNode): IAstNode; override;
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function VisitRecurNode(const Node: IRecurNode): IAstNode; override;
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function VisitMacroExpansionNode(const Node: IMacroExpansionNode): IAstNode; override;
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// Operands are never in tail position.
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function VisitBinaryExpression(const Node: IBinaryExpressionNode): IAstNode; override;
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function VisitUnaryExpression(const Node: IUnaryExpressionNode): IAstNode; override;
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// The core TCO logic
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function VisitFunctionCall(const Node: IFunctionCallNode): TDataValue; override;
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function VisitFunctionCall(const Node: IFunctionCallNode): IAstNode; override;
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public
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constructor Create;
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destructor Destroy; override;
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@@ -70,140 +74,169 @@ end;
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function TAstTCO.Execute(const RootNode: IAstNode): IAstNode;
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begin
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var transformedValue := Accept(RootNode);
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if transformedValue.IsVoid then
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Result := TAst.Block([])
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else
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Result := transformedValue.AsIntf<IAstNode>;
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Result := Accept(RootNode); // Use IAstNode-returning Accept
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if not Assigned(Result) then
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Result := TAst.Block([]);
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end;
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function TAstTCO.Accept(const Node: IAstNode): TDataValue;
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function TAstTCO.Accept(const Node: IAstNode): IAstNode;
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begin
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if (not Assigned(Node)) or Done then
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if (not Assigned(Node)) then
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begin
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Result := nil;
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exit;
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end;
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FIsTailStack.Push(FNextIsTail);
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try
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// Call inherited Accept, which handles the data unwrapping
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Result := inherited Accept(Node);
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finally
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FNextIsTail := FIsTailStack.Pop;
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end;
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end;
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function TAstTCO.VisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
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function TAstTCO.VisitBinaryExpression(const Node: IBinaryExpressionNode): IAstNode;
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begin
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// Operands are never in tail position.
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FNextIsTail := False;
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// Call inherited, which will visit Left and Right with FNextIsTail = False
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Result := inherited VisitBinaryExpression(Node);
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end;
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function TAstTCO.VisitUnaryExpression(const Node: IUnaryExpressionNode): IAstNode;
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begin
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// Operand is never in tail position.
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FNextIsTail := False;
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// Call inherited, which will visit Right with FNextIsTail = False
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Result := inherited VisitUnaryExpression(Node);
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end;
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function TAstTCO.VisitBlockExpression(const Node: IBlockExpressionNode): IAstNode;
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var
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i: Integer;
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isContextTail: Boolean;
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N: TBlockExpressionNode;
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begin
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N := (Node as TBlockExpressionNode);
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isContextTail := FIsTailStack.Peek;
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for i := 0 to High(Node.Expressions) do
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// We must manually iterate here to set FNextIsTail for each child
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for i := 0 to High(N.Expressions) do
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begin
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// Only the last expression in a block is in tail position
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FNextIsTail := isContextTail and (i = High(Node.Expressions));
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Accept(Node.Expressions[i]);
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FNextIsTail := isContextTail and (i = High(N.Expressions));
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N.Expressions[i] := Accept(N.Expressions[i]);
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end;
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Result := TDataValue.FromIntf<IBlockExpressionNode>(Node);
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Result := N;
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end;
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function TAstTCO.VisitIfExpression(const Node: IIfExpressionNode): TDataValue;
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function TAstTCO.VisitIfExpression(const Node: IIfExpressionNode): IAstNode;
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var
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isContextTail: Boolean;
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N: TIfExpressionNode;
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begin
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N := (Node as TIfExpressionNode);
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isContextTail := FIsTailStack.Peek;
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// Condition is never in tail position
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FNextIsTail := False;
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Accept(Node.Condition);
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N.Condition := Accept(N.Condition);
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// Then/Else branches ARE in tail position if the IfExpr is
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FNextIsTail := isContextTail;
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Accept(Node.ThenBranch);
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if Assigned(Node.ElseBranch) then
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Accept(Node.ElseBranch);
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N.ThenBranch := Accept(N.ThenBranch);
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N.ElseBranch := Accept(N.ElseBranch);
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Result := TDataValue.FromIntf<IIfExpressionNode>(Node);
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Result := N;
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end;
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function TAstTCO.VisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue;
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function TAstTCO.VisitTernaryExpression(const Node: ITernaryExpressionNode): IAstNode;
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var
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isContextTail: Boolean;
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N: TTernaryExpressionNode;
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begin
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N := (Node as TTernaryExpressionNode);
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isContextTail := FIsTailStack.Peek;
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// Condition is never in tail position
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FNextIsTail := False;
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Accept(Node.Condition);
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N.Condition := Accept(N.Condition);
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// Then/Else branches ARE in tail position if the TernaryExpr is
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FNextIsTail := isContextTail;
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Accept(Node.ThenBranch);
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Accept(Node.ElseBranch);
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N.ThenBranch := Accept(N.ThenBranch);
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N.ElseBranch := Accept(N.ElseBranch);
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Result := TDataValue.FromIntf<ITernaryExpressionNode>(Node);
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Result := N;
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end;
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function TAstTCO.VisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue;
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function TAstTCO.VisitLambdaExpression(const Node: ILambdaExpressionNode): IAstNode;
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var
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N: TLambdaExpressionNode;
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begin
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// Parameters are never in tail position
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FNextIsTail := False;
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AcceptNodes<IIdentifierNode>(Node.Parameters);
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N := (Node as TLambdaExpressionNode);
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// The body of a lambda is *always* a tail position (relative to the lambda)
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FNextIsTail := True;
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Accept(Node.Body);
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N.Body := Accept(N.Body);
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Result := TDataValue.FromIntf<ILambdaExpressionNode>(Node);
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Result := N;
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end;
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function TAstTCO.VisitRecurNode(const Node: IRecurNode): TDataValue;
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function TAstTCO.VisitRecurNode(const Node: IRecurNode): IAstNode;
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var
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N: TRecurNode;
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begin
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if not FIsTailStack.Peek then
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raise Exception.Create('''recur'' can only be used in a tail position.');
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N := (Node as TRecurNode);
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// Arguments are not in tail position
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FNextIsTail := False;
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AcceptNodes<IAstNode>(Node.Arguments);
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N.Arguments := AcceptNodes<IAstNode>(N.Arguments, function(Node: IAstNode): IAstNode begin exit(Node) end);
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Result := TDataValue.FromIntf<IRecurNode>(Node);
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Result := N;
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end;
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function TAstTCO.VisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue;
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function TAstTCO.VisitMacroExpansionNode(const Node: IMacroExpansionNode): IAstNode;
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var
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N: TMacroExpansionNode;
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begin
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N := (Node as TMacroExpansionNode);
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// Propagate tail call status to the expanded body
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FNextIsTail := FIsTailStack.Peek;
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Accept(Node.ExpandedBody);
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N.ExpandedBody := Accept(N.ExpandedBody);
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// Also visit the original call nodes, though they are not in tail pos
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FNextIsTail := False;
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Accept(Node.Callee);
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AcceptNodes<IAstNode>(Node.Arguments);
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N.Callee := Accept(N.Callee);
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N.Arguments := AcceptNodes<IAstNode>(N.Arguments, function(Node: IAstNode): IAstNode begin exit(Node) end);
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Result := TDataValue.FromIntf<IMacroExpansionNode>(Node);
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Result := N;
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end;
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function TAstTCO.VisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
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function TAstTCO.VisitFunctionCall(const Node: IFunctionCallNode): IAstNode;
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var
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callee: IAstNode;
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args: TArray<IAstNode>;
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isTailCall: Boolean;
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N: TFunctionCallNode;
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begin
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isTailCall := FIsTailStack.Peek;
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N := (Node as TFunctionCallNode);
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// Arguments are not in tail position
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FNextIsTail := False;
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callee := Accept(Node.Callee).AsIntf<IAstNode>;
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args := AcceptNodes<IAstNode>(Node.Arguments);
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N.Callee := Accept(N.Callee);
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N.Arguments := AcceptNodes<IAstNode>(N.Arguments, function(Node: IAstNode): IAstNode begin exit(Node) end);
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// If TCO status changed, we MUST rebuild the node.
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var boundNode := (Node as TBoundFunctionCallNode);
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if (boundNode.IsTailCall <> isTailCall) or (callee <> Node.Callee) or (args <> Node.Arguments) then
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begin
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var newBoundCall := TBoundFunctionCallNode.Create(Node, callee, args, isTailCall);
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(newBoundCall as TAstNode).StaticType := (Node as TAstNode).StaticType;
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Result := TDataValue.FromIntf<IFunctionCallNode>(newBoundCall);
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end
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else
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Result := TDataValue.FromIntf<IFunctionCallNode>(Node); // No change
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// Mutate the node with the TCO status
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N.IsTailCall := isTailCall;
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Result := N;
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end;
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end.
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