| // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| library tree_ir_builder; |
| |
| import '../dart2jslib.dart' as dart2js; |
| import '../dart_types.dart'; |
| import '../elements/elements.dart'; |
| import '../cps_ir/cps_ir_nodes.dart' as cps_ir; |
| import 'tree_ir_nodes.dart'; |
| |
| /** |
| * Builder translates from CPS-based IR to direct-style Tree. |
| * |
| * A call `Invoke(fun, cont, args)`, where cont is a singly-referenced |
| * non-exit continuation `Cont(v, body)` is translated into a direct-style call |
| * whose value is bound in the continuation body: |
| * |
| * `LetVal(v, Invoke(fun, args), body)` |
| * |
| * and the continuation definition is eliminated. A similar translation is |
| * applied to continuation invocations where the continuation is |
| * singly-referenced, though such invocations should not appear in optimized |
| * IR. |
| * |
| * A call `Invoke(fun, cont, args)`, where cont is multiply referenced, is |
| * translated into a call followed by a jump with an argument: |
| * |
| * `Jump L(Invoke(fun, args))` |
| * |
| * and the continuation is translated into a named block that takes an |
| * argument: |
| * |
| * `LetLabel(L, v, body)` |
| * |
| * Block arguments are later replaced with data flow during the Tree-to-Tree |
| * translation out of SSA. Jumps are eliminated during the Tree-to-Tree |
| * control-flow recognition. |
| * |
| * Otherwise, the output of Builder looks very much like the input. In |
| * particular, intermediate values and blocks used for local control flow are |
| * still all named. |
| */ |
| class Builder extends cps_ir.Visitor<Node> { |
| final dart2js.Compiler compiler; |
| |
| /// Maps variable/parameter elements to the Tree variables that represent it. |
| final Map<Element, List<Variable>> element2variables = |
| <Element,List<Variable>>{}; |
| |
| /// Like [element2variables], except for closure variables. Closure variables |
| /// are not subject to SSA, so at most one variable is used per local. |
| final Map<Local, Variable> local2closure = <Local, Variable>{}; |
| |
| // Continuations with more than one use are replaced with Tree labels. This |
| // is the mapping from continuations to labels. |
| final Map<cps_ir.Continuation, Label> labels = <cps_ir.Continuation, Label>{}; |
| |
| FunctionDefinition function; |
| cps_ir.Continuation returnContinuation; |
| |
| Builder parent; |
| |
| Builder(this.compiler); |
| |
| Builder.inner(Builder parent) |
| : this.parent = parent, |
| compiler = parent.compiler; |
| |
| /// Variable used in [buildPhiAssignments] as a temporary when swapping |
| /// variables. |
| Variable phiTempVar; |
| |
| Variable getClosureVariable(Local local) { |
| if (local.executableContext != function.element) { |
| return parent.getClosureVariable(local); |
| } |
| Variable variable = local2closure[local]; |
| if (variable == null) { |
| variable = new Variable(function, local); |
| local2closure[local] = variable; |
| } |
| return variable; |
| } |
| |
| /// Obtains the variable representing the given primitive. Returns null for |
| /// primitives that have no reference and do not need a variable. |
| Variable getVariable(cps_ir.Primitive primitive) { |
| if (primitive.registerIndex == null) { |
| return null; // variable is unused |
| } |
| List<Variable> variables = element2variables[primitive.hint]; |
| if (variables == null) { |
| variables = <Variable>[]; |
| element2variables[primitive.hint] = variables; |
| } |
| while (variables.length <= primitive.registerIndex) { |
| variables.add(new Variable(function, primitive.hint)); |
| } |
| return variables[primitive.registerIndex]; |
| } |
| |
| /// Obtains a reference to the tree Variable corresponding to the IR primitive |
| /// referred to by [reference]. |
| /// This increments the reference count for the given variable, so the |
| /// returned expression must be used in the tree. |
| Expression getVariableReference(cps_ir.Reference reference) { |
| Variable variable = getVariable(reference.definition); |
| if (variable == null) { |
| compiler.internalError( |
| compiler.currentElement, |
| "Reference to ${reference.definition} has no register"); |
| } |
| ++variable.readCount; |
| return variable; |
| } |
| |
| FunctionDefinition build(cps_ir.FunctionDefinition node) { |
| visit(node); |
| return function; |
| } |
| |
| List<Expression> translateArguments(List<cps_ir.Reference> args) { |
| return new List<Expression>.generate(args.length, |
| (int index) => getVariableReference(args[index])); |
| } |
| |
| List<Variable> translatePhiArguments(List<cps_ir.Reference> args) { |
| return new List<Variable>.generate(args.length, |
| (int index) => getVariableReference(args[index])); |
| } |
| |
| Statement buildContinuationAssignment( |
| cps_ir.Parameter parameter, |
| Expression argument, |
| Statement buildRest()) { |
| Variable variable = getVariable(parameter); |
| Statement assignment; |
| if (variable == null) { |
| assignment = new ExpressionStatement(argument, null); |
| } else { |
| assignment = new Assign(variable, argument, null); |
| } |
| assignment.next = buildRest(); |
| return assignment; |
| } |
| |
| /// Simultaneously assigns each argument to the corresponding parameter, |
| /// then continues at the statement created by [buildRest]. |
| Statement buildPhiAssignments( |
| List<cps_ir.Parameter> parameters, |
| List<Variable> arguments, |
| Statement buildRest()) { |
| assert(parameters.length == arguments.length); |
| // We want a parallel assignment to all parameters simultaneously. |
| // Since we do not have parallel assignments in dart_tree, we must linearize |
| // the assignments without attempting to read a previously-overwritten |
| // value. For example {x,y = y,x} cannot be linearized to {x = y; y = x}, |
| // for this we must introduce a temporary variable: {t = x; x = y; y = t}. |
| |
| // [rightHand] is the inverse of [arguments], that is, it maps variables |
| // to the assignments on which is occurs as the right-hand side. |
| Map<Variable, List<int>> rightHand = <Variable, List<int>>{}; |
| for (int i = 0; i < parameters.length; i++) { |
| Variable param = getVariable(parameters[i]); |
| Variable arg = arguments[i]; |
| if (param == null || param == arg) { |
| continue; // No assignment necessary. |
| } |
| List<int> list = rightHand[arg]; |
| if (list == null) { |
| rightHand[arg] = list = <int>[]; |
| } |
| list.add(i); |
| } |
| |
| Statement first, current; |
| void addAssignment(Variable dst, Variable src) { |
| if (first == null) { |
| first = current = new Assign(dst, src, null); |
| } else { |
| current = current.next = new Assign(dst, src, null); |
| } |
| } |
| |
| List<Variable> assignmentSrc = new List<Variable>(parameters.length); |
| List<bool> done = new List<bool>(parameters.length); |
| void visitAssignment(int i) { |
| if (done[i] == true) { |
| return; |
| } |
| Variable param = getVariable(parameters[i]); |
| Variable arg = arguments[i]; |
| if (param == null || param == arg) { |
| return; // No assignment necessary. |
| } |
| if (assignmentSrc[i] != null) { |
| // Cycle found; store argument in a temporary variable. |
| // The temporary will then be used as right-hand side when the |
| // assignment gets added. |
| if (assignmentSrc[i] != phiTempVar) { // Only move to temporary once. |
| assignmentSrc[i] = phiTempVar; |
| addAssignment(phiTempVar, arg); |
| } |
| return; |
| } |
| assignmentSrc[i] = arg; |
| List<int> paramUses = rightHand[param]; |
| if (paramUses != null) { |
| for (int useIndex in paramUses) { |
| visitAssignment(useIndex); |
| } |
| } |
| addAssignment(param, assignmentSrc[i]); |
| done[i] = true; |
| } |
| |
| for (int i = 0; i < parameters.length; i++) { |
| if (done[i] == null) { |
| visitAssignment(i); |
| } |
| } |
| |
| if (first == null) { |
| first = buildRest(); |
| } else { |
| current.next = buildRest(); |
| } |
| return first; |
| } |
| |
| visitNode(cps_ir.Node node) => throw "Unhandled node: $node"; |
| |
| Expression visitFunctionDefinition(cps_ir.FunctionDefinition node) { |
| List<Variable> parameters = <Variable>[]; |
| function = new FunctionDefinition(node.element, parameters, |
| null, node.localConstants, node.defaultParameterValues); |
| returnContinuation = node.returnContinuation; |
| for (cps_ir.Parameter p in node.parameters) { |
| Variable parameter = getVariable(p); |
| assert(parameter != null); |
| ++parameter.writeCount; // Being a parameter counts as a write. |
| parameters.add(parameter); |
| } |
| if (!node.isAbstract) { |
| phiTempVar = new Variable(function, null); |
| function.body = visit(node.body); |
| } |
| return null; |
| } |
| |
| Statement visitLetPrim(cps_ir.LetPrim node) { |
| Variable variable = getVariable(node.primitive); |
| |
| // Don't translate unused primitives. |
| if (variable == null) return visit(node.body); |
| |
| Node definition = visit(node.primitive); |
| |
| // visitPrimitive returns a Statement without successor if it cannot occur |
| // in expression context (currently only the case for FunctionDeclarations). |
| if (definition is Statement) { |
| definition.next = visit(node.body); |
| return definition; |
| } else { |
| return new Assign(variable, definition, visit(node.body)); |
| } |
| } |
| |
| Statement visitLetCont(cps_ir.LetCont node) { |
| Label label; |
| if (node.continuation.hasMultipleUses) { |
| label = new Label(); |
| labels[node.continuation] = label; |
| } |
| Statement body = visit(node.body); |
| // The continuation's body is not always translated directly here because |
| // it may have been already translated: |
| // * For singly-used continuations, the continuation's body is |
| // translated at the site of the continuation invocation. |
| // * For recursive continuations, there is a single non-recursive |
| // invocation. The continuation's body is translated at the site |
| // of the non-recursive continuation invocation. |
| // See visitInvokeContinuation for the implementation. |
| if (label == null || node.continuation.isRecursive) return body; |
| return new LabeledStatement(label, body, visit(node.continuation.body)); |
| } |
| |
| Statement visitInvokeStatic(cps_ir.InvokeStatic node) { |
| // Calls are translated to direct style. |
| List<Expression> arguments = translateArguments(node.arguments); |
| Expression invoke = new InvokeStatic(node.target, node.selector, arguments); |
| return continueWithExpression(node.continuation, invoke); |
| } |
| |
| Statement visitInvokeMethod(cps_ir.InvokeMethod node) { |
| Expression receiver = getVariableReference(node.receiver); |
| List<Expression> arguments = translateArguments(node.arguments); |
| Expression invoke = new InvokeMethod(receiver, node.selector, arguments); |
| return continueWithExpression(node.continuation, invoke); |
| } |
| |
| Statement visitInvokeSuperMethod(cps_ir.InvokeSuperMethod node) { |
| List<Expression> arguments = translateArguments(node.arguments); |
| Expression invoke = new InvokeSuperMethod(node.selector, arguments); |
| return continueWithExpression(node.continuation, invoke); |
| } |
| |
| Statement visitConcatenateStrings(cps_ir.ConcatenateStrings node) { |
| List<Expression> arguments = translateArguments(node.arguments); |
| Expression concat = new ConcatenateStrings(arguments); |
| return continueWithExpression(node.continuation, concat); |
| } |
| |
| Statement continueWithExpression(cps_ir.Reference continuation, |
| Expression expression) { |
| cps_ir.Continuation cont = continuation.definition; |
| if (cont == returnContinuation) { |
| return new Return(expression); |
| } else { |
| assert(cont.parameters.length == 1); |
| Function nextBuilder = cont.hasExactlyOneUse ? |
| () => visit(cont.body) : () => new Break(labels[cont]); |
| return buildContinuationAssignment(cont.parameters.single, expression, |
| nextBuilder); |
| } |
| } |
| |
| Expression visitGetClosureVariable(cps_ir.GetClosureVariable node) { |
| return getClosureVariable(node.variable); |
| } |
| |
| Statement visitSetClosureVariable(cps_ir.SetClosureVariable node) { |
| Variable variable = getClosureVariable(node.variable); |
| Expression value = getVariableReference(node.value); |
| return new Assign(variable, value, visit(node.body), |
| isDeclaration: node.isDeclaration); |
| } |
| |
| Statement visitDeclareFunction(cps_ir.DeclareFunction node) { |
| Variable variable = getClosureVariable(node.variable); |
| FunctionDefinition function = makeSubFunction(node.definition); |
| return new FunctionDeclaration(variable, function, visit(node.body)); |
| } |
| |
| Statement visitTypeOperator(cps_ir.TypeOperator node) { |
| Expression receiver = getVariableReference(node.receiver); |
| Expression concat = new TypeOperator(receiver, node.type, node.operator); |
| return continueWithExpression(node.continuation, concat); |
| } |
| |
| Statement visitInvokeConstructor(cps_ir.InvokeConstructor node) { |
| List<Expression> arguments = translateArguments(node.arguments); |
| Expression invoke = |
| new InvokeConstructor(node.type, node.target, node.selector, arguments); |
| return continueWithExpression(node.continuation, invoke); |
| } |
| |
| Statement visitInvokeContinuation(cps_ir.InvokeContinuation node) { |
| // Invocations of the return continuation are translated to returns. |
| // Other continuation invocations are replaced with assignments of the |
| // arguments to formal parameter variables, followed by the body if |
| // the continuation is singly reference or a break if it is multiply |
| // referenced. |
| cps_ir.Continuation cont = node.continuation.definition; |
| if (cont == returnContinuation) { |
| assert(node.arguments.length == 1); |
| return new Return(getVariableReference(node.arguments.single)); |
| } else { |
| List<Expression> arguments = translatePhiArguments(node.arguments); |
| return buildPhiAssignments(cont.parameters, arguments, |
| () { |
| // Translate invocations of recursive and non-recursive |
| // continuations differently. |
| // * Non-recursive continuations |
| // - If there is one use, translate the continuation body |
| // inline at the invocation site. |
| // - If there are multiple uses, translate to Break. |
| // * Recursive continuations |
| // - There is a single non-recursive invocation. Translate |
| // the continuation body inline as a labeled loop at the |
| // invocation site. |
| // - Translate the recursive invocations to Continue. |
| if (cont.isRecursive) { |
| return node.isRecursive |
| ? new Continue(labels[cont]) |
| : new WhileTrue(labels[cont], visit(cont.body)); |
| } else { |
| return cont.hasExactlyOneUse |
| ? visit(cont.body) |
| : new Break(labels[cont]); |
| } |
| }); |
| } |
| } |
| |
| Statement visitBranch(cps_ir.Branch node) { |
| Expression condition = visit(node.condition); |
| Statement thenStatement, elseStatement; |
| cps_ir.Continuation cont = node.trueContinuation.definition; |
| assert(cont.parameters.isEmpty); |
| thenStatement = |
| cont.hasExactlyOneUse ? visit(cont.body) : new Break(labels[cont]); |
| cont = node.falseContinuation.definition; |
| assert(cont.parameters.isEmpty); |
| elseStatement = |
| cont.hasExactlyOneUse ? visit(cont.body) : new Break(labels[cont]); |
| return new If(condition, thenStatement, elseStatement); |
| } |
| |
| Expression visitConstant(cps_ir.Constant node) { |
| return new Constant(node.expression); |
| } |
| |
| Expression visitThis(cps_ir.This node) { |
| return new This(); |
| } |
| |
| Expression visitReifyTypeVar(cps_ir.ReifyTypeVar node) { |
| return new ReifyTypeVar(node.typeVariable); |
| } |
| |
| Expression visitLiteralList(cps_ir.LiteralList node) { |
| return new LiteralList( |
| node.type, |
| translateArguments(node.values)); |
| } |
| |
| Expression visitLiteralMap(cps_ir.LiteralMap node) { |
| return new LiteralMap( |
| node.type, |
| translateArguments(node.keys), |
| translateArguments(node.values)); |
| } |
| |
| FunctionDefinition makeSubFunction(cps_ir.FunctionDefinition function) { |
| return new Builder.inner(this).build(function); |
| } |
| |
| Node visitCreateFunction(cps_ir.CreateFunction node) { |
| FunctionDefinition def = makeSubFunction(node.definition); |
| FunctionType type = node.definition.element.type; |
| bool hasReturnType = !type.returnType.treatAsDynamic; |
| if (hasReturnType) { |
| // This function cannot occur in expression context. |
| // The successor will be filled in by visitLetPrim. |
| return new FunctionDeclaration(getVariable(node), def, null); |
| } else { |
| return new FunctionExpression(def); |
| } |
| } |
| |
| Expression visitParameter(cps_ir.Parameter node) { |
| // Continuation parameters are not visited (continuations themselves are |
| // not visited yet). |
| compiler.internalError(compiler.currentElement, 'Unexpected IR node.'); |
| return null; |
| } |
| |
| Expression visitContinuation(cps_ir.Continuation node) { |
| // Until continuations with multiple uses are supported, they are not |
| // visited. |
| compiler.internalError(compiler.currentElement, 'Unexpected IR node.'); |
| return null; |
| } |
| |
| Expression visitIsTrue(cps_ir.IsTrue node) { |
| return getVariableReference(node.value); |
| } |
| } |
| |