Index: pkg/compiler/lib/src/js_model/closure_visitors.dart |
diff --git a/pkg/compiler/lib/src/js_model/closure_visitors.dart b/pkg/compiler/lib/src/js_model/closure_visitors.dart |
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+// Copyright (c) 2017, 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. |
+ |
+import 'package:kernel/ast.dart' as ir; |
+ |
+import '../closure.dart'; |
+import '../elements/entities.dart'; |
+import 'closure.dart'; |
+import '../kernel/element_map.dart'; |
+ |
+/// This builder walks the code to determine what variables are captured/free at |
+/// various points to build ClosureScope that can respond to queries |
+/// about how a particular variable is being used at any point in the code. |
+class ClosureScopeBuilder extends ir.Visitor { |
+ /// A map of each visited call node with the associated information about what |
+ /// variables are captured/used. Each ir.Node key corresponds to a scope that |
+ /// was encountered while visiting a closure (initially called through |
+ /// [translateLazyIntializer] or [translateConstructorOrProcedure]). |
+ Map<ir.Node, ClosureScope> _closureInfoMap = <ir.Node, ClosureScope>{}; |
+ |
+ /// A map of the nodes that we have flagged as necessary to generate closure |
+ /// classes for in a later stage. We map that node to information ascertained |
+ /// about variable usage in the surrounding scope. |
+ Map<ir.Node /* ir.Field | ir.FunctionNode */, ScopeInfo> _closuresToGenerate = |
+ <ir.Node, ScopeInfo>{}; |
+ |
+ /// The local variables that have been declared in the current scope. |
+ List<ir.VariableDeclaration> _scopeVariables; |
+ |
+ /// Pointer to the context in which this closure is executed. |
+ /// For example, in the expression `var foo = () => 3 + i;`, the executable |
+ /// context as we walk the nodes in that expression is the ir.Field `foo`. |
+ ir.Node _executableContext; |
+ |
+ /// A flag to indicate if we are currently inside a closure. |
+ bool _isInsideClosure = false; |
+ |
+ /// Pointer to the original node where this closure builder started. |
+ ir.Node _outermostNode; |
+ |
+ /// Keep track of the mutated local variables so that we don't need to box |
+ /// non-mutated variables. |
+ Set<ir.VariableDeclaration> _mutatedVariables = |
+ new Set<ir.VariableDeclaration>(); |
+ |
+ /// The set of variables that are accessed in some form, whether they are |
+ /// mutated or not. |
+ Set<ir.VariableDeclaration> _capturedVariables = |
+ new Set<ir.VariableDeclaration>(); |
+ |
+ /// If true, the visitor is currently traversing some nodes that are inside a |
+ /// try block. |
+ bool _inTry = false; |
+ |
+ /// Lookup the local entity that corresponds to a kernel variable declaration. |
+ final KernelToLocalsMap _localsMap; |
+ |
+ /// The current scope we are in. |
+ KernelScopeInfo _currentScopeInfo; |
+ |
+ final KernelToElementMap _kernelToElementMap; |
+ |
+ ClosureScopeBuilder(this._closureInfoMap, this._closuresToGenerate, |
+ this._localsMap, this._kernelToElementMap); |
+ |
+ /// Update the [ClosureScope] object corresponding to |
+ /// this node if any variables are captured. |
+ void attachCapturedScopeVariables(ir.Node node) { |
+ Set<Local> capturedVariablesForScope = new Set<Local>(); |
+ |
+ for (ir.VariableDeclaration variable in _scopeVariables) { |
+ // No need to box non-assignable elements. |
+ if (variable.isFinal || variable.isConst) continue; |
+ if (!_mutatedVariables.contains(variable)) continue; |
+ if (_capturedVariables.contains(variable)) { |
+ capturedVariablesForScope.add(_localsMap.getLocal(variable)); |
+ } |
+ } |
+ if (!capturedVariablesForScope.isEmpty) { |
+ ThisLocal thisLocal = null; |
+ if (node is ir.Member && node.isInstanceMember) { |
+ if (node is ir.Procedure) { |
+ thisLocal = new ThisLocal(_kernelToElementMap.getMethod(node)); |
+ } else if (node is ir.Field) { |
+ thisLocal = new ThisLocal(_kernelToElementMap.getField(node)); |
+ } |
+ } else if (node is ir.Constructor) { |
+ thisLocal = new ThisLocal(_kernelToElementMap.getConstructor(node)); |
+ } |
+ |
+ Entity context; |
+ if (_executableContext is ir.Member) { |
+ context = _kernelToElementMap.getMember(_executableContext); |
+ } else { |
+ context = _kernelToElementMap.getLocalFunction(_executableContext); |
+ } |
+ _closureInfoMap[node] = |
+ new KernelClosureScope(capturedVariablesForScope, context, thisLocal); |
+ } |
+ } |
+ |
+ /// Perform book-keeping with the current set of local variables that have |
+ /// been seen thus far before entering this new scope. |
+ void enterNewScope(ir.Node node, Function visitNewScope) { |
+ List<ir.VariableDeclaration> oldScopeVariables = _scopeVariables; |
+ _scopeVariables = <ir.VariableDeclaration>[]; |
+ visitNewScope(); |
+ attachCapturedScopeVariables(node); |
+ _mutatedVariables.removeAll(_scopeVariables); |
+ _scopeVariables = oldScopeVariables; |
+ } |
+ |
+ @override |
+ void defaultNode(ir.Node node) { |
+ node.visitChildren(this); |
+ } |
+ |
+ @override |
+ visitTryCatch(ir.TryCatch node) { |
+ bool oldInTry = _inTry; |
+ _inTry = true; |
+ node.visitChildren(this); |
+ _inTry = oldInTry; |
+ } |
+ |
+ @override |
+ visitTryFinally(ir.TryFinally node) { |
+ bool oldInTry = _inTry; |
+ _inTry = true; |
+ node.visitChildren(this); |
+ _inTry = oldInTry; |
+ } |
+ |
+ @override |
+ visitVariableGet(ir.VariableGet node) { |
+ _markVariableAsUsed(node.variable); |
+ } |
+ |
+ @override |
+ visitVariableSet(ir.VariableSet node) { |
+ _mutatedVariables.add(node.variable); |
+ _markVariableAsUsed(node.variable); |
+ node.visitChildren(this); |
+ } |
+ |
+ /// Add this variable to the set of free variables if appropriate and add to |
+ /// the tally of variables used in try or sync blocks. |
+ void _markVariableAsUsed(ir.VariableDeclaration variable) { |
+ if (_isInsideClosure && !_inCurrentContext(variable)) { |
+ // If the element is not declared in the current function and the element |
+ // is not the closure itself we need to mark the element as free variable. |
+ // Note that the check on [insideClosure] is not just an |
+ // optimization: factories have type parameters as function |
+ // parameters, and type parameters are declared in the class, not |
+ // the factory. |
+ _currentScopeInfo.freeVariables.add(variable); |
+ } |
+ if (_inTry) { |
+ _currentScopeInfo.localsUsedInTryOrSync |
+ .add(_localsMap.getLocal(variable)); |
+ } |
+ } |
+ |
+ @override |
+ void visitForStatement(ir.ForStatement node) { |
+ List<Local> boxedLoopVariables = <Local>[]; |
+ enterNewScope(node, () { |
+ // First visit initialized variables and update steps so we can easily |
+ // check if a loop variable was captured in one of these subexpressions. |
+ node.variables |
+ .forEach((ir.VariableDeclaration variable) => variable.accept(this)); |
+ node.updates |
+ .forEach((ir.Expression expression) => expression.accept(this)); |
+ |
+ // Loop variables that have not been captured yet can safely be flagged as |
+ // non-mutated, because no nested function can observe the mutation. |
+ for (ir.VariableDeclaration variable in node.variables) { |
+ if (!_capturedVariables.contains(variable)) { |
+ _mutatedVariables.remove(variable); |
+ } |
+ } |
+ |
+ // Visit condition and body. |
+ // This must happen after the above, so any loop variables mutated in the |
+ // condition or body are indeed flagged as mutated. |
+ if (node.condition != null) node.condition.accept(this); |
+ node.body.accept(this); |
+ |
+ // See if we have declared loop variables that need to be boxed. |
+ for (ir.VariableDeclaration variable in node.variables) { |
+ // Non-mutated variables should not be boxed. The _mutatedVariables set |
+ // gets cleared when `enterNewScope` returns, so check it here. |
+ if (_capturedVariables.contains(variable) && |
+ _mutatedVariables.contains(variable)) { |
+ boxedLoopVariables.add(_localsMap.getLocal(variable)); |
+ } |
+ } |
+ }); |
+ KernelClosureScope scope = _closureInfoMap[node]; |
+ if (scope == null) return; |
+ _closureInfoMap[node] = new KernelLoopClosureScope(scope.boxedVariables, |
+ boxedLoopVariables, scope.context, scope.thisLocal); |
+ } |
+ |
+ void visitInvokable(ir.TreeNode node) { |
+ bool oldIsInsideClosure = _isInsideClosure; |
+ ir.Node oldExecutableContext = _executableContext; |
+ KernelScopeInfo oldScopeInfo = _currentScopeInfo; |
+ |
+ // _outermostNode is only null the first time we enter the body of the |
+ // field, constructor, or method that is being analyzed. |
+ _isInsideClosure = _outermostNode != null; |
+ _executableContext = node; |
+ if (!_isInsideClosure) { |
+ _outermostNode = node; |
+ } |
+ _currentScopeInfo = new KernelScopeInfo(_nodeToThisLocal(node)); |
+ _closuresToGenerate[node] = _currentScopeInfo; |
+ |
+ enterNewScope(node, () { |
+ node.visitChildren(this); |
+ }); |
+ |
+ KernelScopeInfo savedScopeInfo = _currentScopeInfo; |
+ bool savedIsInsideClosure = _isInsideClosure; |
+ |
+ // Restore old values. |
+ _isInsideClosure = oldIsInsideClosure; |
+ _currentScopeInfo = oldScopeInfo; |
+ _executableContext = oldExecutableContext; |
+ |
+ // Mark all free variables as captured and expect to encounter them in the |
+ // outer function. |
+ Iterable<ir.VariableDeclaration> freeVariables = |
+ savedScopeInfo.freeVariables; |
+ assert(freeVariables.isEmpty || savedIsInsideClosure); |
+ for (ir.VariableDeclaration freeVariable in freeVariables) { |
+ assert(!_capturedVariables.contains(freeVariable)); |
+ _capturedVariables.add(freeVariable); |
+ _markVariableAsUsed(freeVariable); |
+ } |
+ } |
+ |
+ /// Return true if [variable]'s context is the same as the current executable |
+ /// context. |
+ bool _inCurrentContext(ir.VariableDeclaration variable) { |
+ ir.TreeNode node = variable; |
+ while (node != _outermostNode && node != _executableContext) { |
+ node = node.parent; |
+ } |
+ return node == _executableContext; |
+ } |
+ |
+ void translateLazyInitializer(ir.Field field) { |
+ visitInvokable(field); |
+ } |
+ |
+ void translateConstructorOrProcedure(ir.Node constructorOrProcedure) { |
+ constructorOrProcedure.accept(this); |
+ } |
+ |
+ void visitFunctionNode(ir.FunctionNode functionNode) { |
+ visitInvokable(functionNode); |
+ } |
+ |
+ /// If [node] is an instance member return the corresponding `this` reference. |
+ /// If not, return null. |
+ Entity _nodeToThisLocal( |
+ ir.TreeNode |
+ /*ir.Field|ir.FunctionNode|ir.Constructor|ir.Procedure*/ node) { |
+ ir.Node nodeToConvert = node; |
+ if (nodeToConvert is ir.Field) { |
+ if (!nodeToConvert.isInstanceMember) return null; |
+ return new ThisLocal(_kernelToElementMap.getField(nodeToConvert)); |
+ } else { |
+ if (nodeToConvert is ir.FunctionNode) { |
+ // Step up one node higher to find the corresponding entity for this |
+ // node. |
+ nodeToConvert = node.parent; |
+ } |
+ if (nodeToConvert is ir.Constructor || |
+ (nodeToConvert is ir.Procedure && |
+ nodeToConvert.kind == ir.ProcedureKind.Factory && |
+ nodeToConvert.isInstanceMember)) { |
+ return new ThisLocal(_kernelToElementMap.getConstructor(nodeToConvert)); |
+ } else if (nodeToConvert is ir.Procedure && |
+ nodeToConvert.isInstanceMember) { |
+ return new ThisLocal(_kernelToElementMap.getMethod(nodeToConvert)); |
+ } |
+ } |
+ return null; |
+ } |
+} |