Linter Demo

Errors: 0

Warnings: 1

File: /home/fstrocco/Dart/dart/benchmark/compiler/lib/src/tree_ir/optimization/loop_rewriter.dart

// 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. part of tree_ir.optimization; /// Rewrites [WhileTrue] statements with an [If] body into a [WhileCondition], /// in situations where only one of the branches contains a [Continue] to the /// loop. Schematically: /// /// L: /// while (true) { /// if (E) { /// S1 (has references to L) /// } else { /// S2 (has no references to L) /// } /// } /// ==> /// L: /// while (E) { /// S1 /// }; /// S2 /// /// A similar transformation is used when S2 occurs in the 'then' position. /// /// Note that the above pattern needs no iteration since nested ifs /// have been collapsed previously in the [StatementRewriter] phase. class LoopRewriter extends RecursiveTransformer implements Pass { String get passName => 'Loop rewriter'; Set<Label> usedContinueLabels = new Set<Label>(); void rewrite(RootNode root) { root.replaceEachBody(visitStatement); } @override void visitInnerFunction(FunctionDefinition node) { node.body = new LoopRewriter().visitStatement(node.body); } Statement visitContinue(Continue node) { usedContinueLabels.add(node.target); return node; } Statement visitWhileTrue(WhileTrue node) { assert(!usedContinueLabels.contains(node.label)); if (node.body is If) { If body = node.body; body.thenStatement = visitStatement(body.thenStatement); bool thenHasContinue = usedContinueLabels.remove(node.label); body.elseStatement = visitStatement(body.elseStatement); bool elseHasContinue = usedContinueLabels.remove(node.label); if (thenHasContinue && !elseHasContinue) { node.label.binding = null; // Prepare to rebind the label. return new WhileCondition( node.label, body.condition, body.thenStatement, body.elseStatement); } else if (!thenHasContinue && elseHasContinue) { node.label.binding = null; return new WhileCondition( node.label, new Not(body.condition), body.elseStatement, body.thenStatement); } } else { node.body = visitStatement(node.body); usedContinueLabels.remove(node.label); } return node; } }