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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package jdk.nashorn.internal.ir;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import jdk.nashorn.internal.codegen.Label;
/**
* A loop node, for example a while node, do while node or for node
*/
public abstract class LoopNode extends BreakableStatement {
private static final long serialVersionUID = 1L;
/** loop continue label. */
protected final Label continueLabel;
/** Loop test node, null if infinite */
protected final JoinPredecessorExpression test;
/** Loop body */
protected final Block body;
/** Can control flow escape from loop, e.g. through breaks or continues to outer loops? */
protected final boolean controlFlowEscapes;
/**
* Constructor
*
* @param lineNumber lineNumber
* @param token token
* @param finish finish
* @param body loop body
* @param test test
* @param controlFlowEscapes controlFlowEscapes
*/
protected LoopNode(final int lineNumber, final long token, final int finish, final Block body, final JoinPredecessorExpression test, final boolean controlFlowEscapes) {
super(lineNumber, token, finish, new Label("while_break"));
this.continueLabel = new Label("while_continue");
this.body = body;
this.controlFlowEscapes = controlFlowEscapes;
this.test = test;
}
/**
* Constructor
*
* @param loopNode loop node
* @param test new test
* @param body new body
* @param controlFlowEscapes controlFlowEscapes
* @param conversion the local variable conversion carried by this loop node.
*/
protected LoopNode(final LoopNode loopNode, final JoinPredecessorExpression test, final Block body,
final boolean controlFlowEscapes, final LocalVariableConversion conversion) {
super(loopNode, conversion);
this.continueLabel = new Label(loopNode.continueLabel);
this.test = test;
this.body = body;
this.controlFlowEscapes = controlFlowEscapes;
}
@Override
public abstract Node ensureUniqueLabels(final LexicalContext lc);
/**
* Does the control flow escape from this loop, i.e. through breaks or
* continues to outer loops?
* @return true if control flow escapes
*/
public boolean controlFlowEscapes() {
return controlFlowEscapes;
}
@Override
public boolean isTerminal() {
if (!mustEnter()) {
return false;
}
//must enter but control flow may escape - then not terminal
if (controlFlowEscapes) {
return false;
}
//must enter, but body ends with return - then terminal
if (body.isTerminal()) {
return true;
}
//no breaks or returns, it is still terminal if we can never exit
return test == null;
}
/**
* Conservative check: does this loop have to be entered?
* @return true if body will execute at least once
*/
public abstract boolean mustEnter();
/**
* Get the continue label for this while node, i.e. location to go to on continue
* @return continue label
*/
public Label getContinueLabel() {
return continueLabel;
}
@Override
public List<Label> getLabels() {
return Collections.unmodifiableList(Arrays.asList(breakLabel, continueLabel));
}
@Override
public boolean isLoop() {
return true;
}
/**
* Get the body for this for node
* @return the body
*/
public abstract Block getBody();
/**
* @param lc lexical context
* @param body new body
* @return new for node if changed or existing if not
*/
public abstract LoopNode setBody(final LexicalContext lc, final Block body);
/**
* Get the test for this for node
* @return the test
*/
public final JoinPredecessorExpression getTest() {
return test;
}
/**
* Set the test for this for node
*
* @param lc lexical context
* @param test new test
* @return same or new node depending on if test was changed
*/
public abstract LoopNode setTest(final LexicalContext lc, final JoinPredecessorExpression test);
/**
* Set the control flow escapes flag for this node.
* TODO - integrate this with Lowering in a better way
*
* @param lc lexical context
* @param controlFlowEscapes control flow escapes value
* @return new loop node if changed otherwise the same
*/
public abstract LoopNode setControlFlowEscapes(final LexicalContext lc, final boolean controlFlowEscapes);
/**
* Does this loop have a LET declaration and hence require a per-iteration scope?
* @return true if a per-iteration scope is required.
*/
public abstract boolean hasPerIterationScope();
}