Mirror of the BLOAT repository
https://www.cs.purdue.edu/homes/hosking/bloat/
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118 lines
2.8 KiB
118 lines
2.8 KiB
/*
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* All files in the distribution of BLOAT (Bytecode Level Optimization and
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* Analysis tool for Java(tm)) are Copyright 1997-2001 by the Purdue
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* Research Foundation of Purdue University. All rights reserved.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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package EDU.purdue.cs.bloat.tree;
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import java.util.*;
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import EDU.purdue.cs.bloat.editor.*;
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/**
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* An expression in which a definition occurs. Each instance has a unique
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* version number associated with it.
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*/
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public abstract class DefExpr extends Expr {
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Set uses; // Expressions in which the definition is used
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int version; // Which number DefExpr is this?
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static int next = 0; // Total number of DefExprs
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/**
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* Constructor.
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*
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* @param type
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* The Type (descriptor) of this expression
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*/
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public DefExpr(final Type type) {
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super(type);
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uses = new HashSet();
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version = DefExpr.next++;
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}
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/**
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* Clean up this expression. Notify all the expressions that use this
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* definition that it is no longer their defining expression.
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*/
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public void cleanupOnly() {
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super.cleanupOnly();
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final List a = new ArrayList(uses);
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uses.clear();
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final Iterator e = a.iterator();
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while (e.hasNext()) {
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final Expr use = (Expr) e.next();
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use.setDef(null);
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}
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}
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/**
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* Returns Number DefExpr this is. This is also the SSA version number of
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* the expression that this <tt>DefExpr</tt> defines.
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*/
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public int version() {
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return version;
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}
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/**
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* Determines whether or not this <tt>DefExpr</tt> defines a local
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* variable in its parent.
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*
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* @see Assign#defs
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*/
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public boolean isDef() {
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if (parent instanceof Assign) {
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final DefExpr[] defs = ((Assign) parent).defs();
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if (defs != null) {
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for (int i = 0; i < defs.length; i++) {
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if (defs[i] == this) {
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return true;
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}
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}
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}
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}
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return false;
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}
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/**
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* Returns the <tt>Expr</tt>s in which the variable defined by this are
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* used.
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*/
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public Collection uses() {
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return new HashSet(uses);
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}
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public boolean hasUse(final Expr use) {
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return uses.contains(use);
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}
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protected void addUse(final Expr use) {
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uses.add(use);
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}
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protected void removeUse(final Expr use) {
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uses.remove(use);
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}
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}
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