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A Java Optimization Framework
package soot.dava.toolkits.base.AST.traversals;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 2005 Nomair A. Naeem
* %%
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 2.1 of the
* License, or (at your option) any later version.
*
* This program 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 Lesser Public License for more details.
*
* You should have received a copy of the GNU General Lesser Public
* License along with this program. If not, see
* .
* #L%
*/
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import soot.Local;
import soot.Value;
import soot.ValueBox;
import soot.dava.internal.AST.ASTAggregatedCondition;
import soot.dava.internal.AST.ASTBinaryCondition;
import soot.dava.internal.AST.ASTCondition;
import soot.dava.internal.AST.ASTDoWhileNode;
import soot.dava.internal.AST.ASTForLoopNode;
import soot.dava.internal.AST.ASTIfElseNode;
import soot.dava.internal.AST.ASTIfNode;
import soot.dava.internal.AST.ASTMethodNode;
import soot.dava.internal.AST.ASTNode;
import soot.dava.internal.AST.ASTStatementSequenceNode;
import soot.dava.internal.AST.ASTSwitchNode;
import soot.dava.internal.AST.ASTSynchronizedBlockNode;
import soot.dava.internal.AST.ASTUnaryCondition;
import soot.dava.internal.AST.ASTWhileNode;
import soot.dava.internal.asg.AugmentedStmt;
import soot.dava.toolkits.base.AST.analysis.DepthFirstAdapter;
import soot.dava.toolkits.base.AST.structuredAnalysis.DavaFlowSet;
import soot.dava.toolkits.base.AST.structuredAnalysis.ReachingCopies;
import soot.jimple.DefinitionStmt;
import soot.jimple.Stmt;
/*
* TODO: shouldnt this be a transformation and hence under the transformation package???
This analysis uses the results from
1 ReachingCopies
2 uD and dU chains
to eliminate extra copies
ALGORITHM:
When you encounter a copy stmt (a=b) find all uses of local a (using dU chain)
if For ALL uses the ReachingCopies set contains copy stmt (a=b)
Remove Copy Stmt
Replace use of a with use of b
Note:
copy stmts can be encountered in:
a, ASTStatementSequenceNode
b, for loop init -------> dont want to remove this
c, for loop update ---------> dont want to remove this
*/
public class CopyPropagation extends DepthFirstAdapter {
public static boolean DEBUG = false;
ASTNode AST;
ASTUsesAndDefs useDefs;
ReachingCopies reachingCopies;
ASTParentNodeFinder parentOf;
boolean someCopyStmtModified;
// need to keep track of whenever we modify the AST
// this flag is set to true whenever a stmt is removed or a local
// substituted for another
boolean ASTMODIFIED;
public CopyPropagation(ASTNode AST) {
super();
someCopyStmtModified = false;
this.AST = AST;
ASTMODIFIED = false;
setup();
}
public CopyPropagation(boolean verbose, ASTNode AST) {
super(verbose);
someCopyStmtModified = false;
this.AST = AST;
ASTMODIFIED = false;
setup();
}
private void setup() {
// create the uD and dU chains
if (DEBUG) {
System.out.println("computing usesAnd Defs");
}
useDefs = new ASTUsesAndDefs(AST);
AST.apply(useDefs);
if (DEBUG) {
System.out.println("computing usesAnd Defs....done");
}
// apply the reaching copies Structural flow Analysis
reachingCopies = new ReachingCopies(AST);
parentOf = new ASTParentNodeFinder();
AST.apply(parentOf);
}
/*
* If any copy stmt was removed or any substitution made we might be able to get better results by redoing the analysis
*/
public void outASTMethodNode(ASTMethodNode node) {
if (ASTMODIFIED) {
// need to rerun copy prop
// before running a structured flow analysis have to do this one
AST.apply(ClosestAbruptTargetFinder.v());
// System.out.println("\n\n\nCOPY PROP\n\n\n\n");
CopyPropagation prop1 = new CopyPropagation(AST);
AST.apply(prop1);
}
}
public void inASTStatementSequenceNode(ASTStatementSequenceNode node) {
for (AugmentedStmt as : node.getStatements()) {
Stmt s = as.get_Stmt();
if (isCopyStmt(s)) {
handleCopyStmt((DefinitionStmt) s);
}
}
}
/*
* Method returns true if s is a copy stmt i.e. a = b where a and b are both locals
*/
public boolean isCopyStmt(Stmt s) {
if (!(s instanceof DefinitionStmt)) {
// only definition stmts can be copy stmts
return false;
}
// x = expr;
// check if expr is a local in which case this is a copy
Value leftOp = ((DefinitionStmt) s).getLeftOp();
Value rightOp = ((DefinitionStmt) s).getRightOp();
if (leftOp instanceof Local && rightOp instanceof Local) {
// this is a copy statement
return true;
}
return false;
}
/*
* Given a copy stmt (a=b) find all uses of local a (using dU chain)
*
* if For ALL uses the ReachingCopies set contains copy stmt (a=b) Remove Copy Stmt Replace use of a with use of b
*/
public void handleCopyStmt(DefinitionStmt copyStmt) {
// System.out.println("COPY STMT FOUND-----------------------------------"+copyStmt);
// get defined local...safe to cast since this is copyStmt
Local definedLocal = (Local) copyStmt.getLeftOp();
// get all uses of this local from the dU chain
Object temp = useDefs.getDUChain(copyStmt);
ArrayList uses = new ArrayList();
if (temp != null) {
uses = (ArrayList) temp;
}
// the uses list contains all stmts / nodes which use the definedLocal
// check if uses is non-empty
if (uses.size() != 0) {
if (DEBUG) {
System.out.println(">>>>The defined local:" + definedLocal + " is used in the following");
System.out.println("\n numof uses:" + uses.size() + uses + ">>>>>>>>>>>>>>>\n\n");
}
// continuing with copy propagation algorithm
// create localPair for copy stmt in question...same to cast as its
// a copyStmt
Local leftLocal = (Local) copyStmt.getLeftOp();
Local rightLocal = (Local) copyStmt.getRightOp();
ReachingCopies.LocalPair localPair = reachingCopies.new LocalPair(leftLocal, rightLocal);
// check for all the non zero uses
Iterator useIt = uses.iterator();
while (useIt.hasNext()) {
// check that the reaching copies of each use has the copy stmt
// a use is either a statement or a node(condition, synch,
// switch , for etc)
Object tempUse = useIt.next();
DavaFlowSet reaching = reachingCopies.getReachingCopies(tempUse);
if (!reaching.contains(localPair)) {
// this copy stmt does not reach this use
// no copy elimination can be done
return;
}
}
// if we get here that means that the copy stmt reached each use
// replace each use of a with b
useIt = uses.iterator();
while (useIt.hasNext()) {
Object tempUse = useIt.next();
if (DEBUG) {
System.out.println("copy stmt reached this use" + tempUse);
}
replace(leftLocal, rightLocal, tempUse);
}
// remove copy stmt a=b
removeStmt(copyStmt);
if (someCopyStmtModified) {
// get all the analyses re-set
setup();
someCopyStmtModified = false;
}
} else {
// the copy stmt is usesless since the definedLocal is not being
// used anywhere after definition
// System.out.println("The defined local:"+definedLocal+" is not used anywhere");
removeStmt(copyStmt);
}
}
public void removeStmt(Stmt stmt) {
Object tempParent = parentOf.getParentOf(stmt);
if (tempParent == null) {
// System.out.println("NO PARENT FOUND CANT DO ANYTHING");
return;
}
// parents are always ASTNodes, hence safe to cast
ASTNode parent = (ASTNode) tempParent;
// REMOVING STMT
if (!(parent instanceof ASTStatementSequenceNode)) {
// parent of a statement should always be a ASTStatementSequenceNode
throw new RuntimeException("Found a stmt whose parent is not an ASTStatementSequenceNode");
}
ASTStatementSequenceNode parentNode = (ASTStatementSequenceNode) parent;
ArrayList newSequence = new ArrayList();
for (AugmentedStmt as : parentNode.getStatements()) {
Stmt s = as.get_Stmt();
if (s.toString().compareTo(stmt.toString()) != 0) {
// this is not the stmt to be removed
newSequence.add(as);
}
}
// System.out.println("STMT REMOVED---------------->"+stmt);
parentNode.setStatements(newSequence);
ASTMODIFIED = true;
return;
}
/*
* Method goes depth first into the condition tree and finds any use of local "from" If it finds the use it replaces it
* with the use of local "to"
*/
public void modifyUses(Local from, Local to, ASTCondition cond) {
if (cond instanceof ASTAggregatedCondition) {
// ArrayList useList = new ArrayList();
modifyUses(from, to, ((ASTAggregatedCondition) cond).getLeftOp());
modifyUses(from, to, ((ASTAggregatedCondition) cond).getRightOp());
} else if (cond instanceof ASTUnaryCondition) {
// get uses from unary condition
Value val = ((ASTUnaryCondition) cond).getValue();
if (val instanceof Local) {
Local local = (Local) val;
if (local.getName().compareTo(from.getName()) == 0) {
// replace the name with the one in "to"
((ASTUnaryCondition) cond).setValue(to);
ASTMODIFIED = true;
}
} else {
Iterator it = val.getUseBoxes().iterator();
while (it.hasNext()) {
ValueBox valBox = (ValueBox) it.next();
Value tempVal = valBox.getValue();
if (tempVal instanceof Local) {
Local local = (Local) tempVal;
if (local.getName().compareTo(from.getName()) == 0) {
// replace the name with the one in "to"
valBox.setValue(to);
ASTMODIFIED = true;
}
}
}
}
} // end unary condition
else if (cond instanceof ASTBinaryCondition) {
// get uses from binaryCondition
Value val = ((ASTBinaryCondition) cond).getConditionExpr();
Iterator it = val.getUseBoxes().iterator();
while (it.hasNext()) {
ValueBox valBox = (ValueBox) it.next();
Value tempVal = valBox.getValue();
if (tempVal instanceof Local) {
Local local = (Local) tempVal;
if (local.getName().compareTo(from.getName()) == 0) {
// replace the name with the one in "to"
valBox.setValue(to);
ASTMODIFIED = true;
}
}
}
} else {
throw new RuntimeException("Method getUseList in CopyPropagation encountered unknown condition type");
}
}
public void modifyUseBoxes(Local from, Local to, List useBoxes) {
Iterator it = useBoxes.iterator();
while (it.hasNext()) {
ValueBox valBox = (ValueBox) it.next();
Value tempVal = valBox.getValue();
if (tempVal instanceof Local) {
Local local = (Local) tempVal;
if (local.getName().compareTo(from.getName()) == 0) {
// replace the name with the one in "to"
valBox.setValue(to);
ASTMODIFIED = true;
}
}
}
}
/*
* Invoked by handleCopyStmt to replace the use of local to the use of local in © 2015 - 2025 Weber Informatics LLC | Privacy Policy