/* Soot - a J*va Optimization Framework
* Copyright (C) 2004 Jennifer Lhotak
*
* This library 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 library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
package soot.jimple.toolkits.annotation.logic;
import soot.*;
import soot.toolkits.graph.*;
import soot.jimple.*;
import java.util.*;
import soot.toolkits.scalar.*;
import soot.tagkit.*;
public class LoopInvariantFinder extends BodyTransformer {
private ArrayList constants;
public LoopInvariantFinder(Singletons.Global g){}
public static LoopInvariantFinder v() { return G.v().soot_jimple_toolkits_annotation_logic_LoopInvariantFinder();}
/**
* this one uses the side effect tester
*/
protected void internalTransform (Body b, String phaseName, Map options){
UnitGraph g = new ExceptionalUnitGraph(b);
LocalDefs sld = new SmartLocalDefs(g, new SimpleLiveLocals(g));
NaiveSideEffectTester nset = new NaiveSideEffectTester();
LoopFinder lf = new LoopFinder();
lf.internalTransform(b, phaseName, options);
Collection<Loop> loops = lf.loops();
constants = new ArrayList();
// no loop invariants if no loops
if (loops.isEmpty()) return;
Iterator<Loop> lIt = loops.iterator();
while (lIt.hasNext()){
Loop loop = lIt.next();
Stmt header = loop.getHead();
Collection<Stmt> loopStmts = loop.getLoopStatements();
Iterator<Stmt> bIt = loopStmts.iterator();
while (bIt.hasNext()){
Stmt tStmt = bIt.next();
//System.out.println("will test stmt: "+tStmt+" for loop header: "+header);
//System.out.println("will test with loop stmts: "+loopStmts);
handleLoopBodyStmt(tStmt, nset, loopStmts);
}
}
}
private void handleLoopBodyStmt(Stmt s, NaiveSideEffectTester nset, Collection<Stmt> loopStmts){
// need to do some checks for arrays - when there is an multi-dim array
// --> for defs there is a get of one of the dims that claims to be
// loop invariant
// handle constants
if (s instanceof DefinitionStmt) {
DefinitionStmt ds = (DefinitionStmt)s;
if (ds.getLeftOp() instanceof Local && ds.getRightOp() instanceof Constant){
if (!constants.contains(ds.getLeftOp())){
constants.add(ds.getLeftOp());
}
else {
constants.remove(ds.getLeftOp());
}
}
}
// ignore goto stmts
if (s instanceof GotoStmt) return;
// ignore invoke stmts
if (s instanceof InvokeStmt) return;
G.v().out.println("s : "+s+" use boxes: "+s.getUseBoxes()+" def boxes: "+s.getDefBoxes());
// just use boxes here
Iterator useBoxesIt = s.getUseBoxes().iterator();
boolean result = true;
uses: while (useBoxesIt.hasNext()){
ValueBox vb = (ValueBox)useBoxesIt.next();
Value v = vb.getValue();
//System.out.println("next vb: "+v+" is a: "+vb.getClass());
//System.out.println("next vb: "+v+" class is a: "+v.getClass());
// new's are not invariant
if (v instanceof NewExpr) {
result = false;
G.v().out.println("break uses: due to new expr");
break uses;
}
// invokes are not invariant
if (v instanceof InvokeExpr) {
result = false;
G.v().out.println("break uses: due to invoke expr");
break uses;
}
// side effect tester doesn't handle expr
if (v instanceof Expr) continue;
G.v().out.println("test: "+v+" of kind: "+v.getClass());
Iterator loopStmtsIt = loopStmts.iterator();
while (loopStmtsIt.hasNext()){
Stmt next = (Stmt)loopStmtsIt.next();
if (nset.unitCanWriteTo(next, v)){
if (!isConstant(next)){
G.v().out.println("result = false unit can be written to by: "+next);
result = false;
break uses;
}
}
}
}
Iterator defBoxesIt = s.getDefBoxes().iterator();
defs: while (defBoxesIt.hasNext()){
ValueBox vb = (ValueBox)defBoxesIt.next();
Value v = vb.getValue();
// new's are not invariant
if (v instanceof NewExpr) {
result = false;
G.v().out.println("break defs due to new");
break defs;
}
// invokes are not invariant
if (v instanceof InvokeExpr) {
result = false;
G.v().out.println("break defs due to invoke");
break defs;
}
// side effect tester doesn't handle expr
if (v instanceof Expr) continue;
G.v().out.println("test: "+v+" of kind: "+v.getClass());
Iterator loopStmtsIt = loopStmts.iterator();
while (loopStmtsIt.hasNext()){
Stmt next = (Stmt)loopStmtsIt.next();
if (next.equals(s)) continue;
if (nset.unitCanWriteTo(next, v)){
if (!isConstant(next)){
G.v().out.println("result false: unit can be written to by: "+next);
result = false;
break defs;
}
}
}
}
G.v().out.println("stmt: "+s+" result: "+result);
if (result){
s.addTag(new LoopInvariantTag("is loop invariant"));
s.addTag(new ColorTag(ColorTag.RED, "Loop Invariant Analysis"));
}
else {
// if loops are nested it might be invariant in one of them
// so remove tag
//if (s.hasTag("LoopInvariantTag")) {
// s.removeTag("LoopInvariantTag");
//}
}
}
private boolean isConstant(Stmt s){
if (s instanceof DefinitionStmt){
DefinitionStmt ds = (DefinitionStmt)s;
if (constants.contains(ds.getLeftOp())){
return true;
}
}
return false;
}
}