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/* Soot - a J*va Optimization Framework
* Copyright (C) 2002 Florian Loitsch
*
* 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.
*/
/*
* Modified by the Sable Research Group and others 1997-1999.
* See the 'credits' file distributed with Soot for the complete list of
* contributors. (Soot is distributed at http://www.sable.mcgill.ca/soot)
*/
package soot.jimple.toolkits.scalar.pre;
import soot.options.*;
import soot.jimple.toolkits.graph.*;
import soot.jimple.toolkits.scalar.*;
import soot.*;
import soot.toolkits.scalar.*;
import soot.toolkits.graph.*;
import soot.jimple.*;
import java.util.*;
import soot.util.*;
import soot.jimple.toolkits.pointer.PASideEffectTester;
import soot.options.BCMOptions;
/**
* Performs a partial redundancy elimination (= code motion). This is
* done, by moving everycomputation as high as possible (it is
* easy to show, that they are computationally optimal), and then
* replacing the original computation by a reference to this new high
* computation. This implies, that we introduce many new
* helper-variables (that can easily be eliminated afterwards). In
* order to catch every redundant expression, this transformation must
* be done on a graph without critical edges. Therefore the first
* thing we do, is removing them. A subsequent pass can then easily
* remove the synthetic nodes we have introduced. The term "busy"
* refers to the fact, that we always move computations as high
* as possible. Even, if this is not necessary.
*
* @see soot.jimple.toolkits.graph.CriticalEdgeRemover
*/
public class BusyCodeMotion extends BodyTransformer {
public BusyCodeMotion( Singletons.Global g ) {}
public static BusyCodeMotion v() { return G.v().soot_jimple_toolkits_scalar_pre_BusyCodeMotion(); }
private static final String PREFIX = "$bcm";
/**
* performs the busy code motion.
*/
protected void internalTransform(Body b, String phaseName, Map opts) {
BCMOptions options = new BCMOptions( opts );
HashMap expToHelper = new HashMap();
Chain unitChain = b.getUnits();
if(Options.v().verbose())
G.v().out.println("[" + b.getMethod().getName() +
"] performing Busy Code Motion...");
CriticalEdgeRemover.v().transform(b, phaseName + ".cer");
UnitGraph graph = new BriefUnitGraph(b);
/* map each unit to its RHS. only take binary expressions */
Map unitToEquivRhs = new UnitMap(b, graph.size() + 1, 0.7f) {
protected Object mapTo(Unit unit) {
Value tmp = SootFilter.noInvokeRhs(unit);
Value tmp2 = SootFilter.binop(tmp);
if (tmp2 == null) tmp2 = SootFilter.concreteRef(tmp);
return SootFilter.equiVal(tmp2);
}
};
/* same as before, but without exception-throwing expressions */
Map unitToNoExceptionEquivRhs = new UnitMap(b, graph.size() + 1, 0.7f) {
protected Object mapTo(Unit unit) {
Value tmp = SootFilter.binopRhs(unit);
tmp = SootFilter.noExceptionThrowing(tmp);
return SootFilter.equiVal(tmp);
}
};
/* if a more precise sideeffect-tester comes out, please change it here! */
SideEffectTester sideEffect;
if( Scene.v().hasCallGraph() && !options.naive_side_effect() ) {
sideEffect = new PASideEffectTester();
} else {
sideEffect = new NaiveSideEffectTester();
}
sideEffect.newMethod( b.getMethod() );
UpSafetyAnalysis upSafe = new UpSafetyAnalysis(graph, unitToEquivRhs,
sideEffect );
DownSafetyAnalysis downSafe = new DownSafetyAnalysis(graph,
unitToNoExceptionEquivRhs, sideEffect );
EarliestnessComputation earliest = new EarliestnessComputation(graph,
upSafe, downSafe, sideEffect );
LocalCreation localCreation = new LocalCreation(b.getLocals(), PREFIX);
Iterator unitIt = unitChain.snapshotIterator();
{ /* insert the computations at the earliest positions */
while (unitIt.hasNext()) {
Unit currentUnit = (Unit)unitIt.next();
Iterator earliestIt =
((FlowSet)earliest.getFlowBefore(currentUnit)).iterator();
while (earliestIt.hasNext()) {
EquivalentValue equiVal = (EquivalentValue)earliestIt.next();
Value exp = equiVal.getValue();
/* get the unic helper-name for this expression */
Local helper = expToHelper.get(equiVal);
if (helper == null) {
helper = localCreation.newLocal(equiVal.getType());
expToHelper.put(equiVal, helper);
}
/* insert a new Assignment-stmt before the currentUnit */
Value insertValue = Jimple.cloneIfNecessary(equiVal.getValue());
Unit firstComp = Jimple.v().newAssignStmt(helper, insertValue);
unitChain.insertBefore(firstComp, currentUnit);
}
}
}
{ /* replace old computations by the helper-vars */
unitIt = unitChain.iterator();
while (unitIt.hasNext()) {
Unit currentUnit = (Unit)unitIt.next();
EquivalentValue rhs = (EquivalentValue)unitToEquivRhs.get(currentUnit);
if (rhs != null) {
Local helper = expToHelper.get(rhs);
if (helper != null)
((AssignStmt)currentUnit).setRightOp(helper);
}
}
}
if(Options.v().verbose())
G.v().out.println("[" + b.getMethod().getName() +
"] Busy Code Motion done!");
}
}
