soot.jimple.toolkits.scalar.UnconditionalBranchFolder Maven / Gradle / Ivy
/* Soot - a J*va Optimization Framework
* Copyright (C) 1999 Phong Co
*
* 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;
import soot.options.*;
import soot.util.*;
import soot.*;
import soot.jimple.*;
import java.util.*;
public class UnconditionalBranchFolder extends BodyTransformer
{
public UnconditionalBranchFolder( Singletons.Global g ) {}
public static UnconditionalBranchFolder v() { return G.v().soot_jimple_toolkits_scalar_UnconditionalBranchFolder(); }
static final int JUMPOPT_TYPES = 6;
int numFound[], numFixed[];
HashMap stmtMap;
protected void internalTransform(Body b, String phaseName, Map options)
{
StmtBody body = (StmtBody)b;
if (Options.v().verbose())
G.v().out.println("[" + body.getMethod().getName() + "] Folding unconditional branches...");
// allocate counters once only
if (numFound == null) {
numFound = new int[JUMPOPT_TYPES+1];
numFixed = new int[JUMPOPT_TYPES+1];
}
for (int i = 0; i <= JUMPOPT_TYPES; i++) {
numFound[i] = 0;
numFixed[i] = 0;
}
Chain units = body.getUnits();
stmtMap = new HashMap();
// find goto and if-goto statements
Iterator stmtIt = units.iterator();
Stmt stmt, target, newTarget;
while (stmtIt.hasNext()) {
stmt = (Stmt)stmtIt.next();
if (stmt instanceof GotoStmt) {
target = (Stmt)((GotoStmt)stmt).getTarget();
if (stmtIt.hasNext()) {
// check for goto -> next statement
if (units.getSuccOf(stmt) == target)
{
stmtIt.remove();
updateCounters(6, true);
}
}
if (target instanceof GotoStmt) {
newTarget = getFinalTarget(target);
if (newTarget == null)
newTarget = stmt;
((GotoStmt)stmt).setTarget(newTarget);
updateCounters(1, true);
}
else if (target instanceof IfStmt) {
updateCounters(3, false);
}
}
else if (stmt instanceof IfStmt) {
target = ((IfStmt)stmt).getTarget();
if (target instanceof GotoStmt) {
newTarget = getFinalTarget(target);
if (newTarget == null)
newTarget = stmt;
((IfStmt)stmt).setTarget(newTarget);
updateCounters(2, true);
}
else if (target instanceof IfStmt) {
updateCounters(4, false);
}
}
}
if (Options.v().verbose())
G.v().out.println("[" + body.getMethod().getName() + "] " + numFixed[0] + " of " +
numFound[0] + " branches folded.");
} // optimizeJumps
private void updateCounters(int type, boolean fixed) {
if ((type < 0) || (type > JUMPOPT_TYPES))
return;
numFound[0]++;
numFound[type]++;
if (fixed) {
numFixed[0]++;
numFixed[type]++;
}
}
private Stmt getFinalTarget(Stmt stmt) {
Stmt finalTarget=null, target;
// if not a goto, this is the final target
if (!(stmt instanceof GotoStmt))
return stmt;
// first map this statement to itself, so we can detect cycles
stmtMap.put(stmt, stmt);
target = (Stmt)((GotoStmt)stmt).getTarget();
// check if target is in statement map
if (stmtMap.containsKey(target)) {
// see if it maps to itself
finalTarget = stmtMap.get(target);
if (finalTarget == target)
// this is part of a cycle
finalTarget = null;
}
else
finalTarget = getFinalTarget(target);
stmtMap.put(stmt, finalTarget);
return finalTarget;
} // getFinalTarget
} // JumpOptimizer