/*******************************************************************************
* Copyright (c) 2006 IBM Corporation.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package com.ibm.wala.ipa.slicer;
import java.util.Collection;
import java.util.Collections;
import com.ibm.wala.dataflow.IFDS.BackwardsSupergraph;
import com.ibm.wala.dataflow.IFDS.IMergeFunction;
import com.ibm.wala.dataflow.IFDS.IPartiallyBalancedFlowFunctions;
import com.ibm.wala.dataflow.IFDS.ISupergraph;
import com.ibm.wala.dataflow.IFDS.PartiallyBalancedTabulationProblem;
import com.ibm.wala.dataflow.IFDS.PartiallyBalancedTabulationSolver;
import com.ibm.wala.dataflow.IFDS.PathEdge;
import com.ibm.wala.dataflow.IFDS.TabulationDomain;
import com.ibm.wala.dataflow.IFDS.TabulationResult;
import com.ibm.wala.dataflow.IFDS.UnorderedDomain;
import com.ibm.wala.ipa.callgraph.CallGraph;
import com.ibm.wala.ipa.callgraph.propagation.InstanceKey;
import com.ibm.wala.ipa.callgraph.propagation.PointerAnalysis;
import com.ibm.wala.ipa.modref.ModRef;
import com.ibm.wala.util.CancelException;
import com.ibm.wala.util.collections.HashSetFactory;
/**
* A demand-driven context-sensitive slicer.
*
* This computes a context-sensitive slice, building an SDG and finding realizable paths to a statement using tabulation.
*
* This implementation uses a preliminary pointer analysis to compute data dependence between heap locations in the SDG.
*/
public class Slicer {
public final static boolean DEBUG = false;
public final static boolean VERBOSE = false;
/**
* options to control data dependence edges in the SDG
*/
public static enum DataDependenceOptions {
FULL("full", false, false, false, false), NO_BASE_PTRS("no_base_ptrs", true, false, false, false), NO_BASE_NO_HEAP(
"no_base_no_heap", true, true, false, false), NO_BASE_NO_EXCEPTIONS("no_base_no_exceptions", true, false, false, true), NO_BASE_NO_HEAP_NO_EXCEPTIONS(
"no_base_no_heap_no_exceptions", true, true, false, true), NO_HEAP("no_heap", false, true, false, false), NO_HEAP_NO_EXCEPTIONS(
"no_heap_no_exceptions", false, true, false, true), NO_EXCEPTIONS("no_exceptions", false, false, false, true), NONE("none",
true, true, true, true), REFLECTION("no_base_no_heap_no_cast", true, true, true, true);
private final String name;
/**
* Ignore data dependence edges representing base pointers? e.g for a statement y = x.f, ignore the data dependence edges for x
*/
private final boolean ignoreBasePtrs;
/**
* Ignore all data dependence edges to or from the heap?
*/
private final boolean ignoreHeap;
/**
* Ignore outgoing data dependence edges from a cast statements? [This is a special case option used for reflection processing]
*/
private final boolean terminateAtCast;
/**
* Ignore data dependence manifesting throw exception objects?
*/
private final boolean ignoreExceptions;
DataDependenceOptions(String name, boolean ignoreBasePtrs, boolean ignoreHeap, boolean terminateAtCast, boolean ignoreExceptions) {
this.name = name;
this.ignoreBasePtrs = ignoreBasePtrs;
this.ignoreHeap = ignoreHeap;
this.terminateAtCast = terminateAtCast;
this.ignoreExceptions = ignoreExceptions;
}
public final boolean isIgnoreBasePtrs() {
return ignoreBasePtrs;
}
public final boolean isIgnoreHeap() {
return ignoreHeap;
}
public final boolean isIgnoreExceptions() {
return ignoreExceptions;
}
/**
* Should data dependence chains terminate at casts? This is used for reflection processing ... we only track flow into casts
* ... but not out.
*/
public final boolean isTerminateAtCast() {
return terminateAtCast;
}
public final String getName() {
return name;
}
}
/**
* options to control control dependence edges in the sdg
*/
public static enum ControlDependenceOptions {
FULL("full"), NONE("none"), NO_EXCEPTIONAL_EDGES("no_exceptional_edges");
private final String name;
ControlDependenceOptions(String name) {
this.name = name;
}
public final String getName() {
return name;
}
}
/**
* @param s a statement of interest
* @return the backward slice of s.
* @throws CancelException
*/
public static Collection<Statement> computeBackwardSlice(Statement s, CallGraph cg, PointerAnalysis<InstanceKey> pa,
DataDependenceOptions dOptions, ControlDependenceOptions cOptions) throws IllegalArgumentException, CancelException {
return computeSlice(new SDG(cg, pa, ModRef.make(), dOptions, cOptions), Collections.singleton(s), true);
}
/**
* @param s a statement of interest
* @return the forward slice of s.
* @throws CancelException
*/
public static Collection<Statement> computeForwardSlice(Statement s, CallGraph cg, PointerAnalysis<InstanceKey> pa,
DataDependenceOptions dOptions, ControlDependenceOptions cOptions) throws IllegalArgumentException, CancelException {
return computeSlice(new SDG(cg, pa, ModRef.make(), dOptions, cOptions), Collections.singleton(s), false);
}
/**
* Use the passed-in SDG
*
* @throws CancelException
*/
public static Collection<Statement> computeBackwardSlice(SDG sdg, Statement s) throws IllegalArgumentException, CancelException {
return computeSlice(sdg, Collections.singleton(s), true);
}
/**
* Use the passed-in SDG
*
* @throws CancelException
*/
public static Collection<Statement> computeForwardSlice(SDG sdg, Statement s) throws IllegalArgumentException, CancelException {
return computeSlice(sdg, Collections.singleton(s), false);
}
/**
* Use the passed-in SDG
*
* @throws CancelException
*/
public static Collection<Statement> computeBackwardSlice(SDG sdg, Collection<Statement> ss) throws IllegalArgumentException,
CancelException {
return computeSlice(sdg, ss, true);
}
/**
* @param ss a collection of statements of interest
* @throws CancelException
*/
protected static Collection<Statement> computeSlice(SDG sdg, Collection<Statement> ss, boolean backward) throws CancelException {
if (sdg == null) {
throw new IllegalArgumentException("sdg cannot be null");
}
return new Slicer().slice(sdg, ss, backward);
}
/**
* Main driver logic.
*
* @param sdg governing system dependence graph
* @param roots set of roots to slice from
* @param backward do a backwards slice?
* @return the {@link Statement}s found by the slicer
* @throws CancelException
*/
public Collection<Statement> slice(SDG sdg, Collection<Statement> roots, boolean backward) throws CancelException {
if (sdg == null) {
throw new IllegalArgumentException("sdg cannot be null");
}
SliceProblem p = makeSliceProblem(roots, sdg, backward);
PartiallyBalancedTabulationSolver<Statement, PDG, Object> solver = PartiallyBalancedTabulationSolver
.createPartiallyBalancedTabulationSolver(p, null);
TabulationResult<Statement, PDG, Object> tr = solver.solve();
Collection<Statement> slice = tr.getSupergraphNodesReached();
if (VERBOSE) {
System.err.println("Slicer done.");
}
return slice;
}
/**
* Return an object which encapsulates the tabulation logic for the slice problem. Subclasses can override this method to
* implement special semantics.
*/
protected SliceProblem makeSliceProblem(Collection<Statement> roots, ISDG sdgView, boolean backward) {
return new SliceProblem(roots, sdgView, backward);
}
/**
* @param s a statement of interest
* @return the backward slice of s.
* @throws CancelException
*/
public static Collection<Statement> computeBackwardSlice(Statement s, CallGraph cg, PointerAnalysis<InstanceKey> pointerAnalysis)
throws IllegalArgumentException, CancelException {
return computeBackwardSlice(s, cg, pointerAnalysis, DataDependenceOptions.FULL, ControlDependenceOptions.FULL);
}
/**
* Tabulation problem representing slicing
*
*/
public static class SliceProblem implements PartiallyBalancedTabulationProblem<Statement, PDG, Object> {
private final Collection<Statement> roots;
private final ISupergraph<Statement, PDG> supergraph;
private final SliceFunctions f;
private final boolean backward;
public SliceProblem(Collection<Statement> roots, ISDG sdg, boolean backward) {
this.roots = roots;
this.backward = backward;
SDGSupergraph forwards = new SDGSupergraph(sdg, backward);
this.supergraph = backward ? BackwardsSupergraph.make(forwards) : forwards;
f = new SliceFunctions();
}
/*
* @see com.ibm.wala.dataflow.IFDS.TabulationProblem#getDomain()
*/
@Override
public TabulationDomain<Object, Statement> getDomain() {
// a dummy
return new UnorderedDomain<Object, Statement>();
}
/*
* @see com.ibm.wala.dataflow.IFDS.TabulationProblem#getFunctionMap()
*/
@Override
public IPartiallyBalancedFlowFunctions<Statement> getFunctionMap() {
return f;
}
/*
* @see com.ibm.wala.dataflow.IFDS.TabulationProblem#getMergeFunction()
*/
@Override
public IMergeFunction getMergeFunction() {
return null;
}
/*
* @see com.ibm.wala.dataflow.IFDS.TabulationProblem#getSupergraph()
*/
@Override
public ISupergraph<Statement, PDG> getSupergraph() {
return supergraph;
}
@Override
public Collection<PathEdge<Statement>> initialSeeds() {
if (backward) {
Collection<PathEdge<Statement>> result = HashSetFactory.make();
for (Statement st : roots) {
PathEdge<Statement> seed = PathEdge.createPathEdge(new MethodExitStatement(st.getNode()), 0, st, 0);
result.add(seed);
}
return result;
} else {
Collection<PathEdge<Statement>> result = HashSetFactory.make();
for (Statement st : roots) {
PathEdge<Statement> seed = PathEdge.createPathEdge(new MethodEntryStatement(st.getNode()), 0, st, 0);
result.add(seed);
}
return result;
}
}
@Override
public Statement getFakeEntry(Statement node) {
return backward ? new MethodExitStatement(node.getNode()) : new MethodEntryStatement(node.getNode());
}
}
}