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RoboVM fork of Soot - A Java optimization framework
/* Soot - a J*va Optimization Framework
* Copyright (C) 1999-2010 Hossein Sadat-Mohtasham
*
* 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.toolkits.graph.pdg;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import soot.Body;
import soot.SootClass;
import soot.toolkits.graph.Block;
import soot.toolkits.graph.BlockGraph;
import soot.toolkits.graph.DominatorNode;
import soot.toolkits.graph.DominatorTree;
import soot.toolkits.graph.HashMutableEdgeLabelledDirectedGraph;
import soot.toolkits.graph.UnitGraph;
import soot.toolkits.graph.pdg.IRegion;
/**
*
* This class implements a Program Dependence Graph as defined in
*
* Ferrante, J., Ottenstein, K. J., and Warren, J. D. 1987.
* The program dependence graph and its use in optimization.
* ACM Trans. Program. Lang. Syst. 9, 3 (Jul. 1987), 319-349.
* DOI= http://doi.acm.org/10.1145/24039.24041
*
* Note: the implementation is not exactly as in the above paper. It first finds
* the regions of control dependence then uses part of the algorithm given in
* the above paper to build the graph.
*
* The constructor accepts a UnitGraph, which can be a BriefUnitGraph, an ExceptionalUnitGraph,
* or an EnhancedUnitGraph. At the absence of exception handling constructs in
* a method, all of these work the same. However, at the presence of exception handling
* constructs, BriefUnitGraph is multi-headed and potentially multi-tailed which makes
* the results of RegionAnalysis and PDG construction unreliable (It's not clear if
* it would be useful anyway); Also, ExceptionalGraph's usefulness when exception handling
* is present is not so clear since almost every unit can throw exception hence the
* dependency is affected. Currently, the PDG is based on a UnitGraph (BlockGraph) and does
* not care whether flow is exceptional or not.
*
* The nodes in a PDG are of type PDGNode and the edges can have three labels: "dependency",
* "dependency-back", and "controlflow"; however, the "controlflow" edges are auxiliary
* and the dependencies are represented by the labels beginning with "dependency".
* Other labels can be added later for application
* or domain-specific cases.
*
*
* To support methods that contain exception-handling and multiple-heads or tails, use EnhancedUnitGraph.
* It does not represent exceptional flow in the way ExceptionalUnitGraph does, but it integrates
* them in a concise way. Also, it adds START/STOP nodes to graph if necessary to make the graph
* single entry single exit.
*
*
* @author Hossein Sadat-Mohtasham
* Sep 2009
*/
public class HashMutablePDG extends HashMutableEdgeLabelledDirectedGraph implements ProgramDependenceGraph {
protected Body m_body = null;
protected SootClass m_class = null;
protected UnitGraph m_cfg = null;
protected BlockGraph m_blockCFG = null;
protected Hashtable m_obj2pdgNode = new Hashtable();
protected List m_weakRegions = null;
protected List m_strongRegions = null;
protected PDGNode m_startNode = null;
protected List m_pdgRegions = null;
private RegionAnalysis m_regionAnalysis = null;
private int m_strongRegionStartID;
public HashMutablePDG(UnitGraph cfg)
{
this.m_body = cfg.getBody();
this.m_class = this.m_body.getMethod().getDeclaringClass();
this.m_cfg = cfg;
this.m_regionAnalysis = new RegionAnalysis(this.m_cfg, this.m_body.getMethod(), this.m_class);
/*
* Get the weak regions and save a copy. Note that the strong regions list is
* initially cloned from the weak region to be later modified.
*/
this.m_strongRegions = this.m_regionAnalysis.getRegions();
this.m_weakRegions = this.cloneRegions(this.m_strongRegions);
this.m_blockCFG = this.m_regionAnalysis.getBlockCFG();
//Construct the PDG
this.constructPDG();
this.m_pdgRegions = HashMutablePDG.computePDGRegions(this.m_startNode);
/*This is needed to convert the initially Region-typed inner node of the PDG's head
to a PDGRegion-typed one after the whole graph is computed.
The root PDGRegion is the one with no parent.
*/
IRegion r = this.m_pdgRegions.get(0);
while(r.getParent() != null)
r = r.getParent();
this.m_startNode.setNode(r);
}
/**
* This is the heart of the PDG contruction. It is huge and definitely needs
* some refactorings, but since it's been evlovong to cover some boundary cases
* it has become hard to rafactor.
*
* It uses the list of weak regions, along with the dominator and post-dominator
* trees to construct the PDG nodes.
*/
@SuppressWarnings("unchecked")
protected void constructPDG()
{
Hashtable block2region = this.m_regionAnalysis.getBlock2RegionMap();
DominatorTree pdom = this.m_regionAnalysis.getPostDominatorTree();
DominatorTree dom = this.m_regionAnalysis.getDominatorTree();
List regions2process = new LinkedList();
Region topLevelRegion = this.m_regionAnalysis.getTopLevelRegion();
m_strongRegionStartID = m_weakRegions.size();
//This becomes the top-level region (or ENTRY region node)
PDGNode pdgnode = new PDGNode(topLevelRegion, PDGNode.Type.REGION);
this.addNode(pdgnode);
this.m_obj2pdgNode.put(topLevelRegion, pdgnode);
this.m_startNode = pdgnode;
topLevelRegion.setParent(null);
regions2process.add(topLevelRegion);
//while there's a (weak) region to process
while(!regions2process.isEmpty())
{
Region r = regions2process.remove(0);
//get the corresponding pdgnode
pdgnode = this.m_obj2pdgNode.get(r);
/*
* For all the CFG nodes in the region, create the corresponding PDG node and edges, and
* process them if they are in the dependence set of other regions, i.e. other regions
* depend on them.
*/
List blocks = r.getBlocks();
Hashtable> toBeRemoved = new Hashtable>();
PDGNode prevPDGNodeInRegion = null;
PDGNode curNodeInRegion = null;
for(Iterator itr = blocks.iterator(); itr.hasNext();)
{
/*
* Add the PDG node corresponding to the CFG block node.
*/
Block a = itr.next();
PDGNode pdgNodeOfA = null;
if(!this.m_obj2pdgNode.containsKey(a))
{
pdgNodeOfA = new PDGNode(a, PDGNode.Type.CFGNODE);
this.addNode(pdgNodeOfA);
this.m_obj2pdgNode.put(a, pdgNodeOfA);
}
else
pdgNodeOfA = this.m_obj2pdgNode.get(a);
this.addEdge(pdgnode, pdgNodeOfA, "dependency");
pdgnode.addDependent(pdgNodeOfA);
//
curNodeInRegion = pdgNodeOfA;
/*
* For each successor B of A, if B does not post-dominate A, add all the
* nodes on the path from B to the L in the post-dominator tree, where L is the least
* common ancestor of A and B in the post-dominator tree (L will be either A itself or
* the parent of A.).
*/
List bs = this.m_blockCFG.getSuccsOf(a);
for(Iterator bItr = bs.iterator(); bItr.hasNext();)
{
List dependents = new ArrayList();
Block b = bItr.next();
if(b.equals(a))
throw new RuntimeException("PDG construction: A and B are not supposed to be the same node!");
DominatorNode aDode = pdom.getDode(a);
DominatorNode bDode = pdom.getDode(b);
//If B post-dominates A, go to the next successor.
if(pdom.isDominatorOf(bDode, aDode))
continue;
//FIXME: what if the parent is null?!!
DominatorNode aParentDode = aDode.getParent();
DominatorNode dode = bDode;
while(dode != aParentDode)
{
dependents.add((Block)dode.getGode());
//This occurs if the CFG is multi-tailed and therefore the pdom is a forest.
if(dode.getParent() == null)
//throw new RuntimeException("parent dode in pdom is null: dode is " + aDode);
break;
dode = dode.getParent();
}
/*
* If node A is in the dependent list of A, then A is the header of a loop.
* Otherwise, A could still be the header of a loop or just a simple predicate.
*/
//first make A's pdg node be a conditional (predicate) pdgnode, if it's not already.
if(pdgNodeOfA.getAttrib() != PDGNode.Attribute.CONDHEADER)
{
PDGNode oldA = pdgNodeOfA;
pdgNodeOfA = new ConditionalPDGNode(pdgNodeOfA);
this.replaceInGraph(pdgNodeOfA, oldA);
pdgnode.removeDependent(oldA);
this.m_obj2pdgNode.put(a, pdgNodeOfA);
pdgnode.addDependent(pdgNodeOfA);
pdgNodeOfA.setAttrib(PDGNode.Attribute.CONDHEADER);
curNodeInRegion = pdgNodeOfA;
}
List copyOfDependents = new ArrayList();
copyOfDependents.addAll(dependents);
//First, add the dependency for B and its corresponding region.
Region regionOfB = block2region.get(b);
PDGNode pdgnodeOfBRegion = null;
if(!this.m_obj2pdgNode.containsKey(regionOfB))
{
pdgnodeOfBRegion = new PDGNode(regionOfB, PDGNode.Type.REGION);
this.addNode(pdgnodeOfBRegion);
this.m_obj2pdgNode.put(regionOfB, pdgnodeOfBRegion);
}
else
pdgnodeOfBRegion = this.m_obj2pdgNode.get(regionOfB);
//set the region hierarchy
regionOfB.setParent(r);
r.addChildRegion(regionOfB);
//add the dependency edges
this.addEdge(pdgNodeOfA, pdgnodeOfBRegion, "dependency");
pdgNodeOfA.addDependent(pdgnodeOfBRegion);
regions2process.add(regionOfB);
//now remove b and all the nodes in the same weak region from the list of dependents
copyOfDependents.remove(b);
copyOfDependents.removeAll(regionOfB.getBlocks());
/* What remains here in the dependence set needs to be processed separately. For
* each node X remained in the dependency set, find the corresponding PDG region node
* and add a dependency edge from the region of B to the region of X. If X's weak
* region contains other nodes not in the dependency set of A, create a new region
* for X and add the proper dependency edges (this actually happens if X is the header
* of a loop and B is a predicate guarding a break/continue.)
*
* Note: it seems the only case that there is a node remained in the dependents is when there
* is a path from b to the header of a loop.
*/
while(!copyOfDependents.isEmpty())
{
Block depB = copyOfDependents.remove(0);
Region rdepB = block2region.get(depB);
/*
* Actually, there are cases when depB is not the header of a loop and therefore would not dominate the current node
* (A) and therefore might not have been created yet. This has happened when an inner loop breaks out of the outer
* loop but could have other cases too.
*/
PDGNode depBPDGNode = this.m_obj2pdgNode.get(depB);
if(depBPDGNode == null)
{
//First, add the dependency for depB and its corresponding region.
PDGNode pdgnodeOfdepBRegion = null;
if(!this.m_obj2pdgNode.containsKey(rdepB))
{
pdgnodeOfdepBRegion = new PDGNode(rdepB, PDGNode.Type.REGION);
this.addNode(pdgnodeOfdepBRegion);
this.m_obj2pdgNode.put(rdepB, pdgnodeOfdepBRegion);
}
else
pdgnodeOfdepBRegion = this.m_obj2pdgNode.get(rdepB);
//set the region hierarchy
rdepB.setParent(regionOfB);
regionOfB.addChildRegion(rdepB);
//add the dependency edges
this.addEdge(pdgnodeOfBRegion, pdgnodeOfdepBRegion, "dependency");
pdgnodeOfBRegion.addDependent(pdgnodeOfdepBRegion);
regions2process.add(rdepB);
//now remove all the nodes in the same weak region from the list of dependents
copyOfDependents.removeAll(rdepB.getBlocks());
continue;
}
/**
* If all the nodes in the weak region of depB are dependent on A, then add
* an edge from the region of B to the region of depB.
*
* else, a new region has to be created to contain the dependences of depB, if
* not already created.
*/
if(dependents.containsAll(rdepB.getBlocks()))
{
/*
* Just add an edge to the pdg node of the existing depB region.
*
*/
//add the dependency edges
//First, add the dependency for depB and its corresponding region.
PDGNode pdgnodeOfdepBRegion = null;
if(!this.m_obj2pdgNode.containsKey(rdepB))
{
pdgnodeOfdepBRegion = new PDGNode(rdepB, PDGNode.Type.REGION);
this.addNode(pdgnodeOfdepBRegion);
this.m_obj2pdgNode.put(rdepB, pdgnodeOfdepBRegion);
}
else
pdgnodeOfdepBRegion = this.m_obj2pdgNode.get(rdepB);
//set the region hierarchy
//Do not set this because the region was created before so must have the
//proper parent already.
//rdepB.setParent(regionOfB);
//regionOfB.addChildRegion(rdepB);
this.addEdge(pdgnodeOfBRegion, pdgnodeOfdepBRegion, "dependency");
pdgnodeOfBRegion.addDependent(pdgnodeOfdepBRegion);
regions2process.add(rdepB);
//now remove all the nodes in the same weak region from the list of dependents
copyOfDependents.removeAll(rdepB.getBlocks());
continue;
}
else
{
PDGNode predPDGofdepB = (PDGNode) this.getPredsOf(depBPDGNode).get(0);
assert(this.m_obj2pdgNode.containsKey(rdepB));
PDGNode pdgnodeOfdepBRegion = this.m_obj2pdgNode.get(rdepB);
//If the loop header has not been separated from its weak region yet
if(predPDGofdepB == pdgnodeOfdepBRegion)
{
/*
* Create a new region to represent the whole loop. In fact, this is a strong
* region as opposed to the weak regions that were created in the RegionAnalysis.
* This strong region only contains the header of the loop, A, and is dependent
* on it. Also, A is dependent on this strong region as well.
*/
Region newRegion = new Region(this.m_strongRegionStartID++, topLevelRegion.getSootMethod(), topLevelRegion.getSootClass(), this.m_cfg);
newRegion.add(depB);
this.m_strongRegions.add(newRegion);
//toBeRemoved.add(depB);
List blocks2BRemoved;
if(toBeRemoved.contains(predPDGofdepB))
blocks2BRemoved = toBeRemoved.get(predPDGofdepB);
else
{
blocks2BRemoved = new ArrayList();
toBeRemoved.put(rdepB, blocks2BRemoved);
}
blocks2BRemoved.add(depB);
PDGNode newpdgnode = new LoopedPDGNode(newRegion, PDGNode.Type.REGION, depBPDGNode);
this.addNode(newpdgnode);
this.m_obj2pdgNode.put(newRegion, newpdgnode);
newpdgnode.setAttrib(PDGNode.Attribute.LOOPHEADER);
depBPDGNode.setAttrib(PDGNode.Attribute.LOOPHEADER);
this.removeEdge(pdgnodeOfdepBRegion, depBPDGNode, "dependency");
pdgnodeOfdepBRegion.removeDependent(depBPDGNode);
this.addEdge(pdgnodeOfdepBRegion, newpdgnode, "dependency");
this.addEdge(newpdgnode, depBPDGNode, "dependency");
pdgnodeOfdepBRegion.addDependent(newpdgnode);
newpdgnode.addDependent(depBPDGNode);
//If a is dependent on itself (simple loop)
if(depB == a)
{
PDGNode loopBodyPDGNode = (PDGNode) this.getSuccsOf(depBPDGNode).get(0);
this.addEdge(depBPDGNode, newpdgnode, "dependency-back");
((LoopedPDGNode)newpdgnode).setBody(loopBodyPDGNode);
depBPDGNode.addBackDependent(newpdgnode);
//This is needed to correctly adjust the prev/next pointers for the new loop node. We should not need
//to adjust the old loop header node because the prev/next should not have been set previously for it.
curNodeInRegion = newpdgnode;
}
else
{
//this is a back-dependency
pdgnodeOfBRegion.addBackDependent(newpdgnode);
this.addEdge(pdgnodeOfBRegion, newpdgnode, "dependency-back");
//DEtermine which dependent of the loop header is actually the loop body region
PDGNode loopBodyPDGNode = null;
List successors = this.getSuccsOf(depBPDGNode);
Iterator succItr = successors.iterator();
while(succItr.hasNext())
{
PDGNode succRPDGNode = succItr.next();
assert(succRPDGNode.getType() == PDGNode.Type.REGION);
Region succR = (Region) succRPDGNode.getNode();
Block h = succR.getBlocks().get(0);
DominatorNode hdode = dom.getDode(h);
DominatorNode adode = dom.getDode(a);
if(dom.isDominatorOf(hdode, adode))
{
loopBodyPDGNode = succRPDGNode;
break;
}
}
assert(loopBodyPDGNode != null);
((LoopedPDGNode)newpdgnode).setBody(loopBodyPDGNode);
PDGNode prev = depBPDGNode.getPrev();
if(prev != null)
{
this.removeEdge(prev, depBPDGNode, "controlflow");
this.addEdge(prev, newpdgnode, "controlflow");
prev.setNext(newpdgnode);
newpdgnode.setPrev(prev);
depBPDGNode.setPrev(null);
}
PDGNode next = depBPDGNode.getNext();
if(next != null)
{
this.removeEdge(depBPDGNode, next, "controlflow");
this.addEdge(newpdgnode, next, "controlflow");
newpdgnode.setNext(next);
next.setPrev(newpdgnode);
depBPDGNode.setNext(null);
}
}
}
else
{
/*
* The strong region for the header has already been created and its
* corresponding PDGNode exist. Just add the dependency edge.
*/
this.addEdge(pdgnodeOfBRegion, predPDGofdepB, "dependency-back");
//this is a back-dependency
pdgnodeOfBRegion.addBackDependent(predPDGofdepB);
}
}
}
}
/* If there is a previous node in this region, add a control flow edge to indicate the
* the correct direction of control flow in the region.
*/
if(prevPDGNodeInRegion != null)
{
this.addEdge(prevPDGNodeInRegion, curNodeInRegion, "controlflow");
prevPDGNodeInRegion.setNext(curNodeInRegion);
curNodeInRegion.setPrev(prevPDGNodeInRegion);
}
prevPDGNodeInRegion = curNodeInRegion;
}
//remove all the blocks marked to be removed from the region (to change a weak region
//to a strong region.)
Enumeration itr1 = toBeRemoved.keys();
while(itr1.hasMoreElements())
{
Region region = itr1.nextElement();
Iterator blockItr = toBeRemoved.get(region).iterator();
while(blockItr.hasNext())
region.remove(blockItr.next());
}
}
}
private List cloneRegions(List weak)
{
List strong = new ArrayList();
Iterator itr = weak.iterator();
while(itr.hasNext())
{
Region r = itr.next();
strong.add((Region)r.clone());
}
return strong;
}
/**
*
* @return The Corresponding UnitGraph
*/
public UnitGraph getCFG()
{
return this.m_cfg;
}
/**
* {@inheritDoc}
*/
public List getWeakRegions()
{
return this.m_weakRegions;
}
/**
* {@inheritDoc}
*/
public List getStrongRegions()
{
return this.m_strongRegions;
}
/**
* {@inheritDoc}
*/
public IRegion GetStartRegion()
{
return this.m_pdgRegions.get(0);
}
/**
* {@inheritDoc}
*/
public PDGNode GetStartNode()
{
return this.m_startNode;
}
public static List getPreorderRegionList(IRegion r)
{
List list = new ArrayList();
Queue toProcess = new LinkedList();
toProcess.add(r);
while(!toProcess.isEmpty())
{
IRegion reg = toProcess.poll();
list.add(reg);
for(Iterator itr = reg.getChildRegions().iterator(); itr.hasNext(); )
toProcess.add((Region)itr.next());
}
return list;
}
public static List getPostorderRegionList(IRegion r)
{
List list = new ArrayList();
postorder(r, list);
return list;
}
private static List postorder(IRegion r, List list)
{
//If there are children, push the children to the stack
if(!r.getChildRegions().isEmpty())
for(Iterator itr = r.getChildRegions().iterator(); itr.hasNext(); )
postorder(itr.next(), list);
list.add(r);
return list;
}
/**
* {@inheritDoc}
*/
public List getPDGRegions()
{
return this.m_pdgRegions;
}
/**
* This method returns a list of regions obtained by post-order
* traversal of the region hierarchy. This takes advantage of the hierarchical
* (parent/child) information encoded within the PDGNodes at construction
* time; it should be noted that, we have not counted the strong regions
* that represent the loop header as a separate region; instead, a PDGRegion
* that represents both the loop header and its body are counted.
* @param The root from which the traversal should begin.
* @return The list of regions obtained thru post-order traversal of the
* region hierarchy.
*/
public static List getPostorderPDGRegionList(PDGNode r)
{
return computePDGRegions(r);
}
private static Hashtable node2Region = new Hashtable();
//compute the pdg region list with in post order
private static List computePDGRegions(PDGNode root)
{
List regions = new ArrayList();
node2Region.clear();
pdgpostorder(root, regions);
return regions;
}
private static PDGRegion pdgpostorder(PDGNode node, List list)
{
node.setVisited(true);
PDGRegion region = null;
if(!node2Region.containsKey(node))
{
region = new PDGRegion(node);
node2Region.put(node, region);
}
else
region = node2Region.get(node);
//If there are children, push the children to the stack
List dependents = node.getDependets();
if(!dependents.isEmpty())
for(Iterator itr = dependents.iterator(); itr.hasNext(); )
{
PDGNode curNode = (PDGNode) itr.next();
if(curNode.getVisited())
continue;
region.addPDGNode(curNode);
if(curNode instanceof LoopedPDGNode)
{
PDGNode body = ((LoopedPDGNode)curNode).getBody();
PDGRegion kid = pdgpostorder(body, list);
kid.setParent(region);
region.addChildRegion(kid);
//This sets the node from the old Region into a PDGRegion
body.setNode(kid);
}
else if(curNode instanceof ConditionalPDGNode)
{
List childs = curNode.getDependets();
Iterator condItr = childs.iterator();
while(condItr.hasNext())
{
PDGNode child = (PDGNode)condItr.next();
PDGRegion kid = pdgpostorder(child, list);
kid.setParent(region);
region.addChildRegion(kid);
//This sets the node from the old Region into a PDGRegion
child.setNode(kid);
}
}
}
list.add(region);
return region;
}
/**
* {@inheritDoc}
*/
public boolean dependentOn(PDGNode node1, PDGNode node2)
{
return node2.getDependets().contains(node1);
}
/**
* {@inheritDoc}
*/
@SuppressWarnings("unchecked")
public List getDependents(PDGNode node)
{
return this.getSuccsOf(node);
//Or return node.getDependents();
}
/**
* {@inheritDoc}
*/
public PDGNode getPDGNode(Object cfgNode)
{
if(cfgNode != null && cfgNode instanceof Block)
if(this.m_obj2pdgNode.containsKey(cfgNode))
return this.m_obj2pdgNode.get(cfgNode);
return null;
}
@SuppressWarnings("unchecked")
private void replaceInGraph(PDGNode newnode, PDGNode oldnode)
{
this.addNode(newnode);
HashMutableEdgeLabelledDirectedGraph graph = (HashMutableEdgeLabelledDirectedGraph) this.clone();
List succs = graph.getSuccsOf(oldnode);
List preds = graph.getPredsOf(oldnode);
Iterator