SVFGOPT.cpp

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//===- SVFGOPT.cpp -- SVFG optimizer------------------------------------------//
//
//                     SVF: Static Value-Flow Analysis
//
// Copyright (C) <2013-2017>  <Yulei Sui>
//
 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
 
// This program 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 Affero General Public License for more details.
 
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
//
//===----------------------------------------------------------------------===//
 
/*
 * @file: SVFGOPT.cpp
 * @author: yesen
 * @date: 31/03/2014
 * @version: 1.0
 *
 * @section LICENSE
 *
 * @section DESCRIPTION
 *
 */
 
#include "Util/Options.h"
#include "Graphs/SVFGOPT.h"
#include "Graphs/SVFGStat.h"
 
using namespace SVF;
using namespace SVFUtil;
 
static std::string KeepAllSelfCycle = "all";
static std::string KeepContextSelfCycle = "context";
static std::string KeepNoneSelfCycle = "none";
 
 
void SVFGOPT::buildSVFG()
{
    SVFG::buildSVFG();
 
    if(Options::DumpVFG())
        dump("SVFG_before_opt");
 
    DBOUT(DGENERAL, outs() << SVFUtil::pasMsg("\tSVFG Optimisation\n"));
 
    keepActualOutFormalIn = Options::KeepAOFI();
 
    stat->sfvgOptStart();
    handleInterValueFlow();
 
    handleIntraValueFlow();
    stat->sfvgOptEnd();
 
}
SVFGEdge* SVFGOPT::addCallIndirectSVFGEdge(NodeID srcId, NodeID dstId, CallSiteID csid, const NodeBS& cpts)
{
    if (Options::ContextInsensitive())
        return addIntraIndirectVFEdge(srcId, dstId, cpts);
    else
        return addCallIndirectVFEdge(srcId, dstId, cpts, csid);
}
 
SVFGEdge* SVFGOPT::addRetIndirectSVFGEdge(NodeID srcId, NodeID dstId, CallSiteID csid, const NodeBS& cpts)
{
    if (Options::ContextInsensitive())
        return addIntraIndirectVFEdge(srcId, dstId, cpts);
    else
        return addRetIndirectVFEdge(srcId, dstId, cpts, csid);
}
 
void SVFGOPT::handleInterValueFlow()
{
    SVFGNodeSet candidates;
    for (SVFGNodeIDToNodeMapTy::iterator it = SVFG::begin(), eit = SVFG::end();
            it!=eit; ++it)
    {
        SVFGNode* node = it->second;
        if (SVFUtil::isa<ActualParmSVFGNode, ActualRetSVFGNode, FormalParmSVFGNode,
                FormalRetSVFGNode, ActualINSVFGNode, ActualOUTSVFGNode,
                FormalINSVFGNode, FormalOUTSVFGNode>(node))
            candidates.insert(node);
    }
 
    SVFGNodeSet nodesToBeDeleted;
    for (SVFGNodeSet::const_iterator it = candidates.begin(), eit = candidates.end();
            it!=eit; ++it)
    {
        SVFGNode* node = *it;
        if (FormalParmSVFGNode* fp = SVFUtil::dyn_cast<FormalParmSVFGNode>(node))
        {
            replaceFParamARetWithPHI(addInterPHIForFP(fp), fp);
            nodesToBeDeleted.insert(fp);
        }
        else if (ActualRetSVFGNode* ar = SVFUtil::dyn_cast<ActualRetSVFGNode>(node))
        {
            replaceFParamARetWithPHI(addInterPHIForAR(ar), ar);
            nodesToBeDeleted.insert(ar);
        }
        else if (SVFUtil::isa<ActualParmSVFGNode, FormalRetSVFGNode>(node))
        {
            nodesToBeDeleted.insert(node);
        }
        else if (SVFUtil::isa<ActualINSVFGNode, FormalOUTSVFGNode>(node))
        {
            retargetEdgesOfAInFOut(node);
            nodesToBeDeleted.insert(node);
        }
        else if (SVFUtil::isa<ActualOUTSVFGNode, FormalINSVFGNode>(node))
        {
            if(keepActualOutFormalIn == false)
                nodesToBeDeleted.insert(node);
        }
    }
 
    for (SVFGNodeSet::iterator it = nodesToBeDeleted.begin(), eit = nodesToBeDeleted.end(); it != eit; ++it)
    {
        SVFGNode* node = *it;
        if (canBeRemoved(node))
        {
            if (SVFUtil::isa<ActualOUTSVFGNode, FormalINSVFGNode>(node))
                retargetEdgesOfAOutFIn(node);   
 
            removeAllEdges(node);
            removeSVFGNode(node);
        }
    }
}
 
void SVFGOPT::replaceFParamARetWithPHI(PHISVFGNode* phi, SVFGNode* svfgNode)
{
    assert((SVFUtil::isa<FormalParmSVFGNode, ActualRetSVFGNode>(svfgNode))
           && "expecting a formal param or actual ret svfg node");
 
    NodeID phiId = phi->getId();
    for (SVFGNode::const_iterator it = svfgNode->OutEdgeBegin(), eit = svfgNode->OutEdgeEnd();
            it != eit; ++it)
    {
        const SVFGEdge* outEdge = *it;
        SVFGNode* dstNode = outEdge->getDstNode();
        NodeID dstId = dstNode->getId();
        if (const CallDirSVFGEdge* callEdge = SVFUtil::dyn_cast<CallDirSVFGEdge>(outEdge))
            addCallEdge(phiId, dstId, callEdge->getCallSiteId());
        else if (const RetDirSVFGEdge* retEdge = SVFUtil::dyn_cast<RetDirSVFGEdge>(outEdge))
            addRetEdge(phiId, dstId, retEdge->getCallSiteId());
        else
            addIntraDirectVFEdge(phiId, dstId);
    }
 
    if (FormalParmSVFGNode* fp = SVFUtil::dyn_cast<FormalParmSVFGNode>(svfgNode))
    {
        for (SVFGNode::iterator it = svfgNode->InEdgeBegin(), eit = svfgNode->InEdgeEnd();
                it != eit; ++it)
        {
            ActualParmSVFGNode* ap = SVFUtil::cast<ActualParmSVFGNode>((*it)->getSrcNode());
            addInterPHIOperands(phi, ap->getParam());
            // connect actual param's def node to phi node
            addCallEdge(getDef(ap->getParam()), phiId, getCallSiteID(ap->getCallSite(), fp->getFun()));
        }
    }
    else if (ActualRetSVFGNode* ar = SVFUtil::dyn_cast<ActualRetSVFGNode>(svfgNode))
    {
        for (SVFGNode::iterator it = svfgNode->InEdgeBegin(), eit = svfgNode->InEdgeEnd();
                it != eit; ++it)
        {
            FormalRetSVFGNode* fr = SVFUtil::cast<FormalRetSVFGNode>((*it)->getSrcNode());
            addInterPHIOperands(phi, fr->getRet());
            // connect formal return's def node to phi node
            addRetEdge(getDef(fr->getRet()), phiId, getCallSiteID(ar->getCallSite(), fr->getFun()));
        }
    }
 
    removeAllEdges(svfgNode);
}
 
void SVFGOPT::retargetEdgesOfAInFOut(SVFGNode* node)
{
    assert(node->getInEdges().size() == 1 && "actual-in/formal-out can only have one incoming edge as its def size");
 
    SVFGNode* def = nullptr;
    NodeBS inPointsTo;
 
    SVFGNode::const_iterator it = node->InEdgeBegin();
    SVFGNode::const_iterator eit = node->InEdgeEnd();
    for (; it != eit; ++it)
    {
        const IndirectSVFGEdge* inEdge = SVFUtil::cast<IndirectSVFGEdge>(*it);
        inPointsTo = inEdge->getPointsTo();
 
        def = inEdge->getSrcNode();
        if (SVFUtil::isa<ActualINSVFGNode>(node))
            setActualINDef(node->getId(), def->getId());
        else if (SVFUtil::isa<FormalOUTSVFGNode>(node))
            setFormalOUTDef(node->getId(), def->getId());
    }
 
    it = node->OutEdgeBegin(), eit = node->OutEdgeEnd();
    for (; it != eit; ++it)
    {
        const IndirectSVFGEdge* outEdge = SVFUtil::cast<IndirectSVFGEdge>(*it);
        NodeBS intersection = inPointsTo;
        intersection &= outEdge->getPointsTo();
 
        if (intersection.empty())
            continue;
 
        SVFGNode* dstNode = outEdge->getDstNode();
        if (const CallIndSVFGEdge* callEdge = SVFUtil::dyn_cast<CallIndSVFGEdge>(outEdge))
            addCallIndirectSVFGEdge(def->getId(), dstNode->getId(), callEdge->getCallSiteId(), intersection);
        else if (const RetIndSVFGEdge* retEdge = SVFUtil::dyn_cast<RetIndSVFGEdge>(outEdge))
            addRetIndirectSVFGEdge(def->getId(), dstNode->getId(), retEdge->getCallSiteId(), intersection);
        else
            assert(false && "expecting an inter-procedural SVFG edge");
    }
 
    removeAllEdges(node);
}
 
void SVFGOPT::retargetEdgesOfAOutFIn(SVFGNode* node)
{
    SVFGNode::const_iterator inIt = node->InEdgeBegin();
    SVFGNode::const_iterator inEit = node->InEdgeEnd();
    for (; inIt != inEit; ++inIt)
    {
        const IndirectSVFGEdge* inEdge = SVFUtil::cast<IndirectSVFGEdge>(*inIt);
        NodeID srcId = inEdge->getSrcID();
 
        SVFGNode::const_iterator outIt = node->OutEdgeBegin();
        SVFGNode::const_iterator outEit = node->OutEdgeEnd();
        for (; outIt != outEit; ++outIt)
        {
            const IndirectSVFGEdge* outEdge = SVFUtil::cast<IndirectSVFGEdge>(*outIt);
 
            NodeBS intersection = inEdge->getPointsTo();
            intersection &= outEdge->getPointsTo();
            if (intersection.empty())
                continue;
 
            NodeID dstId = outEdge->getDstID();
            if (const RetIndSVFGEdge* retEdge = SVFUtil::dyn_cast<RetIndSVFGEdge>(inEdge))
            {
                addRetIndirectSVFGEdge(srcId, dstId, retEdge->getCallSiteId(), intersection);
            }
            else if (const CallIndSVFGEdge* callEdge = SVFUtil::dyn_cast<CallIndSVFGEdge>(inEdge))
            {
                addCallIndirectSVFGEdge(srcId, dstId, callEdge->getCallSiteId(), intersection);
            }
            else
            {
                addIntraIndirectVFEdge(srcId, dstId, intersection);
            }
        }
    }
 
    removeAllEdges(node);
}
 
bool SVFGOPT::isConnectingTwoCallSites(const SVFGNode* node) const
{
    bool hasInCallRet = false;
    bool hasOutCallRet = false;
 
    SVFGNode::const_iterator edgeIt = node->InEdgeBegin();
    SVFGNode::const_iterator edgeEit = node->InEdgeEnd();
    for (; edgeIt != edgeEit; ++edgeIt)
    {
        if (SVFUtil::isa<CallIndSVFGEdge, RetIndSVFGEdge>(*edgeIt))
        {
            hasInCallRet = true;
            break;
        }
    }
 
    edgeIt = node->OutEdgeBegin();
    edgeEit = node->OutEdgeEnd();
    for (; edgeIt != edgeEit; ++edgeIt)
    {
        if (SVFUtil::isa<CallIndSVFGEdge, RetIndSVFGEdge>(*edgeIt))
        {
            hasOutCallRet = true;
            break;
        }
    }
 
    if (hasInCallRet && hasOutCallRet)
        return true;
    else
        return false;
}
 
bool SVFGOPT::canBeRemoved(const SVFGNode * node)
{
    if (SVFUtil::isa<ActualParmSVFGNode, FormalParmSVFGNode,
            ActualRetSVFGNode, FormalRetSVFGNode>(node))
        return true;
    else if (SVFUtil::isa<ActualINSVFGNode, ActualOUTSVFGNode, FormalINSVFGNode,
             FormalOUTSVFGNode, MSSAPHISVFGNode>(node))
    {
        if (isConnectingTwoCallSites(node))
            return false;
 
        if (const ActualINSVFGNode* ai = SVFUtil::dyn_cast<ActualINSVFGNode>(node))
        {
            return (actualInOfIndCS(ai) == false);
        }
        else if (const ActualOUTSVFGNode* ao = SVFUtil::dyn_cast<ActualOUTSVFGNode>(node))
        {
            return (actualOutOfIndCS(ao) == false && isDefOfAInFOut(node) == false);
        }
        else if (const FormalINSVFGNode* fi = SVFUtil::dyn_cast<FormalINSVFGNode>(node))
        {
            return (formalInOfAddressTakenFunc(fi) == false && isDefOfAInFOut(node) == false);
        }
        else if (const FormalOUTSVFGNode* fo = SVFUtil::dyn_cast<FormalOUTSVFGNode>(node))
        {
            return (formalOutOfAddressTakenFunc(fo) == false);
        }
    }
 
    return false;
}
 
void SVFGOPT::parseSelfCycleHandleOption()
{
    std::string choice = (Options::SelfCycle().empty()) ? "" : Options::SelfCycle();
    if (choice.empty() || choice == KeepAllSelfCycle)
        keepAllSelfCycle = true;
    else if (choice == KeepContextSelfCycle)
        keepContextSelfCycle = true;
    else if (choice == KeepNoneSelfCycle)
        keepAllSelfCycle = keepContextSelfCycle = false;
    else
    {
        SVFUtil::writeWrnMsg("Unrecognised option. All self cycle edges will be kept.");
        keepAllSelfCycle = true;
    }
}
 
void SVFGOPT::handleIntraValueFlow()
{
    parseSelfCycleHandleOption();
 
    initialWorkList();
 
    while (!worklist.empty())
    {
        const MSSAPHISVFGNode* node = worklist.pop();
 
        if (checkSelfCycleEdges(node))
            continue;
 
        if (node->hasOutgoingEdge() && node->hasIncomingEdge())
            bypassMSSAPHINode(node);
 
        if (node->hasIncomingEdge() && node->hasOutgoingEdge() == false)
        {
            SVFGNode::const_iterator edgeIt = node->InEdgeBegin();
            SVFGNode::const_iterator edgeEit = node->InEdgeEnd();
            for (; edgeIt != edgeEit; ++edgeIt)
                addIntoWorklist((*edgeIt)->getSrcNode());
 
            removeInEdges(node);
        }
        else if (node->hasOutgoingEdge() && node->hasIncomingEdge() == false)
        {
            SVFGNode::const_iterator edgeIt = node->OutEdgeBegin();
            SVFGNode::const_iterator edgeEit = node->OutEdgeEnd();
            for (; edgeIt != edgeEit; ++edgeIt)
                addIntoWorklist((*edgeIt)->getDstNode());
 
            removeOutEdges(node);
        }
 
        if (node->hasIncomingEdge() == false && node->hasOutgoingEdge() == false)
            removeSVFGNode(const_cast<MSSAPHISVFGNode*>(node));
    }
}
 
 
bool SVFGOPT::checkSelfCycleEdges(const MSSAPHISVFGNode* node)
{
    bool hasSelfCycle = false;
 
    SVFGEdge::SVFGEdgeSetTy inEdges = node->getInEdges();
    SVFGNode::const_iterator inEdgeIt = inEdges.begin();
    SVFGNode::const_iterator inEdgeEit = inEdges.end();
    for (; inEdgeIt != inEdgeEit; ++inEdgeIt)
    {
        SVFGEdge* preEdge = *inEdgeIt;
 
        if (preEdge->getSrcID() == preEdge->getDstID())
        {
            if (keepAllSelfCycle)
            {
                hasSelfCycle = true;
                break;  
            }
            else if (keepContextSelfCycle &&
                     SVFUtil::isa<CallIndSVFGEdge, RetIndSVFGEdge>(preEdge))
            {
                hasSelfCycle = true;
                continue;   
            }
            else
            {
                assert(SVFUtil::isa<IndirectSVFGEdge>(preEdge) && "can only remove indirect SVFG edge");
                removeSVFGEdge(preEdge);
            }
        }
    }
 
    return hasSelfCycle;
}
 
void SVFGOPT::bypassMSSAPHINode(const MSSAPHISVFGNode* node)
{
    SVFGNode::const_iterator inEdgeIt = node->InEdgeBegin();
    SVFGNode::const_iterator inEdgeEit = node->InEdgeEnd();
    for (; inEdgeIt != inEdgeEit; ++inEdgeIt)
    {
        const SVFGEdge* preEdge = *inEdgeIt;
        const SVFGNode* srcNode = preEdge->getSrcNode();
 
        bool added = false;
        SVFGNode::const_iterator outEdgeIt = node->OutEdgeBegin();
        SVFGNode::const_iterator outEdgeEit = node->OutEdgeEnd();
        for (; outEdgeIt != outEdgeEit; ++outEdgeIt)
        {
            const SVFGEdge* succEdge = *outEdgeIt;
            const SVFGNode* dstNode = (*outEdgeIt)->getDstNode();
            if (srcNode->getId() != dstNode->getId()
                    && addNewSVFGEdge(srcNode->getId(), dstNode->getId(), preEdge, succEdge))
                added = true;
            else
            {
                addIntoWorklist(dstNode);
            }
        }
 
        if (added == false)
        {
            addIntoWorklist(srcNode);
        }
    }
 
    removeAllEdges(node);
}
 
bool SVFGOPT::addNewSVFGEdge(NodeID srcId, NodeID dstId, const SVFGEdge* preEdge, const SVFGEdge* succEdge)
{
    assert(SVFUtil::isa<IndirectSVFGEdge>(preEdge) && SVFUtil::isa<IndirectSVFGEdge>(succEdge)
           && "either pre or succ edge is not indirect SVFG edge");
 
    const IndirectSVFGEdge* preIndEdge = SVFUtil::cast<IndirectSVFGEdge>(preEdge);
    const IndirectSVFGEdge* succIndEdge = SVFUtil::cast<IndirectSVFGEdge>(succEdge);
 
    NodeBS intersection = preIndEdge->getPointsTo();
    intersection &= succIndEdge->getPointsTo();
 
    if (intersection.empty())
        return false;
 
    assert(bothInterEdges(preEdge, succEdge) == false && "both edges are inter edges");
 
    if (const CallIndSVFGEdge* preCallEdge = SVFUtil::dyn_cast<CallIndSVFGEdge>(preEdge))
    {
        return addCallIndirectSVFGEdge(srcId, dstId, preCallEdge->getCallSiteId(), intersection);
    }
    else if (const CallIndSVFGEdge* succCallEdge = SVFUtil::dyn_cast<CallIndSVFGEdge>(succEdge))
    {
        return addCallIndirectSVFGEdge(srcId, dstId, succCallEdge->getCallSiteId(), intersection);
    }
    else if (const RetIndSVFGEdge* preRetEdge = SVFUtil::dyn_cast<RetIndSVFGEdge>(preEdge))
    {
        return addRetIndirectSVFGEdge(srcId, dstId, preRetEdge->getCallSiteId(), intersection);
    }
    else if (const RetIndSVFGEdge* succRetEdge = SVFUtil::dyn_cast<RetIndSVFGEdge>(succEdge))
    {
        return addRetIndirectSVFGEdge(srcId, dstId, succRetEdge->getCallSiteId(), intersection);
    }
    else
    {
        return addIntraIndirectVFEdge(srcId, dstId, intersection);
    }
 
    return false;
}