// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Graph acyclic algorithm
//
// Code available from: https://verilator.org
//
//*************************************************************************
//
// Copyright 2003-2019 by Wilson Snyder.  This program is free software; you can
// redistribute it and/or modify it under the terms of either the GNU
// Lesser General Public License Version 3 or the Perl Artistic License
// Version 2.0.
//
// Verilator 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 General Public License for more details.
//
//*************************************************************************

#include "config_build.h"
#include "verilatedos.h"

#include "V3Global.h"
#include "V3Graph.h"

#include <algorithm>
#include <cstdarg>
#include <list>
#include <vector>

//######################################################################
//######################################################################
// Algorithms - acyclic
//      Break the minimal number of backward edges to make the graph acyclic

class GraphAcycVertex : public V3GraphVertex {
    // user() is used for various sub-algorithm pieces
    V3GraphVertex*      m_origVertexp;          // Pointer to first vertex this represents
protected:
    friend class GraphAcyc;
    V3ListEnt<GraphAcycVertex*> m_work;         // List of vertices with optimization work left
    uint32_t            m_storedRank;           // Rank held until commit to edge placement
    bool                m_onWorkList;           // True if already on list of work to do
    bool                m_deleted;              // True if deleted
public:

    GraphAcycVertex(V3Graph* graphp, V3GraphVertex* origVertexp)
        : V3GraphVertex(graphp), m_origVertexp(origVertexp)
        , m_storedRank(0), m_onWorkList(false), m_deleted(false) {
    }
    virtual ~GraphAcycVertex() {}
    V3GraphVertex* origVertexp() const { return m_origVertexp; }
    void setDelete() { m_deleted = true; }
    bool isDelete() const { return m_deleted; }
    virtual string name() const { return m_origVertexp->name(); }
    virtual string dotColor() const { return m_origVertexp->dotColor(); }
    virtual FileLine* fileline() const { return m_origVertexp->fileline(); }
};

//--------------------------------------------------------------------

class GraphAcycEdge : public V3GraphEdge {
    // userp() is always used to point to the head original graph edge
private:
    typedef std::list<V3GraphEdge*> OrigEdgeList;  // List of orig edges, see also GraphAcyc's decl
    V3GraphEdge*        origEdgep() const {
        OrigEdgeList* oEListp = static_cast<OrigEdgeList*>(userp());
        if (!oEListp) v3fatalSrc("No original edge associated with acyc edge "<<this<<endl);
        return (oEListp->front());
    }
public:
    GraphAcycEdge(V3Graph* graphp, V3GraphVertex* fromp, V3GraphVertex* top,
                  int weight, bool cutable=false)
        : V3GraphEdge(graphp, fromp, top, weight, cutable) {
    }
    virtual ~GraphAcycEdge() {}
    // yellow=we might still cut it, else oldEdge: yellowGreen=made uncutable, red=uncutable
    virtual string dotColor() const { return (cutable()?"yellow":origEdgep()->dotColor()); }
};

//--------------------------------------------------------------------

struct GraphAcycEdgeCmp {
    inline bool operator() (const V3GraphEdge* lhsp, const V3GraphEdge* rhsp) const {
        if (lhsp->weight() > rhsp->weight()) return 1;  // LHS goes first
        if (lhsp->weight() < rhsp->weight()) return 0;  // RHS goes first
        return 0;
    }
};

//--------------------------------------------------------------------

// CLASSES
class GraphAcyc {
private:
    typedef std::list<V3GraphEdge*> OrigEdgeList;  // List of orig edges, see also GraphAcycEdge's decl
    // GRAPH USERS
    //  origGraph
    //    GraphVertex::user()   GraphAycVerted* New graph node
    //  m_breakGraph
    //    GraphEdge::user()     OrigEdgeList*   Old graph edges
    //    GraphVertex::user     bool            Detection of loops in simplifyDupIterate
    // MEMBERS
    V3Graph*            m_origGraphp;           // Original graph
    V3Graph             m_breakGraph;           // Graph with only breakable edges represented
    V3List<GraphAcycVertex*>    m_work;         // List of vertices with optimization work left
    std::vector<OrigEdgeList*> m_origEdgeDelp;  // List of deletions to do when done
    V3EdgeFuncP         m_origEdgeFuncp;        // Function that says we follow this edge (in original graph)
    uint32_t            m_placeStep;            // Number that user() must be equal to to indicate processing

    static int debug() { return V3Graph::debug(); }

    // METHODS
    void buildGraph(V3Graph* origGraphp);
    void buildGraphIterate(V3GraphVertex* overtexp, GraphAcycVertex* avertexp);
    void simplify(bool allowCut);
    void simplifyNone(GraphAcycVertex* avertexp);
    void simplifyOne(GraphAcycVertex* avertexp);
    void simplifyOut(GraphAcycVertex* avertexp);
    void simplifyDup(GraphAcycVertex* avertexp);
    void cutBasic(GraphAcycVertex* avertexp);
    void cutBackward(GraphAcycVertex* avertexp);
    void deleteMarked();
    void place();
    void placeTryEdge(V3GraphEdge* edgep);
    bool placeIterate(GraphAcycVertex* vertexp, uint32_t currentRank);

    inline bool origFollowEdge(V3GraphEdge* edgep) {
        return (edgep->weight() && (m_origEdgeFuncp)(edgep));
    }
    V3GraphEdge* edgeFromEdge(V3GraphEdge* oldedgep, V3GraphVertex* fromp, V3GraphVertex* top) {
        // Make new breakGraph edge, with old edge as a template
        GraphAcycEdge* newEdgep = new GraphAcycEdge(&m_breakGraph, fromp, top,
                                                    oldedgep->weight(), oldedgep->cutable());
        newEdgep->userp(oldedgep->userp());  // Keep pointer to OrigEdgeList
        return newEdgep;
    }
    void addOrigEdgep(V3GraphEdge* toEdgep, V3GraphEdge* addEdgep) {
        // Add addEdge (or it's list) to list of edges that break edge represents
        // Note addEdge may already have a bunch of similar linked edge representations.  Yuk.
        UASSERT(addEdgep, "Adding NULL");
        if (!toEdgep->userp()) {
            OrigEdgeList* oep = new OrigEdgeList;
            m_origEdgeDelp.push_back(oep);
            toEdgep->userp(oep);
        }
        OrigEdgeList* oEListp = static_cast<OrigEdgeList*>(toEdgep->userp());
        if (OrigEdgeList* addListp = static_cast<OrigEdgeList*>(addEdgep->userp())) {
            for (OrigEdgeList::iterator it = addListp->begin(); it != addListp->end(); ++it) {
                oEListp->push_back(*it);
            }
            addListp->clear();  // Done with it
        } else {
            oEListp->push_back(addEdgep);
        }
    }
    void cutOrigEdge(V3GraphEdge* breakEdgep, const char* why) {
        // From the break edge, cut edges in original graph it represents
        UINFO(8,why<<" CUT "<<breakEdgep->fromp()<<endl);
        breakEdgep->cut();
        OrigEdgeList* oEListp = static_cast<OrigEdgeList*>(breakEdgep->userp());
        if (!oEListp) v3fatalSrc("No original edge associated with cutting edge "
                                 <<breakEdgep<<endl);
        // The breakGraph edge may represent multiple real edges; cut them all
        for (OrigEdgeList::iterator it = oEListp->begin(); it != oEListp->end(); ++it) {
            V3GraphEdge* origEdgep = *it;
            origEdgep->cut();
            UINFO(8,"  "<<why<<"   "<<origEdgep->fromp()<<" ->"<<origEdgep->top()<<endl);
        }
    }
    // Work Queue
    void workPush(V3GraphVertex* vertexp) {
        GraphAcycVertex* avertexp = static_cast<GraphAcycVertex*>(vertexp);
        // Add vertex to list of nodes needing further optimization trials
        if (!avertexp->m_onWorkList) {
            avertexp->m_onWorkList = true;
            avertexp->m_work.pushBack(m_work, avertexp);
        }
    }
    GraphAcycVertex* workBeginp() { return m_work.begin(); }
    void workPop() {
        GraphAcycVertex* avertexp = workBeginp();
        avertexp->m_onWorkList = false;
        avertexp->m_work.unlink(m_work, avertexp); }
public:
    // CONSTRUCTORS
    GraphAcyc(V3Graph* origGraphp, V3EdgeFuncP edgeFuncp) {
        m_origGraphp = origGraphp;
        m_origEdgeFuncp = edgeFuncp;
        m_placeStep = 0;
    }
    ~GraphAcyc() {
        for (std::vector<OrigEdgeList*>::iterator it = m_origEdgeDelp.begin();
             it != m_origEdgeDelp.end(); ++it) {
            delete (*it);
        }
        m_origEdgeDelp.clear();
    }
    void main();
};

//--------------------------------------------------------------------

void GraphAcyc::buildGraph(V3Graph* origGraphp) {
    // Presumes the graph has been strongly ordered,
    // and thus there's a unique color if there are loops in this subgraph.

    // For each old node, make a new graph node for optimization
    origGraphp->userClearVertices();
    origGraphp->userClearEdges();
    for (V3GraphVertex* overtexp = origGraphp->verticesBeginp();
         overtexp; overtexp = overtexp->verticesNextp()) {
        if (overtexp->color()) {
            GraphAcycVertex* avertexp = new GraphAcycVertex(&m_breakGraph, overtexp);
            overtexp->userp(avertexp);  // Stash so can look up later
        }
    }

    // Build edges between logic vertices
    for (V3GraphVertex* overtexp = origGraphp->verticesBeginp();
         overtexp; overtexp = overtexp->verticesNextp()) {
        if (overtexp->color()) {
            GraphAcycVertex* avertexp = static_cast<GraphAcycVertex*>(overtexp->userp());
            buildGraphIterate(overtexp, avertexp);
        }
    }
}

void GraphAcyc::buildGraphIterate(V3GraphVertex* overtexp, GraphAcycVertex* avertexp) {
    // Make new edges
    for (V3GraphEdge* edgep = overtexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
        if (origFollowEdge(edgep)) {  // not cut
            V3GraphVertex* toVertexp = edgep->top();
            if (toVertexp->color()) {
                GraphAcycVertex* toAVertexp = static_cast<GraphAcycVertex*>(toVertexp->userp());
                // Replicate the old edge into the new graph
                // There may be multiple edges between same pairs of vertices
                V3GraphEdge* breakEdgep = new GraphAcycEdge
                    (&m_breakGraph, avertexp, toAVertexp, edgep->weight(), edgep->cutable());
                addOrigEdgep(breakEdgep, edgep);  // So can find original edge
            }
        }
    }
}

void GraphAcyc::simplify(bool allowCut) {
    // Add all nodes to list of work to do
    for (V3GraphVertex* vertexp = m_breakGraph.verticesBeginp();
         vertexp; vertexp = vertexp->verticesNextp()) {
        workPush(vertexp);
    }
    // Optimize till everything finished
    while (GraphAcycVertex* vertexp = workBeginp()) {
        workPop();
        simplifyNone(vertexp);
        simplifyOne(vertexp);
        simplifyOut(vertexp);
        simplifyDup(vertexp);
        if (allowCut) {
            // The main algorithm works without these, though slower
            // So if changing the main algorithm, comment these out for a test run
            if (v3Global.opt.oAcycSimp()) {
                cutBasic(vertexp);
                cutBackward(vertexp);
            }
        }
    }
    deleteMarked();
}

void GraphAcyc::deleteMarked() {
    // Delete nodes marked for removal
    for (V3GraphVertex* nextp, *vertexp = m_breakGraph.verticesBeginp(); vertexp; vertexp=nextp) {
        nextp = vertexp->verticesNextp();
        GraphAcycVertex* avertexp = static_cast<GraphAcycVertex*>(vertexp);
        if (avertexp->isDelete()) {
            avertexp->unlinkDelete(&m_breakGraph); VL_DANGLING(avertexp);
        }
    }
}

void GraphAcyc::simplifyNone(GraphAcycVertex* avertexp) {
    // Don't need any vertices with no inputs, There's no way they can have a loop.
    // Likewise, vertices with no outputs
    if (avertexp->isDelete()) return;
    if (avertexp->inEmpty() || avertexp->outEmpty()) {
        UINFO(9,"  SimplifyNoneRemove "<<avertexp<<endl);
        avertexp->setDelete();  // Mark so we won't delete it twice
        // Remove edges
        while (V3GraphEdge* edgep = avertexp->outBeginp()) {
            V3GraphVertex* otherVertexp = edgep->top();
            //UINFO(9,"  out "<<otherVertexp<<endl);
            edgep->unlinkDelete(); VL_DANGLING(edgep);
            workPush(otherVertexp);
        }
        while (V3GraphEdge* edgep = avertexp->inBeginp()) {
            V3GraphVertex* otherVertexp = edgep->fromp();
            //UINFO(9,"  in  "<<otherVertexp<<endl);
            edgep->unlinkDelete(); VL_DANGLING(edgep);
            workPush(otherVertexp);
        }
    }
}

void GraphAcyc::simplifyOne(GraphAcycVertex* avertexp) {
    // If a node has one input and one output, we can remove it and change the edges
    if (avertexp->isDelete()) return;
    if (avertexp->inSize1() && avertexp->outSize1()) {
        V3GraphEdge* inEdgep = avertexp->inBeginp();
        V3GraphEdge* outEdgep = avertexp->outBeginp();
        V3GraphVertex* inVertexp = inEdgep->fromp();
        V3GraphVertex* outVertexp = outEdgep->top();
        // The in and out may be the same node; we'll make a loop
        // The in OR out may be THIS node; we can't delete it then.
        if (inVertexp!=avertexp && outVertexp!=avertexp) {
            UINFO(9,"  SimplifyOneRemove "<<avertexp<<endl);
            avertexp->setDelete();  // Mark so we won't delete it twice
            // Make a new edge connecting the two vertices directly
            // If both are breakable, we pick the one with less weight, else it's arbitrary
            // We can forget about the origEdge list for the "non-selected" set of edges,
            // as we need to break only one set or the other set of edges, not both.
            // (This is why we must give preference to the cutable set.)
            V3GraphEdge* templateEdgep = ( (inEdgep->cutable()
                                            && (!outEdgep->cutable()
                                                || inEdgep->weight()<outEdgep->weight() ))
                                           ? inEdgep : outEdgep);
            // cppcheck-suppress leakReturnValNotUsed
            edgeFromEdge(templateEdgep, inVertexp, outVertexp);
            // Remove old edge
            inEdgep->unlinkDelete(); VL_DANGLING(inEdgep);
            outEdgep->unlinkDelete(); VL_DANGLING(outEdgep); VL_DANGLING(templateEdgep);
            workPush(inVertexp);
            workPush(outVertexp);
        }
    }
}

void GraphAcyc::simplifyOut(GraphAcycVertex* avertexp) {
    // If a node has one output that's not cutable, all its inputs can be reassigned
    // to the next node in the list
    if (avertexp->isDelete()) return;
    if (avertexp->outSize1()) {
        V3GraphEdge* outEdgep = avertexp->outBeginp();
        if (!outEdgep->cutable()) {
            V3GraphVertex* outVertexp = outEdgep->top();
            UINFO(9,"  SimplifyOutRemove "<<avertexp<<endl);
            avertexp->setDelete();  // Mark so we won't delete it twice
            for (V3GraphEdge* nextp, *inEdgep = avertexp->inBeginp(); inEdgep; inEdgep=nextp) {
                nextp = inEdgep->inNextp();
                V3GraphVertex* inVertexp = inEdgep->fromp();
                if (inVertexp == avertexp) {
                    if (debug()) v3error("Non-cutable edge forms a loop, vertex="<<avertexp);
                    v3error("Circular logic when ordering code (non-cutable edge loop)");
                    m_origGraphp->reportLoops(&V3GraphEdge::followNotCutable,
                                              avertexp->origVertexp());  // calls OrderGraph::loopsVertexCb
                    // Things are unlikely to end well at this point,
                    // but we'll try something to get to further errors...
                    inEdgep->cutable(true);
                    return;
                }
                // Make a new edge connecting the two vertices directly
                // cppcheck-suppress leakReturnValNotUsed
                edgeFromEdge(inEdgep, inVertexp, outVertexp);
                // Remove old edge
                inEdgep->unlinkDelete(); VL_DANGLING(inEdgep);
                workPush(inVertexp);
            }
            outEdgep->unlinkDelete(); VL_DANGLING(outEdgep);
            workPush(outVertexp);
        }
    }
}

void GraphAcyc::simplifyDup(GraphAcycVertex* avertexp) {
    // Remove redundant edges
    if (avertexp->isDelete()) return;
    // Clear marks
    for (V3GraphEdge* edgep = avertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
        edgep->top()->userp(NULL);
    }
    // Mark edges and detect duplications
    for (V3GraphEdge* nextp, *edgep = avertexp->outBeginp(); edgep; edgep=nextp) {
        nextp = edgep->outNextp();
        V3GraphVertex* outVertexp = edgep->top();
        V3GraphEdge* prevEdgep = static_cast<V3GraphEdge*>(outVertexp->userp());
        if (prevEdgep) {
            if (!prevEdgep->cutable()) {
                // !cutable duplicates prev !cutable: we can ignore it, redundant
                //  cutable duplicates prev !cutable: know it's not a relevant loop, ignore it
                UINFO(8,"    DelDupEdge "<<avertexp<<" -> "<<edgep->top()<<endl);
                edgep->unlinkDelete(); VL_DANGLING(edgep);
            } else if (!edgep->cutable()) {
                // !cutable duplicates prev  cutable: delete the earlier cutable
                UINFO(8,"    DelDupPrev "<<avertexp<<" -> "<<prevEdgep->top()<<endl);
                prevEdgep->unlinkDelete(); VL_DANGLING(prevEdgep);
                outVertexp->userp(edgep);
            } else {
                //  cutable duplicates prev  cutable: combine weights
                UINFO(8,"    DelDupComb "<<avertexp<<" -> "<<edgep->top()<<endl);
                prevEdgep->weight(prevEdgep->weight() + edgep->weight());
                addOrigEdgep(prevEdgep, edgep);
                edgep->unlinkDelete(); VL_DANGLING(edgep);
            }
            workPush(outVertexp);
            workPush(avertexp);
        } else {
            // No previous assignment
            outVertexp->userp(edgep);
        }
    }
}

void GraphAcyc::cutBasic(GraphAcycVertex* avertexp) {
    // Detect and cleanup any loops from node to itself
    if (avertexp->isDelete()) return;
    for (V3GraphEdge* nextp, *edgep = avertexp->outBeginp(); edgep; edgep=nextp) {
        nextp = edgep->outNextp();
        if (edgep->cutable() && edgep->top()==avertexp) {
            cutOrigEdge(edgep, "  Cut Basic");
            edgep->unlinkDelete(); VL_DANGLING(edgep);
            workPush(avertexp);
        }
    }
}

void GraphAcyc::cutBackward(GraphAcycVertex* avertexp) {
    // If a cutable edge is from A->B, and there's a non-cutable edge B->A, then must cut!
    if (avertexp->isDelete()) return;
    // Clear marks
    for (V3GraphEdge* edgep = avertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
        edgep->top()->user(false);
    }
    for (V3GraphEdge* edgep = avertexp->inBeginp(); edgep; edgep=edgep->inNextp()) {
        if (!edgep->cutable()) edgep->fromp()->user(true);
    }
    // Detect duplications
    for (V3GraphEdge* nextp, *edgep = avertexp->outBeginp(); edgep; edgep=nextp) {
        nextp = edgep->outNextp();
        if (edgep->cutable() && edgep->top()->user()) {
            cutOrigEdge(edgep, "  Cut A->B->A");
            edgep->unlinkDelete(); VL_DANGLING(edgep);
            workPush(avertexp);
        }
    }
}

void GraphAcyc::place() {
    // Input is m_breakGraph with ranks already assigned on non-breakable edges

    // Make a list of all cutable edges in the graph
    int numEdges = 0;
    for (V3GraphVertex* vertexp = m_breakGraph.verticesBeginp();
         vertexp; vertexp = vertexp->verticesNextp()) {
        for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
            if (edgep->weight() && edgep->cutable()) {
                numEdges++;
            }
        }
    }
    UINFO(4, "    Cutable edges = "<<numEdges<<endl);

    std::vector<V3GraphEdge*> edges;  // List of all edges to be processed
    edges.reserve(numEdges+1);  // Make the vector properly sized right off the bat -- faster than reallocating
    for (V3GraphVertex* vertexp = m_breakGraph.verticesBeginp();
         vertexp; vertexp = vertexp->verticesNextp()) {
        vertexp->user(0);  // Clear in prep of next step
        for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
            if (edgep->weight() && edgep->cutable()) {
                edges.push_back(edgep);
            }
        }
    }

    // Sort by weight, then by vertex (so that we completely process one vertex, when possible)
    stable_sort(edges.begin(), edges.end(), GraphAcycEdgeCmp());

    // Process each edge in weighted order
    m_placeStep = 10;
    for (std::vector<V3GraphEdge*>::iterator it = edges.begin(); it!=edges.end(); ++it) {
        V3GraphEdge* edgep = (*it);
        placeTryEdge(edgep);
    }
}

void GraphAcyc::placeTryEdge(V3GraphEdge* edgep) {
    // Try to make this edge uncutable
    m_placeStep++;
    UINFO(8, "    PlaceEdge s"<<m_placeStep<<" w"<<edgep->weight()<<" "<<edgep->fromp()<<endl);
    // Make the edge uncutable so we detect it in placement
    edgep->cutable(false);
    // Vertex::m_user begin: number indicates this edge was completed
    // Try to assign ranks, presuming this edge is in place
    // If we come across user()==placestep, we've detected a loop and must back out
    bool loop = placeIterate(static_cast<GraphAcycVertex*>(edgep->top()),
                             edgep->fromp()->rank()+1);
    if (!loop) {
        // No loop, we can keep it as uncutable
        // Commit the new ranks we calculated
        // Just cleanup the list.  If this is slow, we can add another set of
        // user counters to avoid cleaning up the list.
        while (workBeginp()) {
            workPop();
        }
    } else {
        // Adding this edge would cause a loop, kill it
        edgep->cutable(true);  // So graph still looks pretty
        cutOrigEdge(edgep, "  Cut loop");
        edgep->unlinkDelete(); VL_DANGLING(edgep);
        // Back out the ranks we calculated
        while (GraphAcycVertex* vertexp = workBeginp()) {
            workPop();
            vertexp->rank(vertexp->m_storedRank);
        }
    }
}

bool GraphAcyc::placeIterate(GraphAcycVertex* vertexp, uint32_t currentRank) {
    // Assign rank to each unvisited node
    //   rank() is the "committed rank" of the graph known without loops
    // If larger rank is found, assign it and loop back through
    // If we hit a back node make a list of all loops
    if (vertexp->rank() >= currentRank) return false;  // Already processed it
    if (vertexp->user() == m_placeStep) return true;  // Loop detected
    vertexp->user(m_placeStep);
    // Remember we're changing the rank of this node; might need to back out
    if (!vertexp->m_onWorkList) {
        vertexp->m_storedRank = vertexp->rank();
        workPush(vertexp);
    }
    vertexp->rank(currentRank);
    // Follow all edges and increase their ranks
    for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
        if (edgep->weight() && !edgep->cutable()) {
            if (placeIterate(static_cast<GraphAcycVertex*>(edgep->top()), currentRank+1)) {
                // We don't need to reset user(); we'll use a different placeStep for the next edge
                return true;  // Loop detected
            }
        }
    }
    vertexp->user(0);
    return false;
}

//----- Main algorithm entry point

void GraphAcyc::main() {
    m_breakGraph.userClearEdges();

    // Color based on possible loops
    m_origGraphp->stronglyConnected(m_origEdgeFuncp);

    // Make a new graph with vertices that have only a single vertex
    // for each group of old vertices that are interconnected with unbreakable
    // edges (and thus can't represent loops - if we did the unbreakable
    // marking right, anyways)
    buildGraph(m_origGraphp);
    if (debug()>=6) m_breakGraph.dumpDotFilePrefixed("acyc_pre");

    // Perform simple optimizations before any cuttings
    simplify(false);
    if (debug()>=5) m_breakGraph.dumpDotFilePrefixed("acyc_simp");

    UINFO(4, " Cutting trivial loops\n");
    simplify(true);
    if (debug()>=6) m_breakGraph.dumpDotFilePrefixed("acyc_mid");

    UINFO(4, " Ranking\n");
    m_breakGraph.rank(&V3GraphEdge::followNotCutable);
    if (debug()>=6) m_breakGraph.dumpDotFilePrefixed("acyc_rank");

    UINFO(4, " Placement\n");
    place();
    if (debug()>=6) m_breakGraph.dumpDotFilePrefixed("acyc_place");

    UINFO(4, " Final Ranking\n");
    // Only needed to assert there are no loops in completed graph
    m_breakGraph.rank(&V3GraphEdge::followAlwaysTrue);
    if (debug()>=6) m_breakGraph.dumpDotFilePrefixed("acyc_done");
}

void V3Graph::acyclic(V3EdgeFuncP edgeFuncp) {
    UINFO(4, "Acyclic\n");
    GraphAcyc acyc (this, edgeFuncp);
    acyc.main();
    UINFO(4, "Acyclic done\n");
}
