// VISITs
    virtual void visit(AstNetlist* nodep, AstNUser*) {
	AstNode::user1ClearTree();
	readModNames();
	nodep->iterateChildren(*this);
	// Find levels in graph
	m_graph.removeRedundantEdges(&V3GraphEdge::followAlwaysTrue);
	m_graph.dumpDotFilePrefixed("linkcells");
	m_graph.rank();
	for (V3GraphVertex* itp = m_graph.verticesBeginp(); itp; itp=itp->verticesNextp()) {
	    if (LinkCellsVertex* vvertexp = dynamic_cast<LinkCellsVertex*>(itp)) {
		// +1 so we leave level 1  for the new wrapper we'll make in a moment
		AstNodeModule* modp = vvertexp->modp();
		modp->level(vvertexp->rank()+1);
		if (vvertexp == m_topVertexp && modp->level() != 2) {
		    AstNodeModule* abovep = NULL;
		    if (V3GraphEdge* edgep = vvertexp->inBeginp()) {
			if (LinkCellsVertex* eFromVertexp = dynamic_cast<LinkCellsVertex*>(edgep->fromp())) {
			    abovep = eFromVertexp->modp();
			}
		    }
		    v3error("Specified --top-module '"<<v3Global.opt.topModule()
			    <<"' isn't at the top level, it's under another cell '"
			    <<(abovep ? abovep->prettyName() : "UNKNOWN")<<"'");
		}
	    }
	}
	if (v3Global.opt.topModule()!=""
	    && !m_topVertexp) {
	    v3error("Specified --top-module '"<<v3Global.opt.topModule()<<"' was not found in design.");
	}
    }

void GateVisitor::warnSignals() {
    AstNode::user2ClearTree();
    for (V3GraphVertex* itp = m_graph.verticesBeginp(); itp; itp=itp->verticesNextp()) {
	if (GateVarVertex* vvertexp = dynamic_cast<GateVarVertex*>(itp)) {
	    AstVarScope* vscp = vvertexp->varScp();
	    AstNode* sp = vvertexp->rstSyncNodep();
	    AstNode* ap = vvertexp->rstAsyncNodep();
	    if (ap && sp && !vscp->varp()->user2()) {
		// This is somewhat wrong, as marking one flop as ok for sync
		// may mean a different flop now fails.  However it's a pain to
		// then report a warning in a new place - we should report them all at once.
		// Instead we'll disable if any disabled
		if (!vscp->fileline()->warnIsOff(V3ErrorCode::SYNCASYNCNET)
		    && !ap->fileline()->warnIsOff(V3ErrorCode::SYNCASYNCNET)
		    && !sp->fileline()->warnIsOff(V3ErrorCode::SYNCASYNCNET)
		    ) {
		    vscp->varp()->user2(true);  // Warn only once per signal
		    vscp->v3warn(SYNCASYNCNET,"Signal flopped as both synchronous and async: "<<vscp->prettyName()<<endl
				 <<ap->warnMore()<<"... Location of async usage"<<endl
				 <<sp->warnMore()<<"... Location of sync usage"<<endl);
		}
	    }
	}
    }
}

    void newAlwaysTrees(AstAlways* nodep) {
	// Across all variables we're moving
	uint32_t lastColor = 0;
	AstNode* lastExprp = NULL;
	for (V3GraphVertex* vertexp = m_graph.verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	    if (GaterVarVertex* vVxp = dynamic_cast<GaterVarVertex*>(vertexp)) {
		if (!lastExprp || lastColor != vVxp->color()) {
		    lastColor = vVxp->color();
		    // Create the block we've just finished
		    if (lastExprp) newAlwaysTree(nodep, lastExprp); // Duplicate below
		    // New expression for this color
		    lastExprp = newExprFromGraph(vVxp);
		}
		// Mark variable to move
		if (vVxp->nodep()->user2p()) vVxp->nodep()->v3fatalSrc("One variable got marked under two gaters");
		vVxp->nodep()->user2p(lastExprp);
		m_statBits += vVxp->nodep()->width();  // Moving a wide bus counts more!
		// There shouldn't be two possibilities we want to
		// move to, IE {A,B} <= Z because we marked such
		// things as unoptimizable
	    }
	}
	// Create the final block we've just finished
	if (lastExprp) newAlwaysTree(nodep, lastExprp);   // Duplicate above
    }

void V3Graph::userClearEdges() {
    // Clear user() in all of tree
    for (V3GraphVertex* vertexp = verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
	    edgep->user(0);
	    edgep->userp(NULL);	 // Its a union, but might be different size than user()
	}
    }
}

void GateVisitor::mergeAssigns() {
    GateMergeAssignsGraphVisitor merger(&m_graph);
    for (V3GraphVertex* itp = m_graph.verticesBeginp(); itp; itp=itp->verticesNextp()) {
	if (GateVarVertex* vvertexp = dynamic_cast<GateVarVertex*>(itp)) {
	    merger.mergeAssignsTree(vvertexp);
	}
    }
    m_statAssignMerged += merger.numMergedAssigns();
}

void GateVisitor::consumedMark() {
    // Propagate consumed signals backwards to all producers into a consumed node
    m_graph.userClearVertices();
    for (V3GraphVertex* vertexp = m_graph.verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	GateEitherVertex* evertexp = (GateEitherVertex*)vertexp;
	if (!evertexp->user() && evertexp->consumed()) {
	    consumedMarkRecurse(evertexp);
	}
    }
}

 void dumpGraph(std::ostream& os, const string& nameComment) const {
     // UINFO(0) as controlled by caller
     os<<"At "<<nameComment<<", dumping graph. Keys:\n";
     for (V3GraphVertex* vxp = verticesBeginp(); vxp; vxp = vxp->verticesNextp()) {
         Vertex* tspvp = castVertexp(vxp);
         os<<" "<<tspvp->key()<<endl;
         for (V3GraphEdge* edgep = tspvp->outBeginp(); edgep; edgep = edgep->outNextp()) {
             Vertex* neighborp = castVertexp(edgep->top());
             os<<"   has edge "<<edgep->user()<<" to "<<neighborp->key()<<endl;
         }
     }
 }

 void combineGraph(const TspGraphTmpl& g) {
     vl_unordered_set<vluint32_t> edges_done;
     for (V3GraphVertex* vxp = g.verticesBeginp(); vxp; vxp = vxp->verticesNextp()) {
         Vertex* fromp = castVertexp(vxp);
         for (V3GraphEdge* edgep = fromp->outBeginp(); edgep; edgep = edgep->outNextp()) {
             Vertex* top = castVertexp(edgep->top());
             if (edges_done.find(edgep->user()) == edges_done.end()) {
                 addEdge(fromp->key(), top->key(), edgep->weight());
                 edges_done.insert(edgep->user());
             }
         }
     }
 }

    void optimize_accepting_out() {
	// Delete outbound edges from accepting states
	// (As once we've accepted, we no longer care about anything else.)
	for (V3GraphVertex* vertexp = m_graphp->verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	    if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
		if (vvertexp->accepting()) {
		    for (V3GraphEdge* nextp,*edgep = vertexp->outBeginp(); edgep; edgep=nextp) {
			nextp = edgep->outNextp();
			edgep->unlinkDelete(); edgep=NULL;
		    }
		}
	    }
	}
    }

 std::vector<T_Key> getOddDegreeKeys() const {
     std::vector<T_Key> result;
     for (V3GraphVertex* vxp = verticesBeginp(); vxp; vxp = vxp->verticesNextp()) {
         Vertex* tspvp = castVertexp(vxp);
         vluint32_t degree = 0;
         for (V3GraphEdge* edgep = vxp->outBeginp(); edgep; edgep = edgep->outNextp()) {
             degree++;
         }
         if (degree & 1) {
             result.push_back(tspvp->key());
         }
     }
     return result;
 }

    // VISITORS
    virtual void visit(AstAlways* nodep, AstNUser*) {
	if (debug()>=9) cout<<endl<<endl<<endl;
	UINFO(5, "Gater: ALWAYS: "<<nodep<<endl);
	if (nodep->user4Inc()) return;

	clear();

	if (debug()>=9) nodep->dumpTree(cout,"  Alwin:  ");

	// Look for constructs we can't optimize
	// Form graph with Vertices at each IF, and each Variable
	m_aboveTrue = VU_IF | VU_ELSE;
	iterateChildrenAlw(nodep, true);

	// Other reasons to not optimize
	if (!m_numIfs) nonOptimizable(nodep, "No if statements");

	// Something to optimize, oh my!
	if (m_nonopt!="") {
	    UINFO(5, "  Gater non-opt: "<<m_nonopt<<endl);
	} else {
	    // Process it
	    simplifyGraph();

	    // See how much moves
	    uint32_t lastColor = 0;
	    for (V3GraphVertex* vertexp = m_graph.verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
		if (GaterVarVertex* vVxp = dynamic_cast<GaterVarVertex*>(vertexp)) {
		    if (lastColor < vVxp->color()) {
			lastColor = vVxp->color();
		    }
		}
	    }
	    if (lastColor == 0) { // Nothing we moved!
		nonOptimizable(nodep, "Nothing moved");
	    }
	    else if (lastColor > DOMAINS_MAX) {
		// Our move algorithm is fairly slow and if we're splitting
		// up too much it'll get really nasty.  It's probably a bad
		// move for performance to split too much, anyhow, as the
		// number of gaters will result in calling many small c functions.
		nonOptimizable(nodep, "Too much moved");
	    }
	    if (m_nonopt=="") {
		newAlwaysTrees(nodep);
		if (debug()>=9) nodep->dumpTree(cout,"  Gaterout: ");
	    }
	}
	UINFO(5, "  Gater done"<<endl);
    }

DfaVertex* DfaGraph::findStart() {
    DfaVertex* startp = NULL;
    for (V3GraphVertex* vertexp = this->verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
	    if (vvertexp->start()) {
		if (startp) v3fatalSrc("Multiple start points in NFA graph");
		startp = vvertexp;
	    }
	} else {
	    v3fatalSrc("Non DfaVertex in DfaGraph\n");
	}
    }
    if (!startp) v3fatalSrc("No start point in NFA graph");
    return startp;
}

    void simplifyGrandRecurse(V3GraphVertex* vertexp, uint32_t depth) {
	// From top-down delete any vars that grandparents source
	// IE    A -> B -> C -> VAR
	//         \----------^
	//UINFO(9,"GRecurse "<<depth<<" "<<vertexp<<endl);
	// Mark all variables to be swept
	for (V3GraphEdge *nextp, *edgep = vertexp->outBeginp(); edgep; edgep=nextp) {
	    nextp = edgep->outNextp();  // We may edit the list
	    if (GaterVarVertex* toVxp = dynamic_cast<GaterVarVertex*>(edgep->top())) {
		if (toVxp->user() && toVxp->user() < depth) {
		    // A recursion "above" us marked it,
		    // Remove this edge, it's redundant with the upper edge
		    edgep->unlinkDelete(); edgep=NULL;
		} else {
		    GaterEdge* cedgep = static_cast<GaterEdge*>(edgep);
		    if (cedgep->ifelseBoth()) {
			toVxp->user(depth);
		    }
		}
	    }
	}
	// Recurse
	for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
	    simplifyGrandRecurse(edgep->top(), depth+1);
	}
	// Clean our marks
	for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
	    V3GraphVertex* toVxp = edgep->top();
	    if (toVxp->user() && toVxp->user() < depth) {  // A recursion "above" us marked it; don't mess with it
	    } else {
		toVxp->user(0);  // We marked it originally, so unmark now
	    }
	}
	// Delete any If nodes with no children
	// Last, as want bottom-up cleanup
	for (V3GraphEdge *nextp, *edgep = vertexp->outBeginp(); edgep; edgep=nextp) {
	    nextp = edgep->outNextp();  // We may edit the list
	    if (GaterIfVertex* toVxp = dynamic_cast<GaterIfVertex*>(edgep->top())) {
		if (!toVxp->outBeginp()) {
		    if (!nextp || nextp->top() != edgep->top()) {  // Else next would disappear; we'll do it next loop
			toVxp->unlinkDelete(&m_graph); toVxp=NULL; edgep=NULL;
		    }
		}
	    }
	}
    }

 void pruneDepsOnInputs() {
     for (V3GraphVertex* vertexp = m_graph.verticesBeginp();
          vertexp; vertexp=vertexp->verticesNextp()) {
         if (!vertexp->outBeginp()
             && dynamic_cast<SplitVarStdVertex*>(vertexp)) {
             if (debug() >= 9) {
                 SplitVarStdVertex* stdp = (SplitVarStdVertex*)(vertexp);
                 UINFO(0, "Will prune deps on var "<<stdp->nodep()<<endl);
                 stdp->nodep()->dumpTree(cout, "- ");
             }
             for (V3GraphEdge* edgep = vertexp->inBeginp();
                  edgep; edgep=edgep->inNextp()) {
                 SplitEdge* oedgep = dynamic_cast<SplitEdge*>(edgep);
                 oedgep->setIgnoreThisStep();
             }
         }
     }
 }

    void add_complement_edges() {
	// Find accepting vertex
	DfaVertex* acceptp = NULL;
	for (V3GraphVertex* vertexp = m_graphp->verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	    if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
		if (vvertexp->accepting()) {
		    acceptp = vvertexp;
		    break;
		}
	    }
	}
	if (!acceptp) v3fatalSrc("No accepting vertex in DFA\n");

	// Remap edges
	for (V3GraphVertex* vertexp = m_graphp->verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	    if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
		//UINFO(9, "   on vertex "<<vvertexp->name()<<endl);
		if (!vvertexp->accepting() && vvertexp != m_tempNewerReject) {
		    for (V3GraphEdge* nextp, *edgep = vertexp->outBeginp(); edgep; edgep=nextp) {
			nextp = edgep->outNextp();
			if (!edgep->user()) { // Not processed
			    // Old edges to accept now go to new reject
			    DfaEdge* vedgep = static_cast<DfaEdge*>(edgep);
			    DfaVertex* tovertexp = static_cast<DfaVertex*>(edgep->top());
			    if (tovertexp->accepting()) {
				new DfaEdge(graphp(), vvertexp, m_tempNewerReject, vedgep);
				edgep->unlinkDelete(); edgep=NULL;
			    }

			    // NOT of all values goes to accept
			    // We make a edge for each value to OR, IE
			    // edge(complemented,a) edge(complemented,b) means !(a | b)
			    if (!tovertexp->accepting()) {  // Note we must include edges moved above to reject
				DfaEdge* newp = new DfaEdge (graphp(), vvertexp, acceptp, vedgep);
				newp->complement(!newp->complement());
				newp->user(1);
			    }
			}
		    }
		}
	    }
	}
    }

void GateVisitor::consumedMove() {
    // Remove unused logic (logic that doesn't hit a combo block or a display statement)
    // We need the "usually" block logic to do a better job at this
    for (V3GraphVertex* vertexp = m_graph.verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	if (GateVarVertex* vvertexp = dynamic_cast<GateVarVertex*>(vertexp)) {
	    if (!vvertexp->consumed() && !vvertexp->user()) {
		UINFO(8, "Unconsumed "<<vvertexp->varScp()<<endl);
	    }
	}
	if (GateLogicVertex* lvertexp = dynamic_cast<GateLogicVertex*>(vertexp)) {
	    AstNode* nodep = lvertexp->nodep();
	    AstActive* oldactp = lvertexp->activep();  // NULL under cfunc
	    if (!lvertexp->consumed() && oldactp) {
		// Eventually: Move the statement to a new active block with "tracing-on" sensitivity
		UINFO(8,"    Remove unconsumed "<<nodep<<endl);
		nodep->unlinkFrBack();
		pushDeletep(nodep); VL_DANGLING(nodep);
	    }
	}
    }
}

void GateVisitor::dedupe() {
    AstNode::user2ClearTree();
    GateDedupeGraphVisitor deduper;
    // Traverse starting from each of the clocks
    for (V3GraphVertex* itp = m_graph.verticesBeginp(); itp; itp=itp->verticesNextp()) {
	if (GateVarVertex* vvertexp = dynamic_cast<GateVarVertex*>(itp)) {
	    if (vvertexp->isClock()) {
		deduper.dedupeTree(vvertexp);
	    }
	}
    }
    // Traverse starting from each of the outputs
    for (V3GraphVertex* itp = m_graph.verticesBeginp(); itp; itp=itp->verticesNextp()) {
	if (GateVarVertex* vvertexp = dynamic_cast<GateVarVertex*>(itp)) {
	    if (vvertexp->isTop() && vvertexp->varScp()->varp()->isOutput()) {
		deduper.dedupeTree(vvertexp);
	    }
	}
    }
    m_statDedupLogic += deduper.numDeduped();
}

    void optimize_no_outbound() {
	// Non-accepting states with no outbound transitions may be
	// deleted.  Then, any arcs feeding those states, and perhaps those
	// states...

	// Vertex::m_user begin: 1 indicates on the work list
	// (Otherwise we might have nodes on the list twice, and reference after deleting them.)
	m_graphp->userClearVertices();

	// Find all dead vertexes
	stack<DfaVertex*> workps;
	for (V3GraphVertex* vertexp = m_graphp->verticesBeginp(); vertexp; vertexp=vertexp->verticesNextp()) {
	    if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
		workps.push(vvertexp);
		vertexp->user(1);
	    } else {
		// If ever remove this, need dyn cast below
		v3fatalSrc("Non DfaVertex in dfa graph");
	    }
	}

	// While deadness... Delete and find new dead nodes.
	while (!workps.empty()) {
	    DfaVertex* vertexp = workps.top(); workps.pop();
	    vertexp->user(0);
	    if (isDead(vertexp)) {
		// Add nodes that go here to the work list
		for (V3GraphEdge* edgep = vertexp->inBeginp(); edgep; edgep=edgep->inNextp()) {
		    DfaVertex* fromvertexp = static_cast<DfaVertex*>(edgep->fromp());
		    if (fromvertexp != vertexp
			&& !fromvertexp->user()) {
			workps.push(static_cast<DfaVertex*>(fromvertexp));
			fromvertexp->user(1);
		    }
		}
		// Transitions to this state removed by the unlink function
		vertexp->unlinkDelete(m_graphp); vertexp=NULL;
	    }
	}
    }

    void optimize_orphans() {
	// Remove states that don't come from start
	// Presumably the previous optimization orphaned them.

	// Vertex::m_user begin: 1 indicates on the work list, 2 processed
	// (Otherwise we might have nodes on the list twice, and reference after deleting them.)
	m_graphp->userClearVertices();

	DfaVertex* startp = graphp()->findStart();
	stack<V3GraphVertex*> workps;  workps.push(startp);

	// Mark all nodes connected to start
	while (!workps.empty()) {
	    V3GraphVertex* vertexp = workps.top(); workps.pop();
	    vertexp->user(2);  // Processed
	    // Add nodes from here to the work list
	    for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
		V3GraphVertex* tovertexp = edgep->top();
		if (!tovertexp->user()) {
		    workps.push(tovertexp);
		    tovertexp->user(1);
		}
	    }
	}

	// Delete all nodes not connected
	for (V3GraphVertex* nextp,*vertexp = m_graphp->verticesBeginp(); vertexp; vertexp=nextp) {
	    nextp = vertexp->verticesNextp();
	    if (!vertexp->user()) {
		vertexp->unlinkDelete(m_graphp); vertexp=NULL;
	    }
	}
    }

void GateVisitor::replaceAssigns() {
    for (V3GraphVertex* itp = m_graph.verticesBeginp(); itp; itp=itp->verticesNextp()) {
	if (GateVarVertex* vvertexp = dynamic_cast<GateVarVertex*>(itp)) {
	    // Take the Comments/assigns that were moved to the VarScope and change them to a
	    // simple value assignment
	    AstVarScope* vscp = vvertexp->varScp();
	    if (vscp->valuep() && !vscp->valuep()->castNodeMath()) {
		//if (debug()>9) vscp->dumpTree(cout, "-vscPre:  ");
		while (AstNode* delp=vscp->valuep()->castComment()) {
		    delp->unlinkFrBack()->deleteTree(); VL_DANGLING(delp);
		}
		if (AstInitial* delp=vscp->valuep()->castInitial()) {
		    AstNode* bodyp=delp->bodysp();
		    bodyp->unlinkFrBackWithNext();
		    delp->replaceWith(bodyp);
		    delp->deleteTree(); VL_DANGLING(delp);
		}
		if (AstAlways* delp=vscp->valuep()->castAlways()) {
		    AstNode* bodyp=delp->bodysp();
		    bodyp->unlinkFrBackWithNext();
		    delp->replaceWith(bodyp);
		    delp->deleteTree(); VL_DANGLING(delp);
		}
		if (AstNodeAssign* delp=vscp->valuep()->castNodeAssign()) {
		    AstNode* rhsp=delp->rhsp();
		    rhsp->unlinkFrBack();
		    delp->replaceWith(rhsp);
		    delp->deleteTree(); VL_DANGLING(delp);
		}
		//if (debug()>9) {vscp->dumpTree(cout, "-vscDone: "); cout<<endl;}
		if (!vscp->valuep()->castNodeMath()
		    || vscp->valuep()->nextp()) {
		    vscp->dumpTree(cerr, "vscStrange: ");
		    vscp->v3fatalSrc("Value of varscope not mathematical\n");
		}
	    }
	}
    }
}