verilator/src/V3Trace.cpp

// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Waves tracing
//
// Code available from: https://verilator.org
//
//*************************************************************************
//
// Copyright 2003-2025 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.
// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
//
//*************************************************************************
// V3Trace's Transformations:
//
//  Examine whole design and build a graph describing which function call
//  may result in a write to a traced variable. This is done in 2 passes:
//
//  Pass 1:
//      Add vertices for TraceDecl, CFunc, CCall and VarRef nodes, add
//      edges from CCall -> CFunc, VarRef -> TraceDecl, also add edges
//      for public entry points to CFuncs (these are like a spontaneous
//      call)
//
//  Pass 2:
//      Add edges from CFunc -> VarRef being written
//
//  Finally:
//      Process graph to determine when traced variables can change, allocate
//      activity flags, insert nodes to set activity flags, allocate signal
//      numbers (codes), and construct the const, full and incremental trace
//      functions, together with all other trace support functions.
//
//*************************************************************************

#include "V3PchAstNoMT.h"  // VL_MT_DISABLED_CODE_UNIT

#include "V3Trace.h"

#include "V3DupFinder.h"
#include "V3EmitCBase.h"
#include "V3Graph.h"
#include "V3Stats.h"

#include <limits>
#include <set>

VL_DEFINE_DEBUG_FUNCTIONS;

//######################################################################
// Graph vertexes

class TraceActivityVertex final : public V3GraphVertex {
    VL_RTTI_IMPL(TraceActivityVertex, V3GraphVertex)
    AstNode* const m_insertp;
    int32_t m_activityCode;
    bool m_slow;  // If always slow, we can use the same code
public:
    enum { ACTIVITY_NEVER = ((1UL << 31) - 1) };
    enum { ACTIVITY_ALWAYS = ((1UL << 31) - 2) };
    enum { ACTIVITY_SLOW = 0 };
    TraceActivityVertex(V3Graph* graphp, AstNode* nodep, bool slow)
        : V3GraphVertex{graphp}
        , m_insertp{nodep} {
        m_activityCode = 0;
        m_slow = slow;
    }
    TraceActivityVertex(V3Graph* graphp, int32_t code)
        : V3GraphVertex{graphp}
        , m_insertp{nullptr} {
        m_activityCode = code;
        m_slow = false;
    }
    ~TraceActivityVertex() override = default;
    // ACCESSORS
    AstNode* insertp() const {
        UASSERT(m_insertp, "Null insertp; probably called on a special always/slow");
        return m_insertp;
    }
    string name() const override {
        if (activityAlways()) {
            return "*ALWAYS*";
        } else {
            return std::string{slow() ? "*SLOW* " : ""} + insertp()->name();
        }
    }
    string dotColor() const override { return slow() ? "yellowGreen" : "green"; }
    int32_t activityCode() const { return m_activityCode; }
    bool activityAlways() const { return activityCode() == ACTIVITY_ALWAYS; }
    bool activitySlow() const { return activityCode() == ACTIVITY_SLOW; }
    void activityCode(int32_t code) { m_activityCode = code; }
    bool slow() const { return m_slow; }
    void slow(bool flag) {
        if (!flag) m_slow = false;
    }
};

class TraceCFuncVertex final : public V3GraphVertex {
    VL_RTTI_IMPL(TraceCFuncVertex, V3GraphVertex)
    AstCFunc* const m_nodep;

public:
    TraceCFuncVertex(V3Graph* graphp, AstCFunc* nodep)
        : V3GraphVertex{graphp}
        , m_nodep{nodep} {}
    ~TraceCFuncVertex() override = default;
    // ACCESSORS
    AstCFunc* nodep() const { return m_nodep; }
    string name() const override { return nodep()->name(); }
    string dotColor() const override { return "yellow"; }
    FileLine* fileline() const override { return nodep()->fileline(); }
};

class TraceTraceVertex final : public V3GraphVertex {
    VL_RTTI_IMPL(TraceTraceVertex, V3GraphVertex)
    AstTraceDecl* const m_nodep;  // TRACEINC this represents
    // nullptr, or other vertex with the real code() that duplicates this one
    TraceTraceVertex* m_duplicatep = nullptr;

public:
    TraceTraceVertex(V3Graph* graphp, AstTraceDecl* nodep)
        : V3GraphVertex{graphp}
        , m_nodep{nodep} {}
    ~TraceTraceVertex() override = default;
    // ACCESSORS
    AstTraceDecl* nodep() const { return m_nodep; }
    string name() const override { return nodep()->name(); }
    string dotColor() const override { return "red"; }
    FileLine* fileline() const override { return nodep()->fileline(); }
    TraceTraceVertex* duplicatep() const { return m_duplicatep; }
    void duplicatep(TraceTraceVertex* dupp) {
        UASSERT_OBJ(!duplicatep(), nodep(), "Assigning duplicatep() to already duplicated node");
        m_duplicatep = dupp;
    }
};

class TraceVarVertex final : public V3GraphVertex {
    VL_RTTI_IMPL(TraceVarVertex, V3GraphVertex)
    AstVarScope* const m_nodep;

public:
    TraceVarVertex(V3Graph* graphp, AstVarScope* nodep)
        : V3GraphVertex{graphp}
        , m_nodep{nodep} {}
    ~TraceVarVertex() override = default;
    // ACCESSORS
    AstVarScope* nodep() const { return m_nodep; }
    string name() const override { return nodep()->name(); }
    string dotColor() const override { return "skyblue"; }
    FileLine* fileline() const override { return nodep()->fileline(); }
};

//######################################################################
// Trace state, as a visitor of each AstNode

class TraceVisitor final : public VNVisitor {
    // NODE STATE
    // V3Hasher in V3DupFinder
    //  Ast*::user4()                   // V3Hasher calculation
    // Cleared entire netlist
    //  AstCFunc::user1()               // V3GraphVertex* for this node
    //  AstTraceDecl::user1()           // V3GraphVertex* for this node
    //  AstVarScope::user1()            // V3GraphVertex* for this node
    //  AstStmtExpr::user2()            // bool; walked next list for other ccalls
    //  Ast*::user3()                   // TraceActivityVertex* for this node
    const VNUser1InUse m_inuser1;
    const VNUser2InUse m_inuser2;
    const VNUser3InUse m_inuser3;
    // VNUser4InUse     In V3Hasher via V3DupFinder

    // STATE
    AstNodeModule* m_topModp = nullptr;  // Module to add variables to
    AstScope* const m_topScopep = v3Global.rootp()->topScopep()->scopep();  // The top AstScope
    AstCFunc* m_cfuncp = nullptr;  // C function adding to graph
    AstCFunc* m_regFuncp = nullptr;  // Trace registration function
    AstCFunc* m_actAllFuncp = nullptr;  // Set all activity function
    AstTraceDecl* m_tracep = nullptr;  // Trace function adding to graph
    AstVarScope* m_activityVscp = nullptr;  // Activity variable
    uint32_t m_activityNumber = 0;  // Count of fields in activity variable
    uint32_t m_code = 0;  // Trace ident code# being assigned
    V3Graph m_graph;  // Var/CFunc tracking
    TraceActivityVertex* const m_alwaysVtxp;  // "Always trace" vertex
    bool m_finding = false;  // Pass one of algorithm?

    // Trace parallelism. Only VCD tracing can be parallelized at this time.
    const uint32_t m_parallelism
        = v3Global.opt.useTraceParallel() ? static_cast<uint32_t>(v3Global.opt.threads()) : 1;

    VDouble0 m_statSetters;  // Statistic tracking
    VDouble0 m_statSettersSlow;  // Statistic tracking
    VDouble0 m_statUniqCodes;  // Statistic tracking
    VDouble0 m_statUniqSigs;  // Statistic tracking

    // All activity numbers applying to a given trace
    using ActCodeSet = std::set<uint32_t>;
    // For activity set, what traces apply
    using TraceVec = std::multimap<ActCodeSet, TraceTraceVertex*>;

    // METHODS

    void detectDuplicates() {
        UINFO(9, "Finding duplicates");
        // Note uses user4
        V3DupFinder dupFinder;  // Duplicate code detection
        // Hash all of the traced values and find if there are any duplicates
        for (V3GraphVertex& vtx : m_graph.vertices()) {
            if (TraceTraceVertex* const vvertexp = vtx.cast<TraceTraceVertex>()) {
                const AstTraceDecl* const nodep = vvertexp->nodep();
                UASSERT_OBJ(!vvertexp->duplicatep(), nodep, "Should not be a duplicate");
                const auto dupit = dupFinder.findDuplicate(nodep->valuep());
                if (dupit == dupFinder.end()) {
                    dupFinder.insert(nodep->valuep());
                } else {
                    const AstTraceDecl* const dupDeclp = VN_AS(dupit->second->backp(), TraceDecl);
                    UASSERT_OBJ(dupDeclp, nodep, "Trace duplicate of wrong type");
                    TraceTraceVertex* const dupvertexp
                        = dupDeclp->user1u().toGraphVertex()->cast<TraceTraceVertex>();
                    UINFO(8, "  Orig " << nodep);
                    UINFO(8, "   dup " << dupDeclp);
                    // Mark the hashed node as the original and our
                    // iterating node as duplicated
                    vvertexp->duplicatep(dupvertexp);
                }
            }
        }
        if (dumpLevel() || debug() >= 9)
            dupFinder.dumpFile(v3Global.debugFilename("trace") + ".hash", false);
    }

    void graphSimplify(bool initial) {
        if (initial) {
            // Remove all variable nodes
            for (V3GraphVertex* const vtxp : m_graph.vertices().unlinkable()) {
                if (TraceVarVertex* const vvertexp = vtxp->cast<TraceVarVertex>()) {
                    vvertexp->rerouteEdges(&m_graph);
                    vvertexp->unlinkDelete(&m_graph);
                }
            }
            // Remove multiple variables connecting funcs to traces
            // We do this twice, as then we have fewer edges to multiply out in the below
            // expansion.
            m_graph.removeRedundantEdgesMax(&V3GraphEdge::followAlwaysTrue);
            // Remove all Cfunc nodes
            for (V3GraphVertex* const vtxp : m_graph.vertices().unlinkable()) {
                if (TraceCFuncVertex* const vvertexp = vtxp->cast<TraceCFuncVertex>()) {
                    vvertexp->rerouteEdges(&m_graph);
                    vvertexp->unlinkDelete(&m_graph);
                }
            }
        }

        // Remove multiple variables connecting funcs to traces
        m_graph.removeRedundantEdgesMax(&V3GraphEdge::followAlwaysTrue);

        // If there are any edges from a always, keep only the always
        for (V3GraphVertex& vtx : m_graph.vertices()) {
            if (TraceTraceVertex* const vvertexp = vtx.cast<TraceTraceVertex>()) {
                // Search for the incoming always edge
                const V3GraphEdge* alwaysEdgep = nullptr;
                for (const V3GraphEdge& edge : vvertexp->inEdges()) {
                    const TraceActivityVertex* const actVtxp
                        = edge.fromp()->as<const TraceActivityVertex>();
                    if (actVtxp->activityAlways()) {
                        alwaysEdgep = &edge;
                        break;
                    }
                }
                // If always edge exists, remove all other edges
                if (alwaysEdgep) {
                    for (V3GraphEdge* const edgep : vvertexp->inEdges().unlinkable()) {
                        if (edgep != alwaysEdgep) VL_DO_DANGLING(edgep->unlinkDelete(), edgep);
                    }
                }
            }
        }

        // Activity points with no outputs can be removed
        for (V3GraphVertex* const vtxp : m_graph.vertices().unlinkable()) {
            if (TraceActivityVertex* const aVtxp = vtxp->cast<TraceActivityVertex>()) {
                // Leave in the always vertex for later use.
                if (aVtxp != m_alwaysVtxp && aVtxp->outEmpty()) {
                    VL_DO_DANGLING(aVtxp->unlinkDelete(&m_graph), aVtxp);
                }
            }
        }
    }

    uint32_t assignactivityNumbers() {
        uint32_t activityNumber = 1;  // Note 0 indicates "slow" only
        for (V3GraphVertex& vtx : m_graph.vertices()) {
            if (TraceActivityVertex* const vvertexp = vtx.cast<TraceActivityVertex>()) {
                if (vvertexp != m_alwaysVtxp) {
                    if (vvertexp->slow()) {
                        vvertexp->activityCode(TraceActivityVertex::ACTIVITY_SLOW);
                    } else {
                        vvertexp->activityCode(activityNumber++);
                    }
                }
            }
        }
        return activityNumber;
    }

    void sortTraces(TraceVec& traces, uint32_t& nNonConstCodes) {
        // Populate sort structure
        traces.clear();
        nNonConstCodes = 0;
        for (V3GraphVertex& vtx : m_graph.vertices()) {
            if (TraceTraceVertex* const vtxp = vtx.cast<TraceTraceVertex>()) {
                ActCodeSet actSet;
                UINFO(9, "  Add to sort: " << vtxp);
                UINFOTREE(9, vtxp->nodep(), "", "trnode");
                for (const V3GraphEdge& edge : vtxp->inEdges()) {
                    const TraceActivityVertex* const cfvertexp
                        = edge.fromp()->cast<const TraceActivityVertex>();
                    UASSERT_OBJ(cfvertexp, vtxp->nodep(),
                                "Should have been function pointing to this trace");
                    UINFO(9, "   Activity: " << cfvertexp);
                    if (cfvertexp->activityAlways()) {
                        // If code 0, we always trace; ignore other codes
                        actSet.insert(TraceActivityVertex::ACTIVITY_ALWAYS);
                    } else {
                        actSet.insert(cfvertexp->activityCode());
                    }
                }
                UASSERT_OBJ(actSet.count(TraceActivityVertex::ACTIVITY_ALWAYS) == 0
                                || actSet.size() == 1,
                            vtxp->nodep(), "Always active trace has further triggers");
                // Count nodes
                if (!vtxp->duplicatep() && !actSet.empty())
                    nNonConstCodes += vtxp->nodep()->codeInc();
                if (actSet.empty()) {
                    // If a trace doesn't have activity, it's constant, and we
                    // don't need to track changes on it.
                    actSet.insert(TraceActivityVertex::ACTIVITY_NEVER);
                } else if (actSet.count(TraceActivityVertex::ACTIVITY_SLOW) && actSet.size() > 1) {
                    // If a trace depends on the slow flag as well as other
                    // flags, remove the dependency on the slow flag. We will
                    // make slow routines set all activity flags.
                    actSet.erase(TraceActivityVertex::ACTIVITY_SLOW);
                }
                traces.emplace(actSet, vtxp);
            }
        }
    }

    void graphOptimize() {
        // Assign initial activity numbers to activity vertices
        assignactivityNumbers();

        // Sort the traces by activity sets
        TraceVec traces;
        uint32_t unused1;
        sortTraces(traces, unused1);

        // For each activity set with only a small number of signals, make those
        // signals always traced, as it's cheaper to check a few value changes
        // than to test a lot of activity flags
        auto it = traces.begin();
        const auto end = traces.end();
        while (it != end) {
            auto head = it;
            // Approximate the complexity of the value change check
            uint32_t complexity = 0;
            const ActCodeSet& actSet = it->first;
            for (; it != end && it->first == actSet; ++it) {
                if (!it->second->duplicatep()) {
                    uint32_t cost = 0;
                    const AstTraceDecl* const declp = it->second->nodep();
                    // The number of comparisons required by bufp->chg*
                    cost += declp->isWide() ? declp->codeInc() : 1;
                    // Arrays are traced by element
                    cost *= declp->arrayRange().ranged() ? declp->arrayRange().elements() : 1;
                    // Note: Experiments factoring in the size of declp->valuep()
                    // showed no benefit in tracing speed, even for large trees,
                    // so we will leave those out for now.
                    complexity += cost;
                }
            }
            // Leave alone always changing, never changing and signals only set in slow code
            if (actSet.count(TraceActivityVertex::ACTIVITY_ALWAYS)) continue;
            if (actSet.count(TraceActivityVertex::ACTIVITY_NEVER)) continue;
            if (actSet.count(TraceActivityVertex::ACTIVITY_SLOW)) continue;
            // If the value comparisons are cheaper to perform than checking the
            // activity flags make the signals always traced. Note this cost
            // equation is heuristic.
            if (complexity <= actSet.size() * 2) {
                for (; head != it; ++head) {
                    new V3GraphEdge{&m_graph, m_alwaysVtxp, head->second, 1};
                }
            }
        }

        graphSimplify(false);
    }

    AstNodeExpr* selectActivity(FileLine* flp, uint32_t acode, const VAccess& access) {
        return new AstArraySel(flp, new AstVarRef{flp, m_activityVscp, access}, acode);
    }

    AstNode* newActivitySetter(AstNode* insertp, uint32_t code) {
        ++m_statSetters;
        FileLine* const fl = insertp->fileline();
        AstAssign* const setterp = new AstAssign{fl, selectActivity(fl, code, VAccess::WRITE),
                                                 new AstConst{fl, AstConst::BitTrue{}}};
        return setterp;
    }

    AstNode* newActivityAll(AstNode* insertp) {
        ++m_statSettersSlow;
        if (!m_actAllFuncp) {
            FileLine* const flp = m_topScopep->fileline();
            AstCFunc* const funcp = new AstCFunc{flp, "__Vm_traceActivitySetAll", m_topScopep};
            funcp->slow(true);
            funcp->isStatic(false);
            funcp->isLoose(true);
            m_topScopep->addBlocksp(funcp);
            for (uint32_t code = 0; code < m_activityNumber; ++code) {
                AstNode* const setterp = newActivitySetter(insertp, code);
                funcp->addStmtsp(setterp);
            }
            m_actAllFuncp = funcp;
        }
        AstCCall* const callp = new AstCCall{insertp->fileline(), m_actAllFuncp};
        callp->dtypeSetVoid();
        return callp->makeStmt();
    }

    void createActivityFlags() {
        // Assign final activity numbers
        m_activityNumber = assignactivityNumbers();

        // Create an array of bytes, not a bit vector, as they can be set
        // atomically by mtasks, and are cheaper to set (no need for
        // read-modify-write on the C type), and the speed of the tracing code
        // is the same on largish designs.
        FileLine* const flp = m_topScopep->fileline();
        AstNodeDType* const newScalarDtp = new AstBasicDType{flp, VFlagBitPacked{}, 1};
        v3Global.rootp()->typeTablep()->addTypesp(newScalarDtp);
        AstRange* const newArange
            = new AstRange{flp, VNumRange{static_cast<int>(m_activityNumber) - 1, 0}};
        AstNodeDType* const newArrDtp = new AstUnpackArrayDType{flp, newScalarDtp, newArange};
        v3Global.rootp()->typeTablep()->addTypesp(newArrDtp);
        AstVar* const newvarp
            = new AstVar{flp, VVarType::MODULETEMP, "__Vm_traceActivity", newArrDtp};
        m_topModp->addStmtsp(newvarp);
        AstVarScope* const newvscp = new AstVarScope{flp, m_topScopep, newvarp};
        m_topScopep->addVarsp(newvscp);
        m_activityVscp = newvscp;

        // Insert activity setters
        for (const V3GraphVertex& vtx : m_graph.vertices()) {
            if (const TraceActivityVertex* const vtxp = vtx.cast<const TraceActivityVertex>()) {
                AstNode* setterp = nullptr;
                if (vtxp->activitySlow()) {
                    setterp = newActivityAll(vtxp->insertp());
                    // Just set all flags in slow code as it should be rare.
                    // This will be rolled up into a loop by V3Reloop.
                } else if (!vtxp->activityAlways()) {
                    setterp = newActivitySetter(vtxp->insertp(), vtxp->activityCode());
                }
                if (setterp) {
                    AstNode* const insertp = vtxp->insertp();
                    if (AstStmtExpr* const stmtp = VN_CAST(insertp, StmtExpr)) {
                        stmtp->addNextHere(setterp);
                    } else if (AstCFunc* const funcp = VN_CAST(insertp, CFunc)) {
                        // If there are awaits, insert the setter after each await
                        if (funcp->isCoroutine() && funcp->stmtsp()) {
                            funcp->stmtsp()->foreachAndNext([&](AstCAwait* awaitp) {
                                AstNode* stmtp = awaitp->backp();
                                while (VN_IS(stmtp, NodeExpr)) stmtp = stmtp->backp();
                                stmtp->addNextHere(setterp->cloneTree(false));
                            });
                        }
                        funcp->addStmtsp(setterp);
                    } else {
                        insertp->v3fatalSrc("Bad trace activity vertex");
                    }
                }
            }
        }
    }

    AstCFunc* newCFunc(VTraceType traceType, AstCFunc* topFuncp, uint32_t funcNum,
                       uint32_t baseCode = 0) {
        // Create new function
        const bool isTopFunc = topFuncp == nullptr;
        std::string funcName;
        if (isTopFunc) {
            if (traceType == VTraceType::CONSTANT) {
                funcName = "trace_const";
            } else if (traceType == VTraceType::FULL) {
                funcName = "trace_full";
            } else {
                funcName = "trace_chg";
            }
        } else {
            funcName = topFuncp->name();
            funcName += "_sub";
        }
        funcName += "_";
        funcName += cvtToStr(funcNum);

        FileLine* const flp = m_topScopep->fileline();
        AstCFunc* const funcp = new AstCFunc{flp, funcName, m_topScopep};
        funcp->isTrace(true);
        funcp->dontCombine(true);
        funcp->isLoose(true);
        funcp->slow(traceType != VTraceType::CHANGE);
        funcp->isStatic(isTopFunc);
        // Add it to top scope
        m_topScopep->addBlocksp(funcp);
        const std::string bufArg
            = v3Global.opt.traceClassBase()
              + "::" + (v3Global.opt.useTraceOffload() ? "OffloadBuffer" : "Buffer") + "* bufp";
        if (isTopFunc) {
            // Top functions
            funcp->argTypes("void* voidSelf, " + bufArg);
            funcp->addStmtsp(new AstCStmt{flp, EmitCUtil::voidSelfAssign(m_topModp)});
            funcp->addStmtsp(new AstCStmt{flp, EmitCUtil::symClassAssign()});
            // Add global activity check to change dump functions
            if (traceType == VTraceType::CHANGE) {  //
                funcp->addStmtsp(
                    new AstCStmt{flp, "if (VL_UNLIKELY(!vlSymsp->__Vm_activity)) return;"});
            }
            // Register function
            AstCStmt* const cstmtp = new AstCStmt{flp};
            m_regFuncp->addStmtsp(cstmtp);
            if (traceType == VTraceType::CONSTANT) {
                cstmtp->add("tracep->addConstCb(");
                cstmtp->add(new AstAddrOfCFunc{flp, funcp});
                cstmtp->add(", " + std::to_string(funcNum) + ", vlSelf);");
            } else if (traceType == VTraceType::FULL) {
                cstmtp->add("tracep->addFullCb(");
                cstmtp->add(new AstAddrOfCFunc{flp, funcp});
                cstmtp->add(", " + std::to_string(funcNum) + ", vlSelf);");
            } else {
                cstmtp->add("tracep->addChgCb(");
                cstmtp->add(new AstAddrOfCFunc{flp, funcp});
                cstmtp->add(", " + std::to_string(funcNum) + ", vlSelf);");
            }
        } else {
            // Sub functions
            funcp->argTypes(bufArg);
            // Setup base references. Note in rare occasions we can end up with an empty trace
            // sub function, hence the VL_ATTR_UNUSED attributes.
            if (traceType != VTraceType::CHANGE) {
                // Full dump sub function
                funcp->addStmtsp(new AstCStmt{flp,  //
                                              "uint32_t* const oldp VL_ATTR_UNUSED = "
                                              "bufp->oldp(vlSymsp->__Vm_baseCode);\n"});
            } else {
                // Change dump sub function
                if (v3Global.opt.useTraceOffload()) {
                    funcp->addStmtsp(new AstCStmt{flp,  //
                                                  "const uint32_t base VL_ATTR_UNUSED = "
                                                  "vlSymsp->__Vm_baseCode + "
                                                      + cvtToStr(baseCode) + ";\n"});
                    funcp->addStmtsp(
                        new AstCStmt{flp, "(void)bufp;  // Prevent unused variable warning\n"});
                } else {
                    funcp->addStmtsp(new AstCStmt{flp,  //
                                                  "uint32_t* const oldp VL_ATTR_UNUSED = "
                                                  "bufp->oldp(vlSymsp->__Vm_baseCode + "
                                                      + cvtToStr(baseCode) + ");\n"});
                }
            }
            // Add call to top function
            AstCCall* const callp = new AstCCall{funcp->fileline(), funcp};
            callp->dtypeSetVoid();
            callp->argTypes("bufp");
            topFuncp->addStmtsp(callp->makeStmt());
        }
        // Done
        UINFO(5, "  newCFunc " << funcp);
        return funcp;
    }

    void createConstTraceFunctions(const TraceVec& traces) {
        const int splitLimit = v3Global.opt.outputSplitCTrace() ? v3Global.opt.outputSplitCTrace()
                                                                : std::numeric_limits<int>::max();

        AstCFunc* const topFuncp = newCFunc(VTraceType::CONSTANT, nullptr, 0);
        uint32_t subFuncNum = 0;
        AstCFunc* subFuncp = nullptr;
        int subStmts = 0;
        for (auto it = traces.cbegin(); it != traces.end(); ++it) {
            const TraceTraceVertex* const vtxp = it->second;
            AstTraceDecl* const declp = vtxp->nodep();
            if (const TraceTraceVertex* const canonVtxp = vtxp->duplicatep()) {
                // This is a duplicate trace node. We will assign the signal
                // number to the canonical node, and emit this as an alias, so
                // no need to create a TraceInc node.
                const AstTraceDecl* const canonDeclp = canonVtxp->nodep();
                UASSERT_OBJ(!canonVtxp->duplicatep(), canonDeclp, "Canonical node is a duplicate");
                UASSERT_OBJ(canonDeclp->code() != 0, canonDeclp,
                            "Canonical node should have code assigned already");
                declp->code(canonDeclp->code());
                continue;
            }

            // This is a canonical trace node. Assign trace code (signal number).
            UASSERT_OBJ(declp->code() == 0, declp,
                        "Canonical node should not have code assigned yet");
            declp->code(m_code);
            const uint32_t codeInc = declp->codeInc();
            m_code += codeInc;
            m_statUniqCodes += codeInc;
            ++m_statUniqSigs;

            // If this is a const signal, add the AstTraceInc
            const ActCodeSet& actSet = it->first;
            if (actSet.count(TraceActivityVertex::ACTIVITY_NEVER)) {
                // Crate new sub function if required
                if (!subFuncp || subStmts > splitLimit) {
                    subStmts = 0;
                    subFuncp = newCFunc(VTraceType::CONSTANT, topFuncp, subFuncNum);
                    ++subFuncNum;
                }
                FileLine* const flp = declp->fileline();
                AstTraceInc* const incp = new AstTraceInc{flp, declp, VTraceType::CONSTANT};
                subFuncp->addStmtsp(incp);
                subStmts += incp->nodeCount();
            }
        }
    }

    void createNonConstTraceFunctions(const TraceVec& traces, uint32_t nAllCodes,
                                      uint32_t parallelism) {
        const int splitLimit = v3Global.opt.outputSplitCTrace() ? v3Global.opt.outputSplitCTrace()
                                                                : std::numeric_limits<int>::max();

        // pre-incremented, so starts at 0
        uint32_t topFuncNum = std::numeric_limits<uint32_t>::max();
        TraceVec::const_iterator it = traces.begin();
        while (it != traces.end()) {
            AstCFunc* topFulFuncp = nullptr;
            AstCFunc* topChgFuncp = nullptr;
            AstCFunc* subFulFuncp = nullptr;
            AstCFunc* subChgFuncp = nullptr;
            uint32_t subFuncNum = 0;
            int subStmts = 0;
            const uint32_t maxCodes = std::max((nAllCodes + parallelism - 1) / parallelism, 1U);
            uint32_t nCodes = 0;
            const ActCodeSet* prevActSet = nullptr;
            AstIf* ifp = nullptr;
            uint32_t baseCode = 0;
            for (; nCodes < maxCodes && it != traces.end(); ++it) {
                const ActCodeSet& actSet = it->first;
                // Traced value never changes, no need to add it
                if (actSet.count(TraceActivityVertex::ACTIVITY_NEVER)) continue;

                const TraceTraceVertex* const vtxp = it->second;
                AstTraceDecl* const declp = vtxp->nodep();

                // This is a duplicate decl, no need to add it, but must set the
                // function index to the same as the canonical node.
                if (const TraceTraceVertex* const canonVtxp = vtxp->duplicatep()) {
                    declp->fidx(canonVtxp->nodep()->fidx());
                    continue;
                }

                // Create top function if not yet created
                if (!topFulFuncp) {
                    ++topFuncNum;
                    topFulFuncp = newCFunc(VTraceType::FULL, nullptr, topFuncNum);
                    topChgFuncp = newCFunc(VTraceType::CHANGE, nullptr, topFuncNum);
                }

                // Create new sub function if required
                if (!subFulFuncp || subStmts > splitLimit) {
                    baseCode = declp->code();
                    subStmts = 0;
                    subFulFuncp = newCFunc(VTraceType::FULL, topFulFuncp, subFuncNum, baseCode);
                    subChgFuncp = newCFunc(VTraceType::CHANGE, topChgFuncp, subFuncNum, baseCode);
                    ++subFuncNum;
                    prevActSet = nullptr;
                    ifp = nullptr;
                }

                // If required, create the conditional node checking the activity flags
                if (!prevActSet || actSet != *prevActSet) {
                    FileLine* const flp = m_topScopep->fileline();
                    const bool always = actSet.count(TraceActivityVertex::ACTIVITY_ALWAYS) != 0;
                    AstNodeExpr* condp = nullptr;
                    if (always) {
                        condp = new AstConst{flp, 1};  // Always true, will be folded later
                    } else {
                        for (const uint32_t actCode : actSet) {
                            AstNodeExpr* const selp = selectActivity(flp, actCode, VAccess::READ);
                            condp = condp ? new AstOr{flp, condp, selp} : selp;
                        }
                    }
                    ifp = new AstIf{flp, condp};
                    if (!always) ifp->branchPred(VBranchPred::BP_UNLIKELY);
                    subChgFuncp->addStmtsp(ifp);
                    subStmts += ifp->nodeCount();
                    prevActSet = &actSet;
                }

                // Add TraceInc nodes
                FileLine* const flp = declp->fileline();
                AstTraceInc* const incFulp = new AstTraceInc{flp, declp, VTraceType::FULL};
                subFulFuncp->addStmtsp(incFulp);
                AstTraceInc* const incChgp
                    = new AstTraceInc{flp, declp, VTraceType::CHANGE, baseCode};
                ifp->addThensp(incChgp);

                // Set the function index of the decl
                declp->fidx(topFuncNum);

                // Track splitting due to size
                UASSERT_OBJ(incFulp->nodeCount() == incChgp->nodeCount(), declp,
                            "Should have equal cost");
                const VNumRange range = declp->arrayRange();
                if (range.ranged()) {
                    // 2x because each element is a TraceInc and a VarRef
                    subStmts += range.elements() * 2;
                } else {
                    subStmts += incChgp->nodeCount();
                }

                // Track partitioning
                nCodes += declp->codeInc();
            }
        }
    }

    void createCleanupFunction() {
        FileLine* const fl = m_topScopep->fileline();
        AstCFunc* const cleanupFuncp = new AstCFunc{fl, "trace_cleanup", m_topScopep};
        cleanupFuncp->argTypes("void* voidSelf, " + v3Global.opt.traceClassBase()
                               + "* /*unused*/");
        cleanupFuncp->isTrace(true);
        cleanupFuncp->slow(false);
        cleanupFuncp->isStatic(true);
        cleanupFuncp->isLoose(true);
        m_topScopep->addBlocksp(cleanupFuncp);
        cleanupFuncp->addStmtsp(new AstCStmt{fl, EmitCUtil::voidSelfAssign(m_topModp)});
        cleanupFuncp->addStmtsp(new AstCStmt{fl, EmitCUtil::symClassAssign()});

        // Register it
        {
            AstCStmt* const cstmtp = new AstCStmt{fl};
            m_regFuncp->addStmtsp(cstmtp);
            cstmtp->add("tracep->addCleanupCb(");
            cstmtp->add(new AstAddrOfCFunc{fl, cleanupFuncp});
            cstmtp->add(", vlSelf);");
        }

        // Clear global activity flag
        cleanupFuncp->addStmtsp(
            new AstCStmt{m_topScopep->fileline(), "vlSymsp->__Vm_activity = false;"s});

        // Clear fine grained activity flags
        for (uint32_t i = 0; i < m_activityNumber; ++i) {
            AstNode* const clrp = new AstAssign{fl, selectActivity(fl, i, VAccess::WRITE),
                                                new AstConst{fl, AstConst::BitFalse{}}};
            cleanupFuncp->addStmtsp(clrp);
        }
    }

    void createTraceFunctions() {
        // Detect and remove duplicate values
        detectDuplicates();
        m_graph.removeRedundantEdgesMax(&V3GraphEdge::followAlwaysTrue);

        // Simplify & optimize the graph
        if (dumpGraphLevel() >= 6) m_graph.dumpDotFilePrefixed("trace_pre");
        graphSimplify(true);
        if (dumpGraphLevel() >= 6) m_graph.dumpDotFilePrefixed("trace_simplified");
        graphOptimize();
        if (dumpGraphLevel() >= 6) m_graph.dumpDotFilePrefixed("trace_optimized");

        // Create the fine grained activity flags
        createActivityFlags();

        // Form a sorted list of the traces we are interested in
        TraceVec traces;  // The sorted traces
        // We will split functions such that each have to dump roughly the same amount of data
        // for this we need to keep tack of the number of codes used by the trace functions.
        uint32_t nNonConstCodes = 0;
        sortTraces(traces, nNonConstCodes);

        // Our keys are now sorted to have same activity number adjacent, then
        // by trace order. (Better would be execution order for cache
        // efficiency....) Last are constants and non-changers, as then the
        // last value vector is more compact

        // Create the trace registration function
        m_regFuncp = new AstCFunc{m_topScopep->fileline(), "trace_register", m_topScopep};
        m_regFuncp->argTypes(v3Global.opt.traceClassBase() + "* tracep");
        m_regFuncp->isTrace(true);
        m_regFuncp->slow(true);
        m_regFuncp->isStatic(false);
        m_regFuncp->isLoose(true);
        m_topScopep->addBlocksp(m_regFuncp);

        // Create the const dump functions. Also allocates trace codes.
        createConstTraceFunctions(traces);

        // Create the full and incremental dump functions
        createNonConstTraceFunctions(traces, nNonConstCodes, m_parallelism);

        // Remove refs to traced values from TraceDecl nodes, these have now moved under
        // TraceInc
        for (const auto& i : traces) {
            AstNode* const valuep = i.second->nodep()->valuep();
            valuep->unlinkFrBack();
            valuep->deleteTree();
        }

        // Create the trace cleanup function clearing the activity flags
        createCleanupFunction();
    }

    TraceCFuncVertex* getCFuncVertexp(AstCFunc* nodep) {
        TraceCFuncVertex* vertexp
            = nodep->user1() ? nodep->user1u().toGraphVertex()->cast<TraceCFuncVertex>() : nullptr;
        if (!vertexp) {
            vertexp = new TraceCFuncVertex{&m_graph, nodep};
            nodep->user1p(vertexp);
        }
        return vertexp;
    }
    TraceActivityVertex* getActivityVertexp(AstNode* nodep, bool slow) {
        TraceActivityVertex* vertexp
            = nodep->user3() ? nodep->user3u().toGraphVertex()->cast<TraceActivityVertex>()
                             : nullptr;
        if (!vertexp) {
            vertexp = new TraceActivityVertex{&m_graph, nodep, slow};
            nodep->user3p(vertexp);
        }
        vertexp->slow(slow);
        return vertexp;
    }

    // VISITORS
    void visit(AstNetlist* nodep) override {
        m_code = 1;  // Multiple TopScopes will require fixing how code#s
        // are assigned as duplicate varscopes must result in the same tracing code#.

        // Add vertexes for all TraceDecl, and edges from VARs each trace looks at
        m_finding = false;
        iterateChildren(nodep);

        // Add vertexes for all CFUNCs, and edges to VARs the func sets
        m_finding = true;
        iterateChildren(nodep);

        // Create the trace functions and insert them into the tree
        createTraceFunctions();
    }
    void visit(AstNodeModule* nodep) override {
        if (nodep->isTop()) m_topModp = nodep;
        iterateChildren(nodep);
    }
    void visit(AstStmtExpr* nodep) override {
        if (!m_finding && !nodep->user2()) {
            if (AstCCall* const callp = VN_CAST(nodep->exprp(), CCall)) {
                UINFO(8, "   CCALL " << callp);
                // See if there are other calls in same statement list;
                // If so, all funcs might share the same activity code
                TraceActivityVertex* const activityVtxp
                    = getActivityVertexp(nodep, callp->funcp()->slow());
                for (AstNode* nextp = nodep; nextp; nextp = nextp->nextp()) {
                    if (AstStmtExpr* const stmtp = VN_CAST(nextp, StmtExpr)) {
                        if (AstCCall* const ccallp = VN_CAST(stmtp->exprp(), CCall)) {
                            stmtp->user2(true);  // Processed
                            UINFO(8, "     SubCCALL " << ccallp);
                            V3GraphVertex* const ccallFuncVtxp = getCFuncVertexp(ccallp->funcp());
                            activityVtxp->slow(ccallp->funcp()->slow());
                            new V3GraphEdge{&m_graph, activityVtxp, ccallFuncVtxp, 1};
                        }
                    }
                }
            }
        }
        iterateChildren(nodep);
    }
    void visit(AstCFunc* nodep) override {
        UINFO(8, "   CFUNC " << nodep);
        V3GraphVertex* const funcVtxp = getCFuncVertexp(nodep);
        if (!m_finding) {  // If public, we need a unique activity code to allow for sets
                           // directly in this func
            if (nodep->funcPublic() || nodep->dpiExportImpl() || nodep == v3Global.rootp()->evalp()
                || nodep->isCoroutine()) {
                // Cannot treat a coroutine as slow, it may be resumed later
                const bool slow = nodep->slow() && !nodep->isCoroutine();
                V3GraphVertex* const activityVtxp = getActivityVertexp(nodep, slow);
                new V3GraphEdge{&m_graph, activityVtxp, funcVtxp, 1};
            }
        }
        VL_RESTORER(m_cfuncp);
        m_cfuncp = nodep;
        iterateChildren(nodep);
    }
    void visit(AstTraceDecl* nodep) override {
        UINFO(8, "   TRACE " << nodep);
        if (!m_finding) {
            V3GraphVertex* const vertexp = new TraceTraceVertex{&m_graph, nodep};
            nodep->user1p(vertexp);

            UASSERT_OBJ(m_cfuncp, nodep, "Trace not under func");
            VL_RESTORER(m_tracep);
            m_tracep = nodep;
            iterateChildren(nodep);
        }
    }
    void visit(AstVarRef* nodep) override {
        if (m_tracep) {
            UASSERT_OBJ(nodep->varScopep(), nodep, "No var scope?");
            UASSERT_OBJ(nodep->access().isReadOnly(), nodep, "Lvalue in trace?  Should be const.");
            V3GraphVertex* varVtxp = nodep->varScopep()->user1u().toGraphVertex();
            if (!varVtxp) {
                varVtxp = new TraceVarVertex{&m_graph, nodep->varScopep()};
                nodep->varScopep()->user1p(varVtxp);
            }
            V3GraphVertex* const traceVtxp = m_tracep->user1u().toGraphVertex();
            new V3GraphEdge{&m_graph, varVtxp, traceVtxp, 1};
            if (nodep->varp()->isPrimaryInish()  // Always need to trace primary inputs
                || nodep->varp()->isSigPublic()) {  // Or ones user can change
                new V3GraphEdge{&m_graph, m_alwaysVtxp, traceVtxp, 1};
            }
        } else if (m_cfuncp && m_finding && nodep->access().isWriteOrRW()) {
            UASSERT_OBJ(nodep->varScopep(), nodep, "No var scope?");
            V3GraphVertex* const funcVtxp = getCFuncVertexp(m_cfuncp);
            V3GraphVertex* const varVtxp = nodep->varScopep()->user1u().toGraphVertex();
            if (varVtxp) {  // else we're not tracing this signal
                new V3GraphEdge{&m_graph, funcVtxp, varVtxp, 1};
            }
        }
    }
    //--------------------
    void visit(AstNode* nodep) override { iterateChildren(nodep); }

public:
    // CONSTRUCTORS
    explicit TraceVisitor(AstNetlist* nodep)
        : m_alwaysVtxp{new TraceActivityVertex{&m_graph, TraceActivityVertex::ACTIVITY_ALWAYS}} {
        iterate(nodep);
    }
    ~TraceVisitor() override {
        V3Stats::addStat("Tracing, Activity setters", m_statSetters);
        V3Stats::addStat("Tracing, Activity slow blocks", m_statSettersSlow);
        V3Stats::addStat("Tracing, Unique trace codes", m_statUniqCodes);
        V3Stats::addStat("Tracing, Unique traced signals", m_statUniqSigs);
    }
};

//######################################################################
// Trace class functions

void V3Trace::traceAll(AstNetlist* nodep) {
    UINFO(2, __FUNCTION__ << ":");
    { TraceVisitor{nodep}; }  // Destruct before checking
    V3Global::dumpCheckGlobalTree("trace", 0, dumpTreeEitherLevel() >= 3);
}