Make AstTopScope accessible from AstNetlist

AstTopScope is a singleton node and making it accessible without a
traversal simplifies some code and decouple some other.

src/V3ActiveTop.cpp

@@ -45,19 +45,12 @@ private:
     AstUser1InUse m_inuser1;
 
     // STATE
-    AstTopScope* m_topscopep = nullptr;  // Top scope for adding sentrees under
-    SenTreeFinder m_finder;  // Find global sentree's and add them
+    SenTreeFinder m_finder;  // Find global sentree's / add them under the AstTopScope
 
     // METHODS
     VL_DEBUG_FUNC;  // Declare debug()
 
     // VISITORS
-    virtual void visit(AstTopScope* nodep) override {
-        m_topscopep = nodep;
-        m_finder.init(m_topscopep);
-        iterateChildren(nodep);
-        m_topscopep = nullptr;
-    }
     virtual void visit(AstNodeModule* nodep) override {
         // Create required actives and add to module
         // We can start ordering at a module, or a scope

src/V3AstNodes.h

@@ -2333,19 +2333,22 @@ public:
 };
 
 class AstTopScope final : public AstNode {
-    // In the top level netlist, a complete scope tree
-    // There may be two of these, when we support "rare" and "usual" splitting
-    // Parents: topMODULE
-    // Children: SCOPEs
-public:
+    // A singleton, held under the top level AstModule. Holds the top level AstScope,
+    // and after V3ActiveTop, the global list of AstSenTrees (list of unique sensitivity lists).
+    // Parent: Top level AstModule
+    // Children: AstSenTree, AstScope
+    friend class AstNetlist;  // Only the AstNetlist can create one
     AstTopScope(FileLine* fl, AstScope* ascopep)
         : ASTGEN_SUPER_TopScope(fl) {
-        addNOp2p(ascopep);
+        addOp2p(ascopep);
     }
+
+public:
     ASTNODE_NODE_FUNCS(TopScope)
-    AstNode* stmtsp() const { return op1p(); }
-    void addStmtsp(AstNode* nodep) { addOp1p(nodep); }
-    AstScope* scopep() const { return VN_AS(op2p(), Scope); }  // op1 = AstVarScope's
+    virtual bool maybePointedTo() const override { return true; }
+    AstSenTree* senTreesp() const { return VN_AS(op1p(), SenTree); }
+    void addSenTreep(AstSenTree* nodep) { addOp1p((AstNode*)nodep); }
+    AstScope* scopep() const { return VN_AS(op2p(), Scope); }
 };
 
 class AstVarScope final : public AstNode {
@@ -9191,6 +9194,7 @@ private:
     AstCFunc* m_evalp = nullptr;  // The '_eval' function
     AstExecGraph* m_execGraphp = nullptr;  // Execution MTask graph for threads>1 mode
     AstVarScope* m_dpiExportTriggerp = nullptr;  // The DPI export trigger variable
+    AstTopScope* m_topScopep = nullptr;  // The singleton AstTopScope under the top module
     VTimescale m_timeunit;  // Global time unit
     VTimescale m_timeprecision;  // Global time precision
     bool m_changeRequest = false;  // Have _change_request method
@@ -9202,6 +9206,7 @@ public:
         BROKEN_RTN(m_dollarUnitPkgp && !m_dollarUnitPkgp->brokeExists());
         BROKEN_RTN(m_evalp && !m_evalp->brokeExists());
         BROKEN_RTN(m_dpiExportTriggerp && !m_dpiExportTriggerp->brokeExists());
+        BROKEN_RTN(m_topScopep && !m_topScopep->brokeExists());
         return nullptr;
     }
     virtual string name() const override { return "$root"; }
@@ -9239,6 +9244,13 @@ public:
     void execGraphp(AstExecGraph* graphp) { m_execGraphp = graphp; }
     AstVarScope* dpiExportTriggerp() const { return m_dpiExportTriggerp; }
     void dpiExportTriggerp(AstVarScope* varScopep) { m_dpiExportTriggerp = varScopep; }
+    AstTopScope* topScopep() const { return m_topScopep; }
+    void createTopScope(AstScope* scopep) {
+        UASSERT(scopep, "Must not be nullptr");
+        UASSERT_OBJ(!m_topScopep, scopep, "TopScope already exits");
+        m_topScopep = new AstTopScope{scopep->modp()->fileline(), scopep};
+        scopep->modp()->addStmtp(v3Global.rootp()->topScopep());
+    }
     VTimescale timeunit() const { return m_timeunit; }
     void timeunit(const VTimescale& value) { m_timeunit = value; }
     VTimescale timeprecision() const { return m_timeprecision; }

src/V3GenClk.cpp

@@ -49,7 +49,7 @@ private:
     // STATE
     AstActive* m_activep = nullptr;  // Inside activate statement
     AstNodeModule* m_topModp;  // Top module
-    AstScope* m_scopetopp = nullptr;  // Scope under TOPSCOPE
+    AstScope* const m_scopetopp = v3Global.rootp()->topScopep()->scopep();  // The top AstScope
 
     // METHODS
     AstVarScope* genInpClk(AstVarScope* vscp) {
@@ -93,11 +93,6 @@ private:
     // VISITORS
     virtual void visit(AstTopScope* nodep) override {
         AstNode::user2ClearTree();  // user2p() used on entire tree
-
-        AstScope* scopep = nodep->scopep();
-        UASSERT_OBJ(scopep, nodep, "No scope found on top level");
-        m_scopetopp = scopep;
-
         iterateChildren(nodep);
     }
     //----

src/V3Order.cpp

@@ -941,8 +941,6 @@ private:
         m_activep = nullptr;
         m_topScopep = nodep;
         m_scopetopp = nodep->scopep();
-        // Find global SenTrees
-        m_finder.init(m_topScopep);
         // ProcessDomainsIterate will use these when it needs to move
         // something to a combodomain.  This saves a ton of find() operations.
         AstSenTree* combp

src/V3Scope.cpp

@@ -132,8 +132,7 @@ private:
         AstNode::user1ClearTree();
         m_modp = nodep;
         if (m_modp->isTop()) {
-            AstTopScope* topscp = new AstTopScope(nodep->fileline(), m_scopep);
-            m_modp->addStmtp(topscp);
+            v3Global.rootp()->createTopScope(m_scopep);
         } else {
             m_modp->addStmtp(m_scopep);
         }

src/V3SenTree.h

@@ -74,14 +74,21 @@ private:
 class SenTreeFinder final {
 private:
     // STATE
-    AstTopScope* m_topScopep = nullptr;  // Top scope to add global SenTrees to
+    AstTopScope* const m_topScopep;  // Top scope to add global SenTrees to
     SenTreeSet m_trees;  // Set of global SenTrees
 
     VL_UNCOPYABLE(SenTreeFinder);
 
 public:
     // CONSTRUCTORS
-    SenTreeFinder() = default;
+    SenTreeFinder()
+        : m_topScopep{v3Global.rootp()->topScopep()} {
+        // Gather existing global SenTrees
+        for (AstSenTree* nodep = m_topScopep->senTreesp(); nodep;
+             nodep = VN_AS(nodep->nextp(), SenTree)) {
+            m_trees.add(nodep);
+        }
+    }
 
     // METHODS
     AstSenTree* getSenTree(AstSenTree* senTreep) {
@@ -90,23 +97,13 @@ public:
         AstSenTree* treep = m_trees.find(senTreep);
         // Not found, form a new one
         if (!treep) {
-            UASSERT(m_topScopep, "Never called init()");
             treep = senTreep->cloneTree(false);
-            m_topScopep->addStmtsp(treep);
+            m_topScopep->addSenTreep(treep);
             UINFO(8, "    New SENTREE " << treep << endl);
             m_trees.add(treep);
         }
         return treep;
     }
-
-    void init(AstTopScope* topScopep) {
-        // Keep hold of top scope so we can add global SenTrees later
-        m_topScopep = topScopep;
-        // Gather existing global SenTrees
-        for (AstNode* nodep = topScopep->stmtsp(); nodep; nodep = nodep->nextp()) {
-            if (AstSenTree* senTreep = VN_CAST(nodep, SenTree)) m_trees.add(senTreep);
-        }
-    }
 };
 
 #endif  // Guard

src/V3Task.cpp

@@ -423,7 +423,7 @@ private:
     // STATE
     TaskStateVisitor* m_statep;  // Common state between visitors
     AstNodeModule* m_modp = nullptr;  // Current module
-    AstTopScope* m_topScopep = nullptr;  // Current top scope
+    AstTopScope* const m_topScopep = v3Global.rootp()->topScopep();  // The AstTopScope
     AstScope* m_scopep = nullptr;  // Current scope
     InsertMode m_insMode = IM_BEFORE;  // How to insert
     AstNode* m_insStmtp = nullptr;  // Where to insert statement
@@ -1392,10 +1392,6 @@ private:
             iterateChildren(nodep);
         }
     }
-    virtual void visit(AstTopScope* nodep) override {
-        m_topScopep = nodep;
-        iterateChildren(nodep);
-    }
     virtual void visit(AstScope* nodep) override {
         m_scopep = nodep;
         m_insStmtp = nullptr;

src/V3Trace.cpp

@@ -169,7 +169,7 @@ private:
 
     // STATE
     AstNodeModule* m_topModp = nullptr;  // Module to add variables to
-    AstScope* m_topScopep = nullptr;  // Scope 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
     AstTraceDecl* m_tracep = nullptr;  // Trace function adding to graph
@@ -808,12 +808,6 @@ private:
         if (nodep->isTop()) m_topModp = nodep;
         iterateChildren(nodep);
     }
-    virtual void visit(AstTopScope* nodep) override {
-        AstScope* const scopep = nodep->scopep();
-        UASSERT_OBJ(scopep, nodep, "No scope found on top level");
-        m_topScopep = scopep;
-        iterateChildren(nodep);
-    }
     virtual void visit(AstCCall* nodep) override {
         UINFO(8, "   CCALL " << nodep << endl);
         if (!m_finding && !nodep->user2()) {

src/V3TraceDecl.cpp

@@ -37,7 +37,7 @@ private:
     // NODE STATE
 
     // STATE
-    AstScope* m_topScopep = nullptr;  // Current top scope
+    AstScope* const m_topScopep = v3Global.rootp()->topScopep()->scopep();  // The top AstScope
     AstCFunc* m_initFuncp = nullptr;  // Trace function being built
     AstCFunc* m_initSubFuncp = nullptr;  // Trace function being built (under m_init)
     int m_initSubStmts = 0;  // Number of statements in function
@@ -136,7 +136,6 @@ private:
 
     // VISITORS
     virtual void visit(AstTopScope* nodep) override {
-        m_topScopep = nodep->scopep();
         // Create the trace init function
         m_initFuncp = newCFunc("trace_init_top");
         // Create initial sub function