Internals: Use faster VNVisitorConst where able. No functional change intended.

src/V3HierBlock.cpp

@@ -236,7 +236,7 @@ string V3HierBlock::commandArgsFileName(bool forCMake) const {
 
 //######################################################################
 // Collect how hierarchical blocks are used
-class HierBlockUsageCollectVisitor final : public VNVisitor {
+class HierBlockUsageCollectVisitor final : public VNVisitorConst {
     // NODE STATE
     // AstNode::user1()            -> bool. Processed
     const VNUser1InUse m_inuser1;
@@ -266,7 +266,7 @@ class HierBlockUsageCollectVisitor final : public VNVisitor {
         }
         prevGParams.swap(m_gparams);
 
-        iterateChildren(nodep);
+        iterateChildrenConst(nodep);
 
         if (nodep->hierBlock()) {
             m_planp->add(nodep, m_gparams);
@@ -280,7 +280,7 @@ class HierBlockUsageCollectVisitor final : public VNVisitor {
         // Visit used module here to know that the module is hier_block or not.
         // This visitor behaves almost depth first search
         if (AstModule* const modp = VN_CAST(nodep->modp(), Module)) {
-            iterate(modp);
+            iterateConst(modp);
             m_referred.insert(modp);
         }
         // Nothing to do for interface because hierarchical block does not exist
@@ -294,12 +294,12 @@ class HierBlockUsageCollectVisitor final : public VNVisitor {
     }
 
     void visit(AstNodeExpr*) override {}  // Accelerate
-    void visit(AstNode* nodep) override { iterateChildren(nodep); }
+    void visit(AstNode* nodep) override { iterateChildrenConst(nodep); }
 
 public:
     HierBlockUsageCollectVisitor(V3HierBlockPlan* planp, AstNetlist* netlist)
         : m_planp{planp} {
-        iterateChildren(netlist);
+        iterateChildrenConst(netlist);
     }
 };