Fix cell scoping performance (#6059).

Changes

@@ -17,6 +17,7 @@ Verilator 5.041 devel
 * Improve automatic selection of logic for DFG synthesis (#6370). [Geza Lore]
 * Improve `covergroup with function sample` handling  (#6387). [Jakub Wasilewski]
 * Optimize dead functions without references (#6380). [Artur Bieniek, Antmicro Ltd.]
+* Fix cell scoping performance (#6059). [Jerry Tianchen]
 * Fix while loop hang on timing-delayed assignment (#6343) (#6354). [Krzysztof Bieganski, Antmicro Ltd.]
 * Fix driver analysis of partially assigned variables (#6364) (#6378). [Geza Lore]
 * Fix V3Hash MacOS ambiguity (#6350). [Lan Zongwei]

docs/spelling.txt

@@ -428,6 +428,7 @@ Terpstra
 Thiede
 Thierry
 Thyer
+Tianchen
 Tianrui
 Tichelaar
 Timi

src/V3Scope.cpp

@@ -115,9 +115,14 @@ class ScopeVisitor final : public VNVisitor {
             nodep, scopename, m_aboveScopep, m_aboveCellp};
         if (VN_IS(nodep, Package)) m_packageScopes.emplace(nodep, m_scopep);
 
-        // Now for each child cell, iterate the module this cell points to
+        // Get list of cells before we edit, to avoid excess visits (issue #6059)
+        std::deque<AstCell*> cells;
         for (AstNode* cellnextp = nodep->stmtsp(); cellnextp; cellnextp = cellnextp->nextp()) {
-            if (AstCell* const cellp = VN_CAST(cellnextp, Cell)) {
+            if (AstCell* const cellp = VN_CAST(cellnextp, Cell)) cells.push_back(cellp);
+        }
+
+        // Now for each child cell, iterate the module this cell points to
+        for (AstCell* const cellp : cells) {
             VL_RESTORER(m_scopep);  // Protects m_scopep set in called module
             // which is "above" in this code, but later in code execution order
             VL_RESTORER(m_aboveCellp);
@@ -134,7 +139,6 @@ class ScopeVisitor final : public VNVisitor {
                 }
             }
         }
-        }
 
         // Create scope for the current usage of this module
         UINFO(4, " back AT " << scopename << "  " << nodep);