Fix V3InstrCount with recursive functions (#8361)

Fixes #8327

src/V3InstrCount.cpp

@@ -20,6 +20,7 @@
 #include "V3InstrCount.h"
 
 #include <iomanip>
+#include <unordered_map>
 
 VL_DEFINE_DEBUG_FUNCTIONS;
 
@@ -43,6 +44,7 @@ class InstrCountVisitor final : public VNVisitorConst {
     bool m_ignoreRemaining = false;  // Ignore remaining statements in the block
     const bool m_assertNoDups;  // Check for duplicates
     const std::ostream* const m_osp;  // Dump file
+    std::unordered_map<const AstCFunc*, uint32_t> m_funcCosts;  // Cost of each function
 
     // TYPES
     // Little class to cleanly call startVisitBase/endVisitBase
@@ -255,9 +257,15 @@ private:
         if (m_ignoreRemaining) return;
         const VisitBase vb{this, nodep};
         iterateChildrenConst(nodep);
-        m_tracingCall = true;
-        iterateConst(nodep->funcp());
-        UASSERT_OBJ(!m_tracingCall, nodep, "visit(AstCFunc) should have cleared m_tracingCall.");
+        const auto it = m_funcCosts.find(nodep->funcp());
+        if (it == m_funcCosts.end()) {
+            m_tracingCall = true;
+            iterateConst(nodep->funcp());
+            UASSERT_OBJ(!m_tracingCall, nodep,
+                        "visit(AstCFunc) should have cleared m_tracingCall.");
+        } else {
+            m_instrCount += it->second;  // This guards and adds zero cost on recursive calls
+        }
     }
     void visit(AstCFunc* nodep) override {
         // Don't count a CFunc other than by tracing a call or counting it
@@ -265,13 +273,22 @@ private:
         UASSERT_OBJ(m_tracingCall || nodep == m_startNodep, nodep,
                     "AstCFunc not under AstCCall, or not start node");
         UASSERT_OBJ(!m_ignoreRemaining, nodep, "Should not be ignoring at the start of a CFunc");
+        const auto emplacePair = m_funcCosts.emplace(nodep, 0);
+        UASSERT_OBJ(emplacePair.second, nodep, "Should visit every CFunc at most once");
+        uint32_t& funcCostr = emplacePair.first->second;
         m_tracingCall = false;
-        VL_RESTORER(m_inCFunc);
+
+        const uint32_t savedCount = m_instrCount;
+        reset();
         {
+            VL_RESTORER(m_inCFunc);
             m_inCFunc = true;
             const VisitBase vb{this, nodep};
             iterateChildrenConst(nodep);
         }
+        funcCostr = m_instrCount;
+        m_instrCount += savedCount;
+
         m_ignoreRemaining = false;
     }
     void visit(AstNode* nodep) override {

test_regress/t/t_uvm_hello_all_v2020_3_1_dpi.py

@@ -23,6 +23,7 @@ test.compile(v_flags2=[
     "--vpi",
     "--CFLAGS -O0",
     "-Wall",
+    "--stats",
     "+incdir+t/uvm",  #
     "t/uvm/uvm_pkg_all_v2020_3_1_dpi.svh",
     test.pli_filename