From 7f945bf89ed3d108340cee56e0318a2c43a1ae98 Mon Sep 17 00:00:00 2001
From: Geza Lore <gezalore@gmail.com>
Date: Wed, 10 Sep 2025 11:45:08 +0100
Subject: [PATCH] Optimize constant folding in wide expression expansion
 (#6381)

Do not apply V3Const in V3Expand after a function if nothing was
expanded in it.

Also fix statistics counter while at it.

Inspired by #6379, follow up from #6111
---
 src/V3Expand.cpp | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/V3Expand.cpp b/src/V3Expand.cpp
index fe522db32..374ecfdc9 100644
--- a/src/V3Expand.cpp
+++ b/src/V3Expand.cpp
@@ -95,8 +95,8 @@ class ExpandVisitor final : public VNVisitor {
 
     bool doExpandWide(AstNode* nodep) {
         if (isImpure(nodep)) return false;
-        ++m_statWides;
         if (nodep->widthWords() <= v3Global.opt.expandLimit()) {
+            ++m_statWides;
             m_statWideWords += nodep->widthWords();
             return true;
         } else {
@@ -393,10 +393,11 @@ class ExpandVisitor final : public VNVisitor {
         VL_RESTORER(m_nTmps);
         m_funcp = nodep;
         m_nTmps = 0;
+        const VDouble0 statWidesBefore = m_statWides;
         iterateChildren(nodep);
 
-        // Constant fold here, as Ast size can likely be reduced
-        if (v3Global.opt.fConstEager()) {
+        // Constant fold here if anything was expanded, as Ast size can likely be reduced
+        if (v3Global.opt.fConstEager() && m_statWides != statWidesBefore) {
             AstNode* const editedp = V3Const::constifyEditCpp(nodep);
             UASSERT_OBJ(editedp == nodep, editedp, "Should not have replaced CFunc");
         }