From ffd2c5c69e1c381063589a8bc25b2604a90afa1f Mon Sep 17 00:00:00 2001
From: Geza Lore <glore@tenstorrent.com>
Date: Wed, 15 Apr 2026 13:46:45 +0100
Subject: [PATCH] Optimize temporary insertion in DfgPeephole

---
 src/V3DfgPeephole.cpp | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/V3DfgPeephole.cpp b/src/V3DfgPeephole.cpp
index 62ad31269..b44e648da 100644
--- a/src/V3DfgPeephole.cpp
+++ b/src/V3DfgPeephole.cpp
@@ -208,6 +208,9 @@ class V3DfgPeephole final : public DfgVisitor {
     size_t m_currentGeneration = 0;  // Current generation number
     size_t m_lastId = 0;  // Last unique vertex ID assigned
     size_t m_nTemps = 0;  // Number of temporary variables created
+    // Scope for transient temporariy variables cerated in this pass. They should all be
+    // eliminated wihtin this pass, so anything should be ok, pick the top scope as easy to find.
+    AstScope* const m_tmpScopep = v3Global.rootp()->topScopep()->scopep();
 
     // STATIC STATE
     static V3DebugBisect s_debugBisect;  // Debug aid
@@ -1847,10 +1850,9 @@ class V3DfgPeephole final : public DfgVisitor {
                     DfgSplicePacked* const sp = new DfgSplicePacked{m_dfg, flp, vtxp->dtype()};
                     m_vInfo[sp].m_id = ++m_lastId;
                     sp->addDriver(catp, lsb, flp);
-                    DfgVertex::ScopeCache scopeCache;
-                    AstScope* const scopep = vtxp->scopep(scopeCache, true);
                     const std::string name = m_dfg.makeUniqueName("PeepholeNarrow", m_nTemps++);
-                    DfgVertexVar* const varp = m_dfg.makeNewVar(flp, name, vtxp->dtype(), scopep);
+                    DfgVertexVar* const varp
+                        = m_dfg.makeNewVar(flp, name, vtxp->dtype(), m_tmpScopep);
                     varp->tmpForp(varp->vscp());
                     m_vInfo[varp].m_id = ++m_lastId;
                     varp->vscp()->varp()->isInternal(true);