From b06bd46dc9ab1d43fe4523aa4bc634eac21f9db4 Mon Sep 17 00:00:00 2001
From: Artur Bieniek <abieniek@antmicro.com>
Date: Thu, 10 Sep 2026 20:46:54 +0200
Subject: [PATCH] Avoid duplicate lookup in NFA property recursion guard
 (#8321)

Signed-off-by: Artur Bieniek <abieniek@antmicro.com>
---
 src/V3AssertNfa.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/V3AssertNfa.cpp b/src/V3AssertNfa.cpp
index 2bd03e9d4..8c4a07d5d 100644
--- a/src/V3AssertNfa.cpp
+++ b/src/V3AssertNfa.cpp
@@ -2947,11 +2947,10 @@ class AssertNfaVisitor final : public VNVisitor {
         // Recursion guard: IEEE 1800-2023 16.12.1 forbids recursive properties.
         // V3Width emits "Recursive property call" for direct recursion before this
         // pass runs; this catches any nested-inlining cycle that slips past.
-        if (m_inliningProps.count(propyp)) {
+        if (!m_inliningProps.emplace(propyp).second) {
             funcrefp->v3error("Illegal recursive property reference");  // LCOV_EXCL_LINE
             return;  // LCOV_EXCL_LINE
         }
-        m_inliningProps.insert(propyp);
         struct Guard final {
             std::set<const AstProperty*>& setr;
             const AstProperty* keyp;