From c878a7e73523154a4f7da52bde9633d05b715c56 Mon Sep 17 00:00:00 2001
From: Geza Lore <glore@tenstorrent.com>
Date: Wed, 3 Jun 2026 11:24:30 +0100
Subject: [PATCH] Optimize VL_ONEHOT

Equivalent to `__builtin_popcount(_) == 1` and a few instructions
shorter.
---
 include/verilated_funcs.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/verilated_funcs.h b/include/verilated_funcs.h
index 5a1e2b442..db4c39e5c 100644
--- a/include/verilated_funcs.h
+++ b/include/verilated_funcs.h
@@ -803,10 +803,12 @@ static inline IData VL_COUNTBITS_W(int lbits, int words, WDataInP const lwp, IDa
 }
 
 static inline IData VL_ONEHOT_I(IData lhs) VL_PURE {
-    return (((lhs & (lhs - 1)) == 0) & (lhs != 0));
+    const IData y = lhs - 1;
+    return y < (lhs ^ y);
 }
 static inline IData VL_ONEHOT_Q(QData lhs) VL_PURE {
-    return (((lhs & (lhs - 1)) == 0) & (lhs != 0));
+    const QData y = lhs - 1;
+    return y < (lhs ^ y);
 }
 static inline IData VL_ONEHOT_W(int words, WDataInP const lwp) VL_PURE {
     EData one = 0;