From 24b75b65db1ed4f9591f16f9726ebc0f55b158f1 Mon Sep 17 00:00:00 2001
From: Akash Levy <akash@silimate.com>
Date: Tue, 2 Jun 2026 01:18:29 -0700
Subject: [PATCH] Fix UB issue

---
 passes/silimate/opt_compact_prefix.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/passes/silimate/opt_compact_prefix.cc b/passes/silimate/opt_compact_prefix.cc
index 8ae16d639..e9b82f18b 100644
--- a/passes/silimate/opt_compact_prefix.cc
+++ b/passes/silimate/opt_compact_prefix.cc
@@ -79,8 +79,9 @@ struct OptCompactPrefixWorker
 		sig = sigmap(sig);
 		if (!sig.is_fully_const())
 			return false;
+		uint64_t uvalue = (uint64_t)value;
 		for (int i = 0; i < GetSize(sig); i++) {
-			bool want = ((uint64_t)value >> i) & 1;
+			bool want = (i < 64) ? ((uvalue >> i) & 1) : (value < 0);
 			if (sig[i] != (want ? State::S1 : State::S0))
 				return false;
 		}