From 33a22b5cd135b55b9e4d0f195832282be542e4b2 Mon Sep 17 00:00:00 2001
From: George Rennie <georgerennie@gmail.com>
Date: Mon, 26 May 2025 15:28:14 +0100
Subject: [PATCH] kernel: fix convertible_to_int for overflowing unsigned
 values

---
 kernel/rtlil.cc | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index c08e78dce..021aff73b 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -383,7 +383,23 @@ int RTLIL::Const::as_int(bool is_signed) const
 bool RTLIL::Const::convertible_to_int(bool is_signed) const
 {
 	auto size = get_min_size(is_signed);
-	return (size > 0 && size <= 32);
+
+	if (size <= 0)
+		return false;
+
+	// If it fits in 31 bits it is definitely convertible
+	if (size <= 31)
+		return true;
+
+	// If it fits in 32 bits, it is convertible if signed or if unsigned and the
+	// leading bit is not 1
+	if (size == 32) {
+		if (is_signed)
+			return true;
+		return get_bits().at(31) != State::S1;
+	}
+
+	return false;
 }
 
 std::optional<int> RTLIL::Const::try_as_int(bool is_signed) const