From d7cb6981b55a15eee3d0d9be84446826a65c0403 Mon Sep 17 00:00:00 2001
From: Merry <git@mary.rs>
Date: Wed, 13 Dec 2023 12:15:12 +0000
Subject: [PATCH] cxxrtl: Fix value::ctlz

---
 backends/cxxrtl/runtime/cxxrtl/cxxrtl.h | 3 ++-
 tests/cxxrtl/test_value.cc              | 8 +++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
index c9ddb815f..d861b7e07 100644
--- a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
@@ -511,7 +511,8 @@ struct value : public expr_base<value<Bits>> {
 		for (size_t n = 0; n < chunks; n++) {
 			chunk::type x = data[chunks - 1 - n];
 			// First add to `count` as if the chunk is zero
-			count += (n == 0 ? Bits % chunk::bits : chunk::bits);
+			constexpr size_t msb_chunk_bits = Bits % chunk::bits != 0 ? Bits % chunk::bits : chunk::bits;
+			count += (n == 0 ? msb_chunk_bits : chunk::bits);
 			// If the chunk isn't zero, correct the `count` value and return
 			if (x != 0) {
 				for (; x != 0; count--)
diff --git a/tests/cxxrtl/test_value.cc b/tests/cxxrtl/test_value.cc
index c553f6112..4d68372bb 100644
--- a/tests/cxxrtl/test_value.cc
+++ b/tests/cxxrtl/test_value.cc
@@ -36,4 +36,10 @@ int main()
         cxxrtl::value<64> c = a.sshr(b);
         assert(c.get<uint64_t>() == 0xffffffff8abcdef1u);
     }
-}
\ No newline at end of file
+
+    {
+        // ctlz should work with Bits that are a multiple of chunk size
+        cxxrtl::value<32> a(0x00040000u);
+        assert(a.ctlz() == 13);
+    }
+}