Add issue reference to MSVC workaround comment
@@ -432,6 +432,7 @@ static ASTCENC_SIMD_INLINE vint4 unorm16_to_sf16(vint4 p)
vmask4 is_small = p < vint4(4);
// Manually inline clz() on Visual Studio to avoid release build codegen bug
+ // see https://github.com/ARM-software/astc-encoder/issues/259
#if !defined(__clang__) && defined(_MSC_VER)
vint4 a = (~lsr<8>(p)) & p;
a = float_as_int(int_to_float(a));
