(In reply to David Heidelberger (okias) from comment #4)
> > > Also, problematic swizzle can be seen on instruction 27: in diff wx -> wz.
> > 
> > .wz is a legal swizzle according to the native_swizzles table.  Can you add
> > printfs to lookup_native_swizzle to see why it is not being treated as a
> > legal swizzle?
> 
> I made printf in lookup_native_swizzle originally.
> I probably messed this. It's wz -> wx. (it fails for www after 1. w, same
> for wzy, also fails after 1. w).

What is the value of sd  is returned when the swizzle .wx is passed to
lookup_native_swizzle?