Thanks to all for the replies. I had clearly forgotten what MVHI did (OK, I probably never knew-too many new instructions!).
As I said, it's not a problem, but I'm a bit bothered by your comment, Peter: > So this is not a curious "optimization". It is a natural non-optimization. Seems like the unoptimized code is oddly crude. I suppose compiler authors must fight the urge to do some basic optimization, but why would it ever be this bad? I do like the pseudo-assembler, putting as much info as possible in. It just threw me since I was first wondering "Is there some new assembler syntax I've missed??" ...phsiii (who is now having flashbacks to almost 40 years ago, dealing with FORTHX optimization that was optimizing the index increment out of loops.)
