Redundant logical operations left after early splitting

[Paolo Bonzini]

> What's important here is that reg1 is being set multiple times.  You'd
> be better off if you can twiddle the splitters to avoid this behavior.
> If you need a new pseudo, then get one :-)

I agree with this, but...

> Once you do that, local would propagate these things better.  That
> still leaves the simplification & nop problem, but I'm pretty sure
> that can be trivially fixed within local without resorting to running
> another forwprop pass after splitting.

I want to try *moving* forwprop, not add another pass.  Also, fwprop 
could in principle subsume local const/copyprop; it doesn't right now 
because I didn't want to compute def-use chains, but it could be changed 
in the future.

Paolo