Some Haifa scheduler bugs

[Bernd Schmidt]

> In general, that's not going to work.
> 
> Basically any machine that defines SMALL_REGISTER_CLASSES and passes args in
> registers is playing with fire -- reload can and will silently generate incorrect
> code for such targets.  For that reason I _highly_ recommend against using
> registers for parameter passing on the x86 targets.

How can reload generate incorrect code in this case except if the lifetime
of a hard register gets extended by the scheduler or some other optimizer?

Bernd