Re: Recent change to mips_output_move

[Richard Sandiford <rsandifo at redhat dot com>]

Eric Christopher <echristo@redhat.com> writes:
> > As I understand it, .set nomacro only warns about multi-instruction
> > macros, not single-instruction ones.  We've been using move, li and
> > dli in delay slots for a long time.
> 
> Pretty sure I was getting a warning about move. I'll double check later
> though.

Thanks.

> > In case it's any reassurance: for the last few months, I've been
> > testing with a version of gas in which all .set nomacro warnings
> > are hard errors.  I haven't seen it cause any problems.
> > 
> > > (Really should commit move_register to using or though...)
> > 
> > Why's that?
> 
> So that we're not getting unexpected sign extends on some platforms and
> not on others (bcm1250). This way, we're just moving a value, nothing
> more.

Could you be more specific about when this makes a difference?
I.e. in what cases are we using a 32-bit move on a GPR that isn't
properly sign-extended?  In what cases is it valid to do that?

Richard