On Fri, Feb 09, 2018 at 08:11:44AM -0600, Segher Boessenkool wrote:
> On Fri, Feb 09, 2018 at 04:12:47PM +1030, Alan Modra wrote:
> >  ;; Use r0 to stop regrename twiddling with lr restore insns emitted
> >  ;; after the call to __morestack.
> >  (define_insn "split_stack_return"
> > -  [(unspec_volatile [(use (reg:SI 0))] UNSPECV_SPLIT_STACK_RETURN)]
> > +  [(unspec_volatile [(use (reg:SI 0)) (use (reg:SI LR_REGNO))]
> > +               UNSPECV_SPLIT_STACK_RETURN)]
> I'm not sure what a USE as input of an UNSPEC means -- it should work
> without the USEs?

Hmm, yes, plain [(reg:SI 0) (reg:SI LR_REGNO)] ought to work.  A sniff
test says it's OK but I'll do the whole bootstrap/regtest cycle before
committing.  I'm not sure why I put the USE there for r0, probably
because I had the r0 dependency outside the unspec initially then
decided it could replace (const_int 0) inside the unspec vector to
save on useless RTL.  I didn't go far enough in trimming the RTL..

Alan Modra
Australia Development Lab, IBM

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