On Tue, Dec 17, 2019 at 05:35:24PM -0600, Segher Boessenkool wrote:
> On Tue, Dec 17, 2019 at 05:29:44PM -0500, Michael Meissner wrote:
> > On Tue, Dec 17, 2019 at 11:15:29AM -0600, Segher Boessenkool wrote:
> > > > +;; Return true if the operand is a valid memory address that does not
> > > > use a
> > > > +;; prefixed address.
> > > > +(define_predicate "non_prefixed_memory"
> > > > + (match_code "mem")
> > > > +{
> > > > + enum insn_form iform
> > > > + = address_to_insn_form (XEXP (op, 0), mode, NON_PREFIXED_DEFAULT);
> > > > +
> > > > + return (iform != INSN_FORM_BAD
> > > > + && iform != INSN_FORM_PREFIXED_NUMERIC
> > > > + && iform != INSN_FORM_PCREL_LOCAL
> > > > + && iform != INSN_FORM_PCREL_EXTERNAL);
> > > > +})
> > >
> > > Why can this not use just !address_is_prefixed? Why is an
> > > INSN_FORM_PCREL_EXTERNAL address neither prefixed nor non-prefixed? What
> > > does "BAD" mean, really? Should that ever happen, should that not ICE?
> >
> > You can't just invert !address_is_prefixed, because it would all things that
> > may not be valid memory addresses.
>
> Yes, so test that *explicitly*, in the "prefixed_memory" predicate as
> well please. Make the two predicates as much the same as possible.
>
> And what is with the INSN_FORM_PCREL_EXTERNAL?
INSN_FORM_PCREL_EXTERNAL says that the operand is a reference to an external
symbol. It cannot appear in an actual memory insns in normal usage, but it
needs to be handled several places:
1) pcrel_extern_addr needs to be able to load an external address into a GPR
register.
2) The prefixed insn attribute (and prefixed_paddi_p which it calls) needs to
recognize pcrel_extern_addr and note that it is prefixed.
3) The PCREL_OPT support will need to support it. If you do the PCREL_OPT
support via combine and flow control passes, you will need to be able to handle
external references as addresses.
The function address_is_prefixed, specifically does not return true for
external symbols, because you can't use them in a normal context.
In the context of the patch (vector extract), it needs to decide whether the
address is prefixed or not, in order to decide whether it needs a second base
register temporary.
--
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meiss...@linux.ibm.com, phone: +1 (978) 899-4797
