Re: Is there a way to use define_subst when operands need to change modes?

[Kyrill Tkachov <kyrylo dot tkachov at arm dot com>]

On 02/03/15 17:38, Ilya Tocar wrote:
> On 02 Mar 15:22, Kyrill Tkachov wrote:
> > Hi all,
> >
> > I'm looking at using the define_subst machinery to auto-generate
> > zero-extended
> > versions of some patterns, for example having:
> > (set reg:SI
> >       (xor:SI a:SI b:SI))
> >
> > generate a pattern of the form:
> > (set reg:DI
> >       (zero_extend:DI
> >         (xor:SI (a:SI b:SI))))
> >
> > How do I go about achieving this? From the documentation, I think I need
> > something like:
> >       (define_subst "add_z_extend"
> >         [(set (match_operand:SI 0 "" "")
> >               (match_operand:SI 1 "" ""))]
> >         ""
> >         [(set (match_dup 0)
> >               (zero_extend:DI (match_dup 1)))]
> >
> > but in the resultant pattern I need operand 0 to be tranfsormed into DImode.
> > Is there a way to write that?
> Can't you just use  [(set (match_operand:DI 0 "" "")...  instead of
> match_dup?

So, something like:

     (define_subst "add_z_extend"
       [(set (match_operand:SI 0 "" "")
             (match_operand:SI 1 "" ""))]
       ""
       [(set (match_operand:DI 0 "" "")
             (zero_extend:DI (match_dup 1)))]


?


Are we allowed to match an operand twice?