Re: pattern problem with register assignment

[Christian Grössler <chris at groessler dot org>]

On 24.02.11 15:38, Jean-Marc Saffroy wrote:
> On 02/23/2011 09:52 PM, Christian Grössler wrote:
> > Hello,
> >
> > I have a problem with register allocation. Our architecture has some
> > pointer registers "pX" (24bit)
> > and some data registers "dX" (32bit). Since pointers are only 24bit,
> > we're using PSImode for them.
> >
> > There are restrictions in the "add" opcode, we can do
> >
> > pX = add(pX,<imm>)
> > pX = add(pX,dX)
> > pX = add(dX,pX)
> > dX = add(pX,pX)
> > dX = add(pX,<imm>)
> > dX = add(dX,dX)
> > dX = add(dX,<imm>)
> > dX = add(pX,dX)
> > dX = add(dX,pX)
> >
> > pX is allowed in at most 2 of the registers involved, but not in all 3
> > of them.
> > The pattern to add 2 PSImode values looks like this:
> >
> > (define_insn "*addpsi3"
> >    [(set (match_operand:PSI 0 "p_d_operand"
> > "=a,d0d3,?d0d9 m,?d0d9 m")
> >          (plus:PSI (match_operand:PSI 1 "p_d_general_operand"
> > "%a,d0d3,d0d9 a m,d0d9 a i")
> >            (match_operand:PSI 2 "p_d_general_operand" "i d0d9 m,d0d3 m
> > i,d0d9 i a,d0d9 a m")))]
> >    ""
> >    "%0=add(%1,%2)"
> > )
> >
> > It worked fine in the gcc version from 2 years ago, but I'm updating the
> > port to current gcc, and
> > I get a testsuite failure (one of many :-)) in
> > gcc.c-torture/compile/20080812-1.c:
> >
> > 20080812-1.c: In function 'foo':
> > 20080812-1.c:21:1: error: insn does not satisfy its constraints:
> > (insn 49 76 77 3 (set (reg:PSI 6 p2 [144])
> >          (plus:PSI (reg:PSI 5 p1 [orig:145 ivtmp.1 ] [145])
> >              (reg:PSI 7 p3))) 20080812-1.c:15 193 {*addpsi3}
> >       (nil))
> > 20080812-1.c:21:1: internal compiler error: in
> > reload_cse_simplify_operands, at postreload.c:401
> > Please submit a full bug report,
> > with preprocessed source if appropriate.
> > See<http://gcc.gnu.org/bugs.html>  for instructions.
> >
> >
> > It seems that gcc wants to create an instruction like "p2=add(p1,p3)".
> > How can I tell him not to do that?
> > I tried to fiddle with the "p_d_general_operand" predication and use a
> > modified one for operand 2, but
> > at the time the constraint is called, I only see pseudo registers, and
> > don't know in which hard register
> > they will appear at the end.
> >
> > I'm using a gcc snapshot from Jan-19-2011.
> >
> > regards,
> > chris
>
> FWIW, I faced a similar challenge for my private port (ie. define add
> for different types of registers), and I got gcc to work by defining a
> single pattern for all adds, with predicates that don't discriminate on
> register classes: the register contraints do the job of selecting the
> proper combinations.
>
> But there is probably more than one way to do it.
>
> Cheers,
> JM

Hmm, isn't it the same here? The predicates "p_d_general_operand" allow pX and dX
(and "general_operand"), and the constraints select which combinations are vaild.
I forgot to mention that "a" constraint means pX registers, and d0d9 and d0d3 refer
to d0-d9 and d0-d3 registers.

regards,
chris