pattern problem with register assignment

[Christian Grössler <chris at groessler dot org>]

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