Unable to reload subreg

[René Willemink <rene dot Willemink at dspfactory dot ch>]

Compiling the following code with my cross-compiler generates an error:

long long var1 = 10, var2 = 20;
long long result = var1 + var2;

This should perform a double word addition (HImode on my target). Since I haven't defined an addhi3 instruction, gcc tries to solve this problem with addqi3, and uses (subreg:QI (reg:HI)) to access the low and high part of this double word value. 
The problem I run into is that in my cross compiler seems not to be able to reload the destination (subreg:QI (reg:HI)) into a QImode register. This happens when I adjust the constraints to force the result into a register. When I allow the result in memory, no error occurs.

I get the following error:

test.c:35: error: unable to generate reloads for:
(insn 14 13 15 0 0x4019e440 (parallel [
            (set (subreg:QI (reg:HI 85) 0)
                (plus:QI (subreg:QI (reg:HI 83) 0)
                    (subreg:QI (reg:HI 84) 0)))
            (clobber (cc0))
        ]) 16 {addqi3_normal} (nil)
    (nil))
test.c:35: internal compiler error: in find_reloads, at reload.c:3629

This doesn't work:
(define_insn "addqi3_normal"
  [(set
    (match_operand:QI 0 "register_operand"    "=r")
    (plus:QI 
       (match_operand:QI 1 "register_operand"  "r")
       (match_operand:QI 2 "register_operand"  "r"))
    )
    (clobber (cc0))]

This does work, but I don't want the result to be in memory
(define_insn "addqi3_normal"
  [(set
    (match_operand:QI 0 "register_operand"    "=m")
    (plus:QI 
       (match_operand:QI 1 "register_operand"  "r")
       (match_operand:QI 2 "register_operand"  "r"))
    )
    (clobber (cc0))]

My question is, how can I get gcc to reload the destination subreg into a register.

Rene Willemink