reload question

[Jeff Law]

On 06/23/10 11:22, Alex Turjan wrote:
> Hi,
> My port supports hardware loops generated by the following (do_end) pattern:
>
> (set (pc) (if_then_else (ne (match_operand:HI 0 "general_register_operand" "d")
>                             (const_int 0))
>                         (label_ref (match_operand 1 "" ""))
>                         (pc)))
>       (set  (match_operand:HI 2 "general_register_operand" "=0")
>           (plus:HI (match_operand:HI 3 "general_register_operand" "0")
>                            (const_int -1)))
>      (clobber (match_operand:BI 4 "predicate_register_operand" "=j"))
>
>
> When Im compiling a loop with high register pressure the register allocator does not allocate a register for the loop counter (i.e., operand 0) as it has a long life range. Thus operand 0 has to be reloaded but then I get a failure in the reload:
>
> error: unable to generate reloads for:
> (jump_insn 211 182 188 11 lib5.c:51 (parallel [
>              (set (pc)
>                  (if_then_else (ne (reg:HI 292 [ N ])
>                          (const_int 0 [0x0]))
>                      (label_ref 183)
>                      (pc)))
>              (set (reg:HI 292 [ N ])
>                  (plus:HI (reg:HI 292 [ N ])
>                      (const_int -1 [0xffffffffffffffff])))
>              (clobber (reg:BI 33 p1 [293]))
>          ]) 506 {do_endhi} (expr_list:REG_UNUSED (reg:BI 33 p1 [293])
>          (expr_list:REG_BR_PROB (const_int 9100 [0x238c])
>              (nil)))
>   ->  183)
> lib5.c:105:1: internal compiler error: in find_reloads, at reload.c:3821
>
> Can anybody give me a hint?
> I am aware of the following msg:
> http://gcc.gnu.org/ml/gcc/2001-09/msg00942.html
> but still dont know how to make reload do the work.
>    
insns which branch are not allowed to have output reloads.  You must 
support any kind of register as well as memory operands in your insn for 
the loop counter.

Jeff