unable to find a register to spill in class ‘MD_REGS’

["Rodrigo González Alberquilla"<rgalberquilla at fis dot ucm dot es>]

Dear GCC Developers/Users,

I am working on a port of a target backend to PISA architecture (a MIPS-IV like ISA used by the SimpleScalar simulator). When compiling libgcc2 for __muldi3:

#ifdef L_muldi3
DWtype
__muldi3 (DWtype u, DWtype v)
{
  const DWunion uu = {.ll = u};
  const DWunion vv = {.ll = v};
  DWunion w = {.ll = __umulsidi3 (uu.s.low, vv.s.low)};

  w.s.high += ((UWtype) uu.s.low * (UWtype) vv.s.high
               + (UWtype) uu.s.high * (UWtype) vv.s.low);

  return w.ll;
}
#endif

I get the following error:
../.././gcc/libgcc2.c: In function ‘__muldi3’:
../.././gcc/libgcc2.c:542: error: unable to find a register to spill in class ‘MD_REGS’
../.././gcc/libgcc2.c:542: error: este es el insn:
(insn 37 36 38 2 (set (reg:DI 116)
        (mult:DI (zero_extend:DI (reg:SI 3 v1 [orig:117 __ul ] [117]))
            (zero_extend:DI (reg:SI 2 v0 [orig:118 __vl ] [118])))) 14 {umulsidi3_32bit_internal} (nil)
    (expr_list:REG_DEAD (reg:SI 3 v1 [orig:117 __ul ] [117])
        (expr_list:REG_DEAD (reg:SI 2 v0 [orig:118 __vl ] [118])
            (nil))))

I have compile it with -da and the dumps are:

greg:
Spilling for insn 37.
Using reg 4 for reload 0
reload failure for reload 1

Reloads for insn # 37
Reload 0: GR_REGS, RELOAD_FOR_OUTPUT_ADDRESS (opnum = 0), can't combine, secondary_reload_p
Reload 1: reload_out (DI) = (reg:DI 116)
        MD_REGS, RELOAD_FOR_OUTPUT (opnum = 0)
        reload_out_reg: (reg:DI 116)
        secondary_out_reload = 0

lreg:
[...]
  Register 116 costs: LEA_REGS:10000000 GR_REGS:10000000 MEM:8000
[...]
Register 116 used 2 times across 2 insns in block 2; set 1 time; 8 bytes; NO_REGS or none.
[...]
(insn 37 36 38 2 (set (reg:DI 116)
        (mult:DI (zero_extend:DI (reg:SI 117 [ __ul ]))
            (zero_extend:DI (reg:SI 118 [ __vl ])))) 14 {umulsidi3_32bit_internal} (nil)
    (expr_list:REG_DEAD (reg:SI 117 [ __ul ])
        (expr_list:REG_DEAD (reg:SI 118 [ __vl ])
            (nil))))
[...]

I have read a thread of a guy having a paroblem like this but it has not helped me. If anybody would tell me where the problem could be, I would be very pleased.

Regards,
Rodrigo González