Another problem with PIC port, too many reloads for insn

[Robert Baruch]

Hi all,

No, not Position Independent Code... this is the PIC microcontroller
port I'm working on. The one that requires that all moves (and all
adds except increments) go through the W register.

I have changed GO_IF_LEGITIMATE_ADDRESS to accept only these
expressions for valid addresses:

FSR -- the only register which can be used as an indirect pointer
post_inc(FSR)
constant

I specifically left out reg+offset because I want to force gcc to
compute that first, then put the result in FSR.

The problem happens with this insn: set ( subreg ( pseudo-260, 0 ),
const_int ( 0 ) ).

The pseudo gets replaced with mem ( plus ( FP, 104 ) ) where FP is the
register where I'm holding the frame pointer.

find_reloads for the insn computes five reloads:

(gdb) p rld[0]
$32 = {
  in = 0x0, 
  out = 0x0, 
  class = W_REG, 
  inmode = QImode, 
  outmode = VOIDmode, 
  mode = QImode, 
  nregs = 1, 
  inc = 0, 
  in_reg = 0x0, 
  out_reg = 0x0, 
  regno = -1, 
  reg_rtx = 0x0, 
  opnum = 0, 
  secondary_in_reload = -1, 
  secondary_out_reload = -1, 
  secondary_in_icode = CODE_FOR_nothing, 
  secondary_out_icode = CODE_FOR_nothing, 
  when_needed = RELOAD_FOR_OPADDR_ADDR, 
  optional = 0, 
  nocombine = 1, 
  secondary_p = 1, 
  nongroup = 0
}
(gdb) p rld[1]
$33 = {
  in = 0x446f90, 
      (plus:QI (reg/f:QI 49 R20/FP)
        (const_int 104 [0x68]))
  out = 0x0, 
  class = GENERAL_REGS, 
  inmode = QImode, 
  outmode = VOIDmode, 
  mode = QImode, 
  nregs = 1, 
  inc = 0, 
  in_reg = 0x446fa8, 
  out_reg = 0x0, 
  regno = -1, 
  reg_rtx = 0x0, 
  opnum = 0, 
  secondary_in_reload = 0, 
  secondary_out_reload = -1, 
  secondary_in_icode = CODE_FOR_nothing, 
  secondary_out_icode = CODE_FOR_nothing, 
  when_needed = RELOAD_FOR_OPADDR_ADDR, 
  optional = 0, 
  nocombine = 1, 
  secondary_p = 0, 
  nongroup = 0
}
(gdb) p rld[2]
$34 = {
  in = 0x0, 
  out = 0x0, 
  class = W_REG, 
  inmode = VOIDmode, 
  outmode = QImode, 
  mode = QImode, 
  nregs = 1, 
  inc = 0, 
  in_reg = 0x0, 
  out_reg = 0x0, 
  regno = -1, 
  reg_rtx = 0x0, 
  opnum = 0, 
  secondary_in_reload = -1, 
  secondary_out_reload = -1, 
  secondary_in_icode = CODE_FOR_nothing, 
  secondary_out_icode = CODE_FOR_nothing, 
  when_needed = RELOAD_FOR_OPERAND_ADDRESS, 
  optional = 1, 
  nocombine = 1, 
  secondary_p = 1, 
  nongroup = 0
}
(gdb) p rld[3]
$35 = {
  in = 0x0, 
  out = 0x446f9c, 
      (mem:QI (plus:QI (reg/f:QI 49 R20/FP)
              (const_int 104 [0x68])) [6 __x0+0 S4 A8])
  class = NO_REGS, 
  inmode = VOIDmode, 
  outmode = QImode, 
  mode = QImode, 
  nregs = 1, 
  inc = 0, 
  in_reg = 0x0, 
  out_reg = 0x43c534, 
  regno = -1, 
  reg_rtx = 0x0, 
  opnum = 0, 
  secondary_in_reload = -1, 
  secondary_out_reload = 2, 
  secondary_in_icode = CODE_FOR_nothing, 
  secondary_out_icode = CODE_FOR_nothing, 
  when_needed = RELOAD_FOR_OUTPUT, 
  optional = 1, 
  nocombine = 0, 
  secondary_p = 0, 
  nongroup = 0
}
(gdb) p rld[4]
$36 = {
  in = 0x40e37210, 
      (const_int 0 [0x0])
  out = 0x0, 
  class = W_REG, 
  inmode = QImode, 
  outmode = VOIDmode, 
  mode = QImode, 
  nregs = 1, 
  inc = 0, 
  in_reg = 0x40e37210, 
  out_reg = 0x0, 
  regno = -1, 
  reg_rtx = 0x0, 
  opnum = 1, 
  secondary_in_reload = -1, 
  secondary_out_reload = -1, 
  secondary_in_icode = CODE_FOR_nothing, 
  secondary_out_icode = CODE_FOR_nothing, 
  when_needed = RELOAD_FOR_INPUT, 
  optional = 0, 
  nocombine = 0, 
  secondary_p = 0, 
  nongroup = 0
}


Later on, in find_reload_regs for this instruction, the reload order
is determined to be 0, 4, 1, 2, 3. Reload 0 snags the W register, and
of course reload 4 fails and causes GCC to abort, complaining that it
cannot find a spill register because the W register required for
reload 4 is already used.

I need some advice on what I should be doing to help GCC resolve this
insn. I'm including my current port so you can look at it and laugh :)

Thanks for any help!

--Rob
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pic-20050122.tgz
Type: application/x-gzip
Size: 10561 bytes
Desc: not available
URL: <https://gcc.gnu.org/pipermail/gcc/attachments/20050122/f19e7599/attachment.bin>