Re: Reload problems with only one base reg for "base + offset" addressing mode

[redriver jiang <jiang dot redriver at gmail dot com>]

Hi,

You mean I should define insn like this:

(define_insn "*iorqi3_imm"
 [(set (mem:QI (match_operand:HI 0 "register_operand"       "b"))
       (ior:QI (mem:QI (match_operand:HI 1 "register_operand"   "b")
                     (mem:QI (plus: HI (match_operand:HI 2
"register_operand"  "f")
                                   (match_operand: 3 HI
"immediate_operand" "K")   ))))]
""
"..."
[( set_attr "length" "1" )])

"b" for R16,R17,R18, and "f" for R18, "K" for immediate operand with
range "0-127"?


Thanks!


2010/7/20 Ian Lance Taylor <iant@google.com>:
> redriver jiang <jiang.redriver@gmail.com> writes:
>
>> I am porting GCC to a 8bit architecture, and now I have problem on
>> reload problem on addressing mode.
>> Besides 15 general registers, it has three 16bit address registers,
>> R16,R17,R18.
>> R16,R17,R18 are able to be as base register in "base" address mode,
>> but only R18 can be base regs for "base+offse(immediate)t" address
>> mode.
>> I make "BASE_REGS" class ?for "R16,R17,R18", and "POINTER_REG" class
>> for R18, and frame pointer is R18, the maxim "offset" in "base+offset"
>> is 127.
>>
>> And now the test compiler sometimes generate following errors:
>>
>> test3.c: In function 'OS_EventTaskWait':
>> test3.c:62: error: unable to find a register to spill in class 'POINTER_REG'
>> test3.c:62: error: this is the insn:
>> (insn 58 57 61 2 (set (mem/s:QI (plus:HI (reg:HI 16 R16 [51])
>> ? ? ? ? ? ? ? ? (const_int 5 [0x5])) [0 <variable>.OSEventTbl S1 A8])
>> ? ? ? ? (ior:QI (mem/s:QI (plus:HI (reg:HI 16 R16 [51])
>> ? ? ? ? ? ? ? ? ? ? (const_int 5 [0x5])) [0 <variable>.OSEventTbl S1 A8])
>> ? ? ? ? ? ? (mem/s:QI (plus:HI (reg:HI 17 R17 [orig:38 OSTCBCur.0 ] [38])
>> ? ? ? ? ? ? ? ? ? ? (const_int 14 [0xe])) [0 <variable>.OSTCBBitX+0 S1
>> A8]))) 25 {*iorqi3_noimm} (insn_list:REG_DEP_TRUE 51 (nil))
>> ? ? (expr_list:REG_DEAD (reg:HI 17 R17 [orig:38 OSTCBCur.0 ] [38])
>> ? ? ? ? (expr_list:REG_DEAD (reg:HI 16 R16 [51])
>> test3.c:62: confused by earlier errors, bailing out.
>
> You should be able to fix this by using constraints. ?Define a
> constraint which uses the base register and define one which permits one
> of the indirect registers. ?Write different alternatives such that only
> one operand uses the base register in each alternative. ?Then reload
> should be able to pick the best one, and reload the other addresses into
> the indirect register.
>
> Ian
>