Hi,
I would like to split a movhi instruction from an immediate to a const
address to 2 movqi instructions.
(I'm using gcc 4.5.3 but i dont think it matters in this case)
My motivation is the following:
Code in the form:
OCR2RA = 1;
compiles to:
ldi r24, 0x01 ; 1
ldi r25, 0x00 ; 0
sts 0x00F7, r25
sts 0x00F6, r24
instead of
ldi r24, 0x01 ; 1
ldi r25, 0x00 ; 0
sts 0x00F7, r25
sts 0x00F6, __zero_reg__
I'm pretty sure its caused by the following code:
(define_expand "movhi"
[(set (match_operand:HI 0 "nonimmediate_operand" "")
(match_operand:HI 1 "general_operand" ""))]
""
"
{
/* One of the ops has to be in a register. */
if (!register_operand(operand0, HImode)
&& !(register_operand(operand1, HImode) || const0_rtx == operands[1]))
{
operands[1] = copy_to_mode_reg(HImode, operand1);
}
}")
i would like to fix it but i know very little about gcc internals.
i tried to do something like:
(define_expand "movhi"
[(set (match_operand:HI 0 "nonimmediate_operand" "")
(match_operand:HI 1 "general_operand" ""))]
""
"
{
rtx base = XEXP (operands[0], 0);
if (GET_CODE (operands[1]) == CONST_INT
&& CONSTANT_ADDRESS_P (base))
{
short value = INTVAL (operands[1]);
short address = INTVAL (base);
emit_move_insn(gen_rtx_MEM(QImode,address+1), GEN_INT(value >> 8));
emit_move_insn(gen_rtx_MEM(QImode,address), GEN_INT(value & 0xff));
DONE;
}
else /* One of the ops has to be in a register. */
if (!register_operand(operand0, HImode)
&& !(register_operand(operand1, HImode) || const0_rtx == operands[1]))
{
operands[1] = copy_to_mode_reg(HImode, operand1);
}
}")
but then i get Segmentation fault when trying to compile code.
Can someone please point me to the right direction?
Thank,
Ilya.
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