This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH][m68k] Partially fix PR target/28181 (movqi from mem to address register)
Rask Ingemann Lambertsen <rask@sygehus.dk> writes:
> On Tue, Dec 12, 2006 at 12:27:04PM +0000, Richard Sandiford wrote:
>> I don't think this is the right approach. I think we should instead
>> allow address registers to store bytes, and define secondary_reload_class
>> accordingly (plus a few other related changes).
>
> From m68k_regno_mode_ok(), which implements HARD_REGNO_MODE_OK:
>
> /* Address Registers, can't hold bytes, can hold aggregate if
> fits in. */
> if (GET_MODE_SIZE (mode) == 1)
> return false;
> if (regno + GET_MODE_SIZE (mode) / 4 <= 16)
> return true;
>
> Are you planning to change that also? If not, there will be an
> inconsistency.
Yeah, that's what I meant by "we should allow address register to
store bytes".
> I just reread the documentation for HARD_REGNO_MODE_OK and I think
> m68k_regno_mode_ok() is more restrictive than it needs to be in that there
> is already a movqi pattern to copy QImode values between data registers and
> address registers.
Yes.
> Limited support for QImode operands on address registers
> could probably be added. For example,
>
> (define_insn "*addqi3"
> [(set (match_operand:QI 0 "nonimmediate_operand" "=...,*a,d")
> (plus:QI (match_operand:QI 1 "general_operand" "%...,0,0")
> (match_operand:QI 2 "general_operand" "...,di,*a")))
> "..."
> "@
> ...
> adda%.w %2,%0
> add%.w %2,%0"
> )
>
> but the condition codes will of course not be usable with the last two
> alternatives.
Yes. I think it would be better to hold off discussion until
I post the patch.
Richard