"H.J. Lu" <hjl.to...@gmail.com> writes:
>>> LRA has
>>>
>>> if (REG_P (reg) && (ep = get_elimination (reg)) != NULL)
>>> {
>>> rtx to_rtx = replace_p ? ep->to_rtx : ep->from_rtx;
>>>
>>> if (! replace_p)
>>> {
>>> offset += (ep->offset - ep->previous_offset);
>>> offset = trunc_int_for_mode (offset, GET_MODE (plus_cst_src));
>>> }
>>>
>>> if (GET_CODE (XEXP (plus_cst_src, 0)) == SUBREG)
>>> to_rtx = gen_lowpart (GET_MODE (XEXP (plus_cst_src, 0)),
>>> to_rtx);
>>>
>>> Reload has
>>>
>>> rtx to_rtx = ep->to_rtx;
>>> offset += ep->offset;
>>> offset = trunc_int_for_mode (offset, GET_MODE (plus_cst_src));
>>>
>>> if (GET_CODE (XEXP (plus_cst_src, 0)) == SUBREG)
>>> to_rtx = gen_lowpart (GET_MODE (XEXP (plus_cst_src, 0)),
>>> to_rtx);
>>>
>>> (gdb) call debug_rtx (ep->to_rtx)
>>> (reg/f:DI 7 sp)
>>> (gdb) call debug_rtx (ep->from_rtx)
>>> (reg/f:DI 16 argp)
>>> (gdb)
>>>
>>> gen_lowpart returns (reg/f:DI 7 sp) for reload and (reg:SI 16 argp)
>>> for LRA. They are caused by
>>>
>>> if (FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
>>> /* We should convert arg register in LRA after the elimination
>>> if it is possible. */
>>> && xregno == ARG_POINTER_REGNUM
>>> && ! lra_in_progress)
>>> return -1;
>>>
>>> It doesn't work in this case.
>>>
>>
>> This testcase shows that LRA can't convert arg register after
>> the elimination.
>>
> Here is a patch to remove ra_in_progress check for
> ARG_POINTER_REGNUM. Tested on Linux.x86-64.
> OK to install?
Thanks HJ. This looks good to me. As well as your testcase, I think
it would be dangerous to reduce this kind of subreg during non-final
elimination in cases where the argument pointer occupies more than one
hard register (like avr IIRC). We could end up with something like
ARG_POINTER_REGNUM+1, which wouldn't show up as an elimination register
during the rest of LRA.
It's important that we do get rid of the subreg during the final
elimination stage, but I think alter_subreg already handles that case.
Since this code is outside the LRA files: patch is OK if Vlad agrees.
Richard
