On Thu, Nov 12, 2020 at 6:51 PM Uros Bizjak <ubiz...@gmail.com> wrote:
> > > > Yes, removed 'code' and value_mode by checking VECTOR_MODE_P and use
> > > > GET_MODE_INNER
> > > > for value_mode. ".md expanders" shall support for integer constants
> > > > index mode, but
> > > > I guess they shouldn't be expanded by IFN as this function is for
> > > > variable index
> > > > insert only? Anyway, the v3 patch used VOIDmode check...
> >
> > I'm not sure what best to do here, as said accepting "any" (integer) mode as
> > input is desirable (SImode, DImode but eventually also smaller modes). How
> > that can be best achieved I don't know.
>
> I was expecting something similar to how extvM/extzvM operands are
> handled here. We have:
>
> Operands 0 and 1 both have mode M. Operands 2 and 3 have a
> target-specific mode.
>
> Please note operands 2 and 3 having a "target-specific" mode, handled
> in optabs-query.c as:
>
> machine_mode struct_mode = data->operand[struct_op].mode;
> if (struct_mode == VOIDmode)
> struct_mode = word_mode;
> if (mode != struct_mode)
> return false;
>
> > Why's not specifying any mode in the patter no good? Just make sure you
> > appropriately extend/subreg it? We can make sure it will be an integer
> > mode in the expander itself.
>
> IIRC, having known mode, expanders can use create_convert_operand_to,
> and the middle-end will do the above by itself. Also note that at
> least two targets specify SImode, so register operands are currently
> ineffective there.
On a related note, the pattern is currently expanded as (see
store_bit_field_1 in expmed.c):
create_fixed_operand (&ops[0], op0);
create_input_operand (&ops[1], value, innermode);
create_integer_operand (&ops[2], pos);
I don't think calling create_integer_operand on register operand is
correct. The function comment says:
/* Make OP describe an input operand that has value INTVAL and that has
no inherent mode. This function should only be used for operands that
are always expand-time constants. The backend may request that INTVAL
be copied into a different kind of rtx, but it must specify the mode
of that rtx if so. */
Uros.
