Problem while writing Machine-description.

[Peter Kuschnerus]

Hi,

I have instructions with variants to yield the result in register,
promoted to either signdness (unsigned or signed).
I aim to use the variant with signed promotion, if the type is signed,
and otherwise to use the variant with unsigned ptomotion.

I try this as follows:

The macro PROMOTE_MODE is defined that way,
that all modes are promoted to full size of registers (DImode),
with the same signedness as the type.

The define_insn trys to get the promoted signdness of the output value
by using the macro SUBREG_PROMOTED_UNSIGNED_P,
to check which variant of instruction to be used.

The define_insn look this:

(define_insn "addsi3"
  [(set (subreg:SI (match_operand:SI 0 "register_operand" "=r") 0)
        (plus:SI (match_operand:SI 1 "register_operand" "%r")
                 (match_operand:SI 2 "register_operand" "r")))]
  ""
{
  if (SUBREG_PROMOTED_UNSIGNED_P(operands[0]))
    return "add (unsigned32)%0, %1, %2";
  return "add (signed32)%0, %1, %2";
})

>From the macro I get allways FALSE.
I tried varying the RTL-expression,
but I did not get any other than FALSE from SUBREG_PROMOTED_UNSIGNED_P.

I wonder what I am doing wrong.
I do not know if this way is possible at all.
Please does someone know a solution.

Regards,
Peter Kuschnerus