[PATCH 8/8] Add a common .md file and define standard constraints there

[Richard Sandiford]

Segher Boessenkool <segher@kernel.crashing.org> writes:
>> > * cris, m68k, pdp11, and vax actually use "g".
>> > 
>> > So it won't be all that much work to completely get rid of "g".
>> > Do we want that?
>> 
>> Is it simply a matter of replacing “g” by “mri”?  That’s what the doc
>> suggests.  Or is there more to the story than that?
>
> As far as I know "g" and "rmi" are equivalent, yes.  "g" is easier to
> type and read if you use it a lot (only ancient targets really); the
> compiler will probably become somewhat slower for those targets, and
> perhaps somewhat faster for all others.  Hard to say without doing the
> work and measuring the result :-)

FWIW, I had a follow-on patch that created the recog_op_alt data at
build time and made the constraints field of that structure point to
CONSTRAINT_* bytes rather than raw strings.  That involved converting
"g" to "rmi" like you say and also meant adding CONSTRAINT_*s for "#"
and "?".  (Other non-operand characters can be dropped since the information
is given directly in the recog_op_alt.)

It didn't really seem to be much of a win though.

Richard