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Re: [PATCH 8/8] Add a common .md file and define standard constraints there
- From: Richard Sandiford <rdsandiford at googlemail dot com>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: Paul_Koning at Dell dot com, gcc-patches at gcc dot gnu dot org
- Date: Sat, 14 Jun 2014 10:58:45 +0100
- Subject: Re: [PATCH 8/8] Add a common .md file and define standard constraints there
- Authentication-results: sourceware.org; auth=none
- References: <87sinj9hhy dot fsf at talisman dot default> <87tx7z822q dot fsf at talisman dot default> <20140612192430 dot GB9914 at gate dot crashing dot org> <FFE56FBE-059E-4F25-8D61-3AFE37A98D5F at dell dot com> <20140612211842 dot GC13489 at gate dot crashing dot org>
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 âgâ by âmriâ? Thatâs 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