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Re: Setting precision for a PSImode type
- From: Peter Bigot <bigotp at acm dot org>
- To: Bernd Schmidt <bernds at codesourcery dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Mon, 5 Mar 2012 10:54:37 -0600
- Subject: Re: Setting precision for a PSImode type
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- References: <CAPOJ94Nb9Ub5_746eriWOyP4aK--4d5hL591XnEShEH-4xP+6A@mail.gmail.com> <4F54EBFD.4060605@codesourcery.com>
On Mon, Mar 5, 2012 at 10:38 AM, Bernd Schmidt <bernds@codesourcery.com> wrote:
> On 03/05/2012 05:24 PM, Peter Bigot wrote:
>> And is there any reason (other than it doesn't seem to have been done
>> before) to believe PSImode is the wrong way to support a
>> general-purpose 20-bit integral type in gcc?
>
> If you're using 4.7.0, it should be possible to use FRACTIONAL_INT_MODE
> and get reasonable results. However, it hasn't been tested much, since
> the final bits of the patch series which would have added 40 bit int
> support to the C frontend didn't make it in. See the discussion following
> ?http://gcc.gnu.org/ml/gcc-patches/2011-07/msg00079.html
Thanks for the reference; it very much seems what I'm trying to do
will be breaking new ground. I'm still using 4.6.x, though now that
4.7.x has forked off trunk I may update if that would make the task
easier. My preference would be to stick with PSImode, as I think
support for it in the machine description infrastructure will be
necessary (there are a large number of opcodes specific to operation
on 20-bit values).
Peter