On Mon, Mar 5, 2012 at 10:38 AM, Bernd Schmidt <ber...@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
