Bernd Schmidt 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
The avr backend defines a 24-bit scalar integer type by FRACTIONAL_INT_MODE (PSI, 24, 3); INT_MODE (PSI, 3) shred the compiler at some place, don't remember where. The avr 24-bit types don't work smooth, see PR51527. Johann
