[libre-riscv-dev] spike-sv non-default element widths

[lkcl]

On Fri, Oct 26, 2018 at 8:18 AM Jacob Lifshay <programmerjake at gmail.com> wrote:
>
> On Fri, Oct 26, 2018 at 12:01 AM lkcl <lkcl at libre-riscv.org> wrote:
>
> > On Fri, Oct 26, 2018 at 1:43 AM lkcl <lkcl at libre-riscv.org> wrote:
> > >
> > > okay!  at last, retrieving / storing to registers (integer only at the
> > > moment) actually works, with a c.mv preliminary test, on bit-widths of
> > > default (xlen), 8, 16 and 32.  i've yet to put in sign/zero-extension,
> > > that's going to be interesting / tricky and i may need some help.
> >
> I must have missed something,

 http://lists.libre-riscv.org/pipermail/libre-riscv-dev/2018-October/000122.html

> as last I had heard the widths used were
> default, default * 2, default / 2 and 8. I like the new widths better.

 yeah they kinda feel right, and, also, the logic for working out the
max elwidth is real simple.  0b00 in lhs OR 0b00 in rhs equals 0b00;
otherwise max(lhs, rhs).  so the target ends up as default bitwidth if
either src op is default.  quite interesting.

l.