Re: [Qemu-devel] [PATCH v2 01/17] RISC-V: add vfp field in CPURISCVState

[Chih-Min Chao]

On Thu, Sep 12, 2019 at 6:39 AM Richard Henderson <
address@hidden> wrote:

> On 9/11/19 10:51 AM, Chih-Min Chao wrote:
> > Could  the VLEN be configurable in cpu initialization but not fixed in
> > compilation phase ?
> > Take the integer element as example  and the difference should be the
> > stride of vfp.vreg[x] isn't continuous
>
> Do you really want an unbounded amount of vector register storage?


 Hi Richard,

VLEN is implementation-defined parameter and the only limitation on spec is
that it must be power of 2.
What I prefer is the value could be adjustable in runtime.

>


> >     uint8_t *mem = malloc(size)
> >     for (int idx = 0; idx < 32; ++idx) {
> >         vfp.vreg[idx].u64 = (void *)&mem[idx * elem];
> >         vfp.vreg[idx].u32 = (void *)&mem[idx * elem];
> >         vfp.vreg[idx].u16 = (void *)&mem[idx * elem];
> >    }
>
> This isn't adjusting the stride of the elements.  And in any case this
> would
> have to be re-adjusted for every vsetvl.
>
>  Not sure about the relation with vsetvl. Could you provide an example ?

Chih-Min

>
> r~
>