Re: [Qemu-devel] [PATCH 2/2] target/arm: Only implement doubles if the FPU supports them

[Peter Maydell <peter.maydell@linaro.org>]

On Fri, 14 Jun 2019 at 18:21, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 6/14/19 3:44 AM, Peter Maydell wrote:
> > @@ -173,6 +173,11 @@ static bool trans_VSEL(DisasContext *s, arg_VSEL *a)
> >          ((a->vm | a->vn | a->vd) & 0x10)) {
> >          return false;
> >      }
> > +
> > +    if (dp && !dc_isar_feature(aa32_fpdp, s)) {
> > +        return false;
> > +    }
>
> Would it be cleaner to define something like
>
> static bool vfp_dp_enabled(DisasContext *s, int regmask)
> {
>     if (!dc_isar_feature(aa32_fpdp, s)) {
>         /* All double-precision disabled.  */
>         return false;
>     }
>     if (!dc_isar_feature(aa32_fp_d32, s) && (regmask & 0x10)) {
>         /* D16-D31 do not exist.  */
>         return false;
>     }
>     return true;
> }
>
> Then use
>
>     if (dp && !vfp_dp_enabled(s, a->vm | a->vn | a->vd))
>
> ?

It would be less code, but I don't think the "are we using
a register than doesn't exist" and the "do we have dp support"
checks are really related, and splitting the "OR the register
numbers together" from the "test the top bit" makes that
part look rather less clear I think.

thanks
-- PMM