Re: [PATCH for-6.2 21/34] target/arm: Implement MVE VABAV

[Peter Maydell]

On Sat, 17 Jul 2021 at 21:50, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 7/13/21 6:37 AM, Peter Maydell wrote:
> > +#define DO_VABAV(OP, ESIZE, TYPE)                               \
> > +    uint32_t HELPER(glue(mve_, OP))(CPUARMState *env, void *vn, \
> > +                                    void *vm, uint32_t ra)      \
> > +    {                                                           \
> > +        uint16_t mask = mve_element_mask(env);                  \
> > +        unsigned e;                                             \
> > +        TYPE *m = vm, *n = vn;                                  \
> > +        for (e = 0; e < 16 / ESIZE; e++, mask >>= ESIZE) {      \
> > +            if (mask & 1) {                                     \
> > +                int64_t n0 = n[H##ESIZE(e)];                    \
> > +                int64_t m0 = m[H##ESIZE(e)];                    \
> > +                uint32_t r = n0 >= m0 ? (n0 - m0) : (m0 - n0);  \
>
> Any particular reason you're not using TYPE for n0 and m0?

I wanted to definitely be doing the subtraction with a signed
type wider than the inputs, because that's the way the
pseudocode effectively deals with it, and I didn't feel like
thinking through whether using the smaller and possibly
unsigned types would DTRT :-)

-- PMM