Re: [PATCH 23/36] target/arm: Convert Neon 64-bit element 3-reg-same insns

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

On Thu, 30 Apr 2020 at 21:54, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 4/30/20 11:09 AM, Peter Maydell wrote:
> > +
> > +    rn = tcg_temp_new_i64();
> > +    rm = tcg_temp_new_i64();
> > +    rd = tcg_temp_new_i64();
> > +
> > +    for (pass = 0; pass < (a->q ? 2 : 1); pass++) {
> > +        neon_load_reg64(rn, a->vn + pass);
> > +        neon_load_reg64(rm, a->vm + pass);
> > +        fn(rd, rm, rn);
> > +        neon_store_reg64(rd, a->vd + pass);
> > +    }
> > +
> > +    tcg_temp_free_i64(rn);
> > +    tcg_temp_free_i64(rm);
> > +    tcg_temp_free_i64(rd);
> > +
> > +    return true;
> > +}
> > +
> > +#define DO_3SAME_64(INSN, FUNC)                                         \
> > +    static bool trans_##INSN##_3s(DisasContext *s, arg_3same *a)        \
> > +    {                                                                   \
> > +        return do_3same_64(s, a, FUNC);                                 \
> > +    }
>
> You can morph this into the gvec interface like so:
>
> #define DO_3SAME_64(INSN, FUNC) \
>     static void gen_##INSN##_3s(unsigned vece, uint32_t rd_ofs,
>                                 uint32_t rn_ofs, uint32_t rm_ofs,
>                                 uint32_t oprsz, uint32_t maxsz)
>     {
>         static const GVecGen3 op = { .fni8 = FUNC };
>         tcg_gen_gvec_3(rd_ofs, rn_ofs, rm_ofs,
>                        oprsz, maxsz, &op);
>     }
>     DO_3SAME(INSN, gen_##INSN##_3s)
>
> The .fni8 function tells gvec that we have a helper that processes the
> operation in 8 byte chunks.  It will handle the pass loop for you.

This doesn't quite work, because these are shift ops and
so the operands are passed to the helper in the order
rd, rm, rn. Reshuffling the order of arguments to
tcg_gen_gvec_3() fixes this, though.

I guess I should call the macro DO_3SAME_SHIFT64, I hadn't
noticed it was shift specific because the only thing we do
with it is shifts.

thanks
-- PMM