Re: [PATCH v1 04/46] target/loongarch: Implement xvadd/xvsub

[Richard Henderson]

On 6/21/23 11:19, Song Gao wrote:
> 在 2023/6/20 下午8:25, Richard Henderson 写道:
> > On 6/20/23 11:37, Song Gao wrote:
> > > +static bool gvec_xxx(DisasContext *ctx, arg_xxx *a, MemOp mop,
> > > +                     void (*func)(unsigned, uint32_t, uint32_t,
> > > +                                  uint32_t, uint32_t, uint32_t))
> > > +{
> > > +    uint32_t xd_ofs, xj_ofs, xk_ofs;
> > > +
> > > +    CHECK_ASXE;
> > > +
> > > +    xd_ofs = vec_full_offset(a->xd);
> > > +    xj_ofs = vec_full_offset(a->xj);
> > > +    xk_ofs = vec_full_offset(a->xk);
> > > +
> > > +    func(mop, xd_ofs, xj_ofs, xk_ofs, 32, ctx->vl / 8);
> > > +    return true;
> > > +}
> >
> > Comparing gvec_xxx vs gvec_vvv for LSX,
> >
> > >     func(mop, vd_ofs, vj_ofs, vk_ofs, 16, ctx->vl/8);
> >
> > gvec_vvv will write 16 bytes of output, followed by 16 bytes of zero to satisfy 
> > vl / 8.
> >
> >
> > I presume this is the intended behaviour of mixing LSX with LASX, that the high 128-bits 
> > that are not considered by the LSX instruction are zeroed on write?
> Yes,  the LSX instruction  can ignore the high 128-bits.

Ignore != write zeros on output.  What is the behaviour?


r~