Re: [PATCH v3 26/51] target/arm: Implement SME LD1, ST1

[Peter Maydell]

On Thu, 23 Jun 2022 at 21:36, Richard Henderson
<richard.henderson@linaro.org> wrote:
> On 6/23/22 04:41, Peter Maydell wrote:
> > We now have several rather long functions that are
> > pretty complicated and pretty similar handling the various
> > SVE and SME loads and stores. Is there really no hope for
> > sharing code ?
>
> I'm not sure.  Maybe.  The two issues are:
>
> (1) sve ld4/st4 -- arm didn't make z29-z31 illegal, but defined wraparound to 
> z0.  So I
> pass in a Zreg number not a pointer to those routines.  So the routines can't 
> be reused
> for Zarray without changing that.
>
> (2) sme ld1/st1 vertical slice, which significantly alters the spacing 
> between the elements.
>
> One possibility for these cases is to perform the load into 
> env->some_scratch_space, then
> copy into the final position afterward, and the reverse for stores.
>
> Is that preferable?  Do you see another alternative?

Hmm, loading into a scratch space seems a bit clunky too.
I'll leave it to your judgement but I guess since you've already
written and tested the code we have here that argues for going
with what we have. Maybe we'll come back in six months and
realize there's a neater approach. (The GIC ITS code ended up
being refactored like that.)

-- PMM