Re: [PATCH v9 04/10] target/riscv/vector_helper.c: update tail with vext_set_tail_elems_1s()

[Daniel Henrique Barboza]

On 3/10/24 04:41, Richard Henderson wrote:
> On 3/9/24 10:43, Daniel Henrique Barboza wrote:
> > Change all code that updates tail elems to use vext_set_tail_elems_1s()
> > instead of vext_set_elems_1s().
> >
> > Setting 'env->vstart=0' needs to be the very last thing a helper does
> > because env->vstart is being checked by vext_set_tail_elems_1s().
>
> I did wonder if it would be worth doing the vstart = 0 in 
> vext_set_tail_elems_1s, allowing that to be the very last thing in each helper, 
> and could be tail called.


Some insns don't update tail, e.g. vext_ldst_whole(), and we would need to
clear vstart explicitly in them regardless. Might as well deal with clearing
vstart in every helper to make them consistent.


Thanks,

Daniel

> > A side effect of this change is that a lot of 'vta' local variables got
> > unused. The reason is that 'vta' was being fetched to be used with
> > vext_set_elems_1s() but vext_set_tail_elems_1s() doesn't use it - 'vta' is
> > retrieve inside the helper using 'desc'.
> >
> > Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>
>
> r~