Re: [PATCH v11 4/7] target/riscv: remove 'over' brconds from vector trans

[Richard Henderson <richard.henderson@linaro.org>]

On 3/11/24 03:58, Daniel Henrique Barboza wrote:
> Most of the vector translations has this following pattern at the start:
> 
>      TCGLabel *over = gen_new_label();
>      tcg_gen_brcond_tl(TCG_COND_GEU, cpu_vstart, cpu_vl, over);
> 
> And then right at the end:
> 
>       gen_set_label(over);
>       return true;
> 
> This means that if vstart >= vl we'll not set vstart = 0 at the end of
> the insns - this is done inside the helper that is being skipped.  The
> reason why this pattern hasn't been a bigger problem is because the
> conditional vstart >= vl is very rare.
> 
> Checking all the helpers in vector_helper.c we see all of them with a
> pattern like this:
> 
>      for (i = env->vstart; i < vl; i++) {
>          (...)
>      }
>      env->vstart = 0;
> 
> Thus they can handle vstart >= vl case gracefully, with the benefit of
> setting env->vstart = 0 during the process.

You'll want to update this comment for VSTART_CHECK_EARLY_EXIT


r~