Re: [PATCH v6 09/15] target/riscv: Add Zvkned ISA extension support

[Richard Henderson]

On 6/29/23 17:10, Max Chou wrote:
> On 2023/6/28 5:07 PM, Richard Henderson wrote:
> > You can eliminate the vstart % EGS test, and the vstart < vl test, when 
> > VSTART_EQ_ZERO.
> > You can eliminate the vl % EGS test when VL_EQ_VLMAX.
> >
> > You could move all of these tests out of line, into a helper_foo_chk() function which 
> > performs the checks and then calls helper_foo().
> Hi Richard
>
> Thank you for the suggestion.
> I'll provide the v7 patch set with this suggestion.
>
> But I have an question about the vstart < vl test.
> I think that we can't eliminate the vstart < vl test when both the vstart and vl are equal 
> to zero.
> Although this situation means that the instructions will do nothing.

We know vlmax != 0 (there's some architectural minimum).
Therefore if VL_EQ_VLMAX, vl != 0 and if VSTART_EQ_ZERO, then vstart < vl.


r~