Re: [PATCH v4 01/17] x86/mpx: Do not use SIB index if index points to R/ESP

[Ricardo Neri]

On Fri, 2017-02-24 at 09:47 -0500, Nathan Howard wrote:
>         Also, this code would read better with the inner test
>         reversed or done first
>         
>                         if (indx_offset < 0) {
>                                 if (indx_offset != -EDOM)
>                                         goto out_err;
>                                 indx = 0;
>                         } else {
>                                 indx = regs_get_register(etc...)
>                         }
>         
>         or
>                         if (indx_offset == -EDOM)
>                                 indx = 0;
>                         else if (indx_offset < 0)
>                                 goto err;
> 
> 
> Or goto out_err;
> 
> 
>                         else
>                                 indx = regs_get_register(etc...)
>         
>         The compiler should generate the same code in any
>         case, but either could improve reader understanding.
> 
> 
> Also, it may be a tweak more efficient to handle the most likely
> runtime case in the conditional stack first (whichever that may be).

The most likely case will be a positive value but I need to check for
negatives first :( I could wrap the first conditional in an "unlikely".

Thanks and BR,
Ricardo