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