[PATCH] x86: document certain command line options as "dangerous"

H.J. Lu hjl.tools@gmail.com
Mon Jun 24 16:21:00 GMT 2019


On Mon, Jun 24, 2019 at 6:50 AM Jan Beulich <JBeulich@suse.com> wrote:
>
> Errata BT36, BT41, and BT230 mean that gas may, when using one ofthese
> options, produce code that causes #UD on (at least) SandyBridge systems.
>
> gas/
> 2019-06-24  Jan Beulich  <jbeulich@suse.com>
>
>         * doc/c-i386.texi: Mark -mavxscalar= and -mvexwig as dangrous to
>         use.
>
> --- a/gas/doc/c-i386.texi
> +++ b/gas/doc/c-i386.texi
> @@ -303,6 +303,9 @@ AVX instructions with 128bit vector leng
>  @option{-mavxscalar=@var{256}} will encode scalar AVX instructions
>  with 256bit vector length.
>
> +WARNING: Don't use this for production code - due to CPU errata the
> +resulting code may not work on certain models.
> +
>  @cindex @samp{-mvexwig=} option, i386
>  @cindex @samp{-mvexwig=} option, x86-64
>  @item -mvexwig=@var{0}
> @@ -313,6 +316,9 @@ instructions with vex.w = 0, which is th
>  @option{-mvexwig=@var{1}} will encode WIG EVEX instructions with
>  vex.w = 1.
>
> +WARNING: Don't use this for production code - due to CPU errata the
> +resulting code may not work on certain models.
> +
>  @cindex @samp{-mevexlig=} option, i386
>  @cindex @samp{-mevexlig=} option, x86-64
>  @item -mevexlig=@var{128}
>

OK.

Thanks.

-- 
H.J.



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