x86: document certain command line options as "dangerous"

Message ID 5D10D50E020000780023AA78@prv1-mh.provo.novell.com
State New
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  • x86: document certain command line options as "dangerous"
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Commit Message

Jan Beulich June 24, 2019, 1:50 p.m.
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.

Comments

H.J. Lu June 24, 2019, 4:21 p.m. | #1
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.

Patch

--- 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}