[binutils-gdb] x86: document certain command line options as "dangerous"

[Jan Beulich]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4970191fa557c4769697fb41db06f2dcb5f7de2e

commit 4970191fa557c4769697fb41db06f2dcb5f7de2e
Author: Jan Beulich <jbeulich@novell.com>
Date:   Tue Jun 25 09:40:44 2019 +0200

    x86: document certain command line options as "dangerous"
    
    Errata BT36, BT41, and BT230 mean that gas may, when using one ofthese
    options, produce code that causes #UD on (at least) SandyBridge systems.

Diff:
---
 gas/ChangeLog       | 5 +++++
 gas/doc/c-i386.texi | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/gas/ChangeLog b/gas/ChangeLog
index d2175b6..b76ae78 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,5 +1,10 @@
 2019-06-25  Jan Beulich  <jbeulich@suse.com>
 
+	* doc/c-i386.texi: Mark -mavxscalar= and -mvexwig as dangrous to
+	use.
+
+2019-06-25  Jan Beulich  <jbeulich@suse.com>
+
 	* tc-i386.c (process_suffix): Use is_any_vex_encoding().
 
 2019-06-25  Jan Beulich  <jbeulich@suse.com>
diff --git a/gas/doc/c-i386.texi b/gas/doc/c-i386.texi
index 9d821ae..908c6ca 100644
--- a/gas/doc/c-i386.texi
+++ b/gas/doc/c-i386.texi
@@ -303,6 +303,9 @@ AVX instructions with 128bit vector length, which is the default.
 @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 the default.
 @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}