[PATCH] x86: document certain command line options as "dangerous"
Jan Beulich
JBeulich@suse.com
Mon Jun 24 13:50:00 GMT 2019
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}
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