From 4970191fa557c4769697fb41db06f2dcb5f7de2e Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 25 Jun 2019 09:40:44 +0200 Subject: 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. --- gas/doc/c-i386.texi | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'gas/doc') 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} -- cgit v1.1