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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.
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Jan Beulich 2019-06-25 09:40:44 +02:00 committed by Jan Beulich
parent 54fbadc0c3
commit 4970191fa5
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gas/ChangeLog
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@ -1,3 +1,8 @@
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().

6
gas/doc/c-i386.texi
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@ -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}