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authorJan Beulich <jbeulich@novell.com>2019-06-25 09:40:44 +0200
committerJan Beulich <jbeulich@suse.com>2019-06-25 09:40:44 +0200
commit4970191fa557c4769697fb41db06f2dcb5f7de2e (patch)
tree01bb03968b1e653e8ef506878ddf48ca06982400 /gas
parent54fbadc0c35f3dad663e2e175ea8d60546ffd710 (diff)
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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.
Diffstat (limited to 'gas')
-rw-r--r--gas/ChangeLog5
-rw-r--r--gas/doc/c-i386.texi6
2 files changed, 11 insertions, 0 deletions
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}