x86: Add {rex} pseudo prefix

[external/binutils.git] / gas / doc / c-i386.texi

diff --git a/gas/doc/c-i386.texi b/gas/doc/c-i386.texi
index e669c5f..6b2def0 100644 (file)
--- a/gas/doc/c-i386.texi
+++ b/gas/doc/c-i386.texi
@@ -642,6 +642,11 @@ Different encoding options can be specified via pseudo prefixes:
 
 @item
 @samp{@{evex@}} --  encode with EVEX prefix.
+
+@item
+@samp{@{rex@}} -- prefer REX prefix for integer and legacy vector
+instructions (x86-64 only).  Note that this differs from the @samp{rex}
+prefix which generates REX prefix unconditionally.
 @end itemize
 
 @cindex conversion instructions, i386