diff --git a/x86/rex2.pl b/x86/rex2.pl
new file mode 100644
index 00000000..015d1940
--- /dev/null
+++ b/x86/rex2.pl
@@ -0,0 +1,25 @@
+#!/usr/bin/perl
+
+use integer;
+
+while (<>) {
+    chomp;
+    print $_;
+    if (!/\#/ &&
+	# VEX/XOP is implicit so no need to clutter
+	# the table with it...
+	!/\b(rex2|vex|evex|xop)\b/ &&
+	!/\bNOAPX\b/ &&
+	!/\bNOLONG\b/ &&
+	# Maps 2+ are not REX2 encodable, this is implicit
+	!/\b0f3[a8]\b/ &&
+	!/\b(m|map)([2-9]|[1][0-9])\b/ &&
+	((!/\b0f\b/ &&
+	  !/\b[^47ae][0-9a-f] [47ae][0-9a-f]\b/ &&
+	  /\b[47ae][0-9a-f]\b/) ||
+	 /\b0f [38][0-9a-f]\b/ ||
+	 /^(XSAVE|XRSTOR)/)) {
+	print ",NOAPX";
+    }
+    print "\n";
+}