x86: Swap destination/source to encode VEX only if possible

When encoding VEX, we can swap destination and source only if there are
more than 1 register operand.

	* config/tc-i386.c (build_vex_prefix): Swap destination and
	source only if there are more than 1 register operand.

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 7a82555..fc17226 100644 (file)
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-13  H.J. Lu  <hongjiu.lu@intel.com>
+
+       * config/tc-i386.c (build_vex_prefix): Swap destination and
+       source only if there are more than 1 register operand.
+
 2018-09-13  Jan Beulich  <jbeulich@suse.com>
 
        * config/tc-i386.c (operand_size_match): Also deal with three

diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 2bff48a..40b4583 100644 (file)
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -3364,9 +3364,10 @@ build_vex_prefix (const insn_template *t)
   else
     register_specifier = 0xf;
 
-  /* Use 2-byte VEX prefix by swapping destination and source
-     operand.  */
-  if (i.vec_encoding != vex_encoding_vex3
+  /* Use 2-byte VEX prefix by swapping destination and source operand
+     if there are more than 1 register operand.  */
+  if (i.reg_operands > 1
+      && i.vec_encoding != vex_encoding_vex3
       && i.dir_encoding == dir_encoding_default
       && i.operands == i.reg_operands
       && operand_type_equal (&i.types[0], &i.types[i.operands - 1])