re PR target/70168 (Wrong code generation in __sync_val_compare_and_swap on PowerPC)

	PR target/70168
	* config/rs6000/rs6000.c (rs6000_expand_atomic_compare_and_swap):
	Handle overlapping retval and newval.

From-SVN: r234126

gcc/ChangeLog

+2016-03-10  Ulrich Weigand  <Ulrich.Weigand@de.ibm.com>
+
+	PR target/70168
+	* config/rs6000/rs6000.c (rs6000_expand_atomic_compare_and_swap):
+	Handle overlapping retval and newval.
+
 2016-03-10  Nick Clifton  <nickc@redhat.com>
 
 	PR target/7044

gcc/config/rs6000/rs6000.c

@@ -22283,6 +22283,9 @@ rs6000_expand_atomic_compare_and_swap (rtx operands[])
   if (mode != TImode && !reg_or_short_operand (oldval, mode))
     oldval = copy_to_mode_reg (mode, oldval);
 
+  if (reg_overlap_mentioned_p (retval, newval))
+    newval = copy_to_reg (newval);
+
   mem = rs6000_pre_atomic_barrier (mem, mod_s);
 
   label1 = NULL_RTX;