optabs.c (expand_binop): When synthesizing double word rotates from single word shifts...

        * optabs.c (expand_binop): When synthesizing double word rotates
        from single word shifts, use a new register target if the provided
        target is not a REG already.

From-SVN: r79875

gcc/ChangeLog

+2004-03-23  Olivier Hainque  <hainque@act-europe.fr>
+
+        * optabs.c (expand_binop): When synthesizing double word rotates
+        from single word shifts, use a new register target if the provided
+        target is not a REG already.
+
 2004-03-23  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 
 	* alias.c (get_alias_set): Add support for TYPE_REF_CAN_ALIAS_ALL.

gcc/optabs.c

@@ -1087,8 +1087,12 @@ expand_binop (enum machine_mode mode, optab binoptab, rtx op0, rtx op1,
       int shift_count, left_shift, outof_word;
 
       /* If TARGET is the same as one of the operands, the REG_EQUAL note
-	 won't be accurate, so use a new target.  */
-      if (target == 0 || target == op0 || target == op1)
+	 won't be accurate, so use a new target. Do this also if target is not
+	 a REG, first because having a register instead may open optimization
+	 oportunities, and second because if target and op0 happen to be MEMs
+	 designating the same location, we would risk clobbering it too early
+	 in the code sequence we generate below.  */
+      if (target == 0 || target == op0 || target == op1 || ! REG_P (target))
 	target = gen_reg_rtx (mode);
 
       start_sequence ();