re PR rtl-optimization/69291 (wrong code at -O1 for…

re PR rtl-optimization/69291 (wrong code at -O1 for ruby-2.3.0/regcomp.c:985:compile_length_quantifier_node())

2016-02-11  Richard Biener  <rguenther@suse.de>

	PR rtl-optimization/69291
	* ifcvt.c (noce_try_store_flag_constants): Do not allow
	subexpressions affected by changing the result.

From-SVN: r233316

gcc/ChangeLog

+2016-02-11  Richard Biener  <rguenther@suse.de>
+
+	PR rtl-optimization/69291
+	* ifcvt.c (noce_try_store_flag_constants): Do not allow
+	subexpressions affected by changing the result.
+
 2016-02-10  Vladimir Makarov  <vmakarov@redhat.com>
 
 	PR target/69148

gcc/ifcvt.c

@@ -1274,7 +1274,10 @@ noce_try_store_flag_constants (struct noce_if_info *if_info)
       && CONST_INT_P (XEXP (a, 1))
       && CONST_INT_P (XEXP (b, 1))
       && rtx_equal_p (XEXP (a, 0), XEXP (b, 0))
-      && noce_operand_ok (XEXP (a, 0))
+      /* Allow expressions that are not using the result or plain
+         registers where we handle overlap below.  */
+      && (REG_P (XEXP (a, 0))
+	  || ! reg_overlap_mentioned_p (if_info->x, XEXP (a, 0)))
       && if_info->branch_cost >= 2)
     {
       common = XEXP (a, 0);