re PR tree-optimization/71947 (x ^ y not folded to 0 if x == y by DOM)

2016-07-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/71947
	* tree-vrp.c (extract_range_from_assert): Singleton symbolic
	ranges have useful limit_vr information.

	* gcc.dg/tree-ssa/vrp102.c: New testcase.

From-SVN: r238591

gcc/ChangeLog

 2016-07-21  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71947
+	* tree-vrp.c (extract_range_from_assert): Singleton symbolic
+	ranges have useful limit_vr information.
+
+2016-07-21  Richard Biener  <rguenther@suse.de>
+
 	* function-tests.c (build_trivial_generic_function): Set
 	BLOCK_SUPERCONTEXT of DECL_INITIAL.
 	* omp-low.c (create_omp_child_function): Likewise.

gcc/testsuite/ChangeLog

+2016-07-21  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/71947
+	* gcc.dg/tree-ssa/vrp102.c: New testcase.
+
 2016-07-21  Bin Cheng  <bin.cheng@arm.com>
 
 	* gcc.dg/tree-ssa/scev-15.c: New.

gcc/testsuite/gcc.dg/tree-ssa/vrp102.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-vrp1" } */
+
+int f(int x, int y)
+{ 
+  int ret; 
+  if (x == y)
+    ret = x ^ y;
+  else
+    ret = 1;
+
+  return ret;
+} 
+
+/* We should have computed x ^ y as zero and propagated the result into the
+   PHI feeding the result.  */
+
+/* { dg-final { scan-tree-dump "ret_\[0-9\]+ = PHI <\[01\]\\\(\[0-9\]+\\\), \[01\]\\\(\[0-9\]+\\\)>" "vrp1" } } */

gcc/tree-vrp.c

@@ -1513,10 +1513,13 @@ extract_range_from_assert (value_range *vr_p, tree expr)
   limit_vr = (TREE_CODE (limit) == SSA_NAME) ? get_value_range (limit) : NULL;
 
   /* LIMIT's range is only interesting if it has any useful information.  */
-  if (limit_vr
-      && (limit_vr->type == VR_UNDEFINED
-	  || limit_vr->type == VR_VARYING
-	  || symbolic_range_p (limit_vr)))
+  if (! limit_vr
+      || limit_vr->type == VR_UNDEFINED
+      || limit_vr->type == VR_VARYING
+      || (symbolic_range_p (limit_vr)
+	  && ! (limit_vr->type == VR_RANGE
+		&& (limit_vr->min == limit_vr->max
+		    || operand_equal_p (limit_vr->min, limit_vr->max, 0)))))
     limit_vr = NULL;
 
   /* Initially, the new range has the same set of equivalences of