re PR tree-optimization/78788 (ICE (segfault) on s390x-linux-gnu)

2016-12-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/78788
	* tree-vrp.c (set_value_range): Allow [-INF(OVF), +INF(OVF)].
	(set_and_canonicalize_value_range): Do not drop the above to
	VARYING.

	* gcc.dg/torture/pr78788.c: New testcase.

From-SVN: r243631

gcc/ChangeLog

+2016-12-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78788
+	* tree-vrp.c (set_value_range): Allow [-INF(OVF), +INF(OVF)].
+	(set_and_canonicalize_value_range): Do not drop the above to
+	VARYING.
+
 2016-12-13  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
 
 	* config/rs6000/rs600.c (rs6000_builtin_vectorization_cost):

gcc/testsuite/ChangeLog

+2016-12-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78788
+	* gcc.dg/torture/pr78788.c: New testcase.
+
 2016-12-13  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/69481

gcc/testsuite/gcc.dg/torture/pr78788.c

+/* { dg-do compile } */
+
+int a;
+long b;
+long c;
+void d()
+{
+  int e = 0;
+  for (; b; b++)
+    if (c)
+      {
+	e++;
+	e++;
+      }
+  while (e)
+    a = e -= 2;
+}

gcc/tree-vrp.c

@@ -365,10 +365,6 @@ set_value_range (value_range *vr, enum value_range_type t, tree min,
 
       cmp = compare_values (min, max);
       gcc_assert (cmp == 0 || cmp == -1 || cmp == -2);
-
-      if (needs_overflow_infinity (TREE_TYPE (min)))
-	gcc_assert (!is_overflow_infinity (min)
-		    || !is_overflow_infinity (max));
     }
 
   if (flag_checking
@@ -506,14 +502,9 @@ set_and_canonicalize_value_range (value_range *vr, enum value_range_type t,
         }
     }
 
-  /* Drop [-INF(OVF), +INF(OVF)] to varying.  */
-  if (needs_overflow_infinity (TREE_TYPE (min))
-      && is_overflow_infinity (min)
-      && is_overflow_infinity (max))
-    {
-      set_value_range_to_varying (vr);
-      return;
-    }
+  /* Do not drop [-INF(OVF), +INF(OVF)] to varying.  (OVF) has to be sticky
+     to make sure VRP iteration terminates, otherwise we can get into
+     oscillations.  */
 
   set_value_range (vr, t, min, max, equiv);
 }