[PATCH] Fix PR77479

[Richard Biener]

The following fixes PR77479.

Boosttrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2016-09-06  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/77479
        * tree-vrp.c (update_value_range): Extend overflow handling to
        VARYING.

        * gcc.dg/torture/pr77479.c: New testcase.

Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c      (revision 240004)
+++ gcc/tree-vrp.c      (working copy)
@@ -744,23 +745,29 @@ update_value_range (const_tree var, valu
       value_range_type rtype = get_range_info (var, &min, &max);
       if (rtype == VR_RANGE || rtype == VR_ANTI_RANGE)
        {
-         value_range nr;
-         nr.type = rtype;
+         tree nr_min, nr_max;
          /* Range info on SSA names doesn't carry overflow information
             so make sure to preserve the overflow bit on the lattice.  */
-         if (new_vr->type == VR_RANGE
-             && is_negative_overflow_infinity (new_vr->min)
-             && wi::eq_p (new_vr->min, min))
-           nr.min = new_vr->min;
-         else
-           nr.min = wide_int_to_tree (TREE_TYPE (var), min);
-         if (new_vr->type == VR_RANGE
-             && is_positive_overflow_infinity (new_vr->max)
-             && wi::eq_p (new_vr->max, max))
-           nr.max = new_vr->max;
-         else
-           nr.max = wide_int_to_tree (TREE_TYPE (var), max);
-         nr.equiv = NULL;
+         if (rtype == VR_RANGE
+             && needs_overflow_infinity (TREE_TYPE (var))
+             && (new_vr->type == VR_VARYING
+                 || (new_vr->type == VR_RANGE
+                     && is_negative_overflow_infinity (new_vr->min)))
+             && wi::eq_p (vrp_val_min (TREE_TYPE (var)), min))
+           nr_min = negative_overflow_infinity (TREE_TYPE (var));
+         else
+           nr_min = wide_int_to_tree (TREE_TYPE (var), min);
+         if (rtype == VR_RANGE
+             && needs_overflow_infinity (TREE_TYPE (var))
+             && (new_vr->type == VR_VARYING
+                 || (new_vr->type == VR_RANGE
+                     && is_positive_overflow_infinity (new_vr->max)))
+             && wi::eq_p (vrp_val_max (TREE_TYPE (var)), max))
+           nr_max = positive_overflow_infinity (TREE_TYPE (var));
+         else
+           nr_max = wide_int_to_tree (TREE_TYPE (var), max);
+         value_range nr = VR_INITIALIZER;
+         set_and_canonicalize_value_range (&nr, rtype, nr_min, nr_max, NULL);
          vrp_intersect_ranges (new_vr, &nr);
        }
     }
Index: gcc/testsuite/gcc.dg/torture/pr77479.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr77479.c      (revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr77479.c      (working copy)
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fstrict-overflow -ftree-vrp" } */
+
+void
+vr (int of, unsigned char bw)
+{
+  int d1;
+  int lm = 0;
+
+  for (d1 = 0; d1 < 3; ++d1)
+    {
+      const int vl = 2;
+
+      while (bw < vl)
+       {
+       }
+      if (bw != vl)
+       lm -= vl;
+    }
+  while (++of < 1)
+    {
+      lm /= bw;
+      of += lm;
+    }
+}