[Patch] PR68137, drop constant overflow flag in adjust_range_with_scev when possible

[Jiong Wang <jiong dot wang at foss dot arm dot com>]

As reported by pr68137 and pr68326, r230150 caused new issues.

Those ICEs are caused by adjust_range_with_scev getting range with
overflowed constants min or max. So given there are too many places to
generate OVF, we do a check in adjust_range_with_scev, to drop OVF flag
when it's uncessary. This should fix the OVF side-effect caused by
r230150.

A simple regression testcase is included in this patch.

bootstrap OK on x86-64 and aarch64, regression ok on both.

For more background, please see discussion at

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68317

OK for trunk?

2015-11-23  Richard Biener  <rguenth@gcc.gnu.com>
            Jiong Wang  <jiong.wang@arm.com>

gcc/
  PR tree-optimization/68137
  PR tree-optimization/68326
  * tree-vrp.c (adjust_range_with_scev): Call drop_tree_overflow if the
  final min and max are not infinity.

gcc/testsuite/
  * gcc.dg/pr68139.c: New testcase.

--
Regards,
Jiong

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index e2393e4..8efeb76 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -4331,6 +4331,17 @@ adjust_range_with_scev (value_range *vr, struct loop *loop,
 	  && is_positive_overflow_infinity (max)))
     return;
 
+  /* Even for valid range info, sometimes overflow flag will leak in.
+     As GIMPLE IL should have no constants with TREE_OVERFLOW set, we
+     drop them except for +-overflow_infinity which still need special
+     handling in vrp pass.  */
+  if (TREE_OVERFLOW_P (min)
+      && ! is_negative_overflow_infinity (min))
+    min = drop_tree_overflow (min);
+  if (TREE_OVERFLOW_P (max)
+      && ! is_positive_overflow_infinity (max))
+    max = drop_tree_overflow (max);
+
   set_value_range (vr, VR_RANGE, min, max, vr->equiv);
 }
 
diff --git a/gcc/testsuite/gcc.dg/pr68137.c b/gcc/testsuite/gcc.dg/pr68137.c
new file mode 100644
index 0000000..a30e1ac
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr68137.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void bar (int);
+
+void
+foo ()
+{
+ int index = 0;
+ for (index; index <= 10; index--)
+   /* Result of the following multiply will overflow
+      when converted to signed int.  */
+   bar((0xcafe + index) * 0xdead);
+}