re PR tree-optimization/80788 (ICE in set_value_range, at tree-vrp.c:252)

	PR tree-optimization/80788
	* match.pd (X +- C1 CMP C2 -> X CMP C2 -+ C1): If res
	has TREE_OVERFLOW set, call drop_tree_overflow.

	* gcc.dg/pr80788.c: New test.

From-SVN: r255191

gcc/ChangeLog

+2017-11-28  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/80788
+	* match.pd (X +- C1 CMP C2 -> X CMP C2 -+ C1): If res
+	has TREE_OVERFLOW set, call drop_tree_overflow.
+
 2017-11-28  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/83158

gcc/match.pd

@@ -4393,7 +4393,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	  && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
       { constant_boolean_node (cmp == NE_EXPR, type); }
       (if (single_use (@3))
-       (cmp @0 { res; }))))))))
+       (cmp @0 { TREE_OVERFLOW (res)
+		 ? drop_tree_overflow (res) : res; }))))))))
 (for cmp (lt le gt ge)
  (for op (plus minus)
       rop (minus plus)

gcc/testsuite/ChangeLog

+2017-11-28  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/80788
+	* gcc.dg/pr80788.c: New test.
+
 2017-11-27  Martin Sebor  <msebor@redhat.com>
 
 	PR c++/83058

gcc/testsuite/gcc.dg/pr80788.c

+/* PR tree-optimization/80788 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fwrapv" } */
+
+void
+foo (signed char x)
+{
+  signed char a = (x + 1) ^ 128;
+  x &= !!a;
+  if (x != 0)
+    for (;;)
+      ;
+}