[backport gcc-4.8/trunk r193591, also fixes PR55883 <mikpe@it.uu.se>]

gcc/

2012-11-17  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/55236
	* fold-const.c (make_range_step) <case NEGATE_EXPR>: For -fwrapv
	and signed ARG0_TYPE, force low and high to be non-NULL.

gcc/testsuite/

2012-11-17  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/55236
	* gcc.dg/pr55236.c: New test.

--- gcc-4.7.2/gcc/fold-const.c.~1~	2012-06-01 19:03:19.000000000 +0200
+++ gcc-4.7.2/gcc/fold-const.c	2013-01-05 20:43:46.000000000 +0100
@@ -3904,6 +3904,17 @@ make_range_step (location_t loc, enum tr
       return arg0;
 
     case NEGATE_EXPR:
+      /* If flag_wrapv and ARG0_TYPE is signed, make sure
+	 low and high are non-NULL, then normalize will DTRT.  */
+      if (!TYPE_UNSIGNED (arg0_type)
+	  && !TYPE_OVERFLOW_UNDEFINED (arg0_type))
+	{
+	  if (low == NULL_TREE)
+	    low = TYPE_MIN_VALUE (arg0_type);
+	  if (high == NULL_TREE)
+	    high = TYPE_MAX_VALUE (arg0_type);
+	}
+
       /* (-x) IN [a,b] -> x in [-b, -a]  */
       n_low = range_binop (MINUS_EXPR, exp_type,
 			   build_int_cst (exp_type, 0),
--- gcc-4.7.2/gcc/testsuite/gcc.dg/pr55236.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.7.2/gcc/testsuite/gcc.dg/pr55236.c	2013-01-05 20:43:46.000000000 +0100
@@ -0,0 +1,31 @@
+/* PR tree-optimization/55236 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fwrapv" } */
+
+extern void abort ();
+
+__attribute__((noinline, noclone)) void
+foo (int i)
+{
+  if (i > 0)
+    abort ();
+  i = -i;
+  if (i < 0)
+    return;
+  abort ();
+}
+
+__attribute__((noinline, noclone)) void
+bar (int i)
+{
+  if (i > 0 || (-i) >= 0)
+    abort ();
+}
+
+int
+main ()
+{
+  foo (-__INT_MAX__ - 1);
+  bar (-__INT_MAX__ - 1);
+  return 0;
+}