re PR tree-optimization/69615 (0 to limit signed range checks don't always use unsigned compare)

	PR tree-optimization/69615
	* fold-const.c (merge_ranges): If range1 is - [x, x] and x is the
	maximum or minimum of the type, try to merge it also as if
	range1 is + [-, x - 1] or + [x + 1, -].

	* gcc.dg/pr69615.c: New test.

From-SVN: r261139

gcc/ChangeLog

 2018-06-04  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/69615
+	* fold-const.c (merge_ranges): If range1 is - [x, x] and x is the
+	maximum or minimum of the type, try to merge it also as if
+	range1 is + [-, x - 1] or + [x + 1, -].
+
 	PR c++/86025
 	* tree.c (inchash::add_expr): Handle IDENTIFIER_NODE.
 

gcc/fold-const.c

@@ -5084,6 +5084,29 @@ merge_ranges (int *pin_p, tree *plow, tree *phigh, int in0_p, tree low0,
       tem = high0, high0 = high1, high1 = tem;
     }
 
+  /* If the second range is != high1 where high1 is the type maximum of
+     the type, try first merging with < high1 range.  */
+  if (low1
+      && high1
+      && TREE_CODE (low1) == INTEGER_CST
+      && (TREE_CODE (TREE_TYPE (low1)) == INTEGER_TYPE
+	  || (TREE_CODE (TREE_TYPE (low1)) == ENUMERAL_TYPE
+	      && known_eq (TYPE_PRECISION (TREE_TYPE (low1)),
+			   GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (low1))))))
+      && operand_equal_p (low1, high1, 0))
+    {
+      if (tree_int_cst_equal (low1, TYPE_MAX_VALUE (TREE_TYPE (low1)))
+	  && merge_ranges (pin_p, plow, phigh, in0_p, low0, high0,
+			   !in1_p, NULL_TREE, range_predecessor (low1)))
+	return true;
+      /* Similarly for the second range != low1 where low1 is the type minimum
+	 of the type, try first merging with > low1 range.  */
+      if (tree_int_cst_equal (low1, TYPE_MIN_VALUE (TREE_TYPE (low1)))
+	  && merge_ranges (pin_p, plow, phigh, in0_p, low0, high0,
+			   !in1_p, range_successor (low1), NULL_TREE))
+	return true;
+    }
+
   /* Now flag two cases, whether the ranges are disjoint or whether the
      second range is totally subsumed in the first.  Note that the tests
      below are simplified by the ones above.  */

gcc/testsuite/ChangeLog

 2018-06-04  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/69615
+	* gcc.dg/pr69615.c: New test.
+
 	PR c++/86025
 	* c-c++-common/gomp/pr86025.c: New test.
 

gcc/testsuite/gcc.dg/pr69615.c

+/* PR tree-optimization/69615 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-not " >= 0" "optimized" } } */
+/* { dg-final { scan-tree-dump-not " < 0" "optimized" } } */
+/* { dg-final { scan-tree-dump-not " <= 23" "optimized" } } */
+/* { dg-final { scan-tree-dump-not " > 23" "optimized" } } */
+
+extern void foo (void);
+
+void
+f1 (int x)
+{
+  if (x >= 0 && x <= __INT_MAX__ - 1)
+    foo ();
+}
+
+void
+f2 (int x, int y)
+{
+  if (x >= 0 && y && x <= __INT_MAX__ - 1)
+    foo ();
+}
+
+void
+f3 (int x)
+{
+  if (x > -__INT_MAX__ - 1 && x <= 23)
+    foo ();
+}
+
+void
+f4 (int x, int y)
+{
+  if (x > -__INT_MAX__ - 1 && y && x <= 23)
+    foo ();
+}