fold-const.c (make_range): Handle degenerated intervals.

* fold-const.c (make_range): Handle degenerated intervals.
Fixes c-torture/execute/991221-1.c

From-SVN: r34045

gcc/ChangeLog

+Sat May 20 07:27:35 2000  Alexandre Oliva  <aoliva@cygnus.com>
+
+	* fold-const.c (make_range): Handle degenerated intervals.
+	Fixes c-torture/execute/991221-1.c
+
 Fri May 19 18:16:31 2000  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 
 	* cse.c (cse_basic_block): Only call find_reg_note if REG_NOTES not 0.

gcc/fold-const.c

@@ -3455,8 +3455,17 @@ make_range (exp, pin_p, plow, phigh)
 	      low = range_binop (PLUS_EXPR, type, n_high, 0,
 				 integer_one_node, 0);
 	      high = range_binop (MINUS_EXPR, type, n_low, 0,
-				 integer_one_node, 0);
-	      in_p = ! in_p;
+				  integer_one_node, 0);
+
+	      /* If the range is of the form +/- [ x+1, x ], we won't
+		 be able to normalize it.  But then, it represents the
+		 whole range or the empty set, so make it
+		 +/- [ -, - ].  */
+	      if (tree_int_cst_equal (n_low, low)
+		  && tree_int_cst_equal (n_high, high))
+		low = high = 0;
+	      else
+		in_p = ! in_p;
 	    }
 	  else
 	    low = n_low, high = n_high;