From: Bernd Schmidt <bernds@redhat.co.uk>
Date: Thu, 30 Nov 2000 11:53:40 +0000 (+0000)
Subject: Backport a change to the 2.95 branch
X-Git-Tag: prereleases/gcc-2.95.3-test1~57
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62610d6f57cb2e799f56ec2ea5876ba540b84805;p=thirdparty%2Fgcc.git

Backport a change to the 2.95 branch

From-SVN: r37876
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8cfa93c8921a..790e3575d1c3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2000-11-30  Bernd Schmidt  <bernds@redhat.co.uk>
 
+	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
+
 	2000-07-15  Michael Meissner  <meissner@redhat.com>
 	* fold-const.c (fold): When optimizing FOO++ == CONST into ++FOO
 	== CONST + INCREMENT, don't overwrite the tree node for FOO++,
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 2d4f907aa8cd..f260ab4b5004 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -3259,8 +3259,17 @@ 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;