diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5fa424d81d5..5e775c31d16 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2007-06-06  Ian Lance Taylor  <iant@google.com>
+
+	* fold-const.c (merge_ranges): If range_successor or
+	range_predecessor fail, just return 0.
+
 2007-06-06  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR tree-optimization/32216
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index af48916601c..bc6d6022415 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -4549,13 +4549,24 @@ merge_ranges (int *pin_p, tree *plow, tree *phigh, int in0_p, tree low0,
 	{
 	  low = range_successor (high1);
 	  high = high0;
-	  in_p = (low != 0);
+	  in_p = 1;
+	  if (low == 0)
+	    {
+	      /* We are in the weird situation where high0 > high1 but
+		 high1 has no successor.  Punt.  */
+	      return 0;
+	    }
 	}
       else if (! subset || highequal)
 	{
 	  low = low0;
 	  high = range_predecessor (low1);
-	  in_p = (high != 0);
+	  in_p = 1;
+	  if (high == 0)
+	    {
+	      /* low0 < low1 but low1 has no predecessor.  Punt.  */
+	      return 0;
+	    }
 	}
       else
 	return 0;
@@ -4575,7 +4586,12 @@ merge_ranges (int *pin_p, tree *plow, tree *phigh, int in0_p, tree low0,
 	{
 	  low = range_successor (high0);
 	  high = high1;
-	  in_p = (low != 0);
+	  in_p = 1;
+	  if (low == 0)
+	    {
+	      /* high1 > high0 but high0 has no successor.  Punt.  */
+	      return 0;
+	    }
 	}
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 766369d5754..3917a8051eb 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2007-06-06  Ian Lance Taylor  <iant@google.com>
+
+	* g++.dg/conversion/enum1.C: New test.
+
 2007-06-06  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR tree-optimization/32216
diff --git a/gcc/testsuite/g++.dg/conversion/enum1.C b/gcc/testsuite/g++.dg/conversion/enum1.C
new file mode 100644
index 00000000000..6ea8cadb642
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conversion/enum1.C
@@ -0,0 +1,10 @@
+// { dg-do run }
+// { dg-options "-O2 -finline-functions" }
+
+enum E { V = 1 };
+static const E E_MIN = V;
+static const E E_MAX = V;
+
+bool valid(E v) { return v >= E_MIN && v <= E_MAX; }
+
+int main() { return valid(E(2)); }