tree-vrp.c (extract_range_from_binary_expr): Don't shift by floor_log2 of zero.

* tree-vrp.c (extract_range_from_binary_expr): Don't shift by
floor_log2 of zero.  Negate widened zero.

From-SVN: r142702

gcc/ChangeLog

+2008-12-12  Alexandre Oliva  <aoliva@redhat.com>
+
+	* tree-vrp.c (extract_range_from_binary_expr): Don't shift by
+	floor_log2 of zero.  Negate widened zero.
+
 2008-12-12  Ben Elliston  <bje@au.ibm.com>
 
 	* config/fp-bit.c (nan): Rename from this ..

gcc/tree-vrp.c

@@ -2557,11 +2557,11 @@ extract_range_from_binary_expr (value_range_t *vr,
 	  ior_max.high = vr0_max.high | vr1_max.high;
 	  if (ior_max.high != 0)
 	    {
-	      ior_max.low = ~0u;
+	      ior_max.low = ~(unsigned HOST_WIDE_INT)0u;
 	      ior_max.high |= ((HOST_WIDE_INT) 1
 			       << floor_log2 (ior_max.high)) - 1;
 	    }
-	  else
+	  else if (ior_max.low != 0)
 	    ior_max.low |= ((unsigned HOST_WIDE_INT) 1u
 			    << floor_log2 (ior_max.low)) - 1;