stor-layout.c (layout_type): Do upper - lower in the native type, so as to…

stor-layout.c (layout_type): Do upper - lower in the native type, so as to properly handle negative indices.

        * stor-layout.c (layout_type): Do upper - lower in the native type,
        so as to properly handle negative indices.

From-SVN: r17846

gcc/ChangeLog

+Wed Feb 11 01:44:13 1998  Richard Henderson  <rth@cygnus.com>
+
+	* stor-layout.c (layout_type): Do upper - lower in the native type,
+	so as to properly handle negative indices.
+
 Wed Feb 11 01:35:55 1998  Robert Lipe   <robertl@dgii.com>
 
 	* except.c (start_dynamic_cleanup): Remove unused variable 'dhc'.

gcc/stor-layout.c

@@ -786,8 +786,11 @@ layout_type (type)
 					 lb, 0))
 	      ub = TREE_OPERAND (ub, 0);
 
+	    /* The initial subtraction should happen in the original type so
+	       that (possible) negative values are handled appropriately.  */
 	    length = size_binop (PLUS_EXPR, size_one_node,
-				 size_binop (MINUS_EXPR, ub, lb));
+				 fold (build (MINUS_EXPR, TREE_TYPE (lb),
+					      ub, lb)));
 
 	    /* If neither bound is a constant and sizetype is signed, make
 	       sure the size is never negative.  We should really do this