--- gcc/builtins.c.jj	2010-08-12 14:07:37.000000000 +0200
+++ gcc/builtins.c	2010-08-12 14:41:39.740220087 +0200
@@ -8399,7 +8399,7 @@ fold_builtin_memory_op (location_t loc, 
 	  if (readonly_data_expr (src)
 	      || (host_integerp (len, 1)
 		  && (MIN (src_align, dest_align) / BITS_PER_UNIT
-		      >= tree_low_cst (len, 1))))
+		      >= (unsigned HOST_WIDE_INT) tree_low_cst (len, 1))))
 	    {
 	      tree fn = implicit_built_in_decls[BUILT_IN_MEMCPY];
 	      if (!fn)