Use gen_int_mode in expand_builtin_memset_args

[Richard Sandiford]

This patch fixes a case where expand_builtin_memset_args was creating
a zero- rather than sign-extended character-sized CONST_INT.  The problem
showed up on s390, where a character was being passed as (const_int 171)
rather than (const_int -85).

Tested on x86_64-linux-gnu.  Andreas also confirms that it fixes
the s390 failure.  OK to install?

Richard


gcc/
        * builtins.c (expand_builtin_memset_args): Use gen_int_mode
        instead of GEN_INT.

Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c      2011-03-24 15:13:39.000000000 +0000
+++ gcc/builtins.c      2011-03-28 13:56:31.000000000 +0100
@@ -3935,6 +3935,7 @@ expand_builtin_memset_args (tree dest, t
 {
   tree fndecl, fn;
   enum built_in_function fcode;
+  enum machine_mode val_mode;
   char c;
   unsigned int dest_align;
   rtx dest_mem, dest_addr, len_rtx;
@@ -3969,14 +3970,14 @@ expand_builtin_memset_args (tree dest, t
 
   len_rtx = expand_normal (len);
   dest_mem = get_memory_rtx (dest, len);
+  val_mode = TYPE_MODE (unsigned_char_type_node);
 
   if (TREE_CODE (val) != INTEGER_CST)
     {
       rtx val_rtx;
 
       val_rtx = expand_normal (val);
-      val_rtx = convert_to_mode (TYPE_MODE (unsigned_char_type_node),
-                                val_rtx, 0);
+      val_rtx = convert_to_mode (val_mode, val_rtx, 0);
 
       /* Assume that we can memset by pieces if we can store
        * the coefficients by pieces (in the required modes).
@@ -3987,8 +3988,7 @@ expand_builtin_memset_args (tree dest, t
                                  builtin_memset_read_str, &c, dest_align,
                                  true))
        {
-         val_rtx = force_reg (TYPE_MODE (unsigned_char_type_node),
-                              val_rtx);
+         val_rtx = force_reg (val_mode, val_rtx);
          store_by_pieces (dest_mem, tree_low_cst (len, 1),
                           builtin_memset_gen_str, val_rtx, dest_align,
                           true, 0);
@@ -4014,7 +4014,8 @@ expand_builtin_memset_args (tree dest, t
                                  true))
        store_by_pieces (dest_mem, tree_low_cst (len, 1),
                         builtin_memset_read_str, &c, dest_align, true, 0);
-      else if (!set_storage_via_setmem (dest_mem, len_rtx, GEN_INT (c),
+      else if (!set_storage_via_setmem (dest_mem, len_rtx,
+                                       gen_int_mode (c, val_mode),
                                        dest_align, expected_align,
                                        expected_size))
        goto do_libcall;