[Bug middle-end/28161] Wrong bit field layout with -mms-bitfields

[kkojima at gcc dot gnu dot org]

------- Comment #3 from kkojima at gcc dot gnu dot org  2006-06-26 23:10 -------
GDB says that TREE_TYPE of a.d is the 32-bit integer and its
DECL_BIT_FIELD_TYPE is 64-bit when place_field processes a.e.
place_field uses the size of TREE_TYPE of the previous bit filed
when deciding whether a bit field to be packed with the previous
one or not.  It seems that this makes the ms-bitfiled code
confused.  The appended patch is to make place_field use
DECL_BIT_FIELD_TYPE of the previous bit field instead of
TREE_TYPE when comparing the size of consecutive bit fields.
It works for the above testcase, though the thorough tests are
needed.

--- ORIG/trunk/gcc/stor-layout.c        2006-06-13 09:06:36.000000000 +0900
+++ LOCAL/trunk/gcc/stor-layout.c       2006-06-26 16:44:31.000000000 +0900
@@ -1022,6 +1022,7 @@ place_field (record_layout_info rli, tre
   if (targetm.ms_bitfield_layout_p (rli->t))
     {
       tree prev_saved = rli->prev_field;
+      tree prev_type = prev_saved ? DECL_BIT_FIELD_TYPE (prev_saved) : NULL;

       /* This is a bitfield if it exists.  */
       if (rli->prev_field)
@@ -1037,8 +1038,7 @@ place_field (record_layout_info rli, tre
              && !integer_zerop (DECL_SIZE (rli->prev_field))
              && host_integerp (DECL_SIZE (rli->prev_field), 0)
              && host_integerp (TYPE_SIZE (type), 0)
-             && simple_cst_equal (TYPE_SIZE (type),
-                                  TYPE_SIZE (TREE_TYPE (rli->prev_field))))
+             && simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type)))
            {
              /* We're in the middle of a run of equal type size fields; make
                 sure we realign if we run out of bits.  (Not decl size,
@@ -1105,8 +1108,7 @@ place_field (record_layout_info rli, tre

       if (!DECL_BIT_FIELD_TYPE (field)
          || (prev_saved != NULL
-             ? !simple_cst_equal (TYPE_SIZE (type),
-                                  TYPE_SIZE (TREE_TYPE (prev_saved)))
+             ? !simple_cst_equal (TYPE_SIZE (type), TYPE_SIZE (prev_type))
              : !integer_zerop (DECL_SIZE (field)) ))
        {
          /* Never smaller than a byte for compatibility.  */


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28161