[LIB]: Reorganize struct tag

Erm, eating my dog food now that I have access to a 64bit machine here at home:

[acme@mica pahole]$ pahole build/libdwarves.so.1.0.0 tag
/* <b7e> /home/acme/git/pahole/dwarves.h:48 */
struct tag {
        struct list_head      node;          /*     0    16 */
        Dwarf_Off             type;          /*    16     8 */
        Dwarf_Off             id;            /*    24     8 */
        uint16_t              tag;           /*    32     2 */
        uint16_t              decl_line;     /*    34     2 */

        /* XXX 4 bytes hole, try to pack */

        const char  *         decl_file;     /*    40     8 */
        uint32_t              refcnt;        /*    48     4 */
}; /* size: 56, cachelines: 1 */
   /* sum members: 48, holes: 1, sum holes: 4 */
   /* padding: 4 */
   /* last cacheline: 56 bytes */
[acme@mica pahole]$

[acme@mica pahole]$ pahole --reorganize build/libdwarves.so.1.0.0 tag
/* <b7e> /home/acme/git/pahole/dwarves.h:48 */
struct tag {
        struct list_head      node;          /*     0    16 */
        Dwarf_Off             type;          /*    16     8 */
        Dwarf_Off             id;            /*    24     8 */
        uint16_t              tag;           /*    32     2 */
        uint16_t              decl_line;     /*    34     2 */
        uint32_t              refcnt;        /*    36     4 */
        const char  *         decl_file;     /*    40     8 */
}; /* size: 48, cachelines: 1 */
   /* last cacheline: 48 bytes */
   /* saved 8 bytes! */
[acme@mica pahole]$

[acme@mica pahole]$ codiff build/libdwarves.so.1.0.0.before build/libdwarves.so.1.0.0
/home/acme/git/pahole/dwarves.c:
  struct tag              |   -8
  struct type             |   -8
  struct class            |   -8
  struct base_type        |   -8
  struct array_type       |   -8
  struct class_member     |   -8
  struct lexblock         |   -8
  struct ftype            |   -8
  struct function         |  -16
  struct parameter        |   -8
  struct variable         |   -8
  struct inline_expansion |   -8
  struct label            |   -8
  struct enumerator       |   -8
 14 structs changed
  class_member__clone     |   -8
  class__clone            |   -8
 2 functions changed, 16 bytes removed
[acme@mica pahole]$

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

dwarves.h

@@ -49,9 +49,9 @@ struct tag {
 	struct list_head node;
 	Dwarf_Off	 type;
 	Dwarf_Off	 id;
-	uint16_t	 tag;
-	uint16_t	 decl_line;
 	const char	 *decl_file;
+	uint16_t	 decl_line;
+	uint16_t	 tag;
 	uint32_t	 refcnt;
 };