* Makefile.in: Add $(TARGET_H) to the regrename.o rule.
        * regrename.c (struct du_head): Add new element length.
        (sort_du_head, get_element, merge, merge_sort_comparison):
        New functions of merge sort implementation to du_head list.
        (regrename_optimize): Sort du_head linked list by length.
        Iterate registers in a preferred-register-first order.
        Move some code to ...
        (check_new_reg_p): here.  New function.
        (create_new_chain):  Initialize length.
        (scan_rtx_reg): Increase length for non-debug insns.
        * target.def: New hook preferred_rename_class.
        * targhook.c (default_preferred_rename_class): New.
        * targhook.h: Declare it.
        * doc/tm.texi.in: New hook TARGET_PREFERRED_RENAME_CLASS.
        * doc/tm.texi: Regenerate.

From-SVN: r167534