* regrename.c (copyprop_hardreg_forward): New optimization.
        (kill_value_regno, kill_value, init_value_data, kill_clobbered_value,
        kill_set_value, kill_autoinc_value, copy_value, find_oldest_value_reg,
        replace_oldest_value_reg, replace_oldest_value_addr,
        replace_oldest_value_mem, copyprop_hardreg_forward_1,
        debug_value_data, validate_value_data): New.
        * rtl.h (copyprop_hardreg_forward): Declare.
        * toplev.c (flag_cprop_registers): New.
        (f_options): Add -fcprop-registers
        (rest_of_compilation): Invoke it.
        (parse_options_and_default_flags): Set it at -O1.
        * doc/invoke.texi: Document it.

From-SVN: r47951