* function.c (diddle_return_value): Rework to use a callback function.

    * function.c (diddle_return_value): Rework to use a callback function.
        Use current_function_return_rtx if it's been set up.
        (do_clobber_return_reg, clobber_return_register): New.
        (do_use_return_reg, use_return_register): New.
        (expand_function_end): Use them.
        * stmt.c (expand_null_return): Likewise.
        * function.h: Declare them.
        * flow.c (mark_regs_live_at_end): Use diddle_return_value.
        (mark_reg): Change arguments as appropriate for callback.
        * integrate.c (expand_inline_function): Revert 19 Jan change.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@31791 138bc75d-0d04-0410-961f-82ee72b054a4