re PR target/14547 (Passing _Complex long double does not follow the ABI)

        PR target/14547
        * target.h (struct gcc_target): Move calls substructure before
        booleans.  Add split_complex_arg.
        * function.c (assign_parms, split_complex_args): Use it.
        * calls.c (expand_call): Likewise.
        (split_complex_values): Likewise.  Check for splittable types
        before allocating memory.
        (split_complex_types): Likewise.
        * system.h (SPLIT_COMPLEX_ARGS): Poison.
        * expr.h (SPLIT_COMPLEX_ARGS): Remove.
        * target-def.h (TARGET_SPLIT_COMPLEX_ARG): New.
        * config/alpha/alpha.c (alpha_split_complex_arg): New.
        (TARGET_SPLIT_COMPLEX_ARG): New.
        * config/alpha/alpha.h (SPLIT_COMPLEX_ARGS): Remove.
        * config/rs6000/rs6000.c (TARGET_SPLIT_COMPLEX_ARG): New.
        (rs6000_override_options): Zap it for non-AIX.
        (rs6000_function_value): Use targetm.calls.split_complex_arg.
        * config/rs6000/rs6000.h (SPLIT_COMPLEX_ARGS): Remove.
        * config/xtensa/xtensa.c (TARGET_SPLIT_COMPLEX_ARG): New.
        * config/xtensa/xtensa.h (SPLIT_COMPLEX_ARGS): Remove.
        * doc/tm.texi (TARGET_SPLIT_COMPLEX_ARG): Modify from old
        SPLIT_COMPLEX_ARGS entry.

From-SVN: r79376