[ARC] Add support for reduced register file set

[ARC] Add support for reduced register file set

gcc/
2018-01-26  Claudiu Zissulescu  <claziss@synopsys.com>

        * config/arc/arc-arches.def: Option mrf16 valid for all
        architectures.
        * config/arc/arc-c.def (__ARC_RF16__): New predefined macro.
        * config/arc/arc-cpus.def (em_mini): New cpu with rf16 on.
        * config/arc/arc-options.def (FL_RF16): Add mrf16 option.
        * config/arc/arc-tables.opt: Regenerate.
        * config/arc/arc.c (arc_conditional_register_usage): Handle
        reduced register file case.
        (arc_file_start): Set must have build attributes.
        * config/arc/arc.h (MAX_ARC_PARM_REGS): Conditional define using
        mrf16 option value.
        * config/arc/arc.opt (mrf16): Add new option.
        * config/arc/elf.h (ATTRIBUTE_PCS): Define.
        * config/arc/genmultilib.awk: Handle new mrf16 option.
        * config/arc/linux.h (ATTRIBUTE_PCS): Define.
        * config/arc/t-multilib: Regenerate.
        * doc/invoke.texi (ARC Options): Document mrf16 option.

libgcc/
2018-01-26  Claudiu Zissulescu  <claziss@synopsys.com>

        * config/arc/lib1funcs.S (__udivmodsi4): Use safe version for RF16
        option.
        (__divsi3): Use RF16 safe registers.
        (__modsi3): Likewise.

From-SVN: r257083