gcc/doc/gcc/gcc-command-options/machine-dependent-options/rl78-options.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. program:: RL78
   7
   8 .. index:: RL78 Options
   9
  10 .. _rl78-options:
  11
  12 RL78 Options
  13 ^^^^^^^^^^^^
  14
  15 .. option:: -msim
  16
  17   Links in additional target libraries to support operation within a
  18   simulator.
  19
  20 .. option:: -mmul=none
  21
  22   Specifies the type of hardware multiplication and division support to
  23   be used.  The simplest is ``none``, which uses software for both
  24   multiplication and division.  This is the default.  The ``g13``
  25   value is for the hardware multiply/divide peripheral found on the
  26   RL78/G13 (S2 core) targets.  The ``g14`` value selects the use of
  27   the multiplication and division instructions supported by the RL78/G14
  28   (S3 core) parts.  The value ``rl78`` is an alias for ``g14`` and
  29   the value ``mg10`` is an alias for ``none``.
  30
  31   In addition a C preprocessor macro is defined, based upon the setting
  32   of this option.  Possible values are: ``__RL78_MUL_NONE__``,
  33   ``__RL78_MUL_G13__`` or ``__RL78_MUL_G14__``.
  34
  35 .. option:: -mcpu=g10
  36
  37   Specifies the RL78 core to target.  The default is the G14 core, also
  38   known as an S3 core or just RL78.  The G13 or S2 core does not have
  39   multiply or divide instructions, instead it uses a hardware peripheral
  40   for these operations.  The G10 or S1 core does not have register
  41   banks, so it uses a different calling convention.
  42
  43   If this option is set it also selects the type of hardware multiply
  44   support to use, unless this is overridden by an explicit
  45   :option:`-mmul=none` option on the command line.  Thus specifying
  46   :option:`-mcpu=g13` enables the use of the G13 hardware multiply
  47   peripheral and specifying :option:`-mcpu=g10` disables the use of
  48   hardware multiplications altogether.
  49
  50   Note, although the RL78/G14 core is the default target, specifying
  51   :option:`-mcpu=g14` or :option:`-mcpu=rl78` on the command line does
  52   change the behavior of the toolchain since it also enables G14
  53   hardware multiply support.  If these options are not specified on the
  54   command line then software multiplication routines will be used even
  55   though the code targets the RL78 core.  This is for backwards
  56   compatibility with older toolchains which did not have hardware
  57   multiply and divide support.
  58
  59   In addition a C preprocessor macro is defined, based upon the setting
  60   of this option.  Possible values are: ``__RL78_G10__``,
  61   ``__RL78_G13__`` or ``__RL78_G14__``.
  62
  63 .. option:: -mg10, -mg13, -mg14, -mrl78
  64
  65   These are aliases for the corresponding :option:`-mcpu=` option.  They
  66   are provided for backwards compatibility.
  67
  68 .. option:: -mallregs
  69
  70   Allow the compiler to use all of the available registers.  By default
  71   registers ``r24..r31`` are reserved for use in interrupt handlers.
  72   With this option enabled these registers can be used in ordinary
  73   functions as well.
  74
  75 .. option:: -m64bit-doubles, -m32bit-doubles
  76
  77   Make the ``double`` data type be 64 bits (:option:`-m64bit-doubles`)
  78   or 32 bits (:option:`-m32bit-doubles`) in size.  The default is
  79   :option:`-m32bit-doubles`.
  80
  81 .. option:: -msave-mduc-in-interrupts, -mno-save-mduc-in-interrupts
  82
  83   Specifies that interrupt handler functions should preserve the
  84   MDUC registers.  This is only necessary if normal code might use
  85   the MDUC registers, for example because it performs multiplication
  86   and division operations.  The default is to ignore the MDUC registers
  87   as this makes the interrupt handlers faster.  The target option -mg13
  88   needs to be passed for this to work as this feature is only available
  89   on the G13 target (S2 core).  The MDUC registers will only be saved
  90   if the interrupt handler performs a multiplication or division
  91   operation or it calls another function.