gcc/doc/gcc/extensions-to-the-c-language-family/declaring-attributes-of-functions/rx-function-attributes.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 .. _rx-function-attributes:
   7
   8 RX Function Attributes
   9 ^^^^^^^^^^^^^^^^^^^^^^
  10
  11 These function attributes are supported by the RX back end:
  12
  13 .. index:: fast_interrupt function attribute, RX
  14
  15 .. rx-fn-attr:: fast_interrupt
  16
  17   Use this attribute on the RX port to indicate that the specified
  18   function is a fast interrupt handler.  This is just like the
  19   :rx-fn-attr:`interrupt` attribute, except that ``freit`` is used to return
  20   instead of ``reit``.
  21
  22 .. index:: interrupt function attribute, RX
  23
  24 .. rx-fn-attr:: interrupt
  25
  26   Use this attribute to indicate
  27   that the specified function is an interrupt handler.  The compiler generates
  28   function entry and exit sequences suitable for use in an interrupt handler
  29   when this attribute is present.
  30
  31   On RX and RL78 targets, you may specify one or more vector numbers as arguments
  32   to the attribute, as well as naming an alternate table name.
  33   Parameters are handled sequentially, so one handler can be assigned to
  34   multiple entries in multiple tables.  One may also pass the magic
  35   string ``"$default"`` which causes the function to be used for any
  36   unfilled slots in the current table.
  37
  38   This example shows a simple assignment of a function to one vector in
  39   the default table (note that preprocessor macros may be used for
  40   chip-specific symbolic vector names):
  41
  42   .. code-block:: c++
  43
  44     void __attribute__ ((interrupt (5))) txd1_handler ();
  45
  46   This example assigns a function to two slots in the default table
  47   (using preprocessor macros defined elsewhere) and makes it the default
  48   for the ``dct`` table:
  49
  50   .. code-block:: c++
  51
  52     void __attribute__ ((interrupt (RXD1_VECT,RXD2_VECT,"dct","$default")))
  53         txd1_handler ();
  54
  55 .. index:: naked function attribute, RX
  56
  57 .. rx-fn-attr:: naked
  58
  59   This attribute allows the compiler to construct the
  60   requisite function declaration, while allowing the body of the
  61   function to be assembly code. The specified function will not have
  62   prologue/epilogue sequences generated by the compiler. Only basic
  63   ``asm`` statements can safely be included in naked functions
  64   (see :ref:`basic-asm`). While using extended ``asm`` or a mixture of
  65   basic ``asm`` and C code may appear to work, they cannot be
  66   depended upon to work reliably and are not supported.
  67
  68 .. index:: vector function attribute, RX
  69
  70 .. rx-fn-attr:: vector
  71
  72   This RX attribute is similar to the :rx-fn-attr:`interrupt` attribute, including its
  73   parameters, but does not make the function an interrupt-handler type
  74   function (i.e. it retains the normal C function calling ABI).  See the
  75   :rx-fn-attr:`interrupt` attribute for a description of its arguments.