gcc/doc/gcc/extensions-to-the-c-language-family/declaring-attributes-of-functions/risc-v-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 .. _risc-v-function-attributes:
   7
   8 RISC-V Function Attributes
   9 ^^^^^^^^^^^^^^^^^^^^^^^^^^
  10
  11 These function attributes are supported by the RISC-V back end:
  12
  13 .. index:: naked function attribute, RISC-V
  14
  15 .. risc-v-fn-attr:: naked
  16
  17   This attribute allows the compiler to construct the
  18   requisite function declaration, while allowing the body of the
  19   function to be assembly code. The specified function will not have
  20   prologue/epilogue sequences generated by the compiler. Only basic
  21   ``asm`` statements can safely be included in naked functions
  22   (see :ref:`basic-asm`). While using extended ``asm`` or a mixture of
  23   basic ``asm`` and C code may appear to work, they cannot be
  24   depended upon to work reliably and are not supported.
  25
  26 .. index:: interrupt function attribute, RISC-V
  27
  28 .. risc-v-fn-attr:: interrupt
  29
  30   Use this attribute to indicate that the specified function is an interrupt
  31   handler.  The compiler generates function entry and exit sequences suitable
  32   for use in an interrupt handler when this attribute is present.
  33
  34   You can specify the kind of interrupt to be handled by adding an optional
  35   parameter to the interrupt attribute like this:
  36
  37   .. code-block:: c++
  38
  39     void f (void) __attribute__ ((interrupt ("user")));
  40
  41   Permissible values for this parameter are ``user``, ``supervisor``,
  42   and ``machine``.  If there is no parameter, then it defaults to
  43   ``machine``.