Using the GNU Compiler Collection (GCC): ARC Function Attributes

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#### 6.31.3 ARC Function Attributes

These function attributes are supported by the ARC back end:

`interrupt`

  Use this attribute to indicate that the specified function is an interrupt handler. The compiler generates function entry and exit sequences suitable for use in an interrupt handler when this attribute is present.

  On the ARC, you must specify the kind of interrupt to be handled in a parameter to the interrupt attribute like this:

      void f () __attribute__ ((interrupt ("ilink1")));

  Permissible values for this parameter are: `ilink1` and `ilink2`.

`long_call`
`medium_call`
`short_call`

  These attributes specify how a particular function is called. These attributes override the `-mlong-calls` and `-mmedium-calls` (see ARC Options) command-line switches and `#pragma long_calls` settings.

  For ARC, a function marked with the `long_call` attribute is always called using register-indirect jump-and-link instructions, thereby enabling the called function to be placed anywhere within the 32-bit address space. A function marked with the `medium_call` attribute will always be close enough to be called with an unconditional branch-and-link instruction, which has a 25-bit offset from the call site. A function marked with the `short_call` attribute will always be close enough to be called with a conditional branch-and-link instruction, which has a 21-bit offset from the call site.