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

#### 6.4.2.3 ARC Attributes ¶

These attributes are supported by the ARC back end:

`interrupt` ¶

  This attribute applies to functions.

  It indicates 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` for ARCv1 architecture, and `ilink` and `firq` for ARCv2 architecture.

`long_call` ¶
`medium_call`
`short_call`

  These attributes apply to functions.

  These attributes specify how a particular function is called. They 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.

`jli_always` ¶

  This attribute applies to functions.

  It forces the associated function to be called using a `jli` instruction. The `jli` instruction makes use of a table stored into `.jlitab` section, which holds the location of the functions which are addressed using this instruction.

`jli_fixed` ¶

  This attribute applies to functions.

  Identical to `jli_always` above, but the location of the function in the `jli` table is known and given as an attribute parameter.

`secure_call` ¶

  This attribute applies to functions.

  It allows you to mark secure-code functions that are callable from normal mode. The location of the secure call function into the `sjli` table needs to be passed as argument.

`aux` ¶

  This attribute applies to variables.

  The `aux` attribute is used to directly access the ARC’s auxiliary register space from C. The auxiliary register number is given via attribute argument.

`uncached` ¶

  This attribute applies to types.

  Declaring objects with the `uncached` type attribute allows you to exclude data-cache participation in load and store operations on those objects without involving the additional semantic implications of `volatile`. The `.di` instruction suffix is used for all loads and stores of data declared `uncached`.