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

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6.31.8 Epiphany Function Attributes

These function attributes are supported by the Epiphany back end:

disinterrupt

This attribute causes the compiler to emit instructions to disable interrupts for the duration of the given function.

forwarder_section

This attribute modifies the behavior of an interrupt handler. The interrupt handler may be in external memory which cannot be reached by a branch instruction, so generate a local memory trampoline to transfer control. The single parameter identifies the section where the trampoline is placed.

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. It may also generate a special section with code to initialize the interrupt vector table.

On Epiphany targets one or more optional parameters can be added like this:

void __attribute__ ((interrupt ("dma0, dma1"))) universal_dma_handler ();

Permissible values for these parameters are: reset , software_exception , page_miss , timer0 , timer1 , message , dma0 , dma1 , wand and swi . Multiple parameters indicate that multiple entries in the interrupt vector table should be initialized for this function, i.e. for each parameter name , a jump to the function is emitted in the section ivt_entry_ name . The parameter(s) may be omitted entirely, in which case no interrupt vector table entry is provided.

Note that interrupts are enabled inside the function unless the disinterrupt attribute is also specified.

The following examples are all valid uses of these attributes on Epiphany targets:

void __attribute__ ((interrupt)) universal_handler ();
void __attribute__ ((interrupt ("dma1"))) dma1_handler ();
void __attribute__ ((interrupt ("dma0, dma1"))) 
  universal_dma_handler ();
void __attribute__ ((interrupt ("timer0"), disinterrupt))
  fast_timer_handler ();
void __attribute__ ((interrupt ("dma0, dma1"), 
                     forwarder_section ("tramp")))
  external_dma_handler ();

long_call

short_call

These attributes specify how a particular function is called. These attributes override the -mlong-calls (see Adapteva Epiphany Options) command-line switch and #pragma long_calls settings.

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