[LLVMdev] LLVM and Interrupt Service Routines.

[Chris Lattner]

On Jul 24, 2009, at 8:47 AM, Jakob Stoklund Olesen wrote:

> Duncan Sands <baldrick at free.fr> writes:
>
>> the interrupt handler itself is a parameterless procedure that does  
>> not
>> return a value.  As such, I guess calling conventions and so forth  
>> are
>> not very relevant for it :)  In any case llvm-gcc and gcc mainline  
>> seem
>> to output the interrupt handler as an ordinary function on
>> x86-32-linux.
>
> There can be significant differences between an interrupt handler  
> and a
> void f(void) function.  An interrupt handler may have to:
>
> - Save /all/ registers, including those that are normally caller  
> saved.
> - Use a special return instruction (RETI).
> - Step over the "red zone" on the stack.
> - Set up a safe stack frame before calling normal functions.
>
> I usually write the first level interrupt handler in assembler, and  
> then
> call normal C function from there.

Wouldn't a custom calling convention work for all of these requirements?

-Chris