llvm dev - Nov 2012 - [LLVMdev] Inserting pthread_create call into sequential code

Hi,

I was working on multithreading a cross iteration loop. I want to insert a
pthread_create function call and use other pthread functions into my LLVM
IR.

Issue is how do i get these functions using
module->getOrInsertFunction("pthread_create"), since the function
might not
be there in IR and then insert function calls to these functions.

So, crux is how do i call pthread function calls into LLVM IR for a
sequential program.

Pardon me for such a basic doubt as I am a novice in llvm yet.

Regards,
Pankit Thapar
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On Mon, Nov 12, 2012 at 6:22 PM, Pankit Thapar <pankit at umich.edu>
wrote:
> Hi,
>
> I was working on multithreading a cross iteration loop. I want to insert a
> pthread_create function call and use other pthread functions into my LLVM
> IR.
>
> Issue is how do i get these functions using
> module->getOrInsertFunction("pthread_create"), since the
function might not
> be there in IR and then insert function calls to these functions.
>
> So, crux is how do i call pthread function calls into LLVM IR for a
> sequential program.
>
> Pardon me for such a basic doubt as I am a novice in llvm yet.
One quick way you could investigate this is by using the LLVM demo
page http://llvm.org/demo (or the LLVM cpp backend). It's not perfect,
but might do in a pinch.

by compiling simple code like:

void my_func();

int main() {
  my_func();
}

& targeting the cpp backend ("LLVM C++ API code") you can see what
kind of C++ code you might need to write to call an external function.
Then calling pthread_create or any other function is just a matter of
getting the signature right, basically.

- David