llvm dev - Dec 2006 - [LLVMdev] jit with external functions

I have an application that is generating llvm assembler text files, these
are then loaded with ParseAssemblyFile. I am also using
ExecutionEngine::runFunction
to call functions in the loaded/created modules.

Can I place references to external functions in the assembler files? For example
I if my application has a function called fred() I would like to place
calls to fred
in the assembler text file. Can I do that and have the external function call
resolve to the address of fred() in my application?

Thanks for any assistance.
-Ram

On Fri, 8 Dec 2006, Ram Bhamidipaty wrote:
> Can I place references to external functions in the assembler files? For
example
> I if my application has a function called fred() I would like to place
> calls to fred
> in the assembler text file. Can I do that and have the external function
call
> resolve to the address of fred() in my application?
Yes, you can do this.  The JIT will transparently call dlsym on the main 
process to resolve external function calls.  This allows it to find 
standard lib functions like printf, it also allows your code to call into 
your own functions.

-Chris

-- 
http://nondot.org/sabre/
http://llvm.org/

On 12/8/06, Chris Lattner <sabre at nondot.org>
wrote:
> On Fri, 8 Dec 2006, Ram Bhamidipaty wrote:
> > Can I place references to external functions in the assembler files?
For example
> > I if my application has a function called fred() I would like to place
> > calls to fred
> > in the assembler text file. Can I do that and have the external
function call
> > resolve to the address of fred() in my application?
>
> Yes, you can do this.  The JIT will transparently call dlsym on the main
> process to resolve external function calls.  This allows it to find
> standard lib functions like printf, it also allows your code to call into
> your own functions.
Will it also handle symbols that are in shared libraries loaded into
the process?

I am creating a python module that has the llvm functionality. This
module is loaded
into the process as a shared library. I want to generate llvm assembler that has
calls to functions in this shared library.

I just tried an experiment and I got this back:

ERROR: Program used external function 'rtcg_callback' which could not
be resolved!
Aborted

It looks like the additional shared libraries might not be searched. I
plan on looking at
the code to see if I can modify it to handle my case. Any suggestions
on how or where
I should make the change?

Thanks for the info.
-Ram