llvm dev - Jun 2007 - [LLVMdev] How to call native functions from bytecode run in JIT?

On Tue, 12 Jun 2007, Jan Rehders wrote:
>> Jan, how are you doing this?  Are you creating an external LLVM 
>> Function object named "get5", then using
EE::addGlobalMapping?  If
>> 'get5' exists in the address space, why not just let the JIT
resolve it
>> (which will then create the stub)?
>
> Yes. I create a Function with matching signature, calling conventions
> and external linkage which I pass together with the function's
> address to addGlobalMapping.
Okay.  If the function exists in your application's address space already, 
just name the LLVM function the same name as the native function and the 
JIT should find it an do the right thing.  This is how it finds printf and 
a variety of other things.  You don't need to call addGlobalMapping at 
all.

Does this work?

-Chris

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

Hi,
> Okay.  If the function exists in your application's address space  
> already,
> just name the LLVM function the same name as the native function  
> and the
> JIT should find it an do the right thing.  This is how it finds  
> printf and
> a variety of other things.  You don't need to call addGlobalMapping at
> all.
Looking at the output of "nm codegen1" I realized that
"get5" was a C+
+ function whose name was mangled to "__Z4get5v". Surrounding it by  
extern "C" helped a lot :) Now the function is found by the JIT and I
can call it using EE->runFunction als well as using a CallInst.
> Does this work?
However, one strange effet remains: if I first call the function  
using EE->runFunction and then try to call it using a CallInst inside  
another function I get the old "relocation" error in PPCJITInfo.cpp,  
again. Using a CallInst first, then runFunction and then a CallInst  
again works, though. For my project this is probably a non-issue but  
it might indicate some problem in either my code or LLVM - any ideas?

Anyway, thank you all for the helpful comments. I'd surely yielded to  
despair without your help :)

- Jan

Hi,

I was able to try this on linux again. Unfortunately it doesn't work  
at all (neither using runFunction nor a CallInst). It simply says  
function called get5 not known. Calling printf the same way works,  
though. On linux the function is exported as "get5" from the  
executable while it is called "_get5" on OS X. I could not spot any  
other differences.. any thoughts?

greetings,
Jan

On 12. Jun 2007, at 23:08, Jan Rehders wrote:
> Hi,
>
>> Okay.  If the function exists in your application's address space
>> already,
>> just name the LLVM function the same name as the native function
>> and the
>> JIT should find it an do the right thing.  This is how it finds
>> printf and
>> a variety of other things.  You don't need to call  
>> addGlobalMapping at
>> all.
>
> Looking at the output of "nm codegen1" I realized that
"get5" was a C+
> + function whose name was mangled to "__Z4get5v". Surrounding it
by
> extern "C" helped a lot :) Now the function is found by the JIT
and I
> can call it using EE->runFunction als well as using a CallInst.
>
>> Does this work?
>
> However, one strange effet remains: if I first call the function
> using EE->runFunction and then try to call it using a CallInst inside
> another function I get the old "relocation" error in
PPCJITInfo.cpp,
> again. Using a CallInst first, then runFunction and then a CallInst
> again works, though. For my project this is probably a non-issue but
> it might indicate some problem in either my code or LLVM - any ideas?
>
> Anyway, thank you all for the helpful comments. I'd surely yielded to
> despair without your help :)
>
> - Jan
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

On Tue, 12 Jun 2007, Jan Rehders wrote:
> Looking at the output of "nm codegen1" I realized that
"get5" was a C+
> + function whose name was mangled to "__Z4get5v". Surrounding it
by
> extern "C" helped a lot :) Now the function is found by the JIT
and I
> can call it using EE->runFunction als well as using a CallInst.
That would definitely do it :)
>> Does this work?
>
> However, one strange effet remains: if I first call the function
> using EE->runFunction and then try to call it using a CallInst inside
> another function I get the old "relocation" error in
PPCJITInfo.cpp,
> again. Using a CallInst first, then runFunction and then a CallInst
> again works, though. For my project this is probably a non-issue but
> it might indicate some problem in either my code or LLVM - any ideas?
There definitely is a bug here: your initial code should have worked. 
That said, noone has stepped up to fix it, and I'm busy with many other 
things.  If you'd like to dig in and fix the bug, that would be excellent
:)

-Chris

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