Interpreter with multiple modules.

Hi everybody,

I'm currently working with LLVM (v 2.6) and I try to interpret LLVM bitcode
using the c API. Here is my problem : I have two LLVMModuleRef, M1 and M2,
M1 contains the function "funct()" and M2 contains a main function which
call "funct()" (M2 declares "funct()" too but it doesn't define it). If I
try to run the main function, I got the error "LLVM ERROR: Tried to execute
unknown external function: ...".

I build the interpreter giving it M1 and then I add M2. I can use the
LLVMFindFunction(...) to get the functions "funct()" and "main()" and if I
apply LLVMIsDeclaration(...) to these LLVMValueRef, I got false (so the
interpreter should know the two functions are defined and it should be able
to find their code).

Is there something to do to enable the interpreter to find a function in
another module ? I saw there is something like LLVMLinker::LinkModules(...)
in c++ but I didn't find the c version of this function.

Thanks in advance for your help,

Thomas.

I have not used the C api or the interpreter, but via JIT one can use
ExecutionEngine::addGlobalMapping(...) after the function decl in the
foreign module. See if there is an equivalent in the C API, which will
probably work for the interpreter given that this method is declared in
ExecutionEngine. Also search for a previous email thread in this list.
This discussion was fairly recent, and I believe I responded to it.

Hope this helps

Garrison

Garrison Venn wrote:

I have not used the C api or the interpreter, but via JIT one can use
ExecutionEngine::addGlobalMapping(...) after the function decl in the
foreign module. See if there is an equivalent in the C API, which will
probably work for the interpreter given that this method is declared in
ExecutionEngine. Also search for a previous email thread in this list.
This discussion was fairly recent, and I believe I responded to it.

Hope this helps

Garrison

Thanks.

There is a addGlobalMapping(...) function in the C api, but it's not what
I'm looking for. I want the interpreter to automatically link the two
modules. What I want is the following : if the interpreter don't see the
function definition in a module, then it looks at each modules I have
previously added and if it find the function, then it run it just as if it
was in the module.

I will take a look at the previous thread as you suggest me.

Thomas.

I have not used the C api or the interpreter, but via JIT one can use
ExecutionEngine::addGlobalMapping(…) after the function decl in the
foreign module. See if there is an equivalent in the C API, which will
probably work for the interpreter given that this method is declared in
ExecutionEngine. Also search for a previous email thread in this list.
This discussion was fairly recent, and I believe I responded to it.

This is interesting. I’ve just implemented dynamic loading of bitcode modules into lli for my project. I did this by hacking lli using the Linker class. Is ExecutionEngine::addGlobalMapping() preferred for this purpose?

– James

Hi James,

This is interesting. I've just implemented dynamic loading of bitcode modules into lli for my project. I did this by hacking lli using the Linker class. Is ExecutionEngine::addGlobalMapping() preferred for this purpose?

I'm not sure about the preferred way, but at least for the JIT, here is an email from Jeffrey
concerning a previous thread. The issue in that thread was solved via use of
ExecutionEngine::addGlobalMapping(...). I don't know if the inability of the JIT or
interpreter systems to automatically search in other modules is by design or not.

Garrison

Hi James,

This is interesting. I’ve just implemented dynamic loading of bitcode modules into lli for my project. I did this by hacking lli using the Linker class. Is ExecutionEngine::addGlobalMapping() preferred for this purpose?

I’m not sure about the preferred way, but at least for the JIT, here is an email from Jeffrey
concerning a previous thread. The issue in that thread was solved via use of
ExecutionEngine::addGlobalMapping(…). I don’t know if the inability of the JIT or
interpreter systems to automatically search in other modules is by design or not.

Hi Garrison,

Thanks for that. I got the same error that Michael Muller posted below and just assumed I’d need to use the linker to resolve it. I’m linking dynamically loaded modules on demand into the existing main module for the running program created by lli on startup. This seems to work on small test cases but I’ve no idea if this is the right thing to do (I doubt it’s thread safe for example given the naive way I’m doing it). I think I need to go read the source and documentation!

– James

Garrison Venn wrote:
I don't know if the inability of the JIT or

interpreter systems to automatically search in other modules is by design or not.

http://llvm.org/PR2606

Nick