[LLVMdev] Multiple module support in MCJIT

[Kaylor, Andrew]

I'm about to start working on multiple module support in MCJIT.  I know a lot of people are interested in this so it seemed like a good idea to begin by soliciting input.

My immediate plan involves the following:

- Add something to the MCJIT interface to explicitly request module compilation
- Isolate module-specific state variables into a structure so that the state of each module can be tracked independently
- Identify intermediate objects (such as Target Machine) which have module-specific states and duplicate them as necessary
- Implement a mechanism to automatically attempt to resolve external symbols from a module being loaded against any modules that are associated with the same instance of MCJIT.

I do not intend (at this time) to address the case where modules have mutual dependencies on one another, though I imagine that will be a case that we'll want to handle in the future.

There's a bit of ugliness that has crept in where RuntimeDyld maintains a module-related state.  That wasn't supposed to happen and now that it has I'll have to do something about it.  I'll need to do a bit of experimenting to determine the best/easiest approach to take at this time.

I expect that what I'm going to do will more or less follow the shape of what I wrote about in the MCJIT/Kaleidoscope blog posts a couple of months ago, moving whatever I can inside MCJIT.

If anyone has any work in progress in this area or requirements that you want to make sure get addressed, please let me know very soon.

Thanks,
Andy