[LLVMdev] Multiple module support in MCJIT

Kaylor, Andrew andrew.kaylor at intel.com
Tue Sep 17 16:01:51 PDT 2013

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.


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