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How would I go about enabling the ORC JIT to compile code in multiple threads?

Some background:

I’ve switched Clasp (an implementation of Common Lisp that uses llvm as the backend - github.com/drmeister/clasp) over to using ORC as its JIT. I did this by following the Kaleidoscope tutorial. I have a ClaspJIT\_O class that copies the KaleidoscopeJIT class.

Clasp is multithreaded and it needs to compile code in multiple threads because it uses the JIT to generate dispatch functions for multiple dispatch/generic functions. To make this possible, every thread gets its own LLVMContext and every type and llvm::Module that is linked into JITted code in each thread is initialized lazily and thread-locally. Despite this - I experience frequent, random crashes when I try to use the ORC JIT from multiple threads.

Here’s what I’ve tried:

(1) This works: wrap a lock/mutex around access to one ClaspJIT\_O object, the calls to ClaspJIT\_O::addModule and a call to jitFinalizeReplFunction are protected by the lock:

The Common Lisp code that does the lock and calls these functions:

This throttles the system and limits one thread at a time to add modules to the JIT and lookup symbols in the JIT. It’s not bad - I can live with it.

(2) This fails: Keep a thread local copy of a ClaspJIT\_O object that is lazily initialized as soon as any compilation happens in a thread.

(3) This fails: Keep a thread local copy of a ClaspJIT\_O object that is initialized as in #2 AND wrap a lock/mutex around ClaspJIT\_O::addModule and a call to jitFinalizeReplFunction. What I thought I was testing here was if there was some global resource that ORC uses and despite having multiple thread-local ClaspJIT\_O objects the different threads were trampling that common global resource.

I can provide many more details on request.

Christian Schafmeister