[LLVMdev] Jit singleton
meurant.olivier at gmail.com
Wed Feb 10 10:11:12 PST 2010
Thanks Jeffrey !
If possible, keep me inform (on revision number), I'm interested to see how
you will do the unit test. (For my future patch... :) ).
On Wed, Feb 10, 2010 at 6:22 PM, Jeffrey Yasskin <jyasskin at google.com>wrote:
> Thanks for the patch! I'll clean this up, convert your sample to a
> unit test, and commit it for 2.7.
> On Sun, Feb 7, 2010 at 6:09 AM, Olivier Meurant
> <meurant.olivier at gmail.com> wrote:
> > Hi Jeffrey,
> > Thanks for pointing me in the right direction !
> > I'm not using the JIT in lazy mode, but it was fun to understand the
> > lazy-stub code.
> > Attached you will find a patch which follow your 1st option : a map
> > Stub_address -> JITResolver instance, except that the used map is a
> > "std::map" to apply the same upper_bound trick as in the map
> > CallSiteToFunctionMap of the ResolverState. (If it is necessary for
> > call_site -> function, this should be necessary for call_site ->
> > Event if I'm not sure to master all subtle reasons - code
> > ?)
> > A mutex on the StubToResolverMap should prevent any possible race
> > conditions.
> > Every object (Emitter, Resolver, ResolverState) have now a private member
> > instance of JIT (JIT *Jit).
> > The bugpoint tool is using a extern 'C' function :
> > "getPointerToNamedFunction" to get native pointer on function. This
> > used the TheJit static pointer. To keep alive this functionality, I have
> > added a static SmallVector<JIT*> JitPool (with its mutex JitPoolLock),
> > keep pointers of available JIT instance. A new static method on JIT
> > "getPointerToNamedFunctionOnJitPool" fills the need (iterate over
> > JIT to find the function).
> > Attached you will find a test, based on "HowToUseJit" example, which
> > instantiate 2 JIT, in eager/lazy mode and retrieve native pointer via
> > getPointerToNamedFunction function. Where does it belong ? Should I add
> > something to llvm test suite ? To the test directory ?
> > Let me know what you think !
> > Thanks.
> > Olivier.
> > On Thu, Feb 4, 2010 at 9:03 PM, Jeffrey Yasskin <jyasskin at google.com>
> >> In eager compilation mode, I don't know of anything that would go
> >> wrong with having multiple JITs in the process. However, in lazy
> >> compilation mode, we need to map stub addresses to the JIT that knows
> >> how to compile them. Right now, that's done by looking up the static
> >> "TheJITResolver" variable and assuming it's the only JIT, but we could
> >> 1) use a static DenseMap<stub_address, JITResolver*> instead, or 2)
> >> include the JITResolver* inside the stub as an argument to the
> >> compilation callback. Nobody's needed this enough to get it working
> >> though.
> >> I think it'd make some sense to fix it for eager compilation even
> >> before getting lazy compilation working. Would you like to write a
> >> patch? You'll have to remove all uses of TheJIT and TheJITResolver
> >> except for the one in JITResolver::JITCompilerFn, and change the "only
> >> one JIT" check to say something about "only one JIT compiling lazily".
> >> I don't think this change will require passing an LLVMContext to the
> >> JIT--it should just use the Context of the function it's jitting.
> >> The code freeze for llvm-2.7 is on Feb 21 (this probably isn't a
> >> "major" change), so if you want it in the 2.7 release, please try to
> >> mail the patch well ahead of that.
> >> On Thu, Feb 4, 2010 at 5:47 AM, Olivier Meurant
> >> <meurant.olivier at gmail.com> wrote:
> >> > Hi everyone !
> >> >
> >> > If I call ExecutionEngine::createJIT (or EngineBuilder::create) more
> >> > than
> >> > one time, the second time fails on a assertion "Multiple JIT
> >> > resolvers?".
> >> > It seems that the JIT is designed to be a singleton in the process,
> >> > I
> >> > was wondering if it was something mandatory.
> >> > How hard will it be to make it a non-singleton object ? Is this a
> >> > JIT-only
> >> > problem (work needed on JIT classes only) ? Is it a much wider design
> >> > constraint (on codegen ?) ?
> >> >
> >> > In case, if you ask why I want to create more than one JIT, here is a
> >> > reason
> >> > :
> >> > I have a JIT application which works fine, a thread is responsible to
> >> > prepare code execution (work on module, add functions, optimize, call
> >> > JIT...) and a another thread is responsible for executing the code
> >> > produced
> >> > in the first thread.
> >> > It works great, but the preparation thread is heavily loaded. I decide
> >> > to
> >> > look at what happens, if I spawns 2 threads for preparation of the
> >> > I have a working prototype, which have one module and one context by
> >> > thread,
> >> > and it works. But the JIT is still shared between 2 threads and the
> >> > needed to emit a function is not negligible. It will be a great boost
> >> > performances, if I can create one execution engine by thread.
> >> >
> >> > What do you think ? Do you have any comments on it ?
> >> > Thanks for reading !
> >> >
> >> > Olivier.
> >> >
> >> > _______________________________________________
> >> > LLVM Developers mailing list
> >> > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >> >
> >> >
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