llvm dev - Aug 2016 - Designing on-disk ObjectCache for JIT

Hi Lang, LLVM,

Do you have any suggestions about implementing on-disk ObjectCache for
MCJIT/Orc? Anyone is able to point me to / share some existing code?

I also noticed that recently "cache pruning" support was added to LLVM
(ported from clang) [1]. Is it good idea to extent it to also manage saving
and loading objects to disk and create full-featured on-disk cache engine?

[1] https://reviews.llvm.org/D18422

- Paweł
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Hi,

On Thu, 18 Aug 2016 20:23:08 +0000
Paweł Bylica via llvm-dev <llvm-dev at lists.llvm.org>
wrote:
> Hi Lang, LLVM,
> 
> Do you have any suggestions about implementing on-disk ObjectCache for
> MCJIT/Orc? Anyone is able to point me to / share some existing code?
You can find what we did for llvmlite and Numba here.

There's a low-level C shim in llvmlite, wrapping the C++ APIs to make
them callable using ctypes from Python:
https://github.com/numba/llvmlite/blob/master/ffi/executionengine.cpp#L162-L247

Then there's a Python wrapper around that in llvmlite, to make the API
handle regular Python objects:
https://github.com/numba/llvmlite/blob/master/llvmlite/binding/executionengine.py#L149-L198

Then there's a higher-level abstraction in Numba that works around the
callback-oriented nature of the LLVM API, and also handles additional
tasks such as finalizing the module after loading the object code:
https://github.com/numba/numba/blob/master/numba/targets/codegen.py#L236-L349

I'm afraid this code is quite a mouthful :-)

Regards

Antoine.

Hi Pawel,

Do you have any suggestions about implementing on-disk ObjectCache
for
> MCJIT/Orc? Anyone is able to point me to / share some existing code?

There is a demo implementation in llvm/tools/lli/lli.cpp, but I don't think
it goes beyond proof-of-concept.

I also noticed that recently "cache pruning" support was added to
LLVM
> (ported from clang) [1]. Is it good idea to extent it to also manage saving
> and loading objects to disk and create full-featured on-disk cache engine?

I can imagine LTO and the JIT sharing some caching infrastructure. I
haven't had time to work on the caching problem yet, but I'd be very
happy
to see more in-tree support for it.

Cheers,
Lang.

On Thu, Aug 18, 2016 at 1:23 PM, Paweł Bylica <chfast at gmail.com> wrote:
> Hi Lang, LLVM,
>
> Do you have any suggestions about implementing on-disk ObjectCache for
> MCJIT/Orc? Anyone is able to point me to / share some existing code?
>
> I also noticed that recently "cache pruning" support was added to
LLVM
> (ported from clang) [1]. Is it good idea to extent it to also manage saving
> and loading objects to disk and create full-featured on-disk cache engine?
>
> [1] https://reviews.llvm.org/D18422
>
> - Paweł
>
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