[llvm-dev] ORC JIT Weekly #21 -- OrcV1 removal, Removable code, and Remote TargetProcessControl

[Lang Hames via llvm-dev]

Oh, I almost forgot: The "orcv1-removal-with-remote-tpc" also contains a
next step towards breaking Orc up into distinct libraries.

Chris Bieneman started this process on the mainline a while back by moving
some of the Orc error types into a separate OrcError library (Thanks
Chris!). The orcv1-removal-with-remote-tpc branch takes this further.

(1) It adds a new OrcTargetProcess library that contains code specific to
JIT execution. E.g. runAsMain, in-process eh-frame registration code, and
the OrcRPCTPCServer type.
(2) It renames OrcError to OrcShared. This will be a home for types that
are shared between Orc and OrcTargetProcess. It's likely to me mostly
headers, but may contain some code snippets.

This break-up isn't fully implemented in the branch yet: Orc still depends
directly on OrcTargetProcess in places. This is just incomplete work, not
by design.

Eventually I hope to decouple Orc (and JITLink) from ExecutionEngine
entirely. With the removal of OrcV1 this should be much easier: The main
changes will be a substitute types for JITTargetAddress and
JITEvaluatedSymbol (we can come up with better names for them while we're
at it), and moving RTDyldObjectLinkingLayer from ORC to RuntimeDyld.

Thoughts on the break-up (and any of the topics from the weekly mail) are
very welcome.

Finally, correcting the typo above -- the final example should have been:

target-machine% llvm-jitlink-executor listen=localhost:20000
jit-machine% llvm-jitlink -oop-executor-connect localhost:*20000*
hello-world.o
hello world!

-- Lang.

On Sun, Sep 13, 2020 at 11:01 PM Lang Hames <lhames at gmail.com> wrote:

> Hi All,
>
> Everything is landing all at once, just not in the mainline... yet.
>
> As discussed in
> http://lists.llvm.org/pipermail/llvm-dev/2020-September/144885.html:
> OrcV1 will be removed very soon. I have posted a branch with the removal,
> "orcv1-removal", in my llvm fork at https://github.com/lhames/llvm-project
> .
>
> In addition to removing OrcV1, the orcv1-removal branch also contains a
> prototype of the removable code feature. I'm going to discuss this at
> greater length over the next couple of weeks, but if anyone's interested in
> playing with the prototype I'd recommend starting with the
> *ResourceTracker* class in
> https://github.com/lhames/llvm-project/commit/de6f6d57d3e955b998f82ab6e610da41fcb09492
> .
>
> Finally, adding removable code unblocked another prototype I've been
> working on: an OrcRPC based TargetProcessControl implementation. I've added
> that to the "orcv1-removal-with-remote-tpc" branch at
> https://github.com/lhames/llvm-project. The easiest way to start playing
> with this feature is via the new llvm-jitlink options: -oop-executor, and
> -oop-executor-connect. The -oop-executor option will fork and exec the
> llvm-jitlink-executor program and connect to it via open file descriptors
> (similar to how lli-child-target works). The -oop-executor-connect option
> will connect to a listening llvm-jitlink-executor process via TCP, but
> otherwise behaves the same. E.g.
>
> % llvm-jitlink -oop-executor hello-world.o
> hello world!
>
> target-machine% llvm-jitlink-executor listen=localhost:20000
> jit-machine% llvm-jitlink -oop-executor-connect localhost:2000
> hello-world.o
> hello world!
>
> How all this works is left as an exercise for the reader this week. I can
> start providing explanations in my next update.
>
> -- Lang.
>
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