[llvm-dev] Orc JIT v1 Deprecation

Fri May 17 12:46:24 PDT 2019

I thought I would add a data point.

I implemented the Orc v1 API in Clasp - an implementation of Common Lisp
that uses llvm as the backend.
Recently, I switched over to using the new API - works great!  I'm very
excited about the work Lang has been doing and I'm excited to hear that
there is a fix for lldb debugging of jitted code coming (thanks Stefan!).

Orc v1 API Clasp:  (https://github.com/clasp-developers/clasp/tree/dev)
New Orc API Clasp:  (
https://github.com/clasp-developers/clasp/tree/dev-llvmtot)

It's a bit weird because Clasp is self-hosting and I expose the llvm API's
to Common Lisp and I use the llvm API's in a combination of C++ code and
Common Lisp code.

On Fri, May 17, 2019 at 3:35 PM Stefan Gränitz <stefan.graenitz at gmail.com>
wrote:

> I agree, the deprecation of Orc v1 should come with more guidance and
> preparation than currently available. I don't think you are missing any
> channel. The main sources of information are code and reviews. I gathered
> some data on typical lines of argumentation below. Maybe it makes sense to
> have look at them in isolation.
>
> TL;DR: While I do have a number of proposals for the points in the end, I
> would first like to hear your opinions.
>
> (1) MCJIT can be considered mature and stable, while Orc is experimental:
> * Orc is in trunk for more than 4 years now [1]
> * tutorials moved to Orc with Release 3.8 (3 years ago) [2]
> * "ORC should be preferred for new projects" made it to the official
> release notes only now, with 8.0
> * it's a common statement on the list since many years [3]
>
> (2) The LLVM test suite has various use-cases for lli, so the JIT gets
> exercised well. Grepping through lit tests on master today gives me:
> * 202 matches for lli in total (regex: RUN.*[% ]lli)
> * 80 matches for lli using Orc v1 (regex: RUN.*[% ]lli.*jit-kind=orc-mcjit)
> * 17 matches for lli using Orc v2 (regex: RUN.*[% ]lli.*jit-kind=orc-lazy)
>
> (3) There are few active stakeholders in LLVM JIT development:
> * ExecutionEngine saw about 250 commits in total during the last year
> (looking at: llvm/include/llvm/ExecutionEngine && llvm/lib/ExecutionEngine)
> * 192 of these are from Lang, most of the remaining one's are either not
> touching the JIT or NFC
> * I just submitted a fix for JITed code debugging in LLDB, which was
> broken since Release 5.0 [4]
>
> Conclusions?
> * All newcomers go with Orc, because the tutorial uses it and the list
> recommends it.
> * Some newcomers became clients. Their projects got mature and they ask
> for a more stable API.
> * We saw drastic API changes in Orc with past releases. Upcoming releases
> should account for the rate of adoption more and more.
> * Most clients stay clients. Certainly, there are many reasons for that.
> Anyway, we need more active participation.
>
> It's time to:
> * Switch lli's default to Orc to increase visibility and test coverage. Of
> course, MCJIT-specific tests should pass -jit-kind=mcjit.
> * Agree on a way forward, at least for the current release, so we can
> carve out small/simple tasks and distribute the work in the community. If
> the removal of Orc v1 is part of the plan, we should start convergence soon.
> * Communicate/discuss the current state (haves and wants) regularly and
> transparently.
> * Get more people to participate actively.
>
>
> [1] https://github.com/llvm/llvm-project/commit/93de2a12
> [2]
> http://releases.llvm.org/3.8.0/docs/ReleaseNotes.html#non-comprehensive-list-of-changes-in-this-release
> [3] http://lists.llvm.org/pipermail/llvm-dev/2016-March/097767.html
> [4] https://reviews.llvm.org/D61611
>
> On 5/13/19 10:22 AM, Alex Denisov via llvm-dev wrote:
>
> Hi folks,
>
> Rather by accident than on purpose I looked at the release notes and found the following:http://releases.llvm.org/8.0.0/docs/ReleaseNotes.html#changes-to-the-jit-apis
>
> TL;DR: Orc v1 is deprecated and will be removed in the next release.
>
> I have several questions in this regard:
>
> 1. Is there a migration guide I can use to update my code to the new version?
> 2. Is there any development plan for this part of LLVM? So far I have feeling that it's a closed source development.
> 3. Is there some communication channels I am missing to follow? I follow dev&commits mailing lists and present on IRC once in a while, but I somehow missed the message about the Orc v1 removal.
>
> Also, the release notes mention that Orc v2 is the recommended way for the new projects, but:
>
> 1. Is there a documentation?
> 2. How stable the APIs are?
>
> Thank you,
> Alex.
>
>
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at lists.llvm.orghttps://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
> -- https://flowcrypt.com/pub/stefan.graenitz@gmail.com
>
>

-- 
Christian Schafmeister
Professor, Chemistry Department
Temple University
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