[llvm-dev] ORC JIT Weekly #1
Andres Freund via llvm-dev
llvm-dev at lists.llvm.org
Mon Jan 27 10:14:24 PST 2020
On 2020-01-16 18:00:53 -0800, Lang Hames via llvm-dev wrote:
> In the interests of improving visibility into ORC JIT development I'm
> going to try writing weekly status updates for the community. I hope
> they will provide insight into the design and state of development of
> LLVM's JIT APIs, as well as serving as a convenient space for
> discussions among LLVM's large and growing community of JIT API users.
That's a great idea.
> Since this is the first update, I have also added some highlights from last year, and the plan for 2020.
> Highlights from 2019:
> (1) ORCv1 was officially deprecated in LLVM 9. I have left it in for
> the LLVM 10 branch, but plan to remove it from master in the coming
> weeks. All development effort is now focused on ORCv2. If you are an
> ORCv1 client, now's the time to switch over. If you need help please
> ask on the llvm-dev mailing lists (make sure you CC me) or #llvm on
> discord. There are also some tips available in
I also want to highlight the necessity of some form of C API, that
others already have.
Besides just needing something that can be called from languages besides
C++, some amount of higher API stability is also important. For users of
LLVM with longer support cycles than LLVM (e.g. Postgres has 5 years of
back branch maintenance), and which live in a world where vendoring is
not allowed (most things going into linux distros), the API churn can be
serious problem. It's fine if the set of "somewhat stable" C APIs
doesn't provide all the possible features, though.
It's easy enough to add a bunch of wrappers or ifdefs hiding some simple
signature changes, e.g. LLVMOrcGetSymbolAddress adding a parameter as
happened in LLVM 6, but backpatching support for a larger API redesigns,
into stable versions, is scary. We do however quickly get complaints if
a supported version cannot be compiled due to dependencies, as people
tend to upgrade their OS separately from e.g. their database major
> (2) LLVM has a new JIT linker, JITLink, which is intended as an
> eventual replacement for RuntimeDyld. The new design supports linker
> plugins (allowing operation on the low-level bits generated by the JIT
> linker) and native code models (RuntimeDyld required a custom code
> model on some platforms). Currently JITLink only supports Darwin
> x86-64 and arm64, but I hope to see support for new platforms added in
> the future.
What's the capability level of ORCv2 on RuntimeDyld compared to ORCv1?
Are there features supported in v1 that are only available on JITLink
> - Improve JIT support for static initializers:
> - Add support for running initializers from object files, which will enable loading and caching of objects containing initializers.
Hm, that's kind of supported for v1, right?
More information about the llvm-dev