[llvm-dev] MCJIT -- Poor run-time performance for Fibonacci example in LLVM 3.8.1

Lang Hames via llvm-dev llvm-dev at lists.llvm.org
Fri Jun 10 17:06:19 PDT 2016

Hi Riyaz, Renato,

Attempting to run Fibonacci from LLVM 3.8.1 on Darwin I get:

./fib381: Failed to construct ExecutionEngine: Interpreter has not been
linked in.

This suggests that the reason for the slowdown isn't in the JIT itself.
Instead, when we removed the old JIT we probably didn't update the
Fibonacci example to request a JIT at all, so now it's falling back to the
interpreter. I'm just digging in to confirm this now, and will update the
example code as needed to fix this.


On Fri, Jun 10, 2016 at 5:38 AM, Renato Golin via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On 10 June 2016 at 05:31, Riyaz Puthiyapurayil via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > We have been using LLVM 3.4 and are currently migrating to LLVM 3.8.1. We
> > have been using the Old JIT and since it has been removed since 3.6, we
> have
> > to use MCJIT.
> Hi Riyaz,
> I don't know much about it, but MCJIT was also replaced, by a new JIT
> called "ORC".
> The Kaleidoscope example has been updated, you can look there:
> http://llvm.org/docs/tutorial/LangImpl4.html
> cheers,
> --renato
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> llvm-dev at lists.llvm.org
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