[llvm-dev] ORC v2 question

[Lang Hames via llvm-dev]

Hi Dibyendu,

A couple of notes to simplify your code. The following:

#if USE_ORCv2_JIT
    auto FPM = llvm::make_unique<FunctionPassManager>(TSM.getModule());
#else
    std::unique_ptr<FunctionPassManager> FPM(new
FunctionPassManager(M.get()));
#endif

can be reduced to

auto FPM = llvm::make_unique<FunctionPassManager>(&*M);

since M must be non-null.

Likewise, this:

#if USE_ORCv2_JIT
    for (auto &F : *TSM.getModule())
      FPM->run(F);
#else
    for (auto &F : *M)
      FPM->run(F);
#endif

can be reduced to

for (auto &F : *M)
  FPM->run(F);

When you say your code is not getting optimized, do you mean that IR
optimizations are not being applied, or that codegen optimizations are not
being applied?

What do you see if you dump the modules before/after running the pass
manager on them, like this:

dbgs() << "Before optimization:\n" << *M << "\n";
for (auto &F : *M)
  FPM->run(F);
dbgs() << "Before optimization:\n" << *M << "\n";

I expect that output to be the same for both ORC and ORCv2. If not
something is going wrong with IR optimization.

CodeGen optimization seems a more likely culprit: JITTargetMachineBuilder
and ExecutionEngineBuilder have different defaults for their CodeGen
opt-level. JITTargetMachineBuilder defaults to CodeGenOpt::None, and
ExecutionEngineBuilder default to CodeGenOpt::Default.

What happens if you make the following modification to your setup?

auto JTMB = llvm::orc::JITTargetMachineBuilder::detectHost();
*JTMB->setCodeGenOptLevel(CodeGenOpt::Default); // <-- Explicitly set
Codegen opt level*
auto dataLayout = JTMB->getDefaultDataLayoutForTarget();

Hopefully one of these approaches helps. If not let me know and we can dig
deeper -- I would like to help you to get this working.

Cheers,
Lang.

On Tue, Aug 13, 2019 at 1:10 PM Dibyendu Majumdar <mobile at majumdar.org.uk>
wrote:

> Hi Lang,
>
> On Tue, 13 Aug 2019 at 20:47, Lang Hames <lhames at gmail.com> wrote:
> >
> > Sorry for the delayed reply. Looks like you have figured out how to
> solve your issue already. Out of interest, what did you need to do? Do you
> have anything that you would like to see added to
> http://llvm.org/docs/ORCv2.html ?
> >
>
> Sorry my post was misleading. I figured out below which was part of the
> problem.
> Code is still not getting optimized at all. I don't really know what
> is going on.
>
> Yet the same setup works fine with the Legacy ORC v1 setup.
>
> Any help is appreciated.
>
> Here are again the links to the relevant code:
>
>
> https://github.com/dibyendumajumdar/ravi/blob/master/include/ravi_llvmcodegen.h
> https://github.com/dibyendumajumdar/ravi/blob/master/src/ravi_llvmjit.cpp
>
> Just look sections marked USE_ORCv2_JIT.
>
> >> > Optimize Module is just a function object.
> >> >
> >>
> >> Thank you - I fixed that now.
>
> Regards
> Dibyendu
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20190813/1fa36853/attachment.html>