[llvm-dev] [ORC] [mlir] Dump assembly from OrcJit

[Nicolas Vasilache via llvm-dev]

Would be great to have!
I was looking for how to do something like this just a few days ago.


On Fri, Aug 16, 2019, 5:44 PM Caballero, Diego <diego.caballero at intel.com>
wrote:

> + MLIR dev mailing list since that’s where the OrcJit I’m using is.
>
>
>
> Thanks for all the details, Lang! What you described is exactly what I’m
> looking for!
>
>
>
> Please, MLIR dev, let me know if this debug feature and the solution that
> Lang describes below is interesting for MLIR. I’ll dig more into the
> details then but it doesn’t seem too complicated.
>
>
>
> Thanks,
>
> Diego
>
>
>
> *From:* Lang Hames [mailto:lhames at gmail.com]
> *Sent:* Friday, August 16, 2019 1:07 PM
> *To:* Caballero, Diego <diego.caballero at intel.com>
> *Cc:* llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] [ORC] Dump assembly from OrcJit
>
>
>
> Hi Diego,
>
>
>
> That is probably your best option for dumping textual assembly directly,
> but unless you need local symbol names and enhanced disassembly notes there
> is a better option: Dump object files from the JIT and disassemble them.
> Dumping object files has two advantages over assembly: (1) it avoids
> redundant codegen, so is much faster, and (2) the bits you're dumping are
> *exactly* the bits flowing into the JIT linker: there is no chance of
> getting misleading assembly due to a compiler misconfiguration or
> persistent state bug.
>
>
>
> One way to dump object files, which works for both LLJIT and custom
> stacks, is to attach a dummy ObjectCache (see
> https://github.com/llvm/llvm-project/blob/master/llvm/examples/LLJITExamples/LLJITWithObjectCache/LLJITWithObjectCache.cpp)
> and dump the ObjBuffers that are passed in to the cache to disk. You can
> just return 'nullptr' from your dummy cache's getObject method, since you
> are not really using it as a cache.
>
>
>
> Alternatively, If you are writing a custom ORC stack there is a second
> option: You can insert an ObjectTransformLayer between your IRCompileLayer
> and ObjectLinkingLayer and use that to dump the buffers to disk.
>
>
>
> I hope this helps!
>
>
>
> -- Lang.
>
>
>
> On Thu, Aug 15, 2019 at 3:44 PM Caballero, Diego via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hi all,
>
>
>
> Is there a way to dump the generated assembly from OrcJit? I found this
> thread about MCJIT but nothing specific about OrcJit:
> http://lists.llvm.org/pipermail/llvm-dev/2014-June/074145.html
>
> I’m also aware of the alternative approach below, but I’m not sure if the
> output will be the same as the assembly generated by OrcJit. Probably not.
>
>
>
>     std::string outStr;
>
>     {
>
>       llvm::legacy::PassManager pm;
>
>       llvm::raw_string_ostream stream(outStr);
>
>       llvm::buffer_ostream pstream(stream);
>
>       targetMachine->addPassesToEmitFile(pm, pstream, nullptr,
>
>
> llvm::TargetMachine::CGFT_AssemblyFile);
>
>       pm.run(*m);
>
>     }
>
>     llvm::errs() << "Assembly:\n" << outStr << "\n";
>
>
>
> Thanks!
>
> Diego
>
>
>
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