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

[Alex Zinenko via llvm-dev]

Indeed, dumping the assembly would be a helpful option for mlir-*-runner.

On Sat, Aug 17, 2019 at 1:05 AM Nicolas Vasilache <
nicolas.vasilache at gmail.com> wrote:

> 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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-- 
-- Alex
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