[llvm-dev] MCJit Runtine Performance

[Matt Godbolt via llvm-dev]

I'm using
    builder.setMCPU(llvm::sys::getHostCPUName())

which seems to do the trick.

--matt


On Mon, Feb 8, 2016 at 3:37 AM Paweł Bylica <llvm-dev at lists.llvm.org> wrote:

> Hi all,
>
> Can someone also explain how to configure MCJIT to generate code for
> native target (like clang's -march=native)?
>
> Thanks,
> Paweł
>
> On Mon, Feb 8, 2016 at 2:01 AM Morten Brodersen via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi Lang,
>>
>>
>> > can you share your EngineBuilder configuration lines?
>>
>> Sure.
>>
>> The 3.5.2 version use:
>>
>>         llvm::ExecutionEngine* ee =
>>             llvm::EngineBuilder(module)
>>                 .setEngineKind(llvm::EngineKind::JIT)
>>                 .setOptLevel(llvm::CodeGenOpt::Aggressive)
>>                 .create();
>>
>>         module->setDataLayout(ee->getTargetMachine()->getDataLayout());
>>
>> And the 3.7.1 version use:
>>
>>         llvm::EngineBuilder builder(move(modulePtr));
>>
>>         builder.setEngineKind(llvm::EngineKind::JIT);
>>         builder.setErrorStr(&error);
>>         builder.setOptLevel(llvm::CodeGenOpt::Aggressive);
>>
>>         llvm::ExecutionEngine* ee = builder.create();
>>
>>         module->setDataLayout(*ee->getTargetMachine()->getDataLayout());
>>
>> Cheers
>>
>> Morten
>>
>>
>> On 05/02/16 19:13, Lang Hames wrote:
>>
>> Hi Morten,
>>
>> Something else just occurred to me: can you share your EngineBuilder
>> configuration lines? (
>> http://llvm.org/docs/doxygen/html/classllvm_1_1EngineBuilder.html)
>>
>> In particular - are you explicitly setting the optimization level? The
>> old JIT may have had a different default.
>>
>> - Lang.
>>
>>
>>
>> Sent from my iPad
>>
>> On Feb 4, 2016, at 10:54 PM, Jim Grosbach via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>> I agree with Lang and Keno here. This is both unexpected and very
>> interesting. Given the differences in defaults between the two, I would
>> have expected the new JIT to have better performance but longer compile
>> times. That you are seeing the opposite implies there is something very
>> wrong and I'm very interested to help figure out what it is.
>>
>> Sent from my iPad
>>
>> On Feb 4, 2016, at 9:12 PM, Morten Brodersen via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>> Hi Keno,
>>
>> I am talking about runtime. The performance of the generated machine
>> code. Not the time it takes to lower the IR to machine code.
>>
>> We typically only JIT once (taking a few secs) and then run the generated
>> machine code for hours. So the JIT time (IR -> machine code) doesn't impact
>> us.
>>
>> Cheers
>> Morten
>>
>> On 05/02/16 15:58, Keno Fischer wrote:
>>
>> Actually, reading over all of this again, I realize I may have made the
>> wrong statement. The runtime regressions we see in julia are actually
>> regressions in how long LLVM itself takes to do the compilation (but since
>> it happens at run time in the JIT case, I think of it as a regression in
>> our running time). We have only noticed occasional regressions in the
>> performance of the generated code (which we are in the process of fixing).
>> Which kind of regression are you talking about, time taken by LLVM or time
>> taken by the LLVM-generated code?
>>
>> On Thu, Feb 4, 2016 at 11:44 PM, Rafael Espíndola <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> On 4 February 2016 at 22:48, Morten Brodersen via llvm-dev
>>> <llvm-dev at lists.llvm.org> wrote:
>>> > Hi Rafael,
>>> >
>>> > Not easily (llc).
>>> >
>>> > Is there a way to make MCJit not use the large code model when JIT'ing?
>>> >
>>>
>>> I think Davide started adding support for the small code model.
>>>
>>> Cheers,
>>> Rafael
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>
>>
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