[LLVMdev] Trouble using the MCJIT: "Target does not support MC emission" error

[Bruno Cardoso Lopes]

Hi Ralf,

FYI, old JIT doesn't support AVX at all, no encoding info, etc... The
only way to use AVX+JIT is using MCJIT, which contains the correct
encoding, but unfortunately the framework isn't good yet as the old
one is.

On Thu, Aug 25, 2011 at 10:12 AM, Ralf Karrenberg <Chareos at gmx.de> wrote:
> Hi Matt,
>
> I am unsure about MCJIT, but I guess the problem is the same.
> Just like when invoking llc, you need to pass the information to use AVX
> (llc -mattr=+avx).
> I guess the corresponding code should look like this:
>
>     llvm::EngineBuilder engineBuilder(module);
>     engineBuilder.setErrorStr(&eeError);
>     engineBuilder.setEngineKind(llvm::EngineKind::JIT);
>     engineBuilder.setUseMCJIT(true);
>     engineBuilder.setMCPU("corei7-avx");
>     std::vector<std::string> attrs;
>     attrs.push_back("avx");
>     engineBuilder.setMAttrs(attrs);
>     llvm::ExecutionEngine *ee = engineBuilder.create();
>
> Note that I have just today filed a bug report also related to jitted
> AVX: http://llvm.org/bugs/show_bug.cgi?id=10742
> Thus, it might very well be the case that I am also mistaken and need to
> do something different.
>
> Best,
> Ralf
>
> Am 25.08.2011 13:16, schrieb Matt Pharr:
>> I'm trying to wire up some code to use the MC-based JIT; my understanding is that it should be able to JIT AVX code (and that the regular JIT cannot).  However, I'm getting the error "Target does not support MC emission!" when I call EngineBuilder::create().  I assume that I'm just not doing something necessary for initialization, but I'm not sure what it would be--I am calling all of:
>>
>>      llvm::InitializeNativeTarget();
>>      llvm::InitializeAllTargetMCs();
>>      LLVMLinkInMCJIT();
>>      LLVMLinkInJIT();
>>
>> and the module I'm trying to load does have a reasonable target:
>>
>> target triple = "x86_64-apple-darwin11.0.0"
>>
>> I've attached a short test case that has the sequence of calls that I'm making and one of the bitcode files I'm trying to use.  I'd be happy for any guidance or suggestions.
>>
>> Thanks,
>> -matt
>>
>>
>>
>>
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-- 
Bruno Cardoso Lopes
http://www.brunocardoso.cc