[LLVMdev] LLVM 3.3 JIT code speed

[Stéphane Letz]

Hi,

Our DSL LLVM IR emitted code (optimized with -O3 kind of IR ==> IR passes) runs slower when executed with the LLVM 3.3 JIT, compared to what we had with LLVM 3.1. What could be the reason? 

I tried to play with TargetOptions without any success…

Here is the kind of code we use to allocate the JIT:

    EngineBuilder builder(fResult->fModule);
    builder.setOptLevel(CodeGenOpt::Aggressive);
    builder.setEngineKind(EngineKind::JIT);
    builder.setUseMCJIT(true);
    builder.setCodeModel(CodeModel::JITDefault);
    builder.setMCPU(llvm::sys::getHostCPUName());
    
    TargetOptions targetOptions;
    targetOptions.NoFramePointerElim = true;
    targetOptions.LessPreciseFPMADOption = true;
    targetOptions.UnsafeFPMath = true;
    targetOptions.NoInfsFPMath = true;
    targetOptions.NoNaNsFPMath = true;
    targetOptions.GuaranteedTailCallOpt = true;

   builder.setTargetOptions(targetOptions);
    
    TargetMachine* tm = builder.selectTarget();
    
    fJIT = builder.create(tm);
    if (!fJIT) {
        return false;
    }
    ….

Any idea?

Thanks.

Stéphane Letz