[LLVMdev] JIT compiled intrinsics calls is call to null pointer

[Richard Mitton]

sin/cos on Intel is an x87 FPU instruction, but it looks like LLVM is 
generating SSE code instead, which relies on a library function for 
sin/cos/pow/etc.

Richard Mitton
richard at codersnotes.com

On 09/19/2013 01:57 AM, Taco H. in den Bosch wrote:
> Hi Andrew,
>
> this sounded a plausible explanation, because the X86 processor does 
> not have an instruction to calculate the power function.
>
> So I tried the llvm.sin.f32 intrinsic, as the X86 processor family 
> does have an instruction for that, but I still get the same problem. 
> While you may still be right, there is at least something else going 
> on as well.
>
> Thanks for your input, though.
>
> Taco.
>
> ------------------------------------------------------------------------
> *From*: "Andrew MacPherson" <andrew.macp at gmail.com>
> *Sent*: Thursday, September 19, 2013 10:36 AM
> *To*: taco at heddesit.nl
> *Cc*: llvmdev at cs.uiuc.edu
> *Subject*: Re: [LLVMdev] JIT compiled intrinsics calls is call to null 
> pointer
>
> Hi Taco,
>
> We had a similar issue where a math intrinsic was being converted to a 
> call to null and it turned out to be because the system didn't support 
> the CPU instructions for the operation so the intrinsic used a call to 
> the library function (pow in your case). However because we weren't 
> expecting this math function to be looked up by MCJIT in our 
> JITMemoryManager::getPointerToNamedFunction() we weren't making it 
> available and it was returning null.
>
> Not sure if this is relevant to your case but maybe it'll help point 
> you in the right direction.
>
> Cheers,
> Andrew
>
>
> On Wed, Sep 18, 2013 at 8:32 AM, Taco H. in den Bosch 
> <taco at heddesit.nl <mailto:taco at heddesit.nl>> wrote:
>
>
>     Hi everyone,
>
>     I am trying to call an LLVM intrinsic (llvm.pow.f32), inserted
>     with the following call:
>
>     std::vector<llvm::Type *> arg_types;
>     arg_types.push_back(llvm::Type::getFloatTy(context));
>     auto function=llvm::Intrinsic::getDeclaration(module,
>     llvm::Intrinsic::pow, arg_types);
>     auto result=ir_builder->CreateCall(function, args);
>
>     When I try to execute the code generated by the JIT compiler, I
>     see that the intrinsic is not compiled into a math coprocessor
>     instruction, but in a call to a null address:
>
>     002300B8  sub esp,8
>     002300BB  movss       xmm0,dword ptr ds:[2300B0h]
>     002300C3  movss       dword ptr [esp+4],xmm0
>     002300C9  movss       xmm0,dword ptr ds:[2300B4h]
>     002300D1  movss       dword ptr [esp],xmm0
>     002300D6 call      00000000
>     002300DB  add         esp,8
>     002300DE  ret
>
>     Is there anything special that I need to do in order to be able to
>     call intrinsics, either in general or when JITting? I am either
>     doing something wrong, or forgetting to do something, but I don't
>     know what.
>
>     I am working with a Visual Studio compiled version on Windows (x86).
>
>     All hints will be appreciated, with kind regards,
>
>     Taco H. in den Bosch.
>
>
>
>
>
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