[llvm-dev] Since MCJIT I can't get libm functions to work

[Alex Denisov via llvm-dev]

Hi Frank,

If I am not mistaken it doesn't look in the whole process space by default.
Please, try loading all the symbols explicitly:

	sys::DynamicLibrary::LoadLibraryPermanently(nullptr);

If it doesn't help, then you may try compiling your host program with -rdynamic, otherwise dlsym may not see all the symbols. At least it was the case for me on Linux.

I hope it helps.

Cheers,
Alex.

> On 28. Jun 2018, at 21:40, Frank Winter via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> I am upgrading our JIT application to use LLVM 6.0.0, and with this transition I am making the move to use the new MCJIT facility.
> 
> A problem I am encountering is that the math functions from libm are not resolved/found. I am using the lambda resolver from the KaleidoscopeJIT class which first searches the present modules and, if that is unsuccessful, continues the search in the whole process space.
> 
> The generated modules would declare external functions like
> 
> declare float @cosf(float)
> 
> and would call it like:
> 
>   %17 = call float @cosf(float %16)
> 
> The datalayout is set to
> 
> target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> 
> The code snippet that adds the module is pretty much from the JIT tutorial:
> 
>       auto Resolver = llvm::orc::createLambdaResolver(
>                               [&](const std::string &Name) {
>                             if (auto Sym = CompileLayer.findSymbol(Name, false))
>                               return Sym;
>                             return llvm::JITSymbol(nullptr);
>                               },
>                               [](const std::string &Name) {
>                             if (auto SymAddr =
> llvm::RTDyldMemoryManager::getSymbolAddressInProcess(Name))
>                               return llvm::JITSymbol(SymAddr, llvm::JITSymbolFlags::Exported);
>                             return llvm::JITSymbol(nullptr);
>                               });
> 
>       cantFail(CompileLayer.addModule(std::move(M),
>                       std::move(Resolver)));
> 
> When running the program I receive the following error:
> 
> LLVM ERROR: Program used external function 'cosf' which could not be resolved!
> 
> This is on an Intel i7 CPU with LLVM targets configured as "X86".
> 
> Adding the '-lm' and '-ldl' option to the linker command that links the final program doesn't help. (I even called the 'cosf' function by hand in the host code to make sure it is mapped - didn't change the behavior of the MCJIT resolver.)
> 
> Any ideas?
> 
> 
> Best wishes,
> 
> Frank
> 
> 
> 
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