[llvm-dev] llvm interpreter does not find function defined by addGlobalMapping

[via llvm-dev]

Hi Lang,

> So: global mappings do not work in the interpreter at the moment.
This information is somewhat disappointing but, nevertheless, very helpful. Thanks! 

 I use the interpreter, because I iteratively evaluate llvm::Value objects which are constructed using previously defined (and evaluated) llvm::Value objects. It seemed to me that using the interpreter is the most straightforward way for this. I will have a look at ORC, may be it will do, too.

Cheers,
Volker


----- Original Nachricht ----
Von:     Lang Hames <lhames at gmail.com>
An:      markus.parker at arcor.de
Datum:   25.10.2016 05:27
Betreff: Re: Re: [llvm-dev] llvm interpreter does not find function defined by addGlobalMapping

> Hi Markus,
> 
> I don't know the Interpreter code well (and it's very poorly maintained)
> but from a quick inspection it doesn't seem to be inspecting the global
> mapping during external function resolution at all. The reason the code
> works on windows anyway is that (I would guess) it's an exported symbol in
> your program, and the Interpreter *does* look for those. On Linux, where
> symbols are not exported from the main binary by default, this fails.
> 
> So: global mappings do not work in the interpreter at the moment.
> 
> Is there any particular reason for you to use the interpreter? Given that
> it is poorly maintained, I would encourage you to use MCJIT instead (or,
> even better, ORC: http://llvm.org/docs/tutorial/BuildingAJIT1.html).
> 
> Cheers,
> Lang.
> 
> 
> On Mon, Oct 24, 2016 at 12:09 AM, <markus.parker at arcor.de> wrote:
> 
> >  Hi Lang,
> >
> > > What happens if you set the data layout on pModule before creating the
> > > engine?
> >
> > The output of pExecutionEngine->getDataLayout().getStringRepresentation()
> > is an empty string if I do not set the layout on pModule before creating
> > the interpreter engine. If I set the layout before, the output is the
> > specified layout. But unfortunately, the error is still there.
> >
> > Markus
> >
> > >
> > > - Lang.
> > >
> > > On Mon, Sep 19, 2016 at 5:34 AM, via llvm-dev <llvm-dev at lists.llvm.org>
> > > wrote:
> > >
> > > > Hi,
> > > >
> > > > I want to use a function defined in c(++)-code from code generated by
> > > > llvm. For this I use ExecutionEngine.addGlobalMapping(). I started
> > with
> > > > the JIT execution engine and everything worked, then I switched to
> the
> > > > interpreter engine and it stopped working, but only if compiled on a
> > > Linux
> > > > system. More precisely it works if I use
> > > >
> > > >     llvm 3.8.1 + gcc (Linux) + JIT
> > > >     llvm 3.8.0 + mingw-gcc (Windows) + JIT
> > > >     llvm 3.8.0 + mingw-gcc (Windows) + Interpreter
> > > >
> > > > But it does not work for llvm 3.8.1 + gcc (Linux) + Interpreter. In
> > that
> > > > case I get the error message "LLVM ERROR: Tried to execute an unknown
> > > > external function: testFunction." Am I using
> > > ExecutionEngine.addGlobalMapping()
> > > > in the wrong way, even it works in three out of four scenarios?
> > > >
> > > > #include <llvm/Support/TargetSelect.h>
> > > > #include <llvm/Analysis/Passes.h>
> > > > #include <llvm/Transforms/Scalar.h>
> > > > #include <llvm/Transforms/IPO/PassManagerBuilder.h>
> > > > #include <llvm/Transforms/IPO.h>
> > > > #include <llvm/IR/Verifier.h>
> > > > #include <llvm/ExecutionEngine/ExecutionEngine.h>
> > > > #include <llvm/ExecutionEngine/Interpreter.h>
> > > > #include <llvm/ExecutionEngine/MCJIT.h>
> > > > #include <llvm/ExecutionEngine/GenericValue.h>
> > > > #include <llvm/IR/LegacyPassManager.h>
> > > > #include <llvm/IR/IRBuilder.h>
> > > >
> > > > extern "C" double testFunction(){
> > > >   return 42.0;
> > > > }
> > > >
> > > > int main() {
> > > >   // initialization needed for JIT
> > > >   llvm::InitializeNativeTarget();
> > > >   llvm::InitializeNativeTargetAsmPrinter();
> > > >   llvm::InitializeNativeTargetAsmParser();
> > > >
> > > >   llvm::LLVMContext &context(llvm::getGlobalContext());
> > > >   llvm::Module *pModule = new llvm::Module("a module", context);
> > > >
> > > >   // Here the EngineKind-flag decides if JIT or interpreter is used.
> > > >   auto pExecutionEngine = llvm::EngineBuilder(std::
> > > > unique_ptr<llvm::Module>(pModule)
> > > >     ).setEngineKind(llvm::EngineKind::Interpreter).create();
> > > >   pModule->setDataLayout(pExecutionEngine->getDataLayout());
> > > >
> > > >   // declaration of the c function.
> > > >   std::vector<llvm::Type *> noArgTypes;
> > > >   llvm::FunctionType* ft = llvm::FunctionType::get(llvm::
> > > > Type::getDoubleTy(context),noArgTypes, false);
> > > >   auto pFunction = llvm::Function::Create(ft,
> > > llvm::Function::ExternalLinkage,
> > > > "testFunction",pModule);
> > > >   pExecutionEngine->addGlobalMapping(pFunction,
> > reinterpret_cast<void*>(&
> > > > testFunction));
> > > >
> > > >   // generation of llvm code
> > > >   auto pBlock = llvm::BasicBlock::Create(context, "evaluation");
> > > >   llvm::IRBuilder<> builder(context);
> > > >   builder.SetInsertPoint(pBlock);
> > > >
> > > >   // code for call of the c function.
> > > >   auto pFunction2 = pModule->getFunction("testFunction");
> > > >   auto temp = builder.CreateCall(pFunction2,
> > std::vector<llvm::Value*>(),
> > > > "calltmp");
> > > >   builder.CreateRet(temp);
> > > >
> > > >   // generation of the llvm function calling the c function
> > > >   llvm::FunctionType* ftWrapper = llvm::FunctionType::get(llvm::
> > > > Type::getDoubleTy(context),noArgTypes, false);
> > > >   auto pWrapperFunction = llvm::Function::Create(ftWrapper,
> > > > llvm::Function::ExternalLinkage, "AFunction",pModule);
> > > >   pWrapperFunction->getBasicBlockList().push_back(pBlock);
> > > >
> > > >   // calling the generated llvm function
> > > >   pExecutionEngine->finalizeObject();
> > > >   pExecutionEngine->runFunction(pWrapperFunction,std::vector<
> > > > llvm::GenericValue>());
> > > > }
> > > >
> > > > Thanks for any help,
> > > > Markus
> > > > _______________________________________________
> > > > LLVM Developers mailing list
> > > > llvm-dev at lists.llvm.org
> > > > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> > > >
> > >
> >
>