[LLVMdev] create dummy function

[blah32]

What exactly is M in that code you posted?



Oleg Knut wrote:
> 
> Thank you very much for you help, Renato!
> 
> I read through paper you referred and also this document -
> http://llvm.org/docs/tutorial/JITTutorial1.html
> 
> Following these instructions to create successful function I run into
> some problems:
> 1) llvm::getGlobalContext() does not exists anymore? "llvm/LLVMContext.h"
> too?
> 2) creating instance of IRBuilder don't require template (from
> tutorial paper - IRBuilder<> builder(block))
> 
> So, I believe this is just outdated information? I think it just need
> some quick attention with getting materials up to date.
> 
> In the end I got following code, that satisfy my needs:
> 
> 			llvm::Constant* c = M.getOrInsertFunction(dummyFunctionName,
> F.getFunctionType());
> 			llvm::Function* dummy = llvm::cast<llvm::Function>(c);
> 			dummy->setLinkage(llvm::Function::ExternalLinkage);
> 			dummy->setCallingConv(llvm::CallingConv::C);
> 			llvm::BasicBlock* block = llvm::BasicBlock::Create("entry", dummy);
> // no context needed
> 			llvm::IRBuilder builder(block); // no need in <>
> 			builder.CreateRetVoid();
> 
> Cheers,
> Oleg.
> 
> 2009/11/5 Renato Golin <rengolin at systemcall.org>:
>> 2009/11/5 Oleg Knut <oleg77 at gmail.com>:
>>> Hello,
>>> I have a simple question. How to create "dummy" function which will
>>> have no functionality behind (return nothing and do nothing)?
>>> Currently I'm trying to do this:
>>>
>>> llvm::Constant* c = Module.getOrInsertFunction("dummy",
>>> FunctionThatNeedsToBeReplaced.getFunctionType());
>>> llvm::Function* dummy = llvm::cast<llvm::Function>(c);
>>
>> Hi Oleg,
>>
>> Every function needs a BasicBlock, even if the basic block just
>> contains a return.
>>
>> The only reason to create a function without a basic block is when the
>> function is extern'd and imported via JIT, but I guess it's not what
>> you're attempting.
>>
>> Try this presentation and let me know if it's helpful:
>>
>> http://www.systemcall.org/rengolin/stuff/compiler/download/LLVM-pet-project.pdf
>>
>> cheers,
>> --renato
>>
>> Reclaim your digital rights, eliminate DRM, learn more at
>> http://www.defectivebydesign.org/what_is_drm
>>
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