[LLVMdev] create dummy function

[Oleg Knut]

M is llvm::Module instance.

Cheers,
Oleg.

2009/11/15 blah32 <blah32 at live.com>:
>
> 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 So, I believe this is just outdated information?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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>
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