[llvm-dev] Moving to ORCv2 - Where are my global constructors and destructors? + More information

[Lang Hames via llvm-dev]

HI Bjoern,

Thanks for your patience — It’s going to take some time for me to get through all the emails that built up while I was away last month.

I’m glad you found a workaround for your issue, and thanks for pointing out the runConstructors problem. I’m working on a big update to the static initializers/deinitializers problem which I hope to land in the next week or so. Hopefully that will address this issue.

— Lang.

Sent from my iPad

> On Jan 7, 2020, at 6:13 AM, Gaier, Bjoern <Bjoern.Gaier at horiba.com> wrote:
> 
> 
> Sorry for the spam, but I made some progress with my issue and wanted to share what I found out.
>  
> I tried the following line before adding my module to the LLJIT:
> “this->mainModule->getFunction("_GLOBAL__sub_I_VectorBIOS.cpp")->isDiscardableIfUnused();” This actually returned true
> So I tried the following line:
> “this->mainModule->getFunction("_GLOBAL__sub_I_VectorBIOS.cpp")->setLinkage(llvm::GlobalValue::ExternalLinkage);”
> Now I was able to find the function and execute the global constructor. For a workaround this works for me.
> However, running LLJITs ‘runConstructors’ does still not work, they are still empty.
>  
>  
> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Gaier, Bjoern via llvm-dev
> Sent: 06 January 2020 15:02
> To: David Blaikie <dblaikie at gmail.com>; Lang Hames <lhames at gmail.com>
> Cc: llvm-dev at lists.llvm.org
> Subject: Re: [llvm-dev] Moving to ORCv2 - Where are my global constructors and destructors?
>  
> Is there a code example or maybe a documentation about this subject? Sadly it is an important part of my project to get the addresses of the constructors and destructors.
> I really ran out of ideas though, every time when I try to look them up, they seem to be gone already .w.
>  
> From: David Blaikie <dblaikie at gmail.com> 
> Sent: 19 December 2019 20:52
> To: Gaier, Bjoern <Bjoern.Gaier at horiba.com>; Lang Hames <lhames at gmail.com>
> Cc: llvm-dev at lists.llvm.org
> Subject: Re: [llvm-dev] Moving to ORCv2 - Where are my global constructors and destructors?
>  
> +Lang Hames owner/author of the ORC JIT (though I think he's out of office at the moment, so replies from him might be delayed).
> 
> I believe there's a way to wire up the global ctors, but I don't know the details unfortunately - perhaps someone else will chime in if/before Lang gets a chance.
>  
> On Thu, Dec 19, 2019 at 5:53 AM Gaier, Bjoern via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> Heyho,
>  
> Recently I tried out the ORCv2 JIT, especially the LLJIT. I gotta say, that I really like the new interface and the way you use it! However there is one thing I’m missing. I wrote a small bit code file, which should force having a global constructor.
>  
> int wuff();
>  
> __declspec(noinline) int miau()
> {
>        printf("Huhuhu");
>        return wuff();
> }
>  
> const int x = miau();
>  
> When I parse this IR file in my JIT and go through the ‘globals()’ of the llvm::Module, then I will encounter a symbol with the following name:
> “_GLOBAL__sub_I_VectorBIOS.cpp” where VectorBIOS.cpp was the name of the source file I compiled to the bit code.
>  
> I then wanted to get the address of that symbol - from the MCJIT times I remember, that those functions are the global constructors, but when calling lookup on that name, I was not able to find the symbol.
> So I tried a different way:
> llvm::GlobalVariable *var = module->getNamedGlobal("llvm.global_ctors");
> if(var)
> {
>        llvm::ConstantArray *InitList = (llvm::ConstantArray*)var->getInitializer();
>        for(unsigned int n = 0; n < InitList->getNumOperands(); n++)
>        {
>              llvm::ConstantStruct *CS = (llvm::ConstantStruct*)InitList->getOperand(n);
>              if(!CS)
>              {
>                     continue;
>              }
>  
>              llvm::Constant *FP = CS->getOperand(1);
>              if(FP->isNullValue())
>                     continue;
>  
>              llvm::ConstantExpr *CE = (llvm::ConstantExpr*)FP;
>              if(CE->isCast())
>              {
>                     FP = CE->getOperand(0);
>              }
>  
>              ((llvm::Function*)FP)->getName();
>        }
> }
> I then printed the name of the llvm::Function but it was exactly the name I expected “_GLOBAL__sub_I_VectorBIOS.cpp”. This code was executed before I added module to the JIT.
> For various reasons I wanted to store the address to the constructor – so I don’t want to call the LLJIT runConstructor – simply because I want to execute those functions later, when the LLJIT does not exist anymore.
>  
> I hope someone can help me with this…
>  
> Kind Greetings
> Björn
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Takeshi Fukushima. Junichi Tajika
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> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Takeshi Fukushima. Junichi Tajika
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