llvm dev - Jan 2020 - Moving to ORCv2 - Where are my global constructors and destructors?

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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+Lang Hames <lhames at gmail.com> 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
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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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<mailto:lhames at gmail.com> 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<mailto: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
_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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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