[LLVMdev] Runtime JIT: passing function pointers as values?

[Chris Lattner]

On Dec 1, 2007, at 7:32 AM, Benjamin Smedberg wrote:

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> I'm a LLVM newbie who's started experimenting with the JIT, and I  
> have a
> couple questions relating to LLVM and the runtime JIT: I'm going to  
> post
> them as separate messages to avoid getting threads tangled up.

Ok.

> I want to call a C++ function from a function that was JITted at  
> runtime.
> I'm starting with HowToUseJIT.cpp as a base for experimentation. Is it
> possible to take the address of the C++ function and pass it to the  
> JIT
> directly as a value, rather than referencing the function by a  
> symbolic name?

Sure, just cast the pointer value to an integer type (in your C++  
code) then pass that value to ConstantInt::get(...);

Then pass the resultant Constant* to ConstantExpr::getIntToPtr(C,  
<yourpointertype>);

You now have an LLVM Constant* for your pointer.

-Chris