How to build llc individually?

Beginners
#1

I’m trying to generate the object file while building my IR module. I found the tool llc, but actually it was an executable file which I can’t call it from my llvm program directly.

Later I pull the llc.cpp file from the llvm source tree, along with the cmakelist.txt. But when I finally fix some trivial undefined code and comile it, It says lots of function not found.
Just like

initializeCore’ was not declared in this scope
   76 |     initializeCore(*Registry);
      |     ^~~~~~~~~~~~~~
odegen.cpp:77:5: error: ‘initializeCodeGen’ was not declared in this scope
   77 |     initializeCodeGen(*Registry);
      |     ^~~~~~~~~~~~~~~~~
codegen.cpp:78:5: error: ‘initializeLoopStrengthReducePass’ was not declared in this scope
   78 |     initializeLoopStrengthReducePass(*Registry);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
codegen.cpp:79:5: error: ‘initializeLowerIntrinsicsPass’ was not declared in this scope
   79 |     initializeLowerIntrinsicsPass(*Registry);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...

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I’ve comment the below header because I can’t find it when I compile out of tree.

llvm/CodeGen/CommandFlags.inc

the complete header file and the cmake is pasted
header : Ubuntu Pastebin
cmakelist Ubuntu Pastebin

Alternatively, extract the llc.cpp file and compile it out of tree is not a good idea.
I wonder whether I could compile the llc as a library file for me to call the function directly, like .so on linux. If possible, is there any idea to modify the original llc cmakelists?

Thanks in advance.

#2

Depending on what you want to achieve, you could call llc using something like popen(3).

Edit: If you want to do it in a less hacky way, a good starting point would be to look at how the object file generation is handled in LLVMTargetMachineEmit from the C API. In my experience, the C API often strips down the most difficult parts of the infrastructure that may be spread all over the place in the main repository.

#3

Thanks a lot. Diving into the LLVMTargetMachineEmit related API, I finally find the addPassesToEmitFile C API works.