llvm dev - Nov 2017 - shadow-stack and llvm_gc_root_chain linkage when using JIT

What is the expected way of gaining access to llvm_gc_root_chain when using
JIT?

The only way I could figure out was this:

        fpm->add(llvm::createShadowStackGCLoweringPass());
        fpm->doInitialization();
        fpm->run(*f);
        // EPIC KLUDGE
        auto wrong = _module->getNamedGlobal("llvm_gc_root_chain");
        auto right = new llvm::GlobalVariable(
            *_module.get(),
            wrong->getType()->getContainedType(0),
            false, // variable
            llvm::GlobalVariable::ExternalLinkage,
            nullptr,
            "my_gc_root_chain");
        wrong->replaceAllUsesWith(right);

...which works, has a bit of a smell about it.

I cannot use the LLVM's definition from my GC because this is running in
JIT.

I gave up trying to give it external linkage before
shadow-stack-gc-lowering-pass since it makes a unique struct type that I
cannot match (or I'm misunderstanding something badly), causing Stores to
fail when using my definition.

Cheers,

 -- nikodemus
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