[lli] Fix crash with --no-process-syms on MinGW

[jeremyd2019]

In this case, J->getProcessSymbolsJITDylib() returns a NULL pointer. In order to make sure __main is still defined, add the symbol to J->getMainJITDylib() instead in that case. This returns a reference and thus cannot be NULL.

Fixes #143080

[jeremyd2019]

With this change, llvm/test/ExecutionEngine/OrcLazy/emulated-tls.ll succeeds on Cygwin (it probably would on MinGW also), where before it crashed. I was originally just going to add if (J->getTargetTriple().isOSCygMing() && J->getProcessSymbolsJITDylib()) but that then caused the emulated-tls.ll test to fail due to __main also being undefined.

[lhames]

The process-symbols dylib is the right place for __main to go usually, it's only when we pass -no-process-syms that we'd want to put it anywhere else. (Side note: If / when we make Platforms mandatory we should put it in the Platform dylib instead).

Would you mind changing this to:

auto &WorkaroundJD = J->getProcessSymbolsJITDylib()
    ? *J->getProcessSymbolsJITDylib()
    : J->getMainJITDylib();
ExitOnErr(WorkaroundJD.define(
        orc::absoluteSymbols({{J->mangleAndIntern("__main"),
                               {orc::ExecutorAddr::fromPtr(mingw_noop_main),
                                JITSymbolFlags::Exported}}})));

[jeremyd2019]

I had done something like that in a previous attempt, but your suggestion is cleaner than what I was trying with a pointer.

[lhames]

LGTM. Thanks @jeremyd2019!

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-hip-vega20 running on hip-vega20-0 while building llvm at step 2 "update-annotated-scripts".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/123/builds/24552

Here is the relevant piece of the build log for the reference

Step 2 (update-annotated-scripts) failure: update (failure)
git version 2.34.1
fatal: unable to access 'https://github.com/llvm/llvm-zorg.git/': Could not resolve host: github.com
fatal: unable to access 'https://github.com/llvm/llvm-zorg.git/': Could not resolve host: github.com