NativeAOT: Removed LLVM ObjWriter and LLVM dependency

[TIHan]

Now that C# ObjWriter has had a few months to bake, it's time to get rid of the LLVM ObjWriter completely. Briefly talked to @filipnavara about removing the LLVM ObjWriter and he is feeling confident with the C# implementation.

This totally removes the LLVM ObjWriter from the repo. This includes removing the package dependencies and any mention of LLVM ObjWriter in the docs. NativeAOT will not rely on LLVM anymore, with the exception of using coredistools for dev work.

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[TIHan]

cc @agocke @MichalStrehovsky @jkotas @filipnavara

[MichalPetryka]

Does this also remove the dependency of StripSymbols on LLVM?

[TIHan]

Does this also remove the dependency of StripSymbols on LLVM?

It only removes the LLVM ObjWriter dependency. What is StripSymbols in this context? I saw there is iOSStripSymbols - are we using LLVM for this?

[MichalStrehovsky]

Resolves #74505
Resolves #75636

Does this also remove the dependency of StripSymbols on LLVM?

StripSymbols doesn't depends on LLVM. It depends on some stripping tool, be it from binutils or LLVM. This doesn't affect that. The binary we're stripping is produced by the native linker, not object writer, and we still run the native linker and have no plans to replace that.

[MichalStrehovsky]

What's the plan for the object writer in the LLVM repo? Do we need to delete it, or will it be dropped next time LLVM is upgraded?

[MichalStrehovsky]

🎈🎈 🥳

[am11]

Congrats! Huge kudos to @filipnavara. 🎉

cc @shushanhf, @clamp03, @gbalykov, new platforms can skip the llvm objwriter and directly implement it in C#.

[shushanhf]

Congrats! Huge kudos to @filipnavara. 🎉

cc @shushanhf, @clamp03, @gbalykov, new platforms can skip the llvm objwriter and directly implement it in C#.

@am11 Thanks very much.
We had an initial version Native-AOT for LoongArch64 within our local runtime.

[filipnavara]

@am11 Thanks very much. We had an initial version Native-AOT for LoongArch64 within our local runtime.

Would be something nice to share. I already looked into RV64 support and how more code sharing can be achieved between platforms and NativeAOT/CoreCLR.

[shushanhf]

@am11 Thanks very much. We had an initial version Native-AOT for LoongArch64 within our local runtime.

Would be something nice to share. I already looked into RV64 support and how more code sharing can be achieved between platforms and NativeAOT/CoreCLR.

I plan to push a PR after half a year as waiting LLVM amending some LA64's features and we also amend the Native-AOT.

[TIHan]

What's the plan for the object writer in the LLVM repo? Do we need to delete it, or will it be dropped next time LLVM is upgraded?

We should keep the branch, but not update it any further.

[am11]

We should keep the branch

It was merged to dotnet/llvm-project's main. Even if we delete it from main, it will stay in git history forever. imo, it's better to clean it up and remove the associated packaging infra from that repo's main to avoid confusions.

[TIHan]

It was merged to dotnet/llvm-project's main.

Oh, interesting. That's kind of a bummer. I guess we will remove it.

[TIHan]

Failures are #99725 and unrelated to this PR. Merging.

Thank you again everyone, especially @filipnavara for putting so much effort and thought into this work!