release/21.x: [llvm-offload-wrapper] Fix Triple and OpenMP handling (#167580)

[dianqk]

Backport 6655681.

[dianqk]

cc @ZuseZ4

[dyung]

Is this a regression from a previous release? If so, which one? This is going to be the final release from the LLVM 21.x branch, so any issues from taking this change would not be fixed until LLVM 22 releases in about a month. And considering this is the final release of 21.x, we need to be very careful what changes are included. What would be the impact of not accepting this change for 21 and waiting for 22 instead?

[jhuber6]

Is this a regression from a previous release? If so, which one? This is going to be the final release from the LLVM 21.x branch, so any issues from taking this change would not be fixed until LLVM 22 releases in about a month. And considering this is the final release of 21.x, we need to be very careful what changes are included. What would be the impact of not accepting this change for 21 and waiting for 22 instead?

Honestly, it's more of a feature. It makes the utility more usable but it's not strictly required nor does it fix a bug. This, I believe, comes from the Rust team wanting to more easily use this utility. We usually don't backport features so it's up to you.

[ZuseZ4]

This, I believe, comes from the Rust team wanting to more easily use this utility.

Yes indeed, I had asked for it for our rustc GPU efforts in rust-lang/rust-project-goals#109
This PR had helped me with replacing the clang-linker-wrapper invocation, since in Cargo we don't generally want to call (additional) LLVM binaries. However, Joseph mentioned how I can work around it on the rust side. I didn't get to test it yet, but (worst case) we can vendor the fix for a few months on the Rust side till we get to update to LLVM-22, which will simplify our compilation pipeline anyway by quite a bit.

Since you seem a bit concerned about the timeline, I guess either fix on the Rust side is preferred, so we can go with that.

[dyung]

Hi, thanks for the explanation, but I think I am going to pass on integrating this change for the 21.x release, but 22.x is just a little over a month away so hopefully your issue gets better soon with that!