[llvm] [GitHub][workflows] Use latest clang-format version 18.1.1 (PR #85502)

[Owen Pan via llvm-commits]

owenca wrote:

I've relanded it.

> I've reverted this for now as I think it needs more discussion. https://discourse.llvm.org/t/rfc-clang-format-all-the-things/76614 is probably the most recent discussion on this, and the consensus there seems to be that we should be conservative with version upgrades due to churn.

That RFC is about formatting entire codebases, and for me there is no consensus yet even though it seems more people favor at least the latest release of clang-format when formatting entire files.

The more relevant RFC is https://discourse.llvm.org/t/rfc-clang-format-github-action/73391. It seems the consensus is to use at least the latest release of clang-format for CI.

> Unless there's a specific bug fix/feature that landed in `clang-format` that is important for in-tree use, I think we should hold off on this for now until we have a better specified project-wide policy on what to do with bumping the formatter version. If there's a compelling reason to go forward with this though, I'm not opposed to relanding. I think upgrading just to upgrade doesn't make a lot of sense currently though given the lack of project-wide policy/discussion on this topic.

There have been many bug fixes and a number of new options/features since clang-format 17.0.6. One of the new features is the support of `.clang-format-ignore` files, which can be used to ignore .td files mentioned in the RFC you linked above. There are bug fixes that fixed formatting errors in Polly. We also have a new `clang-format` style (from last November) that we can't really use unless the CI is bumped up to clang-format 18.1.1.

https://github.com/llvm/llvm-project/pull/85502