[libcxx-commits] [libcxx] [llvm] [libc++] Optionally support filecheck-based tests (PR #165769)

[Nikolas Klauser via libcxx-commits]

philnik777 wrote:

> > The problem is that AFAICT, LLVM's FileCheck requires configuring the LLVM project as a whole and building a ton of things we don't need for the runtimes. I wouldn't even be surprised if it didn't build on some smaller platforms that we target.
> 
> It does require configuring LLVM, but I'm not sure that requires much more than configuring libc++. Looking at it right now, building just FileCheck takes 188 build steps. It looks like it's just LLVM Support and FileCheck itself, which I feel is reasonably small.

libc++ Takes 173 steps (excluding copying headers), so you'd basically be looking at doubling the build time. It's not definitely unreasoable, since libc++ is relatively quick to build, but still a lot worse than 188 steps might sound at first. Anyways, I think the much bigger problem would be that we'd create a circular dependency between the runtimes build and the llvm build.

> From what I understand, this is primarily intended to test codegen. For that, we probably want to ensure we're testing with clang so that we have at least some control over the actual codegen which should imply getting FileCheck working is possible.

That's the primary reason, but I'd also really like to add tests for our clang-tidy checks with this.

https://github.com/llvm/llvm-project/pull/165769