[llvm] r239035 - Include BPF target in CMake builds.

wow :slight_smile:
this is what I wanted to propose for the last few months.
I had a chat with Chandler about graduating BPF backend
from experimental, but I want to make sure everyone is ok
before proceeding.
Current status of it:
- running on x64, arm64, s390 architectures
- projects that use it: perf, tc, ovs
- there are few front-ends in the works:
one is translating language X to C and then using clang/llvm,
another is generating llvm IR directly,
yet another is using clang rewriter to augment C language
for tracing/networking needs.
one project tried to hack clang overall and was abandoned.
- I've seen people embedding binary llc with bpf support
in their github projects.
- broken llvm build with bpf backend was reported many
times with few folks even provided simple patches to unbreak it.
- we've started to prepare buildbot specific to bpf, but hit
configuration issues with zorg. Hopefully it will be functional soon.
- as far as I can see all across the board api refactoring that
was done by a bunch of people over the last 5 month
didn't cause any problems for them or for the backend

bpf backend has been in-tree since January and has enough
users, so I think it's time to graduate it from experimental.
Honestly I was surprised to see this patch... I was hoping
it will be my honors to do it :wink:

You were correct in your earlier assumption, this shouldn’t have been added by default yet.

I’m going to go ahead and revert this patch in a bit unless someone tells me not to bother, and you can propose your patch to do, essentially, the same thing with the rationale from this message if you’d like.

FWIW I’m not against it, you’ve been an active maintainer and the BPF port hasn’t been terrible to update (from looking at the patches) or keep updated (in the few occasions I’ve done it).

-eric

Sorry for the mistake. I noticed that clang-query was complaining about missing build commands in the BPF target. After investigating it and finding that enabling it didn't break things, I concluded that someone had forgotten the cmake build as occasionally happens and thought it was an obvious fix.

One small suggestion to avoid this in the future: When an experimental target is added, could we make it policy to mention experimental targets in a comment next to the default target list.

FWIW, buildbot hasn't sent me any significant failures from the commit. Just three transient failures on the ppc64le buildbots and one more on sanitizer-x86_64-linux-autoconf.