[llvm] [SimplifyCFG] Avoid threading for loop headers (PR #151142)

[Arne Stenkrona via llvm-commits]

ArneStenkrona2 wrote:

I took a look at the checks https://github.com/llvm/llvm-project/commit/ea2f5395b1acdc6eaf69a79b7660d7fa7d08c271
2 out of 67 show failures.
In [clang-ppc64-aix](https://lab.llvm.org/buildbot/#/builders/64/builds/5491) they all seem to be this assertion:
`Assertion failed: V.getBitWidth() == C.getIntWidth(type) && "Integer type is not the correct size for constant."`
I don't see how my patch could cause type mismatches since it only deals with BBs.

In [mlir-rocm-mi200](https://lab.llvm.org/buildbot/#/builders/177/builds/19107) they all seem to be an ld error:
`ld.lld: error: unknown abi version: `
To my eyes this is certainly unrelated.

To my eyes these don't look like things the patch could cause so I will assume them to not be regressions. Not sure how to validate that best. When trying to run this locally llvm-lit reports the failing tests I've tried so far as unsupported. I also looked at the  post-checks for the parent commit but seems like different checks are run.

I will say for now that this is unrelated to this patch. If anyone here disagrees feel free to ping me and I'll do my best to take a deeper look.

https://github.com/llvm/llvm-project/pull/151142