Update compiler-rt with clang?

[kripken]

See

#24160 (comment)

By leaving compiler-rt on older versions, we risk breakage like with fcoverage. So if we want to support those features, it seems we don't have a choice but to update compiler-rt to tip of tree constantly.

Is that a lot of work, though?

[sbc100]

Since basically forever we have been shipping tip-of-tree clang/llvm with stable/pinned version of the llvm libraries (libc++, libc++abi, compiler-rt).

However it seems that using an out-of-sync compiler-rt like this was probably never really a supported thing to do. See llvm/llvm-project#190708 (comment).

So going forward I suppose we need to keep compiler-rt more up-to-date than we have been. We maybe don't need to update it daily like we do with llvm but at least periodically, and not just every time there is a stable llvm release.

@dschuff does this make sense to you? How have we gotten away with this behaviour for so long I wonder?

[aheejin]

We are due for LLVM 22 library updates anyway. Would updating to 22, meaning close enough version from ToT, work? Or does this have to be ToT? I don't really know what "raw profile format version" is, but given that its number is only 11, it seems this doesn't change very often.

[sbc100]

The change in question just landed 2 days ago so I guess not? I guess the 22 branch was cut a while back?