[clang] [llvm] [PowerPC] Add intrinsics for rldimi/rlwimi/rlwnm (PR #82968)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

If you run into issues using normal integer ops, please file bugs.  Most people aren't going to hand-tune their code like this; builtins like this are at best an ugly workaround.

That said, I guess I'm not strongly against adding a backdoor to force a particular instruction here.

https://github.com/llvm/llvm-project/pull/82968