[clang] [clang] Pragma for llvm.loop.licm.disable (PR #188108)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Missing documentation in clang/docs/LanguageExtensions.rst.  Missing release note.

It's not clear to me how, exactly, we expect users to use this.  "Disabling LICM" disables the pass itself, but there are other passes which can effectively perform hosting.  So it's basically "do less hoisting", where exactly how much less is undefined.

https://github.com/llvm/llvm-project/pull/188108