[llvm] [X86] Narrow BT/BTC/BTR/BTS compare + RMW patterns on very large integers (PR #165540)

[Augie Fackler via llvm-commits]

durin42 wrote:

We're chasing a breakage in our Rust toolchain that has bisected to this too, though I don't yet have enough to reduce a public test case.

https://github.com/llvm/llvm-project/pull/165540