[clang] [llvm] [X86][APX] Remove CF feature from APXF and Diamond Rapids (PR #153751)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> "CF" is a hardware feature; it's incredibly confusing to just pretend it doesn't exist because it's slow. If you need to adjust codegen, add a separate feature TuningSlowCF or something.

Although it's a hardware feature, it's fully under software control due to it's auto generated. So we cannot treat it as pure hardware feature. We usually use Tuningxxx due to hardware defects, which implies some hardware preform good while some bad. But here the problem is we haven't fully address regression to make it a net profit for performance.

https://github.com/llvm/llvm-project/pull/153751