[clang] [X86][Clang] Allow constexpr evaluation of F16C CVTPS2PH intrinsics (PR #162295)

[Eric Xu via cfe-commits]

ericxu233 wrote:

> I just meant the AVX512F/VL variants vcvtps2ph_mask / vcvtps2ph256_mask / __builtin_ia32_vcvtps2ph512_mask - those should just require additional handling for the getNumArgs() == 4 masked variant.
> 
> But I'm happy for this just to focus on the F16C cases if you prefer to iterate in later PRs.

I apologize for the late response, and thanks for the flexibility! Yes, I would prefer to iterate in later PRs since I am a little bit pressed for time lately. Let me know if there are any additional items in the code that I need to address.

https://github.com/llvm/llvm-project/pull/162295