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

[Simon Pilgrim via cfe-commits]

https://github.com/RKSimon commented:

@phoebewang _MM_FROUND_CUR_DIRECTION now only fails in strict mode if we don't have a lossless truncation - is that what you were after?

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