[X86] Add ISD node for masked version of CVTPS2PH.
The 128-bit input produces 64-bits of output and fills the upper 64-bits with 0. The mask only applies to the lower elements. But we can't represent this with a vselect like we normally do.
This also avoids the need to have a special X86ISD::SELECT when avx512bw isn't enabled since vselect v8i16 isn't legal there.
Fixes another instruction for PR34877.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350994 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed