[X86] Stop LowerSIGN_EXTEND_AVX512 from creating v8i16/v16i16/v16i8 vselects with a v8i1/v16i1 condition when BWI is not available.

Some of the tests in vector-shuffle-v1.ll would get into an infinite loop without this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315172 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed