Reapplied D7816 & rL230177 & rL230278 - with an additional fix toensure that the smallest build vector input scalar type is always used. Additional (crash) test cases already committed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230388 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed