Add helpers for getting scalar sizes of vector value types.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203526 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Calculate store mask instead of using switch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203527 91177308-0d34-0410-b5e6-96231b3b80d8