When a combine twiddles an extract_vector, care should be take to preserve
the type of the index operand. No luck extracting a reasonable testcase,
unfortunately.
rdar://11391009
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156419 91177308-0d34-0410-b5e6-96231b3b80d8