This patch converts the old SHR instruction into two instructions,
AShr (Arithmetic) and LShr (Logical). The Shr instructions now are not
dependent on the sign of their operands.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31542 91177308-0d34-0410-b5e6-96231b3b80d8