Significantly clean up parsing of instructions.  This exceptionizes and
simplifies the control flow a bit.  This provides a small (~3%) speedup,
but it's primarily a cleanup exercise.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8983 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed