[PATCH] Added InstCombine transformation for combining two instructions icmp slt/sle/ult/ule/sge/sgt/uge/ugt (ashr/lshr (Const2) %A), (Const1)

[David Majnemer]

Untestable code makes this harder to understand, I'd simply `assert` that those states are unreachable.

http://reviews.llvm.org/D5518