Avoid implicit conversions from MachineInstrBundleInstr to MachineInstr*
in the MSP430 backend, mainly by preferring MachineInstr& over
MachineInstr* when a pointer isn't nullable and using range-based for
There was one piece of questionable code in
NVPTXInstrInfo::AnalyzeBranch, where a condition checked a pointer
converted from an iterator for nullptr. Since this case is impossible
(moreover, the code above guarantees that the iterator is valid), I
removed the check when I changed the pointer to a reference.
Despite that case, there should be no functionality change here.