In the Arm assembly parser, we first match an instruction, then call
processInstruction to possibly change it to a different encoding, to
match rules in the architecture manual which can't be expressed by the
This adds debug printing so that this process is visible when using the
To support this, I've added a new overload of MCInst::dump_pretty which
takes the opcode name as a StringRef, since we don't have an InstPrinter
instance in the assembly parser. Instead, we can get the same
information directly from the MCInstrInfo.