Created by: egrimley
Moving a value to the zero register is a no-op but we have seen ADR XZR,... used by Node.js (libv8). Having these API functions, instrlist_insert_mov_{immed_ptrsz,instr_addr}, create no instructions potentially adds a case for the caller to handle but most uses of those functions set the last two arguments to NULL in any case. If it were a problem we could create a NOP instruction instead. Creating actual moves to XZR seems less good and would be awkward if in generating a constant value we ever used instructions that cannot target XZR.