modBits describes what the ModRM.mod bits are used for.

Addr is an address used by an instruction. It may represent a register, or data.

AddrType is the type of an Addr. An address can be a register or data. The usual use of AddrType is as an enum. However, when building the optab, it

Instruction is an amd64 asssembly instruction.

Op is an amd64 operation. Mnemonics closely follow the amd64 manual.

Program is an amd64 program.

Register is an amd64 register.

ins is a laid out Instruction. After calling make, an ins looks very similar to the laid out bytes for an op. (Passing ins to printf is helpful in deb