Implemented simple expressions

src/build/asm/Instructions.go

@@ -13,6 +13,17 @@ func (a *Assembler) RegisterNumber(mnemonic Mnemonic, reg cpu.Register, number i
 	})
 }
 
+// RegisterRegister adds an instruction using two registers.
+func (a *Assembler) RegisterRegister(mnemonic Mnemonic, left cpu.Register, right cpu.Register) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: mnemonic,
+		Data: &RegisterRegister{
+			Destination: left,
+			Source:      right,
+		},
+	})
+}
+
 // MoveRegisterRegister moves a register value into another register.
 func (a *Assembler) MoveRegisterRegister(destination cpu.Register, source cpu.Register) {
 	a.Instructions = append(a.Instructions, Instruction{