Implemented subtraction

src/build/asm/Assembler.go

@@ -30,10 +30,13 @@ func (a *Assembler) Finalize() ([]byte, []byte) {
 		case ADD:
 			switch operands := x.Data.(type) {
 			case *RegisterNumber:
-				code = x64.AddRegNum8(code, operands.Register, uint8(operands.Number))
+				code = x64.AddRegNum(code, operands.Register, operands.Number)
+			}
 
-			case *RegisterRegister:
-				// code = x64.AddRegReg64(code, operands.Destination, operands.Source)
+		case SUB:
+			switch operands := x.Data.(type) {
+			case *RegisterNumber:
+				code = x64.SubRegNum(code, operands.Register, operands.Number)
 			}
 
 		case CALL:

src/build/asm/Instructions.go

@@ -3,7 +3,7 @@ package asm
 import "git.akyoto.dev/cli/q/src/build/cpu"
 
 // AddRegisterNumber adds a number to the given register.
-func (a *Assembler) AddRegisterNumber(reg cpu.Register, number uint64) {
+func (a *Assembler) AddRegisterNumber(reg cpu.Register, number int) {
 	a.Instructions = append(a.Instructions, Instruction{
 		Mnemonic: ADD,
 		Data: &RegisterNumber{
@@ -13,8 +13,19 @@ func (a *Assembler) AddRegisterNumber(reg cpu.Register, number uint64) {
 	})
 }
 
+// SubRegisterNumber subtracts a number from the given register.
+func (a *Assembler) SubRegisterNumber(reg cpu.Register, number int) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: SUB,
+		Data: &RegisterNumber{
+			Register: reg,
+			Number:   number,
+		},
+	})
+}
+
 // MoveRegisterNumber moves a number into the given register.
-func (a *Assembler) MoveRegisterNumber(reg cpu.Register, number uint64) {
+func (a *Assembler) MoveRegisterNumber(reg cpu.Register, number int) {
 	a.Instructions = append(a.Instructions, Instruction{
 		Mnemonic: MOVE,
 		Data: &RegisterNumber{

src/build/asm/Mnemonic.go

@@ -10,6 +10,7 @@ const (
 	LABEL
 	MOVE
 	RETURN
+	SUB
 	SYSCALL
 )
 
@@ -34,6 +35,9 @@ func (m Mnemonic) String() string {
 	case RETURN:
 		return "return"
 
+	case SUB:
+		return "sub"
+
 	case SYSCALL:
 		return "syscall"
 	}

src/build/asm/RegisterNumber.go

@@ -9,7 +9,7 @@ import (
 // RegisterNumber operates with a register and a number.
 type RegisterNumber struct {
 	Register cpu.Register
-	Number   uint64
+	Number   int
 }
 
 // String returns a human readable version.