Simplified code

src/build/core/Compare.go

@@ -31,16 +31,16 @@ func (f *Function) Compare(comparison *expression.Expression) error {
 			return err
 		}
 
-		return f.Execute(comparison.Token, f.CPU.Output[0], right)
+		return f.ExecuteLeaf(comparison.Token, f.CPU.Output[0], right.Token)
 	}
 
-	tmp := f.CurrentScope().MustFindFree(f.CPU.General)
+	tmp := f.NewRegister()
 	err := f.ExpressionToRegister(left, tmp)
 
 	if err != nil {
 		return err
 	}
 
-	defer f.CurrentScope().Free(tmp)
+	defer f.FreeRegister(tmp)
 	return f.Execute(comparison.Token, tmp, right)
 }

src/build/core/CompileCall.go

@@ -11,8 +11,8 @@ import (
 // Registers that are in use must be saved if they are modified by the function.
 // After the function call, they must be restored in reverse order.
 func (f *Function) CompileCall(root *expression.Expression) error {
-	funcNameRoot := root.Children[0]
 	funcName := ""
+	funcNameRoot := root.Children[0]
 
 	if funcNameRoot.IsLeaf() {
 		funcName = funcNameRoot.Token.Text(f.File.Bytes)
@@ -47,7 +47,7 @@ func (f *Function) CompileCall(root *expression.Expression) error {
 
 	// Push
 	for _, register := range f.CPU.General {
-		if f.CurrentScope().IsUsed(register) {
+		if f.RegisterIsUsed(register) {
 			f.Register(asm.PUSH, register)
 		}
 	}
@@ -59,19 +59,20 @@ func (f *Function) CompileCall(root *expression.Expression) error {
 		f.Call(funcName)
 	}
 
+	// Free parameter registers
 	for _, register := range registers {
 		if register == f.CPU.Output[0] && root.Parent != nil {
 			continue
 		}
 
-		f.CurrentScope().Free(register)
+		f.FreeRegister(register)
 	}
 
 	// Pop
 	for i := len(f.CPU.General) - 1; i >= 0; i-- {
 		register := f.CPU.General[i]
 
-		if f.CurrentScope().IsUsed(register) {
+		if f.RegisterIsUsed(register) {
 			f.Register(asm.POP, register)
 		}
 	}

src/build/core/CompileDefinition.go

@@ -21,8 +21,7 @@ func (f *Function) CompileDefinition(node *ast.Define) error {
 		return errors.New(&errors.UnusedVariable{Name: name}, f.File, node.Name.Position)
 	}
 
-	register := f.CurrentScope().MustFindFree(f.CPU.General)
+	register := f.NewRegister()
-	f.CurrentScope().Reserve(register)
 	err := f.ExpressionToRegister(node.Value, register)
 
 	f.AddVariable(&scope.Variable{

src/build/core/Execute.go

@@ -23,8 +23,8 @@ func (f *Function) Execute(operation token.Token, register cpu.Register, value *
 		return f.ExecuteRegisterRegister(operation, register, f.CPU.Output[0])
 	}
 
-	tmp := f.CurrentScope().MustFindFree(f.CPU.General)
+	tmp := f.NewRegister()
-	defer f.CurrentScope().Free(tmp)
+	defer f.FreeRegister(tmp)
 
 	err := f.ExpressionToRegister(value, tmp)
 

src/build/core/ExpressionToRegister.go

@@ -33,10 +33,9 @@ func (f *Function) ExpressionToRegister(node *expression.Expression, register cp
 	final := register
 
 	if f.UsesRegister(right, register) {
-		register = f.CurrentScope().MustFindFree(f.CPU.General)
+		register = f.NewRegister()
 	}
 
-	f.CurrentScope().Reserve(register)
 	err := f.ExpressionToRegister(left, register)
 
 	if err != nil {
@@ -47,7 +46,7 @@ func (f *Function) ExpressionToRegister(node *expression.Expression, register cp
 
 	if register != final {
 		f.RegisterRegister(asm.MOVE, final, register)
-		f.CurrentScope().Free(register)
+		f.FreeRegister(register)
 	}
 
 	return err

src/build/core/Function.go

@@ -2,13 +2,13 @@ package core
 
 import (
 	"git.akyoto.dev/cli/q/src/build/fs"
+	"git.akyoto.dev/cli/q/src/build/register"
 	"git.akyoto.dev/cli/q/src/build/token"
-	"git.akyoto.dev/cli/q/src/build/z"
 )
 
 // Function represents the smallest unit of code.
 type Function struct {
-	z.Compiler
+	register.Machine
 	Name      string
 	File      *fs.File
 	Body      []token.Token

src/build/core/NewFunction.go

@@ -5,9 +5,9 @@ import (
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/cpu"
 	"git.akyoto.dev/cli/q/src/build/fs"
+	"git.akyoto.dev/cli/q/src/build/register"
 	"git.akyoto.dev/cli/q/src/build/scope"
 	"git.akyoto.dev/cli/q/src/build/token"
-	"git.akyoto.dev/cli/q/src/build/z"
 )
 
 // NewFunction creates a new function.
@@ -16,7 +16,7 @@ func NewFunction(name string, file *fs.File, body []token.Token) *Function {
 		Name: name,
 		File: file,
 		Body: body,
-		Compiler: z.Compiler{
+		Machine: register.Machine{
 			Assembler: asm.Assembler{
 				Instructions: make([]asm.Instruction, 0, 8),
 			},

src/build/core/TokenToRegister.go

@@ -21,8 +21,8 @@ func (f *Function) TokenToRegister(t token.Token, register cpu.Register) error {
 			return errors.New(&errors.UnknownIdentifier{Name: name}, f.File, t.Position)
 		}
 
-		f.UseVariable(variable)
 		f.RegisterRegister(asm.MOVE, register, variable.Register)
+		f.UseVariable(variable)
 		return nil
 
 	case token.Number, token.Rune:

src/build/register/AddLabel.go

@@ -1,8 +1,8 @@
-package z
+package register
 
 import "git.akyoto.dev/cli/q/src/build/asm"
 
-func (f *Compiler) AddLabel(label string) {
+func (f *Machine) AddLabel(label string) {
 	f.Assembler.Label(asm.LABEL, label)
 	f.postInstruction()
 }

src/build/register/Call.go

@@ -0,0 +1,7 @@
+package register
+
+func (f *Machine) Call(label string) {
+	f.Assembler.Call(label)
+	f.UseRegister(f.CPU.Output[0])
+	f.postInstruction()
+}

src/build/register/Comment.go

@@ -1,8 +1,8 @@
-package z
+package register
 
 import "fmt"
 
-func (f *Compiler) Comment(format string, args ...any) {
+func (f *Machine) Comment(format string, args ...any) {
 	f.Assembler.Comment(fmt.Sprintf(format, args...))
 	f.postInstruction()
 }

src/build/register/FreeRegister.go

@@ -0,0 +1,8 @@
+package register
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// FreeRegister frees a register.
+func (f *Machine) FreeRegister(register cpu.Register) {
+	f.CurrentScope().Free(register)
+}

src/build/register/Jump.go

@@ -1,8 +1,8 @@
-package z
+package register
 
 import "git.akyoto.dev/cli/q/src/build/asm"
 
-func (f *Compiler) Jump(mnemonic asm.Mnemonic, label string) {
+func (f *Machine) Jump(mnemonic asm.Mnemonic, label string) {
 	f.Assembler.Label(mnemonic, label)
 	f.postInstruction()
 }

src/build/register/Machine.go

@@ -1,4 +1,4 @@
-package z
+package register
 
 import (
 	"git.akyoto.dev/cli/q/src/build/asm"
@@ -6,8 +6,8 @@ import (
 	"git.akyoto.dev/cli/q/src/build/scope"
 )
 
-// Compiler is a register usage aware assembler.
+// Machine is a register usage aware assembler.
-type Compiler struct {
+type Machine struct {
 	scope.Stack
 	Assembler       asm.Assembler
 	CPU             cpu.CPU

src/build/register/MemoryNumber.go

@@ -1,8 +1,8 @@
-package z
+package register
 
 import "git.akyoto.dev/cli/q/src/build/asm"
 
-func (f *Compiler) MemoryNumber(mnemonic asm.Mnemonic, a asm.Memory, b int) {
+func (f *Machine) MemoryNumber(mnemonic asm.Mnemonic, a asm.Memory, b int) {
 	f.Assembler.MemoryNumber(mnemonic, a, b)
 	f.postInstruction()
 }

src/build/register/NewRegister.go

@@ -0,0 +1,10 @@
+package register
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// NewRegister reserves a register.
+func (f *Machine) NewRegister() cpu.Register {
+	register := f.CurrentScope().MustFindFree(f.CPU.General)
+	f.CurrentScope().Reserve(register)
+	return register
+}

src/build/register/Register.go

@@ -1,15 +1,15 @@
-package z
+package register
 
 import (
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/cpu"
 )
 
-func (f *Compiler) Register(mnemonic asm.Mnemonic, a cpu.Register) {
+func (f *Machine) Register(mnemonic asm.Mnemonic, a cpu.Register) {
 	f.Assembler.Register(mnemonic, a)
 
 	if mnemonic == asm.POP {
-		f.CurrentScope().Use(a)
+		f.UseRegister(a)
 	}
 
 	f.postInstruction()

src/build/register/RegisterIsUsed.go

@@ -0,0 +1,8 @@
+package register
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// RegisterIsUsed reserves a register.
+func (f *Machine) RegisterIsUsed(register cpu.Register) bool {
+	return f.CurrentScope().IsUsed(register)
+}

src/build/register/RegisterLabel.go

@@ -1,19 +1,19 @@
-package z
+package register
 
 import (
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/cpu"
 )
 
-func (f *Compiler) RegisterLabel(mnemonic asm.Mnemonic, register cpu.Register, label string) {
+func (f *Machine) RegisterLabel(mnemonic asm.Mnemonic, register cpu.Register, label string) {
-	if f.CurrentScope().IsUsed(register) && isDestructive(mnemonic) {
+	if f.RegisterIsUsed(register) && isDestructive(mnemonic) {
 		f.SaveRegister(register)
 	}
 
 	f.Assembler.RegisterLabel(mnemonic, register, label)
 
 	if mnemonic == asm.MOVE {
-		f.CurrentScope().Use(register)
+		f.UseRegister(register)
 	}
 
 	f.postInstruction()

src/build/register/RegisterNumber.go

@@ -1,19 +1,19 @@
-package z
+package register
 
 import (
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/cpu"
 )
 
-func (f *Compiler) RegisterNumber(mnemonic asm.Mnemonic, a cpu.Register, b int) {
+func (f *Machine) RegisterNumber(mnemonic asm.Mnemonic, a cpu.Register, b int) {
-	if f.CurrentScope().IsUsed(a) && isDestructive(mnemonic) {
+	if f.RegisterIsUsed(a) && isDestructive(mnemonic) {
 		f.SaveRegister(a)
 	}
 
 	f.Assembler.RegisterNumber(mnemonic, a, b)
 
 	if mnemonic == asm.MOVE {
-		f.CurrentScope().Use(a)
+		f.UseRegister(a)
 	}
 
 	f.postInstruction()

src/build/register/RegisterRegister.go

@@ -1,23 +1,23 @@
-package z
+package register
 
 import (
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/cpu"
 )
 
-func (f *Compiler) RegisterRegister(mnemonic asm.Mnemonic, a cpu.Register, b cpu.Register) {
+func (f *Machine) RegisterRegister(mnemonic asm.Mnemonic, a cpu.Register, b cpu.Register) {
 	if mnemonic == asm.MOVE && a == b {
 		return
 	}
 
-	if f.CurrentScope().IsUsed(a) && isDestructive(mnemonic) {
+	if f.RegisterIsUsed(a) && isDestructive(mnemonic) {
 		f.SaveRegister(a)
 	}
 
 	f.Assembler.RegisterRegister(mnemonic, a, b)
 
 	if mnemonic == asm.MOVE {
-		f.CurrentScope().Use(a)
+		f.UseRegister(a)
 	}
 
 	f.postInstruction()

src/build/register/Return.go

@@ -1,6 +1,6 @@
-package z
+package register
 
-func (f *Compiler) Return() {
+func (f *Machine) Return() {
 	f.Assembler.Return()
 	f.postInstruction()
 }

src/build/register/SaveRegister.go

@@ -1,4 +1,4 @@
-package z
+package register
 
 import (
 	"git.akyoto.dev/cli/q/src/build/asm"
@@ -6,8 +6,8 @@ import (
 )
 
 // SaveRegister attempts to move a variable occupying this register to another register.
-func (f *Compiler) SaveRegister(register cpu.Register) {
+func (f *Machine) SaveRegister(register cpu.Register) {
-	if !f.CurrentScope().IsUsed(register) {
+	if !f.RegisterIsUsed(register) {
 		return
 	}
 
@@ -23,8 +23,7 @@ func (f *Compiler) SaveRegister(register cpu.Register) {
 		return
 	}
 
-	newRegister := f.CurrentScope().MustFindFree(f.CPU.General)
+	newRegister := f.NewRegister()
-	f.CurrentScope().Reserve(newRegister)
 	f.RegisterRegister(asm.MOVE, newRegister, register)
 	variable.Register = newRegister
 }

src/build/register/Syscall.go

@@ -0,0 +1,7 @@
+package register
+
+func (f *Machine) Syscall() {
+	f.Assembler.Syscall()
+	f.UseRegister(f.CPU.Output[0])
+	f.postInstruction()
+}

src/build/register/UseRegister.go

@@ -0,0 +1,8 @@
+package register
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// Use marks a register to be currently in use.
+func (f *Machine) UseRegister(register cpu.Register) {
+	f.CurrentScope().Use(register)
+}

src/build/register/isDestructive.go

@@ -1,4 +1,4 @@
-package z
+package register
 
 import "git.akyoto.dev/cli/q/src/build/asm"
 

src/build/register/postInstruction.go

@@ -1,8 +1,8 @@
-package z
+package register
 
 import "git.akyoto.dev/cli/q/src/build/config"
 
-func (f *Compiler) postInstruction() {
+func (f *Machine) postInstruction() {
 	if !config.Assembler {
 		return
 	}

src/build/z/Call.go

@@ -1,7 +0,0 @@
-package z
-
-func (f *Compiler) Call(label string) {
-	f.Assembler.Call(label)
-	f.CurrentScope().Use(f.CPU.Output[0])
-	f.postInstruction()
-}

src/build/z/Syscall.go

@@ -1,7 +0,0 @@
-package z
-
-func (f *Compiler) Syscall() {
-	f.Assembler.Syscall()
-	f.CurrentScope().Use(f.CPU.Output[0])
-	f.postInstruction()
-}

tests/programs/branch.q

@@ -63,6 +63,10 @@ main() {
 		sys.exit(1)
 	}
 
+	if inc(x) == dec(x) {
+		sys.exit(1)
+	}
+
 	if x == 0 {
 		sys.exit(0)
 	}