From 26214366e37a04b26d1267bc6da440cc86939ff2 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <admin@akyoto.dev>
Date: Tue, 23 Jul 2024 22:14:23 +0200
Subject: [PATCH] Simplified code

---
 src/build/core/Compare.go                        |  6 +++---
 src/build/core/CompileCall.go                    |  9 +++++----
 src/build/core/CompileDefinition.go              |  3 +--
 src/build/core/Execute.go                        |  4 ++--
 src/build/core/ExpressionToRegister.go           |  5 ++---
 src/build/core/Function.go                       |  4 ++--
 src/build/core/NewFunction.go                    |  4 ++--
 src/build/core/TokenToRegister.go                |  2 +-
 src/build/{z => register}/AddLabel.go            |  4 ++--
 src/build/register/Call.go                       |  7 +++++++
 src/build/{z => register}/Comment.go             |  4 ++--
 src/build/register/FreeRegister.go               |  8 ++++++++
 src/build/{z => register}/Jump.go                |  4 ++--
 src/build/{z/Compiler.go => register/Machine.go} |  6 +++---
 src/build/{z => register}/MemoryNumber.go        |  4 ++--
 src/build/register/NewRegister.go                | 10 ++++++++++
 src/build/{z => register}/Register.go            |  6 +++---
 src/build/register/RegisterIsUsed.go             |  8 ++++++++
 src/build/{z => register}/RegisterLabel.go       |  8 ++++----
 src/build/{z => register}/RegisterNumber.go      |  8 ++++----
 src/build/{z => register}/RegisterRegister.go    |  8 ++++----
 src/build/{z => register}/Return.go              |  4 ++--
 src/build/{z => register}/SaveRegister.go        |  9 ++++-----
 src/build/register/Syscall.go                    |  7 +++++++
 src/build/register/UseRegister.go                |  8 ++++++++
 src/build/{z => register}/isDestructive.go       |  2 +-
 src/build/{z => register}/postInstruction.go     |  4 ++--
 src/build/z/Call.go                              |  7 -------
 src/build/z/Syscall.go                           |  7 -------
 tests/programs/branch.q                          |  4 ++++
 30 files changed, 105 insertions(+), 69 deletions(-)
 rename src/build/{z => register}/AddLabel.go (63%)
 create mode 100644 src/build/register/Call.go
 rename src/build/{z => register}/Comment.go (54%)
 create mode 100644 src/build/register/FreeRegister.go
 rename src/build/{z => register}/Jump.go (57%)
 rename src/build/{z/Compiler.go => register/Machine.go} (72%)
 rename src/build/{z => register}/MemoryNumber.go (54%)
 create mode 100644 src/build/register/NewRegister.go
 rename src/build/{z => register}/Register.go (62%)
 create mode 100644 src/build/register/RegisterIsUsed.go
 rename src/build/{z => register}/RegisterLabel.go (52%)
 rename src/build/{z => register}/RegisterNumber.go (54%)
 rename src/build/{z => register}/RegisterRegister.go (58%)
 rename src/build/{z => register}/Return.go (50%)
 rename src/build/{z => register}/SaveRegister.go (69%)
 create mode 100644 src/build/register/Syscall.go
 create mode 100644 src/build/register/UseRegister.go
 rename src/build/{z => register}/isDestructive.go (92%)
 rename src/build/{z => register}/postInstruction.go (74%)
 delete mode 100644 src/build/z/Call.go
 delete mode 100644 src/build/z/Syscall.go

diff --git a/src/build/core/Compare.go b/src/build/core/Compare.go
index 7eb92f7..0ccfe3c 100644
--- a/src/build/core/Compare.go
+++ b/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)
 }
diff --git a/src/build/core/CompileCall.go b/src/build/core/CompileCall.go
index 358d4f8..1441ee9 100644
--- a/src/build/core/CompileCall.go
+++ b/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)
 		}
 	}
diff --git a/src/build/core/CompileDefinition.go b/src/build/core/CompileDefinition.go
index 71745b5..6e1943f 100644
--- a/src/build/core/CompileDefinition.go
+++ b/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)
-	f.CurrentScope().Reserve(register)
+	register := f.NewRegister()
 	err := f.ExpressionToRegister(node.Value, register)
 
 	f.AddVariable(&scope.Variable{
diff --git a/src/build/core/Execute.go b/src/build/core/Execute.go
index 09f2dec..76a54bf 100644
--- a/src/build/core/Execute.go
+++ b/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)
-	defer f.CurrentScope().Free(tmp)
+	tmp := f.NewRegister()
+	defer f.FreeRegister(tmp)
 
 	err := f.ExpressionToRegister(value, tmp)
 
diff --git a/src/build/core/ExpressionToRegister.go b/src/build/core/ExpressionToRegister.go
index c900c7b..212b7ed 100644
--- a/src/build/core/ExpressionToRegister.go
+++ b/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
diff --git a/src/build/core/Function.go b/src/build/core/Function.go
index 65b9252..f926956 100644
--- a/src/build/core/Function.go
+++ b/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
diff --git a/src/build/core/NewFunction.go b/src/build/core/NewFunction.go
index f73aedb..d4bc8f3 100644
--- a/src/build/core/NewFunction.go
+++ b/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),
 			},
diff --git a/src/build/core/TokenToRegister.go b/src/build/core/TokenToRegister.go
index cbdd1c9..50e2b77 100644
--- a/src/build/core/TokenToRegister.go
+++ b/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:
diff --git a/src/build/z/AddLabel.go b/src/build/register/AddLabel.go
similarity index 63%
rename from src/build/z/AddLabel.go
rename to src/build/register/AddLabel.go
index ccc18a8..3189ee0 100644
--- a/src/build/z/AddLabel.go
+++ b/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()
 }
diff --git a/src/build/register/Call.go b/src/build/register/Call.go
new file mode 100644
index 0000000..6008dbd
--- /dev/null
+++ b/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()
+}
diff --git a/src/build/z/Comment.go b/src/build/register/Comment.go
similarity index 54%
rename from src/build/z/Comment.go
rename to src/build/register/Comment.go
index d795f3b..ca86f0f 100644
--- a/src/build/z/Comment.go
+++ b/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()
 }
diff --git a/src/build/register/FreeRegister.go b/src/build/register/FreeRegister.go
new file mode 100644
index 0000000..5c459b7
--- /dev/null
+++ b/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)
+}
diff --git a/src/build/z/Jump.go b/src/build/register/Jump.go
similarity index 57%
rename from src/build/z/Jump.go
rename to src/build/register/Jump.go
index 5938ed5..ff77d01 100644
--- a/src/build/z/Jump.go
+++ b/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()
 }
diff --git a/src/build/z/Compiler.go b/src/build/register/Machine.go
similarity index 72%
rename from src/build/z/Compiler.go
rename to src/build/register/Machine.go
index b93e895..50a22b7 100644
--- a/src/build/z/Compiler.go
+++ b/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.
-type Compiler struct {
+// Machine is a register usage aware assembler.
+type Machine struct {
 	scope.Stack
 	Assembler       asm.Assembler
 	CPU             cpu.CPU
diff --git a/src/build/z/MemoryNumber.go b/src/build/register/MemoryNumber.go
similarity index 54%
rename from src/build/z/MemoryNumber.go
rename to src/build/register/MemoryNumber.go
index 55ab175..6e99fda 100644
--- a/src/build/z/MemoryNumber.go
+++ b/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()
 }
diff --git a/src/build/register/NewRegister.go b/src/build/register/NewRegister.go
new file mode 100644
index 0000000..fb2300c
--- /dev/null
+++ b/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
+}
diff --git a/src/build/z/Register.go b/src/build/register/Register.go
similarity index 62%
rename from src/build/z/Register.go
rename to src/build/register/Register.go
index 6244121..89f0ca1 100644
--- a/src/build/z/Register.go
+++ b/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()
diff --git a/src/build/register/RegisterIsUsed.go b/src/build/register/RegisterIsUsed.go
new file mode 100644
index 0000000..0ba6d0e
--- /dev/null
+++ b/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)
+}
diff --git a/src/build/z/RegisterLabel.go b/src/build/register/RegisterLabel.go
similarity index 52%
rename from src/build/z/RegisterLabel.go
rename to src/build/register/RegisterLabel.go
index 6047d05..7778e5a 100644
--- a/src/build/z/RegisterLabel.go
+++ b/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) {
-	if f.CurrentScope().IsUsed(register) && isDestructive(mnemonic) {
+func (f *Machine) RegisterLabel(mnemonic asm.Mnemonic, register cpu.Register, label string) {
+	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()
diff --git a/src/build/z/RegisterNumber.go b/src/build/register/RegisterNumber.go
similarity index 54%
rename from src/build/z/RegisterNumber.go
rename to src/build/register/RegisterNumber.go
index 14f84ae..ce9a41f 100644
--- a/src/build/z/RegisterNumber.go
+++ b/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) {
-	if f.CurrentScope().IsUsed(a) && isDestructive(mnemonic) {
+func (f *Machine) RegisterNumber(mnemonic asm.Mnemonic, a cpu.Register, b int) {
+	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()
diff --git a/src/build/z/RegisterRegister.go b/src/build/register/RegisterRegister.go
similarity index 58%
rename from src/build/z/RegisterRegister.go
rename to src/build/register/RegisterRegister.go
index 7370955..a969ca5 100644
--- a/src/build/z/RegisterRegister.go
+++ b/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()
diff --git a/src/build/z/Return.go b/src/build/register/Return.go
similarity index 50%
rename from src/build/z/Return.go
rename to src/build/register/Return.go
index 596584b..b9e09b7 100644
--- a/src/build/z/Return.go
+++ b/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()
 }
diff --git a/src/build/z/SaveRegister.go b/src/build/register/SaveRegister.go
similarity index 69%
rename from src/build/z/SaveRegister.go
rename to src/build/register/SaveRegister.go
index dacacf5..1c20818 100644
--- a/src/build/z/SaveRegister.go
+++ b/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) {
-	if !f.CurrentScope().IsUsed(register) {
+func (f *Machine) SaveRegister(register cpu.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)
-	f.CurrentScope().Reserve(newRegister)
+	newRegister := f.NewRegister()
 	f.RegisterRegister(asm.MOVE, newRegister, register)
 	variable.Register = newRegister
 }
diff --git a/src/build/register/Syscall.go b/src/build/register/Syscall.go
new file mode 100644
index 0000000..ace09d7
--- /dev/null
+++ b/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()
+}
diff --git a/src/build/register/UseRegister.go b/src/build/register/UseRegister.go
new file mode 100644
index 0000000..ce45d81
--- /dev/null
+++ b/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)
+}
diff --git a/src/build/z/isDestructive.go b/src/build/register/isDestructive.go
similarity index 92%
rename from src/build/z/isDestructive.go
rename to src/build/register/isDestructive.go
index 2165fcb..086ceca 100644
--- a/src/build/z/isDestructive.go
+++ b/src/build/register/isDestructive.go
@@ -1,4 +1,4 @@
-package z
+package register
 
 import "git.akyoto.dev/cli/q/src/build/asm"
 
diff --git a/src/build/z/postInstruction.go b/src/build/register/postInstruction.go
similarity index 74%
rename from src/build/z/postInstruction.go
rename to src/build/register/postInstruction.go
index a9166e4..d3e2b5d 100644
--- a/src/build/z/postInstruction.go
+++ b/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
 	}
diff --git a/src/build/z/Call.go b/src/build/z/Call.go
deleted file mode 100644
index f1284bb..0000000
--- a/src/build/z/Call.go
+++ /dev/null
@@ -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()
-}
diff --git a/src/build/z/Syscall.go b/src/build/z/Syscall.go
deleted file mode 100644
index dfd2199..0000000
--- a/src/build/z/Syscall.go
+++ /dev/null
@@ -1,7 +0,0 @@
-package z
-
-func (f *Compiler) Syscall() {
-	f.Assembler.Syscall()
-	f.CurrentScope().Use(f.CPU.Output[0])
-	f.postInstruction()
-}
diff --git a/tests/programs/branch.q b/tests/programs/branch.q
index aaa393f..9e6f514 100644
--- a/tests/programs/branch.q
+++ b/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)
 	}