Implemented constant folding

src/build/config/config.go

@@ -15,6 +15,15 @@ const (
 )
 
 var (
+	// Shows the assembly instructions at the end of the compilation.
 	Assembler = false
-	Dry       = false
+
+	// Calculates the result of operations on constants at compile time.
+	ConstantFold = true
+
+	// Skips writing the executable to disk.
+	Dry = false
+
+	// Skips compiling assert statements.
+	SkipAsserts = false
 )

src/build/core/CompileASTNode.go

@@ -8,21 +8,27 @@ import (
 func (f *Function) CompileASTNode(node ast.Node) error {
 	switch node := node.(type) {
 	case *ast.Assert:
+		f.Fold(node.Condition)
 		return f.CompileAssert(node)
 
 	case *ast.Assign:
+		f.Fold(node.Expression)
 		return f.CompileAssign(node)
 
 	case *ast.Call:
+		f.Fold(node.Expression)
 		return f.CompileCall(node.Expression)
 
 	case *ast.Define:
+		f.Fold(node.Expression)
 		return f.CompileDefinition(node)
 
 	case *ast.Return:
+		f.Fold(node.Value)
 		return f.CompileReturn(node)
 
 	case *ast.If:
+		f.Fold(node.Condition)
 		return f.CompileIf(node)
 
 	case *ast.Loop:

src/build/core/CompileAssert.go

@@ -5,10 +5,15 @@ import (
 
 	"git.akyoto.dev/cli/q/src/build/asm"
 	"git.akyoto.dev/cli/q/src/build/ast"
+	"git.akyoto.dev/cli/q/src/build/config"
 )
 
 // CompileAssert compiles an assertion.
 func (f *Function) CompileAssert(assert *ast.Assert) error {
+	if config.SkipAsserts {
+		return nil
+	}
+
 	f.count.assert++
 	success := fmt.Sprintf("%s_assert_%d_true", f.Name, f.count.assert)
 	fail := fmt.Sprintf("%s_assert_%d_false", f.Name, f.count.assert)

src/build/core/ExpressionToRegister.go

@@ -10,6 +10,11 @@ import (
 
 // ExpressionToRegister puts the result of an expression into the specified register.
 func (f *Function) ExpressionToRegister(node *expression.Expression, register cpu.Register) error {
+	if node.IsFolded {
+		f.RegisterNumber(asm.MOVE, register, node.Value)
+		return nil
+	}
+
 	if node.IsLeaf() {
 		return f.TokenToRegister(node.Token, register)
 	}

src/build/core/Fold.go

@@ -0,0 +1,74 @@
+package core
+
+import (
+	"git.akyoto.dev/cli/q/src/build/config"
+	"git.akyoto.dev/cli/q/src/build/expression"
+	"git.akyoto.dev/cli/q/src/build/token"
+)
+
+// Fold will try to precalculate the results of operations with constants.
+func (f *Function) Fold(expr *expression.Expression) error {
+	if !config.ConstantFold {
+		return nil
+	}
+
+	if expr == nil {
+		return nil
+	}
+
+	if expr.IsLeaf() {
+		if expr.Token.IsNumeric() {
+			value, err := f.Number(expr.Token)
+			expr.Value = value
+			expr.IsFolded = true
+			return err
+		}
+
+		return nil
+	}
+
+	canFold := true
+
+	for _, child := range expr.Children {
+		f.Fold(child)
+
+		if !child.IsFolded {
+			canFold = false
+		}
+	}
+
+	if !canFold || len(expr.Children) != 2 {
+		return nil
+	}
+
+	a := expr.Children[0].Value
+	b := expr.Children[1].Value
+
+	switch expr.Token.Kind {
+	case token.Or:
+		expr.Value = a | b
+	case token.And:
+		expr.Value = a & b
+	case token.Xor:
+		expr.Value = a ^ b
+	case token.Add:
+		expr.Value = a + b
+	case token.Sub:
+		expr.Value = a - b
+	case token.Mul:
+		expr.Value = a * b
+	case token.Div:
+		expr.Value = a / b
+	case token.Mod:
+		expr.Value = a % b
+	case token.Shl:
+		expr.Value = a << b
+	case token.Shr:
+		expr.Value = a >> b
+	default:
+		return nil
+	}
+
+	expr.IsFolded = true
+	return nil
+}

src/build/expression/Expression.go

@@ -12,6 +12,8 @@ type Expression struct {
 	Children   []*Expression
 	Token      token.Token
 	Precedence int8
+	Value      int
+	IsFolded   bool
 }
 
 // New creates a new expression.

src/build/token/Token.go

@@ -38,6 +38,11 @@ func (t Token) IsKeyword() bool {
 	return t.Kind > _keywords && t.Kind < _keywordsEnd
 }
 
+// IsNumeric returns true if the token is a number or rune.
+func (t Token) IsNumeric() bool {
+	return t.Kind == Number || t.Kind == Rune
+}
+
 // IsOperator returns true if the token is an operator.
 func (t Token) IsOperator() bool {
 	return t.Kind > _operators && t.Kind < _operatorsEnd

tests/programs_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"git.akyoto.dev/cli/q/src/build"
+	"git.akyoto.dev/cli/q/src/build/config"
 	"git.akyoto.dev/go/assert"
 )
 
@@ -52,11 +53,21 @@ var programs = []struct {
 }
 
 func TestPrograms(t *testing.T) {
+	config.ConstantFold = false
+
 	for _, test := range programs {
 		t.Run(test.Name, func(t *testing.T) {
 			run(t, filepath.Join("programs", test.Name+".q"), test.Input, test.Output, test.ExitCode)
 		})
 	}
+
+	config.ConstantFold = true
+
+	for _, test := range programs {
+		t.Run(test.Name+" (optimized)", func(t *testing.T) {
+			run(t, filepath.Join("programs", test.Name+".q"), test.Input, test.Output, test.ExitCode)
+		})
+	}
 }
 
 func BenchmarkPrograms(b *testing.B) {