Implemented infinite loops

src/build/Function.go

@@ -23,6 +23,7 @@ type Function struct {
 	Assembler asm.Assembler
 	CPU       cpu.CPU
 	Error     error
+	count     struct{ loop int }
 }
 
 // Compile turns a function into machine code.
@@ -115,104 +116,6 @@ func (f *Function) CompileInstruction(line token.List) error {
 	return errors.New(&errors.InvalidInstruction{Instruction: expr.Token.Text()}, f.File, expr.Token.Position)
 }
 
-// CompileKeyword compiles an instruction that starts with a keyword.
-func (f *Function) CompileKeyword(line token.List) error {
-	switch line[0].Text() {
-	case "return":
-		if len(line) > 1 {
-			value := expression.Parse(line[1:])
-			defer value.Close()
-			// TODO: Set the return value
-		}
-
-		f.Assembler.Return()
-
-	case "loop":
-		blockStart := line.IndexKind(token.BlockStart) + 1
-		blockEnd := line.LastIndexKind(token.BlockEnd)
-
-		if blockStart == -1 {
-			return errors.New(errors.MissingBlockStart, f.File, line[0].End())
-		}
-
-		if blockEnd == -1 {
-			return errors.New(errors.MissingBlockEnd, f.File, line[len(line)-1].End())
-		}
-
-		return f.CompileTokens(line[blockStart:blockEnd])
-
-	default:
-		return errors.New(&errors.KeywordNotImplemented{Keyword: line[0].Text()}, f.File, line[0].Position)
-	}
-
-	return nil
-}
-
-// CompileVariableDefinition compiles a variable definition.
-func (f *Function) CompileVariableDefinition(expr *expression.Expression) error {
-	if len(expr.Children) < 2 {
-		return errors.New(errors.MissingAssignValue, f.File, expr.LastChild().Token.End())
-	}
-
-	name := expr.Children[0].Token.Text()
-
-	if f.identifierExists(name) {
-		return errors.New(&errors.VariableAlreadyExists{Name: name}, f.File, expr.Children[0].Token.Position)
-	}
-
-	value := expr.Children[1]
-
-	err := value.EachLeaf(func(leaf *expression.Expression) error {
-		if leaf.Token.Kind == token.Identifier && !f.identifierExists(leaf.Token.Text()) {
-			return errors.New(&errors.UnknownIdentifier{Name: leaf.Token.Text()}, f.File, leaf.Token.Position)
-		}
-
-		return nil
-	})
-
-	if err != nil {
-		return err
-	}
-
-	reg, exists := f.CPU.FindFree()
-
-	if !exists {
-		panic("no free registers")
-	}
-
-	f.ExpressionToRegister(value, reg)
-	f.CPU.Use(reg)
-
-	f.Variables[name] = &Variable{
-		Name:     name,
-		Register: reg,
-	}
-
-	return nil
-}
-
-// CompileFunctionCall compiles a function call.
-func (f *Function) CompileFunctionCall(expr *expression.Expression) error {
-	funcName := expr.Children[0].Token.Text()
-	parameters := expr.Children[1:]
-
-	for i, parameter := range parameters {
-		err := f.ExpressionToRegister(parameter, f.CPU.Syscall[i])
-
-		if err != nil {
-			return err
-		}
-	}
-
-	if funcName == "syscall" {
-		f.Assembler.Syscall()
-	} else {
-		f.Assembler.Call(funcName)
-	}
-
-	return nil
-}
-
 // ExpressionToRegister moves the result of an expression into the given register.
 func (f *Function) ExpressionToRegister(root *expression.Expression, register cpu.Register) error {
 	if root.IsLeaf() {
@@ -285,13 +188,3 @@ func (f *Function) identifierExists(name string) bool {
 	_, exists := f.Variables[name]
 	return exists
 }
-
-// isVariableDefinition returns true if the expression is a variable definition.
-func isVariableDefinition(expr *expression.Expression) bool {
-	return expr.Token.Kind == token.Operator && expr.Token.Text() == ":="
-}
-
-// isFunctionCall returns true if the expression is a function call.
-func isFunctionCall(expr *expression.Expression) bool {
-	return expr.Token.Kind == token.Operator && expr.Token.Text() == "λ"
-}

src/build/FunctionCall.go

@@ -0,0 +1,33 @@
+package build
+
+import (
+	"git.akyoto.dev/cli/q/src/build/expression"
+	"git.akyoto.dev/cli/q/src/build/token"
+)
+
+// CompileFunctionCall compiles a top-level function call.
+func (f *Function) CompileFunctionCall(expr *expression.Expression) error {
+	funcName := expr.Children[0].Token.Text()
+	parameters := expr.Children[1:]
+
+	for i, parameter := range parameters {
+		err := f.ExpressionToRegister(parameter, f.CPU.Syscall[i])
+
+		if err != nil {
+			return err
+		}
+	}
+
+	if funcName == "syscall" {
+		f.Assembler.Syscall()
+	} else {
+		f.Assembler.Call(funcName)
+	}
+
+	return nil
+}
+
+// isFunctionCall returns true if the expression is a function call.
+func isFunctionCall(expr *expression.Expression) bool {
+	return expr.Token.Kind == token.Operator && expr.Token.Text() == "λ"
+}

src/build/Keyword.go

@@ -0,0 +1,46 @@
+package build
+
+import (
+	"fmt"
+
+	"git.akyoto.dev/cli/q/src/build/expression"
+	"git.akyoto.dev/cli/q/src/build/token"
+	"git.akyoto.dev/cli/q/src/errors"
+)
+
+// CompileKeyword compiles an instruction that starts with a keyword.
+func (f *Function) CompileKeyword(line token.List) error {
+	switch line[0].Text() {
+	case "return":
+		if len(line) > 1 {
+			value := expression.Parse(line[1:])
+			defer value.Close()
+			// TODO: Set the return value
+		}
+
+		f.Assembler.Return()
+
+	case "loop":
+		blockStart := line.IndexKind(token.BlockStart) + 1
+		blockEnd := line.LastIndexKind(token.BlockEnd)
+
+		if blockStart == -1 {
+			return errors.New(errors.MissingBlockStart, f.File, line[0].End())
+		}
+
+		if blockEnd == -1 {
+			return errors.New(errors.MissingBlockEnd, f.File, line[len(line)-1].End())
+		}
+
+		loop := fmt.Sprintf("%s_loop_%d", f.Name, f.count.loop)
+		f.Assembler.Label(loop)
+		defer f.Assembler.Jump(loop)
+		f.count.loop++
+		return f.CompileTokens(line[blockStart:blockEnd])
+
+	default:
+		return errors.New(&errors.KeywordNotImplemented{Keyword: line[0].Text()}, f.File, line[0].Position)
+	}
+
+	return nil
+}

src/build/VariableDefinition.go

@@ -0,0 +1,55 @@
+package build
+
+import (
+	"git.akyoto.dev/cli/q/src/build/expression"
+	"git.akyoto.dev/cli/q/src/build/token"
+	"git.akyoto.dev/cli/q/src/errors"
+)
+
+// CompileVariableDefinition compiles a variable definition.
+func (f *Function) CompileVariableDefinition(expr *expression.Expression) error {
+	if len(expr.Children) < 2 {
+		return errors.New(errors.MissingAssignValue, f.File, expr.LastChild().Token.End())
+	}
+
+	name := expr.Children[0].Token.Text()
+
+	if f.identifierExists(name) {
+		return errors.New(&errors.VariableAlreadyExists{Name: name}, f.File, expr.Children[0].Token.Position)
+	}
+
+	value := expr.Children[1]
+
+	err := value.EachLeaf(func(leaf *expression.Expression) error {
+		if leaf.Token.Kind == token.Identifier && !f.identifierExists(leaf.Token.Text()) {
+			return errors.New(&errors.UnknownIdentifier{Name: leaf.Token.Text()}, f.File, leaf.Token.Position)
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return err
+	}
+
+	reg, exists := f.CPU.FindFree()
+
+	if !exists {
+		panic("no free registers")
+	}
+
+	f.ExpressionToRegister(value, reg)
+	f.CPU.Use(reg)
+
+	f.Variables[name] = &Variable{
+		Name:     name,
+		Register: reg,
+	}
+
+	return nil
+}
+
+// isVariableDefinition returns true if the expression is a variable definition.
+func isVariableDefinition(expr *expression.Expression) bool {
+	return expr.Token.Kind == token.Operator && expr.Token.Text() == ":="
+}

src/build/arch/x64/Jump.go

@@ -0,0 +1,11 @@
+package x64
+
+// Jump continues program flow at the new address.
+// The address is relative to the next instruction.
+func Jump8(code []byte, address int8) []byte {
+	return append(
+		code,
+		0xeb,
+		byte(address),
+	)
+}

src/build/asm/Assembler.go

@@ -44,14 +44,32 @@ func (a *Assembler) Finalize() ([]byte, []byte) {
 
 		case CALL:
 			code = x64.Call(code, 0x00_00_00_00)
+			size := 4
 			label := x.Data.(*Label)
-			nextInstructionAddress := len(code)
+			nextInstructionAddress := Address(len(code))
 
 			pointers = append(pointers, Pointer{
-				Position: Address(len(code) - 4),
+				Position: Address(len(code) - size),
+				Size:     uint8(size),
 				Resolve: func() Address {
 					destination := labels[label.Name]
-					distance := int32(destination) - int32(nextInstructionAddress)
+					distance := destination - nextInstructionAddress
+					return Address(distance)
+				},
+			})
+
+		case JUMP:
+			code = x64.Jump8(code, 0x00)
+			size := 1
+			label := x.Data.(*Label)
+			nextInstructionAddress := Address(len(code))
+
+			pointers = append(pointers, Pointer{
+				Position: Address(len(code) - size),
+				Size:     uint8(size),
+				Resolve: func() Address {
+					destination := labels[label.Name]
+					distance := destination - nextInstructionAddress
 					return Address(distance)
 				},
 			})
@@ -67,8 +85,22 @@ func (a *Assembler) Finalize() ([]byte, []byte) {
 	// dataStart := config.BaseAddress + config.CodeOffset + Address(len(code))
 
 	for _, pointer := range pointers {
-		slice := code[pointer.Position : pointer.Position+4]
-		binary.LittleEndian.PutUint32(slice, pointer.Resolve())
+		slice := code[pointer.Position : pointer.Position+Address(pointer.Size)]
+		address := pointer.Resolve()
+
+		switch pointer.Size {
+		case 1:
+			slice[0] = uint8(address)
+
+		case 2:
+			binary.LittleEndian.PutUint16(slice, uint16(address))
+
+		case 4:
+			binary.LittleEndian.PutUint32(slice, uint32(address))
+
+		case 8:
+			binary.LittleEndian.PutUint64(slice, uint64(address))
+		}
 	}
 
 	return code, data

src/build/asm/Instructions.go

@@ -44,6 +44,16 @@ func (a *Assembler) Call(name string) {
 	})
 }
 
+// Jump jumps to a position that is identified by a label.
+func (a *Assembler) Jump(name string) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: JUMP,
+		Data: &Label{
+			Name: name,
+		},
+	})
+}
+
 // Return returns back to the caller.
 func (a *Assembler) Return() {
 	a.Instructions = append(a.Instructions, Instruction{Mnemonic: RETURN})

src/build/asm/Mnemonic.go

@@ -9,6 +9,7 @@ const (
 	SYSCALL
 	LABEL
 	CALL
+	JUMP
 )
 
 // String returns a human readable version.
@@ -28,6 +29,9 @@ func (m Mnemonic) String() string {
 
 	case CALL:
 		return "call"
+
+	case JUMP:
+		return "jump"
 	}
 
 	return "NONE"

src/build/asm/Pointer.go

@@ -8,5 +8,6 @@ type Address = uint32
 // Resolve:  The function that will return the final address.
 type Pointer struct {
 	Position Address
+	Size     uint8
 	Resolve  func() Address
 }