Improved SSA and added unused value checks

src/core/CheckDeadCode.go

@@ -0,0 +1,16 @@
+package core
+
+import (
+	"git.urbach.dev/cli/q/src/errors"
+)
+
+// CheckDeadCode checks for dead values.
+func (f *Function) CheckDeadCode() error {
+	for instr := range f.Values {
+		if instr.IsConst() && instr.Alive() == 0 {
+			return errors.New(&UnusedValue{Value: instr.String()}, f.File, instr.Token().Position)
+		}
+	}
+
+	return nil
+}

src/core/Compile.go

@@ -26,4 +26,6 @@ func (f *Function) Compile() {
 			return
 		}
 	}
+
+	f.Err = f.CheckDeadCode()
 }

src/core/CompileReturn.go

@@ -15,9 +15,10 @@ func (f *Function) CompileReturn(tokens token.List) error {
 		return err
 	}
 
-	f.Append(ssa.Value{
-		Type: ssa.Return,
-		Args: []*ssa.Value{value},
+	f.Append(&ssa.Return{
+		Arguments: ssa.Arguments{
+			Args: []ssa.Value{value},
+		},
 	})
 
 	return nil

src/core/Evaluate.go

@@ -10,7 +10,7 @@ import (
 )
 
 // Evaluate converts an expression to an SSA value.
-func (f *Function) Evaluate(expr *expression.Expression) (*ssa.Value, error) {
+func (f *Function) Evaluate(expr *expression.Expression) (ssa.Value, error) {
 	if expr.IsLeaf() {
 		switch expr.Token.Kind {
 		case token.Identifier:
@@ -30,12 +30,16 @@ func (f *Function) Evaluate(expr *expression.Expression) (*ssa.Value, error) {
 				return nil, err
 			}
 
-			return f.AppendInt(number), nil
+			v := f.AppendInt(number)
+			v.Source = expr.Token
+			return v, nil
 
 		case token.String:
 			data := expr.Token.Bytes(f.File.Bytes)
 			data = Unescape(data)
-			return f.AppendBytes(data), nil
+			v := f.AppendBytes(data)
+			v.Source = expr.Token
+			return v, nil
 		}
 
 		return nil, errors.New(InvalidExpression, f.File, expr.Token.Position)
@@ -44,7 +48,7 @@ func (f *Function) Evaluate(expr *expression.Expression) (*ssa.Value, error) {
 	switch expr.Token.Kind {
 	case token.Call:
 		children := expr.Children
-		typ := ssa.Call
+		isSyscall := false
 
 		if children[0].Token.Kind == token.Identifier {
 			funcName := children[0].String(f.File.Bytes)
@@ -56,11 +60,11 @@ func (f *Function) Evaluate(expr *expression.Expression) (*ssa.Value, error) {
 
 			if funcName == "syscall" {
 				children = children[1:]
-				typ = ssa.Syscall
+				isSyscall = true
 			}
 		}
 
-		args := make([]*ssa.Value, len(children))
+		args := make([]ssa.Value, len(children))
 
 		for i, child := range children {
 			value, err := f.Evaluate(child)
@@ -72,12 +76,27 @@ func (f *Function) Evaluate(expr *expression.Expression) (*ssa.Value, error) {
 			args[i] = value
 		}
 
-		call := f.Append(ssa.Value{Type: typ, Args: args})
-		return call, nil
+		if isSyscall {
+			v := f.Append(&ssa.Syscall{
+				Arguments: ssa.Arguments{Args: args},
+				HasToken:  ssa.HasToken{Source: expr.Token},
+			})
+
+			return v, nil
+		} else {
+			v := f.Append(&ssa.Call{
+				Arguments: ssa.Arguments{Args: args},
+				HasToken:  ssa.HasToken{Source: expr.Token},
+			})
+
+			return v, nil
+		}
 
 	case token.Dot:
 		name := fmt.Sprintf("%s.%s", expr.Children[0].String(f.File.Bytes), expr.Children[1].String(f.File.Bytes))
-		return f.AppendFunction(name), nil
+		v := f.AppendFunction(name)
+		v.Source = expr.Children[1].Token
+		return v, nil
 	}
 
 	return nil, nil

src/core/Function.go

@@ -10,14 +10,14 @@ import (
 
 // Function is the smallest unit of code.
 type Function struct {
-	ssa.Function
+	ssa.IR
 	Name        string
 	UniqueName  string
 	File        *fs.File
 	Input       []*Parameter
 	Output      []*Parameter
 	Body        token.List
-	Identifiers map[string]*ssa.Value
+	Identifiers map[string]ssa.Value
 	Err         error
 }
 
@@ -27,9 +27,11 @@ func NewFunction(name string, file *fs.File) *Function {
 		Name:        name,
 		File:        file,
 		UniqueName:  fmt.Sprintf("%s.%s", file.Package, name),
-		Identifiers: make(map[string]*ssa.Value),
-		Function: ssa.Function{
-			Blocks: []*ssa.Block{{}},
+		Identifiers: make(map[string]ssa.Value),
+		IR: ssa.IR{
+			Blocks: []*ssa.Block{
+				{Instructions: make([]ssa.Value, 0, 8)},
+			},
 		},
 	}
 }

src/core/errors.go

@@ -24,4 +24,13 @@ func (err *UnknownIdentifier) Error() string {
 	}
 
 	return fmt.Sprintf("Unknown identifier '%s'", err.Name)
+}
+
+// UnusedValue error is created when a value is never used.
+type UnusedValue struct {
+	Value string
+}
+
+func (err *UnusedValue) Error() string {
+	return fmt.Sprintf("Unused value '%s'", err.Value)
 }