func (v *CompileVisitor) Declare(vname string, t *ast.Type) {
switch SizeOnStack(t) {
case 4:
v.Append(x86.Commented(x86.PushL(x86.Imm32(0)), "This is variable "+vname))
case 8:
v.Append(x86.Commented(x86.PushL(x86.Imm32(0)), "This is variable "+vname))
v.Append(x86.Commented(x86.PushL(x86.Imm32(0)), "This is variable "+vname))
default:
panic(fmt.Sprintf("I don't handle variables with length %s", SizeOnStack(t)))
}
v.Stack.DefineVariable(vname, t)
}
func (v *CompileVisitor) Visit(n0 ast.Node) (w ast.Visitor) {
// The following only handles functions (not methods)
if n, ok := n0.(*ast.FuncDecl); ok && n.Recv == nil {
v.FunctionPrologue(n)
for _, statement := range n.Body.List {
v.CompileStatement(statement)
}
v.FunctionPostlogue()
v.Append(x86.GlobalSymbol("return_" + n.Name.Name))
v.Append(x86.Commented(x86.PopL(x86.EAX), "Pop the return address"))
// Pop off function arguments...
fmt.Println("Function", v.Stack.Name, "has stack size", v.Stack.Size)
fmt.Println("Function", v.Stack.Name, "has return values size", v.Stack.ReturnSize)
v.Append(x86.Commented(x86.AddL(x86.Imm32(v.Stack.Size-4-v.Stack.ReturnSize), x86.ESP),
"Popping "+v.Stack.Name+" arguments."))
// Then we return!
v.Append(x86.RawAssembly("\tjmp *%eax"))
v.Stack = v.Stack.Parent
return nil // No need to peek inside the func declaration!
}
return v
}
func (v *CompileVisitor) FunctionPostlogue() {
// First we roll back the stack from where we started...
for v.Stack.Name == "_" {
// We need to pop off any extra layers of stack we've added...
if v.Stack.Size > 0 {
v.Append(x86.Commented(x86.AddL(x86.Imm32(v.Stack.Size), x86.ESP),
"We stored this much on the stack so far."))
}
v.Stack = v.Stack.Parent // We've popped off the arguments...
}
// Now jump to the "real" postlogue. This is a little stupid, but I
// expect it'll come in handy when I implement defer (not to mention
// panic/recover).
v.Append(x86.Jmp(x86.Symbol("return_" + v.Stack.Name)))
}
// PopTo returns code to save data from the stack into the variable.
// It also changes the stack size accordingly.
func (s *Stack) PopTo(name string) x86.X86 {
v := s.Lookup(name)
off := SizeOnStack(v.Type())
if TypeToSize(v.Type()) != off {
panic("I can't yet handle types with sizes that aren't a multiple of 4")
}
comment := "Popping to variable " + v.Name()
if v.Name() == "_" {
comment = fmt.Sprint("Popping to ", name, " of type ", PrettyType(v.Type()), " at ", v.InMemory())
}
code := []x86.X86{x86.Comment(s.PrettyComments())}
switch off {
case 4:
s.Size -= off
vnew := s.Lookup(name) // Its location relative to stack may have changed!
return x86.RawAssembly(x86.Assembly([]x86.X86{
x86.PopL(x86.EAX),
x86.Commented(x86.MovL(x86.EAX, vnew.InMemory()), comment),
}))
case 8:
s.Size -= 4
vnew := s.Lookup(name) // Its location relative to stack may have changed!
code = append(code,
x86.PopL(x86.EAX),
x86.Commented(x86.MovL(x86.EAX, vnew.InMemory()), comment))
s.Size -= 4
vnew = s.Lookup(name) // Its location relative to stack may have changed again!
code = append(code,
x86.PopL(x86.EAX),
x86.Commented(x86.MovL(x86.EAX, vnew.InMemory().Add(4)), comment))
return x86.RawAssembly(x86.Assembly(code))
default:
panic(fmt.Sprintf("I don't pop variables with length %s", SizeOnStack(v.Type())))
}
panic("This can't happen")
}
func (v StringVisitor) Visit(n0 ast.Node) (w ast.Visitor) {
//fmt.Printf("in StringVisitor, n0 is %s of type %T\n", n0, n0)
if n, ok := n0.(*ast.BasicLit); ok && n != nil && n.Kind == token.STRING {
str, err := strconv.Unquote(string(n.Value))
if err != nil {
panic(err)
}
sanitize := func(rune int) int {
if unicode.IsLetter(rune) {
return rune
}
return -1
}
fmt.Println("string literals are: ", v.string_literals)
if _, ok := v.string_literals[str]; !ok {
strname := "string_" + strings.Map(sanitize, str)
for {
// See if our strname is valid...
nameexists := false
for _, n := range v.string_literals {
if n == strname {
nameexists = true
}
}
if !nameexists {
break // we've got a unique name already!
}
strname = strname + "X"
}
*v.assembly = append(*v.assembly,
x86.Symbol(strname),
x86.Commented(x86.Ascii(str), "a non-null-terminated string"))
v.string_literals[str] = strname
fmt.Println("Got new string literal: ", str)
}
}
return v
}
func (v *CompileVisitor) FunctionPrologue(fn *ast.FuncDecl) {
v.Stack = v.Stack.New(fn.Name.Name)
ftype := ast.NewType(ast.Function)
ftype.N = uint(fn.Type.Results.NumFields())
ftype.Params = ast.NewScope(nil)
fmt.Println("Working on function", fn.Name.Name)
if fn.Type.Results != nil {
resultnum := 0
for _, resultfield := range fn.Type.Results.List {
names := []string{"_"}
if resultfield.Names != nil {
names = []string{}
for _, i := range resultfield.Names {
names = append(names, i.Name)
}
}
t := TypeExpression(resultfield.Type)
for _, n := range names {
ftype.Params.Insert(&ast.Object{ast.Fun, n, t, resultfield, 0})
resultnum++
v.Stack.DefineVariable(n, t, fmt.Sprintf("return_value_%d", resultnum))
// The return values are actually allocated elsewhere... here
// we just need to define the function type properly so it
// gets called properly.
}
}
}
fmt.Println("Stack size after results is", v.Stack.Size)
v.Stack.ReturnSize = v.Stack.Size
// The arguments are pushed last argument first, so that eventually
// the types of the "later" arguments can depend on the first
// arguments, which seems nice to me.
for pi := len(fn.Type.Params.List) - 1; pi >= 0; pi-- {
paramfield := fn.Type.Params.List[pi]
names := []string{"_"}
if paramfield.Names != nil {
names = []string{}
for _, i := range paramfield.Names {
names = append(names, i.Name)
}
}
t := TypeExpression(paramfield.Type)
for i := len(names) - 1; i >= 0; i-- {
n := names[i]
ftype.Params.Insert(&ast.Object{ast.Fun, n, t, paramfield, 0})
v.Stack.DefineVariable(n, t)
// The function parameters are actually allocated
// elsewhere... here we just need to define the function type
// properly so it gets called properly.
}
}
fmt.Println("Stack size after params is", v.Stack.Size)
v.Stack.DefineVariable("return", IntType)
fmt.Println("Stack size after return is", v.Stack.Size)
v.Stack = v.Stack.New("_")
DefineGlobal(fn.Name.Name, ftype)
// symbol for the start name
pos := myfiles.Position(fn.Pos())
v.Append(x86.Commented(x86.GlobalSymbol("main_"+fn.Name.Name),
fmt.Sprint(pos.Filename, ": line ", pos.Line)))
// If we had arguments, we'd want to swap them with the return
// address here...
}
func (v *CompileVisitor) CompileExpression(exp ast.Expr) {
switch e := exp.(type) {
case *ast.BasicLit:
switch e.Kind {
case token.STRING:
str, err := strconv.Unquote(string(e.Value))
if err != nil {
panic(err)
}
n, ok := v.string_literals[str]
if !ok {
panic(fmt.Sprintf("I don't recognize the string: %s", string(e.Value)))
}
v.Append(
x86.Commented(x86.PushL(x86.Symbol(n)), "Pushing string literal "+string(e.Value)),
x86.PushL(x86.Imm32(len(str))))
v.Stack.Push(StringType) // let the stack know we've pushed a literal
default:
panic(fmt.Sprintf("I don't know how to deal with literal: %s", e))
}
case *ast.CallExpr:
if fn, ok := e.Fun.(*ast.Ident); ok {
pos := myfiles.Position(fn.Pos())
switch fn.Name {
case "println", "print":
if len(e.Args) != 1 {
panic(fmt.Sprintf("%s expects just one argument, not %d", fn.Name, len(e.Args)))
}
argtype := ExprType(e.Args[0], v.Stack)
if argtype.N != ast.String || argtype.Form != ast.Basic {
panic(fmt.Sprintf("Argument to %s has type %s but should have type string!",
fn.Name, argtype))
}
v.Stack = v.Stack.New("arguments")
v.CompileExpression(e.Args[0])
v.Append(x86.Commented(x86.Call(x86.Symbol(fn.Name)),
fmt.Sprint(pos.Filename, ": line ", pos.Line)))
v.Stack = v.Stack.Parent // A hack to let the callee clean up arguments
default:
// This must not be a built-in function...
functype := v.Stack.Lookup(fn.Name)
if functype.Type().Form != ast.Function {
panic("Function " + fn.Name + " is not actually a function!")
}
for i := 0; i < int(functype.Type().N); i++ {
// Put zeros on the stack for the return values (and define these things)
v.Declare(functype.Type().Params.Objects[i].Name,
functype.Type().Params.Objects[i].Type)
}
v.Stack = v.Stack.New("arguments")
for i := len(e.Args) - 1; i >= 0; i-- {
v.CompileExpression(e.Args[i])
}
// FIXME: I assume here that there is no return value!
v.Append(x86.Commented(x86.Call(x86.Symbol("main_"+fn.Name)),
fmt.Sprint(pos.Filename, ": line ", pos.Line)))
v.Stack = v.Stack.Parent // A hack to let the callee clean up arguments
}
} else {
panic(fmt.Sprintf("I don't know how to deal with complicated function: %s", e.Fun))
}
case *ast.Ident:
evar := v.Stack.Lookup(e.Name)
switch SizeOnStack(evar.Type()) {
case 4:
v.Append(x86.Commented(x86.MovL(evar.InMemory(), x86.EAX), "Reading variable "+e.Name))
v.Append(x86.PushL(x86.EAX))
v.Stack.DefineVariable("_copy_of_"+e.Name, evar.Type())
case 8:
v.Append(x86.Comment(fmt.Sprintf("The offset of %s is %s", e.Name, evar.InMemory())))
v.Append(x86.Commented(x86.MovL(evar.InMemory().Add(4), x86.EAX),
"Reading variable "+e.Name))
v.Append(x86.MovL(evar.InMemory(), x86.EBX))
v.Append(x86.PushL(x86.EAX))
v.Append(x86.PushL(x86.EBX))
v.Stack.DefineVariable("_copy_of_"+e.Name, evar.Type())
default:
panic(fmt.Sprintf("I don't handle variables with length %s", SizeOnStack(evar.Type())))
}
default:
panic(fmt.Sprintf("I can't handle expressions such as: %T value %s", exp, exp))
}
}
