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) 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)))
}
func (v *CompileVisitor) PopType(t ast.Type) {
switch t.Form {
case ast.Tuple:
for _, o := range t.Params.Objects {
v.PopType(*o.Type)
}
case ast.Basic:
switch t.N {
case ast.String:
v.Append(x86.AddL(x86.Imm32(8), x86.ESP))
default:
panic(fmt.Sprintf("I don't know how to pop basic type %s", t))
}
default:
panic(fmt.Sprintf("I don't know how to pop type %s", t.Form))
}
}
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) 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))
}
}
func (v *StackVariable) InMemory() x86.Memory {
return x86.Memory{x86.Imm32(v.Offset), x86.ESP, nil, nil}
}