// 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 *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
}