// lookup returns the address of the named variable identified by obj
// that is local to function f or one of its enclosing functions.
// If escaping, the reference comes from a potentially escaping pointer
// expression and the referent must be heap-allocated.
//
func (f *Function) lookup(obj types.Object, escaping bool) Value {
if v, ok := f.objects[obj]; ok {
if escaping {
// Walk up the chain of Captures.
x := v
for {
if c, ok := x.(*Capture); ok {
x = c.Outer
} else {
break
}
}
// By construction, all captures are ultimately Allocs in the
// naive SSA form. Parameters are pre-spilled to the stack.
x.(*Alloc).Heap = true
}
return v // function-local var (address)
}
// Definition must be in an enclosing function;
// plumb it through intervening closures.
if f.Enclosing == nil {
panic("no Value for type.Object " + obj.GetName())
}
v := &Capture{Outer: f.Enclosing.lookup(obj, true)} // escaping
f.objects[obj] = v
f.FreeVars = append(f.FreeVars, v)
return v
}
// addSpilledParam declares a parameter that is pre-spilled to the
// stack; the function body will load/store the spilled location.
// Subsequent lifting will eliminate spills where possible.
//
func (f *Function) addSpilledParam(obj types.Object) {
name := obj.GetName()
param := f.addParam(name, obj.GetType())
spill := &Alloc{
Name_: name + "~", // "~" means "spilled"
Type_: pointer(obj.GetType()),
}
f.objects[obj] = spill
f.Locals = append(f.Locals, spill)
f.emit(spill)
f.emit(&Store{Addr: spill, Val: param})
}
// addNamedLocal creates a local variable, adds it to function f and
// returns it. Its name and type are taken from obj. Subsequent
// calls to f.lookup(obj) will return the same local.
//
// Precondition: f.syntax != nil (i.e. a Go source function).
//
func (f *Function) addNamedLocal(obj types.Object) *Alloc {
l := f.addLocal(obj.GetType(), obj.GetPos())
l.Name_ = obj.GetName()
f.objects[obj] = l
return l
}