func decomposeUserStructInto(f *Func, name *LocalSlot, slots []*LocalSlot) []*LocalSlot {
	fnames := []*LocalSlot{} // slots for struct in name
	t := name.Type
	n := t.NumFields()

	for i := 0; i < n; i++ {
		fs := f.SplitStruct(name, i)
		fnames = append(fnames, fs)
		// arrays and structs will be decomposed further, so
		// there's no need to record a name
		if !fs.Type.IsArray() && !fs.Type.IsStruct() {
			slots = maybeAppend(f, slots, fs)

	}
	return f.SplitSlot(name, ".hi", t.Size(), t), f.SplitSlot(name, ".lo", 0, types.Types[types.TUINT32])
}

func (f *Func) SplitStruct(name *LocalSlot, i int) *LocalSlot {
	st := name.Type
	return f.SplitSlot(name, st.FieldName(i), st.FieldOff(i), st.FieldType(i))
}
func (f *Func) SplitArray(name *LocalSlot) *LocalSlot {
	n := name.N