// If it does not exist, it creates it.
func (ctxt *Link) Lookup(name string) *LSym {
	return ctxt.LookupInit(name, nil)
}

// LookupInit looks up the symbol with name name.
// If it does not exist, it creates it and
// passes it to init for one-time initialization.
func (ctxt *Link) LookupInit(name string, init func(s *LSym)) *LSym {
	ctxt.hashmu.Lock()
	s := ctxt.hash[name]
	if s == nil {

	// which are very similar across functions.
	// Dedup them when possible.
	hash := base64.StdEncoding.EncodeToString(buf.data)
	symname := fmt.Sprintf("%d.%s", len(buf.data), hash)
	return ctxt.LookupInit("go:sehuw."+symname, func(s *obj.LSym) {
		s.WriteBytes(ctxt, 0, buf.data)
		s.Type = objabi.SSEHUNWINDINFO
		s.Set(obj.AttrDuplicateOK, true)
		s.Set(obj.AttrLocal, true)
		s.Set(obj.AttrContentAddressable, true)

		var sym *obj.LSym
		if p.As == obj.ADUFFZERO {
			sym = c.ctxt.Lookup("runtime.duffzero")
		} else {
			sym = c.ctxt.Lookup("runtime.duffcopy")
		}
		// Retrieve or create the TOC anchor.
		symtoc := c.ctxt.LookupInit("TOC."+sym.Name, func(s *obj.LSym) {
			s.Type = objabi.SDATA
			s.Set(obj.AttrDuplicateOK, true)
			s.Set(obj.AttrStatic, true)
			c.ctxt.Data = append(c.ctxt.Data, s)
			s.WriteAddr(c.ctxt, 0, 8, sym, 0)
		})

// given name, type and value.
func (ctxt *Link) DwarfIntConst(name, typename string, val int64) {
	myimportpath := ctxt.Pkgpath
	if myimportpath == "" {
		return
	}
	s := ctxt.LookupInit(dwarf.ConstInfoPrefix+myimportpath, func(s *LSym) {
		s.Type = objabi.SDWARFCONST
		ctxt.Data = append(ctxt.Data, s)
	})

	}
	q := obj.Appendp(p, newprog)
	q.RegTo2 = 1
	r := obj.Appendp(q, newprog)
	r.RegTo2 = 1
	q.As = obj.ACALL
	thunkname := "__x86.get_pc_thunk." + strings.ToLower(rconv(int(dst)))
	q.To.Sym = ctxt.LookupInit(thunkname, func(s *obj.LSym) { s.Set(obj.AttrLocal, true) })
	q.To.Type = obj.TYPE_MEM
	q.To.Name = obj.NAME_EXTERN
	r.As = p.As
	r.Scond = p.Scond
	r.From = p.From
	r.RestArgs = p.RestArgs
	r.Reg = p.Reg

		// Unfortunate.
		return
	}

	wfn := e.curfn.WrappedFunc
	if wfn == nil {
		return
	}

	wsym := wfn.Linksym()
	x := base.Ctxt.LookupInit(fmt.Sprintf("%s.wrapinfo", wsym.Name), func(x *obj.LSym) {
		objw.SymPtrOff(x, 0, wsym)
		x.Set(obj.AttrContentAddressable, true)
	})
	e.curfn.LSym.Func().WrapInfo = x