for _, v := range b.Values {
			if !lv.hasStackMap(v) {
				continue
			}

			live := bitvec.New(nvars)
			lv.livevars = append(lv.livevars, live)
		}

		// walk backward, construct maps at each safe point
		index := int32(len(lv.livevars) - 1)

		liveout.Copy(be.liveout)
		for i := len(b.Values) - 1; i >= 0; i-- {
			v := b.Values[i]

			if lv.hasStackMap(v) {

// since it emits PCDATA for the stack map at the call (calls are safe points).
func (s *State) PrepareCall(v *ssa.Value) {
	idx := s.livenessMap.Get(v)
	if !idx.StackMapValid() {
		// See Liveness.hasStackMap.
		if sym, ok := v.Aux.(*ssa.AuxCall); !ok || !(sym.Fn == ir.Syms.WBZero || sym.Fn == ir.Syms.WBMove) {
			base.Fatalf("missing stack map index for %v", v.LongString())
		}
	}