// Then put their arguments in walkValues before resetting the dead values
	// in walkValues, because the arguments may also become dead values.
	walkValues := []*Value{}
	for _, v := range b.Values {
		if v.Uses == 0 && v.removeable() {
			walkValues = append(walkValues, v)
		}
	}
	for len(walkValues) != 0 {
		v := walkValues[len(walkValues)-1]