diff --git a/pkg/controller/node/ipam/cidrset/cidr_set.go b/pkg/controller/node/ipam/cidrset/cidr_set.go
index 088c62511b5..38a0521d2dd 100644
--- a/pkg/controller/node/ipam/cidrset/cidr_set.go
+++ b/pkg/controller/node/ipam/cidrset/cidr_set.go
@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"math/big"
+	"math/bits"
 	"net"
 	"sync"
 )
@@ -77,48 +78,6 @@ func NewCIDRSet(clusterCIDR *net.IPNet, subNetMaskSize int) (*CidrSet, error) {
 	}, nil
 }
 
-// TODO: Remove this function when upgrading to go 1.9
-var len8tab = [256]uint8{
-	0x00, 0x01, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
-	0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
-	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
-	0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
-	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-	0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-	0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
-}
-
-// TODO: Remove this function when upgrading to go 1.9
-// len64 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
-func len64(x uint64) (n int) {
-	if x >= 1<<32 {
-		x >>= 32
-		n = 32
-	}
-	if x >= 1<<16 {
-		x >>= 16
-		n += 16
-	}
-	if x >= 1<<8 {
-		x >>= 8
-		n += 8
-	}
-	return n + int(len8tab[x])
-}
-
-// TODO: Remove this function when upgrading to go 1.9
-// leadingZeros64 returns the number of leading zero bits in x; the result is 64 for x == 0.
-func leadingZeros64(x uint64) int { return 64 - len64(x) }
-
 func (s *CidrSet) indexToCIDRBlock(index int) *net.IPNet {
 	var ip []byte
 	var mask int
@@ -150,8 +109,7 @@ func (s *CidrSet) indexToCIDRBlock(index int) *net.IPNet {
 				if s.clusterMaskSize < halfV6NBits {
 					// see how many bits are needed to reach the left side
 					btl := uint(s.subNetMaskSize - halfV6NBits)
-					// TODO: Replace this with math/bits.LeadingZeros64 when upgrading to go 1.9
-					indexMaxBit := uint(64 - leadingZeros64(uint64(index)))
+					indexMaxBit := uint(64 - bits.LeadingZeros64(uint64(index)))
 					if indexMaxBit > btl {
 						leftClusterIP |= uint64(index) >> btl
 					}