diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index c0d58f76d4..b286470e2d 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -3163,12 +3163,11 @@ func init() {
 			return s.newValue1(ssa.OpBitLen64, types.Types[TINT], x)
 		},
 		sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64)
-	// Note: disabled on AMD64 because the Go code is faster!
-	// addF("math/bits", "Len8",
-	// 	func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
-	// 		return s.newValue1(ssa.OpBitLen8, types.Types[TINT], args[0])
-	// 	},
-	// 	sys.AMD64)
+	addF("math/bits", "Len8",
+		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
+			return s.newValue1(ssa.OpBitLen8, types.Types[TINT], args[0])
+		},
+		sys.AMD64)
 	addF("math/bits", "Len",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			if s.config.PtrSize == 4 {
diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go
index 39f46c70c8..55a2c943f6 100644
--- a/test/codegen/mathbits.go
+++ b/test/codegen/mathbits.go
@@ -45,7 +45,7 @@ func LeadingZeros16(n uint16) int {
 }
 
 func LeadingZeros8(n uint8) int {
-	// amd64 LeadingZeros8 not intrinsified (see ssa.go)
+	// amd64:"BSRL","LEAL",-"CMOVQEQ"
 	// s390x:"FLOGR"
 	// arm:"CLZ" arm64:"CLZ"
 	// mips:"CLZ"
@@ -89,7 +89,7 @@ func Len16(n uint16) int {
 }
 
 func Len8(n uint8) int {
-	// amd64 Len8 not intrisified (see ssa.go)
+	// amd64:"BSRL","LEAL",-"CMOVQEQ"
 	// s390x:"FLOGR"
 	// arm:"CLZ" arm64:"CLZ"
 	// mips:"CLZ"