1 files changed, 40 insertions, 2 deletions
diff --git a/libgo/go/runtime/string_test.go b/libgo/go/runtime/string_test.go
index 555a7fc7ef9..03327bbb1e2 100644
--- a/libgo/go/runtime/string_test.go
+++ b/libgo/go/runtime/string_test.go
@@ -9,6 +9,7 @@ import (
 	"strconv"
 	"strings"
 	"testing"
+	"unicode/utf8"
 )
 
 // Strings and slices that don't escape and fit into tmpBuf are stack allocated,
@@ -110,6 +111,43 @@ var stringdata = []struct{ name, data string }{
 	{"MixedLength", "$Ѐࠀက퀀𐀀\U00040000\U0010FFFF"},
 }
 
+var sinkInt int
+
+func BenchmarkRuneCount(b *testing.B) {
+	// Each sub-benchmark counts the runes in a string in a different way.
+	b.Run("lenruneslice", func(b *testing.B) {
+		for _, sd := range stringdata {
+			b.Run(sd.name, func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					sinkInt += len([]rune(sd.data))
+				}
+			})
+		}
+	})
+	b.Run("rangeloop", func(b *testing.B) {
+		for _, sd := range stringdata {
+			b.Run(sd.name, func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					n := 0
+					for range sd.data {
+						n++
+					}
+					sinkInt += n
+				}
+			})
+		}
+	})
+	b.Run("utf8.RuneCountInString", func(b *testing.B) {
+		for _, sd := range stringdata {
+			b.Run(sd.name, func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					sinkInt += utf8.RuneCountInString(sd.data)
+				}
+			})
+		}
+	})
+}
+
 func BenchmarkRuneIterate(b *testing.B) {
 	b.Run("range", func(b *testing.B) {
 		for _, sd := range stringdata {
@@ -125,7 +163,7 @@ func BenchmarkRuneIterate(b *testing.B) {
 		for _, sd := range stringdata {
 			b.Run(sd.name, func(b *testing.B) {
 				for i := 0; i < b.N; i++ {
-					for _ = range sd.data {
+					for range sd.data {
 					}
 				}
 			})
@@ -135,7 +173,7 @@ func BenchmarkRuneIterate(b *testing.B) {
 		for _, sd := range stringdata {
 			b.Run(sd.name, func(b *testing.B) {
 				for i := 0; i < b.N; i++ {
-					for _, _ = range sd.data {
+					for range sd.data {
 					}
 				}
 			})