runtime: faster string equality.

benchmark                                old ns/op    new ns/op    delta
BenchmarkCompareStringEqual                     51           35  -30.20%
BenchmarkCompareStringIdentical                 51            7  -85.71%
BenchmarkCompareStringSameLength                25           18  -28.29%
BenchmarkCompareStringDifferentLength            2            2   +1.46%

R=golang-dev, rsc
CC=golang-dev, remy
https://golang.org/cl/6450092

1 files changed, 45 insertions, 0 deletions

diff --git a/src/pkg/runtime/string_test.go b/src/pkg/runtime/string_test.go
new file mode 100644
index 0000000000..8f13f0f428
--- /dev/null
+++ b/src/pkg/runtime/string_test.go
@@ -0,0 +1,45 @@
+package runtime_test
+
+import (
+	"testing"
+)
+
+func BenchmarkCompareStringEqual(b *testing.B) {
+	bytes := []byte("Hello Gophers!")
+	s1, s2 := string(bytes), string(bytes)
+	for i := 0; i < b.N; i++ {
+		if s1 != s2 {
+			b.Fatal("s1 != s2")
+		}
+	}
+}
+
+func BenchmarkCompareStringIdentical(b *testing.B) {
+	s1 := "Hello Gophers!"
+	s2 := s1
+	for i := 0; i < b.N; i++ {
+		if s1 != s2 {
+			b.Fatal("s1 != s2")
+		}
+	}
+}
+
+func BenchmarkCompareStringSameLength(b *testing.B) {
+	s1 := "Hello Gophers!"
+	s2 := "Hello, Gophers"
+	for i := 0; i < b.N; i++ {
+		if s1 == s2 {
+			b.Fatal("s1 == s2")
+		}
+	}
+}
+
+func BenchmarkCompareStringDifferentLength(b *testing.B) {
+	s1 := "Hello Gophers!"
+	s2 := "Hello, Gophers!"
+	for i := 0; i < b.N; i++ {
+		if s1 == s2 {
+			b.Fatal("s1 == s2")
+		}
+	}
+}