runtime: Implement faster equals for strings and bytes.

(amd64)
benchmark           old ns/op    new ns/op    delta
BenchmarkEqual0            16            6  -63.15%
BenchmarkEqual9            22            7  -65.37%
BenchmarkEqual32           36            9  -74.91%
BenchmarkEqual4K         2187          120  -94.51%

benchmark            old MB/s     new MB/s  speedup
BenchmarkEqual9        392.22      1134.38    2.89x
BenchmarkEqual32       866.72      3457.39    3.99x
BenchmarkEqual4K      1872.73     33998.87   18.15x

(386)
benchmark           old ns/op    new ns/op    delta
BenchmarkEqual0            16            5  -63.85%
BenchmarkEqual9            22            7  -67.84%
BenchmarkEqual32           34           12  -64.94%
BenchmarkEqual4K         2196          113  -94.85%

benchmark            old MB/s     new MB/s  speedup
BenchmarkEqual9        405.81      1260.18    3.11x
BenchmarkEqual32       919.55      2631.21    2.86x
BenchmarkEqual4K      1864.85     36072.54   19.34x

Update #3751

R=bradfitz, r, khr, dave, remyoudompheng, fullung, minux.ma, ality
CC=golang-dev
https://golang.org/cl/8056043

1 files changed, 28 insertions, 0 deletions

diff --git a/src/pkg/runtime/string_test.go b/src/pkg/runtime/string_test.go
index 6ba3c1d292..df3ff06a7d 100644
--- a/src/pkg/runtime/string_test.go
+++ b/src/pkg/runtime/string_test.go
@@ -47,3 +47,31 @@ func BenchmarkCompareStringDifferentLength(b *testing.B) {
 		}
 	}
 }
+
+func BenchmarkCompareStringBigUnaligned(b *testing.B) {
+	bytes := make([]byte, 0, 1<<20)
+	for len(bytes) < 1<<20 {
+		bytes = append(bytes, "Hello Gophers!"...)
+	}
+	s1, s2 := string(bytes), "hello"+string(bytes)
+	for i := 0; i < b.N; i++ {
+		if s1 != s2[len("hello"):] {
+			b.Fatal("s1 != s2")
+		}
+	}
+	b.SetBytes(int64(len(s1)))
+}
+
+func BenchmarkCompareStringBig(b *testing.B) {
+	bytes := make([]byte, 0, 1<<20)
+	for len(bytes) < 1<<20 {
+		bytes = append(bytes, "Hello Gophers!"...)
+	}
+	s1, s2 := string(bytes), string(bytes)
+	for i := 0; i < b.N; i++ {
+		if s1 != s2 {
+			b.Fatal("s1 != s2")
+		}
+	}
+	b.SetBytes(int64(len(s1)))
+}