runtime: unify memeq and memequal

They do the same thing, except memequal also has the short-circuit
check if the two pointers are equal.

A) We might as well always do the short-circuit check, it is only 2 instructions.
B) The extra function call (memequal->memeq) is expensive.

benchmark                 old ns/op     new ns/op     delta
BenchmarkArrayEqual-8     8.56          5.31          -37.97%

No noticeable affect on the former memeq user (maps).

Fixes #14302

Change-Id: I85d1ada59ed11e64dd6c54667f79d32cc5f81948
Reviewed-on: https://go-review.googlesource.com/19843
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/runtime/string_test.go b/src/runtime/string_test.go
index 150a25520a..37b75c1a89 100644
--- a/src/runtime/string_test.go
+++ b/src/runtime/string_test.go
@@ -102,6 +102,17 @@ func BenchmarkRuneIterate2(b *testing.B) {
 	}
 }
 
+func BenchmarkArrayEqual(b *testing.B) {
+	a1 := [16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
+	a2 := [16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if a1 != a2 {
+			b.Fatal("not equal")
+		}
+	}
+}
+
 func TestStringW(t *testing.T) {
 	strings := []string{
 		"hello",