crypto/subtle: add additional benchmarks for XORBytes

Provide alignment benchmarks for XORBytes, as well as including
8192 byte blocks in the existing benchmarks. This allows us to
better evaluate performance with unaligned inputs.

Change-Id: Iad497c594c0425389ae02ca848aede5cb0ac3afd
Reviewed-on: https://go-review.googlesource.com/c/go/+/639316
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Filippo Valsorda <[email protected]>
Reviewed-by: Roland Shoemaker <[email protected]>

Author: 4a6f656c

src/crypto/subtle/xor_test.go

@@ -92,7 +92,7 @@ func BenchmarkXORBytes(b *testing.B) {
 	dst := make([]byte, 1<<15)
 	data0 := make([]byte, 1<<15)
 	data1 := make([]byte, 1<<15)
-	sizes := []int64{1 << 3, 1 << 7, 1 << 11, 1 << 15}
+	sizes := []int64{1 << 3, 1 << 7, 1 << 11, 1 << 13, 1 << 15}
 	for _, size := range sizes {
 		b.Run(fmt.Sprintf("%dBytes", size), func(b *testing.B) {
 			s0 := data0[:size]
@@ -105,6 +105,26 @@ func BenchmarkXORBytes(b *testing.B) {
 	}
 }
 
+func BenchmarkXORBytesAlignment(b *testing.B) {
+	dst := make([]byte, 8+1<<11)
+	data0 := make([]byte, 8+1<<11)
+	data1 := make([]byte, 8+1<<11)
+	sizes := []int64{1 << 3, 1 << 7, 1 << 11}
+	for _, size := range sizes {
+		for offset := int64(0); offset < 8; offset++ {
+			b.Run(fmt.Sprintf("%dBytes%dOffset", size, offset), func(b *testing.B) {
+				d := dst[offset : offset+size]
+				s0 := data0[offset : offset+size]
+				s1 := data1[offset : offset+size]
+				b.SetBytes(int64(size))
+				for i := 0; i < b.N; i++ {
+					XORBytes(d, s0, s1)
+				}
+			})
+		}
+	}
+}
+
 func mustPanic(t *testing.T, expected string, f func()) {
 	t.Helper()
 	defer func() {