--- /dev/null
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cipher
+
+// xorBytes xors the bytes in a and b. The destination should have enough
+// space, otherwise xorBytes will panic. Returns the number of bytes xor'd.
+func xorBytes(dst, a, b []byte) int {
+ n := len(a)
+ if len(b) < n {
+ n = len(b)
+ }
+ if n == 0 {
+ return 0
+ }
+ // make sure dst has enough space
+ _ = dst[n-1]
+
+ xorBytesARM64(&dst[0], &a[0], &b[0], n)
+ return n
+}
+
+func xorWords(dst, a, b []byte) {
+ xorBytes(dst, a, b)
+}
+
+//go:noescape
+func xorBytesARM64(dst, a, b *byte, n int)
--- /dev/null
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+// func xorBytesARM64(dst, a, b *byte, n int)
+TEXT ·xorBytesARM64(SB), NOSPLIT|NOFRAME, $0
+ MOVD dst+0(FP), R0
+ MOVD a+8(FP), R1
+ MOVD b+16(FP), R2
+ MOVD n+24(FP), R3
+ CMP $64, R3
+ BLT tail
+loop_64:
+ VLD1.P 64(R1), [V0.B16, V1.B16, V2.B16, V3.B16]
+ VLD1.P 64(R2), [V4.B16, V5.B16, V6.B16, V7.B16]
+ VEOR V0.B16, V4.B16, V4.B16
+ VEOR V1.B16, V5.B16, V5.B16
+ VEOR V2.B16, V6.B16, V6.B16
+ VEOR V3.B16, V7.B16, V7.B16
+ VST1.P [V4.B16, V5.B16, V6.B16, V7.B16], 64(R0)
+ SUBS $64, R3
+ CMP $64, R3
+ BGE loop_64
+tail:
+ // quick end
+ CBZ R3, end
+ TBZ $5, R3, less_than32
+ VLD1.P 32(R1), [V0.B16, V1.B16]
+ VLD1.P 32(R2), [V2.B16, V3.B16]
+ VEOR V0.B16, V2.B16, V2.B16
+ VEOR V1.B16, V3.B16, V3.B16
+ VST1.P [V2.B16, V3.B16], 32(R0)
+less_than32:
+ TBZ $4, R3, less_than16
+ LDP.P 16(R1), (R11, R12)
+ LDP.P 16(R2), (R13, R14)
+ EOR R11, R13, R13
+ EOR R12, R14, R14
+ STP.P (R13, R14), 16(R0)
+less_than16:
+ TBZ $3, R3, less_than8
+ MOVD.P 8(R1), R11
+ MOVD.P 8(R2), R12
+ EOR R11, R12, R12
+ MOVD.P R12, 8(R0)
+less_than8:
+ TBZ $2, R3, less_than4
+ MOVWU.P 4(R1), R13
+ MOVWU.P 4(R2), R14
+ EORW R13, R14, R14
+ MOVWU.P R14, 4(R0)
+less_than4:
+ TBZ $1, R3, less_than2
+ MOVHU.P 2(R1), R15
+ MOVHU.P 2(R2), R16
+ EORW R15, R16, R16
+ MOVHU.P R16, 2(R0)
+less_than2:
+ TBZ $0, R3, end
+ MOVBU (R1), R17
+ MOVBU (R2), R19
+ EORW R17, R19, R19
+ MOVBU R19, (R0)
+end:
+ RET