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crypto/cipher: add optimized assembly xorBytes for ARM (NEON + non-NEON) #53154

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58 changes: 58 additions & 0 deletions src/crypto/cipher/xor_arm.go
View file Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,58 @@
// Copyright 2022 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

import (
"internal/cpu"
"unsafe"
)

const wordSize = int(unsafe.Sizeof(uintptr(0)))

var hasNEON = cpu.HWCap&(1<<12) != 0

func isAligned(a *byte) bool {
return uintptr(unsafe.Pointer(a))%uintptr(wordSize) == 0
}

// 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]

if hasNEON {
xorBytesNEON32(&dst[0], &a[0], &b[0], n)
} else if isAligned(&dst[0]) && isAligned(&a[0]) && isAligned(&b[0]) {
xorBytesARM32(&dst[0], &a[0], &b[0], n)
} else {
safeXORBytes(dst, a, b, n)
}
return n
}

// n needs to be smaller or equal than the length of a and b.
func safeXORBytes(dst, a, b []byte, n int) {
for i := 0; i < n; i++ {
dst[i] = a[i] ^ b[i]
}
}

func xorWords(dst, a, b []byte) {
xorBytes(dst, a, b)
}

//go:noescape
func xorBytesARM32(dst, a, b *byte, n int)

//go:noescape
func xorBytesNEON32(dst, a, b *byte, n int)
114 changes: 114 additions & 0 deletions src/crypto/cipher/xor_arm.s
View file Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,114 @@
// Copyright 2022 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 xorBytesARM32(dst, a, b *byte, n int)
TEXT ·xorBytesARM32(SB), NOSPLIT|NOFRAME, 0ドル
MOVW dst+0(FP), R0
MOVW a+4(FP), R1
MOVW b+8(FP), R2
MOVW n+12(FP), R3
CMP 4,ドル R3
BLT less_than4

loop_4:
MOVW.P 4(R1), R4
MOVW.P 4(R2), R5
EOR R4, R5, R5
MOVW.P R5, 4(R0)

SUB 4,ドル R3
CMP 4,ドル R3
BGE loop_4

less_than4:
CMP 2,ドル R3
BLT less_than2
MOVH.P 2(R1), R4
MOVH.P 2(R2), R5
EOR R4, R5, R5
MOVH.P R5, 2(R0)

SUB 2,ドル R3

less_than2:
CMP 0,ドル R3
BEQ end
MOVB (R1), R4
MOVB (R2), R5
EOR R4, R5, R5
MOVB R5, (R0)
end:
RET

// func xorBytesNEON32(dst, a, b *byte, n int)
TEXT ·xorBytesNEON32(SB), NOSPLIT|NOFRAME, 0ドル
MOVW dst+0(FP), R0
MOVW a+4(FP), R1
MOVW b+8(FP), R2
MOVW n+12(FP), R3
CMP 32,ドル R3
BLT less_than32

loop_32:
WORD 0ドルxF421020D // vld1.u8 {q0, q1}, [r1]!
WORD 0ドルxF422420D // vld1.u8 {q2, q3}, [r2]!
WORD 0ドルxF3004154 // veor q2, q0, q2
WORD 0ドルxF3026156 // veor q3, q1, q3
WORD 0ドルxF400420D // vst1.u8 {q2, q3}, [r0]!

SUB 32,ドル R3
CMP 32,ドル R3
BGE loop_32

less_than32:
CMP 16,ドル R3
BLT less_than16
WORD 0ドルxF4210A0D // vld1.u8 q0, [r1]!
WORD 0ドルxF4222A0D // vld1.u8 q1, [r2]!
WORD 0ドルxF3002152 // veor q1, q0, q1
WORD 0ドルxF4002A0D // vst1.u8 {q1}, [r0]!

SUB 16,ドル R3

less_than16:
CMP 8,ドル R3
BLT less_than8
WORD 0ドルxF421070D // vld1.u8 d0, [r1]!
WORD 0ドルxF422170D // vld1.u8 d1, [r2]!
WORD 0ドルxF3001111 // veor d1, d0, d1
WORD 0ドルxF400170D // vst1.u8 {d1}, [r0]!

SUB 8,ドル R3

less_than8:
CMP 4,ドル R3
BLT less_than4
MOVW.P 4(R1), R4
MOVW.P 4(R2), R5
EOR R4, R5, R5
MOVW.P R5, 4(R0)

SUB 4,ドル R3

less_than4:
CMP 2,ドル R3
BLT less_than2
MOVH.P 2(R1), R4
MOVH.P 2(R2), R5
EOR R4, R5, R5
MOVH.P R5, 2(R0)

SUB 2,ドル R3

less_than2:
CMP 0,ドル R3
BEQ end
MOVB (R1), R4
MOVB (R2), R5
EOR R4, R5, R5
MOVB R5, (R0)
end:
RET
17 changes: 8 additions & 9 deletions src/crypto/cipher/xor_generic.go
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build !amd64 && !ppc64 && !ppc64le && !arm64
//go:build !amd64 && !ppc64 && !ppc64le && !arm64 && !arm

package cipher

Expand All @@ -23,14 +23,9 @@ func xorBytes(dst, a, b []byte) int {
}

switch {
case supportsUnaligned:
case supportsUnaligned || (isAligned(&dst[0]) && isAligned(&a[0]) && isAligned(&b[0])):
fastXORBytes(dst, a, b, n)
default:
// TODO(hanwen): if (dst, a, b) have common alignment
// we could still try fastXORBytes. It is not clear
// how often this happens, and it's only worth it if
// the block encryption itself is hardware
// accelerated.
safeXORBytes(dst, a, b, n)
}
return n
Expand All @@ -39,8 +34,12 @@ func xorBytes(dst, a, b []byte) int {
const wordSize = int(unsafe.Sizeof(uintptr(0)))
const supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" || runtime.GOARCH == "s390x"

func isAligned(a *byte) bool {
return uintptr(unsafe.Pointer(a))%uintptr(wordSize) == 0
}

// fastXORBytes xors in bulk. It only works on architectures that
// support unaligned read/writes.
// support unaligned read/writes, or if dst, a, b are all aligned.
// n needs to be smaller or equal than the length of a and b.
func fastXORBytes(dst, a, b []byte, n int) {
// Assert dst has enough space
Expand Down Expand Up @@ -83,7 +82,7 @@ func fastXORWords(dst, a, b []byte) {
// fastXORWords XORs multiples of 4 or 8 bytes (depending on architecture.)
// The slice arguments a and b are assumed to be of equal length.
func xorWords(dst, a, b []byte) {
if supportsUnaligned {
if supportsUnaligned || (isAligned(&dst[0]) && isAligned(&a[0]) && isAligned(&b[0])) {
fastXORWords(dst, a, b)
} else {
safeXORBytes(dst, a, b, len(b))
Expand Down

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