1// Copyright 2018 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build !purego
6
7#include "textflag.h"
8
9// func xorBytes(dst, a, b *byte, n int)
10TEXT ·xorBytes(SB), NOSPLIT, $0
11	MOVQ  dst+0(FP), BX
12	MOVQ  a+8(FP), SI
13	MOVQ  b+16(FP), CX
14	MOVQ  n+24(FP), DX
15	TESTQ $15, DX            // AND 15 & len, if not zero jump to not_aligned.
16	JNZ   not_aligned
17
18aligned:
19	MOVQ $0, AX // position in slices
20
21	PCALIGN $16
22loop16b:
23	MOVOU (SI)(AX*1), X0   // XOR 16byte forwards.
24	MOVOU (CX)(AX*1), X1
25	PXOR  X1, X0
26	MOVOU X0, (BX)(AX*1)
27	ADDQ  $16, AX
28	CMPQ  DX, AX
29	JNE   loop16b
30	RET
31
32	PCALIGN $16
33loop_1b:
34	SUBQ  $1, DX           // XOR 1byte backwards.
35	MOVB  (SI)(DX*1), DI
36	MOVB  (CX)(DX*1), AX
37	XORB  AX, DI
38	MOVB  DI, (BX)(DX*1)
39	TESTQ $7, DX           // AND 7 & len, if not zero jump to loop_1b.
40	JNZ   loop_1b
41	CMPQ  DX, $0           // if len is 0, ret.
42	JE    ret
43	TESTQ $15, DX          // AND 15 & len, if zero jump to aligned.
44	JZ    aligned
45
46not_aligned:
47	TESTQ $7, DX           // AND $7 & len, if not zero jump to loop_1b.
48	JNE   loop_1b
49	SUBQ  $8, DX           // XOR 8bytes backwards.
50	MOVQ  (SI)(DX*1), DI
51	MOVQ  (CX)(DX*1), AX
52	XORQ  AX, DI
53	MOVQ  DI, (BX)(DX*1)
54	CMPQ  DX, $16          // if len is greater or equal 16 here, it must be aligned.
55	JGE   aligned
56
57ret:
58	RET
59