1/*
2 * Armv7-A specific checksum implementation using NEON
3 *
4 * Copyright (c) 2020, Arm Limited.
5 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
6 */
7
8#include "networking.h"
9#include "../chksum_common.h"
10
11#ifndef __ARM_NEON
12#pragma GCC target("+simd")
13#endif
14
15#include <arm_neon.h>
16
17unsigned short
18__chksum_arm_simd(const void *ptr, unsigned int nbytes)
19{
20    bool swap = (uintptr_t) ptr & 1;
21    uint64x1_t vsum = { 0 };
22
23    if (unlikely(nbytes < 40))
24    {
25	uint64_t sum = slurp_small(ptr, nbytes);
26	return fold_and_swap(sum, false);
27    }
28
29    /* 8-byte align pointer */
30    /* Inline slurp_head-like code since we use NEON here */
31    Assert(nbytes >= 8);
32    uint32_t off = (uintptr_t) ptr & 7;
33    if (likely(off != 0))
34    {
35	const uint64_t *may_alias ptr64 = align_ptr(ptr, 8);
36	uint64x1_t vword64 = vld1_u64(ptr64);
37	/* Get rid of bytes 0..off-1 */
38	uint64x1_t vmask = vdup_n_u64(ALL_ONES);
39	int64x1_t vshiftl = vdup_n_s64(CHAR_BIT * off);
40	vmask = vshl_u64(vmask, vshiftl);
41	vword64 = vand_u64(vword64, vmask);
42	uint32x2_t vtmp = vreinterpret_u32_u64(vword64);
43	/* Set accumulator */
44	vsum = vpaddl_u32(vtmp);
45	/* Update pointer and remaining size */
46	ptr = (char *) ptr64 + 8;
47	nbytes -= 8 - off;
48    }
49    Assert(((uintptr_t) ptr & 7) == 0);
50
51    /* Sum groups of 64 bytes */
52    uint64x2_t vsum0 = { 0, 0 };
53    uint64x2_t vsum1 = { 0, 0 };
54    uint64x2_t vsum2 = { 0, 0 };
55    uint64x2_t vsum3 = { 0, 0 };
56    const uint32_t *may_alias ptr32 = ptr;
57    for (uint32_t i = 0; i < nbytes / 64; i++)
58    {
59	uint32x4_t vtmp0 = vld1q_u32(ptr32);
60	uint32x4_t vtmp1 = vld1q_u32(ptr32 + 4);
61	uint32x4_t vtmp2 = vld1q_u32(ptr32 + 8);
62	uint32x4_t vtmp3 = vld1q_u32(ptr32 + 12);
63	vsum0 = vpadalq_u32(vsum0, vtmp0);
64	vsum1 = vpadalq_u32(vsum1, vtmp1);
65	vsum2 = vpadalq_u32(vsum2, vtmp2);
66	vsum3 = vpadalq_u32(vsum3, vtmp3);
67	ptr32 += 16;
68    }
69    nbytes %= 64;
70
71    /* Fold vsum1/vsum2/vsum3 into vsum0 */
72    vsum0 = vpadalq_u32(vsum0, vreinterpretq_u32_u64(vsum2));
73    vsum1 = vpadalq_u32(vsum1, vreinterpretq_u32_u64(vsum3));
74    vsum0 = vpadalq_u32(vsum0, vreinterpretq_u32_u64(vsum1));
75
76    /* Add any trailing 16-byte groups */
77    while (likely(nbytes >= 16))
78    {
79	uint32x4_t vtmp0 = vld1q_u32(ptr32);
80	vsum0 = vpadalq_u32(vsum0, vtmp0);
81	ptr32 += 4;
82	nbytes -= 16;
83    }
84    Assert(nbytes < 16);
85
86    /* Fold vsum0 into vsum */
87    {
88	/* 4xu32 (4x32b) -> 2xu64 (2x33b) */
89	vsum0 = vpaddlq_u32(vreinterpretq_u32_u64(vsum0));
90	/* 4xu32 (2x(1b+32b)) -> 2xu64 (2x(0b+32b)) */
91	vsum0 = vpaddlq_u32(vreinterpretq_u32_u64(vsum0));
92	/* 4xu32 (4x32b) -> 2xu64 (2x33b) */
93	Assert((vgetq_lane_u64(vsum0, 0) >> 32) == 0);
94	Assert((vgetq_lane_u64(vsum0, 1) >> 32) == 0);
95	uint32x2_t vtmp = vmovn_u64(vsum0);
96	/* Add to accumulator */
97	vsum = vpadal_u32(vsum, vtmp);
98    }
99
100    /* Add any trailing group of 8 bytes */
101    if (nbytes & 8)
102    {
103	uint32x2_t vtmp = vld1_u32(ptr32);
104	/* Add to accumulator */
105	vsum = vpadal_u32(vsum, vtmp);
106	ptr32 += 2;
107	nbytes -= 8;
108    }
109    Assert(nbytes < 8);
110
111    /* Handle any trailing 1..7 bytes */
112    if (likely(nbytes != 0))
113    {
114	Assert(((uintptr_t) ptr32 & 7) == 0);
115	Assert(nbytes < 8);
116	uint64x1_t vword64 = vld1_u64((const uint64_t *) ptr32);
117	/* Get rid of bytes 7..nbytes */
118	uint64x1_t vmask = vdup_n_u64(ALL_ONES);
119	int64x1_t vshiftr = vdup_n_s64(-CHAR_BIT * (8 - nbytes));
120	vmask = vshl_u64(vmask, vshiftr);/* Shift right */
121	vword64 = vand_u64(vword64, vmask);
122	/* Fold 64-bit sum to 33 bits */
123	vword64 = vpaddl_u32(vreinterpret_u32_u64(vword64));
124	/* Add to accumulator */
125	vsum = vpadal_u32(vsum, vreinterpret_u32_u64(vword64));
126    }
127
128    /* Fold 64-bit vsum to 32 bits */
129    vsum = vpaddl_u32(vreinterpret_u32_u64(vsum));
130    vsum = vpaddl_u32(vreinterpret_u32_u64(vsum));
131    Assert(vget_lane_u32(vreinterpret_u32_u64(vsum), 1) == 0);
132
133    /* Fold 32-bit vsum to 16 bits */
134    uint32x2_t vsum32 = vreinterpret_u32_u64(vsum);
135    vsum32 = vpaddl_u16(vreinterpret_u16_u32(vsum32));
136    vsum32 = vpaddl_u16(vreinterpret_u16_u32(vsum32));
137    Assert(vget_lane_u16(vreinterpret_u16_u32(vsum32), 1) == 0);
138    Assert(vget_lane_u16(vreinterpret_u16_u32(vsum32), 2) == 0);
139    Assert(vget_lane_u16(vreinterpret_u16_u32(vsum32), 3) == 0);
140
141    /* Convert to 16-bit scalar */
142    uint16_t sum = vget_lane_u16(vreinterpret_u16_u32(vsum32), 0);
143
144    if (unlikely(swap))/* Odd base pointer is unexpected */
145    {
146	sum = bswap16(sum);
147    }
148    return sum;
149}
150