1 /*
2 * Armv7-A specific checksum implementation using NEON
3 *
4 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 * See https://llvm.org/LICENSE.txt for license information.
6 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 */
8
9 #include "networking.h"
10 #include "../chksum_common.h"
11
12 #ifndef __ARM_NEON
13 #pragma GCC target("+simd")
14 #endif
15
16 #include <arm_neon.h>
17
18 unsigned short
__chksum_arm_simd(const void * ptr,unsigned int nbytes)19 __chksum_arm_simd(const void *ptr, unsigned int nbytes)
20 {
21 bool swap = (uintptr_t) ptr & 1;
22 uint64x1_t vsum = { 0 };
23
24 if (unlikely(nbytes < 40))
25 {
26 uint64_t sum = slurp_small(ptr, nbytes);
27 return fold_and_swap(sum, false);
28 }
29
30 /* 8-byte align pointer */
31 /* Inline slurp_head-like code since we use NEON here */
32 Assert(nbytes >= 8);
33 uint32_t off = (uintptr_t) ptr & 7;
34 if (likely(off != 0))
35 {
36 const uint64_t *may_alias ptr64 = align_ptr(ptr, 8);
37 uint64x1_t vword64 = vld1_u64(ptr64);
38 /* Get rid of bytes 0..off-1 */
39 uint64x1_t vmask = vdup_n_u64(ALL_ONES);
40 int64x1_t vshiftl = vdup_n_s64(CHAR_BIT * off);
41 vmask = vshl_u64(vmask, vshiftl);
42 vword64 = vand_u64(vword64, vmask);
43 uint32x2_t vtmp = vreinterpret_u32_u64(vword64);
44 /* Set accumulator */
45 vsum = vpaddl_u32(vtmp);
46 /* Update pointer and remaining size */
47 ptr = (char *) ptr64 + 8;
48 nbytes -= 8 - off;
49 }
50 Assert(((uintptr_t) ptr & 7) == 0);
51
52 /* Sum groups of 64 bytes */
53 uint64x2_t vsum0 = { 0, 0 };
54 uint64x2_t vsum1 = { 0, 0 };
55 uint64x2_t vsum2 = { 0, 0 };
56 uint64x2_t vsum3 = { 0, 0 };
57 const uint32_t *may_alias ptr32 = ptr;
58 for (uint32_t i = 0; i < nbytes / 64; i++)
59 {
60 uint32x4_t vtmp0 = vld1q_u32(ptr32);
61 uint32x4_t vtmp1 = vld1q_u32(ptr32 + 4);
62 uint32x4_t vtmp2 = vld1q_u32(ptr32 + 8);
63 uint32x4_t vtmp3 = vld1q_u32(ptr32 + 12);
64 vsum0 = vpadalq_u32(vsum0, vtmp0);
65 vsum1 = vpadalq_u32(vsum1, vtmp1);
66 vsum2 = vpadalq_u32(vsum2, vtmp2);
67 vsum3 = vpadalq_u32(vsum3, vtmp3);
68 ptr32 += 16;
69 }
70 nbytes %= 64;
71
72 /* Fold vsum1/vsum2/vsum3 into vsum0 */
73 vsum0 = vpadalq_u32(vsum0, vreinterpretq_u32_u64(vsum2));
74 vsum1 = vpadalq_u32(vsum1, vreinterpretq_u32_u64(vsum3));
75 vsum0 = vpadalq_u32(vsum0, vreinterpretq_u32_u64(vsum1));
76
77 /* Add any trailing 16-byte groups */
78 while (likely(nbytes >= 16))
79 {
80 uint32x4_t vtmp0 = vld1q_u32(ptr32);
81 vsum0 = vpadalq_u32(vsum0, vtmp0);
82 ptr32 += 4;
83 nbytes -= 16;
84 }
85 Assert(nbytes < 16);
86
87 /* Fold vsum0 into vsum */
88 {
89 /* 4xu32 (4x32b) -> 2xu64 (2x33b) */
90 vsum0 = vpaddlq_u32(vreinterpretq_u32_u64(vsum0));
91 /* 4xu32 (2x(1b+32b)) -> 2xu64 (2x(0b+32b)) */
92 vsum0 = vpaddlq_u32(vreinterpretq_u32_u64(vsum0));
93 /* 4xu32 (4x32b) -> 2xu64 (2x33b) */
94 Assert((vgetq_lane_u64(vsum0, 0) >> 32) == 0);
95 Assert((vgetq_lane_u64(vsum0, 1) >> 32) == 0);
96 uint32x2_t vtmp = vmovn_u64(vsum0);
97 /* Add to accumulator */
98 vsum = vpadal_u32(vsum, vtmp);
99 }
100
101 /* Add any trailing group of 8 bytes */
102 if (nbytes & 8)
103 {
104 uint32x2_t vtmp = vld1_u32(ptr32);
105 /* Add to accumulator */
106 vsum = vpadal_u32(vsum, vtmp);
107 ptr32 += 2;
108 nbytes -= 8;
109 }
110 Assert(nbytes < 8);
111
112 /* Handle any trailing 1..7 bytes */
113 if (likely(nbytes != 0))
114 {
115 Assert(((uintptr_t) ptr32 & 7) == 0);
116 Assert(nbytes < 8);
117 uint64x1_t vword64 = vld1_u64((const uint64_t *) ptr32);
118 /* Get rid of bytes 7..nbytes */
119 uint64x1_t vmask = vdup_n_u64(ALL_ONES);
120 int64x1_t vshiftr = vdup_n_s64(-CHAR_BIT * (8 - nbytes));
121 vmask = vshl_u64(vmask, vshiftr);/* Shift right */
122 vword64 = vand_u64(vword64, vmask);
123 /* Fold 64-bit sum to 33 bits */
124 vword64 = vpaddl_u32(vreinterpret_u32_u64(vword64));
125 /* Add to accumulator */
126 vsum = vpadal_u32(vsum, vreinterpret_u32_u64(vword64));
127 }
128
129 /* Fold 64-bit vsum to 32 bits */
130 vsum = vpaddl_u32(vreinterpret_u32_u64(vsum));
131 vsum = vpaddl_u32(vreinterpret_u32_u64(vsum));
132 Assert(vget_lane_u32(vreinterpret_u32_u64(vsum), 1) == 0);
133
134 /* Fold 32-bit vsum to 16 bits */
135 uint32x2_t vsum32 = vreinterpret_u32_u64(vsum);
136 vsum32 = vpaddl_u16(vreinterpret_u16_u32(vsum32));
137 vsum32 = vpaddl_u16(vreinterpret_u16_u32(vsum32));
138 Assert(vget_lane_u16(vreinterpret_u16_u32(vsum32), 1) == 0);
139 Assert(vget_lane_u16(vreinterpret_u16_u32(vsum32), 2) == 0);
140 Assert(vget_lane_u16(vreinterpret_u16_u32(vsum32), 3) == 0);
141
142 /* Convert to 16-bit scalar */
143 uint16_t sum = vget_lane_u16(vreinterpret_u16_u32(vsum32), 0);
144
145 if (unlikely(swap))/* Odd base pointer is unexpected */
146 {
147 sum = bswap16(sum);
148 }
149 return sum;
150 }
151