projects / thirdparty / glibc.git / blame
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| c7d3890f FX |
1 | /* Copyright (C) 2018 Free Software Foundation, Inc. |
| 2 | ||
| 3 | This file is part of the GNU C Library. | |
| 4 | ||
| 5 | The GNU C Library is free software; you can redistribute it and/or | |
| 6 | modify it under the terms of the GNU Lesser General Public | |
| 7 | License as published by the Free Software Foundation; either | |
| 8 | version 2.1 of the License, or (at your option) any later version. | |
| 9 | ||
| 10 | The GNU C Library is distributed in the hope that it will be useful, | |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 | Lesser General Public License for more details. | |
| 14 | ||
| 15 | You should have received a copy of the GNU Lesser General Public | |
| 16 | License along with the GNU C Library. If not, see | |
| 17 | <http://www.gnu.org/licenses/>. */ | |
| 18 | ||
| 19 | #include <sysdep.h> | |
| 20 | #include "memset-reg.h" | |
| 21 | ||
| 22 | #ifndef MEMSET | |
| 23 | # define MEMSET __memset_base64 | |
| 24 | #endif | |
| 25 | ||
| 26 | #ifndef DC_ZVA_THRESHOLD | |
| 27 | # define DC_ZVA_THRESHOLD 512 | |
| 28 | #endif | |
| 29 | ||
| 30 | /* Assumptions: | |
| 31 | * | |
| 32 | * ARMv8-a, AArch64, unaligned accesses | |
| 33 | * | |
| 34 | */ | |
| 35 | ||
| 36 | ENTRY_ALIGN (MEMSET, 6) | |
| 37 | ||
| 38 | DELOUSE (0) | |
| 39 | DELOUSE (2) | |
| 40 | ||
| 41 | bfi valw, valw, 8, 8 | |
| 42 | bfi valw, valw, 16, 16 | |
| 43 | bfi val, val, 32, 32 | |
| 44 | ||
| 45 | add dstend, dstin, count | |
| 46 | ||
| 47 | cmp count, 96 | |
| 48 | b.hi L(set_long) | |
| 49 | cmp count, 16 | |
| 50 | b.hs L(set_medium) | |
| 51 | ||
| 52 | /* Set 0..15 bytes. */ | |
| 53 | tbz count, 3, 1f | |
| 54 | str val, [dstin] | |
| 55 | str val, [dstend, -8] | |
| 56 | ret | |
| 57 | ||
| 58 | .p2align 3 | |
| 59 | 1: tbz count, 2, 2f | |
| 60 | str valw, [dstin] | |
| 61 | str valw, [dstend, -4] | |
| 62 | ret | |
| 63 | 2: cbz count, 3f | |
| 64 | strb valw, [dstin] | |
| 65 | tbz count, 1, 3f | |
| 66 | strh valw, [dstend, -2] | |
| 67 | 3: ret | |
| 68 | ||
| 69 | .p2align 3 | |
| 70 | /* Set 16..96 bytes. */ | |
| 71 | L(set_medium): | |
| 72 | stp val, val, [dstin] | |
| 73 | tbnz count, 6, L(set96) | |
| 74 | stp val, val, [dstend, -16] | |
| 75 | tbz count, 5, 1f | |
| 76 | stp val, val, [dstin, 16] | |
| 77 | stp val, val, [dstend, -32] | |
| 78 | 1: ret | |
| 79 | ||
| 80 | .p2align 4 | |
| 81 | /* Set 64..96 bytes. Write 64 bytes from the start and | |
| 82 | 32 bytes from the end. */ | |
| 83 | L(set96): | |
| 84 | stp val, val, [dstin, 16] | |
| 85 | stp val, val, [dstin, 32] | |
| 86 | stp val, val, [dstin, 48] | |
| 87 | stp val, val, [dstend, -32] | |
| 88 | stp val, val, [dstend, -16] | |
| 89 | ret | |
| 90 | ||
| 91 | .p2align 4 | |
| 92 | L(set_long): | |
| 93 | stp val, val, [dstin] | |
| 94 | cmp count, DC_ZVA_THRESHOLD | |
| 95 | ccmp val, 0, 0, cs | |
| 96 | bic dst, dstin, 15 | |
| 97 | b.eq L(zva_64) | |
| 98 | ||
| 99 | /* Small-size or non-zero memset does not use DC ZVA. */ | |
| 100 | sub count, dstend, dst | |
| 101 | ||
| 102 | /* | |
| 103 | * Adjust count and bias for loop. By substracting extra 1 from count, | |
| 104 | * it is easy to use tbz instruction to check whether loop tailing | |
| 105 | * count is less than 33 bytes, so as to bypass 2 unneccesary stps. | |
| 106 | */ | |
| 107 | sub count, count, 64+16+1 | |
| 108 | nop | |
| 109 | ||
| 110 | 1: stp val, val, [dst, 16] | |
| 111 | stp val, val, [dst, 32] | |
| 112 | stp val, val, [dst, 48] | |
| 113 | stp val, val, [dst, 64]! | |
| 114 | subs count, count, 64 | |
| 115 | b.hs 1b | |
| 116 | ||
| 117 | tbz count, 5, 1f /* Remaining count is less than 33 bytes? */ | |
| 118 | stp val, val, [dst, 16] | |
| 119 | stp val, val, [dst, 32] | |
| 120 | 1: stp val, val, [dstend, -32] | |
| 121 | stp val, val, [dstend, -16] | |
| 122 | ret | |
| 123 | ||
| 124 | .p2align 3 | |
| 125 | L(zva_64): | |
| 126 | stp val, val, [dst, 16] | |
| 127 | stp val, val, [dst, 32] | |
| 128 | stp val, val, [dst, 48] | |
| 129 | bic dst, dst, 63 | |
| 130 | ||
| 131 | /* | |
| 132 | * Previous memory writes might cross cache line boundary, and cause | |
| 133 | * cache line partially dirty. Zeroing this kind of cache line using | |
| 134 | * DC ZVA will incur extra cost, for it requires loading untouched | |
| 135 | * part of the line from memory before zeoring. | |
| 136 | * | |
| 137 | * So, write the first 64 byte aligned block using stp to force | |
| 138 | * fully dirty cache line. | |
| 139 | */ | |
| 140 | stp val, val, [dst, 64] | |
| 141 | stp val, val, [dst, 80] | |
| 142 | stp val, val, [dst, 96] | |
| 143 | stp val, val, [dst, 112] | |
| 144 | ||
| 145 | sub count, dstend, dst | |
| 146 | /* | |
| 147 | * Adjust count and bias for loop. By substracting extra 1 from count, | |
| 148 | * it is easy to use tbz instruction to check whether loop tailing | |
| 149 | * count is less than 33 bytes, so as to bypass 2 unneccesary stps. | |
| 150 | */ | |
| 151 | sub count, count, 128+64+64+1 | |
| 152 | add dst, dst, 128 | |
| 153 | nop | |
| 154 | ||
| 155 | /* DC ZVA sets 64 bytes each time. */ | |
| 156 | 1: dc zva, dst | |
| 157 | add dst, dst, 64 | |
| 158 | subs count, count, 64 | |
| 159 | b.hs 1b | |
| 160 | ||
| 161 | /* | |
| 162 | * Write the last 64 byte aligned block using stp to force fully | |
| 163 | * dirty cache line. | |
| 164 | */ | |
| 165 | stp val, val, [dst, 0] | |
| 166 | stp val, val, [dst, 16] | |
| 167 | stp val, val, [dst, 32] | |
| 168 | stp val, val, [dst, 48] | |
| 169 | ||
| 170 | tbz count, 5, 1f /* Remaining count is less than 33 bytes? */ | |
| 171 | stp val, val, [dst, 64] | |
| 172 | stp val, val, [dst, 80] | |
| 173 | 1: stp val, val, [dstend, -32] | |
| 174 | stp val, val, [dstend, -16] | |
| 175 | ret | |
| 176 | ||
| 177 | END (MEMSET) | |
| 178 | libc_hidden_builtin_def (MEMSET) |