projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| f940b965 RE |
1 | /* strchr - find a character in a string |
| 2 | ||
| f7a9f785 | 3 | Copyright (C) 2014-2016 Free Software Foundation, Inc. |
| f940b965 RE |
4 | |
| 5 | This file is part of the GNU C Library. | |
| 6 | ||
| 7 | The GNU C Library is free software; you can redistribute it and/or | |
| 8 | modify it under the terms of the GNU Lesser General Public | |
| 9 | License as published by the Free Software Foundation; either | |
| 10 | version 2.1 of the License, or (at your option) any later version. | |
| 11 | ||
| 12 | The GNU C Library is distributed in the hope that it will be useful, | |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 15 | Lesser General Public License for more details. | |
| 16 | ||
| 17 | You should have received a copy of the GNU Lesser General Public | |
| 18 | License along with the GNU C Library. If not, see | |
| 19 | <http://www.gnu.org/licenses/>. */ | |
| 20 | ||
| 21 | #include <sysdep.h> | |
| 22 | ||
| 23 | /* Assumptions: | |
| 24 | * | |
| 25 | * ARMv8-a, AArch64 | |
| 26 | */ | |
| 27 | ||
| 28 | /* Arguments and results. */ | |
| 29 | #define srcin x0 | |
| 30 | #define chrin w1 | |
| 31 | ||
| 32 | #define result x0 | |
| 33 | ||
| 34 | #define src x2 | |
| 35 | #define tmp1 x3 | |
| 36 | #define wtmp2 w4 | |
| 37 | #define tmp3 x5 | |
| 38 | ||
| 39 | #define vrepchr v0 | |
| 40 | #define vdata1 v1 | |
| 41 | #define vdata2 v2 | |
| 42 | #define vhas_nul1 v3 | |
| 43 | #define vhas_nul2 v4 | |
| 44 | #define vhas_chr1 v5 | |
| 45 | #define vhas_chr2 v6 | |
| 46 | #define vrepmask_0 v7 | |
| 47 | #define vrepmask_c v16 | |
| 48 | #define vend1 v17 | |
| 49 | #define vend2 v18 | |
| 50 | ||
| 51 | /* Core algorithm. | |
| 52 | For each 32-byte hunk we calculate a 64-bit syndrome value, with | |
| 53 | two bits per byte (LSB is always in bits 0 and 1, for both big | |
| 54 | and little-endian systems). Bit 0 is set iff the relevant byte | |
| 55 | matched the requested character. Bit 1 is set iff the | |
| 56 | relevant byte matched the NUL end of string (we trigger off bit0 | |
| 57 | for the special case of looking for NUL). Since the bits | |
| 58 | in the syndrome reflect exactly the order in which things occur | |
| 59 | in the original string a count_trailing_zeros() operation will | |
| 60 | identify exactly which byte is causing the termination, and why. */ | |
| 61 | ||
| 62 | /* Locals and temporaries. */ | |
| 63 | ||
| 64 | ENTRY (strchr) | |
| 65 | mov wtmp2, #0x0401 | |
| 66 | movk wtmp2, #0x4010, lsl #16 | |
| 67 | dup vrepchr.16b, chrin | |
| 68 | bic src, srcin, #31 | |
| 69 | dup vrepmask_c.4s, wtmp2 | |
| 70 | ands tmp1, srcin, #31 | |
| 71 | add vrepmask_0.4s, vrepmask_c.4s, vrepmask_c.4s // lsl #1 | |
| 72 | b.eq L(loop) | |
| 73 | ||
| 74 | /* Input string is not 32-byte aligned. Rather than forcing | |
| 75 | the padding bytes to a safe value, we calculate the syndrome | |
| 76 | for all the bytes, but then mask off those bits of the | |
| 77 | syndrome that are related to the padding. */ | |
| 78 | ld1 {vdata1.16b, vdata2.16b}, [src], #32 | |
| 79 | neg tmp1, tmp1 | |
| 80 | cmeq vhas_nul1.16b, vdata1.16b, #0 | |
| 81 | cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b | |
| 82 | cmeq vhas_nul2.16b, vdata2.16b, #0 | |
| 83 | cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b | |
| 84 | and vhas_nul1.16b, vhas_nul1.16b, vrepmask_0.16b | |
| 85 | and vhas_nul2.16b, vhas_nul2.16b, vrepmask_0.16b | |
| 86 | and vhas_chr1.16b, vhas_chr1.16b, vrepmask_c.16b | |
| 87 | and vhas_chr2.16b, vhas_chr2.16b, vrepmask_c.16b | |
| 88 | orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b | |
| 89 | orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b | |
| 90 | lsl tmp1, tmp1, #1 | |
| 91 | addp vend1.16b, vend1.16b, vend2.16b // 256->128 | |
| 92 | mov tmp3, #~0 | |
| 93 | addp vend1.16b, vend1.16b, vend2.16b // 128->64 | |
| 94 | lsr tmp1, tmp3, tmp1 | |
| 95 | ||
| 96 | mov tmp3, vend1.2d[0] | |
| 97 | bic tmp1, tmp3, tmp1 // Mask padding bits. | |
| 98 | cbnz tmp1, L(tail) | |
| 99 | ||
| 100 | L(loop): | |
| 101 | ld1 {vdata1.16b, vdata2.16b}, [src], #32 | |
| 102 | cmeq vhas_nul1.16b, vdata1.16b, #0 | |
| 103 | cmeq vhas_chr1.16b, vdata1.16b, vrepchr.16b | |
| 104 | cmeq vhas_nul2.16b, vdata2.16b, #0 | |
| 105 | cmeq vhas_chr2.16b, vdata2.16b, vrepchr.16b | |
| 106 | /* Use a fast check for the termination condition. */ | |
| 107 | orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b | |
| 108 | orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b | |
| 109 | orr vend1.16b, vend1.16b, vend2.16b | |
| 110 | addp vend1.2d, vend1.2d, vend1.2d | |
| 111 | mov tmp1, vend1.2d[0] | |
| 112 | cbz tmp1, L(loop) | |
| 113 | ||
| 114 | /* Termination condition found. Now need to establish exactly why | |
| 115 | we terminated. */ | |
| 116 | and vhas_nul1.16b, vhas_nul1.16b, vrepmask_0.16b | |
| 117 | and vhas_nul2.16b, vhas_nul2.16b, vrepmask_0.16b | |
| 118 | and vhas_chr1.16b, vhas_chr1.16b, vrepmask_c.16b | |
| 119 | and vhas_chr2.16b, vhas_chr2.16b, vrepmask_c.16b | |
| 120 | orr vend1.16b, vhas_nul1.16b, vhas_chr1.16b | |
| 121 | orr vend2.16b, vhas_nul2.16b, vhas_chr2.16b | |
| 122 | addp vend1.16b, vend1.16b, vend2.16b // 256->128 | |
| 123 | addp vend1.16b, vend1.16b, vend2.16b // 128->64 | |
| 124 | ||
| 125 | mov tmp1, vend1.2d[0] | |
| 126 | L(tail): | |
| 127 | sub src, src, #32 | |
| 128 | rbit tmp1, tmp1 | |
| 129 | clz tmp1, tmp1 | |
| 130 | /* Tmp1 is even if the target charager was found first. Otherwise | |
| 131 | we've found the end of string and we weren't looking for NUL. */ | |
| 132 | tst tmp1, #1 | |
| 133 | add result, src, tmp1, lsr #1 | |
| 134 | csel result, result, xzr, eq | |
| 135 | ret | |
| 136 | END (strchr) | |
| 137 | libc_hidden_builtin_def (strchr) | |
| 138 | weak_alias (strchr, index) |