Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2017 ARM Ltd |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions |
| 7 | * are met: |
| 8 | * 1. Redistributions of source code must retain the above copyright |
| 9 | * notice, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * 3. The name of the company may not be used to endorse or promote |
| 14 | * products derived from this software without specific prior written |
| 15 | * permission. |
| 16 | * |
| 17 | * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| 18 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 19 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 20 | * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED |
| 22 | * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| 23 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
| 24 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
| 25 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| 26 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | */ |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 28 | |
| 29 | /* Assumptions: |
| 30 | * |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 31 | * ARMv8-a, AArch64, unaligned accesses. |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 32 | */ |
| 33 | |
| 34 | #include <private/bionic_asm.h> |
| 35 | |
| 36 | /* Parameters and result. */ |
| 37 | #define src1 x0 |
| 38 | #define src2 x1 |
| 39 | #define limit x2 |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 40 | #define result w0 |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 41 | |
| 42 | /* Internal variables. */ |
| 43 | #define data1 x3 |
| 44 | #define data1w w3 |
| 45 | #define data2 x4 |
| 46 | #define data2w w4 |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 47 | #define tmp1 x5 |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 48 | |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 49 | /* Small inputs of less than 8 bytes are handled separately. This allows the |
| 50 | main code to be sped up using unaligned loads since there are now at least |
| 51 | 8 bytes to be compared. If the first 8 bytes are equal, align src1. |
| 52 | This ensures each iteration does at most one unaligned access even if both |
| 53 | src1 and src2 are unaligned, and mutually aligned inputs behave as if |
| 54 | aligned. After the main loop, process the last 8 bytes using unaligned |
| 55 | accesses. */ |
| 56 | |
| 57 | .p2align 6 |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 58 | ENTRY(memcmp) |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 59 | subs limit, limit, 8 |
| 60 | b.lo .Lless8 |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 61 | |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 62 | /* Limit >= 8, so check first 8 bytes using unaligned loads. */ |
| 63 | ldr data1, [src1], 8 |
| 64 | ldr data2, [src2], 8 |
| 65 | and tmp1, src1, 7 |
| 66 | add limit, limit, tmp1 |
| 67 | cmp data1, data2 |
| 68 | bne .Lreturn |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 69 | |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 70 | /* Align src1 and adjust src2 with bytes not yet done. */ |
| 71 | sub src1, src1, tmp1 |
| 72 | sub src2, src2, tmp1 |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 73 | |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 74 | subs limit, limit, 8 |
| 75 | b.ls .Llast_bytes |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 76 | |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 77 | /* Loop performing 8 bytes per iteration using aligned src1. |
| 78 | Limit is pre-decremented by 8 and must be larger than zero. |
| 79 | Exit if <= 8 bytes left to do or if the data is not equal. */ |
| 80 | .p2align 4 |
| 81 | .Lloop8: |
| 82 | ldr data1, [src1], 8 |
| 83 | ldr data2, [src2], 8 |
| 84 | subs limit, limit, 8 |
| 85 | ccmp data1, data2, 0, hi /* NZCV = 0b0000. */ |
| 86 | b.eq .Lloop8 |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 87 | |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 88 | cmp data1, data2 |
| 89 | bne .Lreturn |
| 90 | |
| 91 | /* Compare last 1-8 bytes using unaligned access. */ |
| 92 | .Llast_bytes: |
| 93 | ldr data1, [src1, limit] |
| 94 | ldr data2, [src2, limit] |
| 95 | |
| 96 | /* Compare data bytes and set return value to 0, -1 or 1. */ |
| 97 | .Lreturn: |
| 98 | #ifndef __AARCH64EB__ |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 99 | rev data1, data1 |
| 100 | rev data2, data2 |
| 101 | #endif |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 102 | cmp data1, data2 |
| 103 | .Lret_eq: |
| 104 | cset result, ne |
| 105 | cneg result, result, lo |
| 106 | ret |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 107 | |
Sebastian Pop | ed9bfc4 | 2017-06-19 12:39:02 -0500 | [diff] [blame] | 108 | .p2align 4 |
| 109 | /* Compare up to 8 bytes. Limit is [-8..-1]. */ |
| 110 | .Lless8: |
| 111 | adds limit, limit, 4 |
| 112 | b.lo .Lless4 |
| 113 | ldr data1w, [src1], 4 |
| 114 | ldr data2w, [src2], 4 |
| 115 | cmp data1w, data2w |
| 116 | b.ne .Lreturn |
| 117 | sub limit, limit, 4 |
| 118 | .Lless4: |
| 119 | adds limit, limit, 4 |
| 120 | beq .Lret_eq |
| 121 | .Lbyte_loop: |
| 122 | ldrb data1w, [src1], 1 |
| 123 | ldrb data2w, [src2], 1 |
| 124 | subs limit, limit, 1 |
| 125 | ccmp data1w, data2w, 0, ne /* NZCV = 0b0000. */ |
| 126 | b.eq .Lbyte_loop |
| 127 | sub result, data1w, data2w |
Bernhard Rosenkraenzer | 7e4fa56 | 2014-03-05 11:40:57 +0100 | [diff] [blame] | 128 | ret |
| 129 | END(memcmp) |