1/* memcmp - compare memory 2 * 3 * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 * See https://llvm.org/LICENSE.txt for license information. 5 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 */ 7 8/* Assumptions: 9 * 10 * ARMv8-a, AArch64, unaligned accesses. 11 */ 12 13#include "../asmdefs.h" 14 15/* Parameters and result. */ 16#define src1 x0 17#define src2 x1 18#define limit x2 19#define result w0 20 21/* Internal variables. */ 22#define data1 x3 23#define data1w w3 24#define data1h x4 25#define data2 x5 26#define data2w w5 27#define data2h x6 28#define tmp1 x7 29#define tmp2 x8 30 31ENTRY (__memcmp_aarch64) 32 subs limit, limit, 8 33 b.lo L(less8) 34 35 ldr data1, [src1], 8 36 ldr data2, [src2], 8 37 cmp data1, data2 38 b.ne L(return) 39 40 subs limit, limit, 8 41 b.gt L(more16) 42 43 ldr data1, [src1, limit] 44 ldr data2, [src2, limit] 45 b L(return) 46 47L(more16): 48 ldr data1, [src1], 8 49 ldr data2, [src2], 8 50 cmp data1, data2 51 bne L(return) 52 53 /* Jump directly to comparing the last 16 bytes for 32 byte (or less) 54 strings. */ 55 subs limit, limit, 16 56 b.ls L(last_bytes) 57 58 /* We overlap loads between 0-32 bytes at either side of SRC1 when we 59 try to align, so limit it only to strings larger than 128 bytes. */ 60 cmp limit, 96 61 b.ls L(loop16) 62 63 /* Align src1 and adjust src2 with bytes not yet done. */ 64 and tmp1, src1, 15 65 add limit, limit, tmp1 66 sub src1, src1, tmp1 67 sub src2, src2, tmp1 68 69 /* Loop performing 16 bytes per iteration using aligned src1. 70 Limit is pre-decremented by 16 and must be larger than zero. 71 Exit if <= 16 bytes left to do or if the data is not equal. */ 72 .p2align 4 73L(loop16): 74 ldp data1, data1h, [src1], 16 75 ldp data2, data2h, [src2], 16 76 subs limit, limit, 16 77 ccmp data1, data2, 0, hi 78 ccmp data1h, data2h, 0, eq 79 b.eq L(loop16) 80 81 cmp data1, data2 82 bne L(return) 83 mov data1, data1h 84 mov data2, data2h 85 cmp data1, data2 86 bne L(return) 87 88 /* Compare last 1-16 bytes using unaligned access. */ 89L(last_bytes): 90 add src1, src1, limit 91 add src2, src2, limit 92 ldp data1, data1h, [src1] 93 ldp data2, data2h, [src2] 94 cmp data1, data2 95 bne L(return) 96 mov data1, data1h 97 mov data2, data2h 98 cmp data1, data2 99 100 /* Compare data bytes and set return value to 0, -1 or 1. */ 101L(return): 102#ifndef __AARCH64EB__ 103 rev data1, data1 104 rev data2, data2 105#endif 106 cmp data1, data2 107L(ret_eq): 108 cset result, ne 109 cneg result, result, lo 110 ret 111 112 .p2align 4 113 /* Compare up to 8 bytes. Limit is [-8..-1]. */ 114L(less8): 115 adds limit, limit, 4 116 b.lo L(less4) 117 ldr data1w, [src1], 4 118 ldr data2w, [src2], 4 119 cmp data1w, data2w 120 b.ne L(return) 121 sub limit, limit, 4 122L(less4): 123 adds limit, limit, 4 124 beq L(ret_eq) 125L(byte_loop): 126 ldrb data1w, [src1], 1 127 ldrb data2w, [src2], 1 128 subs limit, limit, 1 129 ccmp data1w, data2w, 0, ne /* NZCV = 0b0000. */ 130 b.eq L(byte_loop) 131 sub result, data1w, data2w 132 ret 133 134END (__memcmp_aarch64) 135