| /* memcmp - compare memory |
| |
| Copyright (C) 2013-2018 Free Software Foundation, Inc. |
| |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <sysdep.h> |
| |
| /* Assumptions: |
| * |
| * ARMv8-a, AArch64, unaligned accesses. |
| */ |
| |
| /* Parameters and result. */ |
| #define src1 x0 |
| #define src2 x1 |
| #define limit x2 |
| #define result w0 |
| |
| /* Internal variables. */ |
| #define data1 x3 |
| #define data1w w3 |
| #define data2 x4 |
| #define data2w w4 |
| #define tmp1 x5 |
| |
| ENTRY_ALIGN (memcmp, 6) |
| DELOUSE (0) |
| DELOUSE (1) |
| DELOUSE (2) |
| |
| subs limit, limit, 8 |
| b.lo .Lless8 |
| |
| /* Limit >= 8, so check first 8 bytes using unaligned loads. */ |
| ldr data1, [src1], 8 |
| ldr data2, [src2], 8 |
| and tmp1, src1, 7 |
| add limit, limit, tmp1 |
| cmp data1, data2 |
| bne .Lreturn |
| |
| /* Align src1 and adjust src2 with bytes not yet done. */ |
| sub src1, src1, tmp1 |
| sub src2, src2, tmp1 |
| |
| subs limit, limit, 8 |
| b.ls .Llast_bytes |
| |
| /* Loop performing 8 bytes per iteration using aligned src1. |
| Limit is pre-decremented by 8 and must be larger than zero. |
| Exit if <= 8 bytes left to do or if the data is not equal. */ |
| .p2align 4 |
| .Lloop8: |
| ldr data1, [src1], 8 |
| ldr data2, [src2], 8 |
| subs limit, limit, 8 |
| ccmp data1, data2, 0, hi /* NZCV = 0b0000. */ |
| b.eq .Lloop8 |
| |
| cmp data1, data2 |
| bne .Lreturn |
| |
| /* Compare last 1-8 bytes using unaligned access. */ |
| .Llast_bytes: |
| ldr data1, [src1, limit] |
| ldr data2, [src2, limit] |
| |
| /* Compare data bytes and set return value to 0, -1 or 1. */ |
| .Lreturn: |
| #ifndef __AARCH64EB__ |
| rev data1, data1 |
| rev data2, data2 |
| #endif |
| cmp data1, data2 |
| .Lret_eq: |
| cset result, ne |
| cneg result, result, lo |
| ret |
| |
| .p2align 4 |
| /* Compare up to 8 bytes. Limit is [-8..-1]. */ |
| .Lless8: |
| adds limit, limit, 4 |
| b.lo .Lless4 |
| ldr data1w, [src1], 4 |
| ldr data2w, [src2], 4 |
| cmp data1w, data2w |
| b.ne .Lreturn |
| sub limit, limit, 4 |
| .Lless4: |
| adds limit, limit, 4 |
| beq .Lret_eq |
| .Lbyte_loop: |
| ldrb data1w, [src1], 1 |
| ldrb data2w, [src2], 1 |
| subs limit, limit, 1 |
| ccmp data1w, data2w, 0, ne /* NZCV = 0b0000. */ |
| b.eq .Lbyte_loop |
| sub result, data1w, data2w |
| ret |
| |
| END (memcmp) |
| #undef bcmp |
| weak_alias (memcmp, bcmp) |
| libc_hidden_builtin_def (memcmp) |
