1 /* SPDX-License-Identifier: GPL-2.0-only */ !! 1 /* Copyright (C) 1996 Free Software Foundation, Inc.
2 /* !! 2 This file is part of the GNU C Library.
3 * linux/arch/arm/lib/memchr.S !! 3 Contributed by David Mosberger (davidm@cs.arizona.edu).
4 * !! 4
5 * Copyright (C) 1995-2000 Russell King !! 5 The GNU C Library is free software; you can redistribute it and/or
6 * !! 6 modify it under the terms of the GNU Library General Public License as
7 * ASM optimised string functions !! 7 published by the Free Software Foundation; either version 2 of the
8 */ !! 8 License, or (at your option) any later version.
9 #include <linux/linkage.h> !! 9
10 #include <asm/assembler.h> !! 10 The GNU C Library is distributed in the hope that it will be useful,
11 !! 11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 .text !! 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 .align 5 !! 13 Library General Public License for more details.
14 ENTRY(memchr) !! 14
15 1: subs r2, r2, #1 !! 15 You should have received a copy of the GNU Library General Public
16 bmi 2f !! 16 License along with the GNU C Library; see the file COPYING.LIB. If not,
17 ldrb r3, [r0], #1 !! 17 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 teq r3, r1 !! 18 Boston, MA 02111-1307, USA. */
19 bne 1b !! 19
20 sub r0, r0, #1 !! 20 /* Finds characters in a memory area. Optimized for the Alpha:
21 2: movne r0, #0 !! 21
22 ret lr !! 22 - memory accessed as aligned quadwords only
23 ENDPROC(memchr) !! 23 - uses cmpbge to compare 8 bytes in parallel
>> 24 - does binary search to find 0 byte in last
>> 25 quadword (HAKMEM needed 12 instructions to
>> 26 do this instead of the 9 instructions that
>> 27 binary search needs).
>> 28
>> 29 For correctness consider that:
>> 30
>> 31 - only minimum number of quadwords may be accessed
>> 32 - the third argument is an unsigned long
>> 33 */
>> 34 #include <linux/export.h>
>> 35 .set noreorder
>> 36 .set noat
>> 37
>> 38 .globl memchr
>> 39 .ent memchr
>> 40 memchr:
>> 41 .frame $30,0,$26,0
>> 42 .prologue 0
>> 43
>> 44 # Hack -- if someone passes in (size_t)-1, hoping to just
>> 45 # search til the end of the address space, we will overflow
>> 46 # below when we find the address of the last byte. Given
>> 47 # that we will never have a 56-bit address space, cropping
>> 48 # the length is the easiest way to avoid trouble.
>> 49 zap $18, 0x80, $5 #-e0 :
>> 50
>> 51 beq $18, $not_found # .. e1 :
>> 52 ldq_u $1, 0($16) # e1 : load first quadword
>> 53 insbl $17, 1, $2 # .. e0 : $2 = 000000000000ch00
>> 54 and $17, 0xff, $17 #-e0 : $17 = 00000000000000ch
>> 55 cmpult $18, 9, $4 # .. e1 :
>> 56 or $2, $17, $17 # e0 : $17 = 000000000000chch
>> 57 lda $3, -1($31) # .. e1 :
>> 58 sll $17, 16, $2 #-e0 : $2 = 00000000chch0000
>> 59 addq $16, $5, $5 # .. e1 :
>> 60 or $2, $17, $17 # e1 : $17 = 00000000chchchch
>> 61 unop # :
>> 62 sll $17, 32, $2 #-e0 : $2 = chchchch00000000
>> 63 or $2, $17, $17 # e1 : $17 = chchchchchchchch
>> 64 extql $1, $16, $7 # e0 :
>> 65 beq $4, $first_quad # .. e1 :
>> 66
>> 67 ldq_u $6, -1($5) #-e1 : eight or less bytes to search
>> 68 extqh $6, $16, $6 # .. e0 :
>> 69 mov $16, $0 # e0 :
>> 70 or $7, $6, $1 # .. e1 : $1 = quadword starting at $16
>> 71
>> 72 # Deal with the case where at most 8 bytes remain to be searched
>> 73 # in $1. E.g.:
>> 74 # $18 = 6
>> 75 # $1 = ????c6c5c4c3c2c1
>> 76 $last_quad:
>> 77 negq $18, $6 #-e0 :
>> 78 xor $17, $1, $1 # .. e1 :
>> 79 srl $3, $6, $6 # e0 : $6 = mask of $18 bits set
>> 80 cmpbge $31, $1, $2 # .. e1 :
>> 81 and $2, $6, $2 #-e0 :
>> 82 beq $2, $not_found # .. e1 :
>> 83
>> 84 $found_it:
>> 85 # Now, determine which byte matched:
>> 86 negq $2, $3 # e0 :
>> 87 and $2, $3, $2 # e1 :
>> 88
>> 89 and $2, 0x0f, $1 #-e0 :
>> 90 addq $0, 4, $3 # .. e1 :
>> 91 cmoveq $1, $3, $0 # e0 :
>> 92
>> 93 addq $0, 2, $3 # .. e1 :
>> 94 and $2, 0x33, $1 #-e0 :
>> 95 cmoveq $1, $3, $0 # .. e1 :
>> 96
>> 97 and $2, 0x55, $1 # e0 :
>> 98 addq $0, 1, $3 # .. e1 :
>> 99 cmoveq $1, $3, $0 #-e0 :
>> 100
>> 101 $done: ret # .. e1 :
>> 102
>> 103 # Deal with the case where $18 > 8 bytes remain to be
>> 104 # searched. $16 may not be aligned.
>> 105 .align 4
>> 106 $first_quad:
>> 107 andnot $16, 0x7, $0 #-e1 :
>> 108 insqh $3, $16, $2 # .. e0 : $2 = 0000ffffffffffff ($16<0:2> ff)
>> 109 xor $1, $17, $1 # e0 :
>> 110 or $1, $2, $1 # e1 : $1 = ====ffffffffffff
>> 111 cmpbge $31, $1, $2 #-e0 :
>> 112 bne $2, $found_it # .. e1 :
>> 113
>> 114 # At least one byte left to process.
>> 115
>> 116 ldq $1, 8($0) # e0 :
>> 117 subq $5, 1, $18 # .. e1 :
>> 118 addq $0, 8, $0 #-e0 :
>> 119
>> 120 # Make $18 point to last quad to be accessed (the
>> 121 # last quad may or may not be partial).
>> 122
>> 123 andnot $18, 0x7, $18 # .. e1 :
>> 124 cmpult $0, $18, $2 # e0 :
>> 125 beq $2, $final # .. e1 :
>> 126
>> 127 # At least two quads remain to be accessed.
>> 128
>> 129 subq $18, $0, $4 #-e0 : $4 <- nr quads to be processed
>> 130 and $4, 8, $4 # e1 : odd number of quads?
>> 131 bne $4, $odd_quad_count # e1 :
>> 132
>> 133 # At least three quads remain to be accessed
>> 134
>> 135 mov $1, $4 # e0 : move prefetched value to correct reg
>> 136
>> 137 .align 4
>> 138 $unrolled_loop:
>> 139 ldq $1, 8($0) #-e0 : prefetch $1
>> 140 xor $17, $4, $2 # .. e1 :
>> 141 cmpbge $31, $2, $2 # e0 :
>> 142 bne $2, $found_it # .. e1 :
>> 143
>> 144 addq $0, 8, $0 #-e0 :
>> 145 $odd_quad_count:
>> 146 xor $17, $1, $2 # .. e1 :
>> 147 ldq $4, 8($0) # e0 : prefetch $4
>> 148 cmpbge $31, $2, $2 # .. e1 :
>> 149 addq $0, 8, $6 #-e0 :
>> 150 bne $2, $found_it # .. e1 :
>> 151
>> 152 cmpult $6, $18, $6 # e0 :
>> 153 addq $0, 8, $0 # .. e1 :
>> 154 bne $6, $unrolled_loop #-e1 :
>> 155
>> 156 mov $4, $1 # e0 : move prefetched value into $1
>> 157 $final: subq $5, $0, $18 # .. e1 : $18 <- number of bytes left to do
>> 158 bne $18, $last_quad # e1 :
>> 159
>> 160 $not_found:
>> 161 mov $31, $0 #-e0 :
>> 162 ret # .. e1 :
>> 163
>> 164 .end memchr
>> 165 EXPORT_SYMBOL(memchr)
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