1/* Optimized version of the standard strchr() function.
2 This file is part of the GNU C Library.
3 Copyright (C) 2000-2022 Free Software Foundation, Inc.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19/* Return: the address of the first occurence of chr in str or NULL
20
21 Inputs:
22 in0: str
23 in1: chr
24
25 A modified version of memchr.S, the search ends when the character is
26 found or the terminating null character is encountered.
27
28 This implementation assumes little endian mode. For big endian mode,
29 the instruction czx1.r should be replaced by czx1.l. */
30
31#include <sysdep.h>
32#undef ret
33
34#define saved_lc r18
35#define poschr r19
36#define pos0 r20
37#define val1 r21
38#define val2 r22
39#define tmp r24
40#define chrx8 r25
41#define loopcnt r30
42
43#define str in0
44#define chr in1
45
46ENTRY(strchr)
47 .prologue
48 alloc r2 = ar.pfs, 2, 0, 0, 0
49 .save ar.lc, saved_lc
50 mov saved_lc = ar.lc // save the loop counter
51 .body
52 mov ret0 = str
53 and tmp = 7, str // tmp = str % 8
54 mux1 chrx8 = chr, @brcst
55 extr.u chr = chr, 0, 8 // retain only the last byte
56 cmp.ne p8, p0 = r0, r0 // clear p8
57 ;;
58 sub loopcnt = 8, tmp // loopcnt = 8 - tmp
59 cmp.eq p6, p0 = tmp, r0
60(p6) br.cond.sptk .str_aligned;;
61 adds loopcnt = -1, loopcnt;;
62 mov ar.lc = loopcnt
63.l1:
64 ld1 val2 = [ret0], 1
65 ;;
66 cmp.eq p6, p0 = val2, chr
67 cmp.eq p7, p0 = val2, r0
68(p6) br.cond.spnt .restore_and_exit
69(p7) br.cond.spnt .notfound
70 br.cloop.sptk .l1
71.str_aligned:
72 ld8 val1 = [ret0], 8;;
73 nop.b 0
74 nop.b 0
75.l2:
76 ld8.s val2 = [ret0], 8 // don't bomb out here
77 czx1.r pos0 = val1
78 xor tmp = val1, chrx8 // if val1 contains chr, tmp will
79 ;; // contain a zero in its position
80 czx1.r poschr = tmp
81 cmp.ne p6, p0 = 8, pos0
82 ;;
83 cmp.ne p7, p0 = 8, poschr
84(p7) br.cond.spnt .foundit
85(p6) br.cond.spnt .notfound
86 chk.s val2, .recovery
87.back:
88 mov val1 = val2
89 br.cond.dptk .l2
90.foundit:
91(p6) cmp.lt p8, p0 = pos0, poschr // we found chr and null in the word
92(p8) br.cond.spnt .notfound // null was found before chr
93 add ret0 = ret0, poschr ;;
94 adds ret0 = -15, ret0 ;; // should be -16, but we decrement
95.restore_and_exit: // ret0 in the next instruction
96 adds ret0 = -1, ret0 // ret0 was pointing 1 char too far
97 mov ar.lc = saved_lc // restore the loop counter
98 br.ret.sptk.many b0
99.notfound:
100 mov ret0 = r0 // return NULL if null was found
101 mov ar.lc = saved_lc
102 br.ret.sptk.many b0
103.recovery:
104 adds ret0 = -8, ret0;;
105 ld8 val2 = [ret0], 8 // bomb out here
106 br.cond.sptk .back
107END(strchr)
108
109weak_alias (strchr, index)
110libc_hidden_builtin_def (strchr)
111

source code of glibc/sysdeps/ia64/strchr.S