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55dec6d8 AS |
1 | /* strchrnul (str, ch) -- Return pointer to first occurrence of CH in STR |
2 | or the final NUL byte. | |
3 | For Motorola 68000. | |
dff8da6b | 4 | Copyright (C) 1999-2024 Free Software Foundation, Inc. |
55dec6d8 | 5 | This file is part of the GNU C Library. |
55dec6d8 AS |
6 | |
7 | The GNU C Library is free software; you can redistribute it and/or | |
3214b89b AJ |
8 | modify it under the terms of the GNU Lesser General Public |
9 | License as published by the Free Software Foundation; either | |
10 | version 2.1 of the License, or (at your option) any later version. | |
55dec6d8 AS |
11 | |
12 | The GNU C Library is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
3214b89b | 15 | Lesser General Public License for more details. |
55dec6d8 | 16 | |
3214b89b | 17 | You should have received a copy of the GNU Lesser General Public |
ab84e3ff | 18 | License along with the GNU C Library. If not, see |
5a82c748 | 19 | <https://www.gnu.org/licenses/>. */ |
55dec6d8 AS |
20 | |
21 | #include <sysdep.h> | |
22 | #include "asm-syntax.h" | |
23 | ||
24 | TEXT | |
25 | ENTRY(__strchrnul) | |
26 | /* Save the callee-saved registers we use. */ | |
27 | movel R(d2),MEM_PREDEC(sp) | |
50e73d13 | 28 | cfi_adjust_cfa_offset (4) |
55dec6d8 | 29 | movel R(d3),MEM_PREDEC(sp) |
50e73d13 AS |
30 | cfi_adjust_cfa_offset (4) |
31 | cfi_rel_offset (R(d2), 4) | |
32 | cfi_rel_offset (R(d3), 0) | |
55dec6d8 AS |
33 | |
34 | /* Get string pointer and character. */ | |
35 | movel MEM_DISP(sp,12),R(a0) | |
36 | moveb MEM_DISP(sp,19),R(d0) | |
37 | ||
38 | /* Distribute the character to all bytes of a longword. */ | |
39 | movel R(d0),R(d1) | |
40 | lsll #8,R(d1) | |
41 | moveb R(d0),R(d1) | |
42 | movel R(d1),R(d0) | |
43 | swap R(d0) | |
44 | movew R(d1),R(d0) | |
45 | ||
46 | /* First search for the character one byte at a time until the | |
47 | pointer is aligned to a longword boundary. */ | |
48 | movel R(a0),R(d1) | |
9c986f87 AS |
49 | #ifdef __mcoldfire__ |
50 | andl #3,R(d1) | |
51 | #else | |
55dec6d8 | 52 | andw #3,R(d1) |
9c986f87 | 53 | #endif |
55dec6d8 | 54 | beq L(L1) |
9c986f87 AS |
55 | moveb MEM(a0),R(d2) |
56 | cmpb R(d0),R(d2) | |
55dec6d8 | 57 | beq L(L9) |
9c986f87 | 58 | tstb R(d2) |
55dec6d8 AS |
59 | beq L(L9) |
60 | addql #1,R(a0) | |
61 | ||
9c986f87 AS |
62 | #ifdef __mcoldfire__ |
63 | subql #3,R(d1) | |
64 | #else | |
65 | subqw #3,R(d1) | |
66 | #endif | |
55dec6d8 | 67 | beq L(L1) |
9c986f87 AS |
68 | moveb MEM(a0),R(d2) |
69 | cmpb R(d0),R(d2) | |
55dec6d8 | 70 | beq L(L9) |
9c986f87 | 71 | tstb R(d2) |
55dec6d8 AS |
72 | beq L(L9) |
73 | addql #1,R(a0) | |
74 | ||
9c986f87 AS |
75 | #ifdef __mcoldfire__ |
76 | addql #1,R(d1) | |
77 | #else | |
78 | addqw #1,R(d1) | |
79 | #endif | |
55dec6d8 | 80 | beq L(L1) |
9c986f87 AS |
81 | moveb MEM(a0),R(d2) |
82 | cmpb R(d0),R(d2) | |
55dec6d8 | 83 | beq L(L9) |
9c986f87 | 84 | tstb R(d2) |
55dec6d8 AS |
85 | beq L(L9) |
86 | addql #1,R(a0) | |
87 | ||
88 | L(L1:) | |
89 | /* Load the magic bits. Unlike the generic implementation we can | |
90 | use the carry bit as the fourth hole. */ | |
91 | movel #0xfefefeff,R(d3) | |
92 | ||
93 | /* We exit the loop if adding MAGIC_BITS to LONGWORD fails to | |
94 | change any of the hole bits of LONGWORD. | |
95 | ||
96 | 1) Is this safe? Will it catch all the zero bytes? | |
97 | Suppose there is a byte with all zeros. Any carry bits | |
98 | propagating from its left will fall into the hole at its | |
99 | least significant bit and stop. Since there will be no | |
100 | carry from its most significant bit, the LSB of the | |
101 | byte to the left will be unchanged, and the zero will be | |
102 | detected. | |
103 | ||
104 | 2) Is this worthwhile? Will it ignore everything except | |
105 | zero bytes? Suppose every byte of LONGWORD has a bit set | |
106 | somewhere. There will be a carry into bit 8. If bit 8 | |
107 | is set, this will carry into bit 16. If bit 8 is clear, | |
108 | one of bits 9-15 must be set, so there will be a carry | |
109 | into bit 16. Similarly, there will be a carry into bit | |
110 | 24. If one of bits 24-31 is set, there will be a carry | |
111 | into bit 32 (=carry flag), so all of the hole bits will | |
112 | be changed. | |
113 | ||
114 | 3) But wait! Aren't we looking for C, not zero? | |
115 | Good point. So what we do is XOR LONGWORD with a longword, | |
116 | each of whose bytes is C. This turns each byte that is C | |
117 | into a zero. */ | |
118 | ||
119 | L(L2:) | |
120 | /* Get the longword in question. */ | |
121 | movel MEM_POSTINC(a0),R(d1) | |
122 | /* XOR with the byte we search for. */ | |
123 | eorl R(d0),R(d1) | |
124 | ||
125 | /* Add the magic value. We get carry bits reported for each byte | |
126 | which is not C. */ | |
127 | movel R(d3),R(d2) | |
128 | addl R(d1),R(d2) | |
129 | ||
130 | /* Check the fourth carry bit before it is clobbered by the next | |
131 | XOR. If it is not set we have a hit. */ | |
132 | bcc L(L8) | |
133 | ||
134 | /* We are only interested in carry bits that change due to the | |
135 | previous add, so remove original bits. */ | |
136 | eorl R(d1),R(d2) | |
137 | ||
138 | /* Now test for the other three overflow bits. | |
139 | Set all non-carry bits. */ | |
140 | orl R(d3),R(d2) | |
141 | /* Add 1 to get zero if all carry bits were set. */ | |
142 | addql #1,R(d2) | |
143 | ||
144 | /* If we don't get zero then at least one byte of the word equals | |
145 | C. */ | |
146 | bne L(L8) | |
147 | ||
148 | /* Next look for a NUL byte. | |
149 | Restore original longword without reload. */ | |
150 | eorl R(d0),R(d1) | |
151 | /* Add the magic value. We get carry bits reported for each byte | |
152 | which is not NUL. */ | |
153 | movel R(d3),R(d2) | |
154 | addl R(d1),R(d2) | |
155 | ||
156 | /* Check the fourth carry bit before it is clobbered by the next | |
157 | XOR. If it is not set we have a hit. */ | |
158 | bcc L(L8) | |
159 | ||
160 | /* We are only interested in carry bits that change due to the | |
161 | previous add, so remove original bits. */ | |
162 | eorl R(d1),R(d2) | |
163 | ||
164 | /* Now test for the other three overflow bits. | |
165 | Set all non-carry bits. */ | |
166 | orl R(d3),R(d2) | |
167 | /* Add 1 to get zero if all carry bits were set. */ | |
168 | addql #1,R(d2) | |
169 | ||
170 | /* If we don't get zero then at least one byte of the word was | |
171 | NUL. Otherwise continue with the next longword. */ | |
172 | bne L(L8) | |
173 | ||
174 | /* Get the longword in question. */ | |
175 | movel MEM_POSTINC(a0),R(d1) | |
176 | /* XOR with the byte we search for. */ | |
177 | eorl R(d0),R(d1) | |
178 | ||
179 | /* Add the magic value. We get carry bits reported for each byte | |
180 | which is not C. */ | |
181 | movel R(d3),R(d2) | |
182 | addl R(d1),R(d2) | |
183 | ||
184 | /* Check the fourth carry bit before it is clobbered by the next | |
185 | XOR. If it is not set we have a hit. */ | |
186 | bcc L(L8) | |
187 | ||
188 | /* We are only interested in carry bits that change due to the | |
189 | previous add, so remove original bits */ | |
190 | eorl R(d1),R(d2) | |
191 | ||
192 | /* Now test for the other three overflow bits. | |
193 | Set all non-carry bits. */ | |
194 | orl R(d3),R(d2) | |
195 | /* Add 1 to get zero if all carry bits were set. */ | |
196 | addql #1,R(d2) | |
197 | ||
198 | /* If we don't get zero then at least one byte of the word equals | |
199 | C. */ | |
200 | bne L(L8) | |
201 | ||
202 | /* Next look for a NUL byte. | |
203 | Restore original longword without reload. */ | |
204 | eorl R(d0),R(d1) | |
205 | /* Add the magic value. We get carry bits reported for each byte | |
206 | which is not NUL. */ | |
207 | movel R(d3),R(d2) | |
208 | addl R(d1),R(d2) | |
209 | ||
210 | /* Check the fourth carry bit before it is clobbered by the next | |
211 | XOR. If it is not set we have a hit. */ | |
212 | bcc L(L8) | |
213 | ||
214 | /* We are only interested in carry bits that change due to the | |
215 | previous add, so remove original bits */ | |
216 | eorl R(d1),R(d2) | |
217 | ||
218 | /* Now test for the other three overflow bits. | |
219 | Set all non-carry bits. */ | |
220 | orl R(d3),R(d2) | |
221 | /* Add 1 to get zero if all carry bits were set. */ | |
222 | addql #1,R(d2) | |
223 | ||
224 | /* If we don't get zero then at least one byte of the word was | |
225 | NUL. Otherwise continue with the next longword. */ | |
226 | beq L(L2) | |
227 | ||
228 | L(L8:) | |
229 | /* We have a hit. Check to see which byte it was. First | |
230 | compensate for the autoincrement in the loop. */ | |
231 | subql #4,R(a0) | |
232 | ||
233 | moveb MEM(a0),R(d1) | |
234 | cmpb R(d0),R(d1) | |
235 | beq L(L9) | |
236 | tstb R(d1) | |
237 | beq L(L9) | |
238 | addql #1,R(a0) | |
239 | ||
240 | moveb MEM(a0),R(d1) | |
241 | cmpb R(d0),R(d1) | |
242 | beq L(L9) | |
243 | tstb R(d1) | |
244 | beq L(L9) | |
245 | addql #1,R(a0) | |
246 | ||
247 | moveb MEM(a0),R(d1) | |
248 | cmpb R(d0),R(d1) | |
249 | beq L(L9) | |
250 | tstb R(d1) | |
251 | beq L(L9) | |
252 | addql #1,R(a0) | |
253 | ||
254 | /* Otherwise the fourth byte must equal C or be NUL. */ | |
255 | L(L9:) | |
256 | movel R(a0),R(d0) | |
257 | movel MEM_POSTINC(sp),R(d3) | |
50e73d13 AS |
258 | cfi_adjust_cfa_offset (-4) |
259 | cfi_restore (R(d3)) | |
55dec6d8 | 260 | movel MEM_POSTINC(sp),R(d2) |
50e73d13 AS |
261 | cfi_adjust_cfa_offset (-4) |
262 | cfi_restore (R(d2)) | |
55dec6d8 AS |
263 | rts |
264 | END(__strchrnul) | |
265 | ||
7ea51012 | 266 | libc_hidden_def (__strchrnul) |
55dec6d8 | 267 | weak_alias (__strchrnul, strchrnul) |