]>
Commit | Line | Data |
---|---|---|
55dec6d8 AS |
1 | /* rawmemchr (str, ch) -- Return pointer to first occurrence of CH in STR. |
2 | For Motorola 68000. | |
04277e02 | 3 | Copyright (C) 1999-2019 Free Software Foundation, Inc. |
55dec6d8 AS |
4 | This file is part of the GNU C Library. |
5 | Contributed by Andreas Schwab <schwab@gnu.org>. | |
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 PE |
18 | License along with the GNU C Library. If not, see |
19 | <http://www.gnu.org/licenses/>. */ | |
55dec6d8 AS |
20 | |
21 | #include <sysdep.h> | |
22 | #include "asm-syntax.h" | |
23 | ||
24 | TEXT | |
25 | ENTRY(__rawmemchr) | |
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 AS |
54 | beq L(L1) |
55 | cmpb MEM(a0),R(d0) | |
56 | beq L(L9) | |
57 | addql #1,R(a0) | |
58 | ||
9c986f87 AS |
59 | #ifdef __mcoldfire__ |
60 | subql #3,R(d1) | |
61 | #else | |
62 | subqw #3,R(d1) | |
63 | #endif | |
55dec6d8 AS |
64 | beq L(L1) |
65 | cmpb MEM(a0),R(d0) | |
66 | beq L(L9) | |
67 | addql #1,R(a0) | |
68 | ||
9c986f87 AS |
69 | #ifdef __mcoldfire__ |
70 | addql #1,R(d1) | |
71 | #else | |
72 | addqw #1,R(d1) | |
73 | #endif | |
55dec6d8 AS |
74 | beq L(L1) |
75 | cmpb MEM(a0),R(d0) | |
76 | beq L(L9) | |
77 | addql #1,R(a0) | |
78 | ||
79 | L(L1:) | |
80 | /* Load the magic bits. Unlike the generic implementation we can | |
81 | use the carry bit as the fourth hole. */ | |
82 | movel #0xfefefeff,R(d3) | |
83 | ||
84 | /* We exit the loop if adding MAGIC_BITS to LONGWORD fails to | |
85 | change any of the hole bits of LONGWORD. | |
86 | ||
87 | 1) Is this safe? Will it catch all the zero bytes? | |
88 | Suppose there is a byte with all zeros. Any carry bits | |
89 | propagating from its left will fall into the hole at its | |
90 | least significant bit and stop. Since there will be no | |
91 | carry from its most significant bit, the LSB of the | |
92 | byte to the left will be unchanged, and the zero will be | |
93 | detected. | |
94 | ||
95 | 2) Is this worthwhile? Will it ignore everything except | |
96 | zero bytes? Suppose every byte of LONGWORD has a bit set | |
97 | somewhere. There will be a carry into bit 8. If bit 8 | |
98 | is set, this will carry into bit 16. If bit 8 is clear, | |
99 | one of bits 9-15 must be set, so there will be a carry | |
100 | into bit 16. Similarly, there will be a carry into bit | |
101 | 24. If one of bits 24-31 is set, there will be a carry | |
102 | into bit 32 (=carry flag), so all of the hole bits will | |
103 | be changed. | |
104 | ||
105 | 3) But wait! Aren't we looking for C, not zero? | |
106 | Good point. So what we do is XOR LONGWORD with a longword, | |
107 | each of whose bytes is C. This turns each byte that is C | |
108 | into a zero. */ | |
109 | ||
110 | L(L2:) | |
111 | /* Get the longword in question. */ | |
112 | movel MEM_POSTINC(a0),R(d1) | |
113 | /* XOR with the byte we search for. */ | |
114 | eorl R(d0),R(d1) | |
115 | ||
116 | /* Add the magic value. We get carry bits reported for each byte | |
117 | which is not C. */ | |
118 | movel R(d3),R(d2) | |
119 | addl R(d1),R(d2) | |
120 | ||
121 | /* Check the fourth carry bit before it is clobbered by the next | |
122 | XOR. If it is not set we have a hit. */ | |
123 | bcc L(L8) | |
124 | ||
125 | /* We are only interested in carry bits that change due to the | |
126 | previous add, so remove original bits. */ | |
127 | eorl R(d1),R(d2) | |
128 | ||
129 | /* Now test for the other three overflow bits. | |
130 | Set all non-carry bits. */ | |
131 | orl R(d3),R(d2) | |
132 | /* Add 1 to get zero if all carry bits were set. */ | |
133 | addql #1,R(d2) | |
134 | ||
135 | /* If we don't get zero then at least one byte of the word equals | |
136 | C. */ | |
137 | bne L(L8) | |
138 | ||
139 | /* Get the longword in question. */ | |
140 | movel MEM_POSTINC(a0),R(d1) | |
141 | /* XOR with the byte we search for. */ | |
142 | eorl R(d0),R(d1) | |
143 | ||
144 | /* Add the magic value. We get carry bits reported for each byte | |
145 | which is not C. */ | |
146 | movel R(d3),R(d2) | |
147 | addl R(d1),R(d2) | |
148 | ||
149 | /* Check the fourth carry bit before it is clobbered by the next | |
150 | XOR. If it is not set we have a hit. */ | |
151 | bcc L(L8) | |
152 | ||
153 | /* We are only interested in carry bits that change due to the | |
154 | previous add, so remove original bits */ | |
155 | eorl R(d1),R(d2) | |
156 | ||
157 | /* Now test for the other three overflow bits. | |
158 | Set all non-carry bits. */ | |
159 | orl R(d3),R(d2) | |
160 | /* Add 1 to get zero if all carry bits were set. */ | |
161 | addql #1,R(d2) | |
162 | ||
163 | /* If we don't get zero then at least one byte of the word equals | |
164 | C. */ | |
165 | beq L(L2) | |
166 | ||
167 | L(L8:) | |
168 | /* We have a hit. Check to see which byte it was. First | |
169 | compensate for the autoincrement in the loop. */ | |
170 | subql #4,R(a0) | |
171 | ||
172 | cmpb MEM(a0),R(d0) | |
173 | beq L(L9) | |
174 | addql #1,R(a0) | |
175 | ||
176 | cmpb MEM(a0),R(d0) | |
177 | beq L(L9) | |
178 | addql #1,R(a0) | |
179 | ||
180 | cmpb MEM(a0),R(d0) | |
181 | beq L(L9) | |
182 | addql #1,R(a0) | |
183 | ||
184 | /* Otherwise the fourth byte must equal C. */ | |
185 | L(L9:) | |
186 | movel R(a0),R(d0) | |
187 | movel MEM_POSTINC(sp),R(d3) | |
50e73d13 AS |
188 | cfi_adjust_cfa_offset (-4) |
189 | cfi_restore (R(d3)) | |
55dec6d8 | 190 | movel MEM_POSTINC(sp),R(d2) |
50e73d13 AS |
191 | cfi_adjust_cfa_offset (-4) |
192 | cfi_restore (R(d2)) | |
55dec6d8 AS |
193 | rts |
194 | END(__rawmemchr) | |
195 | ||
b8daff95 | 196 | libc_hidden_def (__rawmemchr) |
55dec6d8 | 197 | weak_alias (__rawmemchr, rawmemchr) |