1 /*
2 * Copyright (c) 2008-2015 ARM Ltd
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. The name of the company may not be used to endorse or promote
14 * products derived from this software without specific prior written
15 * permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
22 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
23 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
24 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
25 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
26 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include <picolibc.h>
30
31 #include "arm_asm.h"
32 #include <string.h>
33 #include <limits.h>
34
35 #if defined __OPTIMIZE_SIZE__ || defined PREFER_SIZE_OVER_SPEED
36 #if __ARM_ARCH_ISA_THUMB == 2
37 /* Implemented in strlen.S. */
38
39 #elif defined (__thumb__)
40 /* Implemented in strlen.S. */
41
42 #else
43 #include "../../string/strlen.c"
44
45 #endif
46
47 #else /* defined __OPTIMIZE_SIZE__ || defined PREFER_SIZE_OVER_SPEED */
48 #if defined __thumb__ && ! defined __thumb2__
49 #include "../../string/strlen.c"
50
51 #elif __ARM_ARCH_ISA_THUMB >= 2 && defined __ARM_FEATURE_DSP
52 /* Implemented in strlen.S. */
53
54 #else
55 #pragma GCC diagnostic ignored "-Wunused-parameter"
56 size_t __attribute__((naked))
strlen(const char * str)57 strlen (const char* str)
58 {
59 __asm__("len .req r0\n\t"
60 "data .req r3\n\t"
61 "addr .req r1\n\t"
62
63 #ifdef _ISA_ARM_7
64 "pld [r0]\n\t"
65 #endif
66 /* Word-align address */
67 "bic addr, r0, #3\n\t"
68 /* Get adjustment for start ... */
69 "ands len, r0, #3\n\t"
70 "neg len, len\n\t"
71 /* First word of data */
72 "ldr data, [addr], #4\n\t"
73 /* Ensure bytes preceeding start ... */
74 "add ip, len, #4\n\t"
75 "mov ip, ip, asl #3\n\t"
76 "mvn r2, #0\n\t"
77 /* ... are masked out */
78 #ifdef __thumb__
79 "itt ne\n\t"
80 # ifdef __ARMEB__
81 "lslne r2, ip\n\t"
82 # else
83 "lsrne r2, ip\n\t"
84 # endif
85 "orrne data, data, r2\n\t"
86 #else
87 "it ne\n\t"
88 # ifdef __ARMEB__
89 "orrne data, data, r2, lsl ip\n\t"
90 # else
91 "orrne data, data, r2, lsr ip\n\t"
92 # endif
93 #endif
94 /* Magic const 0x01010101 */
95 #ifdef _ISA_ARM_7
96 "movw ip, #0x101\n\t"
97 #else
98 "mov ip, #0x1\n\t"
99 "orr ip, ip, ip, lsl #8\n\t"
100 #endif
101 "orr ip, ip, ip, lsl #16\n"
102
103 /* This is the main loop. We subtract one from each byte in
104 the word: the sign bit changes iff the byte was zero or
105 0x80 -- we eliminate the latter case by anding the result
106 with the 1-s complement of the data. */
107 "1:\n\t"
108 /* test (data - 0x01010101) */
109 "sub r2, data, ip\n\t"
110 /* ... & ~data */
111 "bic r2, r2, data\n\t"
112 /* ... & 0x80808080 == 0? */
113 "ands r2, r2, ip, lsl #7\n\t"
114 #ifdef _ISA_ARM_7
115 /* yes, get more data... */
116 "itt eq\n\t"
117 "ldreq data, [addr], #4\n\t"
118 /* and 4 more bytes */
119 "addeq len, len, #4\n\t"
120 /* Unroll the loop a bit. */
121 "pld [addr, #8]\n\t"
122 /* test (data - 0x01010101) */
123 "ittt eq\n\t"
124 "subeq r2, data, ip\n\t"
125 /* ... & ~data */
126 "biceq r2, r2, data\n\t"
127 /* ... & 0x80808080 == 0? */
128 "andeqs r2, r2, ip, lsl #7\n\t"
129 #endif
130 "itt eq\n\t"
131 /* yes, get more data... */
132 "ldreq data, [addr], #4\n\t"
133 /* and 4 more bytes */
134 "addeq len, len, #4\n\t"
135 "beq 1b\n\t"
136 #ifdef __ARMEB__
137 "tst data, #0xff000000\n\t"
138 "itttt ne\n\t"
139 "addne len, len, #1\n\t"
140 "tstne data, #0xff0000\n\t"
141 "addne len, len, #1\n\t"
142 "tstne data, #0xff00\n\t"
143 "it ne\n\t"
144 "addne len, len, #1\n\t"
145 #else
146 # ifdef _ISA_ARM_5
147 /* R2 is the residual sign bits from the above test. All we
148 need to do now is establish the position of the first zero
149 byte... */
150 /* Little-endian is harder, we need the number of trailing
151 zeros / 8 */
152 # ifdef _ISA_ARM_7
153 "rbit r2, r2\n\t"
154 "clz r2, r2\n\t"
155 # else
156 "rsb r1, r2, #0\n\t"
157 "and r2, r2, r1\n\t"
158 "clz r2, r2\n\t"
159 "rsb r2, r2, #31\n\t"
160 # endif
161 "add len, len, r2, lsr #3\n\t"
162 # else /* No CLZ instruction */
163 "tst data, #0xff\n\t"
164 "itttt ne\n\t"
165 "addne len, len, #1\n\t"
166 "tstne data, #0xff00\n\t"
167 "addne len, len, #1\n\t"
168 "tstne data, #0xff0000\n\t"
169 "it ne\n\t"
170 "addne len, len, #1\n\t"
171 # endif
172 #endif
173 "bx lr\n\t");
174 }
175 #endif
176 #endif
177
