]>
Commit | Line | Data |
---|---|---|
fe2f79db | 1 | /* Optimized strnlen implementation for PowerPC32/POWER7 using cmpb insn. |
b168057a | 2 | Copyright (C) 2010-2015 Free Software Foundation, Inc. |
fe2f79db LM |
3 | Contributed by Luis Machado <luisgpm@br.ibm.com>. |
4 | This file is part of the GNU C Library. | |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Lesser General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
10 | ||
11 | The GNU C Library is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 PE |
17 | License along with the GNU C Library; if not, see |
18 | <http://www.gnu.org/licenses/>. */ | |
fe2f79db LM |
19 | |
20 | #include <sysdep.h> | |
fe2f79db LM |
21 | |
22 | /* int [r3] strnlen (char *s [r3], int size [r4]) */ | |
23 | .machine power7 | |
b5510883 | 24 | ENTRY (__strnlen) |
fe2f79db LM |
25 | CALL_MCOUNT |
26 | dcbt 0,r3 | |
27 | clrrwi r8,r3,2 /* Align the address to word boundary. */ | |
28 | add r7,r3,r4 /* Calculate the last acceptable address. */ | |
29 | cmplwi r4,16 | |
30 | li r0,0 /* Word with null chars. */ | |
33ee81de | 31 | addi r7,r7,-1 |
fe2f79db LM |
32 | ble L(small_range) |
33 | ||
fe2f79db LM |
34 | rlwinm r6,r3,3,27,28 /* Calculate padding. */ |
35 | lwz r12,0(r8) /* Load word from memory. */ | |
36 | cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */ | |
33ee81de AM |
37 | #ifdef __LITTLE_ENDIAN__ |
38 | srw r10,r10,r6 | |
39 | slw r10,r10,r6 | |
40 | #else | |
fe2f79db LM |
41 | slw r10,r10,r6 |
42 | srw r10,r10,r6 | |
33ee81de | 43 | #endif |
fe2f79db LM |
44 | cmplwi cr7,r10,0 /* If r10 == 0, no null's have been found. */ |
45 | bne cr7,L(done) | |
46 | ||
33ee81de | 47 | clrrwi r7,r7,2 /* Address of last word. */ |
fe2f79db LM |
48 | mtcrf 0x01,r8 |
49 | /* Are we now aligned to a doubleword boundary? If so, skip to | |
50 | the main loop. Otherwise, go through the alignment code. */ | |
51 | ||
52 | bt 29,L(loop_setup) | |
53 | ||
33ee81de | 54 | /* Handle WORD2 of pair. */ |
fe2f79db LM |
55 | lwzu r12,4(r8) |
56 | cmpb r10,r12,r0 | |
57 | cmplwi cr7,r10,0 | |
58 | bne cr7,L(done) | |
59 | ||
fe2f79db | 60 | L(loop_setup): |
33ee81de AM |
61 | /* The last word we want to read in the loop below is the one |
62 | containing the last byte of the string, ie. the word at | |
63 | (s + size - 1) & ~3, or r7. The first word read is at | |
64 | r8 + 4, we read 2 * cnt words, so the last word read will | |
65 | be at r8 + 4 + 8 * cnt - 4. Solving for cnt gives | |
66 | cnt = (r7 - r8) / 8 */ | |
67 | sub r5,r7,r8 | |
fe2f79db LM |
68 | srwi r6,r5,3 /* Number of loop iterations. */ |
69 | mtctr r6 /* Setup the counter. */ | |
33ee81de AM |
70 | |
71 | /* Main loop to look for the null byte in the string. Since | |
fe2f79db LM |
72 | it's a small loop (< 8 instructions), align it to 32-bytes. */ |
73 | .p2align 5 | |
74 | L(loop): | |
75 | /* Load two words, compare and merge in a | |
76 | single register for speed. This is an attempt | |
77 | to speed up the null-checking process for bigger strings. */ | |
78 | ||
79 | lwz r12,4(r8) | |
80 | lwzu r11,8(r8) | |
81 | cmpb r10,r12,r0 | |
82 | cmpb r9,r11,r0 | |
83 | or r5,r9,r10 /* Merge everything in one word. */ | |
84 | cmplwi cr7,r5,0 | |
85 | bne cr7,L(found) | |
86 | bdnz L(loop) | |
33ee81de AM |
87 | |
88 | /* We may have one more word to read. */ | |
89 | cmplw cr6,r8,r7 | |
90 | beq cr6,L(end_max) | |
91 | ||
92 | lwzu r12,4(r8) | |
93 | cmpb r10,r12,r0 | |
94 | cmplwi cr6,r10,0 | |
95 | bne cr6,L(done) | |
fe2f79db LM |
96 | |
97 | L(end_max): | |
33ee81de | 98 | mr r3,r4 |
fe2f79db LM |
99 | blr |
100 | ||
101 | /* OK, one (or both) of the words contains a null byte. Check | |
102 | the first word and decrement the address in case the first | |
103 | word really contains a null byte. */ | |
104 | .align 4 | |
105 | L(found): | |
106 | cmplwi cr6,r10,0 | |
107 | addi r8,r8,-4 | |
108 | bne cr6,L(done) | |
109 | ||
110 | /* The null byte must be in the second word. Adjust the address | |
111 | again and move the result of cmpb to r10 so we can calculate the | |
112 | length. */ | |
113 | ||
114 | mr r10,r9 | |
115 | addi r8,r8,4 | |
116 | ||
117 | /* r10 has the output of the cmpb instruction, that is, it contains | |
118 | 0xff in the same position as the null byte in the original | |
119 | word from the string. Use that to calculate the length. | |
120 | We need to make sure the null char is *before* the end of the | |
121 | range. */ | |
122 | L(done): | |
33ee81de AM |
123 | #ifdef __LITTLE_ENDIAN__ |
124 | addi r0,r10,-1 | |
125 | andc r0,r0,r10 | |
126 | popcntw r0,r0 | |
127 | #else | |
128 | cntlzw r0,r10 /* Count leading zeros before the match. */ | |
129 | #endif | |
130 | sub r3,r8,r3 | |
131 | srwi r0,r0,3 /* Convert leading/trailing zeros to bytes. */ | |
132 | add r3,r3,r0 /* Length until the match. */ | |
133 | cmplw r3,r4 | |
134 | blelr | |
135 | mr r3,r4 | |
fe2f79db LM |
136 | blr |
137 | ||
33ee81de | 138 | /* Deals with size <= 16. */ |
fe2f79db LM |
139 | .align 4 |
140 | L(small_range): | |
141 | cmplwi r4,0 | |
33ee81de AM |
142 | beq L(end_max) |
143 | ||
144 | clrrwi r7,r7,2 /* Address of last word. */ | |
fe2f79db LM |
145 | |
146 | rlwinm r6,r3,3,27,28 /* Calculate padding. */ | |
147 | lwz r12,0(r8) /* Load word from memory. */ | |
148 | cmpb r10,r12,r0 /* Check for null bytes in WORD1. */ | |
33ee81de AM |
149 | #ifdef __LITTLE_ENDIAN__ |
150 | srw r10,r10,r6 | |
151 | slw r10,r10,r6 | |
152 | #else | |
fe2f79db LM |
153 | slw r10,r10,r6 |
154 | srw r10,r10,r6 | |
33ee81de | 155 | #endif |
fe2f79db LM |
156 | cmplwi cr7,r10,0 |
157 | bne cr7,L(done) | |
158 | ||
33ee81de AM |
159 | cmplw r8,r7 |
160 | beq L(end_max) | |
fe2f79db LM |
161 | |
162 | .p2align 5 | |
163 | L(loop_small): | |
164 | lwzu r12,4(r8) | |
165 | cmpb r10,r12,r0 | |
fe2f79db LM |
166 | cmplwi cr6,r10,0 |
167 | bne cr6,L(done) | |
33ee81de AM |
168 | cmplw r8,r7 |
169 | bne L(loop_small) | |
170 | mr r3,r4 | |
171 | blr | |
172 | ||
b5510883 JM |
173 | END (__strnlen) |
174 | weak_alias (__strnlen, strnlen) | |
fe2f79db | 175 | libc_hidden_builtin_def (strnlen) |