1 /* Optimized strnlen implementation for PowerPC32/POWER7 using cmpb insn.
2 Copyright (C) 2010-2019 Free Software Foundation, Inc.
3 Contributed by Luis Machado <luisgpm@br.ibm.com>.
4 This file is part of the GNU C Library.
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.
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.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
22 /* int [r3] strnlen (char *s [r3], int size [r4]) */
27 clrrwi r8,r3,2 /* Align the address to word boundary. */
28 add r7,r3,r4 /* Calculate the last acceptable address. */
30 li r0,0 /* Word with null chars. */
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. */
37 #ifdef __LITTLE_ENDIAN__
44 cmplwi cr7,r10,0 /* If r10 == 0, no null's have been found. */
47 clrrwi r7,r7,2 /* Address of last word. */
49 /* Are we now aligned to a doubleword boundary? If so, skip to
50 the main loop. Otherwise, go through the alignment code. */
54 /* Handle WORD2 of pair. */
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 */
68 srwi r6,r5,3 /* Number of loop iterations. */
69 mtctr r6 /* Setup the counter. */
71 /* Main loop to look for the null byte in the string. Since
72 it's a small loop (< 8 instructions), align it to 32-bytes. */
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. */
83 or r5,r9,r10 /* Merge everything in one word. */
88 /* We may have one more word to read. */
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. */
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
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
123 #ifdef __LITTLE_ENDIAN__
128 cntlzw r0,r10 /* Count leading zeros before the match. */
131 srwi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
132 add r3,r3,r0 /* Length until the match. */
138 /* Deals with size <= 16. */
144 clrrwi r7,r7,2 /* Address of last word. */
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. */
149 #ifdef __LITTLE_ENDIAN__
174 libc_hidden_def (__strnlen)
175 weak_alias (__strnlen, strnlen)
176 libc_hidden_builtin_def (strnlen)