1 /* Optimized strchr implementation for PowerPC64/POWER7 using cmpb insn.
2 Copyright (C) 2010-2017 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/>. */
23 # define STRCHR strchr
26 /* int [r3] strchr (char *s [r3], int c [r4]) */
31 clrrdi r8,r3,3 /* Align the address to doubleword boundary. */
33 ld r12,0(r8) /* Load doubleword from memory. */
34 li r0,0 /* Doubleword with null chars to use
37 rlwinm r6,r3,3,26,28 /* Calculate padding. */
41 /* Replicate byte to doubleword. */
46 /* Now r4 has a doubleword of c bytes and r0 has
47 a doubleword of null bytes. */
49 cmpb r10,r12,r4 /* Compare each byte against c byte. */
50 cmpb r11,r12,r0 /* Compare each byte against null byte. */
52 /* Move the doublewords left and right to discard the bits that are
53 not part of the string and bring them back as zeros. */
54 #ifdef __LITTLE_ENDIAN__
65 or r5,r10,r11 /* OR the results to speed things up. */
66 cmpdi cr7,r5,0 /* If r5 == 0, no c or null bytes
72 /* Are we now aligned to a doubleword boundary? If so, skip to
73 the main loop. Otherwise, go through the alignment code. */
77 /* Handle WORD2 of pair. */
84 b L(loop) /* We branch here (rather than falling through)
85 to skip the nops due to heavy alignment
90 /* Load two doublewords, compare and merge in a
91 single register for speed. This is an attempt
92 to speed up the null-checking process for bigger strings. */
105 /* OK, one (or both) of the doublewords contains a c/null byte. Check
106 the first doubleword and decrement the address in case the first
107 doubleword really contains a c/null byte. */
113 /* The c/null byte must be in the second doubleword. Adjust the
114 address again and move the result of cmpb to r10 so we can calculate
121 /* r10/r11 have the output of the cmpb instructions, that is,
122 0xff in the same position as the c/null byte in the original
123 doubleword from the string. Use that to calculate the pointer. */
125 #ifdef __LITTLE_ENDIAN__
134 cntlzd r0,r10 /* Count leading zeros before c matches. */
138 srdi r0,r0,3 /* Convert leading zeros to bytes. */
139 add r3,r8,r0 /* Return address of the matching c byte
140 or null in case c was not found. */
148 /* We are here because strchr was called with a null byte. */
151 /* r0 has a doubleword of null bytes. */
153 cmpb r5,r12,r0 /* Compare each byte against null bytes. */
155 /* Move the doublewords left and right to discard the bits that are
156 not part of the string and bring them back as zeros. */
157 #ifdef __LITTLE_ENDIAN__
164 cmpdi cr7,r5,0 /* If r10 == 0, no c or null bytes
170 /* Are we now aligned to a quadword boundary? If so, skip to
171 the main loop. Otherwise, go through the alignment code. */
175 /* Handle WORD2 of pair. */
180 b L(loop_null) /* We branch here (rather than falling through)
181 to skip the nops due to heavy alignment
182 of the loop below. */
184 /* Main loop to look for the end of the string. Since it's a
185 small loop (< 8 instructions), align it to 32-bytes. */
188 /* Load two doublewords, compare and merge in a
189 single register for speed. This is an attempt
190 to speed up the null-checking process for bigger strings. */
199 /* OK, one (or both) of the doublewords contains a null byte. Check
200 the first doubleword and decrement the address in case the first
201 doubleword really contains a null byte. */
207 /* The null byte must be in the second doubleword. Adjust the address
208 again and move the result of cmpb to r10 so we can calculate the
214 /* r5 has the output of the cmpb instruction, that is, it contains
215 0xff in the same position as the null byte in the original
216 doubleword from the string. Use that to calculate the pointer. */
218 #ifdef __LITTLE_ENDIAN__
223 cntlzd r0,r5 /* Count leading zeros before the match. */
225 srdi r0,r0,3 /* Convert leading zeros to bytes. */
226 add r3,r8,r0 /* Return address of the matching null byte. */
229 weak_alias (strchr, index)
230 libc_hidden_builtin_def (strchr)