1 /* Optimized memchr implementation for PowerPC32/POWER7 using cmpb insn.
2 Copyright (C) 2010-2013 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/>. */
24 /* int [r3] memchr (char *s [r3], int byte [r4], int size [r5]) */
26 ENTRY (BP_SYM (__memchr))
32 add r7,r3,r5 /* Calculate the last acceptable address. */
36 cmplw cr7,r3,r7 /* Compare the starting address (r3) with the
37 ending address (r7). If (r3 >= r7), the size
38 passed in is zero or negative. */
41 li r7,-1 /* Artificially set our ending address (r7)
42 such that we will exit early. */
44 rlwinm r6,r3,3,27,28 /* Calculate padding. */
45 cmpli cr6,r6,0 /* cr6 == Do we have padding? */
46 lwz r12,0(r8) /* Load word from memory. */
47 cmpb r10,r12,r4 /* Check for BYTEs in WORD1. */
48 beq cr6,L(proceed_no_padding)
51 L(proceed_no_padding):
52 cmplwi cr7,r10,0 /* If r10 == 0, no BYTEs have been found. */
55 /* Are we done already? */
61 /* Are we now aligned to a doubleword boundary? If so, skip to
62 the main loop. Otherwise, go through the alignment code. */
66 /* Handle WORD2 of pair. */
72 /* Are we done already? */
79 srwi r6,r5,3 /* Number of loop iterations. */
80 mtctr r6 /* Setup the counter. */
82 /* Main loop to look for BYTE backwards in the string. Since
83 it's a small loop (< 8 instructions), align it to 32-bytes. */
86 /* Load two words, compare and merge in a
87 single register for speed. This is an attempt
88 to speed up the byte-checking process for bigger strings. */
93 or r5,r9,r10 /* Merge everything in one word. */
98 /* We're here because the counter reached 0, and that means we
99 didn't have any matches for BYTE in the whole range. */
102 blt cr6,L(loop_small)
105 /* OK, one (or both) of the words contains BYTE. Check
106 the first word and decrement the address in case the first
107 word really contains BYTE. */
114 /* BYTE must be in the second word. Adjust the address
115 again and move the result of cmpb to r10 so we can calculate the
121 /* r10 has the output of the cmpb instruction, that is, it contains
122 0xff in the same position as BYTE in the original
123 word from the string. Use that to calculate the pointer.
124 We need to make sure BYTE is *before* the end of the range. */
126 cntlzw r0,r10 /* Count leading zeroes before the match. */
127 srwi r0,r0,3 /* Convert leading zeroes to bytes. */
138 /* Deals with size <= 16. */
142 rlwinm r6,r3,3,27,28 /* Calculate padding. */
143 beq L(null) /* This branch is for the cmplwi r5,0 above */
144 lwz r12,0(r8) /* Load word from memory. */
145 cmplwi cr6,r6,0 /* cr6 == Do we have padding? */
146 cmpb r10,r12,r4 /* Check for BYTE in DWORD1. */
147 beq cr6,L(small_no_padding)
154 /* Are we done already? */
159 L(loop_small): /* loop_small has been unrolled. */
192 /* For most cases we will never get here. Under some combinations of
193 padding + length there is a leftover word that still needs to be
201 /* save a branch and exit directly */
205 END (BP_SYM (__memchr))
206 weak_alias (BP_SYM (__memchr), BP_SYM(memchr))
207 libc_hidden_builtin_def (memchr)