1 /* Optimized rawmemchr implementation for PowerPC64/POWER7 using cmpb insn.
2 Copyright (C) 2010 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, write to the Free
18 Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA
25 /* int [r3] rawmemchr (void *s [r3], int c [r4]) */
27 ENTRY (BP_SYM(__rawmemchr))
30 clrrdi r8,r3,3 /* Align the address to doubleword boundary. */
32 /* Replicate byte to doubleword. */
37 /* Now r4 has a doubleword of c bytes. */
39 rlwinm r6,r3,3,26,28 /* Calculate padding. */
40 ld r12,0(r8) /* Load doubleword from memory. */
41 cmpb r5,r12,r4 /* Compare each byte against c byte. */
42 sld r5,r5,r6 /* Move left to discard ignored bits. */
43 srd r5,r5,r6 /* Bring the bits back as zeros. */
44 cmpdi cr7,r5,0 /* If r5 == 0, no c bytes have been found. */
49 /* Are we now aligned to a quadword boundary? If so, skip to
50 the main loop. Otherwise, go through the alignment code. */
54 /* Handle DWORD2 of pair. */
59 b L(loop) /* We branch here (rather than falling through)
60 to skip the nops due to heavy alignment
63 /* Main loop to look for the end of the string. Since it's a
64 small loop (< 8 instructions), align it to 32-bytes. */
67 /* Load two doublewords, compare and merge in a
68 single register for speed. This is an attempt
69 to speed up the byte-checking process for bigger strings. */
78 /* OK, one (or both) of the doublewords contains a 'c' byte. Check
79 the first doubleword and decrement the address in case the first
80 doubleword really contains a c byte. */
86 /* The 'c' byte must be in the second doubleword. Adjust the address
87 again and move the result of cmpb to r10 so we can calculate the
92 /* r5 has the output of the cmpb instruction, that is, it contains
93 0xff in the same position as the 'c' byte in the original
94 doubleword from the string. Use that fact to find out what is
95 the position of the byte inside the string. */
97 cntlzd r0,r5 /* Count leading zeros before the match. */
98 srdi r0,r0,3 /* Convert leading zeroes to bytes. */
99 add r3,r8,r0 /* Return address of the matching char. */
101 END (BP_SYM (__rawmemchr))
102 weak_alias (__rawmemchr,rawmemchr)
103 libc_hidden_builtin_def (__rawmemchr)