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1/* Copyright (C) 1996-2019 Free Software Foundation, Inc.
2 Contributed by David Mosberger (davidm@cs.arizona.edu).
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library. If not, see
17 <http://www.gnu.org/licenses/>. */
18
19/* Finds length of a 0-terminated string. Optimized for the Alpha
20 architecture:
21
22 - memory accessed as aligned quadwords only
23 - uses cmpbge to compare 8 bytes in parallel
24 - does binary search to find 0 byte in last quadword (HAKMEM
25 needed 12 instructions to do this instead of the 8 instructions
26 that the binary search needs).
27*/
28
29#include <sysdep.h>
30
31 .set noreorder
32 .set noat
33
34ENTRY(strlen)
35#ifdef PROF
36 ldgp gp, 0(pv)
37 lda AT, _mcount
38 jsr AT, (AT), _mcount
39 .prologue 1
40#else
41 .prologue 0
42#endif
43
44 ldq_u t0, 0(a0) # load first quadword (a0 may be misaligned)
45 lda t1, -1(zero)
46 insqh t1, a0, t1
47 andnot a0, 7, v0
48 or t1, t0, t0
49 nop # dual issue the next two on ev5
50 cmpbge zero, t0, t1 # t1 <- bitmask: bit i == 1 <==> i-th byte == 0
51 bne t1, $found
52
53$loop: ldq t0, 8(v0)
54 addq v0, 8, v0 # addr += 8
55 cmpbge zero, t0, t1
56 beq t1, $loop
57
58$found: negq t1, t2 # clear all but least set bit
59 and t1, t2, t1
60
61 and t1, 0xf0, t2 # binary search for that set bit
62 and t1, 0xcc, t3
63 and t1, 0xaa, t4
64 cmovne t2, 4, t2
65 cmovne t3, 2, t3
66 cmovne t4, 1, t4
67 addq t2, t3, t2
68 addq v0, t4, v0
69 addq v0, t2, v0
70 nop # dual issue next two on ev4 and ev5
71
72 subq v0, a0, v0
73 ret
74
75 END(strlen)
76libc_hidden_builtin_def (strlen)
77

Warning: That file was not part of the compilation database. It may have many parsing errors.