]>
Commit | Line | Data |
---|---|---|
d4697bc9 | 1 | /* Copyright (C) 1996-2014 Free Software Foundation, Inc. |
95a89bf3 | 2 | Contributed by David Mosberger (davidm@cs.arizona.edu). |
922ac641 | 3 | This file is part of the GNU C Library. |
95a89bf3 | 4 | |
922ac641 | 5 | The GNU C Library is free software; you can redistribute it and/or |
3214b89b AJ |
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. | |
95a89bf3 | 9 | |
922ac641 UD |
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 | |
3214b89b | 13 | Lesser General Public License for more details. |
95a89bf3 | 14 | |
3214b89b | 15 | You should have received a copy of the GNU Lesser General Public |
ab84e3ff PE |
16 | License along with the GNU C Library. If not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
95a89bf3 RM |
18 | |
19 | /* Finds length of a 0-terminated string. Optimized for the Alpha | |
b870eeda | 20 | architecture: |
95a89bf3 RM |
21 | |
22 | - memory accessed as aligned quadwords only | |
b870eeda UD |
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 | */ | |
95a89bf3 RM |
28 | |
29 | #include <sysdep.h> | |
95a89bf3 | 30 | |
b870eeda UD |
31 | .set noreorder |
32 | .set noat | |
95a89bf3 RM |
33 | |
34 | ENTRY(strlen) | |
60c74cf0 UD |
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 | ||
b870eeda UD |
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) | |
79b7c863 | 76 | libc_hidden_builtin_def (strlen) |