1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
/* Optimized rawmemchr implementation for PowerPC64/POWER7 using cmpb insn.
Copyright (C) 2010-2015 Free Software Foundation, Inc.
Contributed by Luis Machado <luisgpm@br.ibm.com>.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* int [r3] rawmemchr (void *s [r3], int c [r4]) */
.machine power7
ENTRY (__rawmemchr)
CALL_MCOUNT 2
dcbt 0,r3
clrrdi r8,r3,3 /* Align the address to doubleword boundary. */
/* Replicate byte to doubleword. */
insrdi r4,r4,8,48
insrdi r4,r4,16,32
insrdi r4,r4,32,0
/* Now r4 has a doubleword of c bytes. */
rlwinm r6,r3,3,26,28 /* Calculate padding. */
ld r12,0(r8) /* Load doubleword from memory. */
cmpb r5,r12,r4 /* Compare each byte against c byte. */
#ifdef __LITTLE_ENDIAN__
srd r5,r5,r6
sld r5,r5,r6
#else
sld r5,r5,r6 /* Move left to discard ignored bits. */
srd r5,r5,r6 /* Bring the bits back as zeros. */
#endif
cmpdi cr7,r5,0 /* If r5 == 0, no c bytes have been found. */
bne cr7,L(done)
mtcrf 0x01,r8
/* Are we now aligned to a quadword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
bt 28,L(loop)
/* Handle DWORD2 of pair. */
ldu r12,8(r8)
cmpb r5,r12,r4
cmpdi cr7,r5,0
bne cr7,L(done)
b L(loop) /* We branch here (rather than falling through)
to skip the nops due to heavy alignment
of the loop below. */
/* Main loop to look for the end of the string. Since it's a
small loop (< 8 instructions), align it to 32-bytes. */
.p2align 5
L(loop):
/* Load two doublewords, compare and merge in a
single register for speed. This is an attempt
to speed up the byte-checking process for bigger strings. */
ld r12,8(r8)
ldu r11,16(r8)
cmpb r5,r12,r4
cmpb r6,r11,r4
or r7,r5,r6
cmpdi cr7,r7,0
beq cr7,L(loop)
/* OK, one (or both) of the doublewords contains a 'c' byte. Check
the first doubleword and decrement the address in case the first
doubleword really contains a c byte. */
cmpdi cr6,r5,0
addi r8,r8,-8
bne cr6,L(done)
/* The 'c' byte must be in the second doubleword. Adjust the address
again and move the result of cmpb to r10 so we can calculate the
pointer. */
mr r5,r6
addi r8,r8,8
/* r5 has the output of the cmpb instruction, that is, it contains
0xff in the same position as the 'c' byte in the original
doubleword from the string. Use that fact to find out what is
the position of the byte inside the string. */
L(done):
#ifdef __LITTLE_ENDIAN__
addi r0,r5,-1
andc r0,r0,r5
popcntd r0,r0 /* Count trailing zeros. */
#else
cntlzd r0,r5 /* Count leading zeros before the match. */
#endif
srdi r0,r0,3 /* Convert leading zeros to bytes. */
add r3,r8,r0 /* Return address of the matching char. */
blr
END (__rawmemchr)
weak_alias (__rawmemchr,rawmemchr)
libc_hidden_builtin_def (__rawmemchr)
|
