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192.168.1.100 / T800 / b4bfae9066747d414c41d9c6db8cbf3a1c96c0f1 / . / src / kernel / linux / v4.19 / arch / alpha / lib / ev67-strrchr.S
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xjb04a4022021-11-25 15:01:52 +0800[diff] [blame]1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * arch/alpha/lib/ev67-strrchr.S
4 * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
5 *
6 * Finds length of a 0-terminated string. Optimized for the
7 * Alpha architecture:
8 *
9 * - memory accessed as aligned quadwords only
10 * - uses bcmpge to compare 8 bytes in parallel
11 *
12 * Much of the information about 21264 scheduling/coding comes from:
13 * Compiler Writer's Guide for the Alpha 21264
14 * abbreviated as 'CWG' in other comments here
15 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
16 * Scheduling notation:
17 * E - either cluster
18 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
19 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
20 */
21
22#include <asm/export.h>
23#include <asm/regdef.h>
24
25 .set noreorder
26 .set noat
27
28 .align 4
29 .ent strrchr
30 .globl strrchr
31strrchr:
32 .frame sp, 0, ra
33 .prologue 0
34
35 and a1, 0xff, t2 # E : 00000000000000ch
36 insbl a1, 1, t4 # U : 000000000000ch00
37 insbl a1, 2, t5 # U : 0000000000ch0000
38 ldq_u t0, 0(a0) # L : load first quadword Latency=3
39
40 mov zero, t6 # E : t6 is last match aligned addr
41 or t2, t4, a1 # E : 000000000000chch
42 sll t5, 8, t3 # U : 00000000ch000000
43 mov zero, t8 # E : t8 is last match byte compare mask
44
45 andnot a0, 7, v0 # E : align source addr
46 or t5, t3, t3 # E : 00000000chch0000
47 sll a1, 32, t2 # U : 0000chch00000000
48 sll a1, 48, t4 # U : chch000000000000
49
50 or t4, a1, a1 # E : chch00000000chch
51 or t2, t3, t2 # E : 0000chchchch0000
52 or a1, t2, a1 # E : chchchchchchchch
53 lda t5, -1 # E : build garbage mask
54
55 cmpbge zero, t0, t1 # E : bits set iff byte == zero
56 mskqh t5, a0, t4 # E : Complete garbage mask
57 xor t0, a1, t2 # E : make bytes == c zero
58 cmpbge zero, t4, t4 # E : bits set iff byte is garbage
59
60 cmpbge zero, t2, t3 # E : bits set iff byte == c
61 andnot t1, t4, t1 # E : clear garbage from null test
62 andnot t3, t4, t3 # E : clear garbage from char test
63 bne t1, $eos # U : did we already hit the terminator?
64
65 /* Character search main loop */
66$loop:
67 ldq t0, 8(v0) # L : load next quadword
68 cmovne t3, v0, t6 # E : save previous comparisons match
69 nop # : Latency=2, extra map slot (keep nop with cmov)
70 nop
71
72 cmovne t3, t3, t8 # E : Latency=2, extra map slot
73 nop # : keep with cmovne
74 addq v0, 8, v0 # E :
75 xor t0, a1, t2 # E :
76
77 cmpbge zero, t0, t1 # E : bits set iff byte == zero
78 cmpbge zero, t2, t3 # E : bits set iff byte == c
79 beq t1, $loop # U : if we havnt seen a null, loop
80 nop
81
82 /* Mask out character matches after terminator */
83$eos:
84 negq t1, t4 # E : isolate first null byte match
85 and t1, t4, t4 # E :
86 subq t4, 1, t5 # E : build a mask of the bytes up to...
87 or t4, t5, t4 # E : ... and including the null
88
89 and t3, t4, t3 # E : mask out char matches after null
90 cmovne t3, t3, t8 # E : save it, if match found Latency=2, extra map slot
91 nop # : Keep with cmovne
92 nop
93
94 cmovne t3, v0, t6 # E :
95 nop # : Keep with cmovne
96 /* Locate the address of the last matched character */
97 ctlz t8, t2 # U0 : Latency=3 (0x40 for t8=0)
98 nop
99
100 cmoveq t8, 0x3f, t2 # E : Compensate for case when no match is seen
101 nop # E : hide the cmov latency (2) behind ctlz latency
102 lda t5, 0x3f($31) # E :
103 subq t5, t2, t5 # E : Normalize leading zero count
104
105 addq t6, t5, v0 # E : and add to quadword address
106 ret # L0 : Latency=3
107 nop
108 nop
109
110 .end strrchr
111 EXPORT_SYMBOL(strrchr)