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
| /* SPDX-License-Identifier: GPL-2.0 */
| /*
| * arch/alpha/lib/strrchr.S
| * Contributed by Richard Henderson (rth@tamu.edu)
| *
| * Return the address of the last occurrence of a given character
| * within a null-terminated string, or null if it is not found.
| */
| #include <asm/export.h>
| #include <asm/regdef.h>
|
| .set noreorder
| .set noat
|
| .align 3
| .ent strrchr
| .globl strrchr
| strrchr:
| .frame sp, 0, ra
| .prologue 0
|
| zapnot a1, 1, a1 # e0 : zero extend our test character
| mov zero, t6 # .. e1 : t6 is last match aligned addr
| sll a1, 8, t5 # e0 : replicate our test character
| mov zero, t8 # .. e1 : t8 is last match byte compare mask
| or t5, a1, a1 # e0 :
| ldq_u t0, 0(a0) # .. e1 : load first quadword
| sll a1, 16, t5 # e0 :
| andnot a0, 7, v0 # .. e1 : align source addr
| or t5, a1, a1 # e0 :
| lda t4, -1 # .. e1 : build garbage mask
| sll a1, 32, t5 # e0 :
| cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero
| mskqh t4, a0, t4 # e0 :
| or t5, a1, a1 # .. e1 : character replication complete
| xor t0, a1, t2 # e0 : make bytes == c zero
| cmpbge zero, t4, t4 # .. e1 : bits set iff byte is garbage
| cmpbge zero, t2, t3 # e0 : bits set iff byte == c
| andnot t1, t4, t1 # .. e1 : clear garbage from null test
| andnot t3, t4, t3 # e0 : clear garbage from char test
| bne t1, $eos # .. e1 : did we already hit the terminator?
|
| /* Character search main loop */
| $loop:
| ldq t0, 8(v0) # e0 : load next quadword
| cmovne t3, v0, t6 # .. e1 : save previous comparisons match
| cmovne t3, t3, t8 # e0 :
| addq v0, 8, v0 # .. e1 :
| xor t0, a1, t2 # e0 :
| cmpbge zero, t0, t1 # .. e1 : bits set iff byte == zero
| cmpbge zero, t2, t3 # e0 : bits set iff byte == c
| beq t1, $loop # .. e1 : if we havnt seen a null, loop
|
| /* Mask out character matches after terminator */
| $eos:
| negq t1, t4 # e0 : isolate first null byte match
| and t1, t4, t4 # e1 :
| subq t4, 1, t5 # e0 : build a mask of the bytes up to...
| or t4, t5, t4 # e1 : ... and including the null
|
| and t3, t4, t3 # e0 : mask out char matches after null
| cmovne t3, t3, t8 # .. e1 : save it, if match found
| cmovne t3, v0, t6 # e0 :
|
| /* Locate the address of the last matched character */
|
| /* Retain the early exit for the ev4 -- the ev5 mispredict penalty
| is 5 cycles -- the same as just falling through. */
| beq t8, $retnull # .. e1 :
|
| and t8, 0xf0, t2 # e0 : binary search for the high bit set
| cmovne t2, t2, t8 # .. e1 (zdb)
| cmovne t2, 4, t2 # e0 :
| and t8, 0xcc, t1 # .. e1 :
| cmovne t1, t1, t8 # e0 :
| cmovne t1, 2, t1 # .. e1 :
| and t8, 0xaa, t0 # e0 :
| cmovne t0, 1, t0 # .. e1 (zdb)
| addq t2, t1, t1 # e0 :
| addq t6, t0, v0 # .. e1 : add our aligned base ptr to the mix
| addq v0, t1, v0 # e0 :
| ret # .. e1 :
|
| $retnull:
| mov zero, v0 # e0 :
| ret # .. e1 :
|
| .end strrchr
| EXPORT_SYMBOL(strrchr)
|
|
