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gerrit-public.fairphone.software / kernel / msm-4.9 / f5db4af466e2dca0fe822019812d586ca910b00c / . / arch / alpha / lib / ev67-strrchr.S
blob: 3fd8bf414c7ba4f2e89e4f37928cb752aaf83ac8 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]1/*
2 * arch/alpha/lib/ev67-strrchr.S
3 * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
4 *
5 * Finds length of a 0-terminated string. Optimized for the
6 * Alpha architecture:
7 *
8 * - memory accessed as aligned quadwords only
9 * - uses bcmpge to compare 8 bytes in parallel
10 *
11 * Much of the information about 21264 scheduling/coding comes from:
12 * Compiler Writer's Guide for the Alpha 21264
13 * abbreviated as 'CWG' in other comments here
14 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
15 * Scheduling notation:
16 * E - either cluster
17 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
18 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
19 */
20
21
22#include <asm/regdef.h>
23
24 .set noreorder
25 .set noat
26
27 .align 4
28 .ent strrchr
29 .globl strrchr
30strrchr:
31 .frame sp, 0, ra
32 .prologue 0
33
34 and a1, 0xff, t2 # E : 00000000000000ch
35 insbl a1, 1, t4 # U : 000000000000ch00
36 insbl a1, 2, t5 # U : 0000000000ch0000
37 ldq_u t0, 0(a0) # L : load first quadword Latency=3
38
39 mov zero, t6 # E : t6 is last match aligned addr
40 or t2, t4, a1 # E : 000000000000chch
41 sll t5, 8, t3 # U : 00000000ch000000
42 mov zero, t8 # E : t8 is last match byte compare mask
43
44 andnot a0, 7, v0 # E : align source addr
45 or t5, t3, t3 # E : 00000000chch0000
46 sll a1, 32, t2 # U : 0000chch00000000
47 sll a1, 48, t4 # U : chch000000000000
48
49 or t4, a1, a1 # E : chch00000000chch
50 or t2, t3, t2 # E : 0000chchchch0000
51 or a1, t2, a1 # E : chchchchchchchch
52 lda t5, -1 # E : build garbage mask
53
54 cmpbge zero, t0, t1 # E : bits set iff byte == zero
55 mskqh t5, a0, t4 # E : Complete garbage mask
56 xor t0, a1, t2 # E : make bytes == c zero
57 cmpbge zero, t4, t4 # E : bits set iff byte is garbage
58
59 cmpbge zero, t2, t3 # E : bits set iff byte == c
60 andnot t1, t4, t1 # E : clear garbage from null test
61 andnot t3, t4, t3 # E : clear garbage from char test
62 bne t1, $eos # U : did we already hit the terminator?
63
64 /* Character search main loop */
65$loop:
66 ldq t0, 8(v0) # L : load next quadword
67 cmovne t3, v0, t6 # E : save previous comparisons match
68 nop # : Latency=2, extra map slot (keep nop with cmov)
69 nop
70
71 cmovne t3, t3, t8 # E : Latency=2, extra map slot
72 nop # : keep with cmovne
73 addq v0, 8, v0 # E :
74 xor t0, a1, t2 # E :
75
76 cmpbge zero, t0, t1 # E : bits set iff byte == zero
77 cmpbge zero, t2, t3 # E : bits set iff byte == c
78 beq t1, $loop # U : if we havnt seen a null, loop
79 nop
80
81 /* Mask out character matches after terminator */
82$eos:
83 negq t1, t4 # E : isolate first null byte match
84 and t1, t4, t4 # E :
85 subq t4, 1, t5 # E : build a mask of the bytes upto...
86 or t4, t5, t4 # E : ... and including the null
87
88 and t3, t4, t3 # E : mask out char matches after null
89 cmovne t3, t3, t8 # E : save it, if match found Latency=2, extra map slot
90 nop # : Keep with cmovne
91 nop
92
93 cmovne t3, v0, t6 # E :
94 nop # : Keep with cmovne
95 /* Locate the address of the last matched character */
96 ctlz t8, t2 # U0 : Latency=3 (0x40 for t8=0)
97 nop
98
99 cmoveq t8, 0x3f, t2 # E : Compensate for case when no match is seen
100 nop # E : hide the cmov latency (2) behind ctlz latency
101 lda t5, 0x3f($31) # E :
102 subq t5, t2, t5 # E : Normalize leading zero count
103
104 addq t6, t5, v0 # E : and add to quadword address
105 ret # L0 : Latency=3
106 nop
107 nop
108
109 .end strrchr