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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * arch/alpha/lib/ev67-strchr.S
3 * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
4 *
5 * Return the address of a given character within a null-terminated
6 * string, or null if it is not found.
7 *
8 * Much of the information about 21264 scheduling/coding comes from:
9 * Compiler Writer's Guide for the Alpha 21264
10 * abbreviated as 'CWG' in other comments here
11 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
12 * Scheduling notation:
13 * E - either cluster
14 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
15 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
16 * Try not to change the actual algorithm if possible for consistency.
17 */
18
19#include <asm/regdef.h>
20
21 .set noreorder
22 .set noat
23
24 .align 4
25 .globl strchr
26 .ent strchr
27strchr:
28 .frame sp, 0, ra
29 .prologue 0
30
31 ldq_u t0, 0(a0) # L : load first quadword Latency=3
32 and a1, 0xff, t3 # E : 00000000000000ch
33 insbl a1, 1, t5 # U : 000000000000ch00
34 insbl a1, 7, a2 # U : ch00000000000000
35
36 insbl t3, 6, a3 # U : 00ch000000000000
37 or t5, t3, a1 # E : 000000000000chch
38 andnot a0, 7, v0 # E : align our loop pointer
39 lda t4, -1 # E : build garbage mask
40
41 mskqh t4, a0, t4 # U : only want relevant part of first quad
42 or a2, a3, a2 # E : chch000000000000
43 inswl a1, 2, t5 # E : 00000000chch0000
44 inswl a1, 4, a3 # E : 0000chch00000000
45
46 or a1, a2, a1 # E : chch00000000chch
47 or a3, t5, t5 # E : 0000chchchch0000
48 cmpbge zero, t0, t2 # E : bits set iff byte == zero
49 cmpbge zero, t4, t4 # E : bits set iff byte is garbage
50
51 /* This quad is _very_ serialized. Lots of stalling happens */
52 or t5, a1, a1 # E : chchchchchchchch
53 xor t0, a1, t1 # E : make bytes == c zero
54 cmpbge zero, t1, t3 # E : bits set iff byte == c
55 or t2, t3, t0 # E : bits set iff char match or zero match
56
57 andnot t0, t4, t0 # E : clear garbage bits
58 cttz t0, a2 # U0 : speculative (in case we get a match)
59 nop # E :
60 bne t0, $found # U :
61
62 /*
63 * Yuk. This loop is going to stall like crazy waiting for the
64 * data to be loaded. Not much can be done about it unless it's
65 * unrolled multiple times - is that safe to do in kernel space?
66 * Or would exception handling recovery code do the trick here?
67 */
68$loop: ldq t0, 8(v0) # L : Latency=3
69 addq v0, 8, v0 # E :
70 xor t0, a1, t1 # E :
71 cmpbge zero, t0, t2 # E : bits set iff byte == 0
72
73 cmpbge zero, t1, t3 # E : bits set iff byte == c
74 or t2, t3, t0 # E :
75 cttz t3, a2 # U0 : speculative (in case we get a match)
76 beq t0, $loop # U :
77
78$found: negq t0, t1 # E : clear all but least set bit
79 and t0, t1, t0 # E :
80 and t0, t3, t1 # E : bit set iff byte was the char
81 addq v0, a2, v0 # E : Add in the bit number from above
82
83 cmoveq t1, $31, v0 # E : Two mapping slots, latency = 2
84 nop
85 nop
86 ret # L0 :
87
88 .end strchr