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1da177e4 LT |
1 | /* |
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 | */ | |
00fc0e0d | 18 | #include <asm/export.h> |
1da177e4 LT |
19 | #include <asm/regdef.h> |
20 | ||
21 | .set noreorder | |
22 | .set noat | |
23 | ||
24 | .align 4 | |
25 | .globl strchr | |
26 | .ent strchr | |
27 | strchr: | |
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 | |
00fc0e0d | 89 | EXPORT_SYMBOL(strchr) |