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dff8da6b | 1 | /* Copyright (C) 1996-2024 Free Software Foundation, Inc. |
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2 | This file is part of the GNU C Library. |
3 | ||
4 | The GNU C Library is free software; you can redistribute it and/or | |
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5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either | |
7 | version 2.1 of the License, or (at your option) any later version. | |
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8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, | |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
3214b89b | 12 | Lesser General Public License for more details. |
60c74cf0 | 13 | |
3214b89b | 14 | You should have received a copy of the GNU Lesser General Public |
ab84e3ff | 15 | License along with the GNU C Library. If not, see |
5a82c748 | 16 | <https://www.gnu.org/licenses/>. */ |
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17 | |
18 | /* Bytewise compare two null-terminated strings. */ | |
19 | ||
20 | #include <sysdep.h> | |
21 | ||
22 | .set noat | |
23 | .set noreorder | |
24 | ||
25 | .text | |
26 | ||
27 | ENTRY(strcmp) | |
28 | #ifdef PROF | |
29 | ldgp gp, 0(pv) | |
30 | lda AT, _mcount | |
31 | jmp AT, (AT), _mcount | |
32 | .prologue 1 | |
33 | #else | |
34 | .prologue 0 | |
35 | #endif | |
36 | ||
37 | ldq_u t0, 0(a0) # e0 : give cache time to catch up | |
38 | xor a0, a1, t2 # .. e1 : are s1 and s2 co-aligned? | |
39 | ldq_u t1, 0(a1) # e0 : | |
40 | and t2, 7, t2 # .. e1 : | |
41 | lda t3, -1 # e0 : | |
42 | bne t2, $unaligned # .. e1 : | |
43 | ||
44 | /* On entry to this basic block: | |
45 | t0 == the first destination word for masking back in | |
46 | t1 == the first source word. | |
47 | t3 == -1. */ | |
48 | ||
49 | $aligned: | |
50 | mskqh t3, a0, t3 # e0 : | |
51 | nop # .. e1 : | |
52 | ornot t1, t3, t1 # e0 : | |
53 | ornot t0, t3, t0 # .. e1 : | |
54 | cmpbge zero, t1, t7 # e0 : bits set iff null found | |
55 | bne t7, $eos # e1 (zdb) | |
56 | ||
57 | /* Aligned compare main loop. | |
58 | On entry to this basic block: | |
59 | t0 == an s1 word. | |
60 | t1 == an s2 word not containing a null. */ | |
61 | ||
62 | $a_loop: | |
63 | xor t0, t1, t2 # e0 : | |
64 | bne t2, $wordcmp # .. e1 (zdb) | |
65 | ldq_u t1, 8(a1) # e0 : | |
66 | ldq_u t0, 8(a0) # .. e1 : | |
67 | addq a1, 8, a1 # e0 : | |
68 | addq a0, 8, a0 # .. e1 : | |
69 | cmpbge zero, t1, t7 # e0 : | |
70 | beq t7, $a_loop # .. e1 (zdb) | |
71 | br $eos # e1 : | |
72 | ||
73 | /* The two strings are not co-aligned. Align s1 and cope. */ | |
74 | ||
75 | $unaligned: | |
76 | and a0, 7, t4 # e0 : find s1 misalignment | |
77 | and a1, 7, t5 # .. e1 : find s2 misalignment | |
78 | subq a1, t4, a1 # e0 : | |
79 | ||
80 | /* If s2 misalignment is larger than s2 misalignment, we need | |
81 | extra startup checks to avoid SEGV. */ | |
82 | ||
83 | cmplt t4, t5, t8 # .. e1 : | |
84 | beq t8, $u_head # e1 : | |
85 | ||
86 | mskqh t3, t5, t3 # e0 : | |
87 | ornot t1, t3, t3 # e0 : | |
88 | cmpbge zero, t3, t7 # e1 : is there a zero? | |
89 | beq t7, $u_head # e1 : | |
90 | ||
91 | /* We've found a zero in the first partial word of s2. Align | |
92 | our current s1 and s2 words and compare what we've got. */ | |
93 | ||
94 | extql t1, t5, t1 # e0 : | |
95 | extql t0, a0, t0 # e0 : | |
96 | cmpbge zero, t1, t7 # .. e1 : find that zero again | |
97 | br $eos # e1 : and finish up | |
98 | ||
99 | .align 3 | |
100 | $u_head: | |
101 | /* We know just enough now to be able to assemble the first | |
102 | full word of s2. We can still find a zero at the end of it. | |
103 | ||
104 | On entry to this basic block: | |
105 | t0 == first word of s1 | |
106 | t1 == first partial word of s2. */ | |
107 | ||
108 | ldq_u t2, 8(a1) # e0 : load second partial s2 word | |
109 | lda t3, -1 # .. e1 : create leading garbage mask | |
110 | extql t1, a1, t1 # e0 : create first s2 word | |
111 | mskqh t3, a0, t3 # e0 : | |
112 | extqh t2, a1, t4 # e0 : | |
113 | ornot t0, t3, t0 # .. e1 : kill s1 garbage | |
114 | or t1, t4, t1 # e0 : s2 word now complete | |
115 | cmpbge zero, t0, t7 # .. e1 : find zero in first s1 word | |
116 | ornot t1, t3, t1 # e0 : kill s2 garbage | |
117 | lda t3, -1 # .. e1 : | |
118 | mskql t3, a1, t3 # e0 : mask for s2[1] bits we have seen | |
119 | bne t7, $eos # .. e1 : | |
120 | xor t0, t1, t4 # e0 : compare aligned words | |
121 | bne t4, $wordcmp # .. e1 (zdb) | |
122 | or t2, t3, t3 # e0 : | |
123 | cmpbge zero, t3, t7 # e1 : | |
124 | bne t7, $u_final # e1 : | |
125 | ||
126 | /* Unaligned copy main loop. In order to avoid reading too much, | |
127 | the loop is structured to detect zeros in aligned words from s2. | |
128 | This has, unfortunately, effectively pulled half of a loop | |
129 | iteration out into the head and half into the tail, but it does | |
130 | prevent nastiness from accumulating in the very thing we want | |
131 | to run as fast as possible. | |
132 | ||
133 | On entry to this basic block: | |
134 | t2 == the unshifted low-bits from the next s2 word. */ | |
135 | ||
136 | .align 3 | |
137 | $u_loop: | |
138 | extql t2, a1, t3 # e0 : | |
139 | ldq_u t2, 16(a1) # .. e1 : load next s2 high bits | |
140 | ldq_u t0, 8(a0) # e0 : load next s1 word | |
141 | addq a1, 8, a1 # .. e1 : | |
142 | addq a0, 8, a0 # e0 : | |
143 | nop # .. e1 : | |
144 | extqh t2, a1, t1 # e0 : | |
145 | cmpbge zero, t0, t7 # .. e1 : find zero in current s1 word | |
146 | or t1, t3, t1 # e0 : | |
147 | bne t7, $eos # .. e1 : | |
148 | xor t0, t1, t4 # e0 : compare the words | |
149 | bne t4, $wordcmp # .. e1 (zdb) | |
150 | cmpbge zero, t2, t4 # e0 : find zero in next low bits | |
151 | beq t4, $u_loop # .. e1 (zdb) | |
152 | ||
153 | /* We've found a zero in the low bits of the last s2 word. Get | |
154 | the next s1 word and align them. */ | |
155 | $u_final: | |
156 | ldq_u t0, 8(a0) # e1 : | |
157 | extql t2, a1, t1 # .. e0 : | |
158 | cmpbge zero, t1, t7 # e0 : | |
159 | ||
160 | /* We've found a zero somewhere in a word we just read. | |
161 | On entry to this basic block: | |
162 | t0 == s1 word | |
163 | t1 == s2 word | |
164 | t7 == cmpbge mask containing the zero. */ | |
165 | ||
166 | .align 3 | |
167 | $eos: | |
168 | negq t7, t6 # e0 : create bytemask of valid data | |
169 | and t6, t7, t8 # e1 : | |
170 | subq t8, 1, t6 # e0 : | |
171 | or t6, t8, t7 # e1 : | |
172 | zapnot t0, t7, t0 # e0 : kill the garbage | |
173 | zapnot t1, t7, t1 # .. e1 : | |
174 | xor t0, t1, v0 # e0 : and compare | |
175 | beq v0, $done # .. e1 : | |
176 | ||
177 | /* Here we have two differing co-aligned words in t0 & t1. | |
db31c863 | 178 | Bytewise compare them and return (t0 > t1 ? 1 : -1). */ |
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179 | $wordcmp: |
180 | cmpbge t0, t1, t2 # e0 : comparison yields bit mask of ge | |
181 | cmpbge t1, t0, t3 # .. e1 : | |
182 | xor t2, t3, t0 # e0 : bits set iff t0/t1 bytes differ | |
183 | negq t0, t1 # e1 : clear all but least bit | |
184 | and t0, t1, t0 # e0 : | |
185 | lda v0, -1 # .. e1 : | |
186 | and t0, t2, t1 # e0 : was bit set in t0 > t1? | |
187 | cmovne t1, 1, v0 # .. e1 (zdb) | |
188 | ||
189 | $done: | |
190 | ret # e1 : | |
191 | ||
192 | END(strcmp) | |
79b7c863 | 193 | libc_hidden_builtin_def (strcmp) |