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1/* Copyright (C) 1996-2019 Free Software Foundation, Inc.
2 Contributed by Richard Henderson (rth@tamu.edu)
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library. If not, see
17 <http://www.gnu.org/licenses/>. */
18
19/* Bytewise compare two null-terminated strings. */
20
21#include <sysdep.h>
22
23 .set noat
24 .set noreorder
25
26 .text
27
28ENTRY(strcmp)
29#ifdef PROF
30 ldgp gp, 0(pv)
31 lda AT, _mcount
32 jmp AT, (AT), _mcount
33 .prologue 1
34#else
35 .prologue 0
36#endif
37
38 ldq_u t0, 0(a0) # e0 : give cache time to catch up
39 xor a0, a1, t2 # .. e1 : are s1 and s2 co-aligned?
40 ldq_u t1, 0(a1) # e0 :
41 and t2, 7, t2 # .. e1 :
42 lda t3, -1 # e0 :
43 bne t2, $unaligned # .. e1 :
44
45 /* On entry to this basic block:
46 t0 == the first destination word for masking back in
47 t1 == the first source word.
48 t3 == -1. */
49
50$aligned:
51 mskqh t3, a0, t3 # e0 :
52 nop # .. e1 :
53 ornot t1, t3, t1 # e0 :
54 ornot t0, t3, t0 # .. e1 :
55 cmpbge zero, t1, t7 # e0 : bits set iff null found
56 bne t7, $eos # e1 (zdb)
57
58 /* Aligned compare main loop.
59 On entry to this basic block:
60 t0 == an s1 word.
61 t1 == an s2 word not containing a null. */
62
63$a_loop:
64 xor t0, t1, t2 # e0 :
65 bne t2, $wordcmp # .. e1 (zdb)
66 ldq_u t1, 8(a1) # e0 :
67 ldq_u t0, 8(a0) # .. e1 :
68 addq a1, 8, a1 # e0 :
69 addq a0, 8, a0 # .. e1 :
70 cmpbge zero, t1, t7 # e0 :
71 beq t7, $a_loop # .. e1 (zdb)
72 br $eos # e1 :
73
74 /* The two strings are not co-aligned. Align s1 and cope. */
75
76$unaligned:
77 and a0, 7, t4 # e0 : find s1 misalignment
78 and a1, 7, t5 # .. e1 : find s2 misalignment
79 subq a1, t4, a1 # e0 :
80
81 /* If s2 misalignment is larger than s2 misalignment, we need
82 extra startup checks to avoid SEGV. */
83
84 cmplt t4, t5, t8 # .. e1 :
85 beq t8, $u_head # e1 :
86
87 mskqh t3, t5, t3 # e0 :
88 ornot t1, t3, t3 # e0 :
89 cmpbge zero, t3, t7 # e1 : is there a zero?
90 beq t7, $u_head # e1 :
91
92 /* We've found a zero in the first partial word of s2. Align
93 our current s1 and s2 words and compare what we've got. */
94
95 extql t1, t5, t1 # e0 :
96 extql t0, a0, t0 # e0 :
97 cmpbge zero, t1, t7 # .. e1 : find that zero again
98 br $eos # e1 : and finish up
99
100 .align 3
101$u_head:
102 /* We know just enough now to be able to assemble the first
103 full word of s2. We can still find a zero at the end of it.
104
105 On entry to this basic block:
106 t0 == first word of s1
107 t1 == first partial word of s2. */
108
109 ldq_u t2, 8(a1) # e0 : load second partial s2 word
110 lda t3, -1 # .. e1 : create leading garbage mask
111 extql t1, a1, t1 # e0 : create first s2 word
112 mskqh t3, a0, t3 # e0 :
113 extqh t2, a1, t4 # e0 :
114 ornot t0, t3, t0 # .. e1 : kill s1 garbage
115 or t1, t4, t1 # e0 : s2 word now complete
116 cmpbge zero, t0, t7 # .. e1 : find zero in first s1 word
117 ornot t1, t3, t1 # e0 : kill s2 garbage
118 lda t3, -1 # .. e1 :
119 mskql t3, a1, t3 # e0 : mask for s2[1] bits we have seen
120 bne t7, $eos # .. e1 :
121 xor t0, t1, t4 # e0 : compare aligned words
122 bne t4, $wordcmp # .. e1 (zdb)
123 or t2, t3, t3 # e0 :
124 cmpbge zero, t3, t7 # e1 :
125 bne t7, $u_final # e1 :
126
127 /* Unaligned copy main loop. In order to avoid reading too much,
128 the loop is structured to detect zeros in aligned words from s2.
129 This has, unfortunately, effectively pulled half of a loop
130 iteration out into the head and half into the tail, but it does
131 prevent nastiness from accumulating in the very thing we want
132 to run as fast as possible.
133
134 On entry to this basic block:
135 t2 == the unshifted low-bits from the next s2 word. */
136
137 .align 3
138$u_loop:
139 extql t2, a1, t3 # e0 :
140 ldq_u t2, 16(a1) # .. e1 : load next s2 high bits
141 ldq_u t0, 8(a0) # e0 : load next s1 word
142 addq a1, 8, a1 # .. e1 :
143 addq a0, 8, a0 # e0 :
144 nop # .. e1 :
145 extqh t2, a1, t1 # e0 :
146 cmpbge zero, t0, t7 # .. e1 : find zero in current s1 word
147 or t1, t3, t1 # e0 :
148 bne t7, $eos # .. e1 :
149 xor t0, t1, t4 # e0 : compare the words
150 bne t4, $wordcmp # .. e1 (zdb)
151 cmpbge zero, t2, t4 # e0 : find zero in next low bits
152 beq t4, $u_loop # .. e1 (zdb)
153
154 /* We've found a zero in the low bits of the last s2 word. Get
155 the next s1 word and align them. */
156$u_final:
157 ldq_u t0, 8(a0) # e1 :
158 extql t2, a1, t1 # .. e0 :
159 cmpbge zero, t1, t7 # e0 :
160
161 /* We've found a zero somewhere in a word we just read.
162 On entry to this basic block:
163 t0 == s1 word
164 t1 == s2 word
165 t7 == cmpbge mask containing the zero. */
166
167 .align 3
168$eos:
169 negq t7, t6 # e0 : create bytemask of valid data
170 and t6, t7, t8 # e1 :
171 subq t8, 1, t6 # e0 :
172 or t6, t8, t7 # e1 :
173 zapnot t0, t7, t0 # e0 : kill the garbage
174 zapnot t1, t7, t1 # .. e1 :
175 xor t0, t1, v0 # e0 : and compare
176 beq v0, $done # .. e1 :
177
178 /* Here we have two differing co-aligned words in t0 & t1.
179 Bytewise compare them and return (t0 > t1 ? 1 : -1). */
180$wordcmp:
181 cmpbge t0, t1, t2 # e0 : comparison yields bit mask of ge
182 cmpbge t1, t0, t3 # .. e1 :
183 xor t2, t3, t0 # e0 : bits set iff t0/t1 bytes differ
184 negq t0, t1 # e1 : clear all but least bit
185 and t0, t1, t0 # e0 :
186 lda v0, -1 # .. e1 :
187 and t0, t2, t1 # e0 : was bit set in t0 > t1?
188 cmovne t1, 1, v0 # .. e1 (zdb)
189
190$done:
191 ret # e1 :
192
193 END(strcmp)
194libc_hidden_builtin_def (strcmp)
195

Warning: That file was not part of the compilation database. It may have many parsing errors.