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78df0fcb AJ |
1 | /* strcat(dest, src) -- Append SRC on the end of DEST. |
2 | Optimized for x86-64. | |
f7a9f785 | 3 | Copyright (C) 2002-2016 Free Software Foundation, Inc. |
78df0fcb AJ |
4 | This file is part of the GNU C Library. |
5 | Contributed by Andreas Jaeger <aj@suse.de>, 2002. | |
6 | ||
7 | The GNU C Library is free software; you can redistribute it and/or | |
8 | modify it under the terms of the GNU Lesser General Public | |
9 | License as published by the Free Software Foundation; either | |
10 | version 2.1 of the License, or (at your option) any later version. | |
11 | ||
12 | The GNU C Library is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | Lesser General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 PE |
18 | License along with the GNU C Library; if not, see |
19 | <http://www.gnu.org/licenses/>. */ | |
78df0fcb AJ |
20 | |
21 | #include <sysdep.h> | |
22 | #include "asm-syntax.h" | |
78df0fcb | 23 | |
37bb363f | 24 | /* Will be removed when new strcpy implementation gets merged. */ |
78df0fcb AJ |
25 | |
26 | .text | |
29691210 | 27 | ENTRY (strcat) |
78df0fcb AJ |
28 | movq %rdi, %rcx /* Dest. register. */ |
29 | andl $7, %ecx /* mask alignment bits */ | |
30 | movq %rdi, %rax /* Duplicate destination pointer. */ | |
31 | movq $0xfefefefefefefeff,%r8 | |
32 | ||
33 | /* First step: Find end of destination. */ | |
34 | jz 4f /* aligned => start loop */ | |
35 | ||
36 | neg %ecx /* We need to align to 8 bytes. */ | |
37 | addl $8,%ecx | |
38 | /* Search the first bytes directly. */ | |
39 | 0: cmpb $0x0,(%rax) /* is byte NUL? */ | |
40 | je 2f /* yes => start copy */ | |
41 | incq %rax /* increment pointer */ | |
42 | decl %ecx | |
43 | jnz 0b | |
44 | ||
45 | ||
46 | ||
47 | /* Now the source is aligned. Scan for NUL byte. */ | |
48 | .p2align 4 | |
49 | 4: | |
50 | /* First unroll. */ | |
51 | movq (%rax), %rcx /* get double word (= 8 bytes) in question */ | |
52 | addq $8,%rax /* adjust pointer for next word */ | |
53 | movq %r8, %rdx /* magic value */ | |
54 | addq %rcx, %rdx /* add the magic value to the word. We get | |
55 | carry bits reported for each byte which | |
56 | is *not* 0 */ | |
57 | jnc 3f /* highest byte is NUL => return pointer */ | |
58 | xorq %rcx, %rdx /* (word+magic)^word */ | |
59 | orq %r8, %rdx /* set all non-carry bits */ | |
60 | incq %rdx /* add 1: if one carry bit was *not* set | |
61 | the addition will not result in 0. */ | |
62 | jnz 3f /* found NUL => return pointer */ | |
63 | ||
64 | /* Second unroll. */ | |
65 | movq (%rax), %rcx /* get double word (= 8 bytes) in question */ | |
66 | addq $8,%rax /* adjust pointer for next word */ | |
67 | movq %r8, %rdx /* magic value */ | |
68 | addq %rcx, %rdx /* add the magic value to the word. We get | |
69 | carry bits reported for each byte which | |
70 | is *not* 0 */ | |
71 | jnc 3f /* highest byte is NUL => return pointer */ | |
72 | xorq %rcx, %rdx /* (word+magic)^word */ | |
73 | orq %r8, %rdx /* set all non-carry bits */ | |
74 | incq %rdx /* add 1: if one carry bit was *not* set | |
75 | the addition will not result in 0. */ | |
76 | jnz 3f /* found NUL => return pointer */ | |
77 | ||
78 | /* Third unroll. */ | |
79 | movq (%rax), %rcx /* get double word (= 8 bytes) in question */ | |
80 | addq $8,%rax /* adjust pointer for next word */ | |
81 | movq %r8, %rdx /* magic value */ | |
82 | addq %rcx, %rdx /* add the magic value to the word. We get | |
83 | carry bits reported for each byte which | |
84 | is *not* 0 */ | |
85 | jnc 3f /* highest byte is NUL => return pointer */ | |
86 | xorq %rcx, %rdx /* (word+magic)^word */ | |
87 | orq %r8, %rdx /* set all non-carry bits */ | |
88 | incq %rdx /* add 1: if one carry bit was *not* set | |
89 | the addition will not result in 0. */ | |
90 | jnz 3f /* found NUL => return pointer */ | |
91 | ||
92 | /* Fourth unroll. */ | |
93 | movq (%rax), %rcx /* get double word (= 8 bytes) in question */ | |
94 | addq $8,%rax /* adjust pointer for next word */ | |
95 | movq %r8, %rdx /* magic value */ | |
96 | addq %rcx, %rdx /* add the magic value to the word. We get | |
97 | carry bits reported for each byte which | |
98 | is *not* 0 */ | |
99 | jnc 3f /* highest byte is NUL => return pointer */ | |
100 | xorq %rcx, %rdx /* (word+magic)^word */ | |
101 | orq %r8, %rdx /* set all non-carry bits */ | |
102 | incq %rdx /* add 1: if one carry bit was *not* set | |
103 | the addition will not result in 0. */ | |
104 | jz 4b /* no NUL found => continue loop */ | |
105 | ||
106 | .p2align 4 /* Align, it's a jump target. */ | |
107 | 3: subq $8,%rax /* correct pointer increment. */ | |
108 | ||
109 | testb %cl, %cl /* is first byte NUL? */ | |
110 | jz 2f /* yes => return */ | |
111 | incq %rax /* increment pointer */ | |
112 | ||
113 | testb %ch, %ch /* is second byte NUL? */ | |
114 | jz 2f /* yes => return */ | |
115 | incq %rax /* increment pointer */ | |
116 | ||
117 | testl $0x00ff0000, %ecx /* is third byte NUL? */ | |
118 | jz 2f /* yes => return pointer */ | |
119 | incq %rax /* increment pointer */ | |
120 | ||
121 | testl $0xff000000, %ecx /* is fourth byte NUL? */ | |
122 | jz 2f /* yes => return pointer */ | |
123 | incq %rax /* increment pointer */ | |
124 | ||
125 | shrq $32, %rcx /* look at other half. */ | |
126 | ||
127 | testb %cl, %cl /* is first byte NUL? */ | |
128 | jz 2f /* yes => return */ | |
129 | incq %rax /* increment pointer */ | |
130 | ||
131 | testb %ch, %ch /* is second byte NUL? */ | |
132 | jz 2f /* yes => return */ | |
133 | incq %rax /* increment pointer */ | |
134 | ||
135 | testl $0xff0000, %ecx /* is third byte NUL? */ | |
136 | jz 2f /* yes => return pointer */ | |
137 | incq %rax /* increment pointer */ | |
138 | ||
139 | 2: | |
140 | /* Second step: Copy source to destination. */ | |
141 | ||
7288b24f | 142 | movq %rsi, %rcx /* duplicate */ |
78df0fcb AJ |
143 | andl $7,%ecx /* mask alignment bits */ |
144 | movq %rax, %rdx /* move around */ | |
145 | jz 22f /* aligned => start loop */ | |
146 | ||
7288b24f AJ |
147 | neg %ecx /* align to 8 bytes. */ |
148 | addl $8, %ecx | |
78df0fcb AJ |
149 | /* Align the source pointer. */ |
150 | 21: | |
151 | movb (%rsi), %al /* Fetch a byte */ | |
152 | testb %al, %al /* Is it NUL? */ | |
153 | movb %al, (%rdx) /* Store it */ | |
154 | jz 24f /* If it was NUL, done! */ | |
155 | incq %rsi | |
156 | incq %rdx | |
157 | decl %ecx | |
158 | jnz 21b | |
159 | ||
160 | /* Now the sources is aligned. Unfortunatly we cannot force | |
161 | to have both source and destination aligned, so ignore the | |
162 | alignment of the destination. */ | |
163 | .p2align 4 | |
164 | 22: | |
165 | /* 1st unroll. */ | |
166 | movq (%rsi), %rax /* Read double word (8 bytes). */ | |
167 | addq $8, %rsi /* Adjust pointer for next word. */ | |
168 | movq %rax, %r9 /* Save a copy for NUL finding. */ | |
169 | addq %r8, %r9 /* add the magic value to the word. We get | |
170 | carry bits reported for each byte which | |
171 | is *not* 0 */ | |
172 | jnc 23f /* highest byte is NUL => return pointer */ | |
173 | xorq %rax, %r9 /* (word+magic)^word */ | |
174 | orq %r8, %r9 /* set all non-carry bits */ | |
175 | incq %r9 /* add 1: if one carry bit was *not* set | |
176 | the addition will not result in 0. */ | |
177 | ||
178 | jnz 23f /* found NUL => return pointer */ | |
179 | ||
180 | movq %rax, (%rdx) /* Write value to destination. */ | |
181 | addq $8, %rdx /* Adjust pointer. */ | |
182 | ||
183 | /* 2nd unroll. */ | |
184 | movq (%rsi), %rax /* Read double word (8 bytes). */ | |
185 | addq $8, %rsi /* Adjust pointer for next word. */ | |
186 | movq %rax, %r9 /* Save a copy for NUL finding. */ | |
187 | addq %r8, %r9 /* add the magic value to the word. We get | |
188 | carry bits reported for each byte which | |
189 | is *not* 0 */ | |
190 | jnc 23f /* highest byte is NUL => return pointer */ | |
191 | xorq %rax, %r9 /* (word+magic)^word */ | |
192 | orq %r8, %r9 /* set all non-carry bits */ | |
193 | incq %r9 /* add 1: if one carry bit was *not* set | |
194 | the addition will not result in 0. */ | |
195 | ||
196 | jnz 23f /* found NUL => return pointer */ | |
197 | ||
198 | movq %rax, (%rdx) /* Write value to destination. */ | |
199 | addq $8, %rdx /* Adjust pointer. */ | |
200 | ||
201 | /* 3rd unroll. */ | |
202 | movq (%rsi), %rax /* Read double word (8 bytes). */ | |
203 | addq $8, %rsi /* Adjust pointer for next word. */ | |
204 | movq %rax, %r9 /* Save a copy for NUL finding. */ | |
205 | addq %r8, %r9 /* add the magic value to the word. We get | |
206 | carry bits reported for each byte which | |
207 | is *not* 0 */ | |
208 | jnc 23f /* highest byte is NUL => return pointer */ | |
209 | xorq %rax, %r9 /* (word+magic)^word */ | |
210 | orq %r8, %r9 /* set all non-carry bits */ | |
211 | incq %r9 /* add 1: if one carry bit was *not* set | |
212 | the addition will not result in 0. */ | |
213 | ||
214 | jnz 23f /* found NUL => return pointer */ | |
215 | ||
216 | movq %rax, (%rdx) /* Write value to destination. */ | |
217 | addq $8, %rdx /* Adjust pointer. */ | |
218 | ||
219 | /* 4th unroll. */ | |
220 | movq (%rsi), %rax /* Read double word (8 bytes). */ | |
221 | addq $8, %rsi /* Adjust pointer for next word. */ | |
222 | movq %rax, %r9 /* Save a copy for NUL finding. */ | |
223 | addq %r8, %r9 /* add the magic value to the word. We get | |
224 | carry bits reported for each byte which | |
225 | is *not* 0 */ | |
226 | jnc 23f /* highest byte is NUL => return pointer */ | |
227 | xorq %rax, %r9 /* (word+magic)^word */ | |
228 | orq %r8, %r9 /* set all non-carry bits */ | |
229 | incq %r9 /* add 1: if one carry bit was *not* set | |
230 | the addition will not result in 0. */ | |
231 | ||
232 | jnz 23f /* found NUL => return pointer */ | |
233 | ||
234 | movq %rax, (%rdx) /* Write value to destination. */ | |
235 | addq $8, %rdx /* Adjust pointer. */ | |
236 | jmp 22b /* Next iteration. */ | |
237 | ||
238 | /* Do the last few bytes. %rax contains the value to write. | |
239 | The loop is unrolled twice. */ | |
240 | .p2align 4 | |
241 | 23: | |
242 | movb %al, (%rdx) /* 1st byte. */ | |
243 | testb %al, %al /* Is it NUL. */ | |
244 | jz 24f /* yes, finish. */ | |
245 | incq %rdx /* Increment destination. */ | |
246 | movb %ah, (%rdx) /* 2nd byte. */ | |
247 | testb %ah, %ah /* Is it NUL?. */ | |
248 | jz 24f /* yes, finish. */ | |
249 | incq %rdx /* Increment destination. */ | |
250 | shrq $16, %rax /* Shift... */ | |
251 | jmp 23b /* and look at next two bytes in %rax. */ | |
252 | ||
253 | ||
254 | 24: | |
255 | movq %rdi, %rax /* Source is return value. */ | |
256 | retq | |
29691210 | 257 | END (strcat) |
85dd1003 | 258 | libc_hidden_builtin_def (strcat) |