1/* Optimized strcpy/stpcpy implementation for PowerPC64/POWER8.
2 Copyright (C) 2015-2024 Free Software Foundation, Inc.
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 <https://www.gnu.org/licenses/>. */
18
19#include <sysdep.h>
20
21#ifdef USE_AS_STPCPY
22# ifndef STPCPY
23# define FUNC_NAME __stpcpy
24# else
25# define FUNC_NAME STPCPY
26# endif
27#else
28# ifndef STRCPY
29# define FUNC_NAME strcpy
30# else
31# define FUNC_NAME STRCPY
32# endif
33#endif /* !USE_AS_STPCPY */
34
35/* Implements the function
36
37 char * [r3] strcpy (char *dest [r3], const char *src [r4])
38
39 or
40
41 char * [r3] stpcpy (char *dest [r3], const char *src [r4])
42
43 if USE_AS_STPCPY is defined.
44
45 The implementation uses unaligned doubleword access to avoid specialized
46 code paths depending of data alignment. Although recent powerpc64 uses
47 64K as default, the page cross handling assumes minimum page size of
48 4k. */
49
50 .machine power8
51ENTRY_TOCLESS (FUNC_NAME, 4)
52 li r0,0 /* Doubleword with null chars to use
53 with cmpb. */
54
55 /* Check if the [src]+15 will cross a 4K page by checking if the bit
56 indicating the page size changes. Basically:
57
58 uint64_t srcin = (uint64_t)src;
59 uint64_t ob = srcin & 4096UL;
60 uint64_t nb = (srcin+15UL) & 4096UL;
61 if (ob ^ nb)
62 goto pagecross; */
63
64 addi r9,r4,15
65 xor r9,r9,r4
66 rlwinm. r9,r9,0,19,19
67 bne L(pagecross)
68
69 /* For short string (less than 16 bytes), just calculate its size as
70 strlen and issues a memcpy if null is found. */
71 mr r7,r4
72 ld r12,0(r7) /* Load doubleword from memory. */
73 cmpb r10,r12,r0 /* Check for null bytes in DWORD1. */
74 cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */
75 bne cr7,L(done)
76
77 ldu r8,8(r7)
78 cmpb r10,r8,r0
79 cmpdi cr7,r10,0
80 bne cr7,L(done)
81
82 b L(loop_before)
83
84 .align 4
85L(pagecross):
86 clrrdi r7,r4,3 /* Align the address to doubleword boundary. */
87 rlwinm r6,r4,3,26,28 /* Calculate padding. */
88 li r5,-1 /* MASK = 0xffffffffffffffff. */
89 ld r12,0(r7) /* Load doubleword from memory. */
90#ifdef __LITTLE_ENDIAN__
91 sld r5,r5,r6
92#else
93 srd r5,r5,r6 /* MASK = MASK >> padding. */
94#endif
95 orc r9,r12,r5 /* Mask bits that are not part of the string. */
96 cmpb r10,r9,r0 /* Check for null bytes in DWORD1. */
97 cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */
98 bne cr7,L(done)
99
100 ldu r6,8(r7)
101 cmpb r10,r6,r0
102 cmpdi cr7,r10,0
103 bne cr7,L(done)
104
105 ld r12,0(r7)
106 cmpb r10,r12,r0
107 cmpdi cr7,r10,0
108 bne cr7,L(done)
109
110 ldu r6,8(r7)
111 cmpb r10,r6,r0
112 cmpdi cr7,r10,0
113 bne cr7,L(done)
114
115 /* We checked for 24 - x bytes, with x being the source alignment
116 (0 <= x <= 16), and no zero has been found. Start the loop
117 copy with doubleword aligned address. */
118 mr r7,r4
119 ld r12, 0(r7)
120 ldu r8, 8(r7)
121
122L(loop_before):
123 /* Save the two doublewords read from source and align the source
124 to 16 bytes for the loop. */
125 mr r11,r3
126 std r12,0(r11)
127 std r8,8(r11)
128 addi r11,r11,16
129 rldicl r9,r4,0,60
130 subf r7,r9,r7
131 subf r11,r9,r11
132 /* Source is adjusted to 16B alignment and destination r11 is
133 also moved based on that adjustment. Now check if r11 is
134 also 16B aligned to move to vectorized loop. */
135 andi. r6, r11, 0xF
136 bne L(loop_start)
137
138 /* Prepare for the loop. */
139 subf r4, r9, r4 /* Adjust r4 based on alignment. */
140 li r7, 16 /* Load required offsets. */
141 li r8, 32
142 li r9, 48
143 vspltisb v0, 0
144 addi r4, r4, 16
145 /* Are we 64-byte aligned? If so, jump to the vectorized loop.
146 Else copy 16B till r4 is 64B aligned. */
147 andi. r6, r4, 63
148 beq L(qw_loop)
149
150 lvx v6, 0, r4 /* Load 16 bytes from memory. */
151 vcmpequb. v5, v0, v6 /* Check for null. */
152 bne cr6, L(qw_done)
153 stvx v6, 0, r11 /* Store 16 bytes. */
154 addi r4, r4, 16 /* Increment the address. */
155 addi r11, r11, 16
156 andi. r6, r4, 63
157 beq L(qw_loop)
158
159 lvx v6, 0, r4
160 vcmpequb. v5, v0, v6
161 bne cr6, L(qw_done)
162 stvx v6, 0, r11
163 addi r4, r4, 16
164 addi r11, r11, 16
165 andi. r6, r4, 63
166 beq L(qw_loop)
167
168 lvx v6, 0, r4
169 vcmpequb. v5, v0, v6
170 bne cr6, L(qw_done)
171 stvx v6, 0, r11
172 addi r4, r4, 16
173 addi r11, r11, 16
174
175 .align 4
176L(qw_loop):
177 lvx v1, r4, r0 /* Load 4 quadwords. */
178 lvx v2, r4, r7
179 lvx v3, r4, r8
180 lvx v4, r4, r9
181 vminub v5, v1, v2 /* Compare and merge into one VR for speed. */
182 vminub v8, v3, v4
183 vminub v7, v5, v8
184 vcmpequb. v7, v7, v0 /* Check for NULLs. */
185 bne cr6, L(qw_loop_done)
186 stvx v1, r11, r0 /* Store 4 quadwords. */
187 stvx v2, r11, r7
188 stvx v3, r11, r8
189 stvx v4, r11, r9
190 addi r4, r4, 64 /* Adjust address for the next iteration. */
191 addi r11, r11, 64 /* Adjust address for the next iteration. */
192
193 lvx v1, r4, r0 /* Load 4 quadwords. */
194 lvx v2, r4, r7
195 lvx v3, r4, r8
196 lvx v4, r4, r9
197 vminub v5, v1, v2 /* Compare and merge into one VR for speed. */
198 vminub v8, v3, v4
199 vminub v7, v5, v8
200 vcmpequb. v7, v7, v0 /* Check for NULLs. */
201 bne cr6, L(qw_loop_done)
202 stvx v1, r11, r0 /* Store 4 quadwords. */
203 stvx v2, r11, r7
204 stvx v3, r11, r8
205 stvx v4, r11, r9
206 addi r4, r4, 64 /* Adjust address for the next iteration. */
207 addi r11, r11, 64 /* Adjust address for the next iteration. */
208
209 lvx v1, r4, r0 /* Load 4 quadwords. */
210 lvx v2, r4, r7
211 lvx v3, r4, r8
212 lvx v4, r4, r9
213 vminub v5, v1, v2 /* Compare and merge into one VR for speed. */
214 vminub v8, v3, v4
215 vminub v7, v5, v8
216 vcmpequb. v7, v7, v0 /* Check for NULLs. */
217 bne cr6, L(qw_loop_done)
218 stvx v1, r11, r0 /* Store 4 quadwords. */
219 stvx v2, r11, r7
220 stvx v3, r11, r8
221 stvx v4, r11, r9
222 addi r4, r4, 64 /* Adjust address for the next iteration. */
223 addi r11, r11, 64 /* Adjust address for the next iteration. */
224 b L(qw_loop)
225
226 .align 4
227L(qw_loop_done):
228 /* Null found in one of the 4 loads. */
229 vcmpequb. v7, v1, v0
230 vor v6, v1, v1
231 bne cr6, L(qw_done)
232 /* Not on the first 16B, So store it. */
233 stvx v1, r11, r0
234 addi r4, r4, 16
235 addi r11, r11, 16
236 vcmpequb. v7, v2, v0
237 vor v6, v2, v2
238 bne cr6, L(qw_done)
239 /* Not on the second 16B, So store it. */
240 stvx v2, r11, r0
241 addi r4, r4, 16
242 addi r11, r11, 16
243 vcmpequb. v7, v3, v0
244 vor v6, v3, v3
245 bne cr6, L(qw_done)
246 /* Not on the third 16B, So store it. */
247 stvx v6, r11, r0
248 addi r4, r4, 16
249 addi r11, r11, 16
250 vor v6, v4, v4
251
252 .align 4
253L(qw_done):
254 mr r7, r4
255 /* Move the result to GPR. */
256#ifdef __LITTLE_ENDIAN__
257 vsldoi v4, v6, v0, 8
258 mfvrd r12, v4
259#else
260 mfvrd r12, v6
261#endif
262 /* Check for null in the first 8 bytes. */
263 cmpb r10, r12, r0
264 cmpdi cr6, r10, 0
265 bne cr6, L(done2)
266 /* Null found in second doubleword. */
267#ifdef __LITTLE_ENDIAN__
268 mfvrd r6, v6
269#else
270 vsldoi v6, v6, v0, 8
271 mfvrd r6, v6
272#endif
273 cmpb r10, r6, r0
274 addi r7, r7, 8
275 b L(done2)
276
277 .align 5
278L(loop):
279 std r12, 0(r11)
280 std r6, 8(r11)
281 addi r11,r11,16
282L(loop_start):
283 /* Load two doublewords, compare and merge in a
284 single register for speed. This is an attempt
285 to speed up the null-checking process for bigger strings. */
286
287 ld r12, 8(r7)
288 ldu r6, 16(r7)
289 cmpb r10,r12,r0
290 cmpb r9,r6,r0
291 or r8,r9,r10 /* Merge everything in one doubleword. */
292 cmpdi cr7,r8,0
293 beq cr7,L(loop)
294
295
296 /* OK, one (or both) of the doublewords contains a null byte. Check
297 the first doubleword and decrement the address in case the first
298 doubleword really contains a null byte. */
299
300 addi r4,r7,-8
301 cmpdi cr6,r10,0
302 addi r7,r7,-8
303 bne cr6,L(done2)
304
305 /* The null byte must be in the second doubleword. Adjust the address
306 again and move the result of cmpb to r10 so we can calculate the
307 length. */
308
309 mr r10,r9
310 addi r7,r7,8
311 b L(done2)
312
313 /* r10 has the output of the cmpb instruction, that is, it contains
314 0xff in the same position as the null byte in the original
315 doubleword from the string. Use that to calculate the length. */
316L(done):
317 mr r11,r3
318L(done2):
319#ifdef __LITTLE_ENDIAN__
320 addi r9, r10, -1 /* Form a mask from trailing zeros. */
321 andc r9, r9, r10
322 popcntd r6, r9 /* Count the bits in the mask. */
323#else
324 cntlzd r6,r10 /* Count leading zeros before the match. */
325#endif
326 subf r5,r4,r7
327 srdi r6,r6,3 /* Convert leading/trailing zeros to bytes. */
328 add r8,r5,r6 /* Compute final length. */
329#ifdef USE_AS_STPCPY
330 /* stpcpy returns the dest address plus the size not counting the
331 final '\0'. */
332 add r3,r11,r8
333#endif
334 addi r8,r8,1 /* Final '/0'. */
335
336 cmpldi cr6,r8,8
337 mtocrf 0x01,r8
338 ble cr6,L(copy_LE_8)
339
340 cmpldi cr1,r8,16
341 blt cr1,8f
342
343 /* Handle copies of 0~31 bytes. */
344 .align 4
345L(copy_LT_32):
346 /* At least 6 bytes to go. */
347 blt cr1,8f
348
349 /* Copy 16 bytes. */
350 ld r6,0(r4)
351 ld r8,8(r4)
352 addi r4,r4,16
353 std r6,0(r11)
354 std r8,8(r11)
355 addi r11,r11,16
3568: /* Copy 8 bytes. */
357 bf 28,L(tail4)
358 ld r6,0(r4)
359 addi r4,r4,8
360 std r6,0(r11)
361 addi r11,r11,8
362
363 .align 4
364/* Copies 4~7 bytes. */
365L(tail4):
366 bf 29,L(tail2)
367 lwz r6,0(r4)
368 stw r6,0(r11)
369 bf 30,L(tail5)
370 lhz r7,4(r4)
371 sth r7,4(r11)
372 bflr 31
373 lbz r8,6(r4)
374 stb r8,6(r11)
375 blr
376
377 .align 4
378/* Copies 2~3 bytes. */
379L(tail2):
380 bf 30,1f
381 lhz r6,0(r4)
382 sth r6,0(r11)
383 bflr 31
384 lbz r7,2(r4)
385 stb r7,2(r11)
386 blr
387
388 .align 4
389L(tail5):
390 bf 31,1f
391 lbz r6,4(r4)
392 stb r6,4(r11)
393 blr
394
395 .align 4
3961:
397 bflr 31
398 lbz r6,0(r4)
399 stb r6,0(r11)
400 blr
401
402/* Handles copies of 0~8 bytes. */
403 .align 4
404L(copy_LE_8):
405 bne cr6,L(tail4)
406 ld r6,0(r4)
407 std r6,0(r11)
408 blr
409END (FUNC_NAME)
410
411#ifndef USE_AS_STPCPY
412libc_hidden_builtin_def (strcpy)
413#endif
414

source code of glibc/sysdeps/powerpc/powerpc64/power8/strcpy.S