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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
1da177e4 LT |
2 | /* |
3 | * arch/alpha/lib/ev6-stxncpy.S | |
4 | * 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com> | |
5 | * | |
6 | * Copy no more than COUNT bytes of the null-terminated string from | |
7 | * SRC to DST. | |
8 | * | |
9 | * This is an internal routine used by strncpy, stpncpy, and strncat. | |
10 | * As such, it uses special linkage conventions to make implementation | |
11 | * of these public functions more efficient. | |
12 | * | |
13 | * On input: | |
14 | * t9 = return address | |
15 | * a0 = DST | |
16 | * a1 = SRC | |
17 | * a2 = COUNT | |
18 | * | |
19 | * Furthermore, COUNT may not be zero. | |
20 | * | |
21 | * On output: | |
22 | * t0 = last word written | |
23 | * t10 = bitmask (with one bit set) indicating the byte position of | |
24 | * the end of the range specified by COUNT | |
25 | * t12 = bitmask (with one bit set) indicating the last byte written | |
26 | * a0 = unaligned address of the last *word* written | |
27 | * a2 = the number of full words left in COUNT | |
28 | * | |
29 | * Furthermore, v0, a3-a5, t11, and $at are untouched. | |
30 | * | |
31 | * Much of the information about 21264 scheduling/coding comes from: | |
32 | * Compiler Writer's Guide for the Alpha 21264 | |
33 | * abbreviated as 'CWG' in other comments here | |
34 | * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html | |
35 | * Scheduling notation: | |
36 | * E - either cluster | |
37 | * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 | |
38 | * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 | |
39 | * Try not to change the actual algorithm if possible for consistency. | |
40 | */ | |
41 | ||
42 | #include <asm/regdef.h> | |
43 | ||
44 | .set noat | |
45 | .set noreorder | |
46 | ||
47 | .text | |
48 | ||
49 | /* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that | |
50 | doesn't like putting the entry point for a procedure somewhere in the | |
51 | middle of the procedure descriptor. Work around this by putting the | |
52 | aligned copy in its own procedure descriptor */ | |
53 | ||
54 | ||
55 | .ent stxncpy_aligned | |
56 | .align 4 | |
57 | stxncpy_aligned: | |
58 | .frame sp, 0, t9, 0 | |
59 | .prologue 0 | |
60 | ||
61 | /* On entry to this basic block: | |
62 | t0 == the first destination word for masking back in | |
63 | t1 == the first source word. */ | |
64 | ||
65 | /* Create the 1st output word and detect 0's in the 1st input word. */ | |
66 | lda t2, -1 # E : build a mask against false zero | |
67 | mskqh t2, a1, t2 # U : detection in the src word (stall) | |
68 | mskqh t1, a1, t3 # U : | |
69 | ornot t1, t2, t2 # E : (stall) | |
70 | ||
71 | mskql t0, a1, t0 # U : assemble the first output word | |
72 | cmpbge zero, t2, t8 # E : bits set iff null found | |
73 | or t0, t3, t0 # E : (stall) | |
74 | beq a2, $a_eoc # U : | |
75 | ||
76 | bne t8, $a_eos # U : | |
77 | nop | |
78 | nop | |
79 | nop | |
80 | ||
81 | /* On entry to this basic block: | |
82 | t0 == a source word not containing a null. */ | |
83 | ||
84 | /* | |
85 | * nops here to: | |
86 | * separate store quads from load quads | |
87 | * limit of 1 bcond/quad to permit training | |
88 | */ | |
89 | $a_loop: | |
90 | stq_u t0, 0(a0) # L : | |
91 | addq a0, 8, a0 # E : | |
92 | subq a2, 1, a2 # E : | |
93 | nop | |
94 | ||
95 | ldq_u t0, 0(a1) # L : | |
96 | addq a1, 8, a1 # E : | |
97 | cmpbge zero, t0, t8 # E : | |
98 | beq a2, $a_eoc # U : | |
99 | ||
100 | beq t8, $a_loop # U : | |
101 | nop | |
102 | nop | |
103 | nop | |
104 | ||
105 | /* Take care of the final (partial) word store. At this point | |
106 | the end-of-count bit is set in t8 iff it applies. | |
107 | ||
108 | On entry to this basic block we have: | |
109 | t0 == the source word containing the null | |
110 | t8 == the cmpbge mask that found it. */ | |
111 | ||
112 | $a_eos: | |
113 | negq t8, t12 # E : find low bit set | |
114 | and t8, t12, t12 # E : (stall) | |
115 | /* For the sake of the cache, don't read a destination word | |
116 | if we're not going to need it. */ | |
117 | and t12, 0x80, t6 # E : (stall) | |
118 | bne t6, 1f # U : (stall) | |
119 | ||
120 | /* We're doing a partial word store and so need to combine | |
121 | our source and original destination words. */ | |
122 | ldq_u t1, 0(a0) # L : | |
123 | subq t12, 1, t6 # E : | |
124 | or t12, t6, t8 # E : (stall) | |
125 | zapnot t0, t8, t0 # U : clear src bytes > null (stall) | |
126 | ||
127 | zap t1, t8, t1 # .. e1 : clear dst bytes <= null | |
128 | or t0, t1, t0 # e1 : (stall) | |
129 | nop | |
130 | nop | |
131 | ||
132 | 1: stq_u t0, 0(a0) # L : | |
133 | ret (t9) # L0 : Latency=3 | |
134 | nop | |
135 | nop | |
136 | ||
137 | /* Add the end-of-count bit to the eos detection bitmask. */ | |
138 | $a_eoc: | |
139 | or t10, t8, t8 # E : | |
140 | br $a_eos # L0 : Latency=3 | |
141 | nop | |
142 | nop | |
143 | ||
144 | .end stxncpy_aligned | |
145 | ||
146 | .align 4 | |
147 | .ent __stxncpy | |
148 | .globl __stxncpy | |
149 | __stxncpy: | |
150 | .frame sp, 0, t9, 0 | |
151 | .prologue 0 | |
152 | ||
153 | /* Are source and destination co-aligned? */ | |
154 | xor a0, a1, t1 # E : | |
155 | and a0, 7, t0 # E : find dest misalignment | |
156 | and t1, 7, t1 # E : (stall) | |
157 | addq a2, t0, a2 # E : bias count by dest misalignment (stall) | |
158 | ||
159 | subq a2, 1, a2 # E : | |
160 | and a2, 7, t2 # E : (stall) | |
161 | srl a2, 3, a2 # U : a2 = loop counter = (count - 1)/8 (stall) | |
162 | addq zero, 1, t10 # E : | |
163 | ||
164 | sll t10, t2, t10 # U : t10 = bitmask of last count byte | |
165 | bne t1, $unaligned # U : | |
166 | /* We are co-aligned; take care of a partial first word. */ | |
167 | ldq_u t1, 0(a1) # L : load first src word | |
168 | addq a1, 8, a1 # E : | |
169 | ||
170 | beq t0, stxncpy_aligned # U : avoid loading dest word if not needed | |
171 | ldq_u t0, 0(a0) # L : | |
172 | nop | |
173 | nop | |
174 | ||
175 | br stxncpy_aligned # .. e1 : | |
176 | nop | |
177 | nop | |
178 | nop | |
179 | ||
180 | ||
181 | ||
182 | /* The source and destination are not co-aligned. Align the destination | |
183 | and cope. We have to be very careful about not reading too much and | |
184 | causing a SEGV. */ | |
185 | ||
186 | .align 4 | |
187 | $u_head: | |
188 | /* We know just enough now to be able to assemble the first | |
189 | full source word. We can still find a zero at the end of it | |
190 | that prevents us from outputting the whole thing. | |
191 | ||
192 | On entry to this basic block: | |
193 | t0 == the first dest word, unmasked | |
194 | t1 == the shifted low bits of the first source word | |
195 | t6 == bytemask that is -1 in dest word bytes */ | |
196 | ||
197 | ldq_u t2, 8(a1) # L : Latency=3 load second src word | |
198 | addq a1, 8, a1 # E : | |
199 | mskql t0, a0, t0 # U : mask trailing garbage in dst | |
200 | extqh t2, a1, t4 # U : (3 cycle stall on t2) | |
201 | ||
202 | or t1, t4, t1 # E : first aligned src word complete (stall) | |
203 | mskqh t1, a0, t1 # U : mask leading garbage in src (stall) | |
204 | or t0, t1, t0 # E : first output word complete (stall) | |
205 | or t0, t6, t6 # E : mask original data for zero test (stall) | |
206 | ||
207 | cmpbge zero, t6, t8 # E : | |
208 | beq a2, $u_eocfin # U : | |
209 | lda t6, -1 # E : | |
210 | nop | |
211 | ||
212 | bne t8, $u_final # U : | |
213 | mskql t6, a1, t6 # U : mask out bits already seen | |
214 | stq_u t0, 0(a0) # L : store first output word | |
215 | or t6, t2, t2 # E : (stall) | |
216 | ||
217 | cmpbge zero, t2, t8 # E : find nulls in second partial | |
218 | addq a0, 8, a0 # E : | |
219 | subq a2, 1, a2 # E : | |
220 | bne t8, $u_late_head_exit # U : | |
221 | ||
222 | /* Finally, we've got all the stupid leading edge cases taken care | |
223 | of and we can set up to enter the main loop. */ | |
224 | extql t2, a1, t1 # U : position hi-bits of lo word | |
225 | beq a2, $u_eoc # U : | |
226 | ldq_u t2, 8(a1) # L : read next high-order source word | |
227 | addq a1, 8, a1 # E : | |
228 | ||
229 | extqh t2, a1, t0 # U : position lo-bits of hi word (stall) | |
230 | cmpbge zero, t2, t8 # E : | |
231 | nop | |
232 | bne t8, $u_eos # U : | |
233 | ||
234 | /* Unaligned copy main loop. In order to avoid reading too much, | |
235 | the loop is structured to detect zeros in aligned source words. | |
236 | This has, unfortunately, effectively pulled half of a loop | |
237 | iteration out into the head and half into the tail, but it does | |
238 | prevent nastiness from accumulating in the very thing we want | |
239 | to run as fast as possible. | |
240 | ||
241 | On entry to this basic block: | |
242 | t0 == the shifted low-order bits from the current source word | |
243 | t1 == the shifted high-order bits from the previous source word | |
244 | t2 == the unshifted current source word | |
245 | ||
246 | We further know that t2 does not contain a null terminator. */ | |
247 | ||
248 | .align 4 | |
249 | $u_loop: | |
250 | or t0, t1, t0 # E : current dst word now complete | |
251 | subq a2, 1, a2 # E : decrement word count | |
252 | extql t2, a1, t1 # U : extract low bits for next time | |
253 | addq a0, 8, a0 # E : | |
254 | ||
255 | stq_u t0, -8(a0) # U : save the current word | |
256 | beq a2, $u_eoc # U : | |
257 | ldq_u t2, 8(a1) # U : Latency=3 load high word for next time | |
258 | addq a1, 8, a1 # E : | |
259 | ||
260 | extqh t2, a1, t0 # U : extract low bits (2 cycle stall) | |
261 | cmpbge zero, t2, t8 # E : test new word for eos | |
262 | nop | |
263 | beq t8, $u_loop # U : | |
264 | ||
265 | /* We've found a zero somewhere in the source word we just read. | |
266 | If it resides in the lower half, we have one (probably partial) | |
267 | word to write out, and if it resides in the upper half, we | |
268 | have one full and one partial word left to write out. | |
269 | ||
270 | On entry to this basic block: | |
271 | t0 == the shifted low-order bits from the current source word | |
272 | t1 == the shifted high-order bits from the previous source word | |
273 | t2 == the unshifted current source word. */ | |
274 | $u_eos: | |
275 | or t0, t1, t0 # E : first (partial) source word complete | |
276 | nop | |
277 | cmpbge zero, t0, t8 # E : is the null in this first bit? (stall) | |
278 | bne t8, $u_final # U : (stall) | |
279 | ||
280 | stq_u t0, 0(a0) # L : the null was in the high-order bits | |
281 | addq a0, 8, a0 # E : | |
282 | subq a2, 1, a2 # E : | |
283 | nop | |
284 | ||
285 | $u_late_head_exit: | |
286 | extql t2, a1, t0 # U : | |
287 | cmpbge zero, t0, t8 # E : | |
288 | or t8, t10, t6 # E : (stall) | |
289 | cmoveq a2, t6, t8 # E : Latency=2, extra map slot (stall) | |
290 | ||
291 | /* Take care of a final (probably partial) result word. | |
292 | On entry to this basic block: | |
293 | t0 == assembled source word | |
294 | t8 == cmpbge mask that found the null. */ | |
295 | $u_final: | |
296 | negq t8, t6 # E : isolate low bit set | |
297 | and t6, t8, t12 # E : (stall) | |
298 | and t12, 0x80, t6 # E : avoid dest word load if we can (stall) | |
299 | bne t6, 1f # U : (stall) | |
300 | ||
301 | ldq_u t1, 0(a0) # L : | |
302 | subq t12, 1, t6 # E : | |
303 | or t6, t12, t8 # E : (stall) | |
304 | zapnot t0, t8, t0 # U : kill source bytes > null | |
305 | ||
306 | zap t1, t8, t1 # U : kill dest bytes <= null | |
307 | or t0, t1, t0 # E : (stall) | |
308 | nop | |
309 | nop | |
310 | ||
311 | 1: stq_u t0, 0(a0) # L : | |
312 | ret (t9) # L0 : Latency=3 | |
313 | ||
314 | /* Got to end-of-count before end of string. | |
315 | On entry to this basic block: | |
316 | t1 == the shifted high-order bits from the previous source word */ | |
317 | $u_eoc: | |
318 | and a1, 7, t6 # E : avoid final load if possible | |
319 | sll t10, t6, t6 # U : (stall) | |
320 | and t6, 0xff, t6 # E : (stall) | |
321 | bne t6, 1f # U : (stall) | |
322 | ||
323 | ldq_u t2, 8(a1) # L : load final src word | |
324 | nop | |
325 | extqh t2, a1, t0 # U : extract low bits for last word (stall) | |
326 | or t1, t0, t1 # E : (stall) | |
327 | ||
328 | 1: cmpbge zero, t1, t8 # E : | |
329 | mov t1, t0 # E : | |
330 | ||
331 | $u_eocfin: # end-of-count, final word | |
332 | or t10, t8, t8 # E : | |
333 | br $u_final # L0 : Latency=3 | |
334 | ||
335 | /* Unaligned copy entry point. */ | |
336 | .align 4 | |
337 | $unaligned: | |
338 | ||
339 | ldq_u t1, 0(a1) # L : load first source word | |
340 | and a0, 7, t4 # E : find dest misalignment | |
341 | and a1, 7, t5 # E : find src misalignment | |
342 | /* Conditionally load the first destination word and a bytemask | |
343 | with 0xff indicating that the destination byte is sacrosanct. */ | |
344 | mov zero, t0 # E : | |
345 | ||
346 | mov zero, t6 # E : | |
347 | beq t4, 1f # U : | |
348 | ldq_u t0, 0(a0) # L : | |
349 | lda t6, -1 # E : | |
350 | ||
351 | mskql t6, a0, t6 # U : | |
352 | nop | |
353 | nop | |
354 | subq a1, t4, a1 # E : sub dest misalignment from src addr | |
355 | ||
356 | /* If source misalignment is larger than dest misalignment, we need | |
357 | extra startup checks to avoid SEGV. */ | |
358 | ||
359 | 1: cmplt t4, t5, t12 # E : | |
360 | extql t1, a1, t1 # U : shift src into place | |
361 | lda t2, -1 # E : for creating masks later | |
362 | beq t12, $u_head # U : (stall) | |
363 | ||
364 | extql t2, a1, t2 # U : | |
365 | cmpbge zero, t1, t8 # E : is there a zero? | |
fe4304ba | 366 | andnot t2, t6, t2 # E : dest mask for a single word copy |
1da177e4 LT |
367 | or t8, t10, t5 # E : test for end-of-count too |
368 | ||
fe4304ba | 369 | cmpbge zero, t2, t3 # E : |
1da177e4 LT |
370 | cmoveq a2, t5, t8 # E : Latency=2, extra map slot |
371 | nop # E : keep with cmoveq | |
372 | andnot t8, t3, t8 # E : (stall) | |
373 | ||
374 | beq t8, $u_head # U : | |
375 | /* At this point we've found a zero in the first partial word of | |
376 | the source. We need to isolate the valid source data and mask | |
377 | it into the original destination data. (Incidentally, we know | |
378 | that we'll need at least one byte of that original dest word.) */ | |
379 | ldq_u t0, 0(a0) # L : | |
380 | negq t8, t6 # E : build bitmask of bytes <= zero | |
381 | mskqh t1, t4, t1 # U : | |
382 | ||
fe4304ba IK |
383 | and t6, t8, t12 # E : |
384 | subq t12, 1, t6 # E : (stall) | |
385 | or t6, t12, t8 # E : (stall) | |
386 | zapnot t2, t8, t2 # U : prepare source word; mirror changes (stall) | |
1da177e4 LT |
387 | |
388 | zapnot t1, t8, t1 # U : to source validity mask | |
fe4304ba | 389 | andnot t0, t2, t0 # E : zero place for source to reside |
1da177e4 LT |
390 | or t0, t1, t0 # E : and put it there (stall both t0, t1) |
391 | stq_u t0, 0(a0) # L : (stall) | |
392 | ||
393 | ret (t9) # L0 : Latency=3 | |
394 | nop | |
395 | nop | |
396 | nop | |
397 | ||
398 | .end __stxncpy |