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Diffstat (limited to 'arch/alpha/lib/stxncpy.S')
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1 | /* | ||
2 | * arch/alpha/lib/stxncpy.S | ||
3 | * Contributed by Richard Henderson (rth@tamu.edu) | ||
4 | * | ||
5 | * Copy no more than COUNT bytes of the null-terminated string from | ||
6 | * SRC to DST. | ||
7 | * | ||
8 | * This is an internal routine used by strncpy, stpncpy, and strncat. | ||
9 | * As such, it uses special linkage conventions to make implementation | ||
10 | * of these public functions more efficient. | ||
11 | * | ||
12 | * On input: | ||
13 | * t9 = return address | ||
14 | * a0 = DST | ||
15 | * a1 = SRC | ||
16 | * a2 = COUNT | ||
17 | * | ||
18 | * Furthermore, COUNT may not be zero. | ||
19 | * | ||
20 | * On output: | ||
21 | * t0 = last word written | ||
22 | * t10 = bitmask (with one bit set) indicating the byte position of | ||
23 | * the end of the range specified by COUNT | ||
24 | * t12 = bitmask (with one bit set) indicating the last byte written | ||
25 | * a0 = unaligned address of the last *word* written | ||
26 | * a2 = the number of full words left in COUNT | ||
27 | * | ||
28 | * Furthermore, v0, a3-a5, t11, and $at are untouched. | ||
29 | */ | ||
30 | |||
31 | #include <asm/regdef.h> | ||
32 | |||
33 | .set noat | ||
34 | .set noreorder | ||
35 | |||
36 | .text | ||
37 | |||
38 | /* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that | ||
39 | doesn't like putting the entry point for a procedure somewhere in the | ||
40 | middle of the procedure descriptor. Work around this by putting the | ||
41 | aligned copy in its own procedure descriptor */ | ||
42 | |||
43 | .ent stxncpy_aligned | ||
44 | .align 3 | ||
45 | stxncpy_aligned: | ||
46 | .frame sp, 0, t9, 0 | ||
47 | .prologue 0 | ||
48 | |||
49 | /* On entry to this basic block: | ||
50 | t0 == the first destination word for masking back in | ||
51 | t1 == the first source word. */ | ||
52 | |||
53 | /* Create the 1st output word and detect 0's in the 1st input word. */ | ||
54 | lda t2, -1 # e1 : build a mask against false zero | ||
55 | mskqh t2, a1, t2 # e0 : detection in the src word | ||
56 | mskqh t1, a1, t3 # e0 : | ||
57 | ornot t1, t2, t2 # .. e1 : | ||
58 | mskql t0, a1, t0 # e0 : assemble the first output word | ||
59 | cmpbge zero, t2, t8 # .. e1 : bits set iff null found | ||
60 | or t0, t3, t0 # e0 : | ||
61 | beq a2, $a_eoc # .. e1 : | ||
62 | bne t8, $a_eos # .. e1 : | ||
63 | |||
64 | /* On entry to this basic block: | ||
65 | t0 == a source word not containing a null. */ | ||
66 | |||
67 | $a_loop: | ||
68 | stq_u t0, 0(a0) # e0 : | ||
69 | addq a0, 8, a0 # .. e1 : | ||
70 | ldq_u t0, 0(a1) # e0 : | ||
71 | addq a1, 8, a1 # .. e1 : | ||
72 | subq a2, 1, a2 # e0 : | ||
73 | cmpbge zero, t0, t8 # .. e1 (stall) | ||
74 | beq a2, $a_eoc # e1 : | ||
75 | beq t8, $a_loop # e1 : | ||
76 | |||
77 | /* Take care of the final (partial) word store. At this point | ||
78 | the end-of-count bit is set in t8 iff it applies. | ||
79 | |||
80 | On entry to this basic block we have: | ||
81 | t0 == the source word containing the null | ||
82 | t8 == the cmpbge mask that found it. */ | ||
83 | |||
84 | $a_eos: | ||
85 | negq t8, t12 # e0 : find low bit set | ||
86 | and t8, t12, t12 # e1 (stall) | ||
87 | |||
88 | /* For the sake of the cache, don't read a destination word | ||
89 | if we're not going to need it. */ | ||
90 | and t12, 0x80, t6 # e0 : | ||
91 | bne t6, 1f # .. e1 (zdb) | ||
92 | |||
93 | /* We're doing a partial word store and so need to combine | ||
94 | our source and original destination words. */ | ||
95 | ldq_u t1, 0(a0) # e0 : | ||
96 | subq t12, 1, t6 # .. e1 : | ||
97 | or t12, t6, t8 # e0 : | ||
98 | unop # | ||
99 | zapnot t0, t8, t0 # e0 : clear src bytes > null | ||
100 | zap t1, t8, t1 # .. e1 : clear dst bytes <= null | ||
101 | or t0, t1, t0 # e1 : | ||
102 | |||
103 | 1: stq_u t0, 0(a0) # e0 : | ||
104 | ret (t9) # e1 : | ||
105 | |||
106 | /* Add the end-of-count bit to the eos detection bitmask. */ | ||
107 | $a_eoc: | ||
108 | or t10, t8, t8 | ||
109 | br $a_eos | ||
110 | |||
111 | .end stxncpy_aligned | ||
112 | |||
113 | .align 3 | ||
114 | .ent __stxncpy | ||
115 | .globl __stxncpy | ||
116 | __stxncpy: | ||
117 | .frame sp, 0, t9, 0 | ||
118 | .prologue 0 | ||
119 | |||
120 | /* Are source and destination co-aligned? */ | ||
121 | xor a0, a1, t1 # e0 : | ||
122 | and a0, 7, t0 # .. e1 : find dest misalignment | ||
123 | and t1, 7, t1 # e0 : | ||
124 | addq a2, t0, a2 # .. e1 : bias count by dest misalignment | ||
125 | subq a2, 1, a2 # e0 : | ||
126 | and a2, 7, t2 # e1 : | ||
127 | srl a2, 3, a2 # e0 : a2 = loop counter = (count - 1)/8 | ||
128 | addq zero, 1, t10 # .. e1 : | ||
129 | sll t10, t2, t10 # e0 : t10 = bitmask of last count byte | ||
130 | bne t1, $unaligned # .. e1 : | ||
131 | |||
132 | /* We are co-aligned; take care of a partial first word. */ | ||
133 | |||
134 | ldq_u t1, 0(a1) # e0 : load first src word | ||
135 | addq a1, 8, a1 # .. e1 : | ||
136 | |||
137 | beq t0, stxncpy_aligned # avoid loading dest word if not needed | ||
138 | ldq_u t0, 0(a0) # e0 : | ||
139 | br stxncpy_aligned # .. e1 : | ||
140 | |||
141 | |||
142 | /* The source and destination are not co-aligned. Align the destination | ||
143 | and cope. We have to be very careful about not reading too much and | ||
144 | causing a SEGV. */ | ||
145 | |||
146 | .align 3 | ||
147 | $u_head: | ||
148 | /* We know just enough now to be able to assemble the first | ||
149 | full source word. We can still find a zero at the end of it | ||
150 | that prevents us from outputting the whole thing. | ||
151 | |||
152 | On entry to this basic block: | ||
153 | t0 == the first dest word, unmasked | ||
154 | t1 == the shifted low bits of the first source word | ||
155 | t6 == bytemask that is -1 in dest word bytes */ | ||
156 | |||
157 | ldq_u t2, 8(a1) # e0 : load second src word | ||
158 | addq a1, 8, a1 # .. e1 : | ||
159 | mskql t0, a0, t0 # e0 : mask trailing garbage in dst | ||
160 | extqh t2, a1, t4 # e0 : | ||
161 | or t1, t4, t1 # e1 : first aligned src word complete | ||
162 | mskqh t1, a0, t1 # e0 : mask leading garbage in src | ||
163 | or t0, t1, t0 # e0 : first output word complete | ||
164 | or t0, t6, t6 # e1 : mask original data for zero test | ||
165 | cmpbge zero, t6, t8 # e0 : | ||
166 | beq a2, $u_eocfin # .. e1 : | ||
167 | lda t6, -1 # e0 : | ||
168 | bne t8, $u_final # .. e1 : | ||
169 | |||
170 | mskql t6, a1, t6 # e0 : mask out bits already seen | ||
171 | nop # .. e1 : | ||
172 | stq_u t0, 0(a0) # e0 : store first output word | ||
173 | or t6, t2, t2 # .. e1 : | ||
174 | cmpbge zero, t2, t8 # e0 : find nulls in second partial | ||
175 | addq a0, 8, a0 # .. e1 : | ||
176 | subq a2, 1, a2 # e0 : | ||
177 | bne t8, $u_late_head_exit # .. e1 : | ||
178 | |||
179 | /* Finally, we've got all the stupid leading edge cases taken care | ||
180 | of and we can set up to enter the main loop. */ | ||
181 | |||
182 | extql t2, a1, t1 # e0 : position hi-bits of lo word | ||
183 | beq a2, $u_eoc # .. e1 : | ||
184 | ldq_u t2, 8(a1) # e0 : read next high-order source word | ||
185 | addq a1, 8, a1 # .. e1 : | ||
186 | extqh t2, a1, t0 # e0 : position lo-bits of hi word (stall) | ||
187 | cmpbge zero, t2, t8 # .. e1 : | ||
188 | nop # e0 : | ||
189 | bne t8, $u_eos # .. e1 : | ||
190 | |||
191 | /* Unaligned copy main loop. In order to avoid reading too much, | ||
192 | the loop is structured to detect zeros in aligned source words. | ||
193 | This has, unfortunately, effectively pulled half of a loop | ||
194 | iteration out into the head and half into the tail, but it does | ||
195 | prevent nastiness from accumulating in the very thing we want | ||
196 | to run as fast as possible. | ||
197 | |||
198 | On entry to this basic block: | ||
199 | t0 == the shifted low-order bits from the current source word | ||
200 | t1 == the shifted high-order bits from the previous source word | ||
201 | t2 == the unshifted current source word | ||
202 | |||
203 | We further know that t2 does not contain a null terminator. */ | ||
204 | |||
205 | .align 3 | ||
206 | $u_loop: | ||
207 | or t0, t1, t0 # e0 : current dst word now complete | ||
208 | subq a2, 1, a2 # .. e1 : decrement word count | ||
209 | stq_u t0, 0(a0) # e0 : save the current word | ||
210 | addq a0, 8, a0 # .. e1 : | ||
211 | extql t2, a1, t1 # e0 : extract high bits for next time | ||
212 | beq a2, $u_eoc # .. e1 : | ||
213 | ldq_u t2, 8(a1) # e0 : load high word for next time | ||
214 | addq a1, 8, a1 # .. e1 : | ||
215 | nop # e0 : | ||
216 | cmpbge zero, t2, t8 # e1 : test new word for eos (stall) | ||
217 | extqh t2, a1, t0 # e0 : extract low bits for current word | ||
218 | beq t8, $u_loop # .. e1 : | ||
219 | |||
220 | /* We've found a zero somewhere in the source word we just read. | ||
221 | If it resides in the lower half, we have one (probably partial) | ||
222 | word to write out, and if it resides in the upper half, we | ||
223 | have one full and one partial word left to write out. | ||
224 | |||
225 | On entry to this basic block: | ||
226 | t0 == the shifted low-order bits from the current source word | ||
227 | t1 == the shifted high-order bits from the previous source word | ||
228 | t2 == the unshifted current source word. */ | ||
229 | $u_eos: | ||
230 | or t0, t1, t0 # e0 : first (partial) source word complete | ||
231 | nop # .. e1 : | ||
232 | cmpbge zero, t0, t8 # e0 : is the null in this first bit? | ||
233 | bne t8, $u_final # .. e1 (zdb) | ||
234 | |||
235 | stq_u t0, 0(a0) # e0 : the null was in the high-order bits | ||
236 | addq a0, 8, a0 # .. e1 : | ||
237 | subq a2, 1, a2 # e1 : | ||
238 | |||
239 | $u_late_head_exit: | ||
240 | extql t2, a1, t0 # .. e0 : | ||
241 | cmpbge zero, t0, t8 # e0 : | ||
242 | or t8, t10, t6 # e1 : | ||
243 | cmoveq a2, t6, t8 # e0 : | ||
244 | nop # .. e1 : | ||
245 | |||
246 | /* Take care of a final (probably partial) result word. | ||
247 | On entry to this basic block: | ||
248 | t0 == assembled source word | ||
249 | t8 == cmpbge mask that found the null. */ | ||
250 | $u_final: | ||
251 | negq t8, t6 # e0 : isolate low bit set | ||
252 | and t6, t8, t12 # e1 : | ||
253 | |||
254 | and t12, 0x80, t6 # e0 : avoid dest word load if we can | ||
255 | bne t6, 1f # .. e1 (zdb) | ||
256 | |||
257 | ldq_u t1, 0(a0) # e0 : | ||
258 | subq t12, 1, t6 # .. e1 : | ||
259 | or t6, t12, t8 # e0 : | ||
260 | zapnot t0, t8, t0 # .. e1 : kill source bytes > null | ||
261 | zap t1, t8, t1 # e0 : kill dest bytes <= null | ||
262 | or t0, t1, t0 # e1 : | ||
263 | |||
264 | 1: stq_u t0, 0(a0) # e0 : | ||
265 | ret (t9) # .. e1 : | ||
266 | |||
267 | /* Got to end-of-count before end of string. | ||
268 | On entry to this basic block: | ||
269 | t1 == the shifted high-order bits from the previous source word */ | ||
270 | $u_eoc: | ||
271 | and a1, 7, t6 # e1 : | ||
272 | sll t10, t6, t6 # e0 : | ||
273 | and t6, 0xff, t6 # e0 : | ||
274 | bne t6, 1f # .. e1 : | ||
275 | |||
276 | ldq_u t2, 8(a1) # e0 : load final src word | ||
277 | nop # .. e1 : | ||
278 | extqh t2, a1, t0 # e0 : extract low bits for last word | ||
279 | or t1, t0, t1 # e1 : | ||
280 | |||
281 | 1: cmpbge zero, t1, t8 | ||
282 | mov t1, t0 | ||
283 | |||
284 | $u_eocfin: # end-of-count, final word | ||
285 | or t10, t8, t8 | ||
286 | br $u_final | ||
287 | |||
288 | /* Unaligned copy entry point. */ | ||
289 | .align 3 | ||
290 | $unaligned: | ||
291 | |||
292 | ldq_u t1, 0(a1) # e0 : load first source word | ||
293 | |||
294 | and a0, 7, t4 # .. e1 : find dest misalignment | ||
295 | and a1, 7, t5 # e0 : find src misalignment | ||
296 | |||
297 | /* Conditionally load the first destination word and a bytemask | ||
298 | with 0xff indicating that the destination byte is sacrosanct. */ | ||
299 | |||
300 | mov zero, t0 # .. e1 : | ||
301 | mov zero, t6 # e0 : | ||
302 | beq t4, 1f # .. e1 : | ||
303 | ldq_u t0, 0(a0) # e0 : | ||
304 | lda t6, -1 # .. e1 : | ||
305 | mskql t6, a0, t6 # e0 : | ||
306 | subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr | ||
307 | |||
308 | /* If source misalignment is larger than dest misalignment, we need | ||
309 | extra startup checks to avoid SEGV. */ | ||
310 | |||
311 | 1: cmplt t4, t5, t12 # e1 : | ||
312 | extql t1, a1, t1 # .. e0 : shift src into place | ||
313 | lda t2, -1 # e0 : for creating masks later | ||
314 | beq t12, $u_head # .. e1 : | ||
315 | |||
316 | extql t2, a1, t2 # e0 : | ||
317 | cmpbge zero, t1, t8 # .. e1 : is there a zero? | ||
318 | andnot t2, t6, t12 # e0 : dest mask for a single word copy | ||
319 | or t8, t10, t5 # .. e1 : test for end-of-count too | ||
320 | cmpbge zero, t12, t3 # e0 : | ||
321 | cmoveq a2, t5, t8 # .. e1 : | ||
322 | andnot t8, t3, t8 # e0 : | ||
323 | beq t8, $u_head # .. e1 (zdb) | ||
324 | |||
325 | /* At this point we've found a zero in the first partial word of | ||
326 | the source. We need to isolate the valid source data and mask | ||
327 | it into the original destination data. (Incidentally, we know | ||
328 | that we'll need at least one byte of that original dest word.) */ | ||
329 | |||
330 | ldq_u t0, 0(a0) # e0 : | ||
331 | negq t8, t6 # .. e1 : build bitmask of bytes <= zero | ||
332 | mskqh t1, t4, t1 # e0 : | ||
333 | and t6, t8, t2 # .. e1 : | ||
334 | subq t2, 1, t6 # e0 : | ||
335 | or t6, t2, t8 # e1 : | ||
336 | |||
337 | zapnot t12, t8, t12 # e0 : prepare source word; mirror changes | ||
338 | zapnot t1, t8, t1 # .. e1 : to source validity mask | ||
339 | |||
340 | andnot t0, t12, t0 # e0 : zero place for source to reside | ||
341 | or t0, t1, t0 # e1 : and put it there | ||
342 | stq_u t0, 0(a0) # e0 : | ||
343 | ret (t9) # .. e1 : | ||
344 | |||
345 | .end __stxncpy | ||