Commit | Line | Data |
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1da177e4 LT |
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? | |
fe4304ba | 318 | andnot t2, t6, t2 # e0 : dest mask for a single word copy |
1da177e4 | 319 | or t8, t10, t5 # .. e1 : test for end-of-count too |
fe4304ba | 320 | cmpbge zero, t2, t3 # e0 : |
1da177e4 LT |
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 : | |
fe4304ba IK |
333 | and t6, t8, t12 # .. e1 : |
334 | subq t12, 1, t6 # e0 : | |
335 | or t6, t12, t8 # e1 : | |
1da177e4 | 336 | |
fe4304ba | 337 | zapnot t2, t8, t2 # e0 : prepare source word; mirror changes |
1da177e4 LT |
338 | zapnot t1, t8, t1 # .. e1 : to source validity mask |
339 | ||
fe4304ba | 340 | andnot t0, t2, t0 # e0 : zero place for source to reside |
1da177e4 LT |
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 |