1 /* Copyright (C) 1996, 1997 Free Software Foundation, Inc.
2 Contributed by Richard Henderson (rth@tamu.edu)
3 This file is part of the GNU C Library.
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.
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.
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 <http://www.gnu.org/licenses/>. */
19 /* Copy a null-terminated string from SRC to DST.
21 This is an internal routine used by strcpy, stpcpy, and strcat.
22 As such, it uses special linkage conventions to make implementation
23 of these public functions more efficient.
31 t8 = bitmask (with one bit set) indicating the last byte written
32 a0 = unaligned address of the last *word* written
34 Furthermore, v0, a3-a5, t11, and t12 are untouched.
37 /* This is generally scheduled for the EV5, but should still be pretty
38 good for the EV4 too. */
47 /* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that
48 doesn't like putting the entry point for a procedure somewhere in the
49 middle of the procedure descriptor. Work around this by putting the
50 aligned copy in its own procedure descriptor */
58 /* On entry to this basic block:
59 t0 == the first destination word for masking back in
60 t1 == the first source word. */
62 /* Create the 1st output word and detect 0's in the 1st input word. */
63 lda t2, -1 # e1 : build a mask against false zero
64 mskqh t2, a1, t2 # e0 : detection in the src word
65 mskqh t1, a1, t3 # e0 :
66 ornot t1, t2, t2 # .. e1 :
67 mskql t0, a1, t0 # e0 : assemble the first output word
68 cmpbge zero, t2, t7 # .. e1 : bits set iff null found
70 bne t7, $a_eos # .. e1 :
72 /* On entry to this basic block:
73 t0 == the first destination word for masking back in
74 t1 == a source word not containing a null. */
77 stq_u t1, 0(a0) # e0 :
78 addq a0, 8, a0 # .. e1 :
79 ldq_u t1, 0(a1) # e0 :
80 addq a1, 8, a1 # .. e1 :
81 cmpbge zero, t1, t7 # e0 (stall)
82 beq t7, $a_loop # .. e1 (zdb)
84 /* Take care of the final (partial) word store.
85 On entry to this basic block we have:
86 t1 == the source word containing the null
87 t7 == the cmpbge mask that found it. */
89 negq t7, t6 # e0 : find low bit set
90 and t7, t6, t8 # e1 (stall)
92 /* For the sake of the cache, don't read a destination word
93 if we're not going to need it. */
94 and t8, 0x80, t6 # e0 :
95 bne t6, 1f # .. e1 (zdb)
97 /* We're doing a partial word store and so need to combine
98 our source and original destination words. */
99 ldq_u t0, 0(a0) # e0 :
100 subq t8, 1, t6 # .. e1 :
101 zapnot t1, t6, t1 # e0 : clear src bytes >= null
102 or t8, t6, t7 # .. e1 :
103 zap t0, t7, t0 # e0 : clear dst bytes <= null
106 1: stq_u t1, 0(a0) # e0 :
118 /* Are source and destination co-aligned? */
119 xor a0, a1, t0 # e0 :
122 bne t0, $unaligned # .. e1 :
124 /* We are co-aligned; take care of a partial first word. */
125 ldq_u t1, 0(a1) # e0 : load first src word
126 and a0, 7, t0 # .. e1 : take care not to load a word ...
127 addq a1, 8, a1 # e0 :
128 beq t0, stxcpy_aligned # .. e1 : ... if we wont need it
129 ldq_u t0, 0(a0) # e0 :
130 br stxcpy_aligned # .. e1 :
133 /* The source and destination are not co-aligned. Align the destination
134 and cope. We have to be very careful about not reading too much and
139 /* We know just enough now to be able to assemble the first
140 full source word. We can still find a zero at the end of it
141 that prevents us from outputting the whole thing.
143 On entry to this basic block:
144 t0 == the first dest word, for masking back in, if needed else 0
145 t1 == the low bits of the first source word
146 t6 == bytemask that is -1 in dest word bytes */
148 ldq_u t2, 8(a1) # e0 :
149 addq a1, 8, a1 # .. e1 :
151 extql t1, a1, t1 # e0 :
152 extqh t2, a1, t4 # e0 :
153 mskql t0, a0, t0 # e0 :
154 or t1, t4, t1 # .. e1 :
155 mskqh t1, a0, t1 # e0 :
159 cmpbge zero, t6, t7 # .. e1 :
160 lda t6, -1 # e0 : for masking just below
161 bne t7, $u_final # .. e1 :
163 mskql t6, a1, t6 # e0 : mask out the bits we have
164 or t6, t2, t2 # e1 : already extracted before
165 cmpbge zero, t2, t7 # e0 : testing eos
166 bne t7, $u_late_head_exit # .. e1 (zdb)
168 /* Finally, we've got all the stupid leading edge cases taken care
169 of and we can set up to enter the main loop. */
171 stq_u t1, 0(a0) # e0 : store first output word
172 addq a0, 8, a0 # .. e1 :
173 extql t2, a1, t0 # e0 : position ho-bits of lo word
174 ldq_u t2, 8(a1) # .. e1 : read next high-order source word
175 addq a1, 8, a1 # e0 :
176 cmpbge zero, t2, t7 # .. e1 :
178 bne t7, $u_eos # .. e1 :
180 /* Unaligned copy main loop. In order to avoid reading too much,
181 the loop is structured to detect zeros in aligned source words.
182 This has, unfortunately, effectively pulled half of a loop
183 iteration out into the head and half into the tail, but it does
184 prevent nastiness from accumulating in the very thing we want
185 to run as fast as possible.
187 On entry to this basic block:
188 t0 == the shifted high-order bits from the previous source word
189 t2 == the unshifted current source word
191 We further know that t2 does not contain a null terminator. */
195 extqh t2, a1, t1 # e0 : extract high bits for current word
196 addq a1, 8, a1 # .. e1 :
197 extql t2, a1, t3 # e0 : extract low bits for next time
198 addq a0, 8, a0 # .. e1 :
199 or t0, t1, t1 # e0 : current dst word now complete
200 ldq_u t2, 0(a1) # .. e1 : load high word for next time
201 stq_u t1, -8(a0) # e0 : save the current word
203 cmpbge zero, t2, t7 # e0 : test new word for eos
204 beq t7, $u_loop # .. e1 :
206 /* We've found a zero somewhere in the source word we just read.
207 If it resides in the lower half, we have one (probably partial)
208 word to write out, and if it resides in the upper half, we
209 have one full and one partial word left to write out.
211 On entry to this basic block:
212 t0 == the shifted high-order bits from the previous source word
213 t2 == the unshifted current source word. */
215 extqh t2, a1, t1 # e0 :
216 or t0, t1, t1 # e1 : first (partial) source word complete
218 cmpbge zero, t1, t7 # e0 : is the null in this first bit?
219 bne t7, $u_final # .. e1 (zdb)
222 stq_u t1, 0(a0) # e0 : the null was in the high-order bits
223 addq a0, 8, a0 # .. e1 :
224 extql t2, a1, t1 # e0 :
225 cmpbge zero, t1, t7 # .. e1 :
227 /* Take care of a final (probably partial) result word.
228 On entry to this basic block:
229 t1 == assembled source word
230 t7 == cmpbge mask that found the null. */
232 negq t7, t6 # e0 : isolate low bit set
233 and t6, t7, t8 # e1 :
235 and t8, 0x80, t6 # e0 : avoid dest word load if we can
236 bne t6, 1f # .. e1 (zdb)
238 ldq_u t0, 0(a0) # e0 :
239 subq t8, 1, t6 # .. e1 :
241 zapnot t1, t6, t1 # .. e1 : kill source bytes >= null
242 zap t0, t7, t0 # e0 : kill dest bytes <= null
245 1: stq_u t1, 0(a0) # e0 :
248 /* Unaligned copy entry point. */
252 ldq_u t1, 0(a1) # e0 : load first source word
254 and a0, 7, t4 # .. e1 : find dest misalignment
255 and a1, 7, t5 # e0 : find src misalignment
257 /* Conditionally load the first destination word and a bytemask
258 with 0xff indicating that the destination byte is sacrosanct. */
260 mov zero, t0 # .. e1 :
263 ldq_u t0, 0(a0) # e0 :
265 mskql t6, a0, t6 # e0 :
267 subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr
269 /* If source misalignment is larger than dest misalignment, we need
270 extra startup checks to avoid SEGV. */
272 cmplt t4, t5, t8 # e0 :
273 beq t8, $u_head # .. e1 (zdb)
275 lda t2, -1 # e1 : mask out leading garbage in source
276 mskqh t2, t5, t2 # e0 :
278 ornot t1, t2, t3 # .. e1 :
279 cmpbge zero, t3, t7 # e0 : is there a zero?
280 beq t7, $u_head # .. e1 (zdb)
282 /* At this point we've found a zero in the first partial word of
283 the source. We need to isolate the valid source data and mask
284 it into the original destination data. (Incidentally, we know
285 that we'll need at least one byte of that original dest word.) */
287 ldq_u t0, 0(a0) # e0 :
289 negq t7, t6 # .. e1 : build bitmask of bytes <= zero
290 and t6, t7, t8 # e0 :
291 and a1, 7, t5 # .. e1 :
292 subq t8, 1, t6 # e0 :
294 srl t8, t5, t8 # e0 : adjust final null return value
296 zapnot t2, t7, t2 # .. e1 : prepare source word; mirror changes
297 and t1, t2, t1 # e1 : to source validity mask
298 extql t2, a1, t2 # .. e0 :
299 extql t1, a1, t1 # e0 :
301 andnot t0, t2, t0 # .. e1 : zero place for source to reside
302 or t0, t1, t1 # e1 : and put it there
303 stq_u t1, 0(a0) # .. e0 :