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1 | /* Copyright (C) 1996-2019 Free Software Foundation, Inc. |
---|---|

2 | Contributed by Richard Henderson (rth@tamu.edu) |

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 | <http://www.gnu.org/licenses/>. */ |

18 | |

19 | /* Copy no more than COUNT bytes of the null-terminated string from |

20 | SRC to DST. |

21 | |

22 | This is an internal routine used by strncpy, stpncpy, and strncat. |

23 | As such, it uses special linkage conventions to make implementation |

24 | of these public functions more efficient. |

25 | |

26 | On input: |

27 | t9 = return address |

28 | a0 = DST |

29 | a1 = SRC |

30 | a2 = COUNT |

31 | |

32 | Furthermore, COUNT may not be zero. |

33 | |

34 | On output: |

35 | t0 = last word written |

36 | t8 = bitmask (with one bit set) indicating the last byte written |

37 | t10 = bitmask (with one bit set) indicating the byte position of |

38 | the end of the range specified by COUNT |

39 | a0 = unaligned address of the last *word* written |

40 | a2 = the number of full words left in COUNT |

41 | |

42 | Furthermore, v0, a3-a5, t11, and t12 are untouched. |

43 | */ |

44 | |

45 | |

46 | /* This is generally scheduled for the EV5, but should still be pretty |

47 | good for the EV4 too. */ |

48 | |

49 | #include <sysdep.h> |

50 | |

51 | .set noat |

52 | .set noreorder |

53 | |

54 | .text |

55 | .type __stxncpy, @function |

56 | .globl __stxncpy |

57 | .usepv __stxncpy, no |

58 | |

59 | cfi_startproc |

60 | cfi_return_column (t9) |

61 | |

62 | /* On entry to this basic block: |

63 | t0 == the first destination word for masking back in |

64 | t1 == the first source word. */ |

65 | .align 3 |

66 | stxncpy_aligned: |

67 | /* Create the 1st output word and detect 0's in the 1st input word. */ |

68 | lda t2, -1 # e1 : build a mask against false zero |

69 | mskqh t2, a1, t2 # e0 : detection in the src word |

70 | mskqh t1, a1, t3 # e0 : |

71 | ornot t1, t2, t2 # .. e1 : |

72 | mskql t0, a1, t0 # e0 : assemble the first output word |

73 | cmpbge zero, t2, t7 # .. e1 : bits set iff null found |

74 | or t0, t3, t0 # e0 : |

75 | beq a2, $a_eoc # .. e1 : |

76 | bne t7, $a_eos # .. e1 : |

77 | |

78 | /* On entry to this basic block: |

79 | t0 == a source word not containing a null. */ |

80 | $a_loop: |

81 | stq_u t0, 0(a0) # e0 : |

82 | addq a0, 8, a0 # .. e1 : |

83 | ldq_u t0, 0(a1) # e0 : |

84 | addq a1, 8, a1 # .. e1 : |

85 | subq a2, 1, a2 # e0 : |

86 | cmpbge zero, t0, t7 # .. e1 (stall) |

87 | beq a2, $a_eoc # e1 : |

88 | beq t7, $a_loop # e1 : |

89 | |

90 | /* Take care of the final (partial) word store. At this point |

91 | the end-of-count bit is set in t7 iff it applies. |

92 | |

93 | On entry to this basic block we have: |

94 | t0 == the source word containing the null |

95 | t7 == the cmpbge mask that found it. */ |

96 | $a_eos: |

97 | negq t7, t8 # e0 : find low bit set |

98 | and t7, t8, t8 # e1 (stall) |

99 | |

100 | /* For the sake of the cache, don't read a destination word |

101 | if we're not going to need it. */ |

102 | and t8, 0x80, t6 # e0 : |

103 | bne t6, 1f # .. e1 (zdb) |

104 | |

105 | /* We're doing a partial word store and so need to combine |

106 | our source and original destination words. */ |

107 | ldq_u t1, 0(a0) # e0 : |

108 | subq t8, 1, t6 # .. e1 : |

109 | or t8, t6, t7 # e0 : |

110 | unop # |

111 | zapnot t0, t7, t0 # e0 : clear src bytes > null |

112 | zap t1, t7, t1 # .. e1 : clear dst bytes <= null |

113 | or t0, t1, t0 # e1 : |

114 | |

115 | 1: stq_u t0, 0(a0) # e0 : |

116 | ret (t9) # e1 : |

117 | |

118 | /* Add the end-of-count bit to the eos detection bitmask. */ |

119 | $a_eoc: |

120 | or t10, t7, t7 |

121 | br $a_eos |

122 | |

123 | .align 3 |

124 | __stxncpy: |

125 | /* Are source and destination co-aligned? */ |

126 | lda t2, -1 |

127 | xor a0, a1, t1 |

128 | srl t2, 1, t2 |

129 | and a0, 7, t0 # find dest misalignment |

130 | cmovlt a2, t2, a2 # bound neg count to LONG_MAX |

131 | and t1, 7, t1 |

132 | addq a2, t0, a2 # bias count by dest misalignment |

133 | subq a2, 1, a2 |

134 | and a2, 7, t2 |

135 | srl a2, 3, a2 # a2 = loop counter = (count - 1)/8 |

136 | addq zero, 1, t10 |

137 | sll t10, t2, t10 # t10 = bitmask of last count byte |

138 | bne t1, $unaligned |

139 | |

140 | /* We are co-aligned; take care of a partial first word. */ |

141 | |

142 | ldq_u t1, 0(a1) # e0 : load first src word |

143 | addq a1, 8, a1 # .. e1 : |

144 | |

145 | beq t0, stxncpy_aligned # avoid loading dest word if not needed |

146 | ldq_u t0, 0(a0) # e0 : |

147 | br stxncpy_aligned # .. e1 : |

148 | |

149 | |

150 | /* The source and destination are not co-aligned. Align the destination |

151 | and cope. We have to be very careful about not reading too much and |

152 | causing a SEGV. */ |

153 | |

154 | .align 3 |

155 | $u_head: |

156 | /* We know just enough now to be able to assemble the first |

157 | full source word. We can still find a zero at the end of it |

158 | that prevents us from outputting the whole thing. |

159 | |

160 | On entry to this basic block: |

161 | t0 == the first dest word, unmasked |

162 | t1 == the shifted low bits of the first source word |

163 | t6 == bytemask that is -1 in dest word bytes */ |

164 | |

165 | ldq_u t2, 8(a1) # e0 : load second src word |

166 | addq a1, 8, a1 # .. e1 : |

167 | mskql t0, a0, t0 # e0 : mask trailing garbage in dst |

168 | extqh t2, a1, t4 # e0 : |

169 | or t1, t4, t1 # e1 : first aligned src word complete |

170 | mskqh t1, a0, t1 # e0 : mask leading garbage in src |

171 | or t0, t1, t0 # e0 : first output word complete |

172 | or t0, t6, t6 # e1 : mask original data for zero test |

173 | cmpbge zero, t6, t7 # e0 : |

174 | beq a2, $u_eocfin # .. e1 : |

175 | lda t6, -1 # e0 : |

176 | bne t7, $u_final # .. e1 : |

177 | |

178 | mskql t6, a1, t6 # e0 : mask out bits already seen |

179 | nop # .. e1 : |

180 | stq_u t0, 0(a0) # e0 : store first output word |

181 | or t6, t2, t2 # .. e1 : |

182 | cmpbge zero, t2, t7 # e0 : find nulls in second partial |

183 | addq a0, 8, a0 # .. e1 : |

184 | subq a2, 1, a2 # e0 : |

185 | bne t7, $u_late_head_exit # .. e1 : |

186 | |

187 | /* Finally, we've got all the stupid leading edge cases taken care |

188 | of and we can set up to enter the main loop. */ |

189 | |

190 | extql t2, a1, t1 # e0 : position hi-bits of lo word |

191 | beq a2, $u_eoc # .. e1 : |

192 | ldq_u t2, 8(a1) # e0 : read next high-order source word |

193 | addq a1, 8, a1 # .. e1 : |

194 | extqh t2, a1, t0 # e0 : position lo-bits of hi word |

195 | cmpbge zero, t2, t7 # .. e1 : test new word for eos |

196 | nop # e0 : |

197 | bne t7, $u_eos # .. e1 : |

198 | |

199 | /* Unaligned copy main loop. In order to avoid reading too much, |

200 | the loop is structured to detect zeros in aligned source words. |

201 | This has, unfortunately, effectively pulled half of a loop |

202 | iteration out into the head and half into the tail, but it does |

203 | prevent nastiness from accumulating in the very thing we want |

204 | to run as fast as possible. |

205 | |

206 | On entry to this basic block: |

207 | t0 == the shifted low-order bits from the current source word |

208 | t1 == the shifted high-order bits from the previous source word |

209 | t2 == the unshifted current source word |

210 | |

211 | We further know that t2 does not contain a null terminator. */ |

212 | |

213 | .align 3 |

214 | $u_loop: |

215 | or t0, t1, t0 # e0 : current dst word now complete |

216 | subq a2, 1, a2 # .. e1 : decrement word count |

217 | stq_u t0, 0(a0) # e0 : save the current word |

218 | addq a0, 8, a0 # .. e1 : |

219 | extql t2, a1, t1 # e0 : extract high bits for next time |

220 | beq a2, $u_eoc # .. e1 : |

221 | ldq_u t2, 8(a1) # e0 : load high word for next time |

222 | addq a1, 8, a1 # .. e1 : |

223 | nop # e0 : |

224 | cmpbge zero, t2, t7 # .. e1 : test new word for eos |

225 | extqh t2, a1, t0 # e0 : extract low bits for current word |

226 | beq t7, $u_loop # .. e1 : |

227 | |

228 | /* We've found a zero somewhere in the source word we just read. |

229 | If it resides in the lower half, we have one (probably partial) |

230 | word to write out, and if it resides in the upper half, we |

231 | have one full and one partial word left to write out. |

232 | |

233 | On entry to this basic block: |

234 | t0 == the shifted low-order bits from the current source word |

235 | t1 == the shifted high-order bits from the previous source word |

236 | t2 == the unshifted current source word. */ |

237 | $u_eos: |

238 | or t0, t1, t0 # e0 : first (partial) source word complete |

239 | cmpbge zero, t0, t7 # e0 : is the null in this first bit? |

240 | bne t7, $u_final # .. e1 (zdb) |

241 | |

242 | stq_u t0, 0(a0) # e0 : the null was in the high-order bits |

243 | addq a0, 8, a0 # .. e1 : |

244 | subq a2, 1, a2 # e0 : |

245 | |

246 | $u_late_head_exit: |

247 | extql t2, a1, t0 # e0 : |

248 | cmpbge zero, t0, t7 # e0 : |

249 | or t7, t10, t6 # e1 : |

250 | cmoveq a2, t6, t7 # e0 : |

251 | |

252 | /* Take care of a final (probably partial) result word. |

253 | On entry to this basic block: |

254 | t0 == assembled source word |

255 | t7 == cmpbge mask that found the null. */ |

256 | $u_final: |

257 | negq t7, t6 # e0 : isolate low bit set |

258 | and t6, t7, t8 # e1 : |

259 | |

260 | and t8, 0x80, t6 # e0 : avoid dest word load if we can |

261 | bne t6, 1f # .. e1 (zdb) |

262 | |

263 | ldq_u t1, 0(a0) # e0 : |

264 | subq t8, 1, t6 # .. e1 : |

265 | or t6, t8, t7 # e0 : |

266 | zapnot t0, t7, t0 # .. e1 : kill source bytes > null |

267 | zap t1, t7, t1 # e0 : kill dest bytes <= null |

268 | or t0, t1, t0 # e1 : |

269 | |

270 | 1: stq_u t0, 0(a0) # e0 : |

271 | ret (t9) # .. e1 : |

272 | |

273 | /* Got to end-of-count before end of string. |

274 | On entry to this basic block: |

275 | t1 == the shifted high-order bits from the previous source word */ |

276 | $u_eoc: |

277 | and a1, 7, t6 # e1 : |

278 | sll t10, t6, t6 # e0 : |

279 | and t6, 0xff, t6 # e0 : |

280 | bne t6, 1f # e1 : avoid src word load if we can |

281 | |

282 | ldq_u t2, 8(a1) # e0 : load final src word |

283 | nop # .. e1 : |

284 | extqh t2, a1, t0 # e0 : extract high bits for last word |

285 | or t1, t0, t1 # e1 : |

286 | |

287 | 1: cmpbge zero, t1, t7 |

288 | mov t1, t0 |

289 | |

290 | $u_eocfin: # end-of-count, final word |

291 | or t10, t7, t7 |

292 | br $u_final |

293 | |

294 | /* Unaligned copy entry point. */ |

295 | .align 3 |

296 | $unaligned: |

297 | |

298 | ldq_u t1, 0(a1) # e0 : load first source word |

299 | |

300 | and a0, 7, t4 # .. e1 : find dest misalignment |

301 | and a1, 7, t5 # e0 : find src misalignment |

302 | |

303 | /* Conditionally load the first destination word and a bytemask |

304 | with 0xff indicating that the destination byte is sacrosanct. */ |

305 | |

306 | mov zero, t0 # .. e1 : |

307 | mov zero, t6 # e0 : |

308 | beq t4, 1f # .. e1 : |

309 | ldq_u t0, 0(a0) # e0 : |

310 | lda t6, -1 # .. e1 : |

311 | mskql t6, a0, t6 # e0 : |

312 | 1: |

313 | subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr |

314 | |

315 | /* If source misalignment is larger than dest misalignment, we need |

316 | extra startup checks to avoid SEGV. */ |

317 | |

318 | cmplt t4, t5, t8 # e1 : |

319 | extql t1, a1, t1 # .. e0 : shift src into place |

320 | lda t2, -1 # e0 : for creating masks later |

321 | beq t8, $u_head # e1 : |

322 | |

323 | mskqh t2, t5, t2 # e0 : begin src byte validity mask |

324 | cmpbge zero, t1, t7 # .. e1 : is there a zero? |

325 | extql t2, a1, t2 # e0 : |

326 | or t7, t10, t5 # .. e1 : test for end-of-count too |

327 | cmpbge zero, t2, t3 # e0 : |

328 | cmoveq a2, t5, t7 # .. e1 : |

329 | andnot t7, t3, t7 # e0 : |

330 | beq t7, $u_head # .. e1 (zdb) |

331 | |

332 | /* At this point we've found a zero in the first partial word of |

333 | the source. We need to isolate the valid source data and mask |

334 | it into the original destination data. (Incidentally, we know |

335 | that we'll need at least one byte of that original dest word.) */ |

336 | |

337 | ldq_u t0, 0(a0) # e0 : |

338 | negq t7, t6 # .. e1 : build bitmask of bytes <= zero |

339 | mskqh t1, t4, t1 # e0 : |

340 | and t6, t7, t8 # .. e1 : |

341 | subq t8, 1, t6 # e0 : |

342 | or t6, t8, t7 # e1 : |

343 | |

344 | zapnot t2, t7, t2 # e0 : prepare source word; mirror changes |

345 | zapnot t1, t7, t1 # .. e1 : to source validity mask |

346 | |

347 | andnot t0, t2, t0 # e0 : zero place for source to reside |

348 | or t0, t1, t0 # e1 : and put it there |

349 | stq_u t0, 0(a0) # e0 : |

350 | ret (t9) # .. e1 : |

351 | |

352 | cfi_endproc |

353 |

Warning: That file was not part of the compilation database. It may have many parsing errors.