1/* Copyright (C) 2000-2022 Free Software Foundation, Inc. 2 This file is part of the GNU C Library. 3 4 The GNU C Library is free software; you can redistribute it and/or 5 modify it under the terms of the GNU Lesser General Public 6 License as published by the Free Software Foundation; either 7 version 2.1 of the License, or (at your option) any later version. 8 9 The GNU C Library is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 Lesser General Public License for more details. 13 14 You should have received a copy of the GNU Lesser General Public 15 License along with the GNU C Library. If not, see 16 <https://www.gnu.org/licenses/>. */ 17 18/* Copy no more than COUNT bytes of the null-terminated string from 19 SRC to DST. 20 21 This is an internal routine used by strncpy, stpncpy, and strncat. 22 As such, it uses special linkage conventions to make implementation 23 of these public functions more efficient. 24 25 On input: 26 t9 = return address 27 a0 = DST 28 a1 = SRC 29 a2 = COUNT 30 31 Furthermore, COUNT may not be zero. 32 33 On output: 34 t0 = last word written 35 t8 = bitmask (with one bit set) indicating the last byte written 36 t10 = bitmask (with one bit set) indicating the byte position of 37 the end of the range specified by COUNT 38 a0 = unaligned address of the last *word* written 39 a2 = the number of full words left in COUNT 40 41 Furthermore, v0, a3-a5, t11, and t12 are untouched. 42*/ 43 44#include <sysdep.h> 45 46 .arch ev6 47 .set noat 48 .set noreorder 49 50 .text 51 .type __stxncpy, @function 52 .globl __stxncpy 53 .usepv __stxncpy, no 54 55 cfi_startproc 56 cfi_return_column (t9) 57 58 /* On entry to this basic block: 59 t0 == the first destination word for masking back in 60 t1 == the first source word. */ 61 .align 4 62stxncpy_aligned: 63 /* Create the 1st output word and detect 0's in the 1st input word. */ 64 lda t2, -1 # E : build a mask against false zero 65 mskqh t2, a1, t2 # U : detection in the src word (stall) 66 mskqh t1, a1, t3 # U : 67 ornot t1, t2, t2 # E : (stall) 68 69 mskql t0, a1, t0 # U : assemble the first output word 70 cmpbge zero, t2, t7 # E : bits set iff null found 71 or t0, t3, t0 # E : (stall) 72 beq a2, $a_eoc # U : 73 74 bne t7, $a_eos # U : 75 nop 76 nop 77 nop 78 79 /* On entry to this basic block: 80 t0 == a source word not containing a null. */ 81 82 /* 83 * nops here to: 84 * separate store quads from load quads 85 * limit of 1 bcond/quad to permit training 86 */ 87$a_loop: 88 stq_u t0, 0(a0) # L : 89 addq a0, 8, a0 # E : 90 subq a2, 1, a2 # E : 91 nop 92 93 ldq_u t0, 0(a1) # L : 94 addq a1, 8, a1 # E : 95 cmpbge zero, t0, t7 # E : 96 beq a2, $a_eoc # U : 97 98 beq t7, $a_loop # U : 99 nop 100 nop 101 nop 102 103 /* Take care of the final (partial) word store. At this point 104 the end-of-count bit is set in t7 iff it applies. 105 106 On entry to this basic block we have: 107 t0 == the source word containing the null 108 t7 == the cmpbge mask that found it. */ 109$a_eos: 110 negq t7, t8 # E : find low bit set 111 and t7, t8, t8 # E : (stall) 112 /* For the sake of the cache, don't read a destination word 113 if we're not going to need it. */ 114 and t8, 0x80, t6 # E : (stall) 115 bne t6, 1f # U : (stall) 116 117 /* We're doing a partial word store and so need to combine 118 our source and original destination words. */ 119 ldq_u t1, 0(a0) # L : 120 subq t8, 1, t6 # E : 121 or t8, t6, t7 # E : (stall) 122 zapnot t0, t7, t0 # U : clear src bytes > null (stall) 123 124 zap t1, t7, t1 # .. e1 : clear dst bytes <= null 125 or t0, t1, t0 # e1 : (stall) 126 nop 127 nop 128 1291: stq_u t0, 0(a0) # L : 130 ret (t9) # L0 : Latency=3 131 nop 132 nop 133 134 /* Add the end-of-count bit to the eos detection bitmask. */ 135$a_eoc: 136 or t10, t7, t7 # E : 137 br $a_eos # L0 : Latency=3 138 nop 139 nop 140 141 .align 4 142__stxncpy: 143 /* Are source and destination co-aligned? */ 144 lda t2, -1 # E : 145 xor a0, a1, t1 # E : 146 and a0, 7, t0 # E : find dest misalignment 147 nop # E : 148 149 srl t2, 1, t2 # U : 150 and t1, 7, t1 # E : 151 cmovlt a2, t2, a2 # E : bound count to LONG_MAX (stall) 152 nop # E : 153 154 addq a2, t0, a2 # E : bias count by dest misalignment 155 subq a2, 1, a2 # E : (stall) 156 and a2, 7, t2 # E : (stall) 157 lda t10, 1 # E : 158 159 srl a2, 3, a2 # U : a2 = loop counter = (count - 1)/8 160 sll t10, t2, t10 # U : t10 = bitmask of last count byte 161 nop # E : 162 bne t1, $unaligned # U : (stall) 163 164 /* We are co-aligned; take care of a partial first word. */ 165 ldq_u t1, 0(a1) # L : load first src word 166 addq a1, 8, a1 # E : 167 beq t0, stxncpy_aligned # U : avoid loading dest word if not needed 168 ldq_u t0, 0(a0) # L : 169 170 br stxncpy_aligned # U : 171 nop 172 nop 173 nop 174 175 176 177/* The source and destination are not co-aligned. Align the destination 178 and cope. We have to be very careful about not reading too much and 179 causing a SEGV. */ 180 181 .align 4 182$u_head: 183 /* We know just enough now to be able to assemble the first 184 full source word. We can still find a zero at the end of it 185 that prevents us from outputting the whole thing. 186 187 On entry to this basic block: 188 t0 == the first dest word, unmasked 189 t1 == the shifted low bits of the first source word 190 t6 == bytemask that is -1 in dest word bytes */ 191 192 ldq_u t2, 8(a1) # L : Latency=3 load second src word 193 addq a1, 8, a1 # E : 194 mskql t0, a0, t0 # U : mask trailing garbage in dst 195 extqh t2, a1, t4 # U : (3 cycle stall on t2) 196 197 or t1, t4, t1 # E : first aligned src word complete (stall) 198 mskqh t1, a0, t1 # U : mask leading garbage in src (stall) 199 or t0, t1, t0 # E : first output word complete (stall) 200 or t0, t6, t6 # E : mask original data for zero test (stall) 201 202 cmpbge zero, t6, t7 # E : 203 beq a2, $u_eocfin # U : 204 lda t6, -1 # E : 205 nop 206 207 bne t7, $u_final # U : 208 mskql t6, a1, t6 # U : mask out bits already seen 209 stq_u t0, 0(a0) # L : store first output word 210 or t6, t2, t2 # E : 211 212 cmpbge zero, t2, t7 # E : find nulls in second partial 213 addq a0, 8, a0 # E : 214 subq a2, 1, a2 # E : 215 bne t7, $u_late_head_exit # U : 216 217 /* Finally, we've got all the stupid leading edge cases taken care 218 of and we can set up to enter the main loop. */ 219 extql t2, a1, t1 # U : position hi-bits of lo word 220 beq a2, $u_eoc # U : 221 ldq_u t2, 8(a1) # L : read next high-order source word 222 addq a1, 8, a1 # E : 223 224 extqh t2, a1, t0 # U : position lo-bits of hi word (stall) 225 cmpbge zero, t2, t7 # E : 226 nop 227 bne t7, $u_eos # U : 228 229 /* Unaligned copy main loop. In order to avoid reading too much, 230 the loop is structured to detect zeros in aligned source words. 231 This has, unfortunately, effectively pulled half of a loop 232 iteration out into the head and half into the tail, but it does 233 prevent nastiness from accumulating in the very thing we want 234 to run as fast as possible. 235 236 On entry to this basic block: 237 t0 == the shifted low-order bits from the current source word 238 t1 == the shifted high-order bits from the previous source word 239 t2 == the unshifted current source word 240 241 We further know that t2 does not contain a null terminator. */ 242 243 .align 4 244$u_loop: 245 or t0, t1, t0 # E : current dst word now complete 246 subq a2, 1, a2 # E : decrement word count 247 extql t2, a1, t1 # U : extract high bits for next time 248 addq a0, 8, a0 # E : 249 250 stq_u t0, -8(a0) # L : save the current word 251 beq a2, $u_eoc # U : 252 ldq_u t2, 8(a1) # L : Latency=3 load high word for next time 253 addq a1, 8, a1 # E : 254 255 extqh t2, a1, t0 # U : extract low bits (2 cycle stall) 256 cmpbge zero, t2, t7 # E : test new word for eos 257 nop 258 beq t7, $u_loop # U : 259 260 /* We've found a zero somewhere in the source word we just read. 261 If it resides in the lower half, we have one (probably partial) 262 word to write out, and if it resides in the upper half, we 263 have one full and one partial word left to write out. 264 265 On entry to this basic block: 266 t0 == the shifted low-order bits from the current source word 267 t1 == the shifted high-order bits from the previous source word 268 t2 == the unshifted current source word. */ 269$u_eos: 270 or t0, t1, t0 # E : first (partial) source word complete 271 nop 272 cmpbge zero, t0, t7 # E : is the null in this first bit? (stall) 273 bne t7, $u_final # U : (stall) 274 275 stq_u t0, 0(a0) # L : the null was in the high-order bits 276 addq a0, 8, a0 # E : 277 subq a2, 1, a2 # E : 278 nop 279 280$u_late_head_exit: 281 extql t2, a1, t0 # U : 282 cmpbge zero, t0, t7 # E : 283 or t7, t10, t6 # E : (stall) 284 cmoveq a2, t6, t7 # E : Latency=2, extra map slot (stall) 285 286 /* Take care of a final (probably partial) result word. 287 On entry to this basic block: 288 t0 == assembled source word 289 t7 == cmpbge mask that found the null. */ 290$u_final: 291 negq t7, t6 # E : isolate low bit set 292 and t6, t7, t8 # E : (stall) 293 and t8, 0x80, t6 # E : avoid dest word load if we can (stall) 294 bne t6, 1f # U : (stall) 295 296 ldq_u t1, 0(a0) # L : 297 subq t8, 1, t6 # E : 298 or t6, t8, t7 # E : (stall) 299 zapnot t0, t7, t0 # U : kill source bytes > null 300 301 zap t1, t7, t1 # U : kill dest bytes <= null 302 or t0, t1, t0 # E : (stall) 303 nop 304 nop 305 3061: stq_u t0, 0(a0) # L : 307 ret (t9) # L0 : Latency=3 308 309 /* Got to end-of-count before end of string. 310 On entry to this basic block: 311 t1 == the shifted high-order bits from the previous source word */ 312$u_eoc: 313 and a1, 7, t6 # E : 314 sll t10, t6, t6 # U : (stall) 315 and t6, 0xff, t6 # E : (stall) 316 bne t6, 1f # U : (stall) 317 318 ldq_u t2, 8(a1) # L : load final src word 319 nop 320 extqh t2, a1, t0 # U : extract low bits for last word (stall) 321 or t1, t0, t1 # E : (stall) 322 3231: cmpbge zero, t1, t7 # E : 324 mov t1, t0 325 326$u_eocfin: # end-of-count, final word 327 or t10, t7, t7 # E : 328 br $u_final # L0 : Latency=3 329 330 /* Unaligned copy entry point. */ 331 .align 4 332$unaligned: 333 334 ldq_u t1, 0(a1) # L : load first source word 335 and a0, 7, t4 # E : find dest misalignment 336 and a1, 7, t5 # E : find src misalignment 337 /* Conditionally load the first destination word and a bytemask 338 with 0xff indicating that the destination byte is sacrosanct. */ 339 mov zero, t0 # E : 340 341 mov zero, t6 # E : 342 beq t4, 1f # U : 343 ldq_u t0, 0(a0) # L : 344 lda t6, -1 # E : 345 346 mskql t6, a0, t6 # U : 347 nop 348 nop 3491: subq a1, t4, a1 # E : sub dest misalignment from src addr 350 351 /* If source misalignment is larger than dest misalignment, we need 352 extra startup checks to avoid SEGV. */ 353 354 cmplt t4, t5, t8 # E : 355 extql t1, a1, t1 # U : shift src into place 356 lda t2, -1 # E : for creating masks later 357 beq t8, $u_head # U : (stall) 358 359 mskqh t2, t5, t2 # U : begin src byte validity mask 360 cmpbge zero, t1, t7 # E : is there a zero? 361 extql t2, a1, t2 # U : 362 or t7, t10, t5 # E : test for end-of-count too 363 364 cmpbge zero, t2, t3 # E : 365 cmoveq a2, t5, t7 # E : Latency=2, extra map slot 366 nop # E : keep with cmoveq 367 andnot t7, t3, t7 # E : (stall) 368 369 beq t7, $u_head # U : 370 /* At this point we've found a zero in the first partial word of 371 the source. We need to isolate the valid source data and mask 372 it into the original destination data. (Incidentally, we know 373 that we'll need at least one byte of that original dest word.) */ 374 ldq_u t0, 0(a0) # L : 375 negq t7, t6 # E : build bitmask of bytes <= zero 376 mskqh t1, t4, t1 # U : 377 378 and t6, t7, t8 # E : 379 subq t8, 1, t6 # E : (stall) 380 or t6, t8, t7 # E : (stall) 381 zapnot t2, t7, t2 # U : prepare source word; mirror changes (stall) 382 383 zapnot t1, t7, t1 # U : to source validity mask 384 andnot t0, t2, t0 # E : zero place for source to reside 385 or t0, t1, t0 # E : and put it there (stall both t0, t1) 386 stq_u t0, 0(a0) # L : (stall) 387 388 ret (t9) # L0 : Latency=3 389 390 cfi_endproc 391