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| 1 | /* | ||
| 2 | * Copyright (c) 1996, 2003, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package sun.tools.tree; | ||
| 27 | |||
| 28 | import sun.tools.java.*; | ||
| 29 | |||
| 30 | /** | ||
| 31 | * WARNING: The contents of this source file are not part of any | ||
| 32 | * supported API. Code that depends on them does so at its own risk: | ||
| 33 | * they are subject to change or removal without notice. | ||
| 34 | */ | ||
| 35 | public final | ||
| 36 | class Vset implements Constants { | ||
| 37 | long vset; // DA bits for first 64 variables | ||
| 38 | long uset; // DU bits for first 64 variables | ||
| 39 | |||
| 40 | // The extension array is interleaved, consisting of alternating | ||
| 41 | // blocks of 64 DA bits followed by 64 DU bits followed by 64 DA | ||
| 42 | // bits, and so on. | ||
| 43 | |||
| 44 | long x[]; // extension array for more bits | ||
| 45 | |||
| 46 | // An infinite vector of zeroes or an infinite vector of ones is | ||
| 47 | // represented by a special value of the extension array. | ||
| 48 | // | ||
| 49 | // IMPORTANT: The condition 'this.x == fullX' is used as a marker for | ||
| 50 | // unreachable code, i.e., for a dead-end. We maintain the invariant | ||
| 51 | // that (this.x != fullX || (this.vset == -1 && this.uset == -1)). | ||
| 52 | // A dead-end has the peculiar property that all variables are both | ||
| 53 | // definitely assigned and definitely unassigned. We always force this | ||
| 54 | // condition to hold, even when the normal bitvector operations performed | ||
| 55 | // during DA/DU analysis would produce a different result. This supresses | ||
| 56 | // reporting of DA/DU errors in unreachable code. | ||
| 57 | |||
| 58 | static final long emptyX[] = new long[0]; // all zeroes | ||
| 59 | static final long fullX[] = new long[0]; // all ones | ||
| 60 | |||
| 61 | // For more thorough testing of long vset support, it is helpful to | ||
| 62 | // temporarily redefine this value to a smaller number, such as 1 or 2. | ||
| 63 | |||
| 64 | static final int VBITS = 64; // number of bits in vset (uset) | ||
| 65 | |||
| 66 | /** | ||
| 67 | * This is the Vset which reports all vars assigned and unassigned. | ||
| 68 | * This impossibility is degenerately true exactly when | ||
| 69 | * control flow cannot reach this point. | ||
| 70 | */ | ||
| 71 | |||
| 72 | // We distinguish a canonical dead-end value generated initially for | ||
| 73 | // statements that do not complete normally, making the next one unreachable. | ||
| 74 | // Once an unreachable statement is reported, a non-canonical dead-end value | ||
| 75 | // is used for subsequent statements in order to suppress redundant error | ||
| 76 | // messages. | ||
| 77 | |||
| 78 | static final Vset DEAD_END = new Vset(-1, -1, fullX); | ||
| 79 | |||
| 80 | /** | ||
| 81 | * Create an empty Vset. | ||
| 82 | */ | ||
| 83 | public Vset() { | ||
| 84 | this.x = emptyX; | ||
| 85 | } | ||
| 86 | |||
| 87 | private Vset(long vset, long uset, long x[]) { | ||
| 88 | this.vset = vset; | ||
| 89 | this.uset = uset; | ||
| 90 | this.x = x; | ||
| 91 | } | ||
| 92 | |||
| 93 | /** | ||
| 94 | * Create an copy of the given Vset. | ||
| 95 | * (However, DEAD_END simply returns itself.) | ||
| 96 | */ | ||
| 97 | public Vset copy() { | ||
| 98 | if (this == DEAD_END) { | ||
| 99 | return this; | ||
| 100 | } | ||
| 101 | Vset vs = new Vset(vset, uset, x); | ||
| 102 | if (x.length > 0) { | ||
| 103 | vs.growX(x.length); // recopy the extension vector | ||
| 104 | } | ||
| 105 | return vs; | ||
| 106 | } | ||
| 107 | |||
| 108 | private void growX(int length) { | ||
| 109 | long newX[] = new long[length]; | ||
| 110 | long oldX[] = x; | ||
| 111 | for (int i = 0; i < oldX.length; i++) { | ||
| 112 | newX[i] = oldX[i]; | ||
| 113 | } | ||
| 114 | x = newX; | ||
| 115 | } | ||
| 116 | |||
| 117 | /** | ||
| 118 | * Ask if this is a vset for a dead end. | ||
| 119 | * Answer true only for the canonical dead-end, DEAD_END. | ||
| 120 | * A canonical dead-end is produced only as a result of | ||
| 121 | * a statement that cannot complete normally, as specified | ||
| 122 | * by the JLS. Due to the special-case rules for if-then | ||
| 123 | * and if-then-else, this may fail to detect actual unreachable | ||
| 124 | * code that could easily be identified. | ||
| 125 | */ | ||
| 126 | |||
| 127 | public boolean isDeadEnd() { | ||
| 128 | return (this == DEAD_END); | ||
| 129 | } | ||
| 130 | |||
| 131 | /** | ||
| 132 | * Ask if this is a vset for a dead end. | ||
| 133 | * Answer true for any dead-end. | ||
| 134 | * Since 'clearDeadEnd' has no effect on this predicate, | ||
| 135 | * if-then and if-then-else are handled in the more 'obvious' | ||
| 136 | * and precise way. This predicate is to be preferred for | ||
| 137 | * dead code elimination purposes. | ||
| 138 | * (Presently used in workaround for bug 4173473 in MethodExpression.java) | ||
| 139 | */ | ||
| 140 | public boolean isReallyDeadEnd() { | ||
| 141 | return (x == fullX); | ||
| 142 | } | ||
| 143 | |||
| 144 | /** | ||
| 145 | * Replace canonical DEAD_END with a distinct but | ||
| 146 | * equivalent Vset. The bits are unaltered, but | ||
| 147 | * the result does not answer true to 'isDeadEnd'. | ||
| 148 | * <p> | ||
| 149 | * Used mostly for error recovery, but see | ||
| 150 | * 'IfStatement.check', where it is used to | ||
| 151 | * implement the special-case treatment of | ||
| 152 | * statement reachability for such statements. | ||
| 153 | */ | ||
| 154 | public Vset clearDeadEnd() { | ||
| 155 | if (this == DEAD_END) { | ||
| 156 | return new Vset(-1, -1, fullX); | ||
| 157 | } | ||
| 158 | return this; | ||
| 159 | } | ||
| 160 | |||
| 161 | /** | ||
| 162 | * Ask if a var is definitely assigned. | ||
| 163 | */ | ||
| 164 | public boolean testVar(int varNumber) { | ||
| 165 | long bit = (1L << varNumber); | ||
| 166 | if (varNumber >= VBITS) { | ||
| 167 | int i = (varNumber / VBITS - 1) * 2; | ||
| 168 | if (i >= x.length) { | ||
| 169 | return (x == fullX); | ||
| 170 | } | ||
| 171 | return (x[i] & bit) != 0; | ||
| 172 | } else { | ||
| 173 | return (vset & bit) != 0; | ||
| 174 | } | ||
| 175 | } | ||
| 176 | |||
| 177 | /** | ||
| 178 | * Ask if a var is definitely un-assigned. | ||
| 179 | * (This is not just the negation of testVar: | ||
| 180 | * It's possible for neither to be true.) | ||
| 181 | */ | ||
| 182 | public boolean testVarUnassigned(int varNumber) { | ||
| 183 | long bit = (1L << varNumber); | ||
| 184 | if (varNumber >= VBITS) { | ||
| 185 | // index "uset" extension | ||
| 186 | int i = ((varNumber / VBITS - 1) * 2) + 1; | ||
| 187 | if (i >= x.length) { | ||
| 188 | return (x == fullX); | ||
| 189 | } | ||
| 190 | return (x[i] & bit) != 0; | ||
| 191 | } else { | ||
| 192 | return (uset & bit) != 0; | ||
| 193 | } | ||
| 194 | } | ||
| 195 | |||
| 196 | /** | ||
| 197 | * Note that a var is definitely assigned. | ||
| 198 | * (Side-effecting.) | ||
| 199 | */ | ||
| 200 | public Vset addVar(int varNumber) { | ||
| 201 | if (x == fullX) { | ||
| 202 | return this; | ||
| 203 | } | ||
| 204 | |||
| 205 | // gen DA, kill DU | ||
| 206 | |||
| 207 | long bit = (1L << varNumber); | ||
| 208 | if (varNumber >= VBITS) { | ||
| 209 | int i = (varNumber / VBITS - 1) * 2; | ||
| 210 | if (i >= x.length) { | ||
| 211 | growX(i+1); | ||
| 212 | } | ||
| 213 | x[i] |= bit; | ||
| 214 | if (i+1 < x.length) { | ||
| 215 | x[i+1] &=~ bit; | ||
| 216 | } | ||
| 217 | } else { | ||
| 218 | vset |= bit; | ||
| 219 | uset &=~ bit; | ||
| 220 | } | ||
| 221 | return this; | ||
| 222 | } | ||
| 223 | |||
| 224 | /** | ||
| 225 | * Note that a var is definitely un-assigned. | ||
| 226 | * (Side-effecting.) | ||
| 227 | */ | ||
| 228 | public Vset addVarUnassigned(int varNumber) { | ||
| 229 | if (x == fullX) { | ||
| 230 | return this; | ||
| 231 | } | ||
| 232 | |||
| 233 | // gen DU, kill DA | ||
| 234 | |||
| 235 | long bit = (1L << varNumber); | ||
| 236 | if (varNumber >= VBITS) { | ||
| 237 | // index "uset" extension | ||
| 238 | int i = ((varNumber / VBITS - 1) * 2) + 1; | ||
| 239 | if (i >= x.length) { | ||
| 240 | growX(i+1); | ||
| 241 | } | ||
| 242 | x[i] |= bit; | ||
| 243 | x[i-1] &=~ bit; | ||
| 244 | } else { | ||
| 245 | uset |= bit; | ||
| 246 | vset &=~ bit; | ||
| 247 | } | ||
| 248 | return this; | ||
| 249 | } | ||
| 250 | |||
| 251 | /** | ||
| 252 | * Retract any assertion about the var. | ||
| 253 | * This operation is ineffective on a dead-end. | ||
| 254 | * (Side-effecting.) | ||
| 255 | */ | ||
| 256 | public Vset clearVar(int varNumber) { | ||
| 257 | if (x == fullX) { | ||
| 258 | return this; | ||
| 259 | } | ||
| 260 | long bit = (1L << varNumber); | ||
| 261 | if (varNumber >= VBITS) { | ||
| 262 | int i = (varNumber / VBITS - 1) * 2; | ||
| 263 | if (i >= x.length) { | ||
| 264 | return this; | ||
| 265 | } | ||
| 266 | x[i] &=~ bit; | ||
| 267 | if (i+1 < x.length) { | ||
| 268 | x[i+1] &=~ bit; | ||
| 269 | } | ||
| 270 | } else { | ||
| 271 | vset &=~ bit; | ||
| 272 | uset &=~ bit; | ||
| 273 | } | ||
| 274 | return this; | ||
| 275 | } | ||
| 276 | |||
| 277 | /** | ||
| 278 | * Join with another vset. This is set intersection. | ||
| 279 | * (Side-effecting.) | ||
| 280 | */ | ||
| 281 | public Vset join(Vset other) { | ||
| 282 | |||
| 283 | // Return a dead-end if both vsets are dead-ends. | ||
| 284 | // Return the canonical DEAD_END only if both vsets | ||
| 285 | // are the canonical DEAD_END. Otherwise, an incoming | ||
| 286 | // dead-end vset has already produced an error message, | ||
| 287 | // and is now assumed to be reachable. | ||
| 288 | if (this == DEAD_END) { | ||
| 289 | return other.copy(); | ||
| 290 | } | ||
| 291 | if (other == DEAD_END) { | ||
| 292 | return this; | ||
| 293 | } | ||
| 294 | if (x == fullX) { | ||
| 295 | return other.copy(); | ||
| 296 | } | ||
| 297 | if (other.x == fullX) { | ||
| 298 | return this; | ||
| 299 | } | ||
| 300 | |||
| 301 | // DA = DA intersection DA | ||
| 302 | // DU = DU intersection DU | ||
| 303 | |||
| 304 | vset &= other.vset; | ||
| 305 | uset &= other.uset; | ||
| 306 | |||
| 307 | if (other.x == emptyX) { | ||
| 308 | x = emptyX; | ||
| 309 | } else { | ||
| 310 | // ASSERT(otherX.length > 0); | ||
| 311 | long otherX[] = other.x; | ||
| 312 | int selfLength = x.length; | ||
| 313 | int limit = (otherX.length < selfLength) ? otherX.length : selfLength; | ||
| 314 | for (int i = 0; i < limit; i++) { | ||
| 315 | x[i] &= otherX[i]; | ||
| 316 | } | ||
| 317 | // If self is longer than other, all remaining | ||
| 318 | // bits are implicitly 0. In the result, then, | ||
| 319 | // the remaining DA and DU bits are cleared. | ||
| 320 | for (int i = limit; i < selfLength; i++) { | ||
| 321 | x[i] = 0; | ||
| 322 | } | ||
| 323 | } | ||
| 324 | return this; | ||
| 325 | } | ||
| 326 | |||
| 327 | /** | ||
| 328 | * Add in the definite assignment bits of another vset, | ||
| 329 | * but join the definite unassignment bits. This unusual | ||
| 330 | * operation is used only for 'finally' blocks. The | ||
| 331 | * original vset 'this' is destroyed by this operation. | ||
| 332 | * (Part of fix for 4068688.) | ||
| 333 | */ | ||
| 334 | |||
| 335 | public Vset addDAandJoinDU(Vset other) { | ||
| 336 | |||
| 337 | // Return a dead-end if either vset is a dead end. | ||
| 338 | // If either vset is the canonical DEAD_END, the | ||
| 339 | // result is also the canonical DEAD_END. | ||
| 340 | if (this == DEAD_END) { | ||
| 341 | return this; | ||
| 342 | } | ||
| 343 | if (other == DEAD_END) { | ||
| 344 | return other; | ||
| 345 | } | ||
| 346 | if (x == fullX) { | ||
| 347 | return this; | ||
| 348 | } | ||
| 349 | if (other.x == fullX) { | ||
| 350 | return other.copy(); | ||
| 351 | } | ||
| 352 | |||
| 353 | // DA = DA union DA' | ||
| 354 | // DU = (DU intersection DU') - DA' | ||
| 355 | |||
| 356 | vset = vset | other.vset; | ||
| 357 | uset = (uset & other.uset) & ~other.vset; | ||
| 358 | |||
| 359 | int selfLength = x.length; | ||
| 360 | long otherX[] = other.x; | ||
| 361 | int otherLength = otherX.length; | ||
| 362 | |||
| 363 | if (otherX != emptyX) { | ||
| 364 | // ASSERT(otherX.length > 0); | ||
| 365 | if (otherLength > selfLength) { | ||
| 366 | growX(otherLength); | ||
| 367 | } | ||
| 368 | int i = 0; | ||
| 369 | while (i < otherLength) { | ||
| 370 | x[i] |= otherX[i]; | ||
| 371 | i++; | ||
| 372 | if (i == otherLength) break; | ||
| 373 | x[i] = ((x[i] & otherX[i]) & ~otherX[i-1]); | ||
| 374 | i++; | ||
| 375 | } | ||
| 376 | } | ||
| 377 | // If self is longer than other, all remaining | ||
| 378 | // bits are implicitly 0. In the result, then, | ||
| 379 | // the remaining DA bits are left unchanged, and | ||
| 380 | // the DU bits are all cleared. First, align | ||
| 381 | // index to the next block of DU bits (odd index). | ||
| 382 | for (int i = (otherLength | 1); i < selfLength; i += 2) { | ||
| 383 | x[i] = 0; | ||
| 384 | } | ||
| 385 | return this; | ||
| 386 | } | ||
| 387 | |||
| 388 | |||
| 389 | /** | ||
| 390 | * Construct a vset consisting of the DA bits of the first argument | ||
| 391 | * and the DU bits of the second argument. This is a higly unusual | ||
| 392 | * operation, as it implies a case where the flowgraph for DA analysis | ||
| 393 | * differs from that for DU analysis. It is only needed for analysing | ||
| 394 | * 'try' blocks. The result is a dead-end iff the first argument is | ||
| 395 | * dead-end. (Part of fix for 4068688.) | ||
| 396 | */ | ||
| 397 | |||
| 398 | public static Vset firstDAandSecondDU(Vset sourceDA, Vset sourceDU) { | ||
| 399 | |||
| 400 | // Note that reachability status is received via 'sourceDA' only! | ||
| 401 | // This is a consequence of the fact that reachability and DA | ||
| 402 | // analysis are performed on an identical flow graph, whereas the | ||
| 403 | // flowgraph for DU analysis differs in the case of a 'try' statement. | ||
| 404 | if (sourceDA.x == fullX) { | ||
| 405 | return sourceDA.copy(); | ||
| 406 | } | ||
| 407 | |||
| 408 | long sourceDAx[] = sourceDA.x; | ||
| 409 | int lenDA = sourceDAx.length; | ||
| 410 | long sourceDUx[] = sourceDU.x; | ||
| 411 | int lenDU = sourceDUx.length; | ||
| 412 | int limit = (lenDA > lenDU) ? lenDA : lenDU; | ||
| 413 | long x[] = emptyX; | ||
| 414 | |||
| 415 | if (limit > 0) { | ||
| 416 | x = new long[limit]; | ||
| 417 | for (int i = 0; i < lenDA; i += 2) { | ||
| 418 | x[i] = sourceDAx[i]; | ||
| 419 | } | ||
| 420 | for (int i = 1; i < lenDU; i += 2) { | ||
| 421 | x[i] = sourceDUx[i]; | ||
| 422 | } | ||
| 423 | } | ||
| 424 | |||
| 425 | return new Vset(sourceDA.vset, sourceDU.uset, x); | ||
| 426 | } | ||
| 427 | |||
| 428 | /** | ||
| 429 | * Remove variables from the vset that are no longer part of | ||
| 430 | * a context. Zeroes are stored past varNumber. | ||
| 431 | * (Side-effecting.)<p> | ||
| 432 | * However, if this is a dead end, keep it so. | ||
| 433 | * That is, leave an infinite tail of bits set. | ||
| 434 | */ | ||
| 435 | public Vset removeAdditionalVars(int varNumber) { | ||
| 436 | if (x == fullX) { | ||
| 437 | return this; | ||
| 438 | } | ||
| 439 | long bit = (1L << varNumber); | ||
| 440 | if (varNumber >= VBITS) { | ||
| 441 | int i = (varNumber / VBITS - 1) * 2; | ||
| 442 | if (i < x.length) { | ||
| 443 | x[i] &= (bit - 1); | ||
| 444 | if (++i < x.length) { | ||
| 445 | x[i] &= (bit - 1); // do the "uset" extension also | ||
| 446 | } | ||
| 447 | while (++i < x.length) { | ||
| 448 | x[i] = 0; | ||
| 449 | } | ||
| 450 | } | ||
| 451 | } else { | ||
| 452 | if (x.length > 0) { | ||
| 453 | x = emptyX; | ||
| 454 | } | ||
| 455 | vset &= (bit - 1); | ||
| 456 | uset &= (bit - 1); | ||
| 457 | } | ||
| 458 | return this; | ||
| 459 | } | ||
| 460 | |||
| 461 | /** | ||
| 462 | * Return one larger than the highest bit set. | ||
| 463 | */ | ||
| 464 | public int varLimit() { | ||
| 465 | long vset; | ||
| 466 | int result; | ||
| 467 | scan: { | ||
| 468 | for (int i = (x.length / 2) * 2; i >= 0; i -= 2) { | ||
| 469 | if (i == x.length) continue; // oops | ||
| 470 | vset = x[i]; | ||
| 471 | if (i+1 < x.length) { | ||
| 472 | vset |= x[i+1]; // check the "uset" also | ||
| 473 | } | ||
| 474 | if (vset != 0) { | ||
| 475 | result = (i/2 + 1) * VBITS; | ||
| 476 | break scan; | ||
| 477 | } | ||
| 478 | } | ||
| 479 | vset = this.vset; | ||
| 480 | vset |= this.uset; // check the "uset" also | ||
| 481 | if (vset != 0) { | ||
| 482 | result = 0; | ||
| 483 | break scan; | ||
| 484 | } else { | ||
| 485 | return 0; | ||
| 486 | } | ||
| 487 | } | ||
| 488 | while (vset != 0) { | ||
| 489 | result += 1; | ||
| 490 | vset >>>= 1; | ||
| 491 | } | ||
| 492 | return result; | ||
| 493 | } | ||
| 494 | |||
| 495 | public String toString() { | ||
| 496 | if (this == DEAD_END) | ||
| 497 | return "{DEAD_END}"; | ||
| 498 | StringBuffer sb = new StringBuffer("{"); | ||
| 499 | int maxVar = VBITS * (1 + (x.length+1)/2); | ||
| 500 | for (int i = 0; i < maxVar; i++) { | ||
| 501 | if (!testVarUnassigned(i)) { | ||
| 502 | if (sb.length() > 1) { | ||
| 503 | sb.append(' '); | ||
| 504 | } | ||
| 505 | sb.append(i); | ||
| 506 | if (!testVar(i)) { | ||
| 507 | sb.append('?'); // not definitely unassigned | ||
| 508 | } | ||
| 509 | } | ||
| 510 | } | ||
| 511 | if (x == fullX) { | ||
| 512 | sb.append("...DEAD_END"); | ||
| 513 | } | ||
| 514 | sb.append('}'); | ||
| 515 | return sb.toString(); | ||
| 516 | } | ||
| 517 | |||
| 518 | } | ||