dfg/DFGAbstractValue.cpp

   1 /*
   2  * Copyright (C) 2013-2015 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "DFGAbstractValue.h"
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "DFGGraph.h"
  32 #include "JSCInlines.h"
  33 #include "TrackedReferences.h"
  34
  35 namespace JSC { namespace DFG {
  36
  37 void AbstractValue::observeTransitions(const TransitionVector& vector)
  38 {
  39     if (m_type & SpecCell) {
  40         m_structure.observeTransitions(vector);
  41         ArrayModes newModes = 0;
  42         for (unsigned i = vector.size(); i--;) {
  43             if (m_arrayModes & asArrayModes(vector[i].previous->indexingType()))
  44                 newModes |= asArrayModes(vector[i].next->indexingType());
  45         }
  46         m_arrayModes |= newModes;
  47     }
  48     checkConsistency();
  49 }
  50
  51 void AbstractValue::set(Graph& graph, const FrozenValue& value, StructureClobberState clobberState)
  52 {
  53     if (!!value && value.value().isCell()) {
  54         Structure* structure = value.structure();
  55         if (graph.registerStructure(structure) == StructureRegisteredAndWatched) {
  56             m_structure = structure;
  57             if (clobberState == StructuresAreClobbered) {
  58                 m_arrayModes = ALL_ARRAY_MODES;
  59                 m_structure.clobber();
  60             } else
  61                 m_arrayModes = asArrayModes(structure->indexingType());
  62         } else {
  63             m_structure.makeTop();
  64             m_arrayModes = ALL_ARRAY_MODES;
  65         }
  66     } else {
  67         m_structure.clear();
  68         m_arrayModes = 0;
  69     }
  70
  71     m_type = speculationFromValue(value.value());
  72     m_value = value.value();
  73
  74     checkConsistency();
  75     assertIsRegistered(graph);
  76 }
  77
  78 void AbstractValue::set(Graph& graph, Structure* structure)
  79 {
  80     m_structure = structure;
  81     m_arrayModes = asArrayModes(structure->indexingType());
  82     m_type = speculationFromStructure(structure);
  83     m_value = JSValue();
  84
  85     checkConsistency();
  86     assertIsRegistered(graph);
  87 }
  88
  89 void AbstractValue::set(Graph& graph, const StructureSet& set)
  90 {
  91     m_structure = set;
  92     m_arrayModes = set.arrayModesFromStructures();
  93     m_type = set.speculationFromStructures();
  94     m_value = JSValue();
  95
  96     checkConsistency();
  97     assertIsRegistered(graph);
  98 }
  99
 100 void AbstractValue::setType(Graph& graph, SpeculatedType type)
 101 {
 102     SpeculatedType cellType = type & SpecCell;
 103     if (cellType) {
 104         if (!(cellType & ~SpecString))
 105             m_structure = graph.m_vm.stringStructure.get();
 106         else if (isSymbolSpeculation(cellType))
 107             m_structure = graph.m_vm.symbolStructure.get();
 108         else
 109             m_structure.makeTop();
 110         m_arrayModes = ALL_ARRAY_MODES;
 111     } else {
 112         m_structure.clear();
 113         m_arrayModes = 0;
 114     }
 115     m_type = type;
 116     m_value = JSValue();
 117     checkConsistency();
 118 }
 119
 120 void AbstractValue::fixTypeForRepresentation(Graph& graph, NodeFlags representation, Node* node)
 121 {
 122     if (representation == NodeResultDouble) {
 123         if (m_value) {
 124             ASSERT(m_value.isNumber());
 125             if (m_value.isInt32())
 126                 m_value = jsDoubleNumber(m_value.asNumber());
 127         }
 128         if (m_type & SpecMachineInt) {
 129             m_type &= ~SpecMachineInt;
 130             m_type |= SpecInt52AsDouble;
 131         }
 132         if (m_type & ~SpecFullDouble)
 133             DFG_CRASH(graph, node, toCString("Abstract value ", *this, " for double node has type outside SpecFullDouble.\n").data());
 134     } else if (representation == NodeResultInt52) {
 135         if (m_type & SpecInt52AsDouble) {
 136             m_type &= ~SpecInt52AsDouble;
 137             m_type |= SpecInt52;
 138         }
 139         if (m_type & ~SpecMachineInt)
 140             DFG_CRASH(graph, node, toCString("Abstract value ", *this, " for int52 node has type outside SpecMachineInt.\n").data());
 141     } else {
 142         if (m_type & SpecInt52) {
 143             m_type &= ~SpecInt52;
 144             m_type |= SpecInt52AsDouble;
 145         }
 146         if (m_type & ~SpecBytecodeTop)
 147             DFG_CRASH(graph, node, toCString("Abstract value ", *this, " for value node has type outside SpecBytecodeTop.\n").data());
 148     }
 149
 150     checkConsistency();
 151 }
 152
 153 void AbstractValue::fixTypeForRepresentation(Graph& graph, Node* node)
 154 {
 155     fixTypeForRepresentation(graph, node->result(), node);
 156 }
 157
 158 bool AbstractValue::mergeOSREntryValue(Graph& graph, JSValue value)
 159 {
 160     AbstractValue oldMe = *this;
 161
 162     if (isClear()) {
 163         FrozenValue* frozenValue = graph.freeze(value);
 164         if (frozenValue->pointsToHeap()) {
 165             m_structure = frozenValue->structure();
 166             m_arrayModes = asArrayModes(frozenValue->structure()->indexingType());
 167         } else {
 168             m_structure.clear();
 169             m_arrayModes = 0;
 170         }
 171
 172         m_type = speculationFromValue(value);
 173         m_value = value;
 174     } else {
 175         mergeSpeculation(m_type, speculationFromValue(value));
 176         if (!!value && value.isCell()) {
 177             Structure* structure = value.asCell()->structure();
 178             graph.registerStructure(structure);
 179             mergeArrayModes(m_arrayModes, asArrayModes(structure->indexingType()));
 180             m_structure.merge(StructureSet(structure));
 181         }
 182         if (m_value != value)
 183             m_value = JSValue();
 184     }
 185
 186     checkConsistency();
 187     assertIsRegistered(graph);
 188
 189     return oldMe != *this;
 190 }
 191
 192 FiltrationResult AbstractValue::filter(Graph& graph, const StructureSet& other)
 193 {
 194     if (isClear())
 195         return FiltrationOK;
 196
 197     // FIXME: This could be optimized for the common case of m_type not
 198     // having structures, array modes, or a specific value.
 199     // https://bugs.webkit.org/show_bug.cgi?id=109663
 200
 201     m_type &= other.speculationFromStructures();
 202     m_arrayModes &= other.arrayModesFromStructures();
 203     m_structure.filter(other);
 204
 205     // It's possible that prior to the above two statements we had (Foo, TOP), where
 206     // Foo is a SpeculatedType that is disjoint with the passed StructureSet. In that
 207     // case, we will now have (None, [someStructure]). In general, we need to make
 208     // sure that new information gleaned from the SpeculatedType needs to be fed back
 209     // into the information gleaned from the StructureSet.
 210     m_structure.filter(m_type);
 211
 212     filterArrayModesByType();
 213     filterValueByType();
 214     return normalizeClarity(graph);
 215 }
 216
 217 FiltrationResult AbstractValue::changeStructure(Graph& graph, const StructureSet& other)
 218 {
 219     m_type &= other.speculationFromStructures();
 220     m_arrayModes = other.arrayModesFromStructures();
 221     m_structure = other;
 222
 223     filterValueByType();
 224
 225     return normalizeClarity(graph);
 226 }
 227
 228 FiltrationResult AbstractValue::filterArrayModes(ArrayModes arrayModes)
 229 {
 230     ASSERT(arrayModes);
 231
 232     if (isClear())
 233         return FiltrationOK;
 234
 235     m_type &= SpecCell;
 236     m_arrayModes &= arrayModes;
 237     return normalizeClarity();
 238 }
 239
 240 FiltrationResult AbstractValue::filter(SpeculatedType type)
 241 {
 242     if ((m_type & type) == m_type)
 243         return FiltrationOK;
 244
 245     // Fast path for the case that we don't even have a cell.
 246     if (!(m_type & SpecCell)) {
 247         m_type &= type;
 248         FiltrationResult result;
 249         if (m_type == SpecNone) {
 250             clear();
 251             result = Contradiction;
 252         } else
 253             result = FiltrationOK;
 254         checkConsistency();
 255         return result;
 256     }
 257
 258     m_type &= type;
 259
 260     // It's possible that prior to this filter() call we had, say, (Final, TOP), and
 261     // the passed type is Array. At this point we'll have (None, TOP). The best way
 262     // to ensure that the structure filtering does the right thing is to filter on
 263     // the new type (None) rather than the one passed (Array).
 264     m_structure.filter(type);
 265     filterArrayModesByType();
 266     filterValueByType();
 267     return normalizeClarity();
 268 }
 269
 270 FiltrationResult AbstractValue::filterByValue(const FrozenValue& value)
 271 {
 272     FiltrationResult result = filter(speculationFromValue(value.value()));
 273     if (m_type)
 274         m_value = value.value();
 275     return result;
 276 }
 277
 278 bool AbstractValue::contains(Structure* structure) const
 279 {
 280     return couldBeType(speculationFromStructure(structure))
 281         && (m_arrayModes & arrayModeFromStructure(structure))
 282         && m_structure.contains(structure);
 283 }
 284
 285 FiltrationResult AbstractValue::filter(const AbstractValue& other)
 286 {
 287     m_type &= other.m_type;
 288     m_structure.filter(other.m_structure);
 289     m_arrayModes &= other.m_arrayModes;
 290
 291     m_structure.filter(m_type);
 292     filterArrayModesByType();
 293     filterValueByType();
 294
 295     if (normalizeClarity() == Contradiction)
 296         return Contradiction;
 297
 298     if (m_value == other.m_value)
 299         return FiltrationOK;
 300
 301     // Neither of us are BOTTOM, so an empty value means TOP.
 302     if (!m_value) {
 303         // We previously didn't prove a value but now we have done so.
 304         m_value = other.m_value;
 305         return FiltrationOK;
 306     }
 307
 308     if (!other.m_value) {
 309         // We had proved a value but the other guy hadn't, so keep our proof.
 310         return FiltrationOK;
 311     }
 312
 313     // We both proved there to be a specific value but they are different.
 314     clear();
 315     return Contradiction;
 316 }
 317
 318 void AbstractValue::filterValueByType()
 319 {
 320     // We could go further, and ensure that if the futurePossibleStructure contravenes
 321     // the value, then we could clear both of those things. But that's unlikely to help
 322     // in any realistic scenario, so we don't do it. Simpler is better.
 323
 324     if (!!m_type) {
 325         // The type is still non-empty. It may be that the new type renders
 326         // the value empty because it contravenes the constant value we had.
 327         if (m_value && !validateType(m_value))
 328             clear();
 329         return;
 330     }
 331
 332     // The type has been rendered empty. That means that the value must now be invalid,
 333     // as well.
 334     ASSERT(!m_value || !validateType(m_value));
 335     m_value = JSValue();
 336 }
 337
 338 void AbstractValue::filterArrayModesByType()
 339 {
 340     if (!(m_type & SpecCell))
 341         m_arrayModes = 0;
 342     else if (!(m_type & ~SpecArray))
 343         m_arrayModes &= ALL_ARRAY_ARRAY_MODES;
 344
 345     // NOTE: If m_type doesn't have SpecArray set, that doesn't mean that the
 346     // array modes have to be a subset of ALL_NON_ARRAY_ARRAY_MODES, since
 347     // in the speculated type type-system, RegExpMatchesArry and ArrayPrototype
 348     // are Otherobj (since they are not *exactly* JSArray) but in the ArrayModes
 349     // type system they are arrays (since they expose the magical length
 350     // property and are otherwise allocated using array allocation). Hence the
 351     // following would be wrong:
 352     //
 353     // if (!(m_type & SpecArray))
 354     //    m_arrayModes &= ALL_NON_ARRAY_ARRAY_MODES;
 355 }
 356
 357 bool AbstractValue::shouldBeClear() const
 358 {
 359     if (m_type == SpecNone)
 360         return true;
 361
 362     if (!(m_type & ~SpecCell)
 363         && (!m_arrayModes || m_structure.isClear()))
 364         return true;
 365
 366     return false;
 367 }
 368
 369 FiltrationResult AbstractValue::normalizeClarity()
 370 {
 371     // It's useful to be able to quickly check if an abstract value is clear.
 372     // This normalizes everything to make that easy.
 373
 374     FiltrationResult result;
 375
 376     if (shouldBeClear()) {
 377         clear();
 378         result = Contradiction;
 379     } else
 380         result = FiltrationOK;
 381
 382     checkConsistency();
 383
 384     return result;
 385 }
 386
 387 FiltrationResult AbstractValue::normalizeClarity(Graph& graph)
 388 {
 389     FiltrationResult result = normalizeClarity();
 390     assertIsRegistered(graph);
 391     return result;
 392 }
 393
 394 #if !ASSERT_DISABLED
 395 void AbstractValue::checkConsistency() const
 396 {
 397     if (!(m_type & SpecCell)) {
 398         ASSERT(m_structure.isClear());
 399         ASSERT(!m_arrayModes);
 400     }
 401
 402     if (isClear())
 403         ASSERT(!m_value);
 404
 405     if (!!m_value) {
 406         SpeculatedType type = m_type;
 407         // This relaxes the assertion below a bit, since we don't know the representation of the
 408         // node.
 409         if (type & SpecInt52)
 410             type |= SpecInt52AsDouble;
 411         ASSERT(mergeSpeculations(type, speculationFromValue(m_value)) == type);
 412     }
 413
 414     // Note that it's possible for a prediction like (Final, []). This really means that
 415     // the value is bottom and that any code that uses the value is unreachable. But
 416     // we don't want to get pedantic about this as it would only increase the computational
 417     // complexity of the code.
 418 }
 419
 420 void AbstractValue::assertIsRegistered(Graph& graph) const
 421 {
 422     m_structure.assertIsRegistered(graph);
 423 }
 424 #endif
 425
 426 void AbstractValue::dump(PrintStream& out) const
 427 {
 428     dumpInContext(out, 0);
 429 }
 430
 431 void AbstractValue::dumpInContext(PrintStream& out, DumpContext* context) const
 432 {
 433     out.print("(", SpeculationDump(m_type));
 434     if (m_type & SpecCell) {
 435         out.print(
 436             ", ", ArrayModesDump(m_arrayModes), ", ",
 437             inContext(m_structure, context));
 438     }
 439     if (!!m_value)
 440         out.print(", ", inContext(m_value, context));
 441     out.print(")");
 442 }
 443
 444 void AbstractValue::validateReferences(const TrackedReferences& trackedReferences)
 445 {
 446     trackedReferences.check(m_value);
 447     m_structure.validateReferences(trackedReferences);
 448 }
 449
 450 } } // namespace JSC::DFG
 451
 452 #endif // ENABLE(DFG_JIT)
 453