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SimpleSValBuilder.cpp
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1 // SimpleSValBuilder.cpp - A basic SValBuilder -----------------------*- C++ -*-
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines SimpleSValBuilder, a basic implementation of SValBuilder.
11 //
12 //===----------------------------------------------------------------------===//
13 
20 
21 using namespace clang;
22 using namespace ento;
23 
24 namespace {
25 class SimpleSValBuilder : public SValBuilder {
26 protected:
27  SVal dispatchCast(SVal val, QualType castTy) override;
28  SVal evalCastFromNonLoc(NonLoc val, QualType castTy) override;
29  SVal evalCastFromLoc(Loc val, QualType castTy) override;
30 
31 public:
32  SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context,
33  ProgramStateManager &stateMgr)
34  : SValBuilder(alloc, context, stateMgr) {}
35  ~SimpleSValBuilder() override {}
36 
37  SVal evalMinus(NonLoc val) override;
38  SVal evalComplement(NonLoc val) override;
39  SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op,
40  NonLoc lhs, NonLoc rhs, QualType resultTy) override;
41  SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op,
42  Loc lhs, Loc rhs, QualType resultTy) override;
43  SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op,
44  Loc lhs, NonLoc rhs, QualType resultTy) override;
45 
46  /// getKnownValue - evaluates a given SVal. If the SVal has only one possible
47  /// (integer) value, that value is returned. Otherwise, returns NULL.
48  const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override;
49 
50  /// Recursively descends into symbolic expressions and replaces symbols
51  /// with their known values (in the sense of the getKnownValue() method).
52  SVal simplifySVal(ProgramStateRef State, SVal V) override;
53 
54  SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op,
55  const llvm::APSInt &RHS, QualType resultTy);
56 };
57 } // end anonymous namespace
58 
59 SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc,
60  ASTContext &context,
61  ProgramStateManager &stateMgr) {
62  return new SimpleSValBuilder(alloc, context, stateMgr);
63 }
64 
65 //===----------------------------------------------------------------------===//
66 // Transfer function for Casts.
67 //===----------------------------------------------------------------------===//
68 
69 SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) {
70  assert(Val.getAs<Loc>() || Val.getAs<NonLoc>());
71  return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy)
72  : evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy);
73 }
74 
75 SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) {
76  bool isLocType = Loc::isLocType(castTy);
77  if (val.getAs<nonloc::PointerToMember>())
78  return val;
79 
81  if (isLocType)
82  return LI->getLoc();
83  // FIXME: Correctly support promotions/truncations.
84  unsigned castSize = Context.getIntWidth(castTy);
85  if (castSize == LI->getNumBits())
86  return val;
87  return makeLocAsInteger(LI->getLoc(), castSize);
88  }
89 
90  if (const SymExpr *se = val.getAsSymbolicExpression()) {
91  QualType T = Context.getCanonicalType(se->getType());
92  // If types are the same or both are integers, ignore the cast.
93  // FIXME: Remove this hack when we support symbolic truncation/extension.
94  // HACK: If both castTy and T are integers, ignore the cast. This is
95  // not a permanent solution. Eventually we want to precisely handle
96  // extension/truncation of symbolic integers. This prevents us from losing
97  // precision when we assign 'x = y' and 'y' is symbolic and x and y are
98  // different integer types.
99  if (haveSameType(T, castTy))
100  return val;
101 
102  if (!isLocType)
103  return makeNonLoc(se, T, castTy);
104  return UnknownVal();
105  }
106 
107  // If value is a non-integer constant, produce unknown.
108  if (!val.getAs<nonloc::ConcreteInt>())
109  return UnknownVal();
110 
111  // Handle casts to a boolean type.
112  if (castTy->isBooleanType()) {
113  bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue();
114  return makeTruthVal(b, castTy);
115  }
116 
117  // Only handle casts from integers to integers - if val is an integer constant
118  // being cast to a non-integer type, produce unknown.
119  if (!isLocType && !castTy->isIntegralOrEnumerationType())
120  return UnknownVal();
121 
122  llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue();
123  BasicVals.getAPSIntType(castTy).apply(i);
124 
125  if (isLocType)
126  return makeIntLocVal(i);
127  else
128  return makeIntVal(i);
129 }
130 
131 SVal SimpleSValBuilder::evalCastFromLoc(Loc val, QualType castTy) {
132 
133  // Casts from pointers -> pointers, just return the lval.
134  //
135  // Casts from pointers -> references, just return the lval. These
136  // can be introduced by the frontend for corner cases, e.g
137  // casting from va_list* to __builtin_va_list&.
138  //
139  if (Loc::isLocType(castTy) || castTy->isReferenceType())
140  return val;
141 
142  // FIXME: Handle transparent unions where a value can be "transparently"
143  // lifted into a union type.
144  if (castTy->isUnionType())
145  return UnknownVal();
146 
147  // Casting a Loc to a bool will almost always be true,
148  // unless this is a weak function or a symbolic region.
149  if (castTy->isBooleanType()) {
150  switch (val.getSubKind()) {
151  case loc::MemRegionValKind: {
152  const MemRegion *R = val.castAs<loc::MemRegionVal>().getRegion();
153  if (const FunctionCodeRegion *FTR = dyn_cast<FunctionCodeRegion>(R))
154  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl()))
155  if (FD->isWeak())
156  // FIXME: Currently we are using an extent symbol here,
157  // because there are no generic region address metadata
158  // symbols to use, only content metadata.
159  return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR));
160 
161  if (const SymbolicRegion *SymR = R->getSymbolicBase())
162  return makeNonLoc(SymR->getSymbol(), BO_NE,
163  BasicVals.getZeroWithPtrWidth(), castTy);
164 
165  // FALL-THROUGH
166  LLVM_FALLTHROUGH;
167  }
168 
169  case loc::GotoLabelKind:
170  // Labels and non-symbolic memory regions are always true.
171  return makeTruthVal(true, castTy);
172  }
173  }
174 
175  if (castTy->isIntegralOrEnumerationType()) {
176  unsigned BitWidth = Context.getIntWidth(castTy);
177 
178  if (!val.getAs<loc::ConcreteInt>())
179  return makeLocAsInteger(val, BitWidth);
180 
181  llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue();
182  BasicVals.getAPSIntType(castTy).apply(i);
183  return makeIntVal(i);
184  }
185 
186  // All other cases: return 'UnknownVal'. This includes casting pointers
187  // to floats, which is probably badness it itself, but this is a good
188  // intermediate solution until we do something better.
189  return UnknownVal();
190 }
191 
192 //===----------------------------------------------------------------------===//
193 // Transfer function for unary operators.
194 //===----------------------------------------------------------------------===//
195 
196 SVal SimpleSValBuilder::evalMinus(NonLoc val) {
197  switch (val.getSubKind()) {
198  case nonloc::ConcreteIntKind:
199  return val.castAs<nonloc::ConcreteInt>().evalMinus(*this);
200  default:
201  return UnknownVal();
202  }
203 }
204 
205 SVal SimpleSValBuilder::evalComplement(NonLoc X) {
206  switch (X.getSubKind()) {
207  case nonloc::ConcreteIntKind:
208  return X.castAs<nonloc::ConcreteInt>().evalComplement(*this);
209  default:
210  return UnknownVal();
211  }
212 }
213 
214 //===----------------------------------------------------------------------===//
215 // Transfer function for binary operators.
216 //===----------------------------------------------------------------------===//
217 
218 SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,
220  const llvm::APSInt &RHS,
221  QualType resultTy) {
222  bool isIdempotent = false;
223 
224  // Check for a few special cases with known reductions first.
225  switch (op) {
226  default:
227  // We can't reduce this case; just treat it normally.
228  break;
229  case BO_Mul:
230  // a*0 and a*1
231  if (RHS == 0)
232  return makeIntVal(0, resultTy);
233  else if (RHS == 1)
234  isIdempotent = true;
235  break;
236  case BO_Div:
237  // a/0 and a/1
238  if (RHS == 0)
239  // This is also handled elsewhere.
240  return UndefinedVal();
241  else if (RHS == 1)
242  isIdempotent = true;
243  break;
244  case BO_Rem:
245  // a%0 and a%1
246  if (RHS == 0)
247  // This is also handled elsewhere.
248  return UndefinedVal();
249  else if (RHS == 1)
250  return makeIntVal(0, resultTy);
251  break;
252  case BO_Add:
253  case BO_Sub:
254  case BO_Shl:
255  case BO_Shr:
256  case BO_Xor:
257  // a+0, a-0, a<<0, a>>0, a^0
258  if (RHS == 0)
259  isIdempotent = true;
260  break;
261  case BO_And:
262  // a&0 and a&(~0)
263  if (RHS == 0)
264  return makeIntVal(0, resultTy);
265  else if (RHS.isAllOnesValue())
266  isIdempotent = true;
267  break;
268  case BO_Or:
269  // a|0 and a|(~0)
270  if (RHS == 0)
271  isIdempotent = true;
272  else if (RHS.isAllOnesValue()) {
273  const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS);
274  return nonloc::ConcreteInt(Result);
275  }
276  break;
277  }
278 
279  // Idempotent ops (like a*1) can still change the type of an expression.
280  // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the
281  // dirty work.
282  if (isIdempotent)
283  return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy);
284 
285  // If we reach this point, the expression cannot be simplified.
286  // Make a SymbolVal for the entire expression, after converting the RHS.
287  const llvm::APSInt *ConvertedRHS = &RHS;
289  // We're looking for a type big enough to compare the symbolic value
290  // with the given constant.
291  // FIXME: This is an approximation of Sema::UsualArithmeticConversions.
292  ASTContext &Ctx = getContext();
293  QualType SymbolType = LHS->getType();
294  uint64_t ValWidth = RHS.getBitWidth();
295  uint64_t TypeWidth = Ctx.getTypeSize(SymbolType);
296 
297  if (ValWidth < TypeWidth) {
298  // If the value is too small, extend it.
299  ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
300  } else if (ValWidth == TypeWidth) {
301  // If the value is signed but the symbol is unsigned, do the comparison
302  // in unsigned space. [C99 6.3.1.8]
303  // (For the opposite case, the value is already unsigned.)
304  if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType())
305  ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
306  }
307  } else
308  ConvertedRHS = &BasicVals.Convert(resultTy, RHS);
309 
310  return makeNonLoc(LHS, op, *ConvertedRHS, resultTy);
311 }
312 
313 // See if Sym is known to be a relation Rel with Bound.
315  llvm::APSInt Bound, ProgramStateRef State) {
316  SValBuilder &SVB = State->getStateManager().getSValBuilder();
317  SVal Result =
318  SVB.evalBinOpNN(State, Rel, nonloc::SymbolVal(Sym),
319  nonloc::ConcreteInt(Bound), SVB.getConditionType());
320  if (auto DV = Result.getAs<DefinedSVal>()) {
321  return !State->assume(*DV, false);
322  }
323  return false;
324 }
325 
326 // See if Sym is known to be within [min/4, max/4], where min and max
327 // are the bounds of the symbol's integral type. With such symbols,
328 // some manipulations can be performed without the risk of overflow.
329 // assume() doesn't cause infinite recursion because we should be dealing
330 // with simpler symbols on every recursive call.
333  SValBuilder &SVB = State->getStateManager().getSValBuilder();
334  BasicValueFactory &BV = SVB.getBasicValueFactory();
335 
336  QualType T = Sym->getType();
337  assert(T->isSignedIntegerOrEnumerationType() &&
338  "This only works with signed integers!");
339  APSIntType AT = BV.getAPSIntType(T);
340 
341  llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max;
342  return isInRelation(BO_LE, Sym, Max, State) &&
343  isInRelation(BO_GE, Sym, Min, State);
344 }
345 
346 // Same for the concrete integers: see if I is within [min/4, max/4].
347 static bool isWithinConstantOverflowBounds(llvm::APSInt I) {
348  APSIntType AT(I);
349  assert(!AT.isUnsigned() &&
350  "This only works with signed integers!");
351 
352  llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max;
353  return (I <= Max) && (I >= -Max);
354 }
355 
356 static std::pair<SymbolRef, llvm::APSInt>
357 decomposeSymbol(SymbolRef Sym, BasicValueFactory &BV) {
358  if (const auto *SymInt = dyn_cast<SymIntExpr>(Sym))
359  if (BinaryOperator::isAdditiveOp(SymInt->getOpcode()))
360  return std::make_pair(SymInt->getLHS(),
361  (SymInt->getOpcode() == BO_Add) ?
362  (SymInt->getRHS()) :
363  (-SymInt->getRHS()));
364 
365  // Fail to decompose: "reduce" the problem to the "$x + 0" case.
366  return std::make_pair(Sym, BV.getValue(0, Sym->getType()));
367 }
368 
369 // Simplify "(LSym + LInt) Op (RSym + RInt)" assuming all values are of the
370 // same signed integral type and no overflows occur (which should be checked
371 // by the caller).
374  SymbolRef LSym, llvm::APSInt LInt,
375  SymbolRef RSym, llvm::APSInt RInt) {
376  SValBuilder &SVB = State->getStateManager().getSValBuilder();
377  BasicValueFactory &BV = SVB.getBasicValueFactory();
378  SymbolManager &SymMgr = SVB.getSymbolManager();
379 
380  QualType SymTy = LSym->getType();
381  assert(SymTy == RSym->getType() &&
382  "Symbols are not of the same type!");
383  assert(APSIntType(LInt) == BV.getAPSIntType(SymTy) &&
384  "Integers are not of the same type as symbols!");
385  assert(APSIntType(RInt) == BV.getAPSIntType(SymTy) &&
386  "Integers are not of the same type as symbols!");
387 
388  QualType ResultTy;
390  ResultTy = SVB.getConditionType();
391  else if (BinaryOperator::isAdditiveOp(Op))
392  ResultTy = SymTy;
393  else
394  llvm_unreachable("Operation not suitable for unchecked rearrangement!");
395 
396  // FIXME: Can we use assume() without getting into an infinite recursion?
397  if (LSym == RSym)
398  return SVB.evalBinOpNN(State, Op, nonloc::ConcreteInt(LInt),
399  nonloc::ConcreteInt(RInt), ResultTy)
400  .castAs<NonLoc>();
401 
402  SymbolRef ResultSym = nullptr;
403  BinaryOperator::Opcode ResultOp;
404  llvm::APSInt ResultInt;
406  // Prefer comparing to a non-negative number.
407  // FIXME: Maybe it'd be better to have consistency in
408  // "$x - $y" vs. "$y - $x" because those are solver's keys.
409  if (LInt > RInt) {
410  ResultSym = SymMgr.getSymSymExpr(RSym, BO_Sub, LSym, SymTy);
412  ResultInt = LInt - RInt; // Opposite order!
413  } else {
414  ResultSym = SymMgr.getSymSymExpr(LSym, BO_Sub, RSym, SymTy);
415  ResultOp = Op;
416  ResultInt = RInt - LInt; // Opposite order!
417  }
418  } else {
419  ResultSym = SymMgr.getSymSymExpr(LSym, Op, RSym, SymTy);
420  ResultInt = (Op == BO_Add) ? (LInt + RInt) : (LInt - RInt);
421  ResultOp = BO_Add;
422  // Bring back the cosmetic difference.
423  if (ResultInt < 0) {
424  ResultInt = -ResultInt;
425  ResultOp = BO_Sub;
426  } else if (ResultInt == 0) {
427  // Shortcut: Simplify "$x + 0" to "$x".
428  return nonloc::SymbolVal(ResultSym);
429  }
430  }
431  const llvm::APSInt &PersistentResultInt = BV.getValue(ResultInt);
432  return nonloc::SymbolVal(
433  SymMgr.getSymIntExpr(ResultSym, ResultOp, PersistentResultInt, ResultTy));
434 }
435 
436 // Rearrange if symbol type matches the result type and if the operator is a
437 // comparison operator, both symbol and constant must be within constant
438 // overflow bounds.
440  SymbolRef Sym, llvm::APSInt Int, QualType Ty) {
441  return Sym->getType() == Ty &&
443  (isWithinConstantOverflowBounds(Sym, State) &&
445 }
446 
448  BinaryOperator::Opcode Op, NonLoc Lhs,
449  NonLoc Rhs, QualType ResultTy) {
450  ProgramStateManager &StateMgr = State->getStateManager();
451  SValBuilder &SVB = StateMgr.getSValBuilder();
452 
453  // We expect everything to be of the same type - this type.
454  QualType SingleTy;
455 
456  auto &Opts =
457  StateMgr.getOwningEngine()->getAnalysisManager().getAnalyzerOptions();
458 
459  // FIXME: After putting complexity threshold to the symbols we can always
460  // rearrange additive operations but rearrange comparisons only if
461  // option is set.
462  if(!Opts.shouldAggressivelySimplifyBinaryOperation())
463  return None;
464 
465  SymbolRef LSym = Lhs.getAsSymbol();
466  if (!LSym)
467  return None;
468 
470  SingleTy = LSym->getType();
471  if (ResultTy != SVB.getConditionType())
472  return None;
473  // Initialize SingleTy later with a symbol's type.
474  } else if (BinaryOperator::isAdditiveOp(Op)) {
475  SingleTy = ResultTy;
476  if (LSym->getType() != SingleTy)
477  return None;
478  // Substracting unsigned integers is a nightmare.
479  if (!SingleTy->isSignedIntegerOrEnumerationType())
480  return None;
481  } else {
482  // Don't rearrange other operations.
483  return None;
484  }
485 
486  assert(!SingleTy.isNull() && "We should have figured out the type by now!");
487 
488  SymbolRef RSym = Rhs.getAsSymbol();
489  if (!RSym || RSym->getType() != SingleTy)
490  return None;
491 
492  BasicValueFactory &BV = State->getBasicVals();
493  llvm::APSInt LInt, RInt;
494  std::tie(LSym, LInt) = decomposeSymbol(LSym, BV);
495  std::tie(RSym, RInt) = decomposeSymbol(RSym, BV);
496  if (!shouldRearrange(State, Op, LSym, LInt, SingleTy) ||
497  !shouldRearrange(State, Op, RSym, RInt, SingleTy))
498  return None;
499 
500  // We know that no overflows can occur anymore.
501  return doRearrangeUnchecked(State, Op, LSym, LInt, RSym, RInt);
502 }
503 
504 SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
506  NonLoc lhs, NonLoc rhs,
507  QualType resultTy) {
508  NonLoc InputLHS = lhs;
509  NonLoc InputRHS = rhs;
510 
511  // Handle trivial case where left-side and right-side are the same.
512  if (lhs == rhs)
513  switch (op) {
514  default:
515  break;
516  case BO_EQ:
517  case BO_LE:
518  case BO_GE:
519  return makeTruthVal(true, resultTy);
520  case BO_LT:
521  case BO_GT:
522  case BO_NE:
523  return makeTruthVal(false, resultTy);
524  case BO_Xor:
525  case BO_Sub:
526  if (resultTy->isIntegralOrEnumerationType())
527  return makeIntVal(0, resultTy);
528  return evalCastFromNonLoc(makeIntVal(0, /*Unsigned=*/false), resultTy);
529  case BO_Or:
530  case BO_And:
531  return evalCastFromNonLoc(lhs, resultTy);
532  }
533 
534  while (1) {
535  switch (lhs.getSubKind()) {
536  default:
537  return makeSymExprValNN(op, lhs, rhs, resultTy);
538  case nonloc::PointerToMemberKind: {
539  assert(rhs.getSubKind() == nonloc::PointerToMemberKind &&
540  "Both SVals should have pointer-to-member-type");
541  auto LPTM = lhs.castAs<nonloc::PointerToMember>(),
542  RPTM = rhs.castAs<nonloc::PointerToMember>();
543  auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData();
544  switch (op) {
545  case BO_EQ:
546  return makeTruthVal(LPTMD == RPTMD, resultTy);
547  case BO_NE:
548  return makeTruthVal(LPTMD != RPTMD, resultTy);
549  default:
550  return UnknownVal();
551  }
552  }
553  case nonloc::LocAsIntegerKind: {
554  Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc();
555  switch (rhs.getSubKind()) {
556  case nonloc::LocAsIntegerKind:
557  // FIXME: at the moment the implementation
558  // of modeling "pointers as integers" is not complete.
560  return UnknownVal();
561  return evalBinOpLL(state, op, lhsL,
562  rhs.castAs<nonloc::LocAsInteger>().getLoc(),
563  resultTy);
564  case nonloc::ConcreteIntKind: {
565  // FIXME: at the moment the implementation
566  // of modeling "pointers as integers" is not complete.
568  return UnknownVal();
569  // Transform the integer into a location and compare.
570  // FIXME: This only makes sense for comparisons. If we want to, say,
571  // add 1 to a LocAsInteger, we'd better unpack the Loc and add to it,
572  // then pack it back into a LocAsInteger.
573  llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue();
574  BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i);
575  return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy);
576  }
577  default:
578  switch (op) {
579  case BO_EQ:
580  return makeTruthVal(false, resultTy);
581  case BO_NE:
582  return makeTruthVal(true, resultTy);
583  default:
584  // This case also handles pointer arithmetic.
585  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
586  }
587  }
588  }
589  case nonloc::ConcreteIntKind: {
590  llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue();
591 
592  // If we're dealing with two known constants, just perform the operation.
593  if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) {
594  llvm::APSInt RHSValue = *KnownRHSValue;
596  // We're looking for a type big enough to compare the two values.
597  // FIXME: This is not correct. char + short will result in a promotion
598  // to int. Unfortunately we have lost types by this point.
599  APSIntType CompareType = std::max(APSIntType(LHSValue),
600  APSIntType(RHSValue));
601  CompareType.apply(LHSValue);
602  CompareType.apply(RHSValue);
603  } else if (!BinaryOperator::isShiftOp(op)) {
604  APSIntType IntType = BasicVals.getAPSIntType(resultTy);
605  IntType.apply(LHSValue);
606  IntType.apply(RHSValue);
607  }
608 
609  const llvm::APSInt *Result =
610  BasicVals.evalAPSInt(op, LHSValue, RHSValue);
611  if (!Result)
612  return UndefinedVal();
613 
614  return nonloc::ConcreteInt(*Result);
615  }
616 
617  // Swap the left and right sides and flip the operator if doing so
618  // allows us to better reason about the expression (this is a form
619  // of expression canonicalization).
620  // While we're at it, catch some special cases for non-commutative ops.
621  switch (op) {
622  case BO_LT:
623  case BO_GT:
624  case BO_LE:
625  case BO_GE:
627  // FALL-THROUGH
628  case BO_EQ:
629  case BO_NE:
630  case BO_Add:
631  case BO_Mul:
632  case BO_And:
633  case BO_Xor:
634  case BO_Or:
635  std::swap(lhs, rhs);
636  continue;
637  case BO_Shr:
638  // (~0)>>a
639  if (LHSValue.isAllOnesValue() && LHSValue.isSigned())
640  return evalCastFromNonLoc(lhs, resultTy);
641  // FALL-THROUGH
642  case BO_Shl:
643  // 0<<a and 0>>a
644  if (LHSValue == 0)
645  return evalCastFromNonLoc(lhs, resultTy);
646  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
647  default:
648  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
649  }
650  }
651  case nonloc::SymbolValKind: {
652  // We only handle LHS as simple symbols or SymIntExprs.
653  SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol();
654 
655  // LHS is a symbolic expression.
656  if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) {
657 
658  // Is this a logical not? (!x is represented as x == 0.)
659  if (op == BO_EQ && rhs.isZeroConstant()) {
660  // We know how to negate certain expressions. Simplify them here.
661 
662  BinaryOperator::Opcode opc = symIntExpr->getOpcode();
663  switch (opc) {
664  default:
665  // We don't know how to negate this operation.
666  // Just handle it as if it were a normal comparison to 0.
667  break;
668  case BO_LAnd:
669  case BO_LOr:
670  llvm_unreachable("Logical operators handled by branching logic.");
671  case BO_Assign:
672  case BO_MulAssign:
673  case BO_DivAssign:
674  case BO_RemAssign:
675  case BO_AddAssign:
676  case BO_SubAssign:
677  case BO_ShlAssign:
678  case BO_ShrAssign:
679  case BO_AndAssign:
680  case BO_XorAssign:
681  case BO_OrAssign:
682  case BO_Comma:
683  llvm_unreachable("'=' and ',' operators handled by ExprEngine.");
684  case BO_PtrMemD:
685  case BO_PtrMemI:
686  llvm_unreachable("Pointer arithmetic not handled here.");
687  case BO_LT:
688  case BO_GT:
689  case BO_LE:
690  case BO_GE:
691  case BO_EQ:
692  case BO_NE:
693  assert(resultTy->isBooleanType() ||
694  resultTy == getConditionType());
695  assert(symIntExpr->getType()->isBooleanType() ||
696  getContext().hasSameUnqualifiedType(symIntExpr->getType(),
697  getConditionType()));
698  // Negate the comparison and make a value.
700  return makeNonLoc(symIntExpr->getLHS(), opc,
701  symIntExpr->getRHS(), resultTy);
702  }
703  }
704 
705  // For now, only handle expressions whose RHS is a constant.
706  if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) {
707  // If both the LHS and the current expression are additive,
708  // fold their constants and try again.
710  BinaryOperator::Opcode lop = symIntExpr->getOpcode();
711  if (BinaryOperator::isAdditiveOp(lop)) {
712  // Convert the two constants to a common type, then combine them.
713 
714  // resultTy may not be the best type to convert to, but it's
715  // probably the best choice in expressions with mixed type
716  // (such as x+1U+2LL). The rules for implicit conversions should
717  // choose a reasonable type to preserve the expression, and will
718  // at least match how the value is going to be used.
719  APSIntType IntType = BasicVals.getAPSIntType(resultTy);
720  const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());
721  const llvm::APSInt &second = IntType.convert(*RHSValue);
722 
723  const llvm::APSInt *newRHS;
724  if (lop == op)
725  newRHS = BasicVals.evalAPSInt(BO_Add, first, second);
726  else
727  newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);
728 
729  assert(newRHS && "Invalid operation despite common type!");
730  rhs = nonloc::ConcreteInt(*newRHS);
731  lhs = nonloc::SymbolVal(symIntExpr->getLHS());
732  op = lop;
733  continue;
734  }
735  }
736 
737  // Otherwise, make a SymIntExpr out of the expression.
738  return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy);
739  }
740  }
741 
742  // Does the symbolic expression simplify to a constant?
743  // If so, "fold" the constant by setting 'lhs' to a ConcreteInt
744  // and try again.
745  SVal simplifiedLhs = simplifySVal(state, lhs);
746  if (simplifiedLhs != lhs)
747  if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) {
748  lhs = *simplifiedLhsAsNonLoc;
749  continue;
750  }
751 
752  // Is the RHS a constant?
753  if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs))
754  return MakeSymIntVal(Sym, op, *RHSValue, resultTy);
755 
756  if (Optional<NonLoc> V = tryRearrange(state, op, lhs, rhs, resultTy))
757  return *V;
758 
759  // Give up -- this is not a symbolic expression we can handle.
760  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
761  }
762  }
763  }
764 }
765 
766 static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR,
767  const FieldRegion *RightFR,
769  QualType resultTy,
770  SimpleSValBuilder &SVB) {
771  // Only comparisons are meaningful here!
773  return UnknownVal();
774 
775  // Next, see if the two FRs have the same super-region.
776  // FIXME: This doesn't handle casts yet, and simply stripping the casts
777  // doesn't help.
778  if (LeftFR->getSuperRegion() != RightFR->getSuperRegion())
779  return UnknownVal();
780 
781  const FieldDecl *LeftFD = LeftFR->getDecl();
782  const FieldDecl *RightFD = RightFR->getDecl();
783  const RecordDecl *RD = LeftFD->getParent();
784 
785  // Make sure the two FRs are from the same kind of record. Just in case!
786  // FIXME: This is probably where inheritance would be a problem.
787  if (RD != RightFD->getParent())
788  return UnknownVal();
789 
790  // We know for sure that the two fields are not the same, since that
791  // would have given us the same SVal.
792  if (op == BO_EQ)
793  return SVB.makeTruthVal(false, resultTy);
794  if (op == BO_NE)
795  return SVB.makeTruthVal(true, resultTy);
796 
797  // Iterate through the fields and see which one comes first.
798  // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field
799  // members and the units in which bit-fields reside have addresses that
800  // increase in the order in which they are declared."
801  bool leftFirst = (op == BO_LT || op == BO_LE);
802  for (const auto *I : RD->fields()) {
803  if (I == LeftFD)
804  return SVB.makeTruthVal(leftFirst, resultTy);
805  if (I == RightFD)
806  return SVB.makeTruthVal(!leftFirst, resultTy);
807  }
808 
809  llvm_unreachable("Fields not found in parent record's definition");
810 }
811 
812 // FIXME: all this logic will change if/when we have MemRegion::getLocation().
813 SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state,
815  Loc lhs, Loc rhs,
816  QualType resultTy) {
817  // Only comparisons and subtractions are valid operations on two pointers.
818  // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15].
819  // However, if a pointer is casted to an integer, evalBinOpNN may end up
820  // calling this function with another operation (PR7527). We don't attempt to
821  // model this for now, but it could be useful, particularly when the
822  // "location" is actually an integer value that's been passed through a void*.
823  if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub))
824  return UnknownVal();
825 
826  // Special cases for when both sides are identical.
827  if (lhs == rhs) {
828  switch (op) {
829  default:
830  llvm_unreachable("Unimplemented operation for two identical values");
831  case BO_Sub:
832  return makeZeroVal(resultTy);
833  case BO_EQ:
834  case BO_LE:
835  case BO_GE:
836  return makeTruthVal(true, resultTy);
837  case BO_NE:
838  case BO_LT:
839  case BO_GT:
840  return makeTruthVal(false, resultTy);
841  }
842  }
843 
844  switch (lhs.getSubKind()) {
845  default:
846  llvm_unreachable("Ordering not implemented for this Loc.");
847 
848  case loc::GotoLabelKind:
849  // The only thing we know about labels is that they're non-null.
850  if (rhs.isZeroConstant()) {
851  switch (op) {
852  default:
853  break;
854  case BO_Sub:
855  return evalCastFromLoc(lhs, resultTy);
856  case BO_EQ:
857  case BO_LE:
858  case BO_LT:
859  return makeTruthVal(false, resultTy);
860  case BO_NE:
861  case BO_GT:
862  case BO_GE:
863  return makeTruthVal(true, resultTy);
864  }
865  }
866  // There may be two labels for the same location, and a function region may
867  // have the same address as a label at the start of the function (depending
868  // on the ABI).
869  // FIXME: we can probably do a comparison against other MemRegions, though.
870  // FIXME: is there a way to tell if two labels refer to the same location?
871  return UnknownVal();
872 
873  case loc::ConcreteIntKind: {
874  // If one of the operands is a symbol and the other is a constant,
875  // build an expression for use by the constraint manager.
876  if (SymbolRef rSym = rhs.getAsLocSymbol()) {
877  // We can only build expressions with symbols on the left,
878  // so we need a reversible operator.
879  if (!BinaryOperator::isComparisonOp(op) || op == BO_Cmp)
880  return UnknownVal();
881 
882  const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue();
884  return makeNonLoc(rSym, op, lVal, resultTy);
885  }
886 
887  // If both operands are constants, just perform the operation.
888  if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
889  SVal ResultVal =
890  lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt);
891  if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>())
892  return evalCastFromNonLoc(*Result, resultTy);
893 
894  assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs");
895  return UnknownVal();
896  }
897 
898  // Special case comparisons against NULL.
899  // This must come after the test if the RHS is a symbol, which is used to
900  // build constraints. The address of any non-symbolic region is guaranteed
901  // to be non-NULL, as is any label.
902  assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>());
903  if (lhs.isZeroConstant()) {
904  switch (op) {
905  default:
906  break;
907  case BO_EQ:
908  case BO_GT:
909  case BO_GE:
910  return makeTruthVal(false, resultTy);
911  case BO_NE:
912  case BO_LT:
913  case BO_LE:
914  return makeTruthVal(true, resultTy);
915  }
916  }
917 
918  // Comparing an arbitrary integer to a region or label address is
919  // completely unknowable.
920  return UnknownVal();
921  }
922  case loc::MemRegionValKind: {
923  if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
924  // If one of the operands is a symbol and the other is a constant,
925  // build an expression for use by the constraint manager.
926  if (SymbolRef lSym = lhs.getAsLocSymbol(true)) {
928  return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy);
929  return UnknownVal();
930  }
931  // Special case comparisons to NULL.
932  // This must come after the test if the LHS is a symbol, which is used to
933  // build constraints. The address of any non-symbolic region is guaranteed
934  // to be non-NULL.
935  if (rInt->isZeroConstant()) {
936  if (op == BO_Sub)
937  return evalCastFromLoc(lhs, resultTy);
938 
940  QualType boolType = getContext().BoolTy;
941  NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>();
942  NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>();
943  return evalBinOpNN(state, op, l, r, resultTy);
944  }
945  }
946 
947  // Comparing a region to an arbitrary integer is completely unknowable.
948  return UnknownVal();
949  }
950 
951  // Get both values as regions, if possible.
952  const MemRegion *LeftMR = lhs.getAsRegion();
953  assert(LeftMR && "MemRegionValKind SVal doesn't have a region!");
954 
955  const MemRegion *RightMR = rhs.getAsRegion();
956  if (!RightMR)
957  // The RHS is probably a label, which in theory could address a region.
958  // FIXME: we can probably make a more useful statement about non-code
959  // regions, though.
960  return UnknownVal();
961 
962  const MemRegion *LeftBase = LeftMR->getBaseRegion();
963  const MemRegion *RightBase = RightMR->getBaseRegion();
964  const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace();
965  const MemSpaceRegion *RightMS = RightBase->getMemorySpace();
966  const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion();
967 
968  // If the two regions are from different known memory spaces they cannot be
969  // equal. Also, assume that no symbolic region (whose memory space is
970  // unknown) is on the stack.
971  if (LeftMS != RightMS &&
972  ((LeftMS != UnknownMS && RightMS != UnknownMS) ||
973  (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) {
974  switch (op) {
975  default:
976  return UnknownVal();
977  case BO_EQ:
978  return makeTruthVal(false, resultTy);
979  case BO_NE:
980  return makeTruthVal(true, resultTy);
981  }
982  }
983 
984  // If both values wrap regions, see if they're from different base regions.
985  // Note, heap base symbolic regions are assumed to not alias with
986  // each other; for example, we assume that malloc returns different address
987  // on each invocation.
988  // FIXME: ObjC object pointers always reside on the heap, but currently
989  // we treat their memory space as unknown, because symbolic pointers
990  // to ObjC objects may alias. There should be a way to construct
991  // possibly-aliasing heap-based regions. For instance, MacOSXApiChecker
992  // guesses memory space for ObjC object pointers manually instead of
993  // relying on us.
994  if (LeftBase != RightBase &&
995  ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) ||
996  (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){
997  switch (op) {
998  default:
999  return UnknownVal();
1000  case BO_EQ:
1001  return makeTruthVal(false, resultTy);
1002  case BO_NE:
1003  return makeTruthVal(true, resultTy);
1004  }
1005  }
1006 
1007  // Handle special cases for when both regions are element regions.
1008  const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR);
1009  const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR);
1010  if (RightER && LeftER) {
1011  // Next, see if the two ERs have the same super-region and matching types.
1012  // FIXME: This should do something useful even if the types don't match,
1013  // though if both indexes are constant the RegionRawOffset path will
1014  // give the correct answer.
1015  if (LeftER->getSuperRegion() == RightER->getSuperRegion() &&
1016  LeftER->getElementType() == RightER->getElementType()) {
1017  // Get the left index and cast it to the correct type.
1018  // If the index is unknown or undefined, bail out here.
1019  SVal LeftIndexVal = LeftER->getIndex();
1020  Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>();
1021  if (!LeftIndex)
1022  return UnknownVal();
1023  LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy);
1024  LeftIndex = LeftIndexVal.getAs<NonLoc>();
1025  if (!LeftIndex)
1026  return UnknownVal();
1027 
1028  // Do the same for the right index.
1029  SVal RightIndexVal = RightER->getIndex();
1030  Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>();
1031  if (!RightIndex)
1032  return UnknownVal();
1033  RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy);
1034  RightIndex = RightIndexVal.getAs<NonLoc>();
1035  if (!RightIndex)
1036  return UnknownVal();
1037 
1038  // Actually perform the operation.
1039  // evalBinOpNN expects the two indexes to already be the right type.
1040  return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy);
1041  }
1042  }
1043 
1044  // Special handling of the FieldRegions, even with symbolic offsets.
1045  const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR);
1046  const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR);
1047  if (RightFR && LeftFR) {
1048  SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy,
1049  *this);
1050  if (!R.isUnknown())
1051  return R;
1052  }
1053 
1054  // Compare the regions using the raw offsets.
1055  RegionOffset LeftOffset = LeftMR->getAsOffset();
1056  RegionOffset RightOffset = RightMR->getAsOffset();
1057 
1058  if (LeftOffset.getRegion() != nullptr &&
1059  LeftOffset.getRegion() == RightOffset.getRegion() &&
1060  !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) {
1061  int64_t left = LeftOffset.getOffset();
1062  int64_t right = RightOffset.getOffset();
1063 
1064  switch (op) {
1065  default:
1066  return UnknownVal();
1067  case BO_LT:
1068  return makeTruthVal(left < right, resultTy);
1069  case BO_GT:
1070  return makeTruthVal(left > right, resultTy);
1071  case BO_LE:
1072  return makeTruthVal(left <= right, resultTy);
1073  case BO_GE:
1074  return makeTruthVal(left >= right, resultTy);
1075  case BO_EQ:
1076  return makeTruthVal(left == right, resultTy);
1077  case BO_NE:
1078  return makeTruthVal(left != right, resultTy);
1079  }
1080  }
1081 
1082  // At this point we're not going to get a good answer, but we can try
1083  // conjuring an expression instead.
1084  SymbolRef LHSSym = lhs.getAsLocSymbol();
1085  SymbolRef RHSSym = rhs.getAsLocSymbol();
1086  if (LHSSym && RHSSym)
1087  return makeNonLoc(LHSSym, op, RHSSym, resultTy);
1088 
1089  // If we get here, we have no way of comparing the regions.
1090  return UnknownVal();
1091  }
1092  }
1093 }
1094 
1095 SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,
1097  Loc lhs, NonLoc rhs, QualType resultTy) {
1098  if (op >= BO_PtrMemD && op <= BO_PtrMemI) {
1099  if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) {
1100  if (PTMSV->isNullMemberPointer())
1101  return UndefinedVal();
1102  if (const FieldDecl *FD = PTMSV->getDeclAs<FieldDecl>()) {
1103  SVal Result = lhs;
1104 
1105  for (const auto &I : *PTMSV)
1106  Result = StateMgr.getStoreManager().evalDerivedToBase(
1107  Result, I->getType(),I->isVirtual());
1108  return state->getLValue(FD, Result);
1109  }
1110  }
1111 
1112  return rhs;
1113  }
1114 
1115  assert(!BinaryOperator::isComparisonOp(op) &&
1116  "arguments to comparison ops must be of the same type");
1117 
1118  // Special case: rhs is a zero constant.
1119  if (rhs.isZeroConstant())
1120  return lhs;
1121 
1122  // Perserve the null pointer so that it can be found by the DerefChecker.
1123  if (lhs.isZeroConstant())
1124  return lhs;
1125 
1126  // We are dealing with pointer arithmetic.
1127 
1128  // Handle pointer arithmetic on constant values.
1129  if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) {
1130  if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) {
1131  const llvm::APSInt &leftI = lhsInt->getValue();
1132  assert(leftI.isUnsigned());
1133  llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true);
1134 
1135  // Convert the bitwidth of rightI. This should deal with overflow
1136  // since we are dealing with concrete values.
1137  rightI = rightI.extOrTrunc(leftI.getBitWidth());
1138 
1139  // Offset the increment by the pointer size.
1140  llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);
1141  QualType pointeeType = resultTy->getPointeeType();
1142  Multiplicand = getContext().getTypeSizeInChars(pointeeType).getQuantity();
1143  rightI *= Multiplicand;
1144 
1145  // Compute the adjusted pointer.
1146  switch (op) {
1147  case BO_Add:
1148  rightI = leftI + rightI;
1149  break;
1150  case BO_Sub:
1151  rightI = leftI - rightI;
1152  break;
1153  default:
1154  llvm_unreachable("Invalid pointer arithmetic operation");
1155  }
1156  return loc::ConcreteInt(getBasicValueFactory().getValue(rightI));
1157  }
1158  }
1159 
1160  // Handle cases where 'lhs' is a region.
1161  if (const MemRegion *region = lhs.getAsRegion()) {
1162  rhs = convertToArrayIndex(rhs).castAs<NonLoc>();
1163  SVal index = UnknownVal();
1164  const SubRegion *superR = nullptr;
1165  // We need to know the type of the pointer in order to add an integer to it.
1166  // Depending on the type, different amount of bytes is added.
1167  QualType elementType;
1168 
1169  if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) {
1170  assert(op == BO_Add || op == BO_Sub);
1171  index = evalBinOpNN(state, op, elemReg->getIndex(), rhs,
1172  getArrayIndexType());
1173  superR = cast<SubRegion>(elemReg->getSuperRegion());
1174  elementType = elemReg->getElementType();
1175  }
1176  else if (isa<SubRegion>(region)) {
1177  assert(op == BO_Add || op == BO_Sub);
1178  index = (op == BO_Add) ? rhs : evalMinus(rhs);
1179  superR = cast<SubRegion>(region);
1180  // TODO: Is this actually reliable? Maybe improving our MemRegion
1181  // hierarchy to provide typed regions for all non-void pointers would be
1182  // better. For instance, we cannot extend this towards LocAsInteger
1183  // operations, where result type of the expression is integer.
1184  if (resultTy->isAnyPointerType())
1185  elementType = resultTy->getPointeeType();
1186  }
1187 
1188  // Represent arithmetic on void pointers as arithmetic on char pointers.
1189  // It is fine when a TypedValueRegion of char value type represents
1190  // a void pointer. Note that arithmetic on void pointers is a GCC extension.
1191  if (elementType->isVoidType())
1192  elementType = getContext().CharTy;
1193 
1194  if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
1195  return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
1196  superR, getContext()));
1197  }
1198  }
1199  return UnknownVal();
1200 }
1201 
1202 const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state,
1203  SVal V) {
1204  V = simplifySVal(state, V);
1205  if (V.isUnknownOrUndef())
1206  return nullptr;
1207 
1208  if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>())
1209  return &X->getValue();
1210 
1211  if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>())
1212  return &X->getValue();
1213 
1214  if (SymbolRef Sym = V.getAsSymbol())
1215  return state->getConstraintManager().getSymVal(state, Sym);
1216 
1217  // FIXME: Add support for SymExprs.
1218  return nullptr;
1219 }
1220 
1221 SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) {
1222  // For now, this function tries to constant-fold symbols inside a
1223  // nonloc::SymbolVal, and does nothing else. More simplifications should
1224  // be possible, such as constant-folding an index in an ElementRegion.
1225 
1226  class Simplifier : public FullSValVisitor<Simplifier, SVal> {
1228  SValBuilder &SVB;
1229 
1230  // Cache results for the lifetime of the Simplifier. Results change every
1231  // time new constraints are added to the program state, which is the whole
1232  // point of simplifying, and for that very reason it's pointless to maintain
1233  // the same cache for the duration of the whole analysis.
1234  llvm::DenseMap<SymbolRef, SVal> Cached;
1235 
1236  static bool isUnchanged(SymbolRef Sym, SVal Val) {
1237  return Sym == Val.getAsSymbol();
1238  }
1239 
1240  SVal cache(SymbolRef Sym, SVal V) {
1241  Cached[Sym] = V;
1242  return V;
1243  }
1244 
1245  SVal skip(SymbolRef Sym) {
1246  return cache(Sym, SVB.makeSymbolVal(Sym));
1247  }
1248 
1249  public:
1250  Simplifier(ProgramStateRef State)
1251  : State(State), SVB(State->getStateManager().getSValBuilder()) {}
1252 
1253  SVal VisitSymbolData(const SymbolData *S) {
1254  // No cache here.
1255  if (const llvm::APSInt *I =
1256  SVB.getKnownValue(State, SVB.makeSymbolVal(S)))
1257  return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I)
1258  : (SVal)SVB.makeIntVal(*I);
1259  return SVB.makeSymbolVal(S);
1260  }
1261 
1262  // TODO: Support SymbolCast. Support IntSymExpr when/if we actually
1263  // start producing them.
1264 
1265  SVal VisitSymIntExpr(const SymIntExpr *S) {
1266  auto I = Cached.find(S);
1267  if (I != Cached.end())
1268  return I->second;
1269 
1270  SVal LHS = Visit(S->getLHS());
1271  if (isUnchanged(S->getLHS(), LHS))
1272  return skip(S);
1273 
1274  SVal RHS;
1275  // By looking at the APSInt in the right-hand side of S, we cannot
1276  // figure out if it should be treated as a Loc or as a NonLoc.
1277  // So make our guess by recalling that we cannot multiply pointers
1278  // or compare a pointer to an integer.
1279  if (Loc::isLocType(S->getLHS()->getType()) &&
1280  BinaryOperator::isComparisonOp(S->getOpcode())) {
1281  // The usual conversion of $sym to &SymRegion{$sym}, as they have
1282  // the same meaning for Loc-type symbols, but the latter form
1283  // is preferred in SVal computations for being Loc itself.
1284  if (SymbolRef Sym = LHS.getAsSymbol()) {
1285  assert(Loc::isLocType(Sym->getType()));
1286  LHS = SVB.makeLoc(Sym);
1287  }
1288  RHS = SVB.makeIntLocVal(S->getRHS());
1289  } else {
1290  RHS = SVB.makeIntVal(S->getRHS());
1291  }
1292 
1293  return cache(
1294  S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));
1295  }
1296 
1297  SVal VisitSymSymExpr(const SymSymExpr *S) {
1298  auto I = Cached.find(S);
1299  if (I != Cached.end())
1300  return I->second;
1301 
1302  // For now don't try to simplify mixed Loc/NonLoc expressions
1303  // because they often appear from LocAsInteger operations
1304  // and we don't know how to combine a LocAsInteger
1305  // with a concrete value.
1306  if (Loc::isLocType(S->getLHS()->getType()) !=
1307  Loc::isLocType(S->getRHS()->getType()))
1308  return skip(S);
1309 
1310  SVal LHS = Visit(S->getLHS());
1311  SVal RHS = Visit(S->getRHS());
1312  if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS))
1313  return skip(S);
1314 
1315  return cache(
1316  S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));
1317  }
1318 
1319  SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); }
1320 
1321  SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); }
1322 
1323  SVal VisitNonLocSymbolVal(nonloc::SymbolVal V) {
1324  // Simplification is much more costly than computing complexity.
1325  // For high complexity, it may be not worth it.
1326  return Visit(V.getSymbol());
1327  }
1328 
1329  SVal VisitSVal(SVal V) { return V; }
1330  };
1331 
1332  // A crude way of preventing this function from calling itself from evalBinOp.
1333  static bool isReentering = false;
1334  if (isReentering)
1335  return V;
1336 
1337  isReentering = true;
1338  SVal SimplifiedV = Simplifier(State).Visit(V);
1339  isReentering = false;
1340 
1341  return SimplifiedV;
1342 }
Represents a function declaration or definition.
Definition: Decl.h:1717
if(T->getSizeExpr()) TRY_TO(TraverseStmt(T -> getSizeExpr()))
CanQualType VoidPtrTy
Definition: ASTContext.h:1053
A (possibly-)qualified type.
Definition: Type.h:642
MemRegion - The root abstract class for all memory regions.
Definition: MemRegion.h:94
const SymExpr * SymbolRef
SValBuilder * createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context, ProgramStateManager &stateMgr)
QualType getPointeeType() const
If this is a pointer, ObjC object pointer, or block pointer, this returns the respective pointee...
Definition: Type.cpp:497
static bool isWithinConstantOverflowBounds(SymbolRef Sym, ProgramStateRef State)
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
const RecordDecl * getParent() const
Returns the parent of this field declaration, which is the struct in which this field is defined...
Definition: Decl.h:2740
Value representing integer constant.
Definition: SVals.h:377
bool isAdditiveOp() const
Definition: Expr.h:3179
Symbolic value.
Definition: SymExpr.h:30
Represents a struct/union/class.
Definition: Decl.h:3570
const SymbolicRegion * getSymbolicBase() const
If this is a symbolic region, returns the region.
Definition: MemRegion.cpp:1209
static NonLoc doRearrangeUnchecked(ProgramStateRef State, BinaryOperator::Opcode Op, SymbolRef LSym, llvm::APSInt LInt, SymbolRef RSym, llvm::APSInt RInt)
static Opcode reverseComparisonOp(Opcode Opc)
Definition: Expr.h:3208
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:154
static bool isInRelation(BinaryOperator::Opcode Rel, SymbolRef Sym, llvm::APSInt Bound, ProgramStateRef State)
Value representing pointer-to-member.
Definition: SVals.h:522
LineState State
field_range fields() const
Definition: Decl.h:3761
Represents a member of a struct/union/class.
Definition: Decl.h:2556
bool isReferenceType() const
Definition: Type.h:6189
i32 captured_struct **param SharedsTy A type which contains references the shared variables *param Shareds Context with the list of shared variables from the p *TaskFunction *param Data Additional data for task generation like final * state
const SymExpr * getAsSymbolicExpression() const
getAsSymbolicExpression - If this Sval wraps a symbolic expression then return that expression...
Definition: SVals.cpp:137
bool isIntegralOrEnumerationType() const
Determine whether this type is an integral or enumeration type.
Definition: Type.h:6504
static bool isLocType(QualType T)
Definition: SVals.h:327
BinaryOperatorKind
static bool shouldRearrange(ProgramStateRef State, BinaryOperator::Opcode Op, SymbolRef Sym, llvm::APSInt Int, QualType Ty)
virtual QualType getType() const =0
static std::pair< SymbolRef, llvm::APSInt > decomposeSymbol(SymbolRef Sym, BasicValueFactory &BV)
static Opcode negateComparisonOp(Opcode Opc)
Definition: Expr.h:3195
unsigned getSubKind() const
Definition: SVals.h:120
SymbolicRegion - A special, "non-concrete" region.
Definition: MemRegion.h:759
static SVal getValue(SVal val, SValBuilder &svalBuilder)
bool isUnionType() const
Definition: Type.cpp:467
bool isNull() const
Return true if this QualType doesn&#39;t point to a type yet.
Definition: Type.h:707
Optional< T > getAs() const
Convert to the specified SVal type, returning None if this SVal is not of the desired type...
Definition: SVals.h:112
bool isComparisonOp() const
Definition: Expr.h:3193
FunctionCodeRegion - A region that represents code texts of function.
Definition: MemRegion.h:576
SVal - This represents a symbolic expression, which can be either an L-value or an R-value...
Definition: SVals.h:76
bool isSignedIntegerOrEnumerationType() const
Determines whether this is an integer type that is signed or an enumeration types whose underlying ty...
Definition: Type.cpp:1852
bool isAnyPointerType() const
Definition: Type.h:6181
Dataflow Directional Tag Classes.
bool isShiftOp() const
Definition: Expr.h:3181
bool isBooleanType() const
Definition: Type.h:6517
Represents symbolic expression that isn&#39;t a location.
Definition: SVals.h:347
unsigned getIntWidth(QualType T) const
T castAs() const
Convert to the specified SVal type, asserting that this SVal is of the desired type.
Definition: SVals.h:104
uint64_t getTypeSize(QualType T) const
Return the size of the specified (complete) type T, in bits.
Definition: ASTContext.h:2076
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:2259
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:13824
bool isVoidType() const
Definition: Type.h:6404
static Optional< NonLoc > tryRearrange(ProgramStateRef State, BinaryOperator::Opcode Op, NonLoc Lhs, NonLoc Rhs, QualType ResultTy)
__DEVICE__ int max(int __a, int __b)
static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR, const FieldRegion *RightFR, BinaryOperator::Opcode op, QualType resultTy, SimpleSValBuilder &SVB)