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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  } else {
479  // Don't rearrange other operations.
480  return None;
481  }
482 
483  assert(!SingleTy.isNull() && "We should have figured out the type by now!");
484 
485  // Rearrange signed symbolic expressions only
486  if (!SingleTy->isSignedIntegerOrEnumerationType())
487  return None;
488 
489  SymbolRef RSym = Rhs.getAsSymbol();
490  if (!RSym || RSym->getType() != SingleTy)
491  return None;
492 
493  BasicValueFactory &BV = State->getBasicVals();
494  llvm::APSInt LInt, RInt;
495  std::tie(LSym, LInt) = decomposeSymbol(LSym, BV);
496  std::tie(RSym, RInt) = decomposeSymbol(RSym, BV);
497  if (!shouldRearrange(State, Op, LSym, LInt, SingleTy) ||
498  !shouldRearrange(State, Op, RSym, RInt, SingleTy))
499  return None;
500 
501  // We know that no overflows can occur anymore.
502  return doRearrangeUnchecked(State, Op, LSym, LInt, RSym, RInt);
503 }
504 
505 SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
507  NonLoc lhs, NonLoc rhs,
508  QualType resultTy) {
509  NonLoc InputLHS = lhs;
510  NonLoc InputRHS = rhs;
511 
512  // Handle trivial case where left-side and right-side are the same.
513  if (lhs == rhs)
514  switch (op) {
515  default:
516  break;
517  case BO_EQ:
518  case BO_LE:
519  case BO_GE:
520  return makeTruthVal(true, resultTy);
521  case BO_LT:
522  case BO_GT:
523  case BO_NE:
524  return makeTruthVal(false, resultTy);
525  case BO_Xor:
526  case BO_Sub:
527  if (resultTy->isIntegralOrEnumerationType())
528  return makeIntVal(0, resultTy);
529  return evalCastFromNonLoc(makeIntVal(0, /*Unsigned=*/false), resultTy);
530  case BO_Or:
531  case BO_And:
532  return evalCastFromNonLoc(lhs, resultTy);
533  }
534 
535  while (1) {
536  switch (lhs.getSubKind()) {
537  default:
538  return makeSymExprValNN(op, lhs, rhs, resultTy);
539  case nonloc::PointerToMemberKind: {
540  assert(rhs.getSubKind() == nonloc::PointerToMemberKind &&
541  "Both SVals should have pointer-to-member-type");
542  auto LPTM = lhs.castAs<nonloc::PointerToMember>(),
543  RPTM = rhs.castAs<nonloc::PointerToMember>();
544  auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData();
545  switch (op) {
546  case BO_EQ:
547  return makeTruthVal(LPTMD == RPTMD, resultTy);
548  case BO_NE:
549  return makeTruthVal(LPTMD != RPTMD, resultTy);
550  default:
551  return UnknownVal();
552  }
553  }
554  case nonloc::LocAsIntegerKind: {
555  Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc();
556  switch (rhs.getSubKind()) {
557  case nonloc::LocAsIntegerKind:
558  // FIXME: at the moment the implementation
559  // of modeling "pointers as integers" is not complete.
561  return UnknownVal();
562  return evalBinOpLL(state, op, lhsL,
563  rhs.castAs<nonloc::LocAsInteger>().getLoc(),
564  resultTy);
565  case nonloc::ConcreteIntKind: {
566  // FIXME: at the moment the implementation
567  // of modeling "pointers as integers" is not complete.
569  return UnknownVal();
570  // Transform the integer into a location and compare.
571  // FIXME: This only makes sense for comparisons. If we want to, say,
572  // add 1 to a LocAsInteger, we'd better unpack the Loc and add to it,
573  // then pack it back into a LocAsInteger.
574  llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue();
575  BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i);
576  return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy);
577  }
578  default:
579  switch (op) {
580  case BO_EQ:
581  return makeTruthVal(false, resultTy);
582  case BO_NE:
583  return makeTruthVal(true, resultTy);
584  default:
585  // This case also handles pointer arithmetic.
586  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
587  }
588  }
589  }
590  case nonloc::ConcreteIntKind: {
591  llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue();
592 
593  // If we're dealing with two known constants, just perform the operation.
594  if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) {
595  llvm::APSInt RHSValue = *KnownRHSValue;
597  // We're looking for a type big enough to compare the two values.
598  // FIXME: This is not correct. char + short will result in a promotion
599  // to int. Unfortunately we have lost types by this point.
600  APSIntType CompareType = std::max(APSIntType(LHSValue),
601  APSIntType(RHSValue));
602  CompareType.apply(LHSValue);
603  CompareType.apply(RHSValue);
604  } else if (!BinaryOperator::isShiftOp(op)) {
605  APSIntType IntType = BasicVals.getAPSIntType(resultTy);
606  IntType.apply(LHSValue);
607  IntType.apply(RHSValue);
608  }
609 
610  const llvm::APSInt *Result =
611  BasicVals.evalAPSInt(op, LHSValue, RHSValue);
612  if (!Result)
613  return UndefinedVal();
614 
615  return nonloc::ConcreteInt(*Result);
616  }
617 
618  // Swap the left and right sides and flip the operator if doing so
619  // allows us to better reason about the expression (this is a form
620  // of expression canonicalization).
621  // While we're at it, catch some special cases for non-commutative ops.
622  switch (op) {
623  case BO_LT:
624  case BO_GT:
625  case BO_LE:
626  case BO_GE:
628  LLVM_FALLTHROUGH;
629  case BO_EQ:
630  case BO_NE:
631  case BO_Add:
632  case BO_Mul:
633  case BO_And:
634  case BO_Xor:
635  case BO_Or:
636  std::swap(lhs, rhs);
637  continue;
638  case BO_Shr:
639  // (~0)>>a
640  if (LHSValue.isAllOnesValue() && LHSValue.isSigned())
641  return evalCastFromNonLoc(lhs, resultTy);
642  LLVM_FALLTHROUGH;
643  case BO_Shl:
644  // 0<<a and 0>>a
645  if (LHSValue == 0)
646  return evalCastFromNonLoc(lhs, resultTy);
647  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
648  default:
649  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
650  }
651  }
652  case nonloc::SymbolValKind: {
653  // We only handle LHS as simple symbols or SymIntExprs.
654  SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol();
655 
656  // LHS is a symbolic expression.
657  if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) {
658 
659  // Is this a logical not? (!x is represented as x == 0.)
660  if (op == BO_EQ && rhs.isZeroConstant()) {
661  // We know how to negate certain expressions. Simplify them here.
662 
663  BinaryOperator::Opcode opc = symIntExpr->getOpcode();
664  switch (opc) {
665  default:
666  // We don't know how to negate this operation.
667  // Just handle it as if it were a normal comparison to 0.
668  break;
669  case BO_LAnd:
670  case BO_LOr:
671  llvm_unreachable("Logical operators handled by branching logic.");
672  case BO_Assign:
673  case BO_MulAssign:
674  case BO_DivAssign:
675  case BO_RemAssign:
676  case BO_AddAssign:
677  case BO_SubAssign:
678  case BO_ShlAssign:
679  case BO_ShrAssign:
680  case BO_AndAssign:
681  case BO_XorAssign:
682  case BO_OrAssign:
683  case BO_Comma:
684  llvm_unreachable("'=' and ',' operators handled by ExprEngine.");
685  case BO_PtrMemD:
686  case BO_PtrMemI:
687  llvm_unreachable("Pointer arithmetic not handled here.");
688  case BO_LT:
689  case BO_GT:
690  case BO_LE:
691  case BO_GE:
692  case BO_EQ:
693  case BO_NE:
694  assert(resultTy->isBooleanType() ||
695  resultTy == getConditionType());
696  assert(symIntExpr->getType()->isBooleanType() ||
697  getContext().hasSameUnqualifiedType(symIntExpr->getType(),
698  getConditionType()));
699  // Negate the comparison and make a value.
701  return makeNonLoc(symIntExpr->getLHS(), opc,
702  symIntExpr->getRHS(), resultTy);
703  }
704  }
705 
706  // For now, only handle expressions whose RHS is a constant.
707  if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) {
708  // If both the LHS and the current expression are additive,
709  // fold their constants and try again.
711  BinaryOperator::Opcode lop = symIntExpr->getOpcode();
712  if (BinaryOperator::isAdditiveOp(lop)) {
713  // Convert the two constants to a common type, then combine them.
714 
715  // resultTy may not be the best type to convert to, but it's
716  // probably the best choice in expressions with mixed type
717  // (such as x+1U+2LL). The rules for implicit conversions should
718  // choose a reasonable type to preserve the expression, and will
719  // at least match how the value is going to be used.
720  APSIntType IntType = BasicVals.getAPSIntType(resultTy);
721  const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());
722  const llvm::APSInt &second = IntType.convert(*RHSValue);
723 
724  const llvm::APSInt *newRHS;
725  if (lop == op)
726  newRHS = BasicVals.evalAPSInt(BO_Add, first, second);
727  else
728  newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);
729 
730  assert(newRHS && "Invalid operation despite common type!");
731  rhs = nonloc::ConcreteInt(*newRHS);
732  lhs = nonloc::SymbolVal(symIntExpr->getLHS());
733  op = lop;
734  continue;
735  }
736  }
737 
738  // Otherwise, make a SymIntExpr out of the expression.
739  return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy);
740  }
741  }
742 
743  // Does the symbolic expression simplify to a constant?
744  // If so, "fold" the constant by setting 'lhs' to a ConcreteInt
745  // and try again.
746  SVal simplifiedLhs = simplifySVal(state, lhs);
747  if (simplifiedLhs != lhs)
748  if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) {
749  lhs = *simplifiedLhsAsNonLoc;
750  continue;
751  }
752 
753  // Is the RHS a constant?
754  if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs))
755  return MakeSymIntVal(Sym, op, *RHSValue, resultTy);
756 
757  if (Optional<NonLoc> V = tryRearrange(state, op, lhs, rhs, resultTy))
758  return *V;
759 
760  // Give up -- this is not a symbolic expression we can handle.
761  return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);
762  }
763  }
764  }
765 }
766 
767 static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR,
768  const FieldRegion *RightFR,
770  QualType resultTy,
771  SimpleSValBuilder &SVB) {
772  // Only comparisons are meaningful here!
774  return UnknownVal();
775 
776  // Next, see if the two FRs have the same super-region.
777  // FIXME: This doesn't handle casts yet, and simply stripping the casts
778  // doesn't help.
779  if (LeftFR->getSuperRegion() != RightFR->getSuperRegion())
780  return UnknownVal();
781 
782  const FieldDecl *LeftFD = LeftFR->getDecl();
783  const FieldDecl *RightFD = RightFR->getDecl();
784  const RecordDecl *RD = LeftFD->getParent();
785 
786  // Make sure the two FRs are from the same kind of record. Just in case!
787  // FIXME: This is probably where inheritance would be a problem.
788  if (RD != RightFD->getParent())
789  return UnknownVal();
790 
791  // We know for sure that the two fields are not the same, since that
792  // would have given us the same SVal.
793  if (op == BO_EQ)
794  return SVB.makeTruthVal(false, resultTy);
795  if (op == BO_NE)
796  return SVB.makeTruthVal(true, resultTy);
797 
798  // Iterate through the fields and see which one comes first.
799  // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field
800  // members and the units in which bit-fields reside have addresses that
801  // increase in the order in which they are declared."
802  bool leftFirst = (op == BO_LT || op == BO_LE);
803  for (const auto *I : RD->fields()) {
804  if (I == LeftFD)
805  return SVB.makeTruthVal(leftFirst, resultTy);
806  if (I == RightFD)
807  return SVB.makeTruthVal(!leftFirst, resultTy);
808  }
809 
810  llvm_unreachable("Fields not found in parent record's definition");
811 }
812 
813 // FIXME: all this logic will change if/when we have MemRegion::getLocation().
814 SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state,
816  Loc lhs, Loc rhs,
817  QualType resultTy) {
818  // Only comparisons and subtractions are valid operations on two pointers.
819  // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15].
820  // However, if a pointer is casted to an integer, evalBinOpNN may end up
821  // calling this function with another operation (PR7527). We don't attempt to
822  // model this for now, but it could be useful, particularly when the
823  // "location" is actually an integer value that's been passed through a void*.
824  if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub))
825  return UnknownVal();
826 
827  // Special cases for when both sides are identical.
828  if (lhs == rhs) {
829  switch (op) {
830  default:
831  llvm_unreachable("Unimplemented operation for two identical values");
832  case BO_Sub:
833  return makeZeroVal(resultTy);
834  case BO_EQ:
835  case BO_LE:
836  case BO_GE:
837  return makeTruthVal(true, resultTy);
838  case BO_NE:
839  case BO_LT:
840  case BO_GT:
841  return makeTruthVal(false, resultTy);
842  }
843  }
844 
845  switch (lhs.getSubKind()) {
846  default:
847  llvm_unreachable("Ordering not implemented for this Loc.");
848 
849  case loc::GotoLabelKind:
850  // The only thing we know about labels is that they're non-null.
851  if (rhs.isZeroConstant()) {
852  switch (op) {
853  default:
854  break;
855  case BO_Sub:
856  return evalCastFromLoc(lhs, resultTy);
857  case BO_EQ:
858  case BO_LE:
859  case BO_LT:
860  return makeTruthVal(false, resultTy);
861  case BO_NE:
862  case BO_GT:
863  case BO_GE:
864  return makeTruthVal(true, resultTy);
865  }
866  }
867  // There may be two labels for the same location, and a function region may
868  // have the same address as a label at the start of the function (depending
869  // on the ABI).
870  // FIXME: we can probably do a comparison against other MemRegions, though.
871  // FIXME: is there a way to tell if two labels refer to the same location?
872  return UnknownVal();
873 
874  case loc::ConcreteIntKind: {
875  // If one of the operands is a symbol and the other is a constant,
876  // build an expression for use by the constraint manager.
877  if (SymbolRef rSym = rhs.getAsLocSymbol()) {
878  // We can only build expressions with symbols on the left,
879  // so we need a reversible operator.
880  if (!BinaryOperator::isComparisonOp(op) || op == BO_Cmp)
881  return UnknownVal();
882 
883  const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue();
885  return makeNonLoc(rSym, op, lVal, resultTy);
886  }
887 
888  // If both operands are constants, just perform the operation.
889  if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
890  SVal ResultVal =
891  lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt);
892  if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>())
893  return evalCastFromNonLoc(*Result, resultTy);
894 
895  assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs");
896  return UnknownVal();
897  }
898 
899  // Special case comparisons against NULL.
900  // This must come after the test if the RHS is a symbol, which is used to
901  // build constraints. The address of any non-symbolic region is guaranteed
902  // to be non-NULL, as is any label.
903  assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>());
904  if (lhs.isZeroConstant()) {
905  switch (op) {
906  default:
907  break;
908  case BO_EQ:
909  case BO_GT:
910  case BO_GE:
911  return makeTruthVal(false, resultTy);
912  case BO_NE:
913  case BO_LT:
914  case BO_LE:
915  return makeTruthVal(true, resultTy);
916  }
917  }
918 
919  // Comparing an arbitrary integer to a region or label address is
920  // completely unknowable.
921  return UnknownVal();
922  }
923  case loc::MemRegionValKind: {
924  if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
925  // If one of the operands is a symbol and the other is a constant,
926  // build an expression for use by the constraint manager.
927  if (SymbolRef lSym = lhs.getAsLocSymbol(true)) {
929  return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy);
930  return UnknownVal();
931  }
932  // Special case comparisons to NULL.
933  // This must come after the test if the LHS is a symbol, which is used to
934  // build constraints. The address of any non-symbolic region is guaranteed
935  // to be non-NULL.
936  if (rInt->isZeroConstant()) {
937  if (op == BO_Sub)
938  return evalCastFromLoc(lhs, resultTy);
939 
941  QualType boolType = getContext().BoolTy;
942  NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>();
943  NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>();
944  return evalBinOpNN(state, op, l, r, resultTy);
945  }
946  }
947 
948  // Comparing a region to an arbitrary integer is completely unknowable.
949  return UnknownVal();
950  }
951 
952  // Get both values as regions, if possible.
953  const MemRegion *LeftMR = lhs.getAsRegion();
954  assert(LeftMR && "MemRegionValKind SVal doesn't have a region!");
955 
956  const MemRegion *RightMR = rhs.getAsRegion();
957  if (!RightMR)
958  // The RHS is probably a label, which in theory could address a region.
959  // FIXME: we can probably make a more useful statement about non-code
960  // regions, though.
961  return UnknownVal();
962 
963  const MemRegion *LeftBase = LeftMR->getBaseRegion();
964  const MemRegion *RightBase = RightMR->getBaseRegion();
965  const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace();
966  const MemSpaceRegion *RightMS = RightBase->getMemorySpace();
967  const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion();
968 
969  // If the two regions are from different known memory spaces they cannot be
970  // equal. Also, assume that no symbolic region (whose memory space is
971  // unknown) is on the stack.
972  if (LeftMS != RightMS &&
973  ((LeftMS != UnknownMS && RightMS != UnknownMS) ||
974  (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) {
975  switch (op) {
976  default:
977  return UnknownVal();
978  case BO_EQ:
979  return makeTruthVal(false, resultTy);
980  case BO_NE:
981  return makeTruthVal(true, resultTy);
982  }
983  }
984 
985  // If both values wrap regions, see if they're from different base regions.
986  // Note, heap base symbolic regions are assumed to not alias with
987  // each other; for example, we assume that malloc returns different address
988  // on each invocation.
989  // FIXME: ObjC object pointers always reside on the heap, but currently
990  // we treat their memory space as unknown, because symbolic pointers
991  // to ObjC objects may alias. There should be a way to construct
992  // possibly-aliasing heap-based regions. For instance, MacOSXApiChecker
993  // guesses memory space for ObjC object pointers manually instead of
994  // relying on us.
995  if (LeftBase != RightBase &&
996  ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) ||
997  (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){
998  switch (op) {
999  default:
1000  return UnknownVal();
1001  case BO_EQ:
1002  return makeTruthVal(false, resultTy);
1003  case BO_NE:
1004  return makeTruthVal(true, resultTy);
1005  }
1006  }
1007 
1008  // Handle special cases for when both regions are element regions.
1009  const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR);
1010  const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR);
1011  if (RightER && LeftER) {
1012  // Next, see if the two ERs have the same super-region and matching types.
1013  // FIXME: This should do something useful even if the types don't match,
1014  // though if both indexes are constant the RegionRawOffset path will
1015  // give the correct answer.
1016  if (LeftER->getSuperRegion() == RightER->getSuperRegion() &&
1017  LeftER->getElementType() == RightER->getElementType()) {
1018  // Get the left index and cast it to the correct type.
1019  // If the index is unknown or undefined, bail out here.
1020  SVal LeftIndexVal = LeftER->getIndex();
1021  Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>();
1022  if (!LeftIndex)
1023  return UnknownVal();
1024  LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy);
1025  LeftIndex = LeftIndexVal.getAs<NonLoc>();
1026  if (!LeftIndex)
1027  return UnknownVal();
1028 
1029  // Do the same for the right index.
1030  SVal RightIndexVal = RightER->getIndex();
1031  Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>();
1032  if (!RightIndex)
1033  return UnknownVal();
1034  RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy);
1035  RightIndex = RightIndexVal.getAs<NonLoc>();
1036  if (!RightIndex)
1037  return UnknownVal();
1038 
1039  // Actually perform the operation.
1040  // evalBinOpNN expects the two indexes to already be the right type.
1041  return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy);
1042  }
1043  }
1044 
1045  // Special handling of the FieldRegions, even with symbolic offsets.
1046  const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR);
1047  const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR);
1048  if (RightFR && LeftFR) {
1049  SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy,
1050  *this);
1051  if (!R.isUnknown())
1052  return R;
1053  }
1054 
1055  // Compare the regions using the raw offsets.
1056  RegionOffset LeftOffset = LeftMR->getAsOffset();
1057  RegionOffset RightOffset = RightMR->getAsOffset();
1058 
1059  if (LeftOffset.getRegion() != nullptr &&
1060  LeftOffset.getRegion() == RightOffset.getRegion() &&
1061  !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) {
1062  int64_t left = LeftOffset.getOffset();
1063  int64_t right = RightOffset.getOffset();
1064 
1065  switch (op) {
1066  default:
1067  return UnknownVal();
1068  case BO_LT:
1069  return makeTruthVal(left < right, resultTy);
1070  case BO_GT:
1071  return makeTruthVal(left > right, resultTy);
1072  case BO_LE:
1073  return makeTruthVal(left <= right, resultTy);
1074  case BO_GE:
1075  return makeTruthVal(left >= right, resultTy);
1076  case BO_EQ:
1077  return makeTruthVal(left == right, resultTy);
1078  case BO_NE:
1079  return makeTruthVal(left != right, resultTy);
1080  }
1081  }
1082 
1083  // At this point we're not going to get a good answer, but we can try
1084  // conjuring an expression instead.
1085  SymbolRef LHSSym = lhs.getAsLocSymbol();
1086  SymbolRef RHSSym = rhs.getAsLocSymbol();
1087  if (LHSSym && RHSSym)
1088  return makeNonLoc(LHSSym, op, RHSSym, resultTy);
1089 
1090  // If we get here, we have no way of comparing the regions.
1091  return UnknownVal();
1092  }
1093  }
1094 }
1095 
1096 SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,
1098  Loc lhs, NonLoc rhs, QualType resultTy) {
1099  if (op >= BO_PtrMemD && op <= BO_PtrMemI) {
1100  if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) {
1101  if (PTMSV->isNullMemberPointer())
1102  return UndefinedVal();
1103  if (const FieldDecl *FD = PTMSV->getDeclAs<FieldDecl>()) {
1104  SVal Result = lhs;
1105 
1106  for (const auto &I : *PTMSV)
1107  Result = StateMgr.getStoreManager().evalDerivedToBase(
1108  Result, I->getType(),I->isVirtual());
1109  return state->getLValue(FD, Result);
1110  }
1111  }
1112 
1113  return rhs;
1114  }
1115 
1116  assert(!BinaryOperator::isComparisonOp(op) &&
1117  "arguments to comparison ops must be of the same type");
1118 
1119  // Special case: rhs is a zero constant.
1120  if (rhs.isZeroConstant())
1121  return lhs;
1122 
1123  // Perserve the null pointer so that it can be found by the DerefChecker.
1124  if (lhs.isZeroConstant())
1125  return lhs;
1126 
1127  // We are dealing with pointer arithmetic.
1128 
1129  // Handle pointer arithmetic on constant values.
1130  if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) {
1131  if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) {
1132  const llvm::APSInt &leftI = lhsInt->getValue();
1133  assert(leftI.isUnsigned());
1134  llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true);
1135 
1136  // Convert the bitwidth of rightI. This should deal with overflow
1137  // since we are dealing with concrete values.
1138  rightI = rightI.extOrTrunc(leftI.getBitWidth());
1139 
1140  // Offset the increment by the pointer size.
1141  llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);
1142  QualType pointeeType = resultTy->getPointeeType();
1143  Multiplicand = getContext().getTypeSizeInChars(pointeeType).getQuantity();
1144  rightI *= Multiplicand;
1145 
1146  // Compute the adjusted pointer.
1147  switch (op) {
1148  case BO_Add:
1149  rightI = leftI + rightI;
1150  break;
1151  case BO_Sub:
1152  rightI = leftI - rightI;
1153  break;
1154  default:
1155  llvm_unreachable("Invalid pointer arithmetic operation");
1156  }
1157  return loc::ConcreteInt(getBasicValueFactory().getValue(rightI));
1158  }
1159  }
1160 
1161  // Handle cases where 'lhs' is a region.
1162  if (const MemRegion *region = lhs.getAsRegion()) {
1163  rhs = convertToArrayIndex(rhs).castAs<NonLoc>();
1164  SVal index = UnknownVal();
1165  const SubRegion *superR = nullptr;
1166  // We need to know the type of the pointer in order to add an integer to it.
1167  // Depending on the type, different amount of bytes is added.
1168  QualType elementType;
1169 
1170  if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) {
1171  assert(op == BO_Add || op == BO_Sub);
1172  index = evalBinOpNN(state, op, elemReg->getIndex(), rhs,
1173  getArrayIndexType());
1174  superR = cast<SubRegion>(elemReg->getSuperRegion());
1175  elementType = elemReg->getElementType();
1176  }
1177  else if (isa<SubRegion>(region)) {
1178  assert(op == BO_Add || op == BO_Sub);
1179  index = (op == BO_Add) ? rhs : evalMinus(rhs);
1180  superR = cast<SubRegion>(region);
1181  // TODO: Is this actually reliable? Maybe improving our MemRegion
1182  // hierarchy to provide typed regions for all non-void pointers would be
1183  // better. For instance, we cannot extend this towards LocAsInteger
1184  // operations, where result type of the expression is integer.
1185  if (resultTy->isAnyPointerType())
1186  elementType = resultTy->getPointeeType();
1187  }
1188 
1189  // Represent arithmetic on void pointers as arithmetic on char pointers.
1190  // It is fine when a TypedValueRegion of char value type represents
1191  // a void pointer. Note that arithmetic on void pointers is a GCC extension.
1192  if (elementType->isVoidType())
1193  elementType = getContext().CharTy;
1194 
1195  if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
1196  return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
1197  superR, getContext()));
1198  }
1199  }
1200  return UnknownVal();
1201 }
1202 
1203 const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state,
1204  SVal V) {
1205  V = simplifySVal(state, V);
1206  if (V.isUnknownOrUndef())
1207  return nullptr;
1208 
1209  if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>())
1210  return &X->getValue();
1211 
1212  if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>())
1213  return &X->getValue();
1214 
1215  if (SymbolRef Sym = V.getAsSymbol())
1216  return state->getConstraintManager().getSymVal(state, Sym);
1217 
1218  // FIXME: Add support for SymExprs.
1219  return nullptr;
1220 }
1221 
1222 SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) {
1223  // For now, this function tries to constant-fold symbols inside a
1224  // nonloc::SymbolVal, and does nothing else. More simplifications should
1225  // be possible, such as constant-folding an index in an ElementRegion.
1226 
1227  class Simplifier : public FullSValVisitor<Simplifier, SVal> {
1229  SValBuilder &SVB;
1230 
1231  // Cache results for the lifetime of the Simplifier. Results change every
1232  // time new constraints are added to the program state, which is the whole
1233  // point of simplifying, and for that very reason it's pointless to maintain
1234  // the same cache for the duration of the whole analysis.
1235  llvm::DenseMap<SymbolRef, SVal> Cached;
1236 
1237  static bool isUnchanged(SymbolRef Sym, SVal Val) {
1238  return Sym == Val.getAsSymbol();
1239  }
1240 
1241  SVal cache(SymbolRef Sym, SVal V) {
1242  Cached[Sym] = V;
1243  return V;
1244  }
1245 
1246  SVal skip(SymbolRef Sym) {
1247  return cache(Sym, SVB.makeSymbolVal(Sym));
1248  }
1249 
1250  public:
1251  Simplifier(ProgramStateRef State)
1252  : State(State), SVB(State->getStateManager().getSValBuilder()) {}
1253 
1254  SVal VisitSymbolData(const SymbolData *S) {
1255  // No cache here.
1256  if (const llvm::APSInt *I =
1257  SVB.getKnownValue(State, SVB.makeSymbolVal(S)))
1258  return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I)
1259  : (SVal)SVB.makeIntVal(*I);
1260  return SVB.makeSymbolVal(S);
1261  }
1262 
1263  // TODO: Support SymbolCast. Support IntSymExpr when/if we actually
1264  // start producing them.
1265 
1266  SVal VisitSymIntExpr(const SymIntExpr *S) {
1267  auto I = Cached.find(S);
1268  if (I != Cached.end())
1269  return I->second;
1270 
1271  SVal LHS = Visit(S->getLHS());
1272  if (isUnchanged(S->getLHS(), LHS))
1273  return skip(S);
1274 
1275  SVal RHS;
1276  // By looking at the APSInt in the right-hand side of S, we cannot
1277  // figure out if it should be treated as a Loc or as a NonLoc.
1278  // So make our guess by recalling that we cannot multiply pointers
1279  // or compare a pointer to an integer.
1280  if (Loc::isLocType(S->getLHS()->getType()) &&
1281  BinaryOperator::isComparisonOp(S->getOpcode())) {
1282  // The usual conversion of $sym to &SymRegion{$sym}, as they have
1283  // the same meaning for Loc-type symbols, but the latter form
1284  // is preferred in SVal computations for being Loc itself.
1285  if (SymbolRef Sym = LHS.getAsSymbol()) {
1286  assert(Loc::isLocType(Sym->getType()));
1287  LHS = SVB.makeLoc(Sym);
1288  }
1289  RHS = SVB.makeIntLocVal(S->getRHS());
1290  } else {
1291  RHS = SVB.makeIntVal(S->getRHS());
1292  }
1293 
1294  return cache(
1295  S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));
1296  }
1297 
1298  SVal VisitSymSymExpr(const SymSymExpr *S) {
1299  auto I = Cached.find(S);
1300  if (I != Cached.end())
1301  return I->second;
1302 
1303  // For now don't try to simplify mixed Loc/NonLoc expressions
1304  // because they often appear from LocAsInteger operations
1305  // and we don't know how to combine a LocAsInteger
1306  // with a concrete value.
1307  if (Loc::isLocType(S->getLHS()->getType()) !=
1308  Loc::isLocType(S->getRHS()->getType()))
1309  return skip(S);
1310 
1311  SVal LHS = Visit(S->getLHS());
1312  SVal RHS = Visit(S->getRHS());
1313  if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS))
1314  return skip(S);
1315 
1316  return cache(
1317  S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));
1318  }
1319 
1320  SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); }
1321 
1322  SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); }
1323 
1324  SVal VisitNonLocSymbolVal(nonloc::SymbolVal V) {
1325  // Simplification is much more costly than computing complexity.
1326  // For high complexity, it may be not worth it.
1327  return Visit(V.getSymbol());
1328  }
1329 
1330  SVal VisitSVal(SVal V) { return V; }
1331  };
1332 
1333  // A crude way of preventing this function from calling itself from evalBinOp.
1334  static bool isReentering = false;
1335  if (isReentering)
1336  return V;
1337 
1338  isReentering = true;
1339  SVal SimplifiedV = Simplifier(State).Visit(V);
1340  isReentering = false;
1341 
1342  return SimplifiedV;
1343 }
Represents a function declaration or definition.
Definition: Decl.h:1739
if(T->getSizeExpr()) TRY_TO(TraverseStmt(T -> getSizeExpr()))
CanQualType VoidPtrTy
Definition: ASTContext.h:1043
A (possibly-)qualified type.
Definition: Type.h:638
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:505
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:2772
Value representing integer constant.
Definition: SVals.h:377
bool isAdditiveOp() const
Definition: Expr.h:3325
Symbolic value.
Definition: SymExpr.h:30
Represents a struct/union/class.
Definition: Decl.h:3602
const SymbolicRegion * getSymbolicBase() const
If this is a symbolic region, returns the region.
Definition: MemRegion.cpp:1218
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:3354
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:3793
Represents a member of a struct/union/class.
Definition: Decl.h:2588
bool isReferenceType() const
Definition: Type.h:6312
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:6648
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:3341
unsigned getSubKind() const
Definition: SVals.h:120
SymbolicRegion - A special, "non-concrete" region.
Definition: MemRegion.h:763
static SVal getValue(SVal val, SValBuilder &svalBuilder)
bool isUnionType() const
Definition: Type.cpp:475
bool isNull() const
Return true if this QualType doesn&#39;t point to a type yet.
Definition: Type.h:703
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:3339
FunctionCodeRegion - A region that represents code texts of function.
Definition: MemRegion.h:580
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:1860
bool isAnyPointerType() const
Definition: Type.h:6304
Dataflow Directional Tag Classes.
bool isShiftOp() const
Definition: Expr.h:3327
bool isBooleanType() const
Definition: Type.h:6661
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:2069
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:2252
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:13961
bool isVoidType() const
Definition: Type.h:6548
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)