clang  5.0.0
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 
18 
19 using namespace clang;
20 using namespace ento;
21 
22 namespace {
23 class SimpleSValBuilder : public SValBuilder {
24 protected:
25  SVal dispatchCast(SVal val, QualType castTy) override;
26  SVal evalCastFromNonLoc(NonLoc val, QualType castTy) override;
27  SVal evalCastFromLoc(Loc val, QualType castTy) override;
28 
29 public:
30  SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context,
31  ProgramStateManager &stateMgr)
32  : SValBuilder(alloc, context, stateMgr) {}
33  ~SimpleSValBuilder() override {}
34 
35  SVal evalMinus(NonLoc val) override;
36  SVal evalComplement(NonLoc val) override;
38  NonLoc lhs, NonLoc rhs, QualType resultTy) override;
40  Loc lhs, Loc rhs, QualType resultTy) override;
42  Loc lhs, NonLoc rhs, QualType resultTy) override;
43 
44  /// getKnownValue - evaluates a given SVal. If the SVal has only one possible
45  /// (integer) value, that value is returned. Otherwise, returns NULL.
46  const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override;
47 
48  /// Recursively descends into symbolic expressions and replaces symbols
49  /// with their known values (in the sense of the getKnownValue() method).
50  SVal simplifySVal(ProgramStateRef State, SVal V) override;
51 
52  SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op,
53  const llvm::APSInt &RHS, QualType resultTy);
54 };
55 } // end anonymous namespace
56 
57 SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc,
58  ASTContext &context,
59  ProgramStateManager &stateMgr) {
60  return new SimpleSValBuilder(alloc, context, stateMgr);
61 }
62 
63 //===----------------------------------------------------------------------===//
64 // Transfer function for Casts.
65 //===----------------------------------------------------------------------===//
66 
67 SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) {
68  assert(Val.getAs<Loc>() || Val.getAs<NonLoc>());
69  return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy)
70  : evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy);
71 }
72 
73 SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) {
74  bool isLocType = Loc::isLocType(castTy);
75  if (val.getAs<nonloc::PointerToMember>())
76  return val;
77 
79  if (isLocType)
80  return LI->getLoc();
81  // FIXME: Correctly support promotions/truncations.
82  unsigned castSize = Context.getIntWidth(castTy);
83  if (castSize == LI->getNumBits())
84  return val;
85  return makeLocAsInteger(LI->getLoc(), castSize);
86  }
87 
88  if (const SymExpr *se = val.getAsSymbolicExpression()) {
89  QualType T = Context.getCanonicalType(se->getType());
90  // If types are the same or both are integers, ignore the cast.
91  // FIXME: Remove this hack when we support symbolic truncation/extension.
92  // HACK: If both castTy and T are integers, ignore the cast. This is
93  // not a permanent solution. Eventually we want to precisely handle
94  // extension/truncation of symbolic integers. This prevents us from losing
95  // precision when we assign 'x = y' and 'y' is symbolic and x and y are
96  // different integer types.
97  if (haveSameType(T, castTy))
98  return val;
99 
100  if (!isLocType)
101  return makeNonLoc(se, T, castTy);
102  return UnknownVal();
103  }
104 
105  // If value is a non-integer constant, produce unknown.
106  if (!val.getAs<nonloc::ConcreteInt>())
107  return UnknownVal();
108 
109  // Handle casts to a boolean type.
110  if (castTy->isBooleanType()) {
111  bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue();
112  return makeTruthVal(b, castTy);
113  }
114 
115  // Only handle casts from integers to integers - if val is an integer constant
116  // being cast to a non-integer type, produce unknown.
117  if (!isLocType && !castTy->isIntegralOrEnumerationType())
118  return UnknownVal();
119 
120  llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue();
121  BasicVals.getAPSIntType(castTy).apply(i);
122 
123  if (isLocType)
124  return makeIntLocVal(i);
125  else
126  return makeIntVal(i);
127 }
128 
129 SVal SimpleSValBuilder::evalCastFromLoc(Loc val, QualType castTy) {
130 
131  // Casts from pointers -> pointers, just return the lval.
132  //
133  // Casts from pointers -> references, just return the lval. These
134  // can be introduced by the frontend for corner cases, e.g
135  // casting from va_list* to __builtin_va_list&.
136  //
137  if (Loc::isLocType(castTy) || castTy->isReferenceType())
138  return val;
139 
140  // FIXME: Handle transparent unions where a value can be "transparently"
141  // lifted into a union type.
142  if (castTy->isUnionType())
143  return UnknownVal();
144 
145  // Casting a Loc to a bool will almost always be true,
146  // unless this is a weak function or a symbolic region.
147  if (castTy->isBooleanType()) {
148  switch (val.getSubKind()) {
149  case loc::MemRegionValKind: {
150  const MemRegion *R = val.castAs<loc::MemRegionVal>().getRegion();
151  if (const FunctionCodeRegion *FTR = dyn_cast<FunctionCodeRegion>(R))
152  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl()))
153  if (FD->isWeak())
154  // FIXME: Currently we are using an extent symbol here,
155  // because there are no generic region address metadata
156  // symbols to use, only content metadata.
157  return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR));
158 
159  if (const SymbolicRegion *SymR = R->getSymbolicBase())
160  return nonloc::SymbolVal(SymR->getSymbol());
161 
162  // FALL-THROUGH
163  LLVM_FALLTHROUGH;
164  }
165 
166  case loc::GotoLabelKind:
167  // Labels and non-symbolic memory regions are always true.
168  return makeTruthVal(true, castTy);
169  }
170  }
171 
172  if (castTy->isIntegralOrEnumerationType()) {
173  unsigned BitWidth = Context.getIntWidth(castTy);
174 
175  if (!val.getAs<loc::ConcreteInt>())
176  return makeLocAsInteger(val, BitWidth);
177 
178  llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue();
179  BasicVals.getAPSIntType(castTy).apply(i);
180  return makeIntVal(i);
181  }
182 
183  // All other cases: return 'UnknownVal'. This includes casting pointers
184  // to floats, which is probably badness it itself, but this is a good
185  // intermediate solution until we do something better.
186  return UnknownVal();
187 }
188 
189 //===----------------------------------------------------------------------===//
190 // Transfer function for unary operators.
191 //===----------------------------------------------------------------------===//
192 
193 SVal SimpleSValBuilder::evalMinus(NonLoc val) {
194  switch (val.getSubKind()) {
195  case nonloc::ConcreteIntKind:
196  return val.castAs<nonloc::ConcreteInt>().evalMinus(*this);
197  default:
198  return UnknownVal();
199  }
200 }
201 
202 SVal SimpleSValBuilder::evalComplement(NonLoc X) {
203  switch (X.getSubKind()) {
204  case nonloc::ConcreteIntKind:
205  return X.castAs<nonloc::ConcreteInt>().evalComplement(*this);
206  default:
207  return UnknownVal();
208  }
209 }
210 
211 //===----------------------------------------------------------------------===//
212 // Transfer function for binary operators.
213 //===----------------------------------------------------------------------===//
214 
215 SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,
217  const llvm::APSInt &RHS,
218  QualType resultTy) {
219  bool isIdempotent = false;
220 
221  // Check for a few special cases with known reductions first.
222  switch (op) {
223  default:
224  // We can't reduce this case; just treat it normally.
225  break;
226  case BO_Mul:
227  // a*0 and a*1
228  if (RHS == 0)
229  return makeIntVal(0, resultTy);
230  else if (RHS == 1)
231  isIdempotent = true;
232  break;
233  case BO_Div:
234  // a/0 and a/1
235  if (RHS == 0)
236  // This is also handled elsewhere.
237  return UndefinedVal();
238  else if (RHS == 1)
239  isIdempotent = true;
240  break;
241  case BO_Rem:
242  // a%0 and a%1
243  if (RHS == 0)
244  // This is also handled elsewhere.
245  return UndefinedVal();
246  else if (RHS == 1)
247  return makeIntVal(0, resultTy);
248  break;
249  case BO_Add:
250  case BO_Sub:
251  case BO_Shl:
252  case BO_Shr:
253  case BO_Xor:
254  // a+0, a-0, a<<0, a>>0, a^0
255  if (RHS == 0)
256  isIdempotent = true;
257  break;
258  case BO_And:
259  // a&0 and a&(~0)
260  if (RHS == 0)
261  return makeIntVal(0, resultTy);
262  else if (RHS.isAllOnesValue())
263  isIdempotent = true;
264  break;
265  case BO_Or:
266  // a|0 and a|(~0)
267  if (RHS == 0)
268  isIdempotent = true;
269  else if (RHS.isAllOnesValue()) {
270  const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS);
271  return nonloc::ConcreteInt(Result);
272  }
273  break;
274  }
275 
276  // Idempotent ops (like a*1) can still change the type of an expression.
277  // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the
278  // dirty work.
279  if (isIdempotent)
280  return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy);
281 
282  // If we reach this point, the expression cannot be simplified.
283  // Make a SymbolVal for the entire expression, after converting the RHS.
284  const llvm::APSInt *ConvertedRHS = &RHS;
286  // We're looking for a type big enough to compare the symbolic value
287  // with the given constant.
288  // FIXME: This is an approximation of Sema::UsualArithmeticConversions.
289  ASTContext &Ctx = getContext();
290  QualType SymbolType = LHS->getType();
291  uint64_t ValWidth = RHS.getBitWidth();
292  uint64_t TypeWidth = Ctx.getTypeSize(SymbolType);
293 
294  if (ValWidth < TypeWidth) {
295  // If the value is too small, extend it.
296  ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
297  } else if (ValWidth == TypeWidth) {
298  // If the value is signed but the symbol is unsigned, do the comparison
299  // in unsigned space. [C99 6.3.1.8]
300  // (For the opposite case, the value is already unsigned.)
301  if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType())
302  ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
303  }
304  } else
305  ConvertedRHS = &BasicVals.Convert(resultTy, RHS);
306 
307  return makeNonLoc(LHS, op, *ConvertedRHS, resultTy);
308 }
309 
310 SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
312  NonLoc lhs, NonLoc rhs,
313  QualType resultTy) {
314  NonLoc InputLHS = lhs;
315  NonLoc InputRHS = rhs;
316 
317  // Handle trivial case where left-side and right-side are the same.
318  if (lhs == rhs)
319  switch (op) {
320  default:
321  break;
322  case BO_EQ:
323  case BO_LE:
324  case BO_GE:
325  return makeTruthVal(true, resultTy);
326  case BO_LT:
327  case BO_GT:
328  case BO_NE:
329  return makeTruthVal(false, resultTy);
330  case BO_Xor:
331  case BO_Sub:
332  if (resultTy->isIntegralOrEnumerationType())
333  return makeIntVal(0, resultTy);
334  return evalCastFromNonLoc(makeIntVal(0, /*Unsigned=*/false), resultTy);
335  case BO_Or:
336  case BO_And:
337  return evalCastFromNonLoc(lhs, resultTy);
338  }
339 
340  while (1) {
341  switch (lhs.getSubKind()) {
342  default:
343  return makeSymExprValNN(state, op, lhs, rhs, resultTy);
344  case nonloc::PointerToMemberKind: {
345  assert(rhs.getSubKind() == nonloc::PointerToMemberKind &&
346  "Both SVals should have pointer-to-member-type");
347  auto LPTM = lhs.castAs<nonloc::PointerToMember>(),
348  RPTM = rhs.castAs<nonloc::PointerToMember>();
349  auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData();
350  switch (op) {
351  case BO_EQ:
352  return makeTruthVal(LPTMD == RPTMD, resultTy);
353  case BO_NE:
354  return makeTruthVal(LPTMD != RPTMD, resultTy);
355  default:
356  return UnknownVal();
357  }
358  }
359  case nonloc::LocAsIntegerKind: {
360  Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc();
361  switch (rhs.getSubKind()) {
362  case nonloc::LocAsIntegerKind:
363  return evalBinOpLL(state, op, lhsL,
365  resultTy);
366  case nonloc::ConcreteIntKind: {
367  // Transform the integer into a location and compare.
368  // FIXME: This only makes sense for comparisons. If we want to, say,
369  // add 1 to a LocAsInteger, we'd better unpack the Loc and add to it,
370  // then pack it back into a LocAsInteger.
371  llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue();
372  BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i);
373  return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy);
374  }
375  default:
376  switch (op) {
377  case BO_EQ:
378  return makeTruthVal(false, resultTy);
379  case BO_NE:
380  return makeTruthVal(true, resultTy);
381  default:
382  // This case also handles pointer arithmetic.
383  return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
384  }
385  }
386  }
387  case nonloc::ConcreteIntKind: {
388  llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue();
389 
390  // If we're dealing with two known constants, just perform the operation.
391  if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) {
392  llvm::APSInt RHSValue = *KnownRHSValue;
394  // We're looking for a type big enough to compare the two values.
395  // FIXME: This is not correct. char + short will result in a promotion
396  // to int. Unfortunately we have lost types by this point.
397  APSIntType CompareType = std::max(APSIntType(LHSValue),
398  APSIntType(RHSValue));
399  CompareType.apply(LHSValue);
400  CompareType.apply(RHSValue);
401  } else if (!BinaryOperator::isShiftOp(op)) {
402  APSIntType IntType = BasicVals.getAPSIntType(resultTy);
403  IntType.apply(LHSValue);
404  IntType.apply(RHSValue);
405  }
406 
407  const llvm::APSInt *Result =
408  BasicVals.evalAPSInt(op, LHSValue, RHSValue);
409  if (!Result)
410  return UndefinedVal();
411 
412  return nonloc::ConcreteInt(*Result);
413  }
414 
415  // Swap the left and right sides and flip the operator if doing so
416  // allows us to better reason about the expression (this is a form
417  // of expression canonicalization).
418  // While we're at it, catch some special cases for non-commutative ops.
419  switch (op) {
420  case BO_LT:
421  case BO_GT:
422  case BO_LE:
423  case BO_GE:
425  // FALL-THROUGH
426  case BO_EQ:
427  case BO_NE:
428  case BO_Add:
429  case BO_Mul:
430  case BO_And:
431  case BO_Xor:
432  case BO_Or:
433  std::swap(lhs, rhs);
434  continue;
435  case BO_Shr:
436  // (~0)>>a
437  if (LHSValue.isAllOnesValue() && LHSValue.isSigned())
438  return evalCastFromNonLoc(lhs, resultTy);
439  // FALL-THROUGH
440  case BO_Shl:
441  // 0<<a and 0>>a
442  if (LHSValue == 0)
443  return evalCastFromNonLoc(lhs, resultTy);
444  return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
445  default:
446  return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
447  }
448  }
449  case nonloc::SymbolValKind: {
450  // We only handle LHS as simple symbols or SymIntExprs.
451  SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol();
452 
453  // LHS is a symbolic expression.
454  if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) {
455 
456  // Is this a logical not? (!x is represented as x == 0.)
457  if (op == BO_EQ && rhs.isZeroConstant()) {
458  // We know how to negate certain expressions. Simplify them here.
459 
460  BinaryOperator::Opcode opc = symIntExpr->getOpcode();
461  switch (opc) {
462  default:
463  // We don't know how to negate this operation.
464  // Just handle it as if it were a normal comparison to 0.
465  break;
466  case BO_LAnd:
467  case BO_LOr:
468  llvm_unreachable("Logical operators handled by branching logic.");
469  case BO_Assign:
470  case BO_MulAssign:
471  case BO_DivAssign:
472  case BO_RemAssign:
473  case BO_AddAssign:
474  case BO_SubAssign:
475  case BO_ShlAssign:
476  case BO_ShrAssign:
477  case BO_AndAssign:
478  case BO_XorAssign:
479  case BO_OrAssign:
480  case BO_Comma:
481  llvm_unreachable("'=' and ',' operators handled by ExprEngine.");
482  case BO_PtrMemD:
483  case BO_PtrMemI:
484  llvm_unreachable("Pointer arithmetic not handled here.");
485  case BO_LT:
486  case BO_GT:
487  case BO_LE:
488  case BO_GE:
489  case BO_EQ:
490  case BO_NE:
491  assert(resultTy->isBooleanType() ||
492  resultTy == getConditionType());
493  assert(symIntExpr->getType()->isBooleanType() ||
494  getContext().hasSameUnqualifiedType(symIntExpr->getType(),
495  getConditionType()));
496  // Negate the comparison and make a value.
498  return makeNonLoc(symIntExpr->getLHS(), opc,
499  symIntExpr->getRHS(), resultTy);
500  }
501  }
502 
503  // For now, only handle expressions whose RHS is a constant.
504  if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) {
505  // If both the LHS and the current expression are additive,
506  // fold their constants and try again.
508  BinaryOperator::Opcode lop = symIntExpr->getOpcode();
509  if (BinaryOperator::isAdditiveOp(lop)) {
510  // Convert the two constants to a common type, then combine them.
511 
512  // resultTy may not be the best type to convert to, but it's
513  // probably the best choice in expressions with mixed type
514  // (such as x+1U+2LL). The rules for implicit conversions should
515  // choose a reasonable type to preserve the expression, and will
516  // at least match how the value is going to be used.
517  APSIntType IntType = BasicVals.getAPSIntType(resultTy);
518  const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());
519  const llvm::APSInt &second = IntType.convert(*RHSValue);
520 
521  const llvm::APSInt *newRHS;
522  if (lop == op)
523  newRHS = BasicVals.evalAPSInt(BO_Add, first, second);
524  else
525  newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);
526 
527  assert(newRHS && "Invalid operation despite common type!");
528  rhs = nonloc::ConcreteInt(*newRHS);
529  lhs = nonloc::SymbolVal(symIntExpr->getLHS());
530  op = lop;
531  continue;
532  }
533  }
534 
535  // Otherwise, make a SymIntExpr out of the expression.
536  return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy);
537  }
538  }
539 
540  // Does the symbolic expression simplify to a constant?
541  // If so, "fold" the constant by setting 'lhs' to a ConcreteInt
542  // and try again.
543  SVal simplifiedLhs = simplifySVal(state, lhs);
544  if (simplifiedLhs != lhs)
545  if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) {
546  lhs = *simplifiedLhsAsNonLoc;
547  continue;
548  }
549 
550  // Is the RHS a constant?
551  if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs))
552  return MakeSymIntVal(Sym, op, *RHSValue, resultTy);
553 
554  // Give up -- this is not a symbolic expression we can handle.
555  return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
556  }
557  }
558  }
559 }
560 
562  const FieldRegion *RightFR,
564  QualType resultTy,
565  SimpleSValBuilder &SVB) {
566  // Only comparisons are meaningful here!
568  return UnknownVal();
569 
570  // Next, see if the two FRs have the same super-region.
571  // FIXME: This doesn't handle casts yet, and simply stripping the casts
572  // doesn't help.
573  if (LeftFR->getSuperRegion() != RightFR->getSuperRegion())
574  return UnknownVal();
575 
576  const FieldDecl *LeftFD = LeftFR->getDecl();
577  const FieldDecl *RightFD = RightFR->getDecl();
578  const RecordDecl *RD = LeftFD->getParent();
579 
580  // Make sure the two FRs are from the same kind of record. Just in case!
581  // FIXME: This is probably where inheritance would be a problem.
582  if (RD != RightFD->getParent())
583  return UnknownVal();
584 
585  // We know for sure that the two fields are not the same, since that
586  // would have given us the same SVal.
587  if (op == BO_EQ)
588  return SVB.makeTruthVal(false, resultTy);
589  if (op == BO_NE)
590  return SVB.makeTruthVal(true, resultTy);
591 
592  // Iterate through the fields and see which one comes first.
593  // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field
594  // members and the units in which bit-fields reside have addresses that
595  // increase in the order in which they are declared."
596  bool leftFirst = (op == BO_LT || op == BO_LE);
597  for (const auto *I : RD->fields()) {
598  if (I == LeftFD)
599  return SVB.makeTruthVal(leftFirst, resultTy);
600  if (I == RightFD)
601  return SVB.makeTruthVal(!leftFirst, resultTy);
602  }
603 
604  llvm_unreachable("Fields not found in parent record's definition");
605 }
606 
607 // FIXME: all this logic will change if/when we have MemRegion::getLocation().
608 SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state,
610  Loc lhs, Loc rhs,
611  QualType resultTy) {
612  // Only comparisons and subtractions are valid operations on two pointers.
613  // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15].
614  // However, if a pointer is casted to an integer, evalBinOpNN may end up
615  // calling this function with another operation (PR7527). We don't attempt to
616  // model this for now, but it could be useful, particularly when the
617  // "location" is actually an integer value that's been passed through a void*.
618  if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub))
619  return UnknownVal();
620 
621  // Special cases for when both sides are identical.
622  if (lhs == rhs) {
623  switch (op) {
624  default:
625  llvm_unreachable("Unimplemented operation for two identical values");
626  case BO_Sub:
627  return makeZeroVal(resultTy);
628  case BO_EQ:
629  case BO_LE:
630  case BO_GE:
631  return makeTruthVal(true, resultTy);
632  case BO_NE:
633  case BO_LT:
634  case BO_GT:
635  return makeTruthVal(false, resultTy);
636  }
637  }
638 
639  switch (lhs.getSubKind()) {
640  default:
641  llvm_unreachable("Ordering not implemented for this Loc.");
642 
643  case loc::GotoLabelKind:
644  // The only thing we know about labels is that they're non-null.
645  if (rhs.isZeroConstant()) {
646  switch (op) {
647  default:
648  break;
649  case BO_Sub:
650  return evalCastFromLoc(lhs, resultTy);
651  case BO_EQ:
652  case BO_LE:
653  case BO_LT:
654  return makeTruthVal(false, resultTy);
655  case BO_NE:
656  case BO_GT:
657  case BO_GE:
658  return makeTruthVal(true, resultTy);
659  }
660  }
661  // There may be two labels for the same location, and a function region may
662  // have the same address as a label at the start of the function (depending
663  // on the ABI).
664  // FIXME: we can probably do a comparison against other MemRegions, though.
665  // FIXME: is there a way to tell if two labels refer to the same location?
666  return UnknownVal();
667 
668  case loc::ConcreteIntKind: {
669  // If one of the operands is a symbol and the other is a constant,
670  // build an expression for use by the constraint manager.
671  if (SymbolRef rSym = rhs.getAsLocSymbol()) {
672  // We can only build expressions with symbols on the left,
673  // so we need a reversible operator.
675  return UnknownVal();
676 
677  const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue();
679  return makeNonLoc(rSym, op, lVal, resultTy);
680  }
681 
682  // If both operands are constants, just perform the operation.
684  SVal ResultVal =
685  lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt);
686  if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>())
687  return evalCastFromNonLoc(*Result, resultTy);
688 
689  assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs");
690  return UnknownVal();
691  }
692 
693  // Special case comparisons against NULL.
694  // This must come after the test if the RHS is a symbol, which is used to
695  // build constraints. The address of any non-symbolic region is guaranteed
696  // to be non-NULL, as is any label.
697  assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>());
698  if (lhs.isZeroConstant()) {
699  switch (op) {
700  default:
701  break;
702  case BO_EQ:
703  case BO_GT:
704  case BO_GE:
705  return makeTruthVal(false, resultTy);
706  case BO_NE:
707  case BO_LT:
708  case BO_LE:
709  return makeTruthVal(true, resultTy);
710  }
711  }
712 
713  // Comparing an arbitrary integer to a region or label address is
714  // completely unknowable.
715  return UnknownVal();
716  }
717  case loc::MemRegionValKind: {
719  // If one of the operands is a symbol and the other is a constant,
720  // build an expression for use by the constraint manager.
721  if (SymbolRef lSym = lhs.getAsLocSymbol(true))
722  return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy);
723 
724  // Special case comparisons to NULL.
725  // This must come after the test if the LHS is a symbol, which is used to
726  // build constraints. The address of any non-symbolic region is guaranteed
727  // to be non-NULL.
728  if (rInt->isZeroConstant()) {
729  if (op == BO_Sub)
730  return evalCastFromLoc(lhs, resultTy);
731 
733  QualType boolType = getContext().BoolTy;
734  NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>();
735  NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>();
736  return evalBinOpNN(state, op, l, r, resultTy);
737  }
738  }
739 
740  // Comparing a region to an arbitrary integer is completely unknowable.
741  return UnknownVal();
742  }
743 
744  // Get both values as regions, if possible.
745  const MemRegion *LeftMR = lhs.getAsRegion();
746  assert(LeftMR && "MemRegionValKind SVal doesn't have a region!");
747 
748  const MemRegion *RightMR = rhs.getAsRegion();
749  if (!RightMR)
750  // The RHS is probably a label, which in theory could address a region.
751  // FIXME: we can probably make a more useful statement about non-code
752  // regions, though.
753  return UnknownVal();
754 
755  const MemRegion *LeftBase = LeftMR->getBaseRegion();
756  const MemRegion *RightBase = RightMR->getBaseRegion();
757  const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace();
758  const MemSpaceRegion *RightMS = RightBase->getMemorySpace();
759  const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion();
760 
761  // If the two regions are from different known memory spaces they cannot be
762  // equal. Also, assume that no symbolic region (whose memory space is
763  // unknown) is on the stack.
764  if (LeftMS != RightMS &&
765  ((LeftMS != UnknownMS && RightMS != UnknownMS) ||
766  (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) {
767  switch (op) {
768  default:
769  return UnknownVal();
770  case BO_EQ:
771  return makeTruthVal(false, resultTy);
772  case BO_NE:
773  return makeTruthVal(true, resultTy);
774  }
775  }
776 
777  // If both values wrap regions, see if they're from different base regions.
778  // Note, heap base symbolic regions are assumed to not alias with
779  // each other; for example, we assume that malloc returns different address
780  // on each invocation.
781  // FIXME: ObjC object pointers always reside on the heap, but currently
782  // we treat their memory space as unknown, because symbolic pointers
783  // to ObjC objects may alias. There should be a way to construct
784  // possibly-aliasing heap-based regions. For instance, MacOSXApiChecker
785  // guesses memory space for ObjC object pointers manually instead of
786  // relying on us.
787  if (LeftBase != RightBase &&
788  ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) ||
789  (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){
790  switch (op) {
791  default:
792  return UnknownVal();
793  case BO_EQ:
794  return makeTruthVal(false, resultTy);
795  case BO_NE:
796  return makeTruthVal(true, resultTy);
797  }
798  }
799 
800  // Handle special cases for when both regions are element regions.
801  const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR);
802  const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR);
803  if (RightER && LeftER) {
804  // Next, see if the two ERs have the same super-region and matching types.
805  // FIXME: This should do something useful even if the types don't match,
806  // though if both indexes are constant the RegionRawOffset path will
807  // give the correct answer.
808  if (LeftER->getSuperRegion() == RightER->getSuperRegion() &&
809  LeftER->getElementType() == RightER->getElementType()) {
810  // Get the left index and cast it to the correct type.
811  // If the index is unknown or undefined, bail out here.
812  SVal LeftIndexVal = LeftER->getIndex();
813  Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>();
814  if (!LeftIndex)
815  return UnknownVal();
816  LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy);
817  LeftIndex = LeftIndexVal.getAs<NonLoc>();
818  if (!LeftIndex)
819  return UnknownVal();
820 
821  // Do the same for the right index.
822  SVal RightIndexVal = RightER->getIndex();
823  Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>();
824  if (!RightIndex)
825  return UnknownVal();
826  RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy);
827  RightIndex = RightIndexVal.getAs<NonLoc>();
828  if (!RightIndex)
829  return UnknownVal();
830 
831  // Actually perform the operation.
832  // evalBinOpNN expects the two indexes to already be the right type.
833  return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy);
834  }
835  }
836 
837  // Special handling of the FieldRegions, even with symbolic offsets.
838  const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR);
839  const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR);
840  if (RightFR && LeftFR) {
841  SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy,
842  *this);
843  if (!R.isUnknown())
844  return R;
845  }
846 
847  // Compare the regions using the raw offsets.
848  RegionOffset LeftOffset = LeftMR->getAsOffset();
849  RegionOffset RightOffset = RightMR->getAsOffset();
850 
851  if (LeftOffset.getRegion() != nullptr &&
852  LeftOffset.getRegion() == RightOffset.getRegion() &&
853  !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) {
854  int64_t left = LeftOffset.getOffset();
855  int64_t right = RightOffset.getOffset();
856 
857  switch (op) {
858  default:
859  return UnknownVal();
860  case BO_LT:
861  return makeTruthVal(left < right, resultTy);
862  case BO_GT:
863  return makeTruthVal(left > right, resultTy);
864  case BO_LE:
865  return makeTruthVal(left <= right, resultTy);
866  case BO_GE:
867  return makeTruthVal(left >= right, resultTy);
868  case BO_EQ:
869  return makeTruthVal(left == right, resultTy);
870  case BO_NE:
871  return makeTruthVal(left != right, resultTy);
872  }
873  }
874 
875  // At this point we're not going to get a good answer, but we can try
876  // conjuring an expression instead.
877  SymbolRef LHSSym = lhs.getAsLocSymbol();
878  SymbolRef RHSSym = rhs.getAsLocSymbol();
879  if (LHSSym && RHSSym)
880  return makeNonLoc(LHSSym, op, RHSSym, resultTy);
881 
882  // If we get here, we have no way of comparing the regions.
883  return UnknownVal();
884  }
885  }
886 }
887 
888 SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,
890  Loc lhs, NonLoc rhs, QualType resultTy) {
891  if (op >= BO_PtrMemD && op <= BO_PtrMemI) {
892  if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) {
893  if (PTMSV->isNullMemberPointer())
894  return UndefinedVal();
895  if (const FieldDecl *FD = PTMSV->getDeclAs<FieldDecl>()) {
896  SVal Result = lhs;
897 
898  for (const auto &I : *PTMSV)
899  Result = StateMgr.getStoreManager().evalDerivedToBase(
900  Result, I->getType(),I->isVirtual());
901  return state->getLValue(FD, Result);
902  }
903  }
904 
905  return rhs;
906  }
907 
908  assert(!BinaryOperator::isComparisonOp(op) &&
909  "arguments to comparison ops must be of the same type");
910 
911  // Special case: rhs is a zero constant.
912  if (rhs.isZeroConstant())
913  return lhs;
914 
915  // We are dealing with pointer arithmetic.
916 
917  // Handle pointer arithmetic on constant values.
919  if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) {
920  const llvm::APSInt &leftI = lhsInt->getValue();
921  assert(leftI.isUnsigned());
922  llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true);
923 
924  // Convert the bitwidth of rightI. This should deal with overflow
925  // since we are dealing with concrete values.
926  rightI = rightI.extOrTrunc(leftI.getBitWidth());
927 
928  // Offset the increment by the pointer size.
929  llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);
930  rightI *= Multiplicand;
931 
932  // Compute the adjusted pointer.
933  switch (op) {
934  case BO_Add:
935  rightI = leftI + rightI;
936  break;
937  case BO_Sub:
938  rightI = leftI - rightI;
939  break;
940  default:
941  llvm_unreachable("Invalid pointer arithmetic operation");
942  }
943  return loc::ConcreteInt(getBasicValueFactory().getValue(rightI));
944  }
945  }
946 
947  // Handle cases where 'lhs' is a region.
948  if (const MemRegion *region = lhs.getAsRegion()) {
949  rhs = convertToArrayIndex(rhs).castAs<NonLoc>();
950  SVal index = UnknownVal();
951  const SubRegion *superR = nullptr;
952  // We need to know the type of the pointer in order to add an integer to it.
953  // Depending on the type, different amount of bytes is added.
954  QualType elementType;
955 
956  if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) {
957  assert(op == BO_Add || op == BO_Sub);
958  index = evalBinOpNN(state, op, elemReg->getIndex(), rhs,
959  getArrayIndexType());
960  superR = cast<SubRegion>(elemReg->getSuperRegion());
961  elementType = elemReg->getElementType();
962  }
963  else if (isa<SubRegion>(region)) {
964  assert(op == BO_Add || op == BO_Sub);
965  index = (op == BO_Add) ? rhs : evalMinus(rhs);
966  superR = cast<SubRegion>(region);
967  // TODO: Is this actually reliable? Maybe improving our MemRegion
968  // hierarchy to provide typed regions for all non-void pointers would be
969  // better. For instance, we cannot extend this towards LocAsInteger
970  // operations, where result type of the expression is integer.
971  if (resultTy->isAnyPointerType())
972  elementType = resultTy->getPointeeType();
973  }
974 
975  if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
976  return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
977  superR, getContext()));
978  }
979  }
980  return UnknownVal();
981 }
982 
983 const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state,
984  SVal V) {
985  if (V.isUnknownOrUndef())
986  return nullptr;
987 
989  return &X->getValue();
990 
992  return &X->getValue();
993 
994  if (SymbolRef Sym = V.getAsSymbol())
995  return state->getConstraintManager().getSymVal(state, Sym);
996 
997  // FIXME: Add support for SymExprs.
998  return nullptr;
999 }
1000 
1001 SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) {
1002  // For now, this function tries to constant-fold symbols inside a
1003  // nonloc::SymbolVal, and does nothing else. More simplifications should
1004  // be possible, such as constant-folding an index in an ElementRegion.
1005 
1006  class Simplifier : public FullSValVisitor<Simplifier, SVal> {
1008  SValBuilder &SVB;
1009 
1010  public:
1011  Simplifier(ProgramStateRef State)
1012  : State(State), SVB(State->getStateManager().getSValBuilder()) {}
1013 
1014  SVal VisitSymbolData(const SymbolData *S) {
1015  if (const llvm::APSInt *I =
1016  SVB.getKnownValue(State, nonloc::SymbolVal(S)))
1017  return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I)
1018  : (SVal)SVB.makeIntVal(*I);
1019  return nonloc::SymbolVal(S);
1020  }
1021 
1022  // TODO: Support SymbolCast. Support IntSymExpr when/if we actually
1023  // start producing them.
1024 
1025  SVal VisitSymIntExpr(const SymIntExpr *S) {
1026  SVal LHS = Visit(S->getLHS());
1027  SVal RHS;
1028  // By looking at the APSInt in the right-hand side of S, we cannot
1029  // figure out if it should be treated as a Loc or as a NonLoc.
1030  // So make our guess by recalling that we cannot multiply pointers
1031  // or compare a pointer to an integer.
1032  if (Loc::isLocType(S->getLHS()->getType()) &&
1034  // The usual conversion of $sym to &SymRegion{$sym}, as they have
1035  // the same meaning for Loc-type symbols, but the latter form
1036  // is preferred in SVal computations for being Loc itself.
1037  if (SymbolRef Sym = LHS.getAsSymbol()) {
1038  assert(Loc::isLocType(Sym->getType()));
1039  LHS = SVB.makeLoc(Sym);
1040  }
1041  RHS = SVB.makeIntLocVal(S->getRHS());
1042  } else {
1043  RHS = SVB.makeIntVal(S->getRHS());
1044  }
1045  return SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
1046  }
1047 
1048  SVal VisitSymSymExpr(const SymSymExpr *S) {
1049  SVal LHS = Visit(S->getLHS());
1050  SVal RHS = Visit(S->getRHS());
1051  return SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
1052  }
1053 
1054  SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); }
1055 
1056  SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); }
1057 
1058  SVal VisitNonLocSymbolVal(nonloc::SymbolVal V) {
1059  // Simplification is much more costly than computing complexity.
1060  // For high complexity, it may be not worth it.
1061  if (V.getSymbol()->computeComplexity() > 100)
1062  return V;
1063  return Visit(V.getSymbol());
1064  }
1065 
1066  SVal VisitSVal(SVal V) { return V; }
1067  };
1068 
1069  return Simplifier(State).Visit(V);
1070 }
FunctionDecl - An instance of this class is created to represent a function declaration or definition...
Definition: Decl.h:1618
CanQualType VoidPtrTy
Definition: ASTContext.h:978
A (possibly-)qualified type.
Definition: Type.h:616
MemRegion - The root abstract class for all memory regions.
Definition: MemRegion.h:79
const llvm::APSInt & getRHS() const
const SymExpr * getLHS() const
SValBuilder * createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context, ProgramStateManager &stateMgr)
unsigned getIntWidth(QualType T) const
bool isBooleanType() const
Definition: Type.h:5969
MemSpaceRegion - A memory region that represents a "memory space"; for example, the set of global var...
Definition: MemRegion.h:179
Value representing integer constant.
Definition: SVals.h:352
const SymExpr * getRHS() const
uint64_t getTypeSize(QualType T) const
Return the size of the specified (complete) type T, in bits.
Definition: ASTContext.h:1924
QualType getElementType() const
Definition: MemRegion.h:1091
const MemRegion * getBaseRegion() const
Definition: MemRegion.cpp:1091
bool isZeroConstant() const
Definition: SVals.cpp:219
bool isUnionType() const
Definition: Type.cpp:390
Symbolic value.
Definition: SymExpr.h:29
RecordDecl - Represents a struct/union/class.
Definition: Decl.h:3354
bool isComparisonOp() const
Definition: Expr.h:3058
const MemSpaceRegion * getMemorySpace() const
Definition: MemRegion.cpp:1059
static Opcode reverseComparisonOp(Opcode Opc)
Definition: Expr.h:3073
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:128
Value representing pointer-to-member.
Definition: SVals.h:486
LineState State
unsigned computeComplexity() const
bool isReferenceType() const
Definition: Type.h:5721
FieldDecl - An instance of this class is created by Sema::ActOnField to represent a member of a struc...
Definition: Decl.h:2366
bool isAnyPointerType() const
Definition: Type.h:5715
SymbolRef getAsLocSymbol(bool IncludeBaseRegions=false) const
If this SVal is a location and wraps a symbol, return that SymbolRef.
Definition: SVals.cpp:74
FullSValVisitor - a convenient mixed visitor for all three: SVal, SymExpr and MemRegion subclasses...
Definition: SValVisitor.h:138
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 * getLHS() const
static bool isLocType(QualType T)
Definition: SVals.h:307
BinaryOperatorKind
const SymbolicRegion * getSymbolicBase() const
If this is a symbolic region, returns the region.
Definition: MemRegion.cpp:1139
field_range fields() const
Definition: Decl.h:3483
bool isUnknownOrUndef() const
Definition: SVals.h:136
A record of the "type" of an APSInt, used for conversions.
Definition: APSIntType.h:20
Represents a symbolic expression like 'x' + 3.
detail::InMemoryDirectory::const_iterator I
Represent a region's offset within the top level base region.
Definition: MemRegion.h:47
virtual QualType getType() const =0
const MemRegion * getSuperRegion() const
Definition: MemRegion.h:430
static Opcode negateComparisonOp(Opcode Opc)
Definition: Expr.h:3060
ASTContext * Context
QualType getPointeeType() const
If this is a pointer, ObjC object pointer, or block pointer, this returns the respective pointee...
Definition: Type.cpp:414
SymbolicRegion - A special, "non-concrete" region.
Definition: MemRegion.h:742
bool isSignedIntegerOrEnumerationType() const
Determines whether this is an integer type that is signed or an enumeration types whose underlying ty...
Definition: Type.cpp:1760
bool hasSymbolicOffset() const
Definition: MemRegion.h:64
Optional< T > getAs() const
Convert to the specified SVal type, returning None if this SVal is not of the desired type...
Definition: SVals.h:100
static SVal getValue(SVal val, SValBuilder &svalBuilder)
bool isIntegralOrEnumerationType() const
Determine whether this type is an integral or enumeration type.
Definition: Type.h:5956
FunctionCodeRegion - A region that represents code texts of function.
Definition: MemRegion.h:563
const FieldDecl * getDecl() const
Definition: MemRegion.h:999
SVal - This represents a symbolic expression, which can be either an L-value or an R-value...
Definition: SVals.h:63
SymbolRef getSymbol() const
Definition: SVals.h:331
QualType getType() const override
NonLoc getIndex() const
Definition: MemRegion.h:1085
const PTMDataType getPTMData() const
Definition: SVals.h:492
bool isAdditiveOp() const
Definition: Expr.h:3044
RegionOffset getAsOffset() const
Compute the offset within the top level memory object.
Definition: MemRegion.cpp:1208
llvm::APSInt convert(const llvm::APSInt &Value) const LLVM_READONLY
Convert and return a new APSInt with the given value, but this type's bit width and signedness...
Definition: APSIntType.h:49
unsigned getSubKind() const
Definition: SVals.h:111
bool isShiftOp() const
Definition: Expr.h:3046
void apply(llvm::APSInt &Value) const
Convert a given APSInt, in place, to match this type.
Definition: APSIntType.h:38
Represents symbolic expression.
Definition: SVals.h:326
const MemRegion * getAsRegion() const
Definition: SVals.cpp:140
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:2087
SubRegion - A region that subsets another larger region.
Definition: MemRegion.h:419
bool isUnknown() const
Definition: SVals.h:128
int64_t getOffset() const
Definition: MemRegion.h:66
BinaryOperator::Opcode getOpcode() const
char __ovld __cnfn max(char x, char y)
Returns y if x < y, otherwise it returns x.
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:13074
SymbolRef getAsSymbol(bool IncludeBaseRegions=false) const
If this SVal wraps a symbol return that SymbolRef.
Definition: SVals.cpp:116
ElementRegin is used to represent both array elements and casts.
Definition: MemRegion.h:1066
const MemRegion * getRegion() const
Definition: MemRegion.h:62
const SymExpr * getAsSymbolicExpression() const
getAsSymbolicExpression - If this Sval wraps a symbolic expression then return that expression...
Definition: SVals.cpp:126
T castAs() const
Convert to the specified SVal type, asserting that this SVal is of the desired type.
Definition: SVals.h:92
Represents a symbolic expression like 'x' + 'y'.
const NamedDecl * Result
Definition: USRFinder.cpp:70
A symbol representing data which can be stored in a memory location (region).
Definition: SymExpr.h:107
const RecordDecl * getParent() const
getParent - Returns the parent of this field declaration, which is the struct in which this field is ...
Definition: Decl.h:2528
static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR, const FieldRegion *RightFR, BinaryOperator::Opcode op, QualType resultTy, SimpleSValBuilder &SVB)