1 // SimpleSValBuilder.cpp - A basic SValBuilder -----------------------*- C++ -*- 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines SimpleSValBuilder, a basic implementation of SValBuilder. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" 14 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" 15 #include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h" 16 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 17 #include "clang/StaticAnalyzer/Core/PathSensitive/SubEngine.h" 18 #include "clang/StaticAnalyzer/Core/PathSensitive/SValVisitor.h" 19 20 using namespace clang; 21 using namespace ento; 22 23 namespace { 24 class SimpleSValBuilder : public SValBuilder { 25 protected: 26 SVal dispatchCast(SVal val, QualType castTy) override; 27 SVal evalCastFromNonLoc(NonLoc val, QualType castTy) override; 28 SVal evalCastFromLoc(Loc val, QualType castTy) override; 29 30 public: 31 SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context, 32 ProgramStateManager &stateMgr) 33 : SValBuilder(alloc, context, stateMgr) {} 34 ~SimpleSValBuilder() override {} 35 36 SVal evalMinus(NonLoc val) override; 37 SVal evalComplement(NonLoc val) override; 38 SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op, 39 NonLoc lhs, NonLoc rhs, QualType resultTy) override; 40 SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op, 41 Loc lhs, Loc rhs, QualType resultTy) override; 42 SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op, 43 Loc lhs, NonLoc rhs, QualType resultTy) override; 44 45 /// getKnownValue - evaluates a given SVal. If the SVal has only one possible 46 /// (integer) value, that value is returned. Otherwise, returns NULL. 47 const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override; 48 49 /// Recursively descends into symbolic expressions and replaces symbols 50 /// with their known values (in the sense of the getKnownValue() method). 51 SVal simplifySVal(ProgramStateRef State, SVal V) override; 52 53 SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op, 54 const llvm::APSInt &RHS, QualType resultTy); 55 }; 56 } // end anonymous namespace 57 58 SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc, 59 ASTContext &context, 60 ProgramStateManager &stateMgr) { 61 return new SimpleSValBuilder(alloc, context, stateMgr); 62 } 63 64 //===----------------------------------------------------------------------===// 65 // Transfer function for Casts. 66 //===----------------------------------------------------------------------===// 67 68 SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) { 69 assert(Val.getAs<Loc>() || Val.getAs<NonLoc>()); 70 return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy) 71 : evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy); 72 } 73 74 SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) { 75 bool isLocType = Loc::isLocType(castTy); 76 if (val.getAs<nonloc::PointerToMember>()) 77 return val; 78 79 if (Optional<nonloc::LocAsInteger> LI = val.getAs<nonloc::LocAsInteger>()) { 80 if (isLocType) 81 return LI->getLoc(); 82 // FIXME: Correctly support promotions/truncations. 83 unsigned castSize = Context.getIntWidth(castTy); 84 if (castSize == LI->getNumBits()) 85 return val; 86 return makeLocAsInteger(LI->getLoc(), castSize); 87 } 88 89 if (const SymExpr *se = val.getAsSymbolicExpression()) { 90 QualType T = Context.getCanonicalType(se->getType()); 91 // If types are the same or both are integers, ignore the cast. 92 // FIXME: Remove this hack when we support symbolic truncation/extension. 93 // HACK: If both castTy and T are integers, ignore the cast. This is 94 // not a permanent solution. Eventually we want to precisely handle 95 // extension/truncation of symbolic integers. This prevents us from losing 96 // precision when we assign 'x = y' and 'y' is symbolic and x and y are 97 // different integer types. 98 if (haveSameType(T, castTy)) 99 return val; 100 101 if (!isLocType) 102 return makeNonLoc(se, T, castTy); 103 return UnknownVal(); 104 } 105 106 // If value is a non-integer constant, produce unknown. 107 if (!val.getAs<nonloc::ConcreteInt>()) 108 return UnknownVal(); 109 110 // Handle casts to a boolean type. 111 if (castTy->isBooleanType()) { 112 bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue(); 113 return makeTruthVal(b, castTy); 114 } 115 116 // Only handle casts from integers to integers - if val is an integer constant 117 // being cast to a non-integer type, produce unknown. 118 if (!isLocType && !castTy->isIntegralOrEnumerationType()) 119 return UnknownVal(); 120 121 llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue(); 122 BasicVals.getAPSIntType(castTy).apply(i); 123 124 if (isLocType) 125 return makeIntLocVal(i); 126 else 127 return makeIntVal(i); 128 } 129 130 SVal SimpleSValBuilder::evalCastFromLoc(Loc val, QualType castTy) { 131 132 // Casts from pointers -> pointers, just return the lval. 133 // 134 // Casts from pointers -> references, just return the lval. These 135 // can be introduced by the frontend for corner cases, e.g 136 // casting from va_list* to __builtin_va_list&. 137 // 138 if (Loc::isLocType(castTy) || castTy->isReferenceType()) 139 return val; 140 141 // FIXME: Handle transparent unions where a value can be "transparently" 142 // lifted into a union type. 143 if (castTy->isUnionType()) 144 return UnknownVal(); 145 146 // Casting a Loc to a bool will almost always be true, 147 // unless this is a weak function or a symbolic region. 148 if (castTy->isBooleanType()) { 149 switch (val.getSubKind()) { 150 case loc::MemRegionValKind: { 151 const MemRegion *R = val.castAs<loc::MemRegionVal>().getRegion(); 152 if (const FunctionCodeRegion *FTR = dyn_cast<FunctionCodeRegion>(R)) 153 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl())) 154 if (FD->isWeak()) 155 // FIXME: Currently we are using an extent symbol here, 156 // because there are no generic region address metadata 157 // symbols to use, only content metadata. 158 return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR)); 159 160 if (const SymbolicRegion *SymR = R->getSymbolicBase()) 161 return makeNonLoc(SymR->getSymbol(), BO_NE, 162 BasicVals.getZeroWithPtrWidth(), castTy); 163 164 // FALL-THROUGH 165 LLVM_FALLTHROUGH; 166 } 167 168 case loc::GotoLabelKind: 169 // Labels and non-symbolic memory regions are always true. 170 return makeTruthVal(true, castTy); 171 } 172 } 173 174 if (castTy->isIntegralOrEnumerationType()) { 175 unsigned BitWidth = Context.getIntWidth(castTy); 176 177 if (!val.getAs<loc::ConcreteInt>()) 178 return makeLocAsInteger(val, BitWidth); 179 180 llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue(); 181 BasicVals.getAPSIntType(castTy).apply(i); 182 return makeIntVal(i); 183 } 184 185 // All other cases: return 'UnknownVal'. This includes casting pointers 186 // to floats, which is probably badness it itself, but this is a good 187 // intermediate solution until we do something better. 188 return UnknownVal(); 189 } 190 191 //===----------------------------------------------------------------------===// 192 // Transfer function for unary operators. 193 //===----------------------------------------------------------------------===// 194 195 SVal SimpleSValBuilder::evalMinus(NonLoc val) { 196 switch (val.getSubKind()) { 197 case nonloc::ConcreteIntKind: 198 return val.castAs<nonloc::ConcreteInt>().evalMinus(*this); 199 default: 200 return UnknownVal(); 201 } 202 } 203 204 SVal SimpleSValBuilder::evalComplement(NonLoc X) { 205 switch (X.getSubKind()) { 206 case nonloc::ConcreteIntKind: 207 return X.castAs<nonloc::ConcreteInt>().evalComplement(*this); 208 default: 209 return UnknownVal(); 210 } 211 } 212 213 //===----------------------------------------------------------------------===// 214 // Transfer function for binary operators. 215 //===----------------------------------------------------------------------===// 216 217 SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS, 218 BinaryOperator::Opcode op, 219 const llvm::APSInt &RHS, 220 QualType resultTy) { 221 bool isIdempotent = false; 222 223 // Check for a few special cases with known reductions first. 224 switch (op) { 225 default: 226 // We can't reduce this case; just treat it normally. 227 break; 228 case BO_Mul: 229 // a*0 and a*1 230 if (RHS == 0) 231 return makeIntVal(0, resultTy); 232 else if (RHS == 1) 233 isIdempotent = true; 234 break; 235 case BO_Div: 236 // a/0 and a/1 237 if (RHS == 0) 238 // This is also handled elsewhere. 239 return UndefinedVal(); 240 else if (RHS == 1) 241 isIdempotent = true; 242 break; 243 case BO_Rem: 244 // a%0 and a%1 245 if (RHS == 0) 246 // This is also handled elsewhere. 247 return UndefinedVal(); 248 else if (RHS == 1) 249 return makeIntVal(0, resultTy); 250 break; 251 case BO_Add: 252 case BO_Sub: 253 case BO_Shl: 254 case BO_Shr: 255 case BO_Xor: 256 // a+0, a-0, a<<0, a>>0, a^0 257 if (RHS == 0) 258 isIdempotent = true; 259 break; 260 case BO_And: 261 // a&0 and a&(~0) 262 if (RHS == 0) 263 return makeIntVal(0, resultTy); 264 else if (RHS.isAllOnesValue()) 265 isIdempotent = true; 266 break; 267 case BO_Or: 268 // a|0 and a|(~0) 269 if (RHS == 0) 270 isIdempotent = true; 271 else if (RHS.isAllOnesValue()) { 272 const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS); 273 return nonloc::ConcreteInt(Result); 274 } 275 break; 276 } 277 278 // Idempotent ops (like a*1) can still change the type of an expression. 279 // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the 280 // dirty work. 281 if (isIdempotent) 282 return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy); 283 284 // If we reach this point, the expression cannot be simplified. 285 // Make a SymbolVal for the entire expression, after converting the RHS. 286 const llvm::APSInt *ConvertedRHS = &RHS; 287 if (BinaryOperator::isComparisonOp(op)) { 288 // We're looking for a type big enough to compare the symbolic value 289 // with the given constant. 290 // FIXME: This is an approximation of Sema::UsualArithmeticConversions. 291 ASTContext &Ctx = getContext(); 292 QualType SymbolType = LHS->getType(); 293 uint64_t ValWidth = RHS.getBitWidth(); 294 uint64_t TypeWidth = Ctx.getTypeSize(SymbolType); 295 296 if (ValWidth < TypeWidth) { 297 // If the value is too small, extend it. 298 ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); 299 } else if (ValWidth == TypeWidth) { 300 // If the value is signed but the symbol is unsigned, do the comparison 301 // in unsigned space. [C99 6.3.1.8] 302 // (For the opposite case, the value is already unsigned.) 303 if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType()) 304 ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); 305 } 306 } else 307 ConvertedRHS = &BasicVals.Convert(resultTy, RHS); 308 309 return makeNonLoc(LHS, op, *ConvertedRHS, resultTy); 310 } 311 312 // See if Sym is known to be a relation Rel with Bound. 313 static bool isInRelation(BinaryOperator::Opcode Rel, SymbolRef Sym, 314 llvm::APSInt Bound, ProgramStateRef State) { 315 SValBuilder &SVB = State->getStateManager().getSValBuilder(); 316 SVal Result = 317 SVB.evalBinOpNN(State, Rel, nonloc::SymbolVal(Sym), 318 nonloc::ConcreteInt(Bound), SVB.getConditionType()); 319 if (auto DV = Result.getAs<DefinedSVal>()) { 320 return !State->assume(*DV, false); 321 } 322 return false; 323 } 324 325 // See if Sym is known to be within [min/4, max/4], where min and max 326 // are the bounds of the symbol's integral type. With such symbols, 327 // some manipulations can be performed without the risk of overflow. 328 // assume() doesn't cause infinite recursion because we should be dealing 329 // with simpler symbols on every recursive call. 330 static bool isWithinConstantOverflowBounds(SymbolRef Sym, 331 ProgramStateRef State) { 332 SValBuilder &SVB = State->getStateManager().getSValBuilder(); 333 BasicValueFactory &BV = SVB.getBasicValueFactory(); 334 335 QualType T = Sym->getType(); 336 assert(T->isSignedIntegerOrEnumerationType() && 337 "This only works with signed integers!"); 338 APSIntType AT = BV.getAPSIntType(T); 339 340 llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max; 341 return isInRelation(BO_LE, Sym, Max, State) && 342 isInRelation(BO_GE, Sym, Min, State); 343 } 344 345 // Same for the concrete integers: see if I is within [min/4, max/4]. 346 static bool isWithinConstantOverflowBounds(llvm::APSInt I) { 347 APSIntType AT(I); 348 assert(!AT.isUnsigned() && 349 "This only works with signed integers!"); 350 351 llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max; 352 return (I <= Max) && (I >= -Max); 353 } 354 355 static std::pair<SymbolRef, llvm::APSInt> 356 decomposeSymbol(SymbolRef Sym, BasicValueFactory &BV) { 357 if (const auto *SymInt = dyn_cast<SymIntExpr>(Sym)) 358 if (BinaryOperator::isAdditiveOp(SymInt->getOpcode())) 359 return std::make_pair(SymInt->getLHS(), 360 (SymInt->getOpcode() == BO_Add) ? 361 (SymInt->getRHS()) : 362 (-SymInt->getRHS())); 363 364 // Fail to decompose: "reduce" the problem to the "$x + 0" case. 365 return std::make_pair(Sym, BV.getValue(0, Sym->getType())); 366 } 367 368 // Simplify "(LSym + LInt) Op (RSym + RInt)" assuming all values are of the 369 // same signed integral type and no overflows occur (which should be checked 370 // by the caller). 371 static NonLoc doRearrangeUnchecked(ProgramStateRef State, 372 BinaryOperator::Opcode Op, 373 SymbolRef LSym, llvm::APSInt LInt, 374 SymbolRef RSym, llvm::APSInt RInt) { 375 SValBuilder &SVB = State->getStateManager().getSValBuilder(); 376 BasicValueFactory &BV = SVB.getBasicValueFactory(); 377 SymbolManager &SymMgr = SVB.getSymbolManager(); 378 379 QualType SymTy = LSym->getType(); 380 assert(SymTy == RSym->getType() && 381 "Symbols are not of the same type!"); 382 assert(APSIntType(LInt) == BV.getAPSIntType(SymTy) && 383 "Integers are not of the same type as symbols!"); 384 assert(APSIntType(RInt) == BV.getAPSIntType(SymTy) && 385 "Integers are not of the same type as symbols!"); 386 387 QualType ResultTy; 388 if (BinaryOperator::isComparisonOp(Op)) 389 ResultTy = SVB.getConditionType(); 390 else if (BinaryOperator::isAdditiveOp(Op)) 391 ResultTy = SymTy; 392 else 393 llvm_unreachable("Operation not suitable for unchecked rearrangement!"); 394 395 // FIXME: Can we use assume() without getting into an infinite recursion? 396 if (LSym == RSym) 397 return SVB.evalBinOpNN(State, Op, nonloc::ConcreteInt(LInt), 398 nonloc::ConcreteInt(RInt), ResultTy) 399 .castAs<NonLoc>(); 400 401 SymbolRef ResultSym = nullptr; 402 BinaryOperator::Opcode ResultOp; 403 llvm::APSInt ResultInt; 404 if (BinaryOperator::isComparisonOp(Op)) { 405 // Prefer comparing to a non-negative number. 406 // FIXME: Maybe it'd be better to have consistency in 407 // "$x - $y" vs. "$y - $x" because those are solver's keys. 408 if (LInt > RInt) { 409 ResultSym = SymMgr.getSymSymExpr(RSym, BO_Sub, LSym, SymTy); 410 ResultOp = BinaryOperator::reverseComparisonOp(Op); 411 ResultInt = LInt - RInt; // Opposite order! 412 } else { 413 ResultSym = SymMgr.getSymSymExpr(LSym, BO_Sub, RSym, SymTy); 414 ResultOp = Op; 415 ResultInt = RInt - LInt; // Opposite order! 416 } 417 } else { 418 ResultSym = SymMgr.getSymSymExpr(LSym, Op, RSym, SymTy); 419 ResultInt = (Op == BO_Add) ? (LInt + RInt) : (LInt - RInt); 420 ResultOp = BO_Add; 421 // Bring back the cosmetic difference. 422 if (ResultInt < 0) { 423 ResultInt = -ResultInt; 424 ResultOp = BO_Sub; 425 } else if (ResultInt == 0) { 426 // Shortcut: Simplify "$x + 0" to "$x". 427 return nonloc::SymbolVal(ResultSym); 428 } 429 } 430 const llvm::APSInt &PersistentResultInt = BV.getValue(ResultInt); 431 return nonloc::SymbolVal( 432 SymMgr.getSymIntExpr(ResultSym, ResultOp, PersistentResultInt, ResultTy)); 433 } 434 435 // Rearrange if symbol type matches the result type and if the operator is a 436 // comparison operator, both symbol and constant must be within constant 437 // overflow bounds. 438 static bool shouldRearrange(ProgramStateRef State, BinaryOperator::Opcode Op, 439 SymbolRef Sym, llvm::APSInt Int, QualType Ty) { 440 return Sym->getType() == Ty && 441 (!BinaryOperator::isComparisonOp(Op) || 442 (isWithinConstantOverflowBounds(Sym, State) && 443 isWithinConstantOverflowBounds(Int))); 444 } 445 446 static Optional<NonLoc> tryRearrange(ProgramStateRef State, 447 BinaryOperator::Opcode Op, NonLoc Lhs, 448 NonLoc Rhs, QualType ResultTy) { 449 ProgramStateManager &StateMgr = State->getStateManager(); 450 SValBuilder &SVB = StateMgr.getSValBuilder(); 451 452 // We expect everything to be of the same type - this type. 453 QualType SingleTy; 454 455 auto &Opts = 456 StateMgr.getOwningEngine().getAnalysisManager().getAnalyzerOptions(); 457 458 // FIXME: After putting complexity threshold to the symbols we can always 459 // rearrange additive operations but rearrange comparisons only if 460 // option is set. 461 if(!Opts.ShouldAggressivelySimplifyBinaryOperation) 462 return None; 463 464 SymbolRef LSym = Lhs.getAsSymbol(); 465 if (!LSym) 466 return None; 467 468 if (BinaryOperator::isComparisonOp(Op)) { 469 SingleTy = LSym->getType(); 470 if (ResultTy != SVB.getConditionType()) 471 return None; 472 // Initialize SingleTy later with a symbol's type. 473 } else if (BinaryOperator::isAdditiveOp(Op)) { 474 SingleTy = ResultTy; 475 if (LSym->getType() != SingleTy) 476 return None; 477 } else { 478 // Don't rearrange other operations. 479 return None; 480 } 481 482 assert(!SingleTy.isNull() && "We should have figured out the type by now!"); 483 484 // Rearrange signed symbolic expressions only 485 if (!SingleTy->isSignedIntegerOrEnumerationType()) 486 return None; 487 488 SymbolRef RSym = Rhs.getAsSymbol(); 489 if (!RSym || RSym->getType() != SingleTy) 490 return None; 491 492 BasicValueFactory &BV = State->getBasicVals(); 493 llvm::APSInt LInt, RInt; 494 std::tie(LSym, LInt) = decomposeSymbol(LSym, BV); 495 std::tie(RSym, RInt) = decomposeSymbol(RSym, BV); 496 if (!shouldRearrange(State, Op, LSym, LInt, SingleTy) || 497 !shouldRearrange(State, Op, RSym, RInt, SingleTy)) 498 return None; 499 500 // We know that no overflows can occur anymore. 501 return doRearrangeUnchecked(State, Op, LSym, LInt, RSym, RInt); 502 } 503 504 SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state, 505 BinaryOperator::Opcode op, 506 NonLoc lhs, NonLoc rhs, 507 QualType resultTy) { 508 NonLoc InputLHS = lhs; 509 NonLoc InputRHS = rhs; 510 511 // Handle trivial case where left-side and right-side are the same. 512 if (lhs == rhs) 513 switch (op) { 514 default: 515 break; 516 case BO_EQ: 517 case BO_LE: 518 case BO_GE: 519 return makeTruthVal(true, resultTy); 520 case BO_LT: 521 case BO_GT: 522 case BO_NE: 523 return makeTruthVal(false, resultTy); 524 case BO_Xor: 525 case BO_Sub: 526 if (resultTy->isIntegralOrEnumerationType()) 527 return makeIntVal(0, resultTy); 528 return evalCastFromNonLoc(makeIntVal(0, /*isUnsigned=*/false), resultTy); 529 case BO_Or: 530 case BO_And: 531 return evalCastFromNonLoc(lhs, resultTy); 532 } 533 534 while (1) { 535 switch (lhs.getSubKind()) { 536 default: 537 return makeSymExprValNN(op, lhs, rhs, resultTy); 538 case nonloc::PointerToMemberKind: { 539 assert(rhs.getSubKind() == nonloc::PointerToMemberKind && 540 "Both SVals should have pointer-to-member-type"); 541 auto LPTM = lhs.castAs<nonloc::PointerToMember>(), 542 RPTM = rhs.castAs<nonloc::PointerToMember>(); 543 auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData(); 544 switch (op) { 545 case BO_EQ: 546 return makeTruthVal(LPTMD == RPTMD, resultTy); 547 case BO_NE: 548 return makeTruthVal(LPTMD != RPTMD, resultTy); 549 default: 550 return UnknownVal(); 551 } 552 } 553 case nonloc::LocAsIntegerKind: { 554 Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc(); 555 switch (rhs.getSubKind()) { 556 case nonloc::LocAsIntegerKind: 557 // FIXME: at the moment the implementation 558 // of modeling "pointers as integers" is not complete. 559 if (!BinaryOperator::isComparisonOp(op)) 560 return UnknownVal(); 561 return evalBinOpLL(state, op, lhsL, 562 rhs.castAs<nonloc::LocAsInteger>().getLoc(), 563 resultTy); 564 case nonloc::ConcreteIntKind: { 565 // FIXME: at the moment the implementation 566 // of modeling "pointers as integers" is not complete. 567 if (!BinaryOperator::isComparisonOp(op)) 568 return UnknownVal(); 569 // Transform the integer into a location and compare. 570 // FIXME: This only makes sense for comparisons. If we want to, say, 571 // add 1 to a LocAsInteger, we'd better unpack the Loc and add to it, 572 // then pack it back into a LocAsInteger. 573 llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue(); 574 // If the region has a symbolic base, pay attention to the type; it 575 // might be coming from a non-default address space. For non-symbolic 576 // regions it doesn't matter that much because such comparisons would 577 // most likely evaluate to concrete false anyway. FIXME: We might 578 // still need to handle the non-comparison case. 579 if (SymbolRef lSym = lhs.getAsLocSymbol(true)) 580 BasicVals.getAPSIntType(lSym->getType()).apply(i); 581 else 582 BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i); 583 return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy); 584 } 585 default: 586 switch (op) { 587 case BO_EQ: 588 return makeTruthVal(false, resultTy); 589 case BO_NE: 590 return makeTruthVal(true, resultTy); 591 default: 592 // This case also handles pointer arithmetic. 593 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); 594 } 595 } 596 } 597 case nonloc::ConcreteIntKind: { 598 llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue(); 599 600 // If we're dealing with two known constants, just perform the operation. 601 if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) { 602 llvm::APSInt RHSValue = *KnownRHSValue; 603 if (BinaryOperator::isComparisonOp(op)) { 604 // We're looking for a type big enough to compare the two values. 605 // FIXME: This is not correct. char + short will result in a promotion 606 // to int. Unfortunately we have lost types by this point. 607 APSIntType CompareType = std::max(APSIntType(LHSValue), 608 APSIntType(RHSValue)); 609 CompareType.apply(LHSValue); 610 CompareType.apply(RHSValue); 611 } else if (!BinaryOperator::isShiftOp(op)) { 612 APSIntType IntType = BasicVals.getAPSIntType(resultTy); 613 IntType.apply(LHSValue); 614 IntType.apply(RHSValue); 615 } 616 617 const llvm::APSInt *Result = 618 BasicVals.evalAPSInt(op, LHSValue, RHSValue); 619 if (!Result) 620 return UndefinedVal(); 621 622 return nonloc::ConcreteInt(*Result); 623 } 624 625 // Swap the left and right sides and flip the operator if doing so 626 // allows us to better reason about the expression (this is a form 627 // of expression canonicalization). 628 // While we're at it, catch some special cases for non-commutative ops. 629 switch (op) { 630 case BO_LT: 631 case BO_GT: 632 case BO_LE: 633 case BO_GE: 634 op = BinaryOperator::reverseComparisonOp(op); 635 LLVM_FALLTHROUGH; 636 case BO_EQ: 637 case BO_NE: 638 case BO_Add: 639 case BO_Mul: 640 case BO_And: 641 case BO_Xor: 642 case BO_Or: 643 std::swap(lhs, rhs); 644 continue; 645 case BO_Shr: 646 // (~0)>>a 647 if (LHSValue.isAllOnesValue() && LHSValue.isSigned()) 648 return evalCastFromNonLoc(lhs, resultTy); 649 LLVM_FALLTHROUGH; 650 case BO_Shl: 651 // 0<<a and 0>>a 652 if (LHSValue == 0) 653 return evalCastFromNonLoc(lhs, resultTy); 654 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); 655 default: 656 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); 657 } 658 } 659 case nonloc::SymbolValKind: { 660 // We only handle LHS as simple symbols or SymIntExprs. 661 SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol(); 662 663 // LHS is a symbolic expression. 664 if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) { 665 666 // Is this a logical not? (!x is represented as x == 0.) 667 if (op == BO_EQ && rhs.isZeroConstant()) { 668 // We know how to negate certain expressions. Simplify them here. 669 670 BinaryOperator::Opcode opc = symIntExpr->getOpcode(); 671 switch (opc) { 672 default: 673 // We don't know how to negate this operation. 674 // Just handle it as if it were a normal comparison to 0. 675 break; 676 case BO_LAnd: 677 case BO_LOr: 678 llvm_unreachable("Logical operators handled by branching logic."); 679 case BO_Assign: 680 case BO_MulAssign: 681 case BO_DivAssign: 682 case BO_RemAssign: 683 case BO_AddAssign: 684 case BO_SubAssign: 685 case BO_ShlAssign: 686 case BO_ShrAssign: 687 case BO_AndAssign: 688 case BO_XorAssign: 689 case BO_OrAssign: 690 case BO_Comma: 691 llvm_unreachable("'=' and ',' operators handled by ExprEngine."); 692 case BO_PtrMemD: 693 case BO_PtrMemI: 694 llvm_unreachable("Pointer arithmetic not handled here."); 695 case BO_LT: 696 case BO_GT: 697 case BO_LE: 698 case BO_GE: 699 case BO_EQ: 700 case BO_NE: 701 assert(resultTy->isBooleanType() || 702 resultTy == getConditionType()); 703 assert(symIntExpr->getType()->isBooleanType() || 704 getContext().hasSameUnqualifiedType(symIntExpr->getType(), 705 getConditionType())); 706 // Negate the comparison and make a value. 707 opc = BinaryOperator::negateComparisonOp(opc); 708 return makeNonLoc(symIntExpr->getLHS(), opc, 709 symIntExpr->getRHS(), resultTy); 710 } 711 } 712 713 // For now, only handle expressions whose RHS is a constant. 714 if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) { 715 // If both the LHS and the current expression are additive, 716 // fold their constants and try again. 717 if (BinaryOperator::isAdditiveOp(op)) { 718 BinaryOperator::Opcode lop = symIntExpr->getOpcode(); 719 if (BinaryOperator::isAdditiveOp(lop)) { 720 // Convert the two constants to a common type, then combine them. 721 722 // resultTy may not be the best type to convert to, but it's 723 // probably the best choice in expressions with mixed type 724 // (such as x+1U+2LL). The rules for implicit conversions should 725 // choose a reasonable type to preserve the expression, and will 726 // at least match how the value is going to be used. 727 APSIntType IntType = BasicVals.getAPSIntType(resultTy); 728 const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS()); 729 const llvm::APSInt &second = IntType.convert(*RHSValue); 730 731 const llvm::APSInt *newRHS; 732 if (lop == op) 733 newRHS = BasicVals.evalAPSInt(BO_Add, first, second); 734 else 735 newRHS = BasicVals.evalAPSInt(BO_Sub, first, second); 736 737 assert(newRHS && "Invalid operation despite common type!"); 738 rhs = nonloc::ConcreteInt(*newRHS); 739 lhs = nonloc::SymbolVal(symIntExpr->getLHS()); 740 op = lop; 741 continue; 742 } 743 } 744 745 // Otherwise, make a SymIntExpr out of the expression. 746 return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy); 747 } 748 } 749 750 // Does the symbolic expression simplify to a constant? 751 // If so, "fold" the constant by setting 'lhs' to a ConcreteInt 752 // and try again. 753 SVal simplifiedLhs = simplifySVal(state, lhs); 754 if (simplifiedLhs != lhs) 755 if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) { 756 lhs = *simplifiedLhsAsNonLoc; 757 continue; 758 } 759 760 // Is the RHS a constant? 761 if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) 762 return MakeSymIntVal(Sym, op, *RHSValue, resultTy); 763 764 if (Optional<NonLoc> V = tryRearrange(state, op, lhs, rhs, resultTy)) 765 return *V; 766 767 // Give up -- this is not a symbolic expression we can handle. 768 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy); 769 } 770 } 771 } 772 } 773 774 static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR, 775 const FieldRegion *RightFR, 776 BinaryOperator::Opcode op, 777 QualType resultTy, 778 SimpleSValBuilder &SVB) { 779 // Only comparisons are meaningful here! 780 if (!BinaryOperator::isComparisonOp(op)) 781 return UnknownVal(); 782 783 // Next, see if the two FRs have the same super-region. 784 // FIXME: This doesn't handle casts yet, and simply stripping the casts 785 // doesn't help. 786 if (LeftFR->getSuperRegion() != RightFR->getSuperRegion()) 787 return UnknownVal(); 788 789 const FieldDecl *LeftFD = LeftFR->getDecl(); 790 const FieldDecl *RightFD = RightFR->getDecl(); 791 const RecordDecl *RD = LeftFD->getParent(); 792 793 // Make sure the two FRs are from the same kind of record. Just in case! 794 // FIXME: This is probably where inheritance would be a problem. 795 if (RD != RightFD->getParent()) 796 return UnknownVal(); 797 798 // We know for sure that the two fields are not the same, since that 799 // would have given us the same SVal. 800 if (op == BO_EQ) 801 return SVB.makeTruthVal(false, resultTy); 802 if (op == BO_NE) 803 return SVB.makeTruthVal(true, resultTy); 804 805 // Iterate through the fields and see which one comes first. 806 // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field 807 // members and the units in which bit-fields reside have addresses that 808 // increase in the order in which they are declared." 809 bool leftFirst = (op == BO_LT || op == BO_LE); 810 for (const auto *I : RD->fields()) { 811 if (I == LeftFD) 812 return SVB.makeTruthVal(leftFirst, resultTy); 813 if (I == RightFD) 814 return SVB.makeTruthVal(!leftFirst, resultTy); 815 } 816 817 llvm_unreachable("Fields not found in parent record's definition"); 818 } 819 820 // FIXME: all this logic will change if/when we have MemRegion::getLocation(). 821 SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state, 822 BinaryOperator::Opcode op, 823 Loc lhs, Loc rhs, 824 QualType resultTy) { 825 // Only comparisons and subtractions are valid operations on two pointers. 826 // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15]. 827 // However, if a pointer is casted to an integer, evalBinOpNN may end up 828 // calling this function with another operation (PR7527). We don't attempt to 829 // model this for now, but it could be useful, particularly when the 830 // "location" is actually an integer value that's been passed through a void*. 831 if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub)) 832 return UnknownVal(); 833 834 // Special cases for when both sides are identical. 835 if (lhs == rhs) { 836 switch (op) { 837 default: 838 llvm_unreachable("Unimplemented operation for two identical values"); 839 case BO_Sub: 840 return makeZeroVal(resultTy); 841 case BO_EQ: 842 case BO_LE: 843 case BO_GE: 844 return makeTruthVal(true, resultTy); 845 case BO_NE: 846 case BO_LT: 847 case BO_GT: 848 return makeTruthVal(false, resultTy); 849 } 850 } 851 852 switch (lhs.getSubKind()) { 853 default: 854 llvm_unreachable("Ordering not implemented for this Loc."); 855 856 case loc::GotoLabelKind: 857 // The only thing we know about labels is that they're non-null. 858 if (rhs.isZeroConstant()) { 859 switch (op) { 860 default: 861 break; 862 case BO_Sub: 863 return evalCastFromLoc(lhs, resultTy); 864 case BO_EQ: 865 case BO_LE: 866 case BO_LT: 867 return makeTruthVal(false, resultTy); 868 case BO_NE: 869 case BO_GT: 870 case BO_GE: 871 return makeTruthVal(true, resultTy); 872 } 873 } 874 // There may be two labels for the same location, and a function region may 875 // have the same address as a label at the start of the function (depending 876 // on the ABI). 877 // FIXME: we can probably do a comparison against other MemRegions, though. 878 // FIXME: is there a way to tell if two labels refer to the same location? 879 return UnknownVal(); 880 881 case loc::ConcreteIntKind: { 882 // If one of the operands is a symbol and the other is a constant, 883 // build an expression for use by the constraint manager. 884 if (SymbolRef rSym = rhs.getAsLocSymbol()) { 885 // We can only build expressions with symbols on the left, 886 // so we need a reversible operator. 887 if (!BinaryOperator::isComparisonOp(op) || op == BO_Cmp) 888 return UnknownVal(); 889 890 const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue(); 891 op = BinaryOperator::reverseComparisonOp(op); 892 return makeNonLoc(rSym, op, lVal, resultTy); 893 } 894 895 // If both operands are constants, just perform the operation. 896 if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) { 897 SVal ResultVal = 898 lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt); 899 if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>()) 900 return evalCastFromNonLoc(*Result, resultTy); 901 902 assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs"); 903 return UnknownVal(); 904 } 905 906 // Special case comparisons against NULL. 907 // This must come after the test if the RHS is a symbol, which is used to 908 // build constraints. The address of any non-symbolic region is guaranteed 909 // to be non-NULL, as is any label. 910 assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>()); 911 if (lhs.isZeroConstant()) { 912 switch (op) { 913 default: 914 break; 915 case BO_EQ: 916 case BO_GT: 917 case BO_GE: 918 return makeTruthVal(false, resultTy); 919 case BO_NE: 920 case BO_LT: 921 case BO_LE: 922 return makeTruthVal(true, resultTy); 923 } 924 } 925 926 // Comparing an arbitrary integer to a region or label address is 927 // completely unknowable. 928 return UnknownVal(); 929 } 930 case loc::MemRegionValKind: { 931 if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) { 932 // If one of the operands is a symbol and the other is a constant, 933 // build an expression for use by the constraint manager. 934 if (SymbolRef lSym = lhs.getAsLocSymbol(true)) { 935 if (BinaryOperator::isComparisonOp(op)) 936 return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy); 937 return UnknownVal(); 938 } 939 // Special case comparisons to NULL. 940 // This must come after the test if the LHS is a symbol, which is used to 941 // build constraints. The address of any non-symbolic region is guaranteed 942 // to be non-NULL. 943 if (rInt->isZeroConstant()) { 944 if (op == BO_Sub) 945 return evalCastFromLoc(lhs, resultTy); 946 947 if (BinaryOperator::isComparisonOp(op)) { 948 QualType boolType = getContext().BoolTy; 949 NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>(); 950 NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>(); 951 return evalBinOpNN(state, op, l, r, resultTy); 952 } 953 } 954 955 // Comparing a region to an arbitrary integer is completely unknowable. 956 return UnknownVal(); 957 } 958 959 // Get both values as regions, if possible. 960 const MemRegion *LeftMR = lhs.getAsRegion(); 961 assert(LeftMR && "MemRegionValKind SVal doesn't have a region!"); 962 963 const MemRegion *RightMR = rhs.getAsRegion(); 964 if (!RightMR) 965 // The RHS is probably a label, which in theory could address a region. 966 // FIXME: we can probably make a more useful statement about non-code 967 // regions, though. 968 return UnknownVal(); 969 970 const MemRegion *LeftBase = LeftMR->getBaseRegion(); 971 const MemRegion *RightBase = RightMR->getBaseRegion(); 972 const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace(); 973 const MemSpaceRegion *RightMS = RightBase->getMemorySpace(); 974 const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion(); 975 976 // If the two regions are from different known memory spaces they cannot be 977 // equal. Also, assume that no symbolic region (whose memory space is 978 // unknown) is on the stack. 979 if (LeftMS != RightMS && 980 ((LeftMS != UnknownMS && RightMS != UnknownMS) || 981 (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) { 982 switch (op) { 983 default: 984 return UnknownVal(); 985 case BO_EQ: 986 return makeTruthVal(false, resultTy); 987 case BO_NE: 988 return makeTruthVal(true, resultTy); 989 } 990 } 991 992 // If both values wrap regions, see if they're from different base regions. 993 // Note, heap base symbolic regions are assumed to not alias with 994 // each other; for example, we assume that malloc returns different address 995 // on each invocation. 996 // FIXME: ObjC object pointers always reside on the heap, but currently 997 // we treat their memory space as unknown, because symbolic pointers 998 // to ObjC objects may alias. There should be a way to construct 999 // possibly-aliasing heap-based regions. For instance, MacOSXApiChecker 1000 // guesses memory space for ObjC object pointers manually instead of 1001 // relying on us. 1002 if (LeftBase != RightBase && 1003 ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) || 1004 (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){ 1005 switch (op) { 1006 default: 1007 return UnknownVal(); 1008 case BO_EQ: 1009 return makeTruthVal(false, resultTy); 1010 case BO_NE: 1011 return makeTruthVal(true, resultTy); 1012 } 1013 } 1014 1015 // Handle special cases for when both regions are element regions. 1016 const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR); 1017 const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR); 1018 if (RightER && LeftER) { 1019 // Next, see if the two ERs have the same super-region and matching types. 1020 // FIXME: This should do something useful even if the types don't match, 1021 // though if both indexes are constant the RegionRawOffset path will 1022 // give the correct answer. 1023 if (LeftER->getSuperRegion() == RightER->getSuperRegion() && 1024 LeftER->getElementType() == RightER->getElementType()) { 1025 // Get the left index and cast it to the correct type. 1026 // If the index is unknown or undefined, bail out here. 1027 SVal LeftIndexVal = LeftER->getIndex(); 1028 Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>(); 1029 if (!LeftIndex) 1030 return UnknownVal(); 1031 LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy); 1032 LeftIndex = LeftIndexVal.getAs<NonLoc>(); 1033 if (!LeftIndex) 1034 return UnknownVal(); 1035 1036 // Do the same for the right index. 1037 SVal RightIndexVal = RightER->getIndex(); 1038 Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>(); 1039 if (!RightIndex) 1040 return UnknownVal(); 1041 RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy); 1042 RightIndex = RightIndexVal.getAs<NonLoc>(); 1043 if (!RightIndex) 1044 return UnknownVal(); 1045 1046 // Actually perform the operation. 1047 // evalBinOpNN expects the two indexes to already be the right type. 1048 return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy); 1049 } 1050 } 1051 1052 // Special handling of the FieldRegions, even with symbolic offsets. 1053 const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR); 1054 const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR); 1055 if (RightFR && LeftFR) { 1056 SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy, 1057 *this); 1058 if (!R.isUnknown()) 1059 return R; 1060 } 1061 1062 // Compare the regions using the raw offsets. 1063 RegionOffset LeftOffset = LeftMR->getAsOffset(); 1064 RegionOffset RightOffset = RightMR->getAsOffset(); 1065 1066 if (LeftOffset.getRegion() != nullptr && 1067 LeftOffset.getRegion() == RightOffset.getRegion() && 1068 !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) { 1069 int64_t left = LeftOffset.getOffset(); 1070 int64_t right = RightOffset.getOffset(); 1071 1072 switch (op) { 1073 default: 1074 return UnknownVal(); 1075 case BO_LT: 1076 return makeTruthVal(left < right, resultTy); 1077 case BO_GT: 1078 return makeTruthVal(left > right, resultTy); 1079 case BO_LE: 1080 return makeTruthVal(left <= right, resultTy); 1081 case BO_GE: 1082 return makeTruthVal(left >= right, resultTy); 1083 case BO_EQ: 1084 return makeTruthVal(left == right, resultTy); 1085 case BO_NE: 1086 return makeTruthVal(left != right, resultTy); 1087 } 1088 } 1089 1090 // At this point we're not going to get a good answer, but we can try 1091 // conjuring an expression instead. 1092 SymbolRef LHSSym = lhs.getAsLocSymbol(); 1093 SymbolRef RHSSym = rhs.getAsLocSymbol(); 1094 if (LHSSym && RHSSym) 1095 return makeNonLoc(LHSSym, op, RHSSym, resultTy); 1096 1097 // If we get here, we have no way of comparing the regions. 1098 return UnknownVal(); 1099 } 1100 } 1101 } 1102 1103 SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state, 1104 BinaryOperator::Opcode op, 1105 Loc lhs, NonLoc rhs, QualType resultTy) { 1106 if (op >= BO_PtrMemD && op <= BO_PtrMemI) { 1107 if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) { 1108 if (PTMSV->isNullMemberPointer()) 1109 return UndefinedVal(); 1110 if (const FieldDecl *FD = PTMSV->getDeclAs<FieldDecl>()) { 1111 SVal Result = lhs; 1112 1113 for (const auto &I : *PTMSV) 1114 Result = StateMgr.getStoreManager().evalDerivedToBase( 1115 Result, I->getType(),I->isVirtual()); 1116 return state->getLValue(FD, Result); 1117 } 1118 } 1119 1120 return rhs; 1121 } 1122 1123 assert(!BinaryOperator::isComparisonOp(op) && 1124 "arguments to comparison ops must be of the same type"); 1125 1126 // Special case: rhs is a zero constant. 1127 if (rhs.isZeroConstant()) 1128 return lhs; 1129 1130 // Perserve the null pointer so that it can be found by the DerefChecker. 1131 if (lhs.isZeroConstant()) 1132 return lhs; 1133 1134 // We are dealing with pointer arithmetic. 1135 1136 // Handle pointer arithmetic on constant values. 1137 if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) { 1138 if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) { 1139 const llvm::APSInt &leftI = lhsInt->getValue(); 1140 assert(leftI.isUnsigned()); 1141 llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true); 1142 1143 // Convert the bitwidth of rightI. This should deal with overflow 1144 // since we are dealing with concrete values. 1145 rightI = rightI.extOrTrunc(leftI.getBitWidth()); 1146 1147 // Offset the increment by the pointer size. 1148 llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true); 1149 QualType pointeeType = resultTy->getPointeeType(); 1150 Multiplicand = getContext().getTypeSizeInChars(pointeeType).getQuantity(); 1151 rightI *= Multiplicand; 1152 1153 // Compute the adjusted pointer. 1154 switch (op) { 1155 case BO_Add: 1156 rightI = leftI + rightI; 1157 break; 1158 case BO_Sub: 1159 rightI = leftI - rightI; 1160 break; 1161 default: 1162 llvm_unreachable("Invalid pointer arithmetic operation"); 1163 } 1164 return loc::ConcreteInt(getBasicValueFactory().getValue(rightI)); 1165 } 1166 } 1167 1168 // Handle cases where 'lhs' is a region. 1169 if (const MemRegion *region = lhs.getAsRegion()) { 1170 rhs = convertToArrayIndex(rhs).castAs<NonLoc>(); 1171 SVal index = UnknownVal(); 1172 const SubRegion *superR = nullptr; 1173 // We need to know the type of the pointer in order to add an integer to it. 1174 // Depending on the type, different amount of bytes is added. 1175 QualType elementType; 1176 1177 if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) { 1178 assert(op == BO_Add || op == BO_Sub); 1179 index = evalBinOpNN(state, op, elemReg->getIndex(), rhs, 1180 getArrayIndexType()); 1181 superR = cast<SubRegion>(elemReg->getSuperRegion()); 1182 elementType = elemReg->getElementType(); 1183 } 1184 else if (isa<SubRegion>(region)) { 1185 assert(op == BO_Add || op == BO_Sub); 1186 index = (op == BO_Add) ? rhs : evalMinus(rhs); 1187 superR = cast<SubRegion>(region); 1188 // TODO: Is this actually reliable? Maybe improving our MemRegion 1189 // hierarchy to provide typed regions for all non-void pointers would be 1190 // better. For instance, we cannot extend this towards LocAsInteger 1191 // operations, where result type of the expression is integer. 1192 if (resultTy->isAnyPointerType()) 1193 elementType = resultTy->getPointeeType(); 1194 } 1195 1196 // Represent arithmetic on void pointers as arithmetic on char pointers. 1197 // It is fine when a TypedValueRegion of char value type represents 1198 // a void pointer. Note that arithmetic on void pointers is a GCC extension. 1199 if (elementType->isVoidType()) 1200 elementType = getContext().CharTy; 1201 1202 if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) { 1203 return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV, 1204 superR, getContext())); 1205 } 1206 } 1207 return UnknownVal(); 1208 } 1209 1210 const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state, 1211 SVal V) { 1212 V = simplifySVal(state, V); 1213 if (V.isUnknownOrUndef()) 1214 return nullptr; 1215 1216 if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>()) 1217 return &X->getValue(); 1218 1219 if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>()) 1220 return &X->getValue(); 1221 1222 if (SymbolRef Sym = V.getAsSymbol()) 1223 return state->getConstraintManager().getSymVal(state, Sym); 1224 1225 // FIXME: Add support for SymExprs. 1226 return nullptr; 1227 } 1228 1229 SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) { 1230 // For now, this function tries to constant-fold symbols inside a 1231 // nonloc::SymbolVal, and does nothing else. More simplifications should 1232 // be possible, such as constant-folding an index in an ElementRegion. 1233 1234 class Simplifier : public FullSValVisitor<Simplifier, SVal> { 1235 ProgramStateRef State; 1236 SValBuilder &SVB; 1237 1238 // Cache results for the lifetime of the Simplifier. Results change every 1239 // time new constraints are added to the program state, which is the whole 1240 // point of simplifying, and for that very reason it's pointless to maintain 1241 // the same cache for the duration of the whole analysis. 1242 llvm::DenseMap<SymbolRef, SVal> Cached; 1243 1244 static bool isUnchanged(SymbolRef Sym, SVal Val) { 1245 return Sym == Val.getAsSymbol(); 1246 } 1247 1248 SVal cache(SymbolRef Sym, SVal V) { 1249 Cached[Sym] = V; 1250 return V; 1251 } 1252 1253 SVal skip(SymbolRef Sym) { 1254 return cache(Sym, SVB.makeSymbolVal(Sym)); 1255 } 1256 1257 public: 1258 Simplifier(ProgramStateRef State) 1259 : State(State), SVB(State->getStateManager().getSValBuilder()) {} 1260 1261 SVal VisitSymbolData(const SymbolData *S) { 1262 // No cache here. 1263 if (const llvm::APSInt *I = 1264 SVB.getKnownValue(State, SVB.makeSymbolVal(S))) 1265 return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I) 1266 : (SVal)SVB.makeIntVal(*I); 1267 return SVB.makeSymbolVal(S); 1268 } 1269 1270 // TODO: Support SymbolCast. Support IntSymExpr when/if we actually 1271 // start producing them. 1272 1273 SVal VisitSymIntExpr(const SymIntExpr *S) { 1274 auto I = Cached.find(S); 1275 if (I != Cached.end()) 1276 return I->second; 1277 1278 SVal LHS = Visit(S->getLHS()); 1279 if (isUnchanged(S->getLHS(), LHS)) 1280 return skip(S); 1281 1282 SVal RHS; 1283 // By looking at the APSInt in the right-hand side of S, we cannot 1284 // figure out if it should be treated as a Loc or as a NonLoc. 1285 // So make our guess by recalling that we cannot multiply pointers 1286 // or compare a pointer to an integer. 1287 if (Loc::isLocType(S->getLHS()->getType()) && 1288 BinaryOperator::isComparisonOp(S->getOpcode())) { 1289 // The usual conversion of $sym to &SymRegion{$sym}, as they have 1290 // the same meaning for Loc-type symbols, but the latter form 1291 // is preferred in SVal computations for being Loc itself. 1292 if (SymbolRef Sym = LHS.getAsSymbol()) { 1293 assert(Loc::isLocType(Sym->getType())); 1294 LHS = SVB.makeLoc(Sym); 1295 } 1296 RHS = SVB.makeIntLocVal(S->getRHS()); 1297 } else { 1298 RHS = SVB.makeIntVal(S->getRHS()); 1299 } 1300 1301 return cache( 1302 S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType())); 1303 } 1304 1305 SVal VisitSymSymExpr(const SymSymExpr *S) { 1306 auto I = Cached.find(S); 1307 if (I != Cached.end()) 1308 return I->second; 1309 1310 // For now don't try to simplify mixed Loc/NonLoc expressions 1311 // because they often appear from LocAsInteger operations 1312 // and we don't know how to combine a LocAsInteger 1313 // with a concrete value. 1314 if (Loc::isLocType(S->getLHS()->getType()) != 1315 Loc::isLocType(S->getRHS()->getType())) 1316 return skip(S); 1317 1318 SVal LHS = Visit(S->getLHS()); 1319 SVal RHS = Visit(S->getRHS()); 1320 if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS)) 1321 return skip(S); 1322 1323 return cache( 1324 S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType())); 1325 } 1326 1327 SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); } 1328 1329 SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); } 1330 1331 SVal VisitNonLocSymbolVal(nonloc::SymbolVal V) { 1332 // Simplification is much more costly than computing complexity. 1333 // For high complexity, it may be not worth it. 1334 return Visit(V.getSymbol()); 1335 } 1336 1337 SVal VisitSVal(SVal V) { return V; } 1338 }; 1339 1340 // A crude way of preventing this function from calling itself from evalBinOp. 1341 static bool isReentering = false; 1342 if (isReentering) 1343 return V; 1344 1345 isReentering = true; 1346 SVal SimplifiedV = Simplifier(State).Visit(V); 1347 isReentering = false; 1348 1349 return SimplifiedV; 1350 } 1351