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 14 #include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" 15 #include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h" 16 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 17 18 using namespace clang; 19 using namespace ento; 20 21 namespace { 22 class SimpleSValBuilder : public SValBuilder { 23 protected: 24 virtual SVal dispatchCast(SVal val, QualType castTy); 25 virtual SVal evalCastFromNonLoc(NonLoc val, QualType castTy); 26 virtual SVal evalCastFromLoc(Loc val, QualType castTy); 27 28 public: 29 SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context, 30 ProgramStateManager &stateMgr) 31 : SValBuilder(alloc, context, stateMgr) {} 32 virtual ~SimpleSValBuilder() {} 33 34 virtual SVal evalMinus(NonLoc val); 35 virtual SVal evalComplement(NonLoc val); 36 virtual SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op, 37 NonLoc lhs, NonLoc rhs, QualType resultTy); 38 virtual SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op, 39 Loc lhs, Loc rhs, QualType resultTy); 40 virtual SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op, 41 Loc lhs, NonLoc rhs, QualType resultTy); 42 43 /// getKnownValue - evaluates a given SVal. If the SVal has only one possible 44 /// (integer) value, that value is returned. Otherwise, returns NULL. 45 virtual const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V); 46 47 SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op, 48 const llvm::APSInt &RHS, QualType resultTy); 49 }; 50 } // end anonymous namespace 51 52 SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc, 53 ASTContext &context, 54 ProgramStateManager &stateMgr) { 55 return new SimpleSValBuilder(alloc, context, stateMgr); 56 } 57 58 //===----------------------------------------------------------------------===// 59 // Transfer function for Casts. 60 //===----------------------------------------------------------------------===// 61 62 SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) { 63 assert(Val.getAs<Loc>() || Val.getAs<NonLoc>()); 64 return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy) 65 : evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy); 66 } 67 68 SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) { 69 70 bool isLocType = Loc::isLocType(castTy); 71 72 if (Optional<nonloc::LocAsInteger> LI = val.getAs<nonloc::LocAsInteger>()) { 73 if (isLocType) 74 return LI->getLoc(); 75 76 // FIXME: Correctly support promotions/truncations. 77 unsigned castSize = Context.getTypeSize(castTy); 78 if (castSize == LI->getNumBits()) 79 return val; 80 return makeLocAsInteger(LI->getLoc(), castSize); 81 } 82 83 if (const SymExpr *se = val.getAsSymbolicExpression()) { 84 QualType T = Context.getCanonicalType(se->getType()); 85 // If types are the same or both are integers, ignore the cast. 86 // FIXME: Remove this hack when we support symbolic truncation/extension. 87 // HACK: If both castTy and T are integers, ignore the cast. This is 88 // not a permanent solution. Eventually we want to precisely handle 89 // extension/truncation of symbolic integers. This prevents us from losing 90 // precision when we assign 'x = y' and 'y' is symbolic and x and y are 91 // different integer types. 92 if (haveSameType(T, castTy)) 93 return val; 94 95 if (!isLocType) 96 return makeNonLoc(se, T, castTy); 97 return UnknownVal(); 98 } 99 100 // If value is a non integer constant, produce unknown. 101 if (!val.getAs<nonloc::ConcreteInt>()) 102 return UnknownVal(); 103 104 // Handle casts to a boolean type. 105 if (castTy->isBooleanType()) { 106 bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue(); 107 return makeTruthVal(b, castTy); 108 } 109 110 // Only handle casts from integers to integers - if val is an integer constant 111 // being cast to a non integer type, produce unknown. 112 if (!isLocType && !castTy->isIntegerType()) 113 return UnknownVal(); 114 115 llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue(); 116 BasicVals.getAPSIntType(castTy).apply(i); 117 118 if (isLocType) 119 return makeIntLocVal(i); 120 else 121 return makeIntVal(i); 122 } 123 124 SVal SimpleSValBuilder::evalCastFromLoc(Loc val, QualType castTy) { 125 126 // Casts from pointers -> pointers, just return the lval. 127 // 128 // Casts from pointers -> references, just return the lval. These 129 // can be introduced by the frontend for corner cases, e.g 130 // casting from va_list* to __builtin_va_list&. 131 // 132 if (Loc::isLocType(castTy) || castTy->isReferenceType()) 133 return val; 134 135 // FIXME: Handle transparent unions where a value can be "transparently" 136 // lifted into a union type. 137 if (castTy->isUnionType()) 138 return UnknownVal(); 139 140 if (castTy->isIntegerType()) { 141 unsigned BitWidth = Context.getTypeSize(castTy); 142 143 if (!val.getAs<loc::ConcreteInt>()) 144 return makeLocAsInteger(val, BitWidth); 145 146 llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue(); 147 BasicVals.getAPSIntType(castTy).apply(i); 148 return makeIntVal(i); 149 } 150 151 // All other cases: return 'UnknownVal'. This includes casting pointers 152 // to floats, which is probably badness it itself, but this is a good 153 // intermediate solution until we do something better. 154 return UnknownVal(); 155 } 156 157 //===----------------------------------------------------------------------===// 158 // Transfer function for unary operators. 159 //===----------------------------------------------------------------------===// 160 161 SVal SimpleSValBuilder::evalMinus(NonLoc val) { 162 switch (val.getSubKind()) { 163 case nonloc::ConcreteIntKind: 164 return val.castAs<nonloc::ConcreteInt>().evalMinus(*this); 165 default: 166 return UnknownVal(); 167 } 168 } 169 170 SVal SimpleSValBuilder::evalComplement(NonLoc X) { 171 switch (X.getSubKind()) { 172 case nonloc::ConcreteIntKind: 173 return X.castAs<nonloc::ConcreteInt>().evalComplement(*this); 174 default: 175 return UnknownVal(); 176 } 177 } 178 179 //===----------------------------------------------------------------------===// 180 // Transfer function for binary operators. 181 //===----------------------------------------------------------------------===// 182 183 static BinaryOperator::Opcode NegateComparison(BinaryOperator::Opcode op) { 184 switch (op) { 185 default: 186 llvm_unreachable("Invalid opcode."); 187 case BO_LT: return BO_GE; 188 case BO_GT: return BO_LE; 189 case BO_LE: return BO_GT; 190 case BO_GE: return BO_LT; 191 case BO_EQ: return BO_NE; 192 case BO_NE: return BO_EQ; 193 } 194 } 195 196 static BinaryOperator::Opcode ReverseComparison(BinaryOperator::Opcode op) { 197 switch (op) { 198 default: 199 llvm_unreachable("Invalid opcode."); 200 case BO_LT: return BO_GT; 201 case BO_GT: return BO_LT; 202 case BO_LE: return BO_GE; 203 case BO_GE: return BO_LE; 204 case BO_EQ: 205 case BO_NE: 206 return op; 207 } 208 } 209 210 SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS, 211 BinaryOperator::Opcode op, 212 const llvm::APSInt &RHS, 213 QualType resultTy) { 214 bool isIdempotent = false; 215 216 // Check for a few special cases with known reductions first. 217 switch (op) { 218 default: 219 // We can't reduce this case; just treat it normally. 220 break; 221 case BO_Mul: 222 // a*0 and a*1 223 if (RHS == 0) 224 return makeIntVal(0, resultTy); 225 else if (RHS == 1) 226 isIdempotent = true; 227 break; 228 case BO_Div: 229 // a/0 and a/1 230 if (RHS == 0) 231 // This is also handled elsewhere. 232 return UndefinedVal(); 233 else if (RHS == 1) 234 isIdempotent = true; 235 break; 236 case BO_Rem: 237 // a%0 and a%1 238 if (RHS == 0) 239 // This is also handled elsewhere. 240 return UndefinedVal(); 241 else if (RHS == 1) 242 return makeIntVal(0, resultTy); 243 break; 244 case BO_Add: 245 case BO_Sub: 246 case BO_Shl: 247 case BO_Shr: 248 case BO_Xor: 249 // a+0, a-0, a<<0, a>>0, a^0 250 if (RHS == 0) 251 isIdempotent = true; 252 break; 253 case BO_And: 254 // a&0 and a&(~0) 255 if (RHS == 0) 256 return makeIntVal(0, resultTy); 257 else if (RHS.isAllOnesValue()) 258 isIdempotent = true; 259 break; 260 case BO_Or: 261 // a|0 and a|(~0) 262 if (RHS == 0) 263 isIdempotent = true; 264 else if (RHS.isAllOnesValue()) { 265 const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS); 266 return nonloc::ConcreteInt(Result); 267 } 268 break; 269 } 270 271 // Idempotent ops (like a*1) can still change the type of an expression. 272 // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the 273 // dirty work. 274 if (isIdempotent) 275 return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy); 276 277 // If we reach this point, the expression cannot be simplified. 278 // Make a SymbolVal for the entire expression, after converting the RHS. 279 const llvm::APSInt *ConvertedRHS = &RHS; 280 if (BinaryOperator::isComparisonOp(op)) { 281 // We're looking for a type big enough to compare the symbolic value 282 // with the given constant. 283 // FIXME: This is an approximation of Sema::UsualArithmeticConversions. 284 ASTContext &Ctx = getContext(); 285 QualType SymbolType = LHS->getType(); 286 uint64_t ValWidth = RHS.getBitWidth(); 287 uint64_t TypeWidth = Ctx.getTypeSize(SymbolType); 288 289 if (ValWidth < TypeWidth) { 290 // If the value is too small, extend it. 291 ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); 292 } else if (ValWidth == TypeWidth) { 293 // If the value is signed but the symbol is unsigned, do the comparison 294 // in unsigned space. [C99 6.3.1.8] 295 // (For the opposite case, the value is already unsigned.) 296 if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType()) 297 ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); 298 } 299 } else 300 ConvertedRHS = &BasicVals.Convert(resultTy, RHS); 301 302 return makeNonLoc(LHS, op, *ConvertedRHS, resultTy); 303 } 304 305 SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state, 306 BinaryOperator::Opcode op, 307 NonLoc lhs, NonLoc rhs, 308 QualType resultTy) { 309 NonLoc InputLHS = lhs; 310 NonLoc InputRHS = rhs; 311 312 // Handle trivial case where left-side and right-side are the same. 313 if (lhs == rhs) 314 switch (op) { 315 default: 316 break; 317 case BO_EQ: 318 case BO_LE: 319 case BO_GE: 320 return makeTruthVal(true, resultTy); 321 case BO_LT: 322 case BO_GT: 323 case BO_NE: 324 return makeTruthVal(false, resultTy); 325 case BO_Xor: 326 case BO_Sub: 327 if (resultTy->isIntegralOrEnumerationType()) 328 return makeIntVal(0, resultTy); 329 return evalCastFromNonLoc(makeIntVal(0, /*Unsigned=*/false), resultTy); 330 case BO_Or: 331 case BO_And: 332 return evalCastFromNonLoc(lhs, resultTy); 333 } 334 335 while (1) { 336 switch (lhs.getSubKind()) { 337 default: 338 return makeSymExprValNN(state, op, lhs, rhs, resultTy); 339 case nonloc::LocAsIntegerKind: { 340 Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc(); 341 switch (rhs.getSubKind()) { 342 case nonloc::LocAsIntegerKind: 343 return evalBinOpLL(state, op, lhsL, 344 rhs.castAs<nonloc::LocAsInteger>().getLoc(), 345 resultTy); 346 case nonloc::ConcreteIntKind: { 347 // Transform the integer into a location and compare. 348 llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue(); 349 BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i); 350 return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy); 351 } 352 default: 353 switch (op) { 354 case BO_EQ: 355 return makeTruthVal(false, resultTy); 356 case BO_NE: 357 return makeTruthVal(true, resultTy); 358 default: 359 // This case also handles pointer arithmetic. 360 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 361 } 362 } 363 } 364 case nonloc::ConcreteIntKind: { 365 llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue(); 366 367 // If we're dealing with two known constants, just perform the operation. 368 if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) { 369 llvm::APSInt RHSValue = *KnownRHSValue; 370 if (BinaryOperator::isComparisonOp(op)) { 371 // We're looking for a type big enough to compare the two values. 372 // FIXME: This is not correct. char + short will result in a promotion 373 // to int. Unfortunately we have lost types by this point. 374 APSIntType CompareType = std::max(APSIntType(LHSValue), 375 APSIntType(RHSValue)); 376 CompareType.apply(LHSValue); 377 CompareType.apply(RHSValue); 378 } else if (!BinaryOperator::isShiftOp(op)) { 379 APSIntType IntType = BasicVals.getAPSIntType(resultTy); 380 IntType.apply(LHSValue); 381 IntType.apply(RHSValue); 382 } 383 384 const llvm::APSInt *Result = 385 BasicVals.evalAPSInt(op, LHSValue, RHSValue); 386 if (!Result) 387 return UndefinedVal(); 388 389 return nonloc::ConcreteInt(*Result); 390 } 391 392 // Swap the left and right sides and flip the operator if doing so 393 // allows us to better reason about the expression (this is a form 394 // of expression canonicalization). 395 // While we're at it, catch some special cases for non-commutative ops. 396 switch (op) { 397 case BO_LT: 398 case BO_GT: 399 case BO_LE: 400 case BO_GE: 401 op = ReverseComparison(op); 402 // FALL-THROUGH 403 case BO_EQ: 404 case BO_NE: 405 case BO_Add: 406 case BO_Mul: 407 case BO_And: 408 case BO_Xor: 409 case BO_Or: 410 std::swap(lhs, rhs); 411 continue; 412 case BO_Shr: 413 // (~0)>>a 414 if (LHSValue.isAllOnesValue() && LHSValue.isSigned()) 415 return evalCastFromNonLoc(lhs, resultTy); 416 // FALL-THROUGH 417 case BO_Shl: 418 // 0<<a and 0>>a 419 if (LHSValue == 0) 420 return evalCastFromNonLoc(lhs, resultTy); 421 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 422 default: 423 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 424 } 425 } 426 case nonloc::SymbolValKind: { 427 // We only handle LHS as simple symbols or SymIntExprs. 428 SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol(); 429 430 // LHS is a symbolic expression. 431 if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) { 432 433 // Is this a logical not? (!x is represented as x == 0.) 434 if (op == BO_EQ && rhs.isZeroConstant()) { 435 // We know how to negate certain expressions. Simplify them here. 436 437 BinaryOperator::Opcode opc = symIntExpr->getOpcode(); 438 switch (opc) { 439 default: 440 // We don't know how to negate this operation. 441 // Just handle it as if it were a normal comparison to 0. 442 break; 443 case BO_LAnd: 444 case BO_LOr: 445 llvm_unreachable("Logical operators handled by branching logic."); 446 case BO_Assign: 447 case BO_MulAssign: 448 case BO_DivAssign: 449 case BO_RemAssign: 450 case BO_AddAssign: 451 case BO_SubAssign: 452 case BO_ShlAssign: 453 case BO_ShrAssign: 454 case BO_AndAssign: 455 case BO_XorAssign: 456 case BO_OrAssign: 457 case BO_Comma: 458 llvm_unreachable("'=' and ',' operators handled by ExprEngine."); 459 case BO_PtrMemD: 460 case BO_PtrMemI: 461 llvm_unreachable("Pointer arithmetic not handled here."); 462 case BO_LT: 463 case BO_GT: 464 case BO_LE: 465 case BO_GE: 466 case BO_EQ: 467 case BO_NE: 468 // Negate the comparison and make a value. 469 opc = NegateComparison(opc); 470 assert(symIntExpr->getType() == resultTy); 471 return makeNonLoc(symIntExpr->getLHS(), opc, 472 symIntExpr->getRHS(), resultTy); 473 } 474 } 475 476 // For now, only handle expressions whose RHS is a constant. 477 if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) { 478 // If both the LHS and the current expression are additive, 479 // fold their constants and try again. 480 if (BinaryOperator::isAdditiveOp(op)) { 481 BinaryOperator::Opcode lop = symIntExpr->getOpcode(); 482 if (BinaryOperator::isAdditiveOp(lop)) { 483 // Convert the two constants to a common type, then combine them. 484 485 // resultTy may not be the best type to convert to, but it's 486 // probably the best choice in expressions with mixed type 487 // (such as x+1U+2LL). The rules for implicit conversions should 488 // choose a reasonable type to preserve the expression, and will 489 // at least match how the value is going to be used. 490 APSIntType IntType = BasicVals.getAPSIntType(resultTy); 491 const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS()); 492 const llvm::APSInt &second = IntType.convert(*RHSValue); 493 494 const llvm::APSInt *newRHS; 495 if (lop == op) 496 newRHS = BasicVals.evalAPSInt(BO_Add, first, second); 497 else 498 newRHS = BasicVals.evalAPSInt(BO_Sub, first, second); 499 500 assert(newRHS && "Invalid operation despite common type!"); 501 rhs = nonloc::ConcreteInt(*newRHS); 502 lhs = nonloc::SymbolVal(symIntExpr->getLHS()); 503 op = lop; 504 continue; 505 } 506 } 507 508 // Otherwise, make a SymIntExpr out of the expression. 509 return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy); 510 } 511 512 513 } else if (isa<SymbolData>(Sym)) { 514 // Does the symbol simplify to a constant? If so, "fold" the constant 515 // by setting 'lhs' to a ConcreteInt and try again. 516 if (const llvm::APSInt *Constant = state->getConstraintManager() 517 .getSymVal(state, Sym)) { 518 lhs = nonloc::ConcreteInt(*Constant); 519 continue; 520 } 521 522 // Is the RHS a constant? 523 if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) 524 return MakeSymIntVal(Sym, op, *RHSValue, resultTy); 525 } 526 527 // Give up -- this is not a symbolic expression we can handle. 528 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 529 } 530 } 531 } 532 } 533 534 // FIXME: all this logic will change if/when we have MemRegion::getLocation(). 535 SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state, 536 BinaryOperator::Opcode op, 537 Loc lhs, Loc rhs, 538 QualType resultTy) { 539 // Only comparisons and subtractions are valid operations on two pointers. 540 // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15]. 541 // However, if a pointer is casted to an integer, evalBinOpNN may end up 542 // calling this function with another operation (PR7527). We don't attempt to 543 // model this for now, but it could be useful, particularly when the 544 // "location" is actually an integer value that's been passed through a void*. 545 if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub)) 546 return UnknownVal(); 547 548 // Special cases for when both sides are identical. 549 if (lhs == rhs) { 550 switch (op) { 551 default: 552 llvm_unreachable("Unimplemented operation for two identical values"); 553 case BO_Sub: 554 return makeZeroVal(resultTy); 555 case BO_EQ: 556 case BO_LE: 557 case BO_GE: 558 return makeTruthVal(true, resultTy); 559 case BO_NE: 560 case BO_LT: 561 case BO_GT: 562 return makeTruthVal(false, resultTy); 563 } 564 } 565 566 switch (lhs.getSubKind()) { 567 default: 568 llvm_unreachable("Ordering not implemented for this Loc."); 569 570 case loc::GotoLabelKind: 571 // The only thing we know about labels is that they're non-null. 572 if (rhs.isZeroConstant()) { 573 switch (op) { 574 default: 575 break; 576 case BO_Sub: 577 return evalCastFromLoc(lhs, resultTy); 578 case BO_EQ: 579 case BO_LE: 580 case BO_LT: 581 return makeTruthVal(false, resultTy); 582 case BO_NE: 583 case BO_GT: 584 case BO_GE: 585 return makeTruthVal(true, resultTy); 586 } 587 } 588 // There may be two labels for the same location, and a function region may 589 // have the same address as a label at the start of the function (depending 590 // on the ABI). 591 // FIXME: we can probably do a comparison against other MemRegions, though. 592 // FIXME: is there a way to tell if two labels refer to the same location? 593 return UnknownVal(); 594 595 case loc::ConcreteIntKind: { 596 // If one of the operands is a symbol and the other is a constant, 597 // build an expression for use by the constraint manager. 598 if (SymbolRef rSym = rhs.getAsLocSymbol()) { 599 // We can only build expressions with symbols on the left, 600 // so we need a reversible operator. 601 if (!BinaryOperator::isComparisonOp(op)) 602 return UnknownVal(); 603 604 const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue(); 605 return makeNonLoc(rSym, ReverseComparison(op), lVal, resultTy); 606 } 607 608 // If both operands are constants, just perform the operation. 609 if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) { 610 SVal ResultVal = 611 lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt); 612 if (Optional<Loc> Result = ResultVal.getAs<Loc>()) 613 return evalCastFromLoc(*Result, resultTy); 614 else 615 return UnknownVal(); 616 } 617 618 // Special case comparisons against NULL. 619 // This must come after the test if the RHS is a symbol, which is used to 620 // build constraints. The address of any non-symbolic region is guaranteed 621 // to be non-NULL, as is any label. 622 assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>()); 623 if (lhs.isZeroConstant()) { 624 switch (op) { 625 default: 626 break; 627 case BO_EQ: 628 case BO_GT: 629 case BO_GE: 630 return makeTruthVal(false, resultTy); 631 case BO_NE: 632 case BO_LT: 633 case BO_LE: 634 return makeTruthVal(true, resultTy); 635 } 636 } 637 638 // Comparing an arbitrary integer to a region or label address is 639 // completely unknowable. 640 return UnknownVal(); 641 } 642 case loc::MemRegionKind: { 643 if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) { 644 // If one of the operands is a symbol and the other is a constant, 645 // build an expression for use by the constraint manager. 646 if (SymbolRef lSym = lhs.getAsLocSymbol()) 647 return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy); 648 649 // Special case comparisons to NULL. 650 // This must come after the test if the LHS is a symbol, which is used to 651 // build constraints. The address of any non-symbolic region is guaranteed 652 // to be non-NULL. 653 if (rInt->isZeroConstant()) { 654 switch (op) { 655 default: 656 break; 657 case BO_Sub: 658 return evalCastFromLoc(lhs, resultTy); 659 case BO_EQ: 660 case BO_LT: 661 case BO_LE: 662 return makeTruthVal(false, resultTy); 663 case BO_NE: 664 case BO_GT: 665 case BO_GE: 666 return makeTruthVal(true, resultTy); 667 } 668 } 669 670 // Comparing a region to an arbitrary integer is completely unknowable. 671 return UnknownVal(); 672 } 673 674 // Get both values as regions, if possible. 675 const MemRegion *LeftMR = lhs.getAsRegion(); 676 assert(LeftMR && "MemRegionKind SVal doesn't have a region!"); 677 678 const MemRegion *RightMR = rhs.getAsRegion(); 679 if (!RightMR) 680 // The RHS is probably a label, which in theory could address a region. 681 // FIXME: we can probably make a more useful statement about non-code 682 // regions, though. 683 return UnknownVal(); 684 685 const MemSpaceRegion *LeftMS = LeftMR->getMemorySpace(); 686 const MemSpaceRegion *RightMS = RightMR->getMemorySpace(); 687 const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion(); 688 const MemRegion *LeftBase = LeftMR->getBaseRegion(); 689 const MemRegion *RightBase = RightMR->getBaseRegion(); 690 691 // If the two regions are from different known memory spaces they cannot be 692 // equal. Also, assume that no symbolic region (whose memory space is 693 // unknown) is on the stack. 694 if (LeftMS != RightMS && 695 ((LeftMS != UnknownMS && RightMS != UnknownMS) || 696 (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) { 697 switch (op) { 698 default: 699 return UnknownVal(); 700 case BO_EQ: 701 return makeTruthVal(false, resultTy); 702 case BO_NE: 703 return makeTruthVal(true, resultTy); 704 } 705 } 706 707 // If both values wrap regions, see if they're from different base regions. 708 // Note, heap base symbolic regions are assumed to not alias with 709 // each other; for example, we assume that malloc returns different address 710 // on each invocation. 711 if (LeftBase != RightBase && 712 ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) || 713 (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){ 714 switch (op) { 715 default: 716 return UnknownVal(); 717 case BO_EQ: 718 return makeTruthVal(false, resultTy); 719 case BO_NE: 720 return makeTruthVal(true, resultTy); 721 } 722 } 723 724 // FIXME: If/when there is a getAsRawOffset() for FieldRegions, this 725 // ElementRegion path and the FieldRegion path below should be unified. 726 if (const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR)) { 727 // First see if the right region is also an ElementRegion. 728 const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR); 729 if (!RightER) 730 return UnknownVal(); 731 732 // Next, see if the two ERs have the same super-region and matching types. 733 // FIXME: This should do something useful even if the types don't match, 734 // though if both indexes are constant the RegionRawOffset path will 735 // give the correct answer. 736 if (LeftER->getSuperRegion() == RightER->getSuperRegion() && 737 LeftER->getElementType() == RightER->getElementType()) { 738 // Get the left index and cast it to the correct type. 739 // If the index is unknown or undefined, bail out here. 740 SVal LeftIndexVal = LeftER->getIndex(); 741 Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>(); 742 if (!LeftIndex) 743 return UnknownVal(); 744 LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy); 745 LeftIndex = LeftIndexVal.getAs<NonLoc>(); 746 if (!LeftIndex) 747 return UnknownVal(); 748 749 // Do the same for the right index. 750 SVal RightIndexVal = RightER->getIndex(); 751 Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>(); 752 if (!RightIndex) 753 return UnknownVal(); 754 RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy); 755 RightIndex = RightIndexVal.getAs<NonLoc>(); 756 if (!RightIndex) 757 return UnknownVal(); 758 759 // Actually perform the operation. 760 // evalBinOpNN expects the two indexes to already be the right type. 761 return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy); 762 } 763 764 // If the element indexes aren't comparable, see if the raw offsets are. 765 RegionRawOffset LeftOffset = LeftER->getAsArrayOffset(); 766 RegionRawOffset RightOffset = RightER->getAsArrayOffset(); 767 768 if (LeftOffset.getRegion() != NULL && 769 LeftOffset.getRegion() == RightOffset.getRegion()) { 770 CharUnits left = LeftOffset.getOffset(); 771 CharUnits right = RightOffset.getOffset(); 772 773 switch (op) { 774 default: 775 return UnknownVal(); 776 case BO_LT: 777 return makeTruthVal(left < right, resultTy); 778 case BO_GT: 779 return makeTruthVal(left > right, resultTy); 780 case BO_LE: 781 return makeTruthVal(left <= right, resultTy); 782 case BO_GE: 783 return makeTruthVal(left >= right, resultTy); 784 case BO_EQ: 785 return makeTruthVal(left == right, resultTy); 786 case BO_NE: 787 return makeTruthVal(left != right, resultTy); 788 } 789 } 790 791 // If we get here, we have no way of comparing the ElementRegions. 792 return UnknownVal(); 793 } 794 795 // See if both regions are fields of the same structure. 796 // FIXME: This doesn't handle nesting, inheritance, or Objective-C ivars. 797 if (const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR)) { 798 // Only comparisons are meaningful here! 799 if (!BinaryOperator::isComparisonOp(op)) 800 return UnknownVal(); 801 802 // First see if the right region is also a FieldRegion. 803 const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR); 804 if (!RightFR) 805 return UnknownVal(); 806 807 // Next, see if the two FRs have the same super-region. 808 // FIXME: This doesn't handle casts yet, and simply stripping the casts 809 // doesn't help. 810 if (LeftFR->getSuperRegion() != RightFR->getSuperRegion()) 811 return UnknownVal(); 812 813 const FieldDecl *LeftFD = LeftFR->getDecl(); 814 const FieldDecl *RightFD = RightFR->getDecl(); 815 const RecordDecl *RD = LeftFD->getParent(); 816 817 // Make sure the two FRs are from the same kind of record. Just in case! 818 // FIXME: This is probably where inheritance would be a problem. 819 if (RD != RightFD->getParent()) 820 return UnknownVal(); 821 822 // We know for sure that the two fields are not the same, since that 823 // would have given us the same SVal. 824 if (op == BO_EQ) 825 return makeTruthVal(false, resultTy); 826 if (op == BO_NE) 827 return makeTruthVal(true, resultTy); 828 829 // Iterate through the fields and see which one comes first. 830 // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field 831 // members and the units in which bit-fields reside have addresses that 832 // increase in the order in which they are declared." 833 bool leftFirst = (op == BO_LT || op == BO_LE); 834 for (RecordDecl::field_iterator I = RD->field_begin(), 835 E = RD->field_end(); I!=E; ++I) { 836 if (*I == LeftFD) 837 return makeTruthVal(leftFirst, resultTy); 838 if (*I == RightFD) 839 return makeTruthVal(!leftFirst, resultTy); 840 } 841 842 llvm_unreachable("Fields not found in parent record's definition"); 843 } 844 845 // If we get here, we have no way of comparing the regions. 846 return UnknownVal(); 847 } 848 } 849 } 850 851 SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state, 852 BinaryOperator::Opcode op, 853 Loc lhs, NonLoc rhs, QualType resultTy) { 854 855 // Special case: rhs is a zero constant. 856 if (rhs.isZeroConstant()) 857 return lhs; 858 859 // Special case: 'rhs' is an integer that has the same width as a pointer and 860 // we are using the integer location in a comparison. Normally this cannot be 861 // triggered, but transfer functions like those for OSCompareAndSwapBarrier32 862 // can generate comparisons that trigger this code. 863 // FIXME: Are all locations guaranteed to have pointer width? 864 if (BinaryOperator::isComparisonOp(op)) { 865 if (Optional<nonloc::ConcreteInt> rhsInt = 866 rhs.getAs<nonloc::ConcreteInt>()) { 867 const llvm::APSInt *x = &rhsInt->getValue(); 868 ASTContext &ctx = Context; 869 if (ctx.getTypeSize(ctx.VoidPtrTy) == x->getBitWidth()) { 870 // Convert the signedness of the integer (if necessary). 871 if (x->isSigned()) 872 x = &getBasicValueFactory().getValue(*x, true); 873 874 return evalBinOpLL(state, op, lhs, loc::ConcreteInt(*x), resultTy); 875 } 876 } 877 return UnknownVal(); 878 } 879 880 // We are dealing with pointer arithmetic. 881 882 // Handle pointer arithmetic on constant values. 883 if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) { 884 if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) { 885 const llvm::APSInt &leftI = lhsInt->getValue(); 886 assert(leftI.isUnsigned()); 887 llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true); 888 889 // Convert the bitwidth of rightI. This should deal with overflow 890 // since we are dealing with concrete values. 891 rightI = rightI.extOrTrunc(leftI.getBitWidth()); 892 893 // Offset the increment by the pointer size. 894 llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true); 895 rightI *= Multiplicand; 896 897 // Compute the adjusted pointer. 898 switch (op) { 899 case BO_Add: 900 rightI = leftI + rightI; 901 break; 902 case BO_Sub: 903 rightI = leftI - rightI; 904 break; 905 default: 906 llvm_unreachable("Invalid pointer arithmetic operation"); 907 } 908 return loc::ConcreteInt(getBasicValueFactory().getValue(rightI)); 909 } 910 } 911 912 // Handle cases where 'lhs' is a region. 913 if (const MemRegion *region = lhs.getAsRegion()) { 914 rhs = convertToArrayIndex(rhs).castAs<NonLoc>(); 915 SVal index = UnknownVal(); 916 const MemRegion *superR = 0; 917 QualType elementType; 918 919 if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) { 920 assert(op == BO_Add || op == BO_Sub); 921 index = evalBinOpNN(state, op, elemReg->getIndex(), rhs, 922 getArrayIndexType()); 923 superR = elemReg->getSuperRegion(); 924 elementType = elemReg->getElementType(); 925 } 926 else if (isa<SubRegion>(region)) { 927 superR = region; 928 index = rhs; 929 if (resultTy->isAnyPointerType()) 930 elementType = resultTy->getPointeeType(); 931 } 932 933 if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) { 934 return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV, 935 superR, getContext())); 936 } 937 } 938 return UnknownVal(); 939 } 940 941 const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state, 942 SVal V) { 943 if (V.isUnknownOrUndef()) 944 return NULL; 945 946 if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>()) 947 return &X->getValue(); 948 949 if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>()) 950 return &X->getValue(); 951 952 if (SymbolRef Sym = V.getAsSymbol()) 953 return state->getConstraintManager().getSymVal(state, Sym); 954 955 // FIXME: Add support for SymExprs. 956 return NULL; 957 } 958