SimpleSValBuilder.cpp revision 4e45dba1c0234eec7b7c348dbbf568c5ac9fc471
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/APSIntType.h" 15#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" 16#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 17 18using namespace clang; 19using namespace ento; 20 21namespace { 22class SimpleSValBuilder : public SValBuilder { 23protected: 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 28public: 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 52SValBuilder *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 62SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) { 63 assert(isa<Loc>(&Val) || isa<NonLoc>(&Val)); 64 return isa<Loc>(Val) ? evalCastFromLoc(cast<Loc>(Val), CastTy) 65 : evalCastFromNonLoc(cast<NonLoc>(Val), CastTy); 66} 67 68SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) { 69 70 bool isLocType = Loc::isLocType(castTy); 71 72 if (nonloc::LocAsInteger *LI = dyn_cast<nonloc::LocAsInteger>(&val)) { 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(Context)); 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 (!isa<nonloc::ConcreteInt>(val)) 102 return UnknownVal(); 103 104 // Only handle casts from integers to integers - if val is an integer constant 105 // being cast to a non integer type, produce unknown. 106 if (!isLocType && !castTy->isIntegerType()) 107 return UnknownVal(); 108 109 llvm::APSInt i = cast<nonloc::ConcreteInt>(val).getValue(); 110 BasicVals.getAPSIntType(castTy).apply(i); 111 112 if (isLocType) 113 return makeIntLocVal(i); 114 else 115 return makeIntVal(i); 116} 117 118SVal SimpleSValBuilder::evalCastFromLoc(Loc val, QualType castTy) { 119 120 // Casts from pointers -> pointers, just return the lval. 121 // 122 // Casts from pointers -> references, just return the lval. These 123 // can be introduced by the frontend for corner cases, e.g 124 // casting from va_list* to __builtin_va_list&. 125 // 126 if (Loc::isLocType(castTy) || castTy->isReferenceType()) 127 return val; 128 129 // FIXME: Handle transparent unions where a value can be "transparently" 130 // lifted into a union type. 131 if (castTy->isUnionType()) 132 return UnknownVal(); 133 134 if (castTy->isIntegerType()) { 135 unsigned BitWidth = Context.getTypeSize(castTy); 136 137 if (!isa<loc::ConcreteInt>(val)) 138 return makeLocAsInteger(val, BitWidth); 139 140 llvm::APSInt i = cast<loc::ConcreteInt>(val).getValue(); 141 BasicVals.getAPSIntType(castTy).apply(i); 142 return makeIntVal(i); 143 } 144 145 // All other cases: return 'UnknownVal'. This includes casting pointers 146 // to floats, which is probably badness it itself, but this is a good 147 // intermediate solution until we do something better. 148 return UnknownVal(); 149} 150 151//===----------------------------------------------------------------------===// 152// Transfer function for unary operators. 153//===----------------------------------------------------------------------===// 154 155SVal SimpleSValBuilder::evalMinus(NonLoc val) { 156 switch (val.getSubKind()) { 157 case nonloc::ConcreteIntKind: 158 return cast<nonloc::ConcreteInt>(val).evalMinus(*this); 159 default: 160 return UnknownVal(); 161 } 162} 163 164SVal SimpleSValBuilder::evalComplement(NonLoc X) { 165 switch (X.getSubKind()) { 166 case nonloc::ConcreteIntKind: 167 return cast<nonloc::ConcreteInt>(X).evalComplement(*this); 168 default: 169 return UnknownVal(); 170 } 171} 172 173//===----------------------------------------------------------------------===// 174// Transfer function for binary operators. 175//===----------------------------------------------------------------------===// 176 177static BinaryOperator::Opcode NegateComparison(BinaryOperator::Opcode op) { 178 switch (op) { 179 default: 180 llvm_unreachable("Invalid opcode."); 181 case BO_LT: return BO_GE; 182 case BO_GT: return BO_LE; 183 case BO_LE: return BO_GT; 184 case BO_GE: return BO_LT; 185 case BO_EQ: return BO_NE; 186 case BO_NE: return BO_EQ; 187 } 188} 189 190static BinaryOperator::Opcode ReverseComparison(BinaryOperator::Opcode op) { 191 switch (op) { 192 default: 193 llvm_unreachable("Invalid opcode."); 194 case BO_LT: return BO_GT; 195 case BO_GT: return BO_LT; 196 case BO_LE: return BO_GE; 197 case BO_GE: return BO_LE; 198 case BO_EQ: 199 case BO_NE: 200 return op; 201 } 202} 203 204SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS, 205 BinaryOperator::Opcode op, 206 const llvm::APSInt &RHS, 207 QualType resultTy) { 208 bool isIdempotent = false; 209 210 // Check for a few special cases with known reductions first. 211 switch (op) { 212 default: 213 // We can't reduce this case; just treat it normally. 214 break; 215 case BO_Mul: 216 // a*0 and a*1 217 if (RHS == 0) 218 return makeIntVal(0, resultTy); 219 else if (RHS == 1) 220 isIdempotent = true; 221 break; 222 case BO_Div: 223 // a/0 and a/1 224 if (RHS == 0) 225 // This is also handled elsewhere. 226 return UndefinedVal(); 227 else if (RHS == 1) 228 isIdempotent = true; 229 break; 230 case BO_Rem: 231 // a%0 and a%1 232 if (RHS == 0) 233 // This is also handled elsewhere. 234 return UndefinedVal(); 235 else if (RHS == 1) 236 return makeIntVal(0, resultTy); 237 break; 238 case BO_Add: 239 case BO_Sub: 240 case BO_Shl: 241 case BO_Shr: 242 case BO_Xor: 243 // a+0, a-0, a<<0, a>>0, a^0 244 if (RHS == 0) 245 isIdempotent = true; 246 break; 247 case BO_And: 248 // a&0 and a&(~0) 249 if (RHS == 0) 250 return makeIntVal(0, resultTy); 251 else if (RHS.isAllOnesValue()) 252 isIdempotent = true; 253 break; 254 case BO_Or: 255 // a|0 and a|(~0) 256 if (RHS == 0) 257 isIdempotent = true; 258 else if (RHS.isAllOnesValue()) { 259 const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS); 260 return nonloc::ConcreteInt(Result); 261 } 262 break; 263 } 264 265 // Idempotent ops (like a*1) can still change the type of an expression. 266 // Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the 267 // dirty work. 268 if (isIdempotent) 269 return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy); 270 271 // If we reach this point, the expression cannot be simplified. 272 // Make a SymbolVal for the entire expression, after converting the RHS. 273 const llvm::APSInt *ConvertedRHS = &RHS; 274 if (BinaryOperator::isComparisonOp(op)) { 275 // We're looking for a type big enough to compare the symbolic value 276 // with the given constant. 277 // FIXME: This is an approximation of Sema::UsualArithmeticConversions. 278 ASTContext &Ctx = getContext(); 279 QualType SymbolType = LHS->getType(Ctx); 280 uint64_t ValWidth = RHS.getBitWidth(); 281 uint64_t TypeWidth = Ctx.getTypeSize(SymbolType); 282 283 if (ValWidth < TypeWidth) { 284 // If the value is too small, extend it. 285 ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); 286 } else if (ValWidth == TypeWidth) { 287 // If the value is signed but the symbol is unsigned, do the comparison 288 // in unsigned space. [C99 6.3.1.8] 289 // (For the opposite case, the value is already unsigned.) 290 if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType()) 291 ConvertedRHS = &BasicVals.Convert(SymbolType, RHS); 292 } 293 } else 294 ConvertedRHS = &BasicVals.Convert(resultTy, RHS); 295 296 return makeNonLoc(LHS, op, *ConvertedRHS, resultTy); 297} 298 299SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state, 300 BinaryOperator::Opcode op, 301 NonLoc lhs, NonLoc rhs, 302 QualType resultTy) { 303 NonLoc InputLHS = lhs; 304 NonLoc InputRHS = rhs; 305 306 // Handle trivial case where left-side and right-side are the same. 307 if (lhs == rhs) 308 switch (op) { 309 default: 310 break; 311 case BO_EQ: 312 case BO_LE: 313 case BO_GE: 314 return makeTruthVal(true, resultTy); 315 case BO_LT: 316 case BO_GT: 317 case BO_NE: 318 return makeTruthVal(false, resultTy); 319 case BO_Xor: 320 case BO_Sub: 321 if (resultTy->isIntegralOrEnumerationType()) 322 return makeIntVal(0, resultTy); 323 return evalCastFromNonLoc(makeIntVal(0, /*Unsigned=*/false), resultTy); 324 case BO_Or: 325 case BO_And: 326 return evalCastFromNonLoc(lhs, resultTy); 327 } 328 329 while (1) { 330 switch (lhs.getSubKind()) { 331 default: 332 return makeSymExprValNN(state, op, lhs, rhs, resultTy); 333 case nonloc::LocAsIntegerKind: { 334 Loc lhsL = cast<nonloc::LocAsInteger>(lhs).getLoc(); 335 switch (rhs.getSubKind()) { 336 case nonloc::LocAsIntegerKind: 337 return evalBinOpLL(state, op, lhsL, 338 cast<nonloc::LocAsInteger>(rhs).getLoc(), 339 resultTy); 340 case nonloc::ConcreteIntKind: { 341 // Transform the integer into a location and compare. 342 llvm::APSInt i = cast<nonloc::ConcreteInt>(rhs).getValue(); 343 BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i); 344 return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy); 345 } 346 default: 347 switch (op) { 348 case BO_EQ: 349 return makeTruthVal(false, resultTy); 350 case BO_NE: 351 return makeTruthVal(true, resultTy); 352 default: 353 // This case also handles pointer arithmetic. 354 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 355 } 356 } 357 } 358 case nonloc::ConcreteIntKind: { 359 llvm::APSInt LHSValue = cast<nonloc::ConcreteInt>(lhs).getValue(); 360 361 // If we're dealing with two known constants, just perform the operation. 362 if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) { 363 llvm::APSInt RHSValue = *KnownRHSValue; 364 if (BinaryOperator::isComparisonOp(op)) { 365 // We're looking for a type big enough to compare the two values. 366 // FIXME: This is not correct. char + short will result in a promotion 367 // to int. Unfortunately we have lost types by this point. 368 APSIntType CompareType = std::max(APSIntType(LHSValue), 369 APSIntType(RHSValue)); 370 CompareType.apply(LHSValue); 371 CompareType.apply(RHSValue); 372 } else if (!BinaryOperator::isShiftOp(op)) { 373 APSIntType IntType = BasicVals.getAPSIntType(resultTy); 374 IntType.apply(LHSValue); 375 IntType.apply(RHSValue); 376 } 377 378 const llvm::APSInt *Result = 379 BasicVals.evalAPSInt(op, LHSValue, RHSValue); 380 if (!Result) 381 return UndefinedVal(); 382 383 return nonloc::ConcreteInt(*Result); 384 } 385 386 // Swap the left and right sides and flip the operator if doing so 387 // allows us to better reason about the expression (this is a form 388 // of expression canonicalization). 389 // While we're at it, catch some special cases for non-commutative ops. 390 switch (op) { 391 case BO_LT: 392 case BO_GT: 393 case BO_LE: 394 case BO_GE: 395 op = ReverseComparison(op); 396 // FALL-THROUGH 397 case BO_EQ: 398 case BO_NE: 399 case BO_Add: 400 case BO_Mul: 401 case BO_And: 402 case BO_Xor: 403 case BO_Or: 404 std::swap(lhs, rhs); 405 continue; 406 case BO_Shr: 407 // (~0)>>a 408 if (LHSValue.isAllOnesValue() && LHSValue.isSigned()) 409 return evalCastFromNonLoc(lhs, resultTy); 410 // FALL-THROUGH 411 case BO_Shl: 412 // 0<<a and 0>>a 413 if (LHSValue == 0) 414 return evalCastFromNonLoc(lhs, resultTy); 415 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 416 default: 417 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 418 } 419 } 420 case nonloc::SymbolValKind: { 421 // We only handle LHS as simple symbols or SymIntExprs. 422 SymbolRef Sym = cast<nonloc::SymbolVal>(lhs).getSymbol(); 423 424 // LHS is a symbolic expression. 425 if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) { 426 427 // Is this a logical not? (!x is represented as x == 0.) 428 if (op == BO_EQ && rhs.isZeroConstant()) { 429 // We know how to negate certain expressions. Simplify them here. 430 431 BinaryOperator::Opcode opc = symIntExpr->getOpcode(); 432 switch (opc) { 433 default: 434 // We don't know how to negate this operation. 435 // Just handle it as if it were a normal comparison to 0. 436 break; 437 case BO_LAnd: 438 case BO_LOr: 439 llvm_unreachable("Logical operators handled by branching logic."); 440 case BO_Assign: 441 case BO_MulAssign: 442 case BO_DivAssign: 443 case BO_RemAssign: 444 case BO_AddAssign: 445 case BO_SubAssign: 446 case BO_ShlAssign: 447 case BO_ShrAssign: 448 case BO_AndAssign: 449 case BO_XorAssign: 450 case BO_OrAssign: 451 case BO_Comma: 452 llvm_unreachable("'=' and ',' operators handled by ExprEngine."); 453 case BO_PtrMemD: 454 case BO_PtrMemI: 455 llvm_unreachable("Pointer arithmetic not handled here."); 456 case BO_LT: 457 case BO_GT: 458 case BO_LE: 459 case BO_GE: 460 case BO_EQ: 461 case BO_NE: 462 // Negate the comparison and make a value. 463 opc = NegateComparison(opc); 464 assert(symIntExpr->getType(Context) == resultTy); 465 return makeNonLoc(symIntExpr->getLHS(), opc, 466 symIntExpr->getRHS(), resultTy); 467 } 468 } 469 470 // For now, only handle expressions whose RHS is a constant. 471 if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) { 472 // If both the LHS and the current expression are additive, 473 // fold their constants and try again. 474 if (BinaryOperator::isAdditiveOp(op)) { 475 BinaryOperator::Opcode lop = symIntExpr->getOpcode(); 476 if (BinaryOperator::isAdditiveOp(lop)) { 477 // Convert the two constants to a common type, then combine them. 478 479 // resultTy may not be the best type to convert to, but it's 480 // probably the best choice in expressions with mixed type 481 // (such as x+1U+2LL). The rules for implicit conversions should 482 // choose a reasonable type to preserve the expression, and will 483 // at least match how the value is going to be used. 484 APSIntType IntType = BasicVals.getAPSIntType(resultTy); 485 const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS()); 486 const llvm::APSInt &second = IntType.convert(*RHSValue); 487 488 const llvm::APSInt *newRHS; 489 if (lop == op) 490 newRHS = BasicVals.evalAPSInt(BO_Add, first, second); 491 else 492 newRHS = BasicVals.evalAPSInt(BO_Sub, first, second); 493 494 assert(newRHS && "Invalid operation despite common type!"); 495 rhs = nonloc::ConcreteInt(*newRHS); 496 lhs = nonloc::SymbolVal(symIntExpr->getLHS()); 497 op = lop; 498 continue; 499 } 500 } 501 502 // Otherwise, make a SymIntExpr out of the expression. 503 return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy); 504 } 505 506 507 } else if (isa<SymbolData>(Sym)) { 508 // Does the symbol simplify to a constant? If so, "fold" the constant 509 // by setting 'lhs' to a ConcreteInt and try again. 510 if (const llvm::APSInt *Constant = state->getSymVal(Sym)) { 511 lhs = nonloc::ConcreteInt(*Constant); 512 continue; 513 } 514 515 // Is the RHS a constant? 516 if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) 517 return MakeSymIntVal(Sym, op, *RHSValue, resultTy); 518 } 519 520 // Give up -- this is not a symbolic expression we can handle. 521 return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy); 522 } 523 } 524 } 525} 526 527// FIXME: all this logic will change if/when we have MemRegion::getLocation(). 528SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state, 529 BinaryOperator::Opcode op, 530 Loc lhs, Loc rhs, 531 QualType resultTy) { 532 // Only comparisons and subtractions are valid operations on two pointers. 533 // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15]. 534 // However, if a pointer is casted to an integer, evalBinOpNN may end up 535 // calling this function with another operation (PR7527). We don't attempt to 536 // model this for now, but it could be useful, particularly when the 537 // "location" is actually an integer value that's been passed through a void*. 538 if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub)) 539 return UnknownVal(); 540 541 // Special cases for when both sides are identical. 542 if (lhs == rhs) { 543 switch (op) { 544 default: 545 llvm_unreachable("Unimplemented operation for two identical values"); 546 case BO_Sub: 547 return makeZeroVal(resultTy); 548 case BO_EQ: 549 case BO_LE: 550 case BO_GE: 551 return makeTruthVal(true, resultTy); 552 case BO_NE: 553 case BO_LT: 554 case BO_GT: 555 return makeTruthVal(false, resultTy); 556 } 557 } 558 559 switch (lhs.getSubKind()) { 560 default: 561 llvm_unreachable("Ordering not implemented for this Loc."); 562 563 case loc::GotoLabelKind: 564 // The only thing we know about labels is that they're non-null. 565 if (rhs.isZeroConstant()) { 566 switch (op) { 567 default: 568 break; 569 case BO_Sub: 570 return evalCastFromLoc(lhs, resultTy); 571 case BO_EQ: 572 case BO_LE: 573 case BO_LT: 574 return makeTruthVal(false, resultTy); 575 case BO_NE: 576 case BO_GT: 577 case BO_GE: 578 return makeTruthVal(true, resultTy); 579 } 580 } 581 // There may be two labels for the same location, and a function region may 582 // have the same address as a label at the start of the function (depending 583 // on the ABI). 584 // FIXME: we can probably do a comparison against other MemRegions, though. 585 // FIXME: is there a way to tell if two labels refer to the same location? 586 return UnknownVal(); 587 588 case loc::ConcreteIntKind: { 589 // If one of the operands is a symbol and the other is a constant, 590 // build an expression for use by the constraint manager. 591 if (SymbolRef rSym = rhs.getAsLocSymbol()) { 592 // We can only build expressions with symbols on the left, 593 // so we need a reversible operator. 594 if (!BinaryOperator::isComparisonOp(op)) 595 return UnknownVal(); 596 597 const llvm::APSInt &lVal = cast<loc::ConcreteInt>(lhs).getValue(); 598 return makeNonLoc(rSym, ReverseComparison(op), lVal, resultTy); 599 } 600 601 // If both operands are constants, just perform the operation. 602 if (loc::ConcreteInt *rInt = dyn_cast<loc::ConcreteInt>(&rhs)) { 603 SVal ResultVal = cast<loc::ConcreteInt>(lhs).evalBinOp(BasicVals, op, 604 *rInt); 605 if (Loc *Result = dyn_cast<Loc>(&ResultVal)) 606 return evalCastFromLoc(*Result, resultTy); 607 else 608 return UnknownVal(); 609 } 610 611 // Special case comparisons against NULL. 612 // This must come after the test if the RHS is a symbol, which is used to 613 // build constraints. The address of any non-symbolic region is guaranteed 614 // to be non-NULL, as is any label. 615 assert(isa<loc::MemRegionVal>(rhs) || isa<loc::GotoLabel>(rhs)); 616 if (lhs.isZeroConstant()) { 617 switch (op) { 618 default: 619 break; 620 case BO_EQ: 621 case BO_GT: 622 case BO_GE: 623 return makeTruthVal(false, resultTy); 624 case BO_NE: 625 case BO_LT: 626 case BO_LE: 627 return makeTruthVal(true, resultTy); 628 } 629 } 630 631 // Comparing an arbitrary integer to a region or label address is 632 // completely unknowable. 633 return UnknownVal(); 634 } 635 case loc::MemRegionKind: { 636 if (loc::ConcreteInt *rInt = dyn_cast<loc::ConcreteInt>(&rhs)) { 637 // If one of the operands is a symbol and the other is a constant, 638 // build an expression for use by the constraint manager. 639 if (SymbolRef lSym = lhs.getAsLocSymbol()) 640 return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy); 641 642 // Special case comparisons to NULL. 643 // This must come after the test if the LHS is a symbol, which is used to 644 // build constraints. The address of any non-symbolic region is guaranteed 645 // to be non-NULL. 646 if (rInt->isZeroConstant()) { 647 switch (op) { 648 default: 649 break; 650 case BO_Sub: 651 return evalCastFromLoc(lhs, resultTy); 652 case BO_EQ: 653 case BO_LT: 654 case BO_LE: 655 return makeTruthVal(false, resultTy); 656 case BO_NE: 657 case BO_GT: 658 case BO_GE: 659 return makeTruthVal(true, resultTy); 660 } 661 } 662 663 // Comparing a region to an arbitrary integer is completely unknowable. 664 return UnknownVal(); 665 } 666 667 // Get both values as regions, if possible. 668 const MemRegion *LeftMR = lhs.getAsRegion(); 669 assert(LeftMR && "MemRegionKind SVal doesn't have a region!"); 670 671 const MemRegion *RightMR = rhs.getAsRegion(); 672 if (!RightMR) 673 // The RHS is probably a label, which in theory could address a region. 674 // FIXME: we can probably make a more useful statement about non-code 675 // regions, though. 676 return UnknownVal(); 677 678 const MemSpaceRegion *LeftMS = LeftMR->getMemorySpace(); 679 const MemSpaceRegion *RightMS = RightMR->getMemorySpace(); 680 const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion(); 681 const MemRegion *LeftBase = LeftMR->getBaseRegion(); 682 const MemRegion *RightBase = RightMR->getBaseRegion(); 683 684 // If the two regions are from different known memory spaces they cannot be 685 // equal. Also, assume that no symbolic region (whose memory space is 686 // unknown) is on the stack. 687 if (LeftMS != RightMS && 688 ((LeftMS != UnknownMS && RightMS != UnknownMS) || 689 (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) { 690 switch (op) { 691 default: 692 return UnknownVal(); 693 case BO_EQ: 694 return makeTruthVal(false, resultTy); 695 case BO_NE: 696 return makeTruthVal(true, resultTy); 697 } 698 } 699 700 // If both values wrap regions, see if they're from different base regions. 701 // Note, heap base symbolic regions are assumed to not alias with 702 // each other; for example, we assume that malloc returns different address 703 // on each invocation. 704 if (LeftBase != RightBase && 705 ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) || 706 (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){ 707 switch (op) { 708 default: 709 return UnknownVal(); 710 case BO_EQ: 711 return makeTruthVal(false, resultTy); 712 case BO_NE: 713 return makeTruthVal(true, resultTy); 714 } 715 } 716 717 // FIXME: If/when there is a getAsRawOffset() for FieldRegions, this 718 // ElementRegion path and the FieldRegion path below should be unified. 719 if (const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR)) { 720 // First see if the right region is also an ElementRegion. 721 const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR); 722 if (!RightER) 723 return UnknownVal(); 724 725 // Next, see if the two ERs have the same super-region and matching types. 726 // FIXME: This should do something useful even if the types don't match, 727 // though if both indexes are constant the RegionRawOffset path will 728 // give the correct answer. 729 if (LeftER->getSuperRegion() == RightER->getSuperRegion() && 730 LeftER->getElementType() == RightER->getElementType()) { 731 // Get the left index and cast it to the correct type. 732 // If the index is unknown or undefined, bail out here. 733 SVal LeftIndexVal = LeftER->getIndex(); 734 NonLoc *LeftIndex = dyn_cast<NonLoc>(&LeftIndexVal); 735 if (!LeftIndex) 736 return UnknownVal(); 737 LeftIndexVal = evalCastFromNonLoc(*LeftIndex, resultTy); 738 LeftIndex = dyn_cast<NonLoc>(&LeftIndexVal); 739 if (!LeftIndex) 740 return UnknownVal(); 741 742 // Do the same for the right index. 743 SVal RightIndexVal = RightER->getIndex(); 744 NonLoc *RightIndex = dyn_cast<NonLoc>(&RightIndexVal); 745 if (!RightIndex) 746 return UnknownVal(); 747 RightIndexVal = evalCastFromNonLoc(*RightIndex, resultTy); 748 RightIndex = dyn_cast<NonLoc>(&RightIndexVal); 749 if (!RightIndex) 750 return UnknownVal(); 751 752 // Actually perform the operation. 753 // evalBinOpNN expects the two indexes to already be the right type. 754 return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy); 755 } 756 757 // If the element indexes aren't comparable, see if the raw offsets are. 758 RegionRawOffset LeftOffset = LeftER->getAsArrayOffset(); 759 RegionRawOffset RightOffset = RightER->getAsArrayOffset(); 760 761 if (LeftOffset.getRegion() != NULL && 762 LeftOffset.getRegion() == RightOffset.getRegion()) { 763 CharUnits left = LeftOffset.getOffset(); 764 CharUnits right = RightOffset.getOffset(); 765 766 switch (op) { 767 default: 768 return UnknownVal(); 769 case BO_LT: 770 return makeTruthVal(left < right, resultTy); 771 case BO_GT: 772 return makeTruthVal(left > right, resultTy); 773 case BO_LE: 774 return makeTruthVal(left <= right, resultTy); 775 case BO_GE: 776 return makeTruthVal(left >= right, resultTy); 777 case BO_EQ: 778 return makeTruthVal(left == right, resultTy); 779 case BO_NE: 780 return makeTruthVal(left != right, resultTy); 781 } 782 } 783 784 // If we get here, we have no way of comparing the ElementRegions. 785 return UnknownVal(); 786 } 787 788 // See if both regions are fields of the same structure. 789 // FIXME: This doesn't handle nesting, inheritance, or Objective-C ivars. 790 if (const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR)) { 791 // Only comparisons are meaningful here! 792 if (!BinaryOperator::isComparisonOp(op)) 793 return UnknownVal(); 794 795 // First see if the right region is also a FieldRegion. 796 const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR); 797 if (!RightFR) 798 return UnknownVal(); 799 800 // Next, see if the two FRs have the same super-region. 801 // FIXME: This doesn't handle casts yet, and simply stripping the casts 802 // doesn't help. 803 if (LeftFR->getSuperRegion() != RightFR->getSuperRegion()) 804 return UnknownVal(); 805 806 const FieldDecl *LeftFD = LeftFR->getDecl(); 807 const FieldDecl *RightFD = RightFR->getDecl(); 808 const RecordDecl *RD = LeftFD->getParent(); 809 810 // Make sure the two FRs are from the same kind of record. Just in case! 811 // FIXME: This is probably where inheritance would be a problem. 812 if (RD != RightFD->getParent()) 813 return UnknownVal(); 814 815 // We know for sure that the two fields are not the same, since that 816 // would have given us the same SVal. 817 if (op == BO_EQ) 818 return makeTruthVal(false, resultTy); 819 if (op == BO_NE) 820 return makeTruthVal(true, resultTy); 821 822 // Iterate through the fields and see which one comes first. 823 // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field 824 // members and the units in which bit-fields reside have addresses that 825 // increase in the order in which they are declared." 826 bool leftFirst = (op == BO_LT || op == BO_LE); 827 for (RecordDecl::field_iterator I = RD->field_begin(), 828 E = RD->field_end(); I!=E; ++I) { 829 if (*I == LeftFD) 830 return makeTruthVal(leftFirst, resultTy); 831 if (*I == RightFD) 832 return makeTruthVal(!leftFirst, resultTy); 833 } 834 835 llvm_unreachable("Fields not found in parent record's definition"); 836 } 837 838 // If we get here, we have no way of comparing the regions. 839 return UnknownVal(); 840 } 841 } 842} 843 844SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state, 845 BinaryOperator::Opcode op, 846 Loc lhs, NonLoc rhs, QualType resultTy) { 847 848 // Special case: rhs is a zero constant. 849 if (rhs.isZeroConstant()) 850 return lhs; 851 852 // Special case: 'rhs' is an integer that has the same width as a pointer and 853 // we are using the integer location in a comparison. Normally this cannot be 854 // triggered, but transfer functions like those for OSCommpareAndSwapBarrier32 855 // can generate comparisons that trigger this code. 856 // FIXME: Are all locations guaranteed to have pointer width? 857 if (BinaryOperator::isComparisonOp(op)) { 858 if (nonloc::ConcreteInt *rhsInt = dyn_cast<nonloc::ConcreteInt>(&rhs)) { 859 const llvm::APSInt *x = &rhsInt->getValue(); 860 ASTContext &ctx = Context; 861 if (ctx.getTypeSize(ctx.VoidPtrTy) == x->getBitWidth()) { 862 // Convert the signedness of the integer (if necessary). 863 if (x->isSigned()) 864 x = &getBasicValueFactory().getValue(*x, true); 865 866 return evalBinOpLL(state, op, lhs, loc::ConcreteInt(*x), resultTy); 867 } 868 } 869 return UnknownVal(); 870 } 871 872 // We are dealing with pointer arithmetic. 873 874 // Handle pointer arithmetic on constant values. 875 if (nonloc::ConcreteInt *rhsInt = dyn_cast<nonloc::ConcreteInt>(&rhs)) { 876 if (loc::ConcreteInt *lhsInt = dyn_cast<loc::ConcreteInt>(&lhs)) { 877 const llvm::APSInt &leftI = lhsInt->getValue(); 878 assert(leftI.isUnsigned()); 879 llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true); 880 881 // Convert the bitwidth of rightI. This should deal with overflow 882 // since we are dealing with concrete values. 883 rightI = rightI.extOrTrunc(leftI.getBitWidth()); 884 885 // Offset the increment by the pointer size. 886 llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true); 887 rightI *= Multiplicand; 888 889 // Compute the adjusted pointer. 890 switch (op) { 891 case BO_Add: 892 rightI = leftI + rightI; 893 break; 894 case BO_Sub: 895 rightI = leftI - rightI; 896 break; 897 default: 898 llvm_unreachable("Invalid pointer arithmetic operation"); 899 } 900 return loc::ConcreteInt(getBasicValueFactory().getValue(rightI)); 901 } 902 } 903 904 // Handle cases where 'lhs' is a region. 905 if (const MemRegion *region = lhs.getAsRegion()) { 906 rhs = cast<NonLoc>(convertToArrayIndex(rhs)); 907 SVal index = UnknownVal(); 908 const MemRegion *superR = 0; 909 QualType elementType; 910 911 if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) { 912 assert(op == BO_Add || op == BO_Sub); 913 index = evalBinOpNN(state, op, elemReg->getIndex(), rhs, 914 getArrayIndexType()); 915 superR = elemReg->getSuperRegion(); 916 elementType = elemReg->getElementType(); 917 } 918 else if (isa<SubRegion>(region)) { 919 superR = region; 920 index = rhs; 921 if (resultTy->isAnyPointerType()) 922 elementType = resultTy->getPointeeType(); 923 } 924 925 if (NonLoc *indexV = dyn_cast<NonLoc>(&index)) { 926 return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV, 927 superR, getContext())); 928 } 929 } 930 return UnknownVal(); 931} 932 933const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state, 934 SVal V) { 935 if (V.isUnknownOrUndef()) 936 return NULL; 937 938 if (loc::ConcreteInt* X = dyn_cast<loc::ConcreteInt>(&V)) 939 return &X->getValue(); 940 941 if (nonloc::ConcreteInt* X = dyn_cast<nonloc::ConcreteInt>(&V)) 942 return &X->getValue(); 943 944 if (SymbolRef Sym = V.getAsSymbol()) 945 return state->getSymVal(Sym); 946 947 // FIXME: Add support for SymExprs. 948 return NULL; 949} 950