1437 lines · cpp
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-exception6//7//===----------------------------------------------------------------------===//8//9// This file defines SimpleSValBuilder, a basic implementation of SValBuilder.10//11//===----------------------------------------------------------------------===//12 13#include "clang/StaticAnalyzer/Core/PathSensitive/APSIntPtr.h"14#include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h"15#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"16#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"17#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"18#include "clang/StaticAnalyzer/Core/PathSensitive/SValVisitor.h"19#include <optional>20 21using namespace clang;22using namespace ento;23 24namespace {25class SimpleSValBuilder : public SValBuilder {26 27 // Query the constraint manager whether the SVal has only one possible28 // (integer) value. If that is the case, the value is returned. Otherwise,29 // returns NULL.30 // This is an implementation detail. Checkers should use `getKnownValue()`31 // instead.32 static const llvm::APSInt *getConstValue(ProgramStateRef state, SVal V);33 34 // Helper function that returns the value stored in a nonloc::ConcreteInt or35 // loc::ConcreteInt.36 static const llvm::APSInt *getConcreteValue(SVal V);37 38 // With one `simplifySValOnce` call, a compound symbols might collapse to39 // simpler symbol tree that is still possible to further simplify. Thus, we40 // do the simplification on a new symbol tree until we reach the simplest41 // form, i.e. the fixpoint.42 // Consider the following symbol `(b * b) * b * b` which has this tree:43 // *44 // / \45 // * b46 // / \47 // / b48 // (b * b)49 // Now, if the `b * b == 1` new constraint is added then during the first50 // iteration we have the following transformations:51 // * *52 // / \ / \53 // * b --> b b54 // / \55 // / b56 // 157 // We need another iteration to reach the final result `1`.58 SVal simplifyUntilFixpoint(ProgramStateRef State, SVal Val);59 60 // Recursively descends into symbolic expressions and replaces symbols61 // with their known values (in the sense of the getConstValue() method).62 // We traverse the symbol tree and query the constraint values for the63 // sub-trees and if a value is a constant we do the constant folding.64 SVal simplifySValOnce(ProgramStateRef State, SVal V);65 66public:67 SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context,68 ProgramStateManager &stateMgr)69 : SValBuilder(alloc, context, stateMgr) {}70 ~SimpleSValBuilder() override {}71 72 SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op,73 NonLoc lhs, NonLoc rhs, QualType resultTy) override;74 SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op,75 Loc lhs, Loc rhs, QualType resultTy) override;76 SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op,77 Loc lhs, NonLoc rhs, QualType resultTy) override;78 79 /// Evaluates a given SVal by recursively evaluating and80 /// simplifying the children SVals. If the SVal has only one possible81 /// (integer) value, that value is returned. Otherwise, returns NULL.82 const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override;83 84 /// Evaluates a given SVal by recursively evaluating and simplifying the85 /// children SVals, then returns its minimal possible (integer) value. If the86 /// constraint manager cannot provide a meaningful answer, this returns NULL.87 const llvm::APSInt *getMinValue(ProgramStateRef state, SVal V) override;88 89 /// Evaluates a given SVal by recursively evaluating and simplifying the90 /// children SVals, then returns its maximal possible (integer) value. If the91 /// constraint manager cannot provide a meaningful answer, this returns NULL.92 const llvm::APSInt *getMaxValue(ProgramStateRef state, SVal V) override;93 94 SVal simplifySVal(ProgramStateRef State, SVal V) override;95 96 SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op,97 const llvm::APSInt &RHS, QualType resultTy);98};99} // end anonymous namespace100 101SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc,102 ASTContext &context,103 ProgramStateManager &stateMgr) {104 return new SimpleSValBuilder(alloc, context, stateMgr);105}106 107// Checks if the negation the value and flipping sign preserve108// the semantics on the operation in the resultType109static bool isNegationValuePreserving(const llvm::APSInt &Value,110 APSIntType ResultType) {111 const unsigned ValueBits = Value.getSignificantBits();112 if (ValueBits == ResultType.getBitWidth()) {113 // The value is the lowest negative value that is representable114 // in signed integer with bitWith of result type. The115 // negation is representable if resultType is unsigned.116 return ResultType.isUnsigned();117 }118 119 // If resultType bitWith is higher that number of bits required120 // to represent RHS, the sign flip produce same value.121 return ValueBits < ResultType.getBitWidth();122}123 124//===----------------------------------------------------------------------===//125// Transfer function for binary operators.126//===----------------------------------------------------------------------===//127 128SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,129 BinaryOperator::Opcode op,130 const llvm::APSInt &RHS,131 QualType resultTy) {132 bool isIdempotent = false;133 134 // Check for a few special cases with known reductions first.135 switch (op) {136 default:137 // We can't reduce this case; just treat it normally.138 break;139 case BO_Mul:140 // a*0 and a*1141 if (RHS == 0)142 return makeIntVal(0, resultTy);143 else if (RHS == 1)144 isIdempotent = true;145 break;146 case BO_Div:147 // a/0 and a/1148 if (RHS == 0)149 // This is also handled elsewhere.150 return UndefinedVal();151 else if (RHS == 1)152 isIdempotent = true;153 break;154 case BO_Rem:155 // a%0 and a%1156 if (RHS == 0)157 // This is also handled elsewhere.158 return UndefinedVal();159 else if (RHS == 1)160 return makeIntVal(0, resultTy);161 break;162 case BO_Add:163 case BO_Sub:164 case BO_Shl:165 case BO_Shr:166 case BO_Xor:167 // a+0, a-0, a<<0, a>>0, a^0168 if (RHS == 0)169 isIdempotent = true;170 break;171 case BO_And:172 // a&0 and a&(~0)173 if (RHS == 0)174 return makeIntVal(0, resultTy);175 else if (RHS.isAllOnes())176 isIdempotent = true;177 break;178 case BO_Or:179 // a|0 and a|(~0)180 if (RHS == 0)181 isIdempotent = true;182 else if (RHS.isAllOnes()) {183 return nonloc::ConcreteInt(BasicVals.Convert(resultTy, RHS));184 }185 break;186 }187 188 // Idempotent ops (like a*1) can still change the type of an expression.189 // Wrap the LHS up in a NonLoc again and let evalCast do the190 // dirty work.191 if (isIdempotent)192 return evalCast(nonloc::SymbolVal(LHS), resultTy, QualType{});193 194 // If we reach this point, the expression cannot be simplified.195 // Make a SymbolVal for the entire expression, after converting the RHS.196 std::optional<APSIntPtr> ConvertedRHS = BasicVals.getValue(RHS);197 if (BinaryOperator::isComparisonOp(op)) {198 // We're looking for a type big enough to compare the symbolic value199 // with the given constant.200 // FIXME: This is an approximation of Sema::UsualArithmeticConversions.201 ASTContext &Ctx = getContext();202 QualType SymbolType = LHS->getType();203 uint64_t ValWidth = RHS.getBitWidth();204 uint64_t TypeWidth = Ctx.getTypeSize(SymbolType);205 206 if (ValWidth < TypeWidth) {207 // If the value is too small, extend it.208 ConvertedRHS = BasicVals.Convert(SymbolType, RHS);209 } else if (ValWidth == TypeWidth) {210 // If the value is signed but the symbol is unsigned, do the comparison211 // in unsigned space. [C99 6.3.1.8]212 // (For the opposite case, the value is already unsigned.)213 if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType())214 ConvertedRHS = BasicVals.Convert(SymbolType, RHS);215 }216 } else if (BinaryOperator::isAdditiveOp(op) && RHS.isNegative()) {217 // Change a+(-N) into a-N, and a-(-N) into a+N218 // Adjust addition/subtraction of negative value, to219 // subtraction/addition of the negated value.220 APSIntType resultIntTy = BasicVals.getAPSIntType(resultTy);221 if (isNegationValuePreserving(RHS, resultIntTy)) {222 ConvertedRHS = BasicVals.getValue(-resultIntTy.convert(RHS));223 op = (op == BO_Add) ? BO_Sub : BO_Add;224 } else {225 ConvertedRHS = BasicVals.Convert(resultTy, RHS);226 }227 } else228 ConvertedRHS = BasicVals.Convert(resultTy, RHS);229 230 return makeNonLoc(LHS, op, *ConvertedRHS, resultTy);231}232 233// See if Sym is known to be a relation Rel with Bound.234static bool isInRelation(BinaryOperator::Opcode Rel, SymbolRef Sym,235 llvm::APSInt Bound, ProgramStateRef State) {236 SValBuilder &SVB = State->getStateManager().getSValBuilder();237 BasicValueFactory &BV = SVB.getBasicValueFactory();238 SVal Result = SVB.evalBinOpNN(State, Rel, nonloc::SymbolVal(Sym),239 nonloc::ConcreteInt(BV.getValue(Bound)),240 SVB.getConditionType());241 if (auto DV = Result.getAs<DefinedSVal>()) {242 return !State->assume(*DV, false);243 }244 return false;245}246 247// See if Sym is known to be within [min/4, max/4], where min and max248// are the bounds of the symbol's integral type. With such symbols,249// some manipulations can be performed without the risk of overflow.250// assume() doesn't cause infinite recursion because we should be dealing251// with simpler symbols on every recursive call.252static bool isWithinConstantOverflowBounds(SymbolRef Sym,253 ProgramStateRef State) {254 SValBuilder &SVB = State->getStateManager().getSValBuilder();255 BasicValueFactory &BV = SVB.getBasicValueFactory();256 257 QualType T = Sym->getType();258 assert(T->isSignedIntegerOrEnumerationType() &&259 "This only works with signed integers!");260 APSIntType AT = BV.getAPSIntType(T);261 262 llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max;263 return isInRelation(BO_LE, Sym, Max, State) &&264 isInRelation(BO_GE, Sym, Min, State);265}266 267// Same for the concrete integers: see if I is within [min/4, max/4].268static bool isWithinConstantOverflowBounds(llvm::APSInt I) {269 APSIntType AT(I);270 assert(!AT.isUnsigned() &&271 "This only works with signed integers!");272 273 llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4);274 return (I <= Max) && (I >= -Max);275}276 277static std::pair<SymbolRef, APSIntPtr> decomposeSymbol(SymbolRef Sym,278 BasicValueFactory &BV) {279 if (const auto *SymInt = dyn_cast<SymIntExpr>(Sym))280 if (BinaryOperator::isAdditiveOp(SymInt->getOpcode()))281 return std::make_pair(SymInt->getLHS(),282 (SymInt->getOpcode() == BO_Add)283 ? BV.getValue(SymInt->getRHS())284 : BV.getValue(-SymInt->getRHS()));285 286 // Fail to decompose: "reduce" the problem to the "$x + 0" case.287 return std::make_pair(Sym, BV.getValue(0, Sym->getType()));288}289 290// Simplify "(LSym + LInt) Op (RSym + RInt)" assuming all values are of the291// same signed integral type and no overflows occur (which should be checked292// by the caller).293static NonLoc doRearrangeUnchecked(ProgramStateRef State,294 BinaryOperator::Opcode Op,295 SymbolRef LSym, llvm::APSInt LInt,296 SymbolRef RSym, llvm::APSInt RInt) {297 SValBuilder &SVB = State->getStateManager().getSValBuilder();298 BasicValueFactory &BV = SVB.getBasicValueFactory();299 SymbolManager &SymMgr = SVB.getSymbolManager();300 301 QualType SymTy = LSym->getType();302 assert(SymTy == RSym->getType() &&303 "Symbols are not of the same type!");304 assert(APSIntType(LInt) == BV.getAPSIntType(SymTy) &&305 "Integers are not of the same type as symbols!");306 assert(APSIntType(RInt) == BV.getAPSIntType(SymTy) &&307 "Integers are not of the same type as symbols!");308 309 QualType ResultTy;310 if (BinaryOperator::isComparisonOp(Op))311 ResultTy = SVB.getConditionType();312 else if (BinaryOperator::isAdditiveOp(Op))313 ResultTy = SymTy;314 else315 llvm_unreachable("Operation not suitable for unchecked rearrangement!");316 317 if (LSym == RSym)318 return SVB319 .evalBinOpNN(State, Op, nonloc::ConcreteInt(BV.getValue(LInt)),320 nonloc::ConcreteInt(BV.getValue(RInt)), ResultTy)321 .castAs<NonLoc>();322 323 SymbolRef ResultSym = nullptr;324 BinaryOperator::Opcode ResultOp;325 llvm::APSInt ResultInt;326 if (BinaryOperator::isComparisonOp(Op)) {327 // Prefer comparing to a non-negative number.328 // FIXME: Maybe it'd be better to have consistency in329 // "$x - $y" vs. "$y - $x" because those are solver's keys.330 if (LInt > RInt) {331 ResultSym = SymMgr.acquire<SymSymExpr>(RSym, BO_Sub, LSym, SymTy);332 ResultOp = BinaryOperator::reverseComparisonOp(Op);333 ResultInt = LInt - RInt; // Opposite order!334 } else {335 ResultSym = SymMgr.acquire<SymSymExpr>(LSym, BO_Sub, RSym, SymTy);336 ResultOp = Op;337 ResultInt = RInt - LInt; // Opposite order!338 }339 } else {340 ResultSym = SymMgr.acquire<SymSymExpr>(LSym, Op, RSym, SymTy);341 ResultInt = (Op == BO_Add) ? (LInt + RInt) : (LInt - RInt);342 ResultOp = BO_Add;343 // Bring back the cosmetic difference.344 if (ResultInt < 0) {345 ResultInt = -ResultInt;346 ResultOp = BO_Sub;347 } else if (ResultInt == 0) {348 // Shortcut: Simplify "$x + 0" to "$x".349 return nonloc::SymbolVal(ResultSym);350 }351 }352 APSIntPtr PersistentResultInt = BV.getValue(ResultInt);353 return nonloc::SymbolVal(SymMgr.acquire<SymIntExpr>(354 ResultSym, ResultOp, PersistentResultInt, ResultTy));355}356 357// Rearrange if symbol type matches the result type and if the operator is a358// comparison operator, both symbol and constant must be within constant359// overflow bounds.360static bool shouldRearrange(ProgramStateRef State, BinaryOperator::Opcode Op,361 SymbolRef Sym, llvm::APSInt Int, QualType Ty) {362 return Sym->getType() == Ty &&363 (!BinaryOperator::isComparisonOp(Op) ||364 (isWithinConstantOverflowBounds(Sym, State) &&365 isWithinConstantOverflowBounds(Int)));366}367 368static std::optional<NonLoc> tryRearrange(ProgramStateRef State,369 BinaryOperator::Opcode Op, NonLoc Lhs,370 NonLoc Rhs, QualType ResultTy) {371 ProgramStateManager &StateMgr = State->getStateManager();372 SValBuilder &SVB = StateMgr.getSValBuilder();373 374 // We expect everything to be of the same type - this type.375 QualType SingleTy;376 377 // FIXME: After putting complexity threshold to the symbols we can always378 // rearrange additive operations but rearrange comparisons only if379 // option is set.380 if (!SVB.getAnalyzerOptions().ShouldAggressivelySimplifyBinaryOperation)381 return std::nullopt;382 383 SymbolRef LSym = Lhs.getAsSymbol();384 if (!LSym)385 return std::nullopt;386 387 if (BinaryOperator::isComparisonOp(Op)) {388 SingleTy = LSym->getType();389 if (ResultTy != SVB.getConditionType())390 return std::nullopt;391 // Initialize SingleTy later with a symbol's type.392 } else if (BinaryOperator::isAdditiveOp(Op)) {393 SingleTy = ResultTy;394 if (LSym->getType() != SingleTy)395 return std::nullopt;396 } else {397 // Don't rearrange other operations.398 return std::nullopt;399 }400 401 assert(!SingleTy.isNull() && "We should have figured out the type by now!");402 403 // Rearrange signed symbolic expressions only404 if (!SingleTy->isSignedIntegerOrEnumerationType())405 return std::nullopt;406 407 SymbolRef RSym = Rhs.getAsSymbol();408 if (!RSym || RSym->getType() != SingleTy)409 return std::nullopt;410 411 BasicValueFactory &BV = State->getBasicVals();412 llvm::APSInt LInt, RInt;413 std::tie(LSym, LInt) = decomposeSymbol(LSym, BV);414 std::tie(RSym, RInt) = decomposeSymbol(RSym, BV);415 if (!shouldRearrange(State, Op, LSym, LInt, SingleTy) ||416 !shouldRearrange(State, Op, RSym, RInt, SingleTy))417 return std::nullopt;418 419 // We know that no overflows can occur anymore.420 return doRearrangeUnchecked(State, Op, LSym, LInt, RSym, RInt);421}422 423SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,424 BinaryOperator::Opcode op,425 NonLoc lhs, NonLoc rhs,426 QualType resultTy) {427 NonLoc InputLHS = lhs;428 NonLoc InputRHS = rhs;429 430 // Constraints may have changed since the creation of a bound SVal. Check if431 // the values can be simplified based on those new constraints.432 SVal simplifiedLhs = simplifySVal(state, lhs);433 SVal simplifiedRhs = simplifySVal(state, rhs);434 if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>())435 lhs = *simplifiedLhsAsNonLoc;436 if (auto simplifiedRhsAsNonLoc = simplifiedRhs.getAs<NonLoc>())437 rhs = *simplifiedRhsAsNonLoc;438 439 // Handle trivial case where left-side and right-side are the same.440 if (lhs == rhs)441 switch (op) {442 default:443 break;444 case BO_EQ:445 case BO_LE:446 case BO_GE:447 return makeTruthVal(true, resultTy);448 case BO_LT:449 case BO_GT:450 case BO_NE:451 return makeTruthVal(false, resultTy);452 case BO_Xor:453 case BO_Sub:454 if (resultTy->isIntegralOrEnumerationType())455 return makeIntVal(0, resultTy);456 return evalCast(makeIntVal(0, /*isUnsigned=*/false), resultTy,457 QualType{});458 case BO_Or:459 case BO_And:460 return evalCast(lhs, resultTy, QualType{});461 }462 463 while (true) {464 switch (lhs.getKind()) {465 default:466 return makeSymExprValNN(op, lhs, rhs, resultTy);467 case nonloc::PointerToMemberKind: {468 assert(rhs.getKind() == nonloc::PointerToMemberKind &&469 "Both SVals should have pointer-to-member-type");470 auto LPTM = lhs.castAs<nonloc::PointerToMember>(),471 RPTM = rhs.castAs<nonloc::PointerToMember>();472 auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData();473 switch (op) {474 case BO_EQ:475 return makeTruthVal(LPTMD == RPTMD, resultTy);476 case BO_NE:477 return makeTruthVal(LPTMD != RPTMD, resultTy);478 default:479 return UnknownVal();480 }481 }482 case nonloc::LocAsIntegerKind: {483 Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc();484 switch (rhs.getKind()) {485 case nonloc::LocAsIntegerKind:486 // FIXME: at the moment the implementation487 // of modeling "pointers as integers" is not complete.488 if (!BinaryOperator::isComparisonOp(op))489 return UnknownVal();490 return evalBinOpLL(state, op, lhsL,491 rhs.castAs<nonloc::LocAsInteger>().getLoc(),492 resultTy);493 case nonloc::ConcreteIntKind: {494 // FIXME: at the moment the implementation495 // of modeling "pointers as integers" is not complete.496 if (!BinaryOperator::isComparisonOp(op))497 return UnknownVal();498 // Transform the integer into a location and compare.499 // FIXME: This only makes sense for comparisons. If we want to, say,500 // add 1 to a LocAsInteger, we'd better unpack the Loc and add to it,501 // then pack it back into a LocAsInteger.502 llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue();503 // If the region has a symbolic base, pay attention to the type; it504 // might be coming from a non-default address space. For non-symbolic505 // regions it doesn't matter that much because such comparisons would506 // most likely evaluate to concrete false anyway. FIXME: We might507 // still need to handle the non-comparison case.508 if (SymbolRef lSym = lhs.getAsLocSymbol(true))509 BasicVals.getAPSIntType(lSym->getType()).apply(i);510 else511 BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i);512 return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy);513 }514 default:515 switch (op) {516 case BO_EQ:517 return makeTruthVal(false, resultTy);518 case BO_NE:519 return makeTruthVal(true, resultTy);520 default:521 // This case also handles pointer arithmetic.522 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);523 }524 }525 }526 case nonloc::ConcreteIntKind: {527 llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue();528 529 // If we're dealing with two known constants, just perform the operation.530 if (const llvm::APSInt *KnownRHSValue = getConstValue(state, rhs)) {531 llvm::APSInt RHSValue = *KnownRHSValue;532 if (BinaryOperator::isComparisonOp(op)) {533 // We're looking for a type big enough to compare the two values.534 // FIXME: This is not correct. char + short will result in a promotion535 // to int. Unfortunately we have lost types by this point.536 APSIntType CompareType = std::max(APSIntType(LHSValue),537 APSIntType(RHSValue));538 CompareType.apply(LHSValue);539 CompareType.apply(RHSValue);540 } else if (!BinaryOperator::isShiftOp(op)) {541 APSIntType IntType = BasicVals.getAPSIntType(resultTy);542 IntType.apply(LHSValue);543 IntType.apply(RHSValue);544 }545 546 std::optional<APSIntPtr> Result =547 BasicVals.evalAPSInt(op, LHSValue, RHSValue);548 if (!Result) {549 if (op == BO_Shl || op == BO_Shr) {550 // FIXME: At this point the constant folding claims that the result551 // of a bitwise shift is undefined. However, constant folding552 // relies on the inaccurate type information that is stored in the553 // bit size of APSInt objects, and if we reached this point, then554 // the checker core.BitwiseShift already determined that the shift555 // is valid (in a PreStmt callback, by querying the real type from556 // the AST node).557 // To avoid embarrassing false positives, let's just say that we558 // don't know anything about the result of the shift.559 return UnknownVal();560 }561 return UndefinedVal();562 }563 564 return nonloc::ConcreteInt(*Result);565 }566 567 // Swap the left and right sides and flip the operator if doing so568 // allows us to better reason about the expression (this is a form569 // of expression canonicalization).570 // While we're at it, catch some special cases for non-commutative ops.571 switch (op) {572 case BO_LT:573 case BO_GT:574 case BO_LE:575 case BO_GE:576 op = BinaryOperator::reverseComparisonOp(op);577 [[fallthrough]];578 case BO_EQ:579 case BO_NE:580 case BO_Add:581 case BO_Mul:582 case BO_And:583 case BO_Xor:584 case BO_Or:585 std::swap(lhs, rhs);586 continue;587 case BO_Shr:588 // (~0)>>a589 if (LHSValue.isAllOnes() && LHSValue.isSigned())590 return evalCast(lhs, resultTy, QualType{});591 [[fallthrough]];592 case BO_Shl:593 // 0<<a and 0>>a594 if (LHSValue == 0)595 return evalCast(lhs, resultTy, QualType{});596 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);597 case BO_Div:598 // 0 / x == 0599 case BO_Rem:600 // 0 % x == 0601 if (LHSValue == 0)602 return makeZeroVal(resultTy);603 [[fallthrough]];604 default:605 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);606 }607 }608 case nonloc::SymbolValKind: {609 // We only handle LHS as simple symbols or SymIntExprs.610 SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol();611 612 // LHS is a symbolic expression.613 if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) {614 615 // Is this a logical not? (!x is represented as x == 0.)616 if (op == BO_EQ && rhs.isZeroConstant()) {617 // We know how to negate certain expressions. Simplify them here.618 619 BinaryOperator::Opcode opc = symIntExpr->getOpcode();620 switch (opc) {621 default:622 // We don't know how to negate this operation.623 // Just handle it as if it were a normal comparison to 0.624 break;625 case BO_LAnd:626 case BO_LOr:627 llvm_unreachable("Logical operators handled by branching logic.");628 case BO_Assign:629 case BO_MulAssign:630 case BO_DivAssign:631 case BO_RemAssign:632 case BO_AddAssign:633 case BO_SubAssign:634 case BO_ShlAssign:635 case BO_ShrAssign:636 case BO_AndAssign:637 case BO_XorAssign:638 case BO_OrAssign:639 case BO_Comma:640 llvm_unreachable("'=' and ',' operators handled by ExprEngine.");641 case BO_PtrMemD:642 case BO_PtrMemI:643 llvm_unreachable("Pointer arithmetic not handled here.");644 case BO_LT:645 case BO_GT:646 case BO_LE:647 case BO_GE:648 case BO_EQ:649 case BO_NE:650 assert(resultTy->isBooleanType() ||651 resultTy == getConditionType());652 assert(symIntExpr->getType()->isBooleanType() ||653 getContext().hasSameUnqualifiedType(symIntExpr->getType(),654 getConditionType()));655 // Negate the comparison and make a value.656 opc = BinaryOperator::negateComparisonOp(opc);657 return makeNonLoc(symIntExpr->getLHS(), opc,658 symIntExpr->getRHS(), resultTy);659 }660 }661 662 // For now, only handle expressions whose RHS is a constant.663 if (const llvm::APSInt *RHSValue = getConstValue(state, rhs)) {664 // If both the LHS and the current expression are additive,665 // fold their constants and try again.666 if (BinaryOperator::isAdditiveOp(op)) {667 BinaryOperator::Opcode lop = symIntExpr->getOpcode();668 if (BinaryOperator::isAdditiveOp(lop)) {669 // Convert the two constants to a common type, then combine them.670 671 // resultTy may not be the best type to convert to, but it's672 // probably the best choice in expressions with mixed type673 // (such as x+1U+2LL). The rules for implicit conversions should674 // choose a reasonable type to preserve the expression, and will675 // at least match how the value is going to be used.676 APSIntType IntType = BasicVals.getAPSIntType(resultTy);677 const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());678 const llvm::APSInt &second = IntType.convert(*RHSValue);679 680 // If the op and lop agrees, then we just need to681 // sum the constants. Otherwise, we change to operation682 // type if substraction would produce negative value683 // (and cause overflow for unsigned integers),684 // as consequence x+1U-10 produces x-9U, instead685 // of x+4294967287U, that would be produced without this686 // additional check.687 std::optional<APSIntPtr> newRHS;688 if (lop == op) {689 newRHS = BasicVals.evalAPSInt(BO_Add, first, second);690 } else if (first >= second) {691 newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);692 op = lop;693 } else {694 newRHS = BasicVals.evalAPSInt(BO_Sub, second, first);695 }696 697 assert(newRHS && "Invalid operation despite common type!");698 rhs = nonloc::ConcreteInt(*newRHS);699 lhs = nonloc::SymbolVal(symIntExpr->getLHS());700 continue;701 }702 }703 704 // Otherwise, make a SymIntExpr out of the expression.705 return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy);706 }707 }708 709 // Is the RHS a constant?710 if (const llvm::APSInt *RHSValue = getConstValue(state, rhs))711 return MakeSymIntVal(Sym, op, *RHSValue, resultTy);712 713 if (std::optional<NonLoc> V = tryRearrange(state, op, lhs, rhs, resultTy))714 return *V;715 716 // Give up -- this is not a symbolic expression we can handle.717 return makeSymExprValNN(op, InputLHS, InputRHS, resultTy);718 }719 }720 }721}722 723static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR,724 const FieldRegion *RightFR,725 BinaryOperator::Opcode op,726 QualType resultTy,727 SimpleSValBuilder &SVB) {728 // Only comparisons are meaningful here!729 if (!BinaryOperator::isComparisonOp(op))730 return UnknownVal();731 732 // Next, see if the two FRs have the same super-region.733 // FIXME: This doesn't handle casts yet, and simply stripping the casts734 // doesn't help.735 if (LeftFR->getSuperRegion() != RightFR->getSuperRegion())736 return UnknownVal();737 738 const FieldDecl *LeftFD = LeftFR->getDecl();739 const FieldDecl *RightFD = RightFR->getDecl();740 const RecordDecl *RD = LeftFD->getParent();741 742 // Make sure the two FRs are from the same kind of record. Just in case!743 // FIXME: This is probably where inheritance would be a problem.744 if (RD != RightFD->getParent())745 return UnknownVal();746 747 // We know for sure that the two fields are not the same, since that748 // would have given us the same SVal.749 if (op == BO_EQ)750 return SVB.makeTruthVal(false, resultTy);751 if (op == BO_NE)752 return SVB.makeTruthVal(true, resultTy);753 754 // Iterate through the fields and see which one comes first.755 // [C99 6.7.2.1.13] "Within a structure object, the non-bit-field756 // members and the units in which bit-fields reside have addresses that757 // increase in the order in which they are declared."758 bool leftFirst = (op == BO_LT || op == BO_LE);759 for (const auto *I : RD->fields()) {760 if (I == LeftFD)761 return SVB.makeTruthVal(leftFirst, resultTy);762 if (I == RightFD)763 return SVB.makeTruthVal(!leftFirst, resultTy);764 }765 766 llvm_unreachable("Fields not found in parent record's definition");767}768 769// This is used in debug builds only for now because some downstream users770// may hit this assert in their subsequent merges.771// There are still places in the analyzer where equal bitwidth Locs772// are compared, and need to be found and corrected. Recent previous fixes have773// addressed the known problems of making NULLs with specific bitwidths774// for Loc comparisons along with deprecation of APIs for the same purpose.775//776static void assertEqualBitWidths(ProgramStateRef State, Loc RhsLoc,777 Loc LhsLoc) {778 // Implements a "best effort" check for RhsLoc and LhsLoc bit widths779 ASTContext &Ctx = State->getStateManager().getContext();780 uint64_t RhsBitwidth =781 RhsLoc.getType(Ctx).isNull() ? 0 : Ctx.getTypeSize(RhsLoc.getType(Ctx));782 uint64_t LhsBitwidth =783 LhsLoc.getType(Ctx).isNull() ? 0 : Ctx.getTypeSize(LhsLoc.getType(Ctx));784 if (RhsBitwidth && LhsBitwidth && (LhsLoc.getKind() == RhsLoc.getKind())) {785 assert(RhsBitwidth == LhsBitwidth &&786 "RhsLoc and LhsLoc bitwidth must be same!");787 }788}789 790// FIXME: all this logic will change if/when we have MemRegion::getLocation().791SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state,792 BinaryOperator::Opcode op,793 Loc lhs, Loc rhs,794 QualType resultTy) {795 796 // Assert that bitwidth of lhs and rhs are the same.797 // This can happen if two different address spaces are used,798 // and the bitwidths of the address spaces are different.799 // See LIT case clang/test/Analysis/cstring-checker-addressspace.c800 // FIXME: See comment above in the function assertEqualBitWidths801 assertEqualBitWidths(state, rhs, lhs);802 803 // Only comparisons and subtractions are valid operations on two pointers.804 // See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15].805 // However, if a pointer is casted to an integer, evalBinOpNN may end up806 // calling this function with another operation (PR7527). We don't attempt to807 // model this for now, but it could be useful, particularly when the808 // "location" is actually an integer value that's been passed through a void*.809 if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub))810 return UnknownVal();811 812 // Special cases for when both sides are identical.813 if (lhs == rhs) {814 switch (op) {815 default:816 llvm_unreachable("Unimplemented operation for two identical values");817 case BO_Sub:818 return makeZeroVal(resultTy);819 case BO_EQ:820 case BO_LE:821 case BO_GE:822 return makeTruthVal(true, resultTy);823 case BO_NE:824 case BO_LT:825 case BO_GT:826 return makeTruthVal(false, resultTy);827 }828 }829 830 switch (lhs.getKind()) {831 default:832 llvm_unreachable("Ordering not implemented for this Loc.");833 834 case loc::GotoLabelKind:835 // The only thing we know about labels is that they're non-null.836 if (rhs.isZeroConstant()) {837 switch (op) {838 default:839 break;840 case BO_Sub:841 return evalCast(lhs, resultTy, QualType{});842 case BO_EQ:843 case BO_LE:844 case BO_LT:845 return makeTruthVal(false, resultTy);846 case BO_NE:847 case BO_GT:848 case BO_GE:849 return makeTruthVal(true, resultTy);850 }851 }852 // There may be two labels for the same location, and a function region may853 // have the same address as a label at the start of the function (depending854 // on the ABI).855 // FIXME: we can probably do a comparison against other MemRegions, though.856 // FIXME: is there a way to tell if two labels refer to the same location?857 return UnknownVal();858 859 case loc::ConcreteIntKind: {860 auto L = lhs.castAs<loc::ConcreteInt>();861 862 // If one of the operands is a symbol and the other is a constant,863 // build an expression for use by the constraint manager.864 if (SymbolRef rSym = rhs.getAsLocSymbol()) {865 if (op == BO_Cmp)866 return UnknownVal();867 868 if (!BinaryOperator::isComparisonOp(op))869 return makeNonLoc(L.getValue(), op, rSym, resultTy);870 871 op = BinaryOperator::reverseComparisonOp(op);872 return makeNonLoc(rSym, op, L.getValue(), resultTy);873 }874 875 // If both operands are constants, just perform the operation.876 if (std::optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {877 assert(BinaryOperator::isComparisonOp(op) || op == BO_Sub);878 879 if (std::optional<APSIntPtr> ResultInt =880 BasicVals.evalAPSInt(op, L.getValue(), rInt->getValue()))881 return evalCast(nonloc::ConcreteInt(*ResultInt), resultTy, QualType{});882 return UnknownVal();883 }884 885 // Special case comparisons against NULL.886 // This must come after the test if the RHS is a symbol, which is used to887 // build constraints. The address of any non-symbolic region is guaranteed888 // to be non-NULL, as is any label.889 assert((isa<loc::MemRegionVal, loc::GotoLabel>(rhs)));890 if (lhs.isZeroConstant()) {891 switch (op) {892 default:893 break;894 case BO_EQ:895 case BO_GT:896 case BO_GE:897 return makeTruthVal(false, resultTy);898 case BO_NE:899 case BO_LT:900 case BO_LE:901 return makeTruthVal(true, resultTy);902 }903 }904 905 // Comparing an arbitrary integer to a region or label address is906 // completely unknowable.907 return UnknownVal();908 }909 case loc::MemRegionValKind: {910 if (std::optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {911 // If one of the operands is a symbol and the other is a constant,912 // build an expression for use by the constraint manager.913 if (SymbolRef lSym = lhs.getAsLocSymbol(true)) {914 if (BinaryOperator::isComparisonOp(op))915 return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy);916 return UnknownVal();917 }918 // Special case comparisons to NULL.919 // This must come after the test if the LHS is a symbol, which is used to920 // build constraints. The address of any non-symbolic region is guaranteed921 // to be non-NULL.922 if (rInt->isZeroConstant()) {923 if (op == BO_Sub)924 return evalCast(lhs, resultTy, QualType{});925 926 if (BinaryOperator::isComparisonOp(op)) {927 QualType boolType = getContext().BoolTy;928 NonLoc l = evalCast(lhs, boolType, QualType{}).castAs<NonLoc>();929 NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>();930 return evalBinOpNN(state, op, l, r, resultTy);931 }932 }933 934 // Comparing a region to an arbitrary integer is completely unknowable.935 return UnknownVal();936 }937 938 // Get both values as regions, if possible.939 const MemRegion *LeftMR = lhs.getAsRegion();940 assert(LeftMR && "MemRegionValKind SVal doesn't have a region!");941 942 const MemRegion *RightMR = rhs.getAsRegion();943 if (!RightMR)944 // The RHS is probably a label, which in theory could address a region.945 // FIXME: we can probably make a more useful statement about non-code946 // regions, though.947 return UnknownVal();948 949 const MemRegion *LeftBase = LeftMR->getBaseRegion();950 const MemRegion *RightBase = RightMR->getBaseRegion();951 const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace(state);952 const MemSpaceRegion *RightMS = RightBase->getMemorySpace(state);953 const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion();954 955 // If the two regions are from different known memory spaces they cannot be956 // equal. Also, assume that no symbolic region (whose memory space is957 // unknown) is on the stack.958 if (LeftMS != RightMS &&959 ((LeftMS != UnknownMS && RightMS != UnknownMS) ||960 (isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) {961 switch (op) {962 default:963 return UnknownVal();964 case BO_EQ:965 return makeTruthVal(false, resultTy);966 case BO_NE:967 return makeTruthVal(true, resultTy);968 }969 }970 971 // If both values wrap regions, see if they're from different base regions.972 // Note, heap base symbolic regions are assumed to not alias with973 // each other; for example, we assume that malloc returns different address974 // on each invocation.975 // FIXME: ObjC object pointers always reside on the heap, but currently976 // we treat their memory space as unknown, because symbolic pointers977 // to ObjC objects may alias. There should be a way to construct978 // possibly-aliasing heap-based regions. For instance, MacOSXApiChecker979 // guesses memory space for ObjC object pointers manually instead of980 // relying on us.981 if (LeftBase != RightBase &&982 ((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) ||983 (isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){984 switch (op) {985 default:986 return UnknownVal();987 case BO_EQ:988 return makeTruthVal(false, resultTy);989 case BO_NE:990 return makeTruthVal(true, resultTy);991 }992 }993 994 // Handle special cases for when both regions are element regions.995 const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR);996 const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR);997 if (RightER && LeftER) {998 // Next, see if the two ERs have the same super-region and matching types.999 // FIXME: This should do something useful even if the types don't match,1000 // though if both indexes are constant the RegionRawOffset path will1001 // give the correct answer.1002 if (LeftER->getSuperRegion() == RightER->getSuperRegion() &&1003 LeftER->getElementType() == RightER->getElementType()) {1004 // Get the left index and cast it to the correct type.1005 // If the index is unknown or undefined, bail out here.1006 SVal LeftIndexVal = LeftER->getIndex();1007 std::optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>();1008 if (!LeftIndex)1009 return UnknownVal();1010 LeftIndexVal = evalCast(*LeftIndex, ArrayIndexTy, QualType{});1011 LeftIndex = LeftIndexVal.getAs<NonLoc>();1012 if (!LeftIndex)1013 return UnknownVal();1014 1015 // Do the same for the right index.1016 SVal RightIndexVal = RightER->getIndex();1017 std::optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>();1018 if (!RightIndex)1019 return UnknownVal();1020 RightIndexVal = evalCast(*RightIndex, ArrayIndexTy, QualType{});1021 RightIndex = RightIndexVal.getAs<NonLoc>();1022 if (!RightIndex)1023 return UnknownVal();1024 1025 // Actually perform the operation.1026 // evalBinOpNN expects the two indexes to already be the right type.1027 return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy);1028 }1029 }1030 1031 // Special handling of the FieldRegions, even with symbolic offsets.1032 const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR);1033 const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR);1034 if (RightFR && LeftFR) {1035 SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy,1036 *this);1037 if (!R.isUnknown())1038 return R;1039 }1040 1041 // Compare the regions using the raw offsets.1042 RegionOffset LeftOffset = LeftMR->getAsOffset();1043 RegionOffset RightOffset = RightMR->getAsOffset();1044 1045 if (LeftOffset.getRegion() != nullptr &&1046 LeftOffset.getRegion() == RightOffset.getRegion() &&1047 !LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) {1048 int64_t left = LeftOffset.getOffset();1049 int64_t right = RightOffset.getOffset();1050 1051 switch (op) {1052 default:1053 return UnknownVal();1054 case BO_LT:1055 return makeTruthVal(left < right, resultTy);1056 case BO_GT:1057 return makeTruthVal(left > right, resultTy);1058 case BO_LE:1059 return makeTruthVal(left <= right, resultTy);1060 case BO_GE:1061 return makeTruthVal(left >= right, resultTy);1062 case BO_EQ:1063 return makeTruthVal(left == right, resultTy);1064 case BO_NE:1065 return makeTruthVal(left != right, resultTy);1066 }1067 }1068 1069 // At this point we're not going to get a good answer, but we can try1070 // conjuring an expression instead.1071 SymbolRef LHSSym = lhs.getAsLocSymbol();1072 SymbolRef RHSSym = rhs.getAsLocSymbol();1073 if (LHSSym && RHSSym)1074 return makeNonLoc(LHSSym, op, RHSSym, resultTy);1075 1076 // If we get here, we have no way of comparing the regions.1077 return UnknownVal();1078 }1079 }1080}1081 1082SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,1083 BinaryOperator::Opcode op, Loc lhs,1084 NonLoc rhs, QualType resultTy) {1085 if (op >= BO_PtrMemD && op <= BO_PtrMemI) {1086 if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) {1087 if (PTMSV->isNullMemberPointer())1088 return UndefinedVal();1089 1090 auto getFieldLValue = [&](const auto *FD) -> SVal {1091 SVal Result = lhs;1092 1093 for (const auto &I : *PTMSV)1094 Result = StateMgr.getStoreManager().evalDerivedToBase(1095 Result, I->getType(), I->isVirtual());1096 1097 return state->getLValue(FD, Result);1098 };1099 1100 if (const auto *FD = PTMSV->getDeclAs<FieldDecl>()) {1101 return getFieldLValue(FD);1102 }1103 if (const auto *FD = PTMSV->getDeclAs<IndirectFieldDecl>()) {1104 return getFieldLValue(FD);1105 }1106 }1107 1108 return rhs;1109 }1110 1111 assert(!BinaryOperator::isComparisonOp(op) &&1112 "arguments to comparison ops must be of the same type");1113 1114 SVal simplifiedRhs = simplifySVal(state, rhs);1115 if (auto simplifiedRhsAsNonLoc = simplifiedRhs.getAs<NonLoc>())1116 rhs = *simplifiedRhsAsNonLoc;1117 1118 // Special case: rhs is a zero constant.1119 if (rhs.isZeroConstant())1120 return lhs;1121 1122 // Perserve the null pointer so that it can be found by the DerefChecker.1123 if (lhs.isZeroConstant())1124 return lhs;1125 1126 // We are dealing with pointer arithmetic.1127 1128 // Handle pointer arithmetic on constant values.1129 if (std::optional<nonloc::ConcreteInt> rhsInt =1130 rhs.getAs<nonloc::ConcreteInt>()) {1131 if (std::optional<loc::ConcreteInt> lhsInt =1132 lhs.getAs<loc::ConcreteInt>()) {1133 const llvm::APSInt &leftI = lhsInt->getValue();1134 assert(leftI.isUnsigned());1135 llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true);1136 1137 // Convert the bitwidth of rightI. This should deal with overflow1138 // since we are dealing with concrete values.1139 rightI = rightI.extOrTrunc(leftI.getBitWidth());1140 1141 // Offset the increment by the pointer size.1142 llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);1143 QualType pointeeType = resultTy->getPointeeType();1144 Multiplicand = getContext().getTypeSizeInChars(pointeeType).getQuantity();1145 rightI *= Multiplicand;1146 1147 // Compute the adjusted pointer.1148 switch (op) {1149 case BO_Add:1150 rightI = leftI + rightI;1151 break;1152 case BO_Sub:1153 rightI = leftI - rightI;1154 break;1155 default:1156 llvm_unreachable("Invalid pointer arithmetic operation");1157 }1158 return loc::ConcreteInt(getBasicValueFactory().getValue(rightI));1159 }1160 }1161 1162 // Handle cases where 'lhs' is a region.1163 if (const MemRegion *region = lhs.getAsRegion()) {1164 rhs = convertToArrayIndex(rhs).castAs<NonLoc>();1165 SVal index = UnknownVal();1166 const SubRegion *superR = nullptr;1167 // We need to know the type of the pointer in order to add an integer to it.1168 // Depending on the type, different amount of bytes is added.1169 QualType elementType;1170 1171 if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) {1172 assert(op == BO_Add || op == BO_Sub);1173 index = evalBinOpNN(state, op, elemReg->getIndex(), rhs,1174 getArrayIndexType());1175 superR = cast<SubRegion>(elemReg->getSuperRegion());1176 elementType = elemReg->getElementType();1177 }1178 else if (isa<SubRegion>(region)) {1179 assert(op == BO_Add || op == BO_Sub);1180 index = (op == BO_Add) ? rhs : evalMinus(rhs);1181 superR = cast<SubRegion>(region);1182 // TODO: Is this actually reliable? Maybe improving our MemRegion1183 // hierarchy to provide typed regions for all non-void pointers would be1184 // better. For instance, we cannot extend this towards LocAsInteger1185 // operations, where result type of the expression is integer.1186 if (resultTy->isAnyPointerType())1187 elementType = resultTy->getPointeeType();1188 }1189 1190 // Represent arithmetic on void pointers as arithmetic on char pointers.1191 // It is fine when a TypedValueRegion of char value type represents1192 // a void pointer. Note that arithmetic on void pointers is a GCC extension.1193 if (elementType->isVoidType())1194 elementType = getContext().CharTy;1195 1196 if (std::optional<NonLoc> indexV = index.getAs<NonLoc>()) {1197 return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,1198 superR, getContext()));1199 }1200 }1201 return UnknownVal();1202}1203 1204const llvm::APSInt *SimpleSValBuilder::getConstValue(ProgramStateRef state,1205 SVal V) {1206 if (const llvm::APSInt *Res = getConcreteValue(V))1207 return Res;1208 1209 if (SymbolRef Sym = V.getAsSymbol())1210 return state->getConstraintManager().getSymVal(state, Sym);1211 1212 return nullptr;1213}1214 1215const llvm::APSInt *SimpleSValBuilder::getConcreteValue(SVal V) {1216 if (std::optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>())1217 return X->getValue().get();1218 1219 if (std::optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>())1220 return X->getValue().get();1221 1222 return nullptr;1223}1224 1225const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state,1226 SVal V) {1227 return getConstValue(state, simplifySVal(state, V));1228}1229 1230const llvm::APSInt *SimpleSValBuilder::getMinValue(ProgramStateRef state,1231 SVal V) {1232 V = simplifySVal(state, V);1233 1234 if (const llvm::APSInt *Res = getConcreteValue(V))1235 return Res;1236 1237 if (SymbolRef Sym = V.getAsSymbol())1238 return state->getConstraintManager().getSymMinVal(state, Sym);1239 1240 return nullptr;1241}1242 1243const llvm::APSInt *SimpleSValBuilder::getMaxValue(ProgramStateRef state,1244 SVal V) {1245 V = simplifySVal(state, V);1246 1247 if (const llvm::APSInt *Res = getConcreteValue(V))1248 return Res;1249 1250 if (SymbolRef Sym = V.getAsSymbol())1251 return state->getConstraintManager().getSymMaxVal(state, Sym);1252 1253 return nullptr;1254}1255 1256SVal SimpleSValBuilder::simplifyUntilFixpoint(ProgramStateRef State, SVal Val) {1257 SVal SimplifiedVal = simplifySValOnce(State, Val);1258 while (SimplifiedVal != Val) {1259 Val = SimplifiedVal;1260 SimplifiedVal = simplifySValOnce(State, Val);1261 }1262 return SimplifiedVal;1263}1264 1265SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) {1266 return simplifyUntilFixpoint(State, V);1267}1268 1269SVal SimpleSValBuilder::simplifySValOnce(ProgramStateRef State, SVal V) {1270 // For now, this function tries to constant-fold symbols inside a1271 // nonloc::SymbolVal, and does nothing else. More simplifications should1272 // be possible, such as constant-folding an index in an ElementRegion.1273 1274 class Simplifier : public FullSValVisitor<Simplifier, SVal> {1275 ProgramStateRef State;1276 SValBuilder &SVB;1277 1278 // Cache results for the lifetime of the Simplifier. Results change every1279 // time new constraints are added to the program state, which is the whole1280 // point of simplifying, and for that very reason it's pointless to maintain1281 // the same cache for the duration of the whole analysis.1282 llvm::DenseMap<SymbolRef, SVal> Cached;1283 1284 static bool isUnchanged(SymbolRef Sym, SVal Val) {1285 return Sym == Val.getAsSymbol();1286 }1287 1288 SVal cache(SymbolRef Sym, SVal V) {1289 Cached[Sym] = V;1290 return V;1291 }1292 1293 SVal skip(SymbolRef Sym) {1294 return cache(Sym, SVB.makeSymbolVal(Sym));1295 }1296 1297 // Return the known const value for the Sym if available, or return Undef1298 // otherwise.1299 SVal getConst(SymbolRef Sym) {1300 const llvm::APSInt *Const =1301 State->getConstraintManager().getSymVal(State, Sym);1302 if (Const)1303 return Loc::isLocType(Sym->getType()) ? (SVal)SVB.makeIntLocVal(*Const)1304 : (SVal)SVB.makeIntVal(*Const);1305 return UndefinedVal();1306 }1307 1308 SVal getConstOrVisit(SymbolRef Sym) {1309 const SVal Ret = getConst(Sym);1310 if (Ret.isUndef())1311 return Visit(Sym);1312 return Ret;1313 }1314 1315 public:1316 Simplifier(ProgramStateRef State)1317 : State(State), SVB(State->getStateManager().getSValBuilder()) {}1318 1319 SVal VisitSymbolData(const SymbolData *S) {1320 // No cache here.1321 if (const llvm::APSInt *I =1322 State->getConstraintManager().getSymVal(State, S))1323 return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I)1324 : (SVal)SVB.makeIntVal(*I);1325 return SVB.makeSymbolVal(S);1326 }1327 1328 SVal VisitSymIntExpr(const SymIntExpr *S) {1329 auto I = Cached.find(S);1330 if (I != Cached.end())1331 return I->second;1332 1333 SVal LHS = getConstOrVisit(S->getLHS());1334 if (isUnchanged(S->getLHS(), LHS))1335 return skip(S);1336 1337 SVal RHS;1338 // By looking at the APSInt in the right-hand side of S, we cannot1339 // figure out if it should be treated as a Loc or as a NonLoc.1340 // So make our guess by recalling that we cannot multiply pointers1341 // or compare a pointer to an integer.1342 if (Loc::isLocType(S->getLHS()->getType()) &&1343 BinaryOperator::isComparisonOp(S->getOpcode())) {1344 // The usual conversion of $sym to &SymRegion{$sym}, as they have1345 // the same meaning for Loc-type symbols, but the latter form1346 // is preferred in SVal computations for being Loc itself.1347 if (SymbolRef Sym = LHS.getAsSymbol()) {1348 assert(Loc::isLocType(Sym->getType()));1349 LHS = SVB.makeLoc(Sym);1350 }1351 RHS = SVB.makeIntLocVal(S->getRHS());1352 } else {1353 RHS = SVB.makeIntVal(S->getRHS());1354 }1355 1356 return cache(1357 S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));1358 }1359 1360 SVal VisitIntSymExpr(const IntSymExpr *S) {1361 auto I = Cached.find(S);1362 if (I != Cached.end())1363 return I->second;1364 1365 SVal RHS = getConstOrVisit(S->getRHS());1366 if (isUnchanged(S->getRHS(), RHS))1367 return skip(S);1368 1369 SVal LHS = SVB.makeIntVal(S->getLHS());1370 return cache(1371 S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));1372 }1373 1374 SVal VisitSymSymExpr(const SymSymExpr *S) {1375 auto I = Cached.find(S);1376 if (I != Cached.end())1377 return I->second;1378 1379 // For now don't try to simplify mixed Loc/NonLoc expressions1380 // because they often appear from LocAsInteger operations1381 // and we don't know how to combine a LocAsInteger1382 // with a concrete value.1383 if (Loc::isLocType(S->getLHS()->getType()) !=1384 Loc::isLocType(S->getRHS()->getType()))1385 return skip(S);1386 1387 SVal LHS = getConstOrVisit(S->getLHS());1388 SVal RHS = getConstOrVisit(S->getRHS());1389 1390 if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS))1391 return skip(S);1392 1393 return cache(1394 S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));1395 }1396 1397 SVal VisitSymbolCast(const SymbolCast *S) {1398 auto I = Cached.find(S);1399 if (I != Cached.end())1400 return I->second;1401 const SymExpr *OpSym = S->getOperand();1402 SVal OpVal = getConstOrVisit(OpSym);1403 if (isUnchanged(OpSym, OpVal))1404 return skip(S);1405 1406 return cache(S, SVB.evalCast(OpVal, S->getType(), OpSym->getType()));1407 }1408 1409 SVal VisitUnarySymExpr(const UnarySymExpr *S) {1410 auto I = Cached.find(S);1411 if (I != Cached.end())1412 return I->second;1413 SVal Op = getConstOrVisit(S->getOperand());1414 if (isUnchanged(S->getOperand(), Op))1415 return skip(S);1416 1417 return cache(1418 S, SVB.evalUnaryOp(State, S->getOpcode(), Op, S->getType()));1419 }1420 1421 SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); }1422 1423 SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); }1424 1425 SVal VisitSymbolVal(nonloc::SymbolVal V) {1426 // Simplification is much more costly than computing complexity.1427 // For high complexity, it may be not worth it.1428 return Visit(V.getSymbol());1429 }1430 1431 SVal VisitSVal(SVal V) { return V; }1432 };1433 1434 SVal SimplifiedV = Simplifier(State).Visit(V);1435 return SimplifiedV;1436}1437