1 //== SimpleConstraintManager.cpp --------------------------------*- 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 SimpleConstraintManager, a class that holds code shared 11 // between BasicConstraintManager and RangeConstraintManager. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "SimpleConstraintManager.h" 16 #include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h" 17 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 18 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 19 20 namespace clang { 21 22 namespace ento { 23 24 SimpleConstraintManager::~SimpleConstraintManager() {} 25 26 bool SimpleConstraintManager::canReasonAbout(SVal X) const { 27 nonloc::SymbolVal *SymVal = dyn_cast<nonloc::SymbolVal>(&X); 28 if (SymVal && SymVal->isExpression()) { 29 const SymExpr *SE = SymVal->getSymbol(); 30 31 if (const SymIntExpr *SIE = dyn_cast<SymIntExpr>(SE)) { 32 switch (SIE->getOpcode()) { 33 // We don't reason yet about bitwise-constraints on symbolic values. 34 case BO_And: 35 case BO_Or: 36 case BO_Xor: 37 return false; 38 // We don't reason yet about these arithmetic constraints on 39 // symbolic values. 40 case BO_Mul: 41 case BO_Div: 42 case BO_Rem: 43 case BO_Shl: 44 case BO_Shr: 45 return false; 46 // All other cases. 47 default: 48 return true; 49 } 50 } 51 52 return false; 53 } 54 55 return true; 56 } 57 58 ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state, 59 DefinedSVal Cond, 60 bool Assumption) { 61 if (isa<NonLoc>(Cond)) 62 return assume(state, cast<NonLoc>(Cond), Assumption); 63 else 64 return assume(state, cast<Loc>(Cond), Assumption); 65 } 66 67 ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state, Loc cond, 68 bool assumption) { 69 state = assumeAux(state, cond, assumption); 70 return SU.processAssume(state, cond, assumption); 71 } 72 73 ProgramStateRef SimpleConstraintManager::assumeAux(ProgramStateRef state, 74 Loc Cond, bool Assumption) { 75 switch (Cond.getSubKind()) { 76 default: 77 assert (false && "'Assume' not implemented for this Loc."); 78 return state; 79 80 case loc::MemRegionKind: { 81 // FIXME: Should this go into the storemanager? 82 83 const MemRegion *R = cast<loc::MemRegionVal>(Cond).getRegion(); 84 const SubRegion *SubR = dyn_cast<SubRegion>(R); 85 86 while (SubR) { 87 // FIXME: now we only find the first symbolic region. 88 if (const SymbolicRegion *SymR = dyn_cast<SymbolicRegion>(SubR)) { 89 const llvm::APSInt &zero = getBasicVals().getZeroWithPtrWidth(); 90 if (Assumption) 91 return assumeSymNE(state, SymR->getSymbol(), zero, zero); 92 else 93 return assumeSymEQ(state, SymR->getSymbol(), zero, zero); 94 } 95 SubR = dyn_cast<SubRegion>(SubR->getSuperRegion()); 96 } 97 98 // FALL-THROUGH. 99 } 100 101 case loc::GotoLabelKind: 102 return Assumption ? state : NULL; 103 104 case loc::ConcreteIntKind: { 105 bool b = cast<loc::ConcreteInt>(Cond).getValue() != 0; 106 bool isFeasible = b ? Assumption : !Assumption; 107 return isFeasible ? state : NULL; 108 } 109 } // end switch 110 } 111 112 ProgramStateRef SimpleConstraintManager::assume(ProgramStateRef state, 113 NonLoc cond, 114 bool assumption) { 115 state = assumeAux(state, cond, assumption); 116 return SU.processAssume(state, cond, assumption); 117 } 118 119 static BinaryOperator::Opcode NegateComparison(BinaryOperator::Opcode op) { 120 // FIXME: This should probably be part of BinaryOperator, since this isn't 121 // the only place it's used. (This code was copied from SimpleSValBuilder.cpp.) 122 switch (op) { 123 default: 124 llvm_unreachable("Invalid opcode."); 125 case BO_LT: return BO_GE; 126 case BO_GT: return BO_LE; 127 case BO_LE: return BO_GT; 128 case BO_GE: return BO_LT; 129 case BO_EQ: return BO_NE; 130 case BO_NE: return BO_EQ; 131 } 132 } 133 134 135 ProgramStateRef 136 SimpleConstraintManager::assumeAuxForSymbol(ProgramStateRef State, 137 SymbolRef Sym, bool Assumption) { 138 BasicValueFactory &BVF = getBasicVals(); 139 QualType T = Sym->getType(BVF.getContext()); 140 141 // None of the constraint solvers currently support non-integer types. 142 if (!T->isIntegerType()) 143 return State; 144 145 const llvm::APSInt &zero = BVF.getValue(0, T); 146 if (Assumption) 147 return assumeSymNE(State, Sym, zero, zero); 148 else 149 return assumeSymEQ(State, Sym, zero, zero); 150 } 151 152 ProgramStateRef SimpleConstraintManager::assumeAux(ProgramStateRef state, 153 NonLoc Cond, 154 bool Assumption) { 155 156 // We cannot reason about SymSymExprs, and can only reason about some 157 // SymIntExprs. 158 if (!canReasonAbout(Cond)) { 159 // Just add the constraint to the expression without trying to simplify. 160 SymbolRef sym = Cond.getAsSymExpr(); 161 return assumeAuxForSymbol(state, sym, Assumption); 162 } 163 164 BasicValueFactory &BasicVals = getBasicVals(); 165 166 switch (Cond.getSubKind()) { 167 default: 168 llvm_unreachable("'Assume' not implemented for this NonLoc"); 169 170 case nonloc::SymbolValKind: { 171 nonloc::SymbolVal& SV = cast<nonloc::SymbolVal>(Cond); 172 SymbolRef sym = SV.getSymbol(); 173 assert(sym); 174 175 // Handle SymbolData. 176 if (!SV.isExpression()) { 177 return assumeAuxForSymbol(state, sym, Assumption); 178 179 // Handle symbolic expression. 180 } else { 181 // We can only simplify expressions whose RHS is an integer. 182 const SymIntExpr *SE = dyn_cast<SymIntExpr>(sym); 183 if (!SE) 184 return assumeAuxForSymbol(state, sym, Assumption); 185 186 BinaryOperator::Opcode op = SE->getOpcode(); 187 // Implicitly compare non-comparison expressions to 0. 188 if (!BinaryOperator::isComparisonOp(op)) { 189 QualType T = SE->getType(BasicVals.getContext()); 190 const llvm::APSInt &zero = BasicVals.getValue(0, T); 191 op = (Assumption ? BO_NE : BO_EQ); 192 return assumeSymRel(state, SE, op, zero); 193 } 194 // From here on out, op is the real comparison we'll be testing. 195 if (!Assumption) 196 op = NegateComparison(op); 197 198 return assumeSymRel(state, SE->getLHS(), op, SE->getRHS()); 199 } 200 } 201 202 case nonloc::ConcreteIntKind: { 203 bool b = cast<nonloc::ConcreteInt>(Cond).getValue() != 0; 204 bool isFeasible = b ? Assumption : !Assumption; 205 return isFeasible ? state : NULL; 206 } 207 208 case nonloc::LocAsIntegerKind: 209 return assumeAux(state, cast<nonloc::LocAsInteger>(Cond).getLoc(), 210 Assumption); 211 } // end switch 212 } 213 214 static void computeAdjustment(SymbolRef &Sym, llvm::APSInt &Adjustment) { 215 // Is it a "($sym+constant1)" expression? 216 if (const SymIntExpr *SE = dyn_cast<SymIntExpr>(Sym)) { 217 BinaryOperator::Opcode Op = SE->getOpcode(); 218 if (Op == BO_Add || Op == BO_Sub) { 219 Sym = SE->getLHS(); 220 Adjustment = APSIntType(Adjustment).convert(SE->getRHS()); 221 222 // Don't forget to negate the adjustment if it's being subtracted. 223 // This should happen /after/ promotion, in case the value being 224 // subtracted is, say, CHAR_MIN, and the promoted type is 'int'. 225 if (Op == BO_Sub) 226 Adjustment = -Adjustment; 227 } 228 } 229 } 230 231 ProgramStateRef SimpleConstraintManager::assumeSymRel(ProgramStateRef state, 232 const SymExpr *LHS, 233 BinaryOperator::Opcode op, 234 const llvm::APSInt& Int) { 235 assert(BinaryOperator::isComparisonOp(op) && 236 "Non-comparison ops should be rewritten as comparisons to zero."); 237 238 BasicValueFactory &BVF = getBasicVals(); 239 ASTContext &Ctx = BVF.getContext(); 240 241 // Get the type used for calculating wraparound. 242 APSIntType WraparoundType = BVF.getAPSIntType(LHS->getType(Ctx)); 243 244 // We only handle simple comparisons of the form "$sym == constant" 245 // or "($sym+constant1) == constant2". 246 // The adjustment is "constant1" in the above expression. It's used to 247 // "slide" the solution range around for modular arithmetic. For example, 248 // x < 4 has the solution [0, 3]. x+2 < 4 has the solution [0-2, 3-2], which 249 // in modular arithmetic is [0, 1] U [UINT_MAX-1, UINT_MAX]. It's up to 250 // the subclasses of SimpleConstraintManager to handle the adjustment. 251 SymbolRef Sym = LHS; 252 llvm::APSInt Adjustment = WraparoundType.getZeroValue(); 253 computeAdjustment(Sym, Adjustment); 254 255 // Convert the right-hand side integer as necessary. 256 APSIntType ComparisonType = std::max(WraparoundType, APSIntType(Int)); 257 llvm::APSInt ConvertedInt = ComparisonType.convert(Int); 258 259 switch (op) { 260 default: 261 // No logic yet for other operators. assume the constraint is feasible. 262 return state; 263 264 case BO_EQ: 265 return assumeSymEQ(state, Sym, ConvertedInt, Adjustment); 266 267 case BO_NE: 268 return assumeSymNE(state, Sym, ConvertedInt, Adjustment); 269 270 case BO_GT: 271 return assumeSymGT(state, Sym, ConvertedInt, Adjustment); 272 273 case BO_GE: 274 return assumeSymGE(state, Sym, ConvertedInt, Adjustment); 275 276 case BO_LT: 277 return assumeSymLT(state, Sym, ConvertedInt, Adjustment); 278 279 case BO_LE: 280 return assumeSymLE(state, Sym, ConvertedInt, Adjustment); 281 } // end switch 282 } 283 284 } // end of namespace ento 285 286 } // end of namespace clang 287