lib/StaticAnalyzer/RangeConstraintManager.cpp

   1 //== RangeConstraintManager.cpp - Manage range constraints.------*- 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 RangeConstraintManager, a class that tracks simple
  11 //  equality and inequality constraints on symbolic values of GRState.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "SimpleConstraintManager.h"
  16 #include "clang/StaticAnalyzer/PathSensitive/GRState.h"
  17 #include "clang/StaticAnalyzer/PathSensitive/GRStateTrait.h"
  18 #include "clang/StaticAnalyzer/PathSensitive/TransferFuncs.h"
  19 #include "clang/StaticAnalyzer/ManagerRegistry.h"
  20 #include "llvm/Support/Debug.h"
  21 #include "llvm/ADT/FoldingSet.h"
  22 #include "llvm/ADT/ImmutableSet.h"
  23 #include "llvm/Support/raw_ostream.h"
  24
  25 using namespace clang;
  26 using namespace ento;
  27
  28 namespace { class ConstraintRange {}; }
  29 static int ConstraintRangeIndex = 0;
  30
  31 /// A Range represents the closed range [from, to].  The caller must
  32 /// guarantee that from <= to.  Note that Range is immutable, so as not
  33 /// to subvert RangeSet's immutability.
  34 namespace {
  35 class Range : public std::pair<const llvm::APSInt*,
  36                                                 const llvm::APSInt*> {
  37 public:
  38   Range(const llvm::APSInt &from, const llvm::APSInt &to)
  39     : std::pair<const llvm::APSInt*, const llvm::APSInt*>(&from, &to) {
  40     assert(from <= to);
  41   }
  42   bool Includes(const llvm::APSInt &v) const {
  43     return *first <= v && v <= *second;
  44   }
  45   const llvm::APSInt &From() const {
  46     return *first;
  47   }
  48   const llvm::APSInt &To() const {
  49     return *second;
  50   }
  51   const llvm::APSInt *getConcreteValue() const {
  52     return &From() == &To() ? &From() : NULL;
  53   }
  54
  55   void Profile(llvm::FoldingSetNodeID &ID) const {
  56     ID.AddPointer(&From());
  57     ID.AddPointer(&To());
  58   }
  59 };
  60
  61
  62 class RangeTrait : public llvm::ImutContainerInfo<Range> {
  63 public:
  64   // When comparing if one Range is less than another, we should compare
  65   // the actual APSInt values instead of their pointers.  This keeps the order
  66   // consistent (instead of comparing by pointer values) and can potentially
  67   // be used to speed up some of the operations in RangeSet.
  68   static inline bool isLess(key_type_ref lhs, key_type_ref rhs) {
  69     return *lhs.first < *rhs.first || (!(*rhs.first < *lhs.first) &&
  70                                        *lhs.second < *rhs.second);
  71   }
  72 };
  73
  74 /// RangeSet contains a set of ranges. If the set is empty, then
  75 ///  there the value of a symbol is overly constrained and there are no
  76 ///  possible values for that symbol.
  77 class RangeSet {
  78   typedef llvm::ImmutableSet<Range, RangeTrait> PrimRangeSet;
  79   PrimRangeSet ranges; // no need to make const, since it is an
  80                        // ImmutableSet - this allows default operator=
  81                        // to work.
  82 public:
  83   typedef PrimRangeSet::Factory Factory;
  84   typedef PrimRangeSet::iterator iterator;
  85
  86   RangeSet(PrimRangeSet RS) : ranges(RS) {}
  87
  88   iterator begin() const { return ranges.begin(); }
  89   iterator end() const { return ranges.end(); }
  90
  91   bool isEmpty() const { return ranges.isEmpty(); }
  92
  93   /// Construct a new RangeSet representing '{ [from, to] }'.
  94   RangeSet(Factory &F, const llvm::APSInt &from, const llvm::APSInt &to)
  95     : ranges(F.add(F.getEmptySet(), Range(from, to))) {}
  96
  97   /// Profile - Generates a hash profile of this RangeSet for use
  98   ///  by FoldingSet.
  99   void Profile(llvm::FoldingSetNodeID &ID) const { ranges.Profile(ID); }
 100
 101   /// getConcreteValue - If a symbol is contrained to equal a specific integer
 102   ///  constant then this method returns that value.  Otherwise, it returns
 103   ///  NULL.
 104   const llvm::APSInt* getConcreteValue() const {
 105     return ranges.isSingleton() ? ranges.begin()->getConcreteValue() : 0;
 106   }
 107
 108 private:
 109   void IntersectInRange(BasicValueFactory &BV, Factory &F,
 110                         const llvm::APSInt &Lower,
 111                         const llvm::APSInt &Upper,
 112                         PrimRangeSet &newRanges,
 113                         PrimRangeSet::iterator &i,
 114                         PrimRangeSet::iterator &e) const {
 115     // There are six cases for each range R in the set:
 116     //   1. R is entirely before the intersection range.
 117     //   2. R is entirely after the intersection range.
 118     //   3. R contains the entire intersection range.
 119     //   4. R starts before the intersection range and ends in the middle.
 120     //   5. R starts in the middle of the intersection range and ends after it.
 121     //   6. R is entirely contained in the intersection range.
 122     // These correspond to each of the conditions below.
 123     for (/* i = begin(), e = end() */; i != e; ++i) {
 124       if (i->To() < Lower) {
 125         continue;
 126       }
 127       if (i->From() > Upper) {
 128         break;
 129       }
 130
 131       if (i->Includes(Lower)) {
 132         if (i->Includes(Upper)) {
 133           newRanges = F.add(newRanges, Range(BV.getValue(Lower),
 134                                              BV.getValue(Upper)));
 135           break;
 136         } else
 137           newRanges = F.add(newRanges, Range(BV.getValue(Lower), i->To()));
 138       } else {
 139         if (i->Includes(Upper)) {
 140           newRanges = F.add(newRanges, Range(i->From(), BV.getValue(Upper)));
 141           break;
 142         } else
 143           newRanges = F.add(newRanges, *i);
 144       }
 145     }
 146   }
 147
 148 public:
 149   // Returns a set containing the values in the receiving set, intersected with
 150   // the closed range [Lower, Upper]. Unlike the Range type, this range uses
 151   // modular arithmetic, corresponding to the common treatment of C integer
 152   // overflow. Thus, if the Lower bound is greater than the Upper bound, the
 153   // range is taken to wrap around. This is equivalent to taking the
 154   // intersection with the two ranges [Min, Upper] and [Lower, Max],
 155   // or, alternatively, /removing/ all integers between Upper and Lower.
 156   RangeSet Intersect(BasicValueFactory &BV, Factory &F,
 157                      const llvm::APSInt &Lower,
 158                      const llvm::APSInt &Upper) const {
 159     PrimRangeSet newRanges = F.getEmptySet();
 160
 161     PrimRangeSet::iterator i = begin(), e = end();
 162     if (Lower <= Upper)
 163       IntersectInRange(BV, F, Lower, Upper, newRanges, i, e);
 164     else {
 165       // The order of the next two statements is important!
 166       // IntersectInRange() does not reset the iteration state for i and e.
 167       // Therefore, the lower range most be handled first.
 168       IntersectInRange(BV, F, BV.getMinValue(Upper), Upper, newRanges, i, e);
 169       IntersectInRange(BV, F, Lower, BV.getMaxValue(Lower), newRanges, i, e);
 170     }
 171     return newRanges;
 172   }
 173
 174   void print(llvm::raw_ostream &os) const {
 175     bool isFirst = true;
 176     os << "{ ";
 177     for (iterator i = begin(), e = end(); i != e; ++i) {
 178       if (isFirst)
 179         isFirst = false;
 180       else
 181         os << ", ";
 182
 183       os << '[' << i->From().toString(10) << ", " << i->To().toString(10)
 184          << ']';
 185     }
 186     os << " }";
 187   }
 188
 189   bool operator==(const RangeSet &other) const {
 190     return ranges == other.ranges;
 191   }
 192 };
 193 } // end anonymous namespace
 194
 195 typedef llvm::ImmutableMap<SymbolRef,RangeSet> ConstraintRangeTy;
 196
 197 namespace clang {
 198 namespace ento {
 199 template<>
 200 struct GRStateTrait<ConstraintRange>
 201   : public GRStatePartialTrait<ConstraintRangeTy> {
 202   static inline void* GDMIndex() { return &ConstraintRangeIndex; }
 203 };
 204 }
 205 }
 206
 207 namespace {
 208 class RangeConstraintManager : public SimpleConstraintManager{
 209   RangeSet GetRange(const GRState *state, SymbolRef sym);
 210 public:
 211   RangeConstraintManager(SubEngine &subengine)
 212     : SimpleConstraintManager(subengine) {}
 213
 214   const GRState *assumeSymNE(const GRState* state, SymbolRef sym,
 215                              const llvm::APSInt& Int,
 216                              const llvm::APSInt& Adjustment);
 217
 218   const GRState *assumeSymEQ(const GRState* state, SymbolRef sym,
 219                              const llvm::APSInt& Int,
 220                              const llvm::APSInt& Adjustment);
 221
 222   const GRState *assumeSymLT(const GRState* state, SymbolRef sym,
 223                              const llvm::APSInt& Int,
 224                              const llvm::APSInt& Adjustment);
 225
 226   const GRState *assumeSymGT(const GRState* state, SymbolRef sym,
 227                              const llvm::APSInt& Int,
 228                              const llvm::APSInt& Adjustment);
 229
 230   const GRState *assumeSymGE(const GRState* state, SymbolRef sym,
 231                              const llvm::APSInt& Int,
 232                              const llvm::APSInt& Adjustment);
 233
 234   const GRState *assumeSymLE(const GRState* state, SymbolRef sym,
 235                              const llvm::APSInt& Int,
 236                              const llvm::APSInt& Adjustment);
 237
 238   const llvm::APSInt* getSymVal(const GRState* St, SymbolRef sym) const;
 239
 240   // FIXME: Refactor into SimpleConstraintManager?
 241   bool isEqual(const GRState* St, SymbolRef sym, const llvm::APSInt& V) const {
 242     const llvm::APSInt *i = getSymVal(St, sym);
 243     return i ? *i == V : false;
 244   }
 245
 246   const GRState* removeDeadBindings(const GRState* St, SymbolReaper& SymReaper);
 247
 248   void print(const GRState* St, llvm::raw_ostream& Out,
 249              const char* nl, const char *sep);
 250
 251 private:
 252   RangeSet::Factory F;
 253 };
 254
 255 } // end anonymous namespace
 256
 257 ConstraintManager* ento::CreateRangeConstraintManager(GRStateManager&,
 258                                                     SubEngine &subeng) {
 259   return new RangeConstraintManager(subeng);
 260 }
 261
 262 const llvm::APSInt* RangeConstraintManager::getSymVal(const GRState* St,
 263                                                       SymbolRef sym) const {
 264   const ConstraintRangeTy::data_type *T = St->get<ConstraintRange>(sym);
 265   return T ? T->getConcreteValue() : NULL;
 266 }
 267
 268 /// Scan all symbols referenced by the constraints. If the symbol is not alive
 269 /// as marked in LSymbols, mark it as dead in DSymbols.
 270 const GRState*
 271 RangeConstraintManager::removeDeadBindings(const GRState* state,
 272                                            SymbolReaper& SymReaper) {
 273
 274   ConstraintRangeTy CR = state->get<ConstraintRange>();
 275   ConstraintRangeTy::Factory& CRFactory = state->get_context<ConstraintRange>();
 276
 277   for (ConstraintRangeTy::iterator I = CR.begin(), E = CR.end(); I != E; ++I) {
 278     SymbolRef sym = I.getKey();
 279     if (SymReaper.maybeDead(sym))
 280       CR = CRFactory.remove(CR, sym);
 281   }
 282
 283   return state->set<ConstraintRange>(CR);
 284 }
 285
 286 RangeSet
 287 RangeConstraintManager::GetRange(const GRState *state, SymbolRef sym) {
 288   if (ConstraintRangeTy::data_type* V = state->get<ConstraintRange>(sym))
 289     return *V;
 290
 291   // Lazily generate a new RangeSet representing all possible values for the
 292   // given symbol type.
 293   QualType T = state->getSymbolManager().getType(sym);
 294   BasicValueFactory& BV = state->getBasicVals();
 295   return RangeSet(F, BV.getMinValue(T), BV.getMaxValue(T));
 296 }
 297
 298 //===------------------------------------------------------------------------===
 299 // assumeSymX methods: public interface for RangeConstraintManager.
 300 //===------------------------------------------------------------------------===/
 301
 302 // The syntax for ranges below is mathematical, using [x, y] for closed ranges
 303 // and (x, y) for open ranges. These ranges are modular, corresponding with
 304 // a common treatment of C integer overflow. This means that these methods
 305 // do not have to worry about overflow; RangeSet::Intersect can handle such a
 306 // "wraparound" range.
 307 // As an example, the range [UINT_MAX-1, 3) contains five values: UINT_MAX-1,
 308 // UINT_MAX, 0, 1, and 2.
 309
 310 const GRState*
 311 RangeConstraintManager::assumeSymNE(const GRState* state, SymbolRef sym,
 312                                     const llvm::APSInt& Int,
 313                                     const llvm::APSInt& Adjustment) {
 314   BasicValueFactory &BV = state->getBasicVals();
 315
 316   llvm::APSInt Lower = Int-Adjustment;
 317   llvm::APSInt Upper = Lower;
 318   --Lower;
 319   ++Upper;
 320
 321   // [Int-Adjustment+1, Int-Adjustment-1]
 322   // Notice that the lower bound is greater than the upper bound.
 323   RangeSet New = GetRange(state, sym).Intersect(BV, F, Upper, Lower);
 324   return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
 325 }
 326
 327 const GRState*
 328 RangeConstraintManager::assumeSymEQ(const GRState* state, SymbolRef sym,
 329                                     const llvm::APSInt& Int,
 330                                     const llvm::APSInt& Adjustment) {
 331   // [Int-Adjustment, Int-Adjustment]
 332   BasicValueFactory &BV = state->getBasicVals();
 333   llvm::APSInt AdjInt = Int-Adjustment;
 334   RangeSet New = GetRange(state, sym).Intersect(BV, F, AdjInt, AdjInt);
 335   return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
 336 }
 337
 338 const GRState*
 339 RangeConstraintManager::assumeSymLT(const GRState* state, SymbolRef sym,
 340                                     const llvm::APSInt& Int,
 341                                     const llvm::APSInt& Adjustment) {
 342   BasicValueFactory &BV = state->getBasicVals();
 343
 344   QualType T = state->getSymbolManager().getType(sym);
 345   const llvm::APSInt &Min = BV.getMinValue(T);
 346
 347   // Special case for Int == Min. This is always false.
 348   if (Int == Min)
 349     return NULL;
 350
 351   llvm::APSInt Lower = Min-Adjustment;
 352   llvm::APSInt Upper = Int-Adjustment;
 353   --Upper;
 354
 355   RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
 356   return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
 357 }
 358
 359 const GRState*
 360 RangeConstraintManager::assumeSymGT(const GRState* state, SymbolRef sym,
 361                                     const llvm::APSInt& Int,
 362                                     const llvm::APSInt& Adjustment) {
 363   BasicValueFactory &BV = state->getBasicVals();
 364
 365   QualType T = state->getSymbolManager().getType(sym);
 366   const llvm::APSInt &Max = BV.getMaxValue(T);
 367
 368   // Special case for Int == Max. This is always false.
 369   if (Int == Max)
 370     return NULL;
 371
 372   llvm::APSInt Lower = Int-Adjustment;
 373   llvm::APSInt Upper = Max-Adjustment;
 374   ++Lower;
 375
 376   RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
 377   return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
 378 }
 379
 380 const GRState*
 381 RangeConstraintManager::assumeSymGE(const GRState* state, SymbolRef sym,
 382                                     const llvm::APSInt& Int,
 383                                     const llvm::APSInt& Adjustment) {
 384   BasicValueFactory &BV = state->getBasicVals();
 385
 386   QualType T = state->getSymbolManager().getType(sym);
 387   const llvm::APSInt &Min = BV.getMinValue(T);
 388
 389   // Special case for Int == Min. This is always feasible.
 390   if (Int == Min)
 391     return state;
 392
 393   const llvm::APSInt &Max = BV.getMaxValue(T);
 394
 395   llvm::APSInt Lower = Int-Adjustment;
 396   llvm::APSInt Upper = Max-Adjustment;
 397
 398   RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
 399   return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
 400 }
 401
 402 const GRState*
 403 RangeConstraintManager::assumeSymLE(const GRState* state, SymbolRef sym,
 404                                     const llvm::APSInt& Int,
 405                                     const llvm::APSInt& Adjustment) {
 406   BasicValueFactory &BV = state->getBasicVals();
 407
 408   QualType T = state->getSymbolManager().getType(sym);
 409   const llvm::APSInt &Max = BV.getMaxValue(T);
 410
 411   // Special case for Int == Max. This is always feasible.
 412   if (Int == Max)
 413     return state;
 414
 415   const llvm::APSInt &Min = BV.getMinValue(T);
 416
 417   llvm::APSInt Lower = Min-Adjustment;
 418   llvm::APSInt Upper = Int-Adjustment;
 419
 420   RangeSet New = GetRange(state, sym).Intersect(BV, F, Lower, Upper);
 421   return New.isEmpty() ? NULL : state->set<ConstraintRange>(sym, New);
 422 }
 423
 424 //===------------------------------------------------------------------------===
 425 // Pretty-printing.
 426 //===------------------------------------------------------------------------===/
 427
 428 void RangeConstraintManager::print(const GRState* St, llvm::raw_ostream& Out,
 429                                    const char* nl, const char *sep) {
 430
 431   ConstraintRangeTy Ranges = St->get<ConstraintRange>();
 432
 433   if (Ranges.isEmpty())
 434     return;
 435
 436   Out << nl << sep << "ranges of symbol values:";
 437
 438   for (ConstraintRangeTy::iterator I=Ranges.begin(), E=Ranges.end(); I!=E; ++I){
 439     Out << nl << ' ' << I.getKey() << " : ";
 440     I.getData().print(Out);
 441   }
 442 }