1 //== SymbolManager.h - Management of Symbolic Values ------------*- 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 SymbolManager, a class that manages symbolic values
11 //  created for use by ExprEngine and related classes.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
16 #include "clang/Analysis/Analyses/LiveVariables.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/Store.h"
19 #include "llvm/Support/raw_ostream.h"
20 
21 using namespace clang;
22 using namespace ento;
23 
24 void SymExpr::dump() const {
25   dumpToStream(llvm::errs());
26 }
27 
28 static void print(raw_ostream &os, BinaryOperator::Opcode Op) {
29   switch (Op) {
30     default:
31       assert(false && "operator printing not implemented");
32       break;
33     case BO_Mul: os << '*'  ; break;
34     case BO_Div: os << '/'  ; break;
35     case BO_Rem: os << '%'  ; break;
36     case BO_Add: os << '+'  ; break;
37     case BO_Sub: os << '-'  ; break;
38     case BO_Shl: os << "<<" ; break;
39     case BO_Shr: os << ">>" ; break;
40     case BO_LT:  os << "<"  ; break;
41     case BO_GT:  os << '>'  ; break;
42     case BO_LE:  os << "<=" ; break;
43     case BO_GE:  os << ">=" ; break;
44     case BO_EQ:  os << "==" ; break;
45     case BO_NE:  os << "!=" ; break;
46     case BO_And: os << '&'  ; break;
47     case BO_Xor: os << '^'  ; break;
48     case BO_Or:  os << '|'  ; break;
49   }
50 }
51 
52 void SymIntExpr::dumpToStream(raw_ostream &os) const {
53   os << '(';
54   getLHS()->dumpToStream(os);
55   os << ") ";
56   print(os, getOpcode());
57   os << ' ' << getRHS().getZExtValue();
58   if (getRHS().isUnsigned()) os << 'U';
59 }
60 
61 void SymSymExpr::dumpToStream(raw_ostream &os) const {
62   os << '(';
63   getLHS()->dumpToStream(os);
64   os << ") ";
65   os << '(';
66   getRHS()->dumpToStream(os);
67   os << ')';
68 }
69 
70 void SymbolConjured::dumpToStream(raw_ostream &os) const {
71   os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
72 }
73 
74 void SymbolDerived::dumpToStream(raw_ostream &os) const {
75   os << "derived_$" << getSymbolID() << '{'
76      << getParentSymbol() << ',' << getRegion() << '}';
77 }
78 
79 void SymbolExtent::dumpToStream(raw_ostream &os) const {
80   os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
81 }
82 
83 void SymbolMetadata::dumpToStream(raw_ostream &os) const {
84   os << "meta_$" << getSymbolID() << '{'
85      << getRegion() << ',' << T.getAsString() << '}';
86 }
87 
88 void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
89   os << "reg_$" << getSymbolID() << "<" << R << ">";
90 }
91 
92 const SymbolRegionValue*
93 SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
94   llvm::FoldingSetNodeID profile;
95   SymbolRegionValue::Profile(profile, R);
96   void *InsertPos;
97   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
98   if (!SD) {
99     SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
100     new (SD) SymbolRegionValue(SymbolCounter, R);
101     DataSet.InsertNode(SD, InsertPos);
102     ++SymbolCounter;
103   }
104 
105   return cast<SymbolRegionValue>(SD);
106 }
107 
108 const SymbolConjured*
109 SymbolManager::getConjuredSymbol(const Stmt *E, QualType T, unsigned Count,
110                                  const void *SymbolTag) {
111 
112   llvm::FoldingSetNodeID profile;
113   SymbolConjured::Profile(profile, E, T, Count, SymbolTag);
114   void *InsertPos;
115   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
116   if (!SD) {
117     SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
118     new (SD) SymbolConjured(SymbolCounter, E, T, Count, SymbolTag);
119     DataSet.InsertNode(SD, InsertPos);
120     ++SymbolCounter;
121   }
122 
123   return cast<SymbolConjured>(SD);
124 }
125 
126 const SymbolDerived*
127 SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
128                                 const TypedValueRegion *R) {
129 
130   llvm::FoldingSetNodeID profile;
131   SymbolDerived::Profile(profile, parentSymbol, R);
132   void *InsertPos;
133   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
134   if (!SD) {
135     SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
136     new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
137     DataSet.InsertNode(SD, InsertPos);
138     ++SymbolCounter;
139   }
140 
141   return cast<SymbolDerived>(SD);
142 }
143 
144 const SymbolExtent*
145 SymbolManager::getExtentSymbol(const SubRegion *R) {
146   llvm::FoldingSetNodeID profile;
147   SymbolExtent::Profile(profile, R);
148   void *InsertPos;
149   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
150   if (!SD) {
151     SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
152     new (SD) SymbolExtent(SymbolCounter, R);
153     DataSet.InsertNode(SD, InsertPos);
154     ++SymbolCounter;
155   }
156 
157   return cast<SymbolExtent>(SD);
158 }
159 
160 const SymbolMetadata*
161 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
162                                  unsigned Count, const void *SymbolTag) {
163 
164   llvm::FoldingSetNodeID profile;
165   SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
166   void *InsertPos;
167   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
168   if (!SD) {
169     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
170     new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
171     DataSet.InsertNode(SD, InsertPos);
172     ++SymbolCounter;
173   }
174 
175   return cast<SymbolMetadata>(SD);
176 }
177 
178 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
179                                                BinaryOperator::Opcode op,
180                                                const llvm::APSInt& v,
181                                                QualType t) {
182   llvm::FoldingSetNodeID ID;
183   SymIntExpr::Profile(ID, lhs, op, v, t);
184   void *InsertPos;
185   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
186 
187   if (!data) {
188     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
189     new (data) SymIntExpr(lhs, op, v, t);
190     DataSet.InsertNode(data, InsertPos);
191   }
192 
193   return cast<SymIntExpr>(data);
194 }
195 
196 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
197                                                BinaryOperator::Opcode op,
198                                                const SymExpr *rhs,
199                                                QualType t) {
200   llvm::FoldingSetNodeID ID;
201   SymSymExpr::Profile(ID, lhs, op, rhs, t);
202   void *InsertPos;
203   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
204 
205   if (!data) {
206     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
207     new (data) SymSymExpr(lhs, op, rhs, t);
208     DataSet.InsertNode(data, InsertPos);
209   }
210 
211   return cast<SymSymExpr>(data);
212 }
213 
214 QualType SymbolConjured::getType(ASTContext&) const {
215   return T;
216 }
217 
218 QualType SymbolDerived::getType(ASTContext &Ctx) const {
219   return R->getValueType();
220 }
221 
222 QualType SymbolExtent::getType(ASTContext &Ctx) const {
223   return Ctx.getSizeType();
224 }
225 
226 QualType SymbolMetadata::getType(ASTContext&) const {
227   return T;
228 }
229 
230 QualType SymbolRegionValue::getType(ASTContext &C) const {
231   return R->getValueType();
232 }
233 
234 SymbolManager::~SymbolManager() {
235   for (SymbolDependTy::const_iterator I = SymbolDependencies.begin(),
236        E = SymbolDependencies.end(); I != E; ++I) {
237     delete I->second;
238   }
239 
240 }
241 
242 bool SymbolManager::canSymbolicate(QualType T) {
243   T = T.getCanonicalType();
244 
245   if (Loc::isLocType(T))
246     return true;
247 
248   if (T->isIntegerType())
249     return T->isScalarType();
250 
251   if (T->isRecordType() && !T->isUnionType())
252     return true;
253 
254   return false;
255 }
256 
257 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
258                                         const SymbolRef Dependent) {
259   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
260   SymbolRefSmallVectorTy *dependencies = 0;
261   if (I == SymbolDependencies.end()) {
262     dependencies = new SymbolRefSmallVectorTy();
263     SymbolDependencies[Primary] = dependencies;
264   } else {
265     dependencies = I->second;
266   }
267   dependencies->push_back(Dependent);
268 }
269 
270 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
271                                                      const SymbolRef Primary) {
272   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
273   if (I == SymbolDependencies.end())
274     return 0;
275   return I->second;
276 }
277 
278 void SymbolReaper::markDependentsLive(SymbolRef sym) {
279   // Do not mark dependents more then once.
280   SymbolMapTy::iterator LI = TheLiving.find(sym);
281   assert(LI != TheLiving.end() && "The primary symbol is not live.");
282   if (LI->second == HaveMarkedDependents)
283     return;
284   LI->second = HaveMarkedDependents;
285 
286   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
287     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
288                                                 E = Deps->end(); I != E; ++I) {
289       if (TheLiving.find(*I) != TheLiving.end())
290         continue;
291       markLive(*I);
292     }
293   }
294 }
295 
296 void SymbolReaper::markLive(SymbolRef sym) {
297   TheLiving[sym] = NotProcessed;
298   TheDead.erase(sym);
299   markDependentsLive(sym);
300 }
301 
302 void SymbolReaper::markLive(const MemRegion *region) {
303   RegionRoots.insert(region);
304 }
305 
306 void SymbolReaper::markInUse(SymbolRef sym) {
307   if (isa<SymbolMetadata>(sym))
308     MetadataInUse.insert(sym);
309 }
310 
311 bool SymbolReaper::maybeDead(SymbolRef sym) {
312   if (isLive(sym))
313     return false;
314 
315   TheDead.insert(sym);
316   return true;
317 }
318 
319 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
320   if (RegionRoots.count(MR))
321     return true;
322 
323   MR = MR->getBaseRegion();
324 
325   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
326     return isLive(SR->getSymbol());
327 
328   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
329     return isLive(VR, true);
330 
331   // FIXME: This is a gross over-approximation. What we really need is a way to
332   // tell if anything still refers to this region. Unlike SymbolicRegions,
333   // AllocaRegions don't have associated symbols, though, so we don't actually
334   // have a way to track their liveness.
335   if (isa<AllocaRegion>(MR))
336     return true;
337 
338   if (isa<CXXThisRegion>(MR))
339     return true;
340 
341   if (isa<MemSpaceRegion>(MR))
342     return true;
343 
344   return false;
345 }
346 
347 bool SymbolReaper::isLive(SymbolRef sym) {
348   if (TheLiving.count(sym)) {
349     markDependentsLive(sym);
350     return true;
351   }
352 
353   if (const SymbolDerived *derived = dyn_cast<SymbolDerived>(sym)) {
354     if (isLive(derived->getParentSymbol())) {
355       markLive(sym);
356       return true;
357     }
358     return false;
359   }
360 
361   if (const SymbolExtent *extent = dyn_cast<SymbolExtent>(sym)) {
362     if (isLiveRegion(extent->getRegion())) {
363       markLive(sym);
364       return true;
365     }
366     return false;
367   }
368 
369   if (const SymbolMetadata *metadata = dyn_cast<SymbolMetadata>(sym)) {
370     if (MetadataInUse.count(sym)) {
371       if (isLiveRegion(metadata->getRegion())) {
372         markLive(sym);
373         MetadataInUse.erase(sym);
374         return true;
375       }
376     }
377     return false;
378   }
379 
380   // Interogate the symbol.  It may derive from an input value to
381   // the analyzed function/method.
382   return isa<SymbolRegionValue>(sym);
383 }
384 
385 bool SymbolReaper::isLive(const Stmt *ExprVal) const {
386   return LCtx->getAnalysisContext()->getRelaxedLiveVariables()->
387       isLive(Loc, ExprVal);
388 }
389 
390 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
391   const StackFrameContext *VarContext = VR->getStackFrame();
392   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
393 
394   if (VarContext == CurrentContext) {
395     if (LCtx->getAnalysisContext()->getRelaxedLiveVariables()->
396           isLive(Loc, VR->getDecl()))
397       return true;
398 
399     if (!includeStoreBindings)
400       return false;
401 
402     unsigned &cachedQuery =
403       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
404 
405     if (cachedQuery) {
406       return cachedQuery == 1;
407     }
408 
409     // Query the store to see if the region occurs in any live bindings.
410     if (Store store = reapedStore.getStore()) {
411       bool hasRegion =
412         reapedStore.getStoreManager().includedInBindings(store, VR);
413       cachedQuery = hasRegion ? 1 : 2;
414       return hasRegion;
415     }
416 
417     return false;
418   }
419 
420   return VarContext->isParentOf(CurrentContext);
421 }
422 
423 SymbolVisitor::~SymbolVisitor() {}
424