UninitializedValues.cpp revision de091aeb4658e986ed8fa5fbce7ab35ef2ae26ec 
1//==- UninitializedValues.cpp - Find Uninitialized 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 implements uninitialized values analysis for source-level CFGs.
11//
12//===----------------------------------------------------------------------===//
13
14#include <utility>
15#include "llvm/ADT/Optional.h"
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/ADT/PackedVector.h"
18#include "llvm/ADT/DenseMap.h"
19#include "clang/AST/Decl.h"
20#include "clang/Analysis/CFG.h"
21#include "clang/Analysis/AnalysisContext.h"
22#include "clang/Analysis/Visitors/CFGRecStmtDeclVisitor.h"
23#include "clang/Analysis/Analyses/UninitializedValues.h"
24#include "clang/Analysis/Support/SaveAndRestore.h"
25
26using namespace clang;
27
28static bool isTrackedVar(const VarDecl *vd, const DeclContext *dc) {
29  if (vd->isLocalVarDecl() && !vd->hasGlobalStorage() &&
30      !vd->isExceptionVariable() &&
31      vd->getDeclContext() == dc) {
32    QualType ty = vd->getType();
33    return ty->isScalarType() || ty->isVectorType();
34  }
35  return false;
36}
37
38//------------------------------------------------------------------------====//
39// DeclToIndex: a mapping from Decls we track to value indices.
40//====------------------------------------------------------------------------//
41
42namespace {
43class DeclToIndex {
44  llvm::DenseMap<const VarDecl *, unsigned> map;
45public:
46  DeclToIndex() {}
47
48  /// Compute the actual mapping from declarations to bits.
49  void computeMap(const DeclContext &dc);
50
51  /// Return the number of declarations in the map.
52  unsigned size() const { return map.size(); }
53
54  /// Returns the bit vector index for a given declaration.
55  llvm::Optional<unsigned> getValueIndex(const VarDecl *d) const;
56};
57}
58
59void DeclToIndex::computeMap(const DeclContext &dc) {
60  unsigned count = 0;
61  DeclContext::specific_decl_iterator<VarDecl> I(dc.decls_begin()),
62                                               E(dc.decls_end());
63  for ( ; I != E; ++I) {
64    const VarDecl *vd = *I;
65    if (isTrackedVar(vd, &dc))
66      map[vd] = count++;
67  }
68}
69
70llvm::Optional<unsigned> DeclToIndex::getValueIndex(const VarDecl *d) const {
71  llvm::DenseMap<const VarDecl *, unsigned>::const_iterator I = map.find(d);
72  if (I == map.end())
73    return llvm::Optional<unsigned>();
74  return I->second;
75}
76
77//------------------------------------------------------------------------====//
78// CFGBlockValues: dataflow values for CFG blocks.
79//====------------------------------------------------------------------------//
80
81// These values are defined in such a way that a merge can be done using
82// a bitwise OR.
83enum Value { Unknown = 0x0,         /* 00 */
84             Initialized = 0x1,     /* 01 */
85             Uninitialized = 0x2,   /* 10 */
86             MayUninitialized = 0x3 /* 11 */ };
87
88static bool isUninitialized(const Value v) {
89  return v >= Uninitialized;
90}
91static bool isAlwaysUninit(const Value v) {
92  return v == Uninitialized;
93}
94
95namespace {
96
97typedef llvm::PackedVector<Value, 2> ValueVector;
98typedef std::pair<ValueVector *, ValueVector *> BVPair;
99
100class CFGBlockValues {
101  const CFG &cfg;
102  BVPair *vals;
103  ValueVector scratch;
104  DeclToIndex declToIndex;
105
106  ValueVector &lazyCreate(ValueVector *&bv);
107public:
108  CFGBlockValues(const CFG &cfg);
109  ~CFGBlockValues();
110
111  unsigned getNumEntries() const { return declToIndex.size(); }
112
113  void computeSetOfDeclarations(const DeclContext &dc);
114  ValueVector &getValueVector(const CFGBlock *block,
115                                const CFGBlock *dstBlock);
116
117  BVPair &getValueVectors(const CFGBlock *block, bool shouldLazyCreate);
118
119  void mergeIntoScratch(ValueVector const &source, bool isFirst);
120  bool updateValueVectorWithScratch(const CFGBlock *block);
121  bool updateValueVectors(const CFGBlock *block, const BVPair &newVals);
122
123  bool hasNoDeclarations() const {
124    return declToIndex.size() == 0;
125  }
126
127  bool hasEntry(const VarDecl *vd) const {
128    return declToIndex.getValueIndex(vd).hasValue();
129  }
130
131  bool hasValues(const CFGBlock *block);
132
133  void resetScratch();
134  ValueVector &getScratch() { return scratch; }
135
136  ValueVector::reference operator[](const VarDecl *vd);
137};
138} // end anonymous namespace
139
140CFGBlockValues::CFGBlockValues(const CFG &c) : cfg(c), vals(0) {
141  unsigned n = cfg.getNumBlockIDs();
142  if (!n)
143    return;
144  vals = new std::pair<ValueVector*, ValueVector*>[n];
145  memset((void*)vals, 0, sizeof(*vals) * n);
146}
147
148CFGBlockValues::~CFGBlockValues() {
149  unsigned n = cfg.getNumBlockIDs();
150  if (n == 0)
151    return;
152  for (unsigned i = 0; i < n; ++i) {
153    delete vals[i].first;
154    delete vals[i].second;
155  }
156  delete [] vals;
157}
158
159void CFGBlockValues::computeSetOfDeclarations(const DeclContext &dc) {
160  declToIndex.computeMap(dc);
161  scratch.resize(declToIndex.size());
162}
163
164ValueVector &CFGBlockValues::lazyCreate(ValueVector *&bv) {
165  if (!bv)
166    bv = new ValueVector(declToIndex.size());
167  return *bv;
168}
169
170/// This function pattern matches for a '&&' or '||' that appears at
171/// the beginning of a CFGBlock that also (1) has a terminator and
172/// (2) has no other elements.  If such an expression is found, it is returned.
173static BinaryOperator *getLogicalOperatorInChain(const CFGBlock *block) {
174  if (block->empty())
175    return 0;
176
177  const CFGStmt *cstmt = block->front().getAs<CFGStmt>();
178  if (!cstmt)
179    return 0;
180
181  BinaryOperator *b = dyn_cast_or_null<BinaryOperator>(cstmt->getStmt());
182
183  if (!b || !b->isLogicalOp())
184    return 0;
185
186  if (block->pred_size() == 2) {
187    if (block->getTerminatorCondition() == b) {
188      if (block->succ_size() == 2)
189      return b;
190    }
191    else if (block->size() == 1)
192      return b;
193  }
194
195  return 0;
196}
197
198ValueVector &CFGBlockValues::getValueVector(const CFGBlock *block,
199                                            const CFGBlock *dstBlock) {
200  unsigned idx = block->getBlockID();
201  if (dstBlock && getLogicalOperatorInChain(block)) {
202    if (*block->succ_begin() == dstBlock)
203      return lazyCreate(vals[idx].first);
204    assert(*(block->succ_begin()+1) == dstBlock);
205    return lazyCreate(vals[idx].second);
206  }
207
208  assert(vals[idx].second == 0);
209  return lazyCreate(vals[idx].first);
210}
211
212bool CFGBlockValues::hasValues(const CFGBlock *block) {
213  unsigned idx = block->getBlockID();
214  return vals[idx].second != 0;
215}
216
217BVPair &CFGBlockValues::getValueVectors(const clang::CFGBlock *block,
218                                        bool shouldLazyCreate) {
219  unsigned idx = block->getBlockID();
220  lazyCreate(vals[idx].first);
221  if (shouldLazyCreate)
222    lazyCreate(vals[idx].second);
223  return vals[idx];
224}
225
226void CFGBlockValues::mergeIntoScratch(ValueVector const &source,
227                                      bool isFirst) {
228  if (isFirst)
229    scratch = source;
230  else
231    scratch |= source;
232}
233#if 0
234static void printVector(const CFGBlock *block, ValueVector &bv,
235                        unsigned num) {
236
237  llvm::errs() << block->getBlockID() << " :";
238  for (unsigned i = 0; i < bv.size(); ++i) {
239    llvm::errs() << ' ' << bv[i];
240  }
241  llvm::errs() << " : " << num << '\n';
242}
243#endif
244
245bool CFGBlockValues::updateValueVectorWithScratch(const CFGBlock *block) {
246  ValueVector &dst = getValueVector(block, 0);
247  bool changed = (dst != scratch);
248  if (changed)
249    dst = scratch;
250#if 0
251  printVector(block, scratch, 0);
252#endif
253  return changed;
254}
255
256bool CFGBlockValues::updateValueVectors(const CFGBlock *block,
257                                      const BVPair &newVals) {
258  BVPair &vals = getValueVectors(block, true);
259  bool changed = *newVals.first != *vals.first ||
260                 *newVals.second != *vals.second;
261  *vals.first = *newVals.first;
262  *vals.second = *newVals.second;
263#if 0
264  printVector(block, *vals.first, 1);
265  printVector(block, *vals.second, 2);
266#endif
267  return changed;
268}
269
270void CFGBlockValues::resetScratch() {
271  scratch.reset();
272}
273
274ValueVector::reference CFGBlockValues::operator[](const VarDecl *vd) {
275  const llvm::Optional<unsigned> &idx = declToIndex.getValueIndex(vd);
276  assert(idx.hasValue());
277  return scratch[idx.getValue()];
278}
279
280//------------------------------------------------------------------------====//
281// Worklist: worklist for dataflow analysis.
282//====------------------------------------------------------------------------//
283
284namespace {
285class DataflowWorklist {
286  SmallVector<const CFGBlock *, 20> worklist;
287  llvm::BitVector enqueuedBlocks;
288public:
289  DataflowWorklist(const CFG &cfg) : enqueuedBlocks(cfg.getNumBlockIDs()) {}
290
291  void enqueueSuccessors(const CFGBlock *block);
292  const CFGBlock *dequeue();
293};
294}
295
296void DataflowWorklist::enqueueSuccessors(const clang::CFGBlock *block) {
297  unsigned OldWorklistSize = worklist.size();
298  for (CFGBlock::const_succ_iterator I = block->succ_begin(),
299       E = block->succ_end(); I != E; ++I) {
300    const CFGBlock *Successor = *I;
301    if (!Successor || enqueuedBlocks[Successor->getBlockID()])
302      continue;
303    worklist.push_back(Successor);
304    enqueuedBlocks[Successor->getBlockID()] = true;
305  }
306  if (OldWorklistSize == 0 || OldWorklistSize == worklist.size())
307    return;
308
309  // Rotate the newly added blocks to the start of the worklist so that it forms
310  // a proper queue when we pop off the end of the worklist.
311  std::rotate(worklist.begin(), worklist.begin() + OldWorklistSize,
312              worklist.end());
313}
314
315const CFGBlock *DataflowWorklist::dequeue() {
316  if (worklist.empty())
317    return 0;
318  const CFGBlock *b = worklist.back();
319  worklist.pop_back();
320  enqueuedBlocks[b->getBlockID()] = false;
321  return b;
322}
323
324//------------------------------------------------------------------------====//
325// Transfer function for uninitialized values analysis.
326//====------------------------------------------------------------------------//
327
328namespace {
329class FindVarResult {
330  const VarDecl *vd;
331  const DeclRefExpr *dr;
332public:
333  FindVarResult(VarDecl *vd, DeclRefExpr *dr) : vd(vd), dr(dr) {}
334
335  const DeclRefExpr *getDeclRefExpr() const { return dr; }
336  const VarDecl *getDecl() const { return vd; }
337};
338
339class TransferFunctions : public StmtVisitor<TransferFunctions> {
340  CFGBlockValues &vals;
341  const CFG &cfg;
342  AnalysisContext &ac;
343  UninitVariablesHandler *handler;
344  const bool flagBlockUses;
345
346  /// The last DeclRefExpr seen when analyzing a block.  Used to
347  /// cheat when detecting cases when the address of a variable is taken.
348  DeclRefExpr *lastDR;
349
350  /// The last lvalue-to-rvalue conversion of a variable whose value
351  /// was uninitialized.  Normally this results in a warning, but it is
352  /// possible to either silence the warning in some cases, or we
353  /// propagate the uninitialized value.
354  CastExpr *lastLoad;
355
356  /// For some expressions, we want to ignore any post-processing after
357  /// visitation.
358  bool skipProcessUses;
359
360public:
361  TransferFunctions(CFGBlockValues &vals, const CFG &cfg,
362                    AnalysisContext &ac,
363                    UninitVariablesHandler *handler,
364                    bool flagBlockUses)
365    : vals(vals), cfg(cfg), ac(ac), handler(handler),
366      flagBlockUses(flagBlockUses), lastDR(0), lastLoad(0),
367      skipProcessUses(false) {}
368
369  const CFG &getCFG() { return cfg; }
370  void reportUninit(const DeclRefExpr *ex, const VarDecl *vd,
371                    bool isAlwaysUninit);
372
373  void VisitBlockExpr(BlockExpr *be);
374  void VisitDeclStmt(DeclStmt *ds);
375  void VisitDeclRefExpr(DeclRefExpr *dr);
376  void VisitUnaryOperator(UnaryOperator *uo);
377  void VisitBinaryOperator(BinaryOperator *bo);
378  void VisitCastExpr(CastExpr *ce);
379  void VisitObjCForCollectionStmt(ObjCForCollectionStmt *fs);
380  void Visit(Stmt *s);
381
382  bool isTrackedVar(const VarDecl *vd) {
383    return ::isTrackedVar(vd, cast<DeclContext>(ac.getDecl()));
384  }
385
386  FindVarResult findBlockVarDecl(Expr *ex);
387
388  void ProcessUses(Stmt *s = 0);
389};
390}
391
392static const Expr *stripCasts(ASTContext &C, const Expr *Ex) {
393  while (Ex) {
394    Ex = Ex->IgnoreParenNoopCasts(C);
395    if (const CastExpr *CE = dyn_cast<CastExpr>(Ex)) {
396      if (CE->getCastKind() == CK_LValueBitCast) {
397        Ex = CE->getSubExpr();
398        continue;
399      }
400    }
401    break;
402  }
403  return Ex;
404}
405
406void TransferFunctions::reportUninit(const DeclRefExpr *ex,
407                                     const VarDecl *vd, bool isAlwaysUnit) {
408  if (handler) handler->handleUseOfUninitVariable(ex, vd, isAlwaysUnit);
409}
410
411FindVarResult TransferFunctions::findBlockVarDecl(Expr* ex) {
412  if (DeclRefExpr* dr = dyn_cast<DeclRefExpr>(ex->IgnoreParenCasts()))
413    if (VarDecl *vd = dyn_cast<VarDecl>(dr->getDecl()))
414      if (isTrackedVar(vd))
415        return FindVarResult(vd, dr);
416  return FindVarResult(0, 0);
417}
418
419void TransferFunctions::VisitObjCForCollectionStmt(ObjCForCollectionStmt *fs) {
420  // This represents an initialization of the 'element' value.
421  Stmt *element = fs->getElement();
422  const VarDecl* vd = 0;
423
424  if (DeclStmt* ds = dyn_cast<DeclStmt>(element)) {
425    vd = cast<VarDecl>(ds->getSingleDecl());
426    if (!isTrackedVar(vd))
427      vd = 0;
428  }
429  else {
430    // Initialize the value of the reference variable.
431    const FindVarResult &res = findBlockVarDecl(cast<Expr>(element));
432    vd = res.getDecl();
433  }
434
435  if (vd)
436    vals[vd] = Initialized;
437}
438
439void TransferFunctions::VisitBlockExpr(BlockExpr *be) {
440  if (!flagBlockUses || !handler)
441    return;
442  const BlockDecl *bd = be->getBlockDecl();
443  for (BlockDecl::capture_const_iterator i = bd->capture_begin(),
444        e = bd->capture_end() ; i != e; ++i) {
445    const VarDecl *vd = i->getVariable();
446    if (!vd->hasLocalStorage())
447      continue;
448    if (!isTrackedVar(vd))
449      continue;
450    if (i->isByRef()) {
451      vals[vd] = Initialized;
452      continue;
453    }
454    Value v = vals[vd];
455    if (isUninitialized(v))
456      handler->handleUseOfUninitVariable(be, vd, isAlwaysUninit(v));
457  }
458}
459
460void TransferFunctions::VisitDeclRefExpr(DeclRefExpr *dr) {
461  // Record the last DeclRefExpr seen.  This is an lvalue computation.
462  // We use this value to later detect if a variable "escapes" the analysis.
463  if (const VarDecl *vd = dyn_cast<VarDecl>(dr->getDecl()))
464    if (isTrackedVar(vd)) {
465      ProcessUses();
466      lastDR = dr;
467    }
468}
469
470void TransferFunctions::VisitDeclStmt(DeclStmt *ds) {
471  for (DeclStmt::decl_iterator DI = ds->decl_begin(), DE = ds->decl_end();
472       DI != DE; ++DI) {
473    if (VarDecl *vd = dyn_cast<VarDecl>(*DI)) {
474      if (isTrackedVar(vd)) {
475        if (Expr *init = vd->getInit()) {
476          // If the initializer consists solely of a reference to itself, we
477          // explicitly mark the variable as uninitialized. This allows code
478          // like the following:
479          //
480          //   int x = x;
481          //
482          // to deliberately leave a variable uninitialized. Different analysis
483          // clients can detect this pattern and adjust their reporting
484          // appropriately, but we need to continue to analyze subsequent uses
485          // of the variable.
486          if (init == lastLoad) {
487            const DeclRefExpr *DR
488              = cast<DeclRefExpr>(stripCasts(ac.getASTContext(),
489                                             lastLoad->getSubExpr()));
490            if (DR->getDecl() == vd) {
491              // int x = x;
492              // Propagate uninitialized value, but don't immediately report
493              // a problem.
494              vals[vd] = Uninitialized;
495              lastLoad = 0;
496              lastDR = 0;
497              return;
498            }
499          }
500
501          // All other cases: treat the new variable as initialized.
502          vals[vd] = Initialized;
503        }
504      }
505    }
506  }
507}
508
509void TransferFunctions::VisitBinaryOperator(clang::BinaryOperator *bo) {
510  if (bo->isAssignmentOp()) {
511    const FindVarResult &res = findBlockVarDecl(bo->getLHS());
512    if (const VarDecl* vd = res.getDecl()) {
513      ValueVector::reference val = vals[vd];
514      if (isUninitialized(val)) {
515        if (bo->getOpcode() != BO_Assign)
516          reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
517        else
518          val = Initialized;
519      }
520    }
521  }
522}
523
524void TransferFunctions::VisitUnaryOperator(clang::UnaryOperator *uo) {
525  switch (uo->getOpcode()) {
526    case clang::UO_PostDec:
527    case clang::UO_PostInc:
528    case clang::UO_PreDec:
529    case clang::UO_PreInc: {
530      const FindVarResult &res = findBlockVarDecl(uo->getSubExpr());
531      if (const VarDecl *vd = res.getDecl()) {
532        assert(res.getDeclRefExpr() == lastDR);
533        // We null out lastDR to indicate we have fully processed it
534        // and we don't want the auto-value setting in Visit().
535        lastDR = 0;
536
537        ValueVector::reference val = vals[vd];
538        if (isUninitialized(val))
539          reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
540      }
541      break;
542    }
543    default:
544      break;
545  }
546}
547
548void TransferFunctions::VisitCastExpr(clang::CastExpr *ce) {
549  if (ce->getCastKind() == CK_LValueToRValue) {
550    const FindVarResult &res = findBlockVarDecl(ce->getSubExpr());
551    if (const VarDecl *vd = res.getDecl()) {
552      assert(res.getDeclRefExpr() == lastDR);
553      if (isUninitialized(vals[vd])) {
554        // Record this load of an uninitialized value.  Normally this
555        // results in a warning, but we delay reporting the issue
556        // in case it is wrapped in a void cast, etc.
557        lastLoad = ce;
558      }
559    }
560  }
561  else if (ce->getCastKind() == CK_NoOp ||
562           ce->getCastKind() == CK_LValueBitCast) {
563    skipProcessUses = true;
564  }
565  else if (CStyleCastExpr *cse = dyn_cast<CStyleCastExpr>(ce)) {
566    if (cse->getType()->isVoidType()) {
567      // e.g. (void) x;
568      if (lastLoad == cse->getSubExpr()) {
569        // Squelch any detected load of an uninitialized value if
570        // we cast it to void.
571        lastLoad = 0;
572        lastDR = 0;
573      }
574    }
575  }
576}
577
578void TransferFunctions::Visit(clang::Stmt *s) {
579  skipProcessUses = false;
580  StmtVisitor<TransferFunctions>::Visit(s);
581  if (!skipProcessUses)
582    ProcessUses(s);
583}
584
585void TransferFunctions::ProcessUses(Stmt *s) {
586  // This method is typically called after visiting a CFGElement statement
587  // in the CFG.  We delay processing of reporting many loads of uninitialized
588  // values until here.
589  if (lastLoad) {
590    // If we just visited the lvalue-to-rvalue cast, there is nothing
591    // left to do.
592    if (lastLoad == s)
593      return;
594
595    // If we reach here, we have seen a load of an uninitialized value
596    // and it hasn't been casted to void or otherwise handled.  In this
597    // situation, report the incident.
598    const DeclRefExpr *DR =
599      cast<DeclRefExpr>(stripCasts(ac.getASTContext(),
600                                   lastLoad->getSubExpr()));
601    const VarDecl *VD = cast<VarDecl>(DR->getDecl());
602    reportUninit(DR, VD, isAlwaysUninit(vals[VD]));
603    lastLoad = 0;
604
605    if (DR == lastDR) {
606      lastDR = 0;
607      return;
608    }
609  }
610
611  // Any other uses of 'lastDR' involve taking an lvalue of variable.
612  // In this case, it "escapes" the analysis.
613  if (lastDR && lastDR != s) {
614    vals[cast<VarDecl>(lastDR->getDecl())] = Initialized;
615    lastDR = 0;
616  }
617}
618
619//------------------------------------------------------------------------====//
620// High-level "driver" logic for uninitialized values analysis.
621//====------------------------------------------------------------------------//
622
623static bool runOnBlock(const CFGBlock *block, const CFG &cfg,
624                       AnalysisContext &ac, CFGBlockValues &vals,
625                       llvm::BitVector &wasAnalyzed,
626                       UninitVariablesHandler *handler = 0,
627                       bool flagBlockUses = false) {
628
629  wasAnalyzed[block->getBlockID()] = true;
630
631  if (const BinaryOperator *b = getLogicalOperatorInChain(block)) {
632    CFGBlock::const_pred_iterator itr = block->pred_begin();
633    BVPair vA = vals.getValueVectors(*itr, false);
634    ++itr;
635    BVPair vB = vals.getValueVectors(*itr, false);
636
637    BVPair valsAB;
638
639    if (b->getOpcode() == BO_LAnd) {
640      // Merge the 'F' bits from the first and second.
641      vals.mergeIntoScratch(*(vA.second ? vA.second : vA.first), true);
642      vals.mergeIntoScratch(*(vB.second ? vB.second : vB.first), false);
643      valsAB.first = vA.first;
644      valsAB.second = &vals.getScratch();
645    }
646    else {
647      // Merge the 'T' bits from the first and second.
648      assert(b->getOpcode() == BO_LOr);
649      vals.mergeIntoScratch(*vA.first, true);
650      vals.mergeIntoScratch(*vB.first, false);
651      valsAB.first = &vals.getScratch();
652      valsAB.second = vA.second ? vA.second : vA.first;
653    }
654    return vals.updateValueVectors(block, valsAB);
655  }
656
657  // Default behavior: merge in values of predecessor blocks.
658  vals.resetScratch();
659  bool isFirst = true;
660  for (CFGBlock::const_pred_iterator I = block->pred_begin(),
661       E = block->pred_end(); I != E; ++I) {
662    vals.mergeIntoScratch(vals.getValueVector(*I, block), isFirst);
663    isFirst = false;
664  }
665  // Apply the transfer function.
666  TransferFunctions tf(vals, cfg, ac, handler, flagBlockUses);
667  for (CFGBlock::const_iterator I = block->begin(), E = block->end();
668       I != E; ++I) {
669    if (const CFGStmt *cs = dyn_cast<CFGStmt>(&*I)) {
670      tf.Visit(cs->getStmt());
671    }
672  }
673  tf.ProcessUses();
674  return vals.updateValueVectorWithScratch(block);
675}
676
677void clang::runUninitializedVariablesAnalysis(
678    const DeclContext &dc,
679    const CFG &cfg,
680    AnalysisContext &ac,
681    UninitVariablesHandler &handler,
682    UninitVariablesAnalysisStats &stats) {
683  CFGBlockValues vals(cfg);
684  vals.computeSetOfDeclarations(dc);
685  if (vals.hasNoDeclarations())
686    return;
687
688  stats.NumVariablesAnalyzed = vals.getNumEntries();
689
690  // Mark all variables uninitialized at the entry.
691  const CFGBlock &entry = cfg.getEntry();
692  for (CFGBlock::const_succ_iterator i = entry.succ_begin(),
693        e = entry.succ_end(); i != e; ++i) {
694    if (const CFGBlock *succ = *i) {
695      ValueVector &vec = vals.getValueVector(&entry, succ);
696      const unsigned n = vals.getNumEntries();
697      for (unsigned j = 0; j < n ; ++j) {
698        vec[j] = Uninitialized;
699      }
700    }
701  }
702
703  // Proceed with the workist.
704  DataflowWorklist worklist(cfg);
705  llvm::BitVector previouslyVisited(cfg.getNumBlockIDs());
706  worklist.enqueueSuccessors(&cfg.getEntry());
707  llvm::BitVector wasAnalyzed(cfg.getNumBlockIDs(), false);
708
709  while (const CFGBlock *block = worklist.dequeue()) {
710    // Did the block change?
711    bool changed = runOnBlock(block, cfg, ac, vals, wasAnalyzed);
712    ++stats.NumBlockVisits;
713    if (changed || !previouslyVisited[block->getBlockID()])
714      worklist.enqueueSuccessors(block);
715    previouslyVisited[block->getBlockID()] = true;
716  }
717
718  // Run through the blocks one more time, and report uninitialized variabes.
719  for (CFG::const_iterator BI = cfg.begin(), BE = cfg.end(); BI != BE; ++BI) {
720    if (wasAnalyzed[(*BI)->getBlockID()]) {
721      runOnBlock(*BI, cfg, ac, vals, wasAnalyzed, &handler,
722                 /* flagBlockUses */ true);
723      ++stats.NumBlockVisits;
724    }
725  }
726}
727
728UninitVariablesHandler::~UninitVariablesHandler() {}
729