UninitializedValues.cpp revision 4ddb3871307376d27d0f276c9da0ecce0384f01f 
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/BitVector.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  return vd->isLocalVarDecl() && !vd->hasGlobalStorage() &&
30         vd->getType()->isScalarType() &&
31         vd->getDeclContext() == dc;
32}
33
34//------------------------------------------------------------------------====//
35// DeclToIndex: a mapping from Decls we track to value indices.
36//====------------------------------------------------------------------------//
37
38namespace {
39class DeclToIndex {
40  llvm::DenseMap<const VarDecl *, unsigned> map;
41public:
42  DeclToIndex() {}
43
44  /// Compute the actual mapping from declarations to bits.
45  void computeMap(const DeclContext &dc);
46
47  /// Return the number of declarations in the map.
48  unsigned size() const { return map.size(); }
49
50  /// Returns the bit vector index for a given declaration.
51  llvm::Optional<unsigned> getValueIndex(const VarDecl *d);
52};
53}
54
55void DeclToIndex::computeMap(const DeclContext &dc) {
56  unsigned count = 0;
57  DeclContext::specific_decl_iterator<VarDecl> I(dc.decls_begin()),
58                                               E(dc.decls_end());
59  for ( ; I != E; ++I) {
60    const VarDecl *vd = *I;
61    if (isTrackedVar(vd, &dc))
62      map[vd] = count++;
63  }
64}
65
66llvm::Optional<unsigned> DeclToIndex::getValueIndex(const VarDecl *d) {
67  llvm::DenseMap<const VarDecl *, unsigned>::iterator I = map.find(d);
68  if (I == map.end())
69    return llvm::Optional<unsigned>();
70  return I->second;
71}
72
73//------------------------------------------------------------------------====//
74// CFGBlockValues: dataflow values for CFG blocks.
75//====------------------------------------------------------------------------//
76
77// These values are defined in such a way that a merge can be done using
78// a bitwise OR.
79enum Value { Unknown = 0x0,         /* 00 */
80             Initialized = 0x1,     /* 01 */
81             Uninitialized = 0x2,   /* 10 */
82             MayUninitialized = 0x3 /* 11 */ };
83
84static bool isUninitialized(const Value v) {
85  return v >= Uninitialized;
86}
87static bool isAlwaysUninit(const Value v) {
88  return v == Uninitialized;
89}
90
91class ValueVector {
92  llvm::BitVector vec;
93public:
94  ValueVector() {}
95  ValueVector(unsigned size) : vec(size << 1) {}
96  void resize(unsigned n) { vec.resize(n << 1); }
97  void merge(const ValueVector &rhs) { vec |= rhs.vec; }
98  bool operator!=(const ValueVector &rhs) const { return vec != rhs.vec; }
99  void reset() { vec.reset(); }
100
101  class reference {
102    ValueVector &vv;
103    const unsigned idx;
104
105    reference();  // Undefined
106  public:
107    reference(ValueVector &vv, unsigned idx) : vv(vv), idx(idx) {}
108    ~reference() {}
109
110    reference &operator=(Value v) {
111      vv.vec[idx << 1] = (((unsigned) v) & 0x1) ? true : false;
112      vv.vec[(idx << 1) | 1] = (((unsigned) v) & 0x2) ? true : false;
113      return *this;
114    }
115    operator Value() {
116      unsigned x = (vv.vec[idx << 1] ? 1 : 0) | (vv.vec[(idx << 1) | 1] ? 2 :0);
117      return (Value) x;
118    }
119  };
120
121  reference operator[](unsigned idx) { return reference(*this, idx); }
122};
123
124typedef std::pair<ValueVector *, ValueVector *> BVPair;
125
126namespace {
127class CFGBlockValues {
128  const CFG &cfg;
129  BVPair *vals;
130  ValueVector scratch;
131  DeclToIndex declToIndex;
132
133  ValueVector &lazyCreate(ValueVector *&bv);
134public:
135  CFGBlockValues(const CFG &cfg);
136  ~CFGBlockValues();
137
138  void computeSetOfDeclarations(const DeclContext &dc);
139  ValueVector &getValueVector(const CFGBlock *block,
140                                const CFGBlock *dstBlock);
141
142  BVPair &getValueVectors(const CFGBlock *block, bool shouldLazyCreate);
143
144  void mergeIntoScratch(ValueVector const &source, bool isFirst);
145  bool updateValueVectorWithScratch(const CFGBlock *block);
146  bool updateValueVectors(const CFGBlock *block, const BVPair &newVals);
147
148  bool hasNoDeclarations() const {
149    return declToIndex.size() == 0;
150  }
151
152  void resetScratch();
153  ValueVector &getScratch() { return scratch; }
154
155  ValueVector::reference operator[](const VarDecl *vd);
156};
157}
158
159CFGBlockValues::CFGBlockValues(const CFG &c) : cfg(c), vals(0) {
160  unsigned n = cfg.getNumBlockIDs();
161  if (!n)
162    return;
163  vals = new std::pair<ValueVector*, ValueVector*>[n];
164  memset(vals, 0, sizeof(*vals) * n);
165}
166
167CFGBlockValues::~CFGBlockValues() {
168  unsigned n = cfg.getNumBlockIDs();
169  if (n == 0)
170    return;
171  for (unsigned i = 0; i < n; ++i) {
172    delete vals[i].first;
173    delete vals[i].second;
174  }
175  delete [] vals;
176}
177
178void CFGBlockValues::computeSetOfDeclarations(const DeclContext &dc) {
179  declToIndex.computeMap(dc);
180  scratch.resize(declToIndex.size());
181}
182
183ValueVector &CFGBlockValues::lazyCreate(ValueVector *&bv) {
184  if (!bv)
185    bv = new ValueVector(declToIndex.size());
186  return *bv;
187}
188
189/// This function pattern matches for a '&&' or '||' that appears at
190/// the beginning of a CFGBlock that also (1) has a terminator and
191/// (2) has no other elements.  If such an expression is found, it is returned.
192static BinaryOperator *getLogicalOperatorInChain(const CFGBlock *block) {
193  if (block->empty())
194    return 0;
195
196  const CFGStmt *cstmt = block->front().getAs<CFGStmt>();
197  if (!cstmt)
198    return 0;
199
200  BinaryOperator *b = llvm::dyn_cast_or_null<BinaryOperator>(cstmt->getStmt());
201
202  if (!b || !b->isLogicalOp())
203    return 0;
204
205  if (block->pred_size() == 2 &&
206      ((block->succ_size() == 2 && block->getTerminatorCondition() == b) ||
207       block->size() == 1))
208    return b;
209
210  return 0;
211}
212
213ValueVector &CFGBlockValues::getValueVector(const CFGBlock *block,
214                                            const CFGBlock *dstBlock) {
215  unsigned idx = block->getBlockID();
216  if (dstBlock && getLogicalOperatorInChain(block)) {
217    if (*block->succ_begin() == dstBlock)
218      return lazyCreate(vals[idx].first);
219    assert(*(block->succ_begin()+1) == dstBlock);
220    return lazyCreate(vals[idx].second);
221  }
222
223  assert(vals[idx].second == 0);
224  return lazyCreate(vals[idx].first);
225}
226
227BVPair &CFGBlockValues::getValueVectors(const clang::CFGBlock *block,
228                                        bool shouldLazyCreate) {
229  unsigned idx = block->getBlockID();
230  lazyCreate(vals[idx].first);
231  if (shouldLazyCreate)
232    lazyCreate(vals[idx].second);
233  return vals[idx];
234}
235
236void CFGBlockValues::mergeIntoScratch(ValueVector const &source,
237                                      bool isFirst) {
238  if (isFirst)
239    scratch = source;
240  else
241    scratch.merge(source);
242}
243#if 0
244static void printVector(const CFGBlock *block, ValueVector &bv,
245                        unsigned num) {
246
247  llvm::errs() << block->getBlockID() << " :";
248  for (unsigned i = 0; i < bv.size(); ++i) {
249    llvm::errs() << ' ' << bv[i];
250  }
251  llvm::errs() << " : " << num << '\n';
252}
253#endif
254
255bool CFGBlockValues::updateValueVectorWithScratch(const CFGBlock *block) {
256  ValueVector &dst = getValueVector(block, 0);
257  bool changed = (dst != scratch);
258  if (changed)
259    dst = scratch;
260#if 0
261  printVector(block, scratch, 0);
262#endif
263  return changed;
264}
265
266bool CFGBlockValues::updateValueVectors(const CFGBlock *block,
267                                      const BVPair &newVals) {
268  BVPair &vals = getValueVectors(block, true);
269  bool changed = *newVals.first != *vals.first ||
270                 *newVals.second != *vals.second;
271  *vals.first = *newVals.first;
272  *vals.second = *newVals.second;
273#if 0
274  printVector(block, *vals.first, 1);
275  printVector(block, *vals.second, 2);
276#endif
277  return changed;
278}
279
280void CFGBlockValues::resetScratch() {
281  scratch.reset();
282}
283
284ValueVector::reference CFGBlockValues::operator[](const VarDecl *vd) {
285  const llvm::Optional<unsigned> &idx = declToIndex.getValueIndex(vd);
286  assert(idx.hasValue());
287  return scratch[idx.getValue()];
288}
289
290//------------------------------------------------------------------------====//
291// Worklist: worklist for dataflow analysis.
292//====------------------------------------------------------------------------//
293
294namespace {
295class DataflowWorklist {
296  llvm::SmallVector<const CFGBlock *, 20> worklist;
297  llvm::BitVector enqueuedBlocks;
298public:
299  DataflowWorklist(const CFG &cfg) : enqueuedBlocks(cfg.getNumBlockIDs()) {}
300
301  void enqueue(const CFGBlock *block);
302  void enqueueSuccessors(const CFGBlock *block);
303  const CFGBlock *dequeue();
304
305};
306}
307
308void DataflowWorklist::enqueue(const CFGBlock *block) {
309  if (!block)
310    return;
311  unsigned idx = block->getBlockID();
312  if (enqueuedBlocks[idx])
313    return;
314  worklist.push_back(block);
315  enqueuedBlocks[idx] = true;
316}
317
318void DataflowWorklist::enqueueSuccessors(const clang::CFGBlock *block) {
319  for (CFGBlock::const_succ_iterator I = block->succ_begin(),
320       E = block->succ_end(); I != E; ++I) {
321    enqueue(*I);
322  }
323}
324
325const CFGBlock *DataflowWorklist::dequeue() {
326  if (worklist.empty())
327    return 0;
328  const CFGBlock *b = worklist.back();
329  worklist.pop_back();
330  enqueuedBlocks[b->getBlockID()] = false;
331  return b;
332}
333
334//------------------------------------------------------------------------====//
335// Transfer function for uninitialized values analysis.
336//====------------------------------------------------------------------------//
337
338namespace {
339class FindVarResult {
340  const VarDecl *vd;
341  const DeclRefExpr *dr;
342public:
343  FindVarResult(VarDecl *vd, DeclRefExpr *dr) : vd(vd), dr(dr) {}
344
345  const DeclRefExpr *getDeclRefExpr() const { return dr; }
346  const VarDecl *getDecl() const { return vd; }
347};
348
349class TransferFunctions : public CFGRecStmtVisitor<TransferFunctions> {
350  CFGBlockValues &vals;
351  const CFG &cfg;
352  AnalysisContext &ac;
353  UninitVariablesHandler *handler;
354  const DeclRefExpr *currentDR;
355  const Expr *currentVoidCast;
356  const bool flagBlockUses;
357public:
358  TransferFunctions(CFGBlockValues &vals, const CFG &cfg,
359                    AnalysisContext &ac,
360                    UninitVariablesHandler *handler,
361                    bool flagBlockUses)
362    : vals(vals), cfg(cfg), ac(ac), handler(handler), currentDR(0),
363      currentVoidCast(0), flagBlockUses(flagBlockUses) {}
364
365  const CFG &getCFG() { return cfg; }
366  void reportUninit(const DeclRefExpr *ex, const VarDecl *vd,
367                    bool isAlwaysUninit);
368
369  void VisitBlockExpr(BlockExpr *be);
370  void VisitDeclStmt(DeclStmt *ds);
371  void VisitDeclRefExpr(DeclRefExpr *dr);
372  void VisitUnaryOperator(UnaryOperator *uo);
373  void VisitBinaryOperator(BinaryOperator *bo);
374  void VisitCastExpr(CastExpr *ce);
375  void VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *se);
376  void BlockStmt_VisitObjCForCollectionStmt(ObjCForCollectionStmt *fs);
377
378  bool isTrackedVar(const VarDecl *vd) {
379    return ::isTrackedVar(vd, cast<DeclContext>(ac.getDecl()));
380  }
381
382  FindVarResult findBlockVarDecl(Expr *ex);
383};
384}
385
386void TransferFunctions::reportUninit(const DeclRefExpr *ex,
387                                     const VarDecl *vd, bool isAlwaysUnit) {
388  if (handler) handler->handleUseOfUninitVariable(ex, vd, isAlwaysUnit);
389}
390
391FindVarResult TransferFunctions::findBlockVarDecl(Expr* ex) {
392  if (DeclRefExpr* dr = dyn_cast<DeclRefExpr>(ex->IgnoreParenCasts()))
393    if (VarDecl *vd = dyn_cast<VarDecl>(dr->getDecl()))
394      if (isTrackedVar(vd))
395        return FindVarResult(vd, dr);
396  return FindVarResult(0, 0);
397}
398
399void TransferFunctions::BlockStmt_VisitObjCForCollectionStmt(
400    ObjCForCollectionStmt *fs) {
401
402  Visit(fs->getCollection());
403
404  // This represents an initialization of the 'element' value.
405  Stmt *element = fs->getElement();
406  const VarDecl* vd = 0;
407
408  if (DeclStmt* ds = dyn_cast<DeclStmt>(element)) {
409    vd = cast<VarDecl>(ds->getSingleDecl());
410    if (!isTrackedVar(vd))
411      vd = 0;
412  }
413  else {
414    // Initialize the value of the reference variable.
415    const FindVarResult &res = findBlockVarDecl(cast<Expr>(element));
416    vd = res.getDecl();
417    if (!vd) {
418      Visit(element);
419      return;
420    }
421  }
422
423  if (vd)
424    vals[vd] = Initialized;
425}
426
427void TransferFunctions::VisitBlockExpr(BlockExpr *be) {
428  if (!flagBlockUses || !handler)
429    return;
430  AnalysisContext::referenced_decls_iterator i, e;
431  llvm::tie(i, e) = ac.getReferencedBlockVars(be->getBlockDecl());
432  for ( ; i != e; ++i) {
433    const VarDecl *vd = *i;
434    if (vd->getAttr<BlocksAttr>() || !vd->hasLocalStorage() ||
435        !isTrackedVar(vd))
436      continue;
437    Value v = vals[vd];
438    if (isUninitialized(v))
439      handler->handleUseOfUninitVariable(be, vd, isAlwaysUninit(v));
440  }
441}
442
443void TransferFunctions::VisitDeclStmt(DeclStmt *ds) {
444  for (DeclStmt::decl_iterator DI = ds->decl_begin(), DE = ds->decl_end();
445       DI != DE; ++DI) {
446    if (VarDecl *vd = dyn_cast<VarDecl>(*DI)) {
447      if (isTrackedVar(vd)) {
448        vals[vd] = Uninitialized;
449        if (Stmt *init = vd->getInit()) {
450          Visit(init);
451          vals[vd] = Initialized;
452        }
453      }
454      else if (Stmt *init = vd->getInit()) {
455        Visit(init);
456      }
457    }
458  }
459}
460
461void TransferFunctions::VisitDeclRefExpr(DeclRefExpr *dr) {
462  // We assume that DeclRefExprs wrapped in an lvalue-to-rvalue cast
463  // cannot be block-level expressions.  Therefore, we determine if
464  // a DeclRefExpr is involved in a "load" by comparing it to the current
465  // DeclRefExpr found when analyzing the last lvalue-to-rvalue CastExpr.
466  // If a DeclRefExpr is not involved in a load, we are essentially computing
467  // its address, either for assignment to a reference or via the '&' operator.
468  // In such cases, treat the variable as being initialized, since this
469  // analysis isn't powerful enough to do alias tracking.
470  if (dr != currentDR)
471    if (const VarDecl *vd = dyn_cast<VarDecl>(dr->getDecl()))
472      if (isTrackedVar(vd))
473        vals[vd] = Initialized;
474}
475
476void TransferFunctions::VisitBinaryOperator(clang::BinaryOperator *bo) {
477  if (bo->isAssignmentOp()) {
478    const FindVarResult &res = findBlockVarDecl(bo->getLHS());
479    if (const VarDecl* vd = res.getDecl()) {
480      // We assume that DeclRefExprs wrapped in a BinaryOperator "assignment"
481      // cannot be block-level expressions.  Therefore, we determine if
482      // a DeclRefExpr is involved in a "load" by comparing it to the current
483      // DeclRefExpr found when analyzing the last lvalue-to-rvalue CastExpr.
484      SaveAndRestore<const DeclRefExpr*> lastDR(currentDR,
485                                                res.getDeclRefExpr());
486      Visit(bo->getRHS());
487      Visit(bo->getLHS());
488
489      ValueVector::reference val = vals[vd];
490      if (isUninitialized(val)) {
491        if (bo->getOpcode() != BO_Assign)
492          reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
493        val = Initialized;
494      }
495      return;
496    }
497  }
498  Visit(bo->getRHS());
499  Visit(bo->getLHS());
500}
501
502void TransferFunctions::VisitUnaryOperator(clang::UnaryOperator *uo) {
503  switch (uo->getOpcode()) {
504    case clang::UO_PostDec:
505    case clang::UO_PostInc:
506    case clang::UO_PreDec:
507    case clang::UO_PreInc: {
508      const FindVarResult &res = findBlockVarDecl(uo->getSubExpr());
509      if (const VarDecl *vd = res.getDecl()) {
510        // We assume that DeclRefExprs wrapped in a unary operator ++/--
511        // cannot be block-level expressions.  Therefore, we determine if
512        // a DeclRefExpr is involved in a "load" by comparing it to the current
513        // DeclRefExpr found when analyzing the last lvalue-to-rvalue CastExpr.
514        SaveAndRestore<const DeclRefExpr*> lastDR(currentDR,
515                                                  res.getDeclRefExpr());
516        Visit(uo->getSubExpr());
517
518        ValueVector::reference val = vals[vd];
519        if (isUninitialized(val)) {
520          reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
521          // Don't cascade warnings.
522          val = Initialized;
523        }
524        return;
525      }
526      break;
527    }
528    default:
529      break;
530  }
531  Visit(uo->getSubExpr());
532}
533
534void TransferFunctions::VisitCastExpr(clang::CastExpr *ce) {
535  if (ce->getCastKind() == CK_LValueToRValue) {
536    const FindVarResult &res = findBlockVarDecl(ce->getSubExpr());
537    if (const VarDecl *vd = res.getDecl()) {
538      // We assume that DeclRefExprs wrapped in an lvalue-to-rvalue cast
539      // cannot be block-level expressions.  Therefore, we determine if
540      // a DeclRefExpr is involved in a "load" by comparing it to the current
541      // DeclRefExpr found when analyzing the last lvalue-to-rvalue CastExpr.
542      // Here we update 'currentDR' to be the one associated with this
543      // lvalue-to-rvalue cast.  Then, when we analyze the DeclRefExpr, we
544      // will know that we are not computing its lvalue for other purposes
545      // than to perform a load.
546      SaveAndRestore<const DeclRefExpr*> lastDR(currentDR,
547                                                res.getDeclRefExpr());
548      Visit(ce->getSubExpr());
549      if (currentVoidCast != ce) {
550        Value val = vals[vd];
551        if (isUninitialized(val)) {
552          reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
553          // Don't cascade warnings.
554          vals[vd] = Initialized;
555        }
556      }
557      return;
558    }
559  }
560  else if (CStyleCastExpr *cse = dyn_cast<CStyleCastExpr>(ce)) {
561    if (cse->getType()->isVoidType()) {
562      // e.g. (void) x;
563      SaveAndRestore<const Expr *>
564        lastVoidCast(currentVoidCast, cse->getSubExpr()->IgnoreParens());
565      Visit(cse->getSubExpr());
566      return;
567    }
568  }
569  Visit(ce->getSubExpr());
570}
571
572void TransferFunctions::VisitUnaryExprOrTypeTraitExpr(
573                                          UnaryExprOrTypeTraitExpr *se) {
574  if (se->getKind() == UETT_SizeOf) {
575    if (se->getType()->isConstantSizeType())
576      return;
577    // Handle VLAs.
578    Visit(se->getArgumentExpr());
579  }
580}
581
582//------------------------------------------------------------------------====//
583// High-level "driver" logic for uninitialized values analysis.
584//====------------------------------------------------------------------------//
585
586static bool runOnBlock(const CFGBlock *block, const CFG &cfg,
587                       AnalysisContext &ac, CFGBlockValues &vals,
588                       UninitVariablesHandler *handler = 0,
589                       bool flagBlockUses = false) {
590
591  if (const BinaryOperator *b = getLogicalOperatorInChain(block)) {
592    CFGBlock::const_pred_iterator itr = block->pred_begin();
593    BVPair vA = vals.getValueVectors(*itr, false);
594    ++itr;
595    BVPair vB = vals.getValueVectors(*itr, false);
596
597    BVPair valsAB;
598
599    if (b->getOpcode() == BO_LAnd) {
600      // Merge the 'F' bits from the first and second.
601      vals.mergeIntoScratch(*(vA.second ? vA.second : vA.first), true);
602      vals.mergeIntoScratch(*(vB.second ? vB.second : vB.first), false);
603      valsAB.first = vA.first;
604      valsAB.second = &vals.getScratch();
605    }
606    else {
607      // Merge the 'T' bits from the first and second.
608      assert(b->getOpcode() == BO_LOr);
609      vals.mergeIntoScratch(*vA.first, true);
610      vals.mergeIntoScratch(*vB.first, false);
611      valsAB.first = &vals.getScratch();
612      valsAB.second = vA.second ? vA.second : vA.first;
613    }
614    return vals.updateValueVectors(block, valsAB);
615  }
616
617  // Default behavior: merge in values of predecessor blocks.
618  vals.resetScratch();
619  bool isFirst = true;
620  for (CFGBlock::const_pred_iterator I = block->pred_begin(),
621       E = block->pred_end(); I != E; ++I) {
622    vals.mergeIntoScratch(vals.getValueVector(*I, block), isFirst);
623    isFirst = false;
624  }
625  // Apply the transfer function.
626  TransferFunctions tf(vals, cfg, ac, handler, flagBlockUses);
627  for (CFGBlock::const_iterator I = block->begin(), E = block->end();
628       I != E; ++I) {
629    if (const CFGStmt *cs = dyn_cast<CFGStmt>(&*I)) {
630      tf.BlockStmt_Visit(cs->getStmt());
631    }
632  }
633  return vals.updateValueVectorWithScratch(block);
634}
635
636void clang::runUninitializedVariablesAnalysis(const DeclContext &dc,
637                                              const CFG &cfg,
638                                              AnalysisContext &ac,
639                                              UninitVariablesHandler &handler) {
640  CFGBlockValues vals(cfg);
641  vals.computeSetOfDeclarations(dc);
642  if (vals.hasNoDeclarations())
643    return;
644  DataflowWorklist worklist(cfg);
645  llvm::BitVector previouslyVisited(cfg.getNumBlockIDs());
646
647  worklist.enqueueSuccessors(&cfg.getEntry());
648
649  while (const CFGBlock *block = worklist.dequeue()) {
650    // Did the block change?
651    bool changed = runOnBlock(block, cfg, ac, vals);
652    if (changed || !previouslyVisited[block->getBlockID()])
653      worklist.enqueueSuccessors(block);
654    previouslyVisited[block->getBlockID()] = true;
655  }
656
657  // Run through the blocks one more time, and report uninitialized variabes.
658  for (CFG::const_iterator BI = cfg.begin(), BE = cfg.end(); BI != BE; ++BI) {
659    runOnBlock(*BI, cfg, ac, vals, &handler, /* flagBlockUses */ true);
660  }
661}
662
663UninitVariablesHandler::~UninitVariablesHandler() {}
664
665