UninitializedValues.cpp revision 6f27542da8843b5c1c579b86e342385bcc43d5f0 
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  void resetScratch();
128  ValueVector &getScratch() { return scratch; }
129
130  ValueVector::reference operator[](const VarDecl *vd);
131};
132} // end anonymous namespace
133
134CFGBlockValues::CFGBlockValues(const CFG &c) : cfg(c), vals(0) {
135  unsigned n = cfg.getNumBlockIDs();
136  if (!n)
137    return;
138  vals = new std::pair<ValueVector*, ValueVector*>[n];
139  memset((void*)vals, 0, sizeof(*vals) * n);
140}
141
142CFGBlockValues::~CFGBlockValues() {
143  unsigned n = cfg.getNumBlockIDs();
144  if (n == 0)
145    return;
146  for (unsigned i = 0; i < n; ++i) {
147    delete vals[i].first;
148    delete vals[i].second;
149  }
150  delete [] vals;
151}
152
153void CFGBlockValues::computeSetOfDeclarations(const DeclContext &dc) {
154  declToIndex.computeMap(dc);
155  scratch.resize(declToIndex.size());
156}
157
158ValueVector &CFGBlockValues::lazyCreate(ValueVector *&bv) {
159  if (!bv)
160    bv = new ValueVector(declToIndex.size());
161  return *bv;
162}
163
164/// This function pattern matches for a '&&' or '||' that appears at
165/// the beginning of a CFGBlock that also (1) has a terminator and
166/// (2) has no other elements.  If such an expression is found, it is returned.
167static const BinaryOperator *getLogicalOperatorInChain(const CFGBlock *block) {
168  if (block->empty())
169    return 0;
170
171  const CFGStmt *cstmt = block->front().getAs<CFGStmt>();
172  if (!cstmt)
173    return 0;
174
175  const BinaryOperator *b = dyn_cast_or_null<BinaryOperator>(cstmt->getStmt());
176
177  if (!b || !b->isLogicalOp())
178    return 0;
179
180  if (block->pred_size() == 2) {
181    if (block->getTerminatorCondition() == b) {
182      if (block->succ_size() == 2)
183      return b;
184    }
185    else if (block->size() == 1)
186      return b;
187  }
188
189  return 0;
190}
191
192ValueVector &CFGBlockValues::getValueVector(const CFGBlock *block,
193                                            const CFGBlock *dstBlock) {
194  unsigned idx = block->getBlockID();
195  if (dstBlock && getLogicalOperatorInChain(block)) {
196    if (*block->succ_begin() == dstBlock)
197      return lazyCreate(vals[idx].first);
198    assert(*(block->succ_begin()+1) == dstBlock);
199    return lazyCreate(vals[idx].second);
200  }
201
202  assert(vals[idx].second == 0);
203  return lazyCreate(vals[idx].first);
204}
205
206BVPair &CFGBlockValues::getValueVectors(const clang::CFGBlock *block,
207                                        bool shouldLazyCreate) {
208  unsigned idx = block->getBlockID();
209  lazyCreate(vals[idx].first);
210  if (shouldLazyCreate)
211    lazyCreate(vals[idx].second);
212  return vals[idx];
213}
214
215void CFGBlockValues::mergeIntoScratch(ValueVector const &source,
216                                      bool isFirst) {
217  if (isFirst)
218    scratch = source;
219  else
220    scratch |= source;
221}
222#if 0
223static void printVector(const CFGBlock *block, ValueVector &bv,
224                        unsigned num) {
225
226  llvm::errs() << block->getBlockID() << " :";
227  for (unsigned i = 0; i < bv.size(); ++i) {
228    llvm::errs() << ' ' << bv[i];
229  }
230  llvm::errs() << " : " << num << '\n';
231}
232#endif
233
234bool CFGBlockValues::updateValueVectorWithScratch(const CFGBlock *block) {
235  ValueVector &dst = getValueVector(block, 0);
236  bool changed = (dst != scratch);
237  if (changed)
238    dst = scratch;
239#if 0
240  printVector(block, scratch, 0);
241#endif
242  return changed;
243}
244
245bool CFGBlockValues::updateValueVectors(const CFGBlock *block,
246                                      const BVPair &newVals) {
247  BVPair &vals = getValueVectors(block, true);
248  bool changed = *newVals.first != *vals.first ||
249                 *newVals.second != *vals.second;
250  *vals.first = *newVals.first;
251  *vals.second = *newVals.second;
252#if 0
253  printVector(block, *vals.first, 1);
254  printVector(block, *vals.second, 2);
255#endif
256  return changed;
257}
258
259void CFGBlockValues::resetScratch() {
260  scratch.reset();
261}
262
263ValueVector::reference CFGBlockValues::operator[](const VarDecl *vd) {
264  const llvm::Optional<unsigned> &idx = declToIndex.getValueIndex(vd);
265  assert(idx.hasValue());
266  return scratch[idx.getValue()];
267}
268
269//------------------------------------------------------------------------====//
270// Worklist: worklist for dataflow analysis.
271//====------------------------------------------------------------------------//
272
273namespace {
274class DataflowWorklist {
275  SmallVector<const CFGBlock *, 20> worklist;
276  llvm::BitVector enqueuedBlocks;
277public:
278  DataflowWorklist(const CFG &cfg) : enqueuedBlocks(cfg.getNumBlockIDs()) {}
279
280  void enqueueSuccessors(const CFGBlock *block);
281  const CFGBlock *dequeue();
282};
283}
284
285void DataflowWorklist::enqueueSuccessors(const clang::CFGBlock *block) {
286  unsigned OldWorklistSize = worklist.size();
287  for (CFGBlock::const_succ_iterator I = block->succ_begin(),
288       E = block->succ_end(); I != E; ++I) {
289    const CFGBlock *Successor = *I;
290    if (!Successor || enqueuedBlocks[Successor->getBlockID()])
291      continue;
292    worklist.push_back(Successor);
293    enqueuedBlocks[Successor->getBlockID()] = true;
294  }
295  if (OldWorklistSize == 0 || OldWorklistSize == worklist.size())
296    return;
297
298  // Rotate the newly added blocks to the start of the worklist so that it forms
299  // a proper queue when we pop off the end of the worklist.
300  std::rotate(worklist.begin(), worklist.begin() + OldWorklistSize,
301              worklist.end());
302}
303
304const CFGBlock *DataflowWorklist::dequeue() {
305  if (worklist.empty())
306    return 0;
307  const CFGBlock *b = worklist.back();
308  worklist.pop_back();
309  enqueuedBlocks[b->getBlockID()] = false;
310  return b;
311}
312
313//------------------------------------------------------------------------====//
314// Transfer function for uninitialized values analysis.
315//====------------------------------------------------------------------------//
316
317namespace {
318class FindVarResult {
319  const VarDecl *vd;
320  const DeclRefExpr *dr;
321public:
322  FindVarResult(VarDecl *vd, DeclRefExpr *dr) : vd(vd), dr(dr) {}
323
324  const DeclRefExpr *getDeclRefExpr() const { return dr; }
325  const VarDecl *getDecl() const { return vd; }
326};
327
328class TransferFunctions : public StmtVisitor<TransferFunctions> {
329  CFGBlockValues &vals;
330  const CFG &cfg;
331  AnalysisContext &ac;
332  UninitVariablesHandler *handler;
333
334  /// The last DeclRefExpr seen when analyzing a block.  Used to
335  /// cheat when detecting cases when the address of a variable is taken.
336  DeclRefExpr *lastDR;
337
338  /// The last lvalue-to-rvalue conversion of a variable whose value
339  /// was uninitialized.  Normally this results in a warning, but it is
340  /// possible to either silence the warning in some cases, or we
341  /// propagate the uninitialized value.
342  CastExpr *lastLoad;
343
344  /// For some expressions, we want to ignore any post-processing after
345  /// visitation.
346  bool skipProcessUses;
347
348public:
349  TransferFunctions(CFGBlockValues &vals, const CFG &cfg,
350                    AnalysisContext &ac,
351                    UninitVariablesHandler *handler)
352    : vals(vals), cfg(cfg), ac(ac), handler(handler),
353      lastDR(0), lastLoad(0),
354      skipProcessUses(false) {}
355
356  void reportUninit(const DeclRefExpr *ex, const VarDecl *vd,
357                    bool isAlwaysUninit);
358
359  void VisitBlockExpr(BlockExpr *be);
360  void VisitDeclStmt(DeclStmt *ds);
361  void VisitDeclRefExpr(DeclRefExpr *dr);
362  void VisitUnaryOperator(UnaryOperator *uo);
363  void VisitBinaryOperator(BinaryOperator *bo);
364  void VisitCastExpr(CastExpr *ce);
365  void VisitObjCForCollectionStmt(ObjCForCollectionStmt *fs);
366  void Visit(Stmt *s);
367
368  bool isTrackedVar(const VarDecl *vd) {
369    return ::isTrackedVar(vd, cast<DeclContext>(ac.getDecl()));
370  }
371
372  FindVarResult findBlockVarDecl(Expr *ex);
373
374  void ProcessUses(Stmt *s = 0);
375};
376}
377
378static const Expr *stripCasts(ASTContext &C, const Expr *Ex) {
379  while (Ex) {
380    Ex = Ex->IgnoreParenNoopCasts(C);
381    if (const CastExpr *CE = dyn_cast<CastExpr>(Ex)) {
382      if (CE->getCastKind() == CK_LValueBitCast) {
383        Ex = CE->getSubExpr();
384        continue;
385      }
386    }
387    break;
388  }
389  return Ex;
390}
391
392void TransferFunctions::reportUninit(const DeclRefExpr *ex,
393                                     const VarDecl *vd, bool isAlwaysUnit) {
394  if (handler) handler->handleUseOfUninitVariable(ex, vd, isAlwaysUnit);
395}
396
397FindVarResult TransferFunctions::findBlockVarDecl(Expr *ex) {
398  if (DeclRefExpr *dr = dyn_cast<DeclRefExpr>(ex->IgnoreParenCasts()))
399    if (VarDecl *vd = dyn_cast<VarDecl>(dr->getDecl()))
400      if (isTrackedVar(vd))
401        return FindVarResult(vd, dr);
402  return FindVarResult(0, 0);
403}
404
405void TransferFunctions::VisitObjCForCollectionStmt(ObjCForCollectionStmt *fs) {
406  // This represents an initialization of the 'element' value.
407  Stmt *element = fs->getElement();
408  const VarDecl *vd = 0;
409
410  if (DeclStmt *ds = dyn_cast<DeclStmt>(element)) {
411    vd = cast<VarDecl>(ds->getSingleDecl());
412    if (!isTrackedVar(vd))
413      vd = 0;
414  } else {
415    // Initialize the value of the reference variable.
416    const FindVarResult &res = findBlockVarDecl(cast<Expr>(element));
417    vd = res.getDecl();
418  }
419
420  if (vd)
421    vals[vd] = Initialized;
422}
423
424void TransferFunctions::VisitBlockExpr(BlockExpr *be) {
425  const BlockDecl *bd = be->getBlockDecl();
426  for (BlockDecl::capture_const_iterator i = bd->capture_begin(),
427        e = bd->capture_end() ; i != e; ++i) {
428    const VarDecl *vd = i->getVariable();
429    if (!isTrackedVar(vd))
430      continue;
431    if (i->isByRef()) {
432      vals[vd] = Initialized;
433      continue;
434    }
435    Value v = vals[vd];
436    if (handler && isUninitialized(v))
437      handler->handleUseOfUninitVariable(be, vd, isAlwaysUninit(v));
438  }
439}
440
441void TransferFunctions::VisitDeclRefExpr(DeclRefExpr *dr) {
442  // Record the last DeclRefExpr seen.  This is an lvalue computation.
443  // We use this value to later detect if a variable "escapes" the analysis.
444  if (const VarDecl *vd = dyn_cast<VarDecl>(dr->getDecl()))
445    if (isTrackedVar(vd)) {
446      ProcessUses();
447      lastDR = dr;
448    }
449}
450
451void TransferFunctions::VisitDeclStmt(DeclStmt *ds) {
452  for (DeclStmt::decl_iterator DI = ds->decl_begin(), DE = ds->decl_end();
453       DI != DE; ++DI) {
454    if (VarDecl *vd = dyn_cast<VarDecl>(*DI)) {
455      if (isTrackedVar(vd)) {
456        if (Expr *init = vd->getInit()) {
457          // If the initializer consists solely of a reference to itself, we
458          // explicitly mark the variable as uninitialized. This allows code
459          // like the following:
460          //
461          //   int x = x;
462          //
463          // to deliberately leave a variable uninitialized. Different analysis
464          // clients can detect this pattern and adjust their reporting
465          // appropriately, but we need to continue to analyze subsequent uses
466          // of the variable.
467          if (init == lastLoad) {
468            const DeclRefExpr *DR
469              = cast<DeclRefExpr>(stripCasts(ac.getASTContext(),
470                                             lastLoad->getSubExpr()));
471            if (DR->getDecl() == vd) {
472              // int x = x;
473              // Propagate uninitialized value, but don't immediately report
474              // a problem.
475              vals[vd] = Uninitialized;
476              lastLoad = 0;
477              lastDR = 0;
478              return;
479            }
480          }
481
482          // All other cases: treat the new variable as initialized.
483          vals[vd] = Initialized;
484        }
485      }
486    }
487  }
488}
489
490void TransferFunctions::VisitBinaryOperator(clang::BinaryOperator *bo) {
491  if (bo->isAssignmentOp()) {
492    const FindVarResult &res = findBlockVarDecl(bo->getLHS());
493    if (const VarDecl *vd = res.getDecl()) {
494      ValueVector::reference val = vals[vd];
495      if (isUninitialized(val)) {
496        if (bo->getOpcode() != BO_Assign)
497          reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
498        else
499          val = Initialized;
500      }
501    }
502  }
503}
504
505void TransferFunctions::VisitUnaryOperator(clang::UnaryOperator *uo) {
506  switch (uo->getOpcode()) {
507    case clang::UO_PostDec:
508    case clang::UO_PostInc:
509    case clang::UO_PreDec:
510    case clang::UO_PreInc: {
511      const FindVarResult &res = findBlockVarDecl(uo->getSubExpr());
512      if (const VarDecl *vd = res.getDecl()) {
513        assert(res.getDeclRefExpr() == lastDR);
514        // We null out lastDR to indicate we have fully processed it
515        // and we don't want the auto-value setting in Visit().
516        lastDR = 0;
517
518        ValueVector::reference val = vals[vd];
519        if (isUninitialized(val))
520          reportUninit(res.getDeclRefExpr(), vd, isAlwaysUninit(val));
521      }
522      break;
523    }
524    default:
525      break;
526  }
527}
528
529void TransferFunctions::VisitCastExpr(clang::CastExpr *ce) {
530  if (ce->getCastKind() == CK_LValueToRValue) {
531    const FindVarResult &res = findBlockVarDecl(ce->getSubExpr());
532    if (const VarDecl *vd = res.getDecl()) {
533      assert(res.getDeclRefExpr() == lastDR);
534      if (isUninitialized(vals[vd])) {
535        // Record this load of an uninitialized value.  Normally this
536        // results in a warning, but we delay reporting the issue
537        // in case it is wrapped in a void cast, etc.
538        lastLoad = ce;
539      }
540    }
541  }
542  else if (ce->getCastKind() == CK_NoOp ||
543           ce->getCastKind() == CK_LValueBitCast) {
544    skipProcessUses = true;
545  }
546  else if (CStyleCastExpr *cse = dyn_cast<CStyleCastExpr>(ce)) {
547    if (cse->getType()->isVoidType()) {
548      // e.g. (void) x;
549      if (lastLoad == cse->getSubExpr()) {
550        // Squelch any detected load of an uninitialized value if
551        // we cast it to void.
552        lastLoad = 0;
553        lastDR = 0;
554      }
555    }
556  }
557}
558
559void TransferFunctions::Visit(clang::Stmt *s) {
560  skipProcessUses = false;
561  StmtVisitor<TransferFunctions>::Visit(s);
562  if (!skipProcessUses)
563    ProcessUses(s);
564}
565
566void TransferFunctions::ProcessUses(Stmt *s) {
567  // This method is typically called after visiting a CFGElement statement
568  // in the CFG.  We delay processing of reporting many loads of uninitialized
569  // values until here.
570  if (lastLoad) {
571    // If we just visited the lvalue-to-rvalue cast, there is nothing
572    // left to do.
573    if (lastLoad == s)
574      return;
575
576    // If we reach here, we have seen a load of an uninitialized value
577    // and it hasn't been casted to void or otherwise handled.  In this
578    // situation, report the incident.
579    const DeclRefExpr *DR =
580      cast<DeclRefExpr>(stripCasts(ac.getASTContext(),
581                                   lastLoad->getSubExpr()));
582    const VarDecl *VD = cast<VarDecl>(DR->getDecl());
583    reportUninit(DR, VD, isAlwaysUninit(vals[VD]));
584    lastLoad = 0;
585
586    if (DR == lastDR) {
587      lastDR = 0;
588      return;
589    }
590  }
591
592  // Any other uses of 'lastDR' involve taking an lvalue of variable.
593  // In this case, it "escapes" the analysis.
594  if (lastDR && lastDR != s) {
595    vals[cast<VarDecl>(lastDR->getDecl())] = Initialized;
596    lastDR = 0;
597  }
598}
599
600//------------------------------------------------------------------------====//
601// High-level "driver" logic for uninitialized values analysis.
602//====------------------------------------------------------------------------//
603
604static bool runOnBlock(const CFGBlock *block, const CFG &cfg,
605                       AnalysisContext &ac, CFGBlockValues &vals,
606                       llvm::BitVector &wasAnalyzed,
607                       UninitVariablesHandler *handler = 0) {
608
609  wasAnalyzed[block->getBlockID()] = true;
610
611  if (const BinaryOperator *b = getLogicalOperatorInChain(block)) {
612    CFGBlock::const_pred_iterator itr = block->pred_begin();
613    BVPair vA = vals.getValueVectors(*itr, false);
614    ++itr;
615    BVPair vB = vals.getValueVectors(*itr, false);
616
617    BVPair valsAB;
618
619    if (b->getOpcode() == BO_LAnd) {
620      // Merge the 'F' bits from the first and second.
621      vals.mergeIntoScratch(*(vA.second ? vA.second : vA.first), true);
622      vals.mergeIntoScratch(*(vB.second ? vB.second : vB.first), false);
623      valsAB.first = vA.first;
624      valsAB.second = &vals.getScratch();
625    } else {
626      // Merge the 'T' bits from the first and second.
627      assert(b->getOpcode() == BO_LOr);
628      vals.mergeIntoScratch(*vA.first, true);
629      vals.mergeIntoScratch(*vB.first, false);
630      valsAB.first = &vals.getScratch();
631      valsAB.second = vA.second ? vA.second : vA.first;
632    }
633    return vals.updateValueVectors(block, valsAB);
634  }
635
636  // Default behavior: merge in values of predecessor blocks.
637  vals.resetScratch();
638  bool isFirst = true;
639  for (CFGBlock::const_pred_iterator I = block->pred_begin(),
640       E = block->pred_end(); I != E; ++I) {
641    const CFGBlock *pred = *I;
642    if (wasAnalyzed[pred->getBlockID()]) {
643      vals.mergeIntoScratch(vals.getValueVector(pred, block), isFirst);
644      isFirst = false;
645    }
646  }
647  // Apply the transfer function.
648  TransferFunctions tf(vals, cfg, ac, handler);
649  for (CFGBlock::const_iterator I = block->begin(), E = block->end();
650       I != E; ++I) {
651    if (const CFGStmt *cs = dyn_cast<CFGStmt>(&*I)) {
652      tf.Visit(const_cast<Stmt*>(cs->getStmt()));
653    }
654  }
655  tf.ProcessUses();
656  return vals.updateValueVectorWithScratch(block);
657}
658
659void clang::runUninitializedVariablesAnalysis(
660    const DeclContext &dc,
661    const CFG &cfg,
662    AnalysisContext &ac,
663    UninitVariablesHandler &handler,
664    UninitVariablesAnalysisStats &stats) {
665  CFGBlockValues vals(cfg);
666  vals.computeSetOfDeclarations(dc);
667  if (vals.hasNoDeclarations())
668    return;
669
670  stats.NumVariablesAnalyzed = vals.getNumEntries();
671
672  // Mark all variables uninitialized at the entry.
673  const CFGBlock &entry = cfg.getEntry();
674  for (CFGBlock::const_succ_iterator i = entry.succ_begin(),
675        e = entry.succ_end(); i != e; ++i) {
676    if (const CFGBlock *succ = *i) {
677      ValueVector &vec = vals.getValueVector(&entry, succ);
678      const unsigned n = vals.getNumEntries();
679      for (unsigned j = 0; j < n ; ++j) {
680        vec[j] = Uninitialized;
681      }
682    }
683  }
684
685  // Proceed with the workist.
686  DataflowWorklist worklist(cfg);
687  llvm::BitVector previouslyVisited(cfg.getNumBlockIDs());
688  worklist.enqueueSuccessors(&cfg.getEntry());
689  llvm::BitVector wasAnalyzed(cfg.getNumBlockIDs(), false);
690  wasAnalyzed[cfg.getEntry().getBlockID()] = true;
691
692  while (const CFGBlock *block = worklist.dequeue()) {
693    // Did the block change?
694    bool changed = runOnBlock(block, cfg, ac, vals, wasAnalyzed);
695    ++stats.NumBlockVisits;
696    if (changed || !previouslyVisited[block->getBlockID()])
697      worklist.enqueueSuccessors(block);
698    previouslyVisited[block->getBlockID()] = true;
699  }
700
701  // Run through the blocks one more time, and report uninitialized variabes.
702  for (CFG::const_iterator BI = cfg.begin(), BE = cfg.end(); BI != BE; ++BI) {
703    const CFGBlock *block = *BI;
704    if (wasAnalyzed[block->getBlockID()]) {
705      runOnBlock(block, cfg, ac, vals, wasAnalyzed, &handler);
706      ++stats.NumBlockVisits;
707    }
708  }
709}
710
711UninitVariablesHandler::~UninitVariablesHandler() {}
712