clang  15.0.0git
ReachableCode.cpp
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1 //===-- ReachableCode.cpp - Code Reachability Analysis --------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements a flow-sensitive, path-insensitive analysis of
10 // determining reachable blocks within a CFG.
11 //
12 //===----------------------------------------------------------------------===//
13 
15 #include "clang/AST/Expr.h"
16 #include "clang/AST/ExprCXX.h"
17 #include "clang/AST/ExprObjC.h"
18 #include "clang/AST/ParentMap.h"
19 #include "clang/AST/StmtCXX.h"
21 #include "clang/Analysis/CFG.h"
22 #include "clang/Basic/Builtins.h"
24 #include "clang/Lex/Preprocessor.h"
25 #include "llvm/ADT/BitVector.h"
26 #include "llvm/ADT/SmallVector.h"
27 
28 using namespace clang;
29 
30 //===----------------------------------------------------------------------===//
31 // Core Reachability Analysis routines.
32 //===----------------------------------------------------------------------===//
33 
34 static bool isEnumConstant(const Expr *Ex) {
35  const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Ex);
36  if (!DR)
37  return false;
38  return isa<EnumConstantDecl>(DR->getDecl());
39 }
40 
41 static bool isTrivialExpression(const Expr *Ex) {
42  Ex = Ex->IgnoreParenCasts();
43  return isa<IntegerLiteral>(Ex) || isa<StringLiteral>(Ex) ||
44  isa<CXXBoolLiteralExpr>(Ex) || isa<ObjCBoolLiteralExpr>(Ex) ||
45  isa<CharacterLiteral>(Ex) ||
46  isEnumConstant(Ex);
47 }
48 
49 static bool isTrivialDoWhile(const CFGBlock *B, const Stmt *S) {
50  // Check if the block ends with a do...while() and see if 'S' is the
51  // condition.
52  if (const Stmt *Term = B->getTerminatorStmt()) {
53  if (const DoStmt *DS = dyn_cast<DoStmt>(Term)) {
54  const Expr *Cond = DS->getCond()->IgnoreParenCasts();
55  return Cond == S && isTrivialExpression(Cond);
56  }
57  }
58  return false;
59 }
60 
61 static bool isBuiltinUnreachable(const Stmt *S) {
62  if (const auto *DRE = dyn_cast<DeclRefExpr>(S))
63  if (const auto *FDecl = dyn_cast<FunctionDecl>(DRE->getDecl()))
64  return FDecl->getIdentifier() &&
65  FDecl->getBuiltinID() == Builtin::BI__builtin_unreachable;
66  return false;
67 }
68 
69 static bool isBuiltinAssumeFalse(const CFGBlock *B, const Stmt *S,
70  ASTContext &C) {
71  if (B->empty()) {
72  // Happens if S is B's terminator and B contains nothing else
73  // (e.g. a CFGBlock containing only a goto).
74  return false;
75  }
76  if (Optional<CFGStmt> CS = B->back().getAs<CFGStmt>()) {
77  if (const auto *CE = dyn_cast<CallExpr>(CS->getStmt())) {
78  return CE->getCallee()->IgnoreCasts() == S && CE->isBuiltinAssumeFalse(C);
79  }
80  }
81  return false;
82 }
83 
84 static bool isDeadReturn(const CFGBlock *B, const Stmt *S) {
85  // Look to see if the current control flow ends with a 'return', and see if
86  // 'S' is a substatement. The 'return' may not be the last element in the
87  // block, or may be in a subsequent block because of destructors.
88  const CFGBlock *Current = B;
89  while (true) {
90  for (const CFGElement &CE : llvm::reverse(*Current)) {
91  if (Optional<CFGStmt> CS = CE.getAs<CFGStmt>()) {
92  if (const ReturnStmt *RS = dyn_cast<ReturnStmt>(CS->getStmt())) {
93  if (RS == S)
94  return true;
95  if (const Expr *RE = RS->getRetValue()) {
96  RE = RE->IgnoreParenCasts();
97  if (RE == S)
98  return true;
99  ParentMap PM(const_cast<Expr *>(RE));
100  // If 'S' is in the ParentMap, it is a subexpression of
101  // the return statement.
102  return PM.getParent(S);
103  }
104  }
105  break;
106  }
107  }
108  // Note also that we are restricting the search for the return statement
109  // to stop at control-flow; only part of a return statement may be dead,
110  // without the whole return statement being dead.
111  if (Current->getTerminator().isTemporaryDtorsBranch()) {
112  // Temporary destructors have a predictable control flow, thus we want to
113  // look into the next block for the return statement.
114  // We look into the false branch, as we know the true branch only contains
115  // the call to the destructor.
116  assert(Current->succ_size() == 2);
117  Current = *(Current->succ_begin() + 1);
118  } else if (!Current->getTerminatorStmt() && Current->succ_size() == 1) {
119  // If there is only one successor, we're not dealing with outgoing control
120  // flow. Thus, look into the next block.
121  Current = *Current->succ_begin();
122  if (Current->pred_size() > 1) {
123  // If there is more than one predecessor, we're dealing with incoming
124  // control flow - if the return statement is in that block, it might
125  // well be reachable via a different control flow, thus it's not dead.
126  return false;
127  }
128  } else {
129  // We hit control flow or a dead end. Stop searching.
130  return false;
131  }
132  }
133  llvm_unreachable("Broke out of infinite loop.");
134 }
135 
137  assert(Loc.isMacroID());
139  do {
140  Last = Loc;
141  Loc = SM.getImmediateMacroCallerLoc(Loc);
142  } while (Loc.isMacroID());
143  return Last;
144 }
145 
146 /// Returns true if the statement is expanded from a configuration macro.
148  Preprocessor &PP,
149  bool IgnoreYES_NO = false) {
150  // FIXME: This is not very precise. Here we just check to see if the
151  // value comes from a macro, but we can do much better. This is likely
152  // to be over conservative. This logic is factored into a separate function
153  // so that we can refine it later.
154  SourceLocation L = S->getBeginLoc();
155  if (L.isMacroID()) {
157  if (IgnoreYES_NO) {
158  // The Objective-C constant 'YES' and 'NO'
159  // are defined as macros. Do not treat them
160  // as configuration values.
161  SourceLocation TopL = getTopMostMacro(L, SM);
162  StringRef MacroName = PP.getImmediateMacroName(TopL);
163  if (MacroName == "YES" || MacroName == "NO")
164  return false;
165  } else if (!PP.getLangOpts().CPlusPlus) {
166  // Do not treat C 'false' and 'true' macros as configuration values.
167  SourceLocation TopL = getTopMostMacro(L, SM);
168  StringRef MacroName = PP.getImmediateMacroName(TopL);
169  if (MacroName == "false" || MacroName == "true")
170  return false;
171  }
172  return true;
173  }
174  return false;
175 }
176 
177 static bool isConfigurationValue(const ValueDecl *D, Preprocessor &PP);
178 
179 /// Returns true if the statement represents a configuration value.
180 ///
181 /// A configuration value is something usually determined at compile-time
182 /// to conditionally always execute some branch. Such guards are for
183 /// "sometimes unreachable" code. Such code is usually not interesting
184 /// to report as unreachable, and may mask truly unreachable code within
185 /// those blocks.
186 static bool isConfigurationValue(const Stmt *S,
187  Preprocessor &PP,
188  SourceRange *SilenceableCondVal = nullptr,
189  bool IncludeIntegers = true,
190  bool WrappedInParens = false) {
191  if (!S)
192  return false;
193 
194  if (const auto *Ex = dyn_cast<Expr>(S))
195  S = Ex->IgnoreImplicit();
196 
197  if (const auto *Ex = dyn_cast<Expr>(S))
198  S = Ex->IgnoreCasts();
199 
200  // Special case looking for the sigil '()' around an integer literal.
201  if (const ParenExpr *PE = dyn_cast<ParenExpr>(S))
202  if (!PE->getBeginLoc().isMacroID())
203  return isConfigurationValue(PE->getSubExpr(), PP, SilenceableCondVal,
204  IncludeIntegers, true);
205 
206  if (const Expr *Ex = dyn_cast<Expr>(S))
207  S = Ex->IgnoreCasts();
208 
209  bool IgnoreYES_NO = false;
210 
211  switch (S->getStmtClass()) {
212  case Stmt::CallExprClass: {
213  const FunctionDecl *Callee =
214  dyn_cast_or_null<FunctionDecl>(cast<CallExpr>(S)->getCalleeDecl());
215  return Callee ? Callee->isConstexpr() : false;
216  }
217  case Stmt::DeclRefExprClass:
218  return isConfigurationValue(cast<DeclRefExpr>(S)->getDecl(), PP);
219  case Stmt::ObjCBoolLiteralExprClass:
220  IgnoreYES_NO = true;
221  LLVM_FALLTHROUGH;
222  case Stmt::CXXBoolLiteralExprClass:
223  case Stmt::IntegerLiteralClass: {
224  const Expr *E = cast<Expr>(S);
225  if (IncludeIntegers) {
226  if (SilenceableCondVal && !SilenceableCondVal->getBegin().isValid())
227  *SilenceableCondVal = E->getSourceRange();
228  return WrappedInParens ||
229  isExpandedFromConfigurationMacro(E, PP, IgnoreYES_NO);
230  }
231  return false;
232  }
233  case Stmt::MemberExprClass:
234  return isConfigurationValue(cast<MemberExpr>(S)->getMemberDecl(), PP);
235  case Stmt::UnaryExprOrTypeTraitExprClass:
236  return true;
237  case Stmt::BinaryOperatorClass: {
238  const BinaryOperator *B = cast<BinaryOperator>(S);
239  // Only include raw integers (not enums) as configuration
240  // values if they are used in a logical or comparison operator
241  // (not arithmetic).
242  IncludeIntegers &= (B->isLogicalOp() || B->isComparisonOp());
243  return isConfigurationValue(B->getLHS(), PP, SilenceableCondVal,
244  IncludeIntegers) ||
245  isConfigurationValue(B->getRHS(), PP, SilenceableCondVal,
246  IncludeIntegers);
247  }
248  case Stmt::UnaryOperatorClass: {
249  const UnaryOperator *UO = cast<UnaryOperator>(S);
250  if (UO->getOpcode() != UO_LNot && UO->getOpcode() != UO_Minus)
251  return false;
252  bool SilenceableCondValNotSet =
253  SilenceableCondVal && SilenceableCondVal->getBegin().isInvalid();
254  bool IsSubExprConfigValue =
255  isConfigurationValue(UO->getSubExpr(), PP, SilenceableCondVal,
256  IncludeIntegers, WrappedInParens);
257  // Update the silenceable condition value source range only if the range
258  // was set directly by the child expression.
259  if (SilenceableCondValNotSet &&
260  SilenceableCondVal->getBegin().isValid() &&
261  *SilenceableCondVal ==
263  *SilenceableCondVal = UO->getSourceRange();
264  return IsSubExprConfigValue;
265  }
266  default:
267  return false;
268  }
269 }
270 
271 static bool isConfigurationValue(const ValueDecl *D, Preprocessor &PP) {
272  if (const EnumConstantDecl *ED = dyn_cast<EnumConstantDecl>(D))
273  return isConfigurationValue(ED->getInitExpr(), PP);
274  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
275  // As a heuristic, treat globals as configuration values. Note
276  // that we only will get here if Sema evaluated this
277  // condition to a constant expression, which means the global
278  // had to be declared in a way to be a truly constant value.
279  // We could generalize this to local variables, but it isn't
280  // clear if those truly represent configuration values that
281  // gate unreachable code.
282  if (!VD->hasLocalStorage())
283  return true;
284 
285  // As a heuristic, locals that have been marked 'const' explicitly
286  // can be treated as configuration values as well.
287  return VD->getType().isLocalConstQualified();
288  }
289  return false;
290 }
291 
292 /// Returns true if we should always explore all successors of a block.
294  Preprocessor &PP) {
295  if (const Stmt *Term = B->getTerminatorStmt()) {
296  if (isa<SwitchStmt>(Term))
297  return true;
298  // Specially handle '||' and '&&'.
299  if (isa<BinaryOperator>(Term)) {
300  return isConfigurationValue(Term, PP);
301  }
302  }
303 
304  const Stmt *Cond = B->getTerminatorCondition(/* stripParens */ false);
305  return isConfigurationValue(Cond, PP);
306 }
307 
308 static unsigned scanFromBlock(const CFGBlock *Start,
309  llvm::BitVector &Reachable,
310  Preprocessor *PP,
311  bool IncludeSometimesUnreachableEdges) {
312  unsigned count = 0;
313 
314  // Prep work queue
316 
317  // The entry block may have already been marked reachable
318  // by the caller.
319  if (!Reachable[Start->getBlockID()]) {
320  ++count;
321  Reachable[Start->getBlockID()] = true;
322  }
323 
324  WL.push_back(Start);
325 
326  // Find the reachable blocks from 'Start'.
327  while (!WL.empty()) {
328  const CFGBlock *item = WL.pop_back_val();
329 
330  // There are cases where we want to treat all successors as reachable.
331  // The idea is that some "sometimes unreachable" code is not interesting,
332  // and that we should forge ahead and explore those branches anyway.
333  // This allows us to potentially uncover some "always unreachable" code
334  // within the "sometimes unreachable" code.
335  // Look at the successors and mark then reachable.
336  Optional<bool> TreatAllSuccessorsAsReachable;
337  if (!IncludeSometimesUnreachableEdges)
338  TreatAllSuccessorsAsReachable = false;
339 
340  for (CFGBlock::const_succ_iterator I = item->succ_begin(),
341  E = item->succ_end(); I != E; ++I) {
342  const CFGBlock *B = *I;
343  if (!B) do {
344  const CFGBlock *UB = I->getPossiblyUnreachableBlock();
345  if (!UB)
346  break;
347 
348  if (!TreatAllSuccessorsAsReachable.hasValue()) {
349  assert(PP);
350  TreatAllSuccessorsAsReachable =
352  }
353 
354  if (TreatAllSuccessorsAsReachable.getValue()) {
355  B = UB;
356  break;
357  }
358  }
359  while (false);
360 
361  if (B) {
362  unsigned blockID = B->getBlockID();
363  if (!Reachable[blockID]) {
364  Reachable.set(blockID);
365  WL.push_back(B);
366  ++count;
367  }
368  }
369  }
370  }
371  return count;
372 }
373 
374 static unsigned scanMaybeReachableFromBlock(const CFGBlock *Start,
375  Preprocessor &PP,
376  llvm::BitVector &Reachable) {
377  return scanFromBlock(Start, Reachable, &PP, true);
378 }
379 
380 //===----------------------------------------------------------------------===//
381 // Dead Code Scanner.
382 //===----------------------------------------------------------------------===//
383 
384 namespace {
385  class DeadCodeScan {
386  llvm::BitVector Visited;
387  llvm::BitVector &Reachable;
389  Preprocessor &PP;
390  ASTContext &C;
391 
393  DeferredLocsTy;
394 
395  DeferredLocsTy DeferredLocs;
396 
397  public:
398  DeadCodeScan(llvm::BitVector &reachable, Preprocessor &PP, ASTContext &C)
399  : Visited(reachable.size()),
400  Reachable(reachable),
401  PP(PP), C(C) {}
402 
403  void enqueue(const CFGBlock *block);
404  unsigned scanBackwards(const CFGBlock *Start,
406 
407  bool isDeadCodeRoot(const CFGBlock *Block);
408 
409  const Stmt *findDeadCode(const CFGBlock *Block);
410 
411  void reportDeadCode(const CFGBlock *B,
412  const Stmt *S,
414  };
415 }
416 
417 void DeadCodeScan::enqueue(const CFGBlock *block) {
418  unsigned blockID = block->getBlockID();
419  if (Reachable[blockID] || Visited[blockID])
420  return;
421  Visited[blockID] = true;
422  WorkList.push_back(block);
423 }
424 
425 bool DeadCodeScan::isDeadCodeRoot(const clang::CFGBlock *Block) {
426  bool isDeadRoot = true;
427 
428  for (CFGBlock::const_pred_iterator I = Block->pred_begin(),
429  E = Block->pred_end(); I != E; ++I) {
430  if (const CFGBlock *PredBlock = *I) {
431  unsigned blockID = PredBlock->getBlockID();
432  if (Visited[blockID]) {
433  isDeadRoot = false;
434  continue;
435  }
436  if (!Reachable[blockID]) {
437  isDeadRoot = false;
438  Visited[blockID] = true;
439  WorkList.push_back(PredBlock);
440  continue;
441  }
442  }
443  }
444 
445  return isDeadRoot;
446 }
447 
448 static bool isValidDeadStmt(const Stmt *S) {
449  if (S->getBeginLoc().isInvalid())
450  return false;
451  if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(S))
452  return BO->getOpcode() != BO_Comma;
453  return true;
454 }
455 
456 const Stmt *DeadCodeScan::findDeadCode(const clang::CFGBlock *Block) {
457  for (CFGBlock::const_iterator I = Block->begin(), E = Block->end(); I!=E; ++I)
458  if (Optional<CFGStmt> CS = I->getAs<CFGStmt>()) {
459  const Stmt *S = CS->getStmt();
460  if (isValidDeadStmt(S))
461  return S;
462  }
463 
464  CFGTerminator T = Block->getTerminator();
465  if (T.isStmtBranch()) {
466  const Stmt *S = T.getStmt();
467  if (S && isValidDeadStmt(S))
468  return S;
469  }
470 
471  return nullptr;
472 }
473 
474 static int SrcCmp(const std::pair<const CFGBlock *, const Stmt *> *p1,
475  const std::pair<const CFGBlock *, const Stmt *> *p2) {
476  if (p1->second->getBeginLoc() < p2->second->getBeginLoc())
477  return -1;
478  if (p2->second->getBeginLoc() < p1->second->getBeginLoc())
479  return 1;
480  return 0;
481 }
482 
483 unsigned DeadCodeScan::scanBackwards(const clang::CFGBlock *Start,
485 
486  unsigned count = 0;
487  enqueue(Start);
488 
489  while (!WorkList.empty()) {
490  const CFGBlock *Block = WorkList.pop_back_val();
491 
492  // It is possible that this block has been marked reachable after
493  // it was enqueued.
494  if (Reachable[Block->getBlockID()])
495  continue;
496 
497  // Look for any dead code within the block.
498  const Stmt *S = findDeadCode(Block);
499 
500  if (!S) {
501  // No dead code. Possibly an empty block. Look at dead predecessors.
502  for (CFGBlock::const_pred_iterator I = Block->pred_begin(),
503  E = Block->pred_end(); I != E; ++I) {
504  if (const CFGBlock *predBlock = *I)
505  enqueue(predBlock);
506  }
507  continue;
508  }
509 
510  // Specially handle macro-expanded code.
511  if (S->getBeginLoc().isMacroID()) {
512  count += scanMaybeReachableFromBlock(Block, PP, Reachable);
513  continue;
514  }
515 
516  if (isDeadCodeRoot(Block)) {
517  reportDeadCode(Block, S, CB);
518  count += scanMaybeReachableFromBlock(Block, PP, Reachable);
519  }
520  else {
521  // Record this statement as the possibly best location in a
522  // strongly-connected component of dead code for emitting a
523  // warning.
524  DeferredLocs.push_back(std::make_pair(Block, S));
525  }
526  }
527 
528  // If we didn't find a dead root, then report the dead code with the
529  // earliest location.
530  if (!DeferredLocs.empty()) {
531  llvm::array_pod_sort(DeferredLocs.begin(), DeferredLocs.end(), SrcCmp);
532  for (const auto &I : DeferredLocs) {
533  const CFGBlock *Block = I.first;
534  if (Reachable[Block->getBlockID()])
535  continue;
536  reportDeadCode(Block, I.second, CB);
537  count += scanMaybeReachableFromBlock(Block, PP, Reachable);
538  }
539  }
540 
541  return count;
542 }
543 
545  SourceRange &R1,
546  SourceRange &R2) {
547  R1 = R2 = SourceRange();
548 
549  if (const Expr *Ex = dyn_cast<Expr>(S))
550  S = Ex->IgnoreParenImpCasts();
551 
552  switch (S->getStmtClass()) {
553  case Expr::BinaryOperatorClass: {
554  const BinaryOperator *BO = cast<BinaryOperator>(S);
555  return BO->getOperatorLoc();
556  }
557  case Expr::UnaryOperatorClass: {
558  const UnaryOperator *UO = cast<UnaryOperator>(S);
559  R1 = UO->getSubExpr()->getSourceRange();
560  return UO->getOperatorLoc();
561  }
562  case Expr::CompoundAssignOperatorClass: {
563  const CompoundAssignOperator *CAO = cast<CompoundAssignOperator>(S);
564  R1 = CAO->getLHS()->getSourceRange();
565  R2 = CAO->getRHS()->getSourceRange();
566  return CAO->getOperatorLoc();
567  }
568  case Expr::BinaryConditionalOperatorClass:
569  case Expr::ConditionalOperatorClass: {
570  const AbstractConditionalOperator *CO =
571  cast<AbstractConditionalOperator>(S);
572  return CO->getQuestionLoc();
573  }
574  case Expr::MemberExprClass: {
575  const MemberExpr *ME = cast<MemberExpr>(S);
576  R1 = ME->getSourceRange();
577  return ME->getMemberLoc();
578  }
579  case Expr::ArraySubscriptExprClass: {
580  const ArraySubscriptExpr *ASE = cast<ArraySubscriptExpr>(S);
581  R1 = ASE->getLHS()->getSourceRange();
582  R2 = ASE->getRHS()->getSourceRange();
583  return ASE->getRBracketLoc();
584  }
585  case Expr::CStyleCastExprClass: {
586  const CStyleCastExpr *CSC = cast<CStyleCastExpr>(S);
587  R1 = CSC->getSubExpr()->getSourceRange();
588  return CSC->getLParenLoc();
589  }
590  case Expr::CXXFunctionalCastExprClass: {
591  const CXXFunctionalCastExpr *CE = cast <CXXFunctionalCastExpr>(S);
592  R1 = CE->getSubExpr()->getSourceRange();
593  return CE->getBeginLoc();
594  }
595  case Stmt::CXXTryStmtClass: {
596  return cast<CXXTryStmt>(S)->getHandler(0)->getCatchLoc();
597  }
598  case Expr::ObjCBridgedCastExprClass: {
599  const ObjCBridgedCastExpr *CSC = cast<ObjCBridgedCastExpr>(S);
600  R1 = CSC->getSubExpr()->getSourceRange();
601  return CSC->getLParenLoc();
602  }
603  default: ;
604  }
605  R1 = S->getSourceRange();
606  return S->getBeginLoc();
607 }
608 
609 void DeadCodeScan::reportDeadCode(const CFGBlock *B,
610  const Stmt *S,
612  // Classify the unreachable code found, or suppress it in some cases.
614 
615  if (isa<BreakStmt>(S)) {
617  } else if (isTrivialDoWhile(B, S) || isBuiltinUnreachable(S) ||
618  isBuiltinAssumeFalse(B, S, C)) {
619  return;
620  }
621  else if (isDeadReturn(B, S)) {
623  }
624 
625  SourceRange SilenceableCondVal;
626 
627  if (UK == reachable_code::UK_Other) {
628  // Check if the dead code is part of the "loop target" of
629  // a for/for-range loop. This is the block that contains
630  // the increment code.
631  if (const Stmt *LoopTarget = B->getLoopTarget()) {
632  SourceLocation Loc = LoopTarget->getBeginLoc();
633  SourceRange R1(Loc, Loc), R2;
634 
635  if (const ForStmt *FS = dyn_cast<ForStmt>(LoopTarget)) {
636  const Expr *Inc = FS->getInc();
637  Loc = Inc->getBeginLoc();
638  R2 = Inc->getSourceRange();
639  }
640 
642  Loc, SourceRange(), SourceRange(Loc, Loc), R2);
643  return;
644  }
645 
646  // Check if the dead block has a predecessor whose branch has
647  // a configuration value that *could* be modified to
648  // silence the warning.
650  if (PI != B->pred_end()) {
651  if (const CFGBlock *PredBlock = PI->getPossiblyUnreachableBlock()) {
652  const Stmt *TermCond =
653  PredBlock->getTerminatorCondition(/* strip parens */ false);
654  isConfigurationValue(TermCond, PP, &SilenceableCondVal);
655  }
656  }
657  }
658 
659  SourceRange R1, R2;
660  SourceLocation Loc = GetUnreachableLoc(S, R1, R2);
661  CB.HandleUnreachable(UK, Loc, SilenceableCondVal, R1, R2);
662 }
663 
664 //===----------------------------------------------------------------------===//
665 // Reachability APIs.
666 //===----------------------------------------------------------------------===//
667 
668 namespace clang { namespace reachable_code {
669 
670 void Callback::anchor() { }
671 
672 unsigned ScanReachableFromBlock(const CFGBlock *Start,
673  llvm::BitVector &Reachable) {
674  return scanFromBlock(Start, Reachable, /* SourceManager* */ nullptr, false);
675 }
676 
678  Callback &CB) {
679 
680  CFG *cfg = AC.getCFG();
681  if (!cfg)
682  return;
683 
684  // Scan for reachable blocks from the entrance of the CFG.
685  // If there are no unreachable blocks, we're done.
686  llvm::BitVector reachable(cfg->getNumBlockIDs());
687  unsigned numReachable =
688  scanMaybeReachableFromBlock(&cfg->getEntry(), PP, reachable);
689  if (numReachable == cfg->getNumBlockIDs())
690  return;
691 
692  // If there aren't explicit EH edges, we should include the 'try' dispatch
693  // blocks as roots.
694  if (!AC.getCFGBuildOptions().AddEHEdges) {
695  for (const CFGBlock *B : cfg->try_blocks())
696  numReachable += scanMaybeReachableFromBlock(B, PP, reachable);
697  if (numReachable == cfg->getNumBlockIDs())
698  return;
699  }
700 
701  // There are some unreachable blocks. We need to find the root blocks that
702  // contain code that should be considered unreachable.
703  for (const CFGBlock *block : *cfg) {
704  // A block may have been marked reachable during this loop.
705  if (reachable[block->getBlockID()])
706  continue;
707 
708  DeadCodeScan DS(reachable, PP, AC.getASTContext());
709  numReachable += DS.scanBackwards(block, CB);
710 
711  if (numReachable == cfg->getNumBlockIDs())
712  return;
713  }
714 }
715 
716 }} // end namespace clang::reachable_code
clang::CFGTerminator::isStmtBranch
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Definition: CFG.h:539
Builtins.h
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ASTContext & getASTContext() const
Definition: AnalysisDeclContext.h:104
clang::reachable_code::FindUnreachableCode
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Definition: ReachableCode.cpp:677
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Definition: CFG.h:1067
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Definition: SourceLocation.h:210
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Returns true if the statement is expanded from a configuration macro.
Definition: ReachableCode.cpp:147
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Definition: CFG.h:918
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Definition: ReachableCode.cpp:293
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Returns the total number of BlockIDs allocated (which start at 0).
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Definition: CFG.h:955
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Definition: LLVM.h:38
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Definition: CFG.h:1240
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Encodes a location in the source.
Definition: SourceLocation.h:86
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Definition: Expr.h:3525
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@ UK_Loop_Increment
Definition: ReachableCode.h:43
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Definition: Stmt.cpp:324
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An Objective-C "bridged" cast expression, which casts between Objective-C pointers and C pointers,...
Definition: ExprObjC.h:1625
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@ C
Definition: SemaDeclAttr.cpp:55
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AnalysisDeclContext contains the context data for the function, method or block under analysis.
Definition: AnalysisDeclContext.h:72
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Definition: LLVM.h:40
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UnaryOperator - This represents the unary-expression's (except sizeof and alignof),...
Definition: Expr.h:2163
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Definition: CFG.h:931
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Represents a source-level, intra-procedural CFG that represents the control-flow of a Stmt.
Definition: CFG.h:1225
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UnreachableKind
Classifications of unreachable code.
Definition: ReachableCode.h:40
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This class handles loading and caching of source files into memory.
Definition: SourceManager.h:627
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Definition: Expr.h:3770
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Definition: Preprocessor.h:994
Preprocessor.h
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Retrieve the name of the immediate macro expansion.
Definition: Preprocessor.h:1897
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Definition: CFG.h:535
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Definition: CFG.h:576
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Definition: ReachableCode.cpp:308
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Definition: ReachableCode.cpp:448
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Definition: ReachableCode.cpp:474
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Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:208
ReachableCode.h
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Definition: Stmt.h:2539
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Definition: Expr.h:1295
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Definition: CFG.h:866
Expr.h
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Represents a variable declaration or definition.
Definition: Decl.h:874
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SourceLocation getMemberLoc() const
getMemberLoc - Return the location of the "member", in X->F, it is the location of 'F'.
Definition: Expr.h:3353
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An instance of this object exists for each enum constant that is defined.
Definition: Decl.h:3070
ExprObjC.h
ExprCXX.h
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Definition: CFG.cpp:6056
clang::CFGTerminator
Represents CFGBlock terminator statement.
Definition: CFG.h:503
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An array access can be written A[4] or 4[A] (both are equivalent).
Definition: Expr.h:2674
clang::ArraySubscriptExpr::getRHS
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Definition: Expr.h:2678
isBuiltinUnreachable
static bool isBuiltinUnreachable(const Stmt *S)
Definition: ReachableCode.cpp:61
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Definition: Preprocessor.h:998
clang::Expr::IgnoreParenCasts
Expr * IgnoreParenCasts() LLVM_READONLY
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Definition: Expr.cpp:2952
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Definition: Expr.h:3735
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Definition: ParentMap.h:20
clang::UnaryOperator::getOperatorLoc
SourceLocation getOperatorLoc() const
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Definition: Expr.h:2214
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Definition: CFG.h:873
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Definition: CFG.h:132
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Definition: AnalysisDeclContext.h:110
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Definition: ReachableCode.cpp:49
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Definition: CFG.h:109
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Definition: Decl.h:674
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Definition: CFG.h:956
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Definition: Expr.h:3856
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Definition: ReachableCode.h:47
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Definition: CFG.h:937
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Definition: Expr.h:2645
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Definition: Stmt.h:2483
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Definition: Expr.h:3848
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Definition: CFG.h:1331
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Definition: ParentMap.cpp:134
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Definition: SourceLocation.h:103
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Definition: ReachableCode.cpp:41
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Definition: CFG.h:55
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@ UK_Return
Definition: ReachableCode.h:41
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Definition: ReachableCode.cpp:69
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Definition: Expr.h:3939
ParentMap.h
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virtual void HandleUnreachable(UnreachableKind UK, SourceLocation L, SourceRange ConditionVal, SourceRange R1, SourceRange R2)=0
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Definition: Expr.h:2693
isEnumConstant
static bool isEnumConstant(const Expr *Ex)
Definition: ReachableCode.cpp:34
clang::UnaryOperator::getSubExpr
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Definition: Expr.h:2210
clang
Definition: CalledOnceCheck.h:17
clang::reachable_code::UK_Other
@ UK_Other
Definition: ReachableCode.h:44
CFG.h
clang::DeclaratorContext::Block
@ Block
clang::Stmt
Stmt - This represents one statement.
Definition: Stmt.h:69
clang::ComparisonCategoryType::Last
@ Last
clang::UnaryOperator::getOpcode
Opcode getOpcode() const
Definition: Expr.h:2205
clang::BinaryOperator::getRHS
Expr * getRHS() const
Definition: Expr.h:3858
clang::CFG::try_blocks
try_block_range try_blocks() const
Definition: CFG.h:1350
clang::CFGBlock::getTerminatorStmt
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Definition: CFG.h:1050
clang::Stmt::getBeginLoc
SourceLocation getBeginLoc() const LLVM_READONLY
Definition: Stmt.cpp:336
clang::reachable_code::UK_Break
@ UK_Break
Definition: ReachableCode.h:42
scanMaybeReachableFromBlock
static unsigned scanMaybeReachableFromBlock(const CFGBlock *Start, Preprocessor &PP, llvm::BitVector &Reachable)
Definition: ReachableCode.cpp:374
clang::MemberExpr
MemberExpr - [C99 6.5.2.3] Structure and Union Members.
Definition: Expr.h:3164
isConfigurationValue
static bool isConfigurationValue(const ValueDecl *D, Preprocessor &PP)
Definition: ReachableCode.cpp:271
clang::AbstractConditionalOperator::getQuestionLoc
SourceLocation getQuestionLoc() const
Definition: Expr.h:4134
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Definition: AnalysisDeclContext.cpp:213
clang::Expr::IgnoreCasts
Expr * IgnoreCasts() LLVM_READONLY
Skip past any casts which might surround this expression until reaching a fixed point.
Definition: Expr.cpp:2931
clang::Expr
This represents one expression.
Definition: Expr.h:109
isDeadReturn
static bool isDeadReturn(const CFGBlock *B, const Stmt *S)
Definition: ReachableCode.cpp:84
clang::Preprocessor
Engages in a tight little dance with the lexer to efficiently preprocess tokens.
Definition: Preprocessor.h:131
SM
#define SM(sm)
Definition: Cuda.cpp:81
clang::DeclRefExpr
A reference to a declared variable, function, enum, etc.
Definition: Expr.h:1223
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Represents a function declaration or definition.
Definition: Decl.h:1872
clang::reachable_code::ScanReachableFromBlock
unsigned ScanReachableFromBlock(const CFGBlock *Start, llvm::BitVector &Reachable)
ScanReachableFromBlock - Mark all blocks reachable from Start.
Definition: ReachableCode.cpp:672
getTopMostMacro
static SourceLocation getTopMostMacro(SourceLocation Loc, SourceManager &SM)
Definition: ReachableCode.cpp:136
StmtCXX.h
GetUnreachableLoc
static SourceLocation GetUnreachableLoc(const Stmt *S, SourceRange &R1, SourceRange &R2)
Definition: ReachableCode.cpp:544
clang::ReturnStmt
ReturnStmt - This represents a return, optionally of an expression: return; return 4;.
Definition: Stmt.h:2765
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pred_iterator pred_end()
Definition: CFG.h:938
clang::CFGBlock::const_pred_iterator
AdjacentBlocks::const_iterator const_pred_iterator
Definition: CFG.h:924
clang::ObjCBridgedCastExpr::getLParenLoc
SourceLocation getLParenLoc() const
Definition: ExprObjC.h:1649