void lfort::runUninitializedVariablesAnalysis(
const DeclContext &dc,
const CFG &cfg,
AnalysisDeclContext &ac,
UninitVariablesHandler &handler,
UninitVariablesAnalysisStats &stats) {
CFGBlockValues vals(cfg);
vals.computeSetOfDeclarations(dc);
if (vals.hasNoDeclarations())
return;
stats.NumVariablesAnalyzed = vals.getNumEntries();
// Precompute which expressions are uses and which are initializations.
ClassifyRefs classification(ac);
cfg.VisitBlockStmts(classification);
// Mark all variables uninitialized at the entry.
const CFGBlock &entry = cfg.getEntry();
ValueVector &vec = vals.getValueVector(&entry);
const unsigned n = vals.getNumEntries();
for (unsigned j = 0; j < n ; ++j) {
vec[j] = Uninitialized;
}
// Proceed with the workist.
DataflowWorklist worklist(cfg, *ac.getAnalysis<PostOrderCFGView>());
llvm::BitVector previouslyVisited(cfg.getNumBlockIDs());
worklist.enqueueSuccessors(&cfg.getEntry());
llvm::BitVector wasAnalyzed(cfg.getNumBlockIDs(), false);
wasAnalyzed[cfg.getEntry().getBlockID()] = true;
PruneBlocksHandler PBH(cfg.getNumBlockIDs());
while (const CFGBlock *block = worklist.dequeue()) {
PBH.currentBlock = block->getBlockID();
// Did the block change?
bool changed = runOnBlock(block, cfg, ac, vals,
classification, wasAnalyzed, PBH);
++stats.NumBlockVisits;
if (changed || !previouslyVisited[block->getBlockID()])
worklist.enqueueSuccessors(block);
previouslyVisited[block->getBlockID()] = true;
}
if (!PBH.hadAnyUse)
return;
// Run through the blocks one more time, and report uninitialized variabes.
for (CFG::const_iterator BI = cfg.begin(), BE = cfg.end(); BI != BE; ++BI) {
const CFGBlock *block = *BI;
if (PBH.hadUse[block->getBlockID()]) {
runOnBlock(block, cfg, ac, vals, classification, wasAnalyzed, handler);
++stats.NumBlockVisits;
}
}
}
void clang::runUninitializedVariablesAnalysis(
const DeclContext &dc,
const CFG &cfg,
AnalysisDeclContext &ac,
UninitVariablesHandler &handler,
UninitVariablesAnalysisStats &stats) {
CFGBlockValues vals(cfg);
vals.computeSetOfDeclarations(dc);
if (vals.hasNoDeclarations())
return;
stats.NumVariablesAnalyzed = vals.getNumEntries();
// Mark all variables uninitialized at the entry.
const CFGBlock &entry = cfg.getEntry();
for (CFGBlock::const_succ_iterator i = entry.succ_begin(),
e = entry.succ_end(); i != e; ++i) {
if (const CFGBlock *succ = *i) {
ValueVector &vec = vals.getValueVector(&entry, succ);
const unsigned n = vals.getNumEntries();
for (unsigned j = 0; j < n ; ++j) {
vec[j] = Uninitialized;
}
}
}
// Proceed with the workist.
DataflowWorklist worklist(cfg);
llvm::BitVector previouslyVisited(cfg.getNumBlockIDs());
worklist.enqueueSuccessors(&cfg.getEntry());
llvm::BitVector wasAnalyzed(cfg.getNumBlockIDs(), false);
wasAnalyzed[cfg.getEntry().getBlockID()] = true;
while (const CFGBlock *block = worklist.dequeue()) {
// Did the block change?
bool changed = runOnBlock(block, cfg, ac, vals, wasAnalyzed);
++stats.NumBlockVisits;
if (changed || !previouslyVisited[block->getBlockID()])
worklist.enqueueSuccessors(block);
previouslyVisited[block->getBlockID()] = true;
}
// Run through the blocks one more time, and report uninitialized variabes.
for (CFG::const_iterator BI = cfg.begin(), BE = cfg.end(); BI != BE; ++BI) {
const CFGBlock *block = *BI;
if (wasAnalyzed[block->getBlockID()]) {
runOnBlock(block, cfg, ac, vals, wasAnalyzed, &handler);
++stats.NumBlockVisits;
}
}
}
void FindUnreachableCode(AnalysisDeclContext &AC, Preprocessor &PP,
Callback &CB) {
CFG *cfg = AC.getCFG();
if (!cfg)
return;
// Scan for reachable blocks from the entrance of the CFG.
// If there are no unreachable blocks, we're done.
llvm::BitVector reachable(cfg->getNumBlockIDs());
unsigned numReachable =
scanMaybeReachableFromBlock(&cfg->getEntry(), PP, reachable);
if (numReachable == cfg->getNumBlockIDs())
return;
// If there aren't explicit EH edges, we should include the 'try' dispatch
// blocks as roots.
if (!AC.getCFGBuildOptions().AddEHEdges) {
for (CFG::try_block_iterator I = cfg->try_blocks_begin(),
E = cfg->try_blocks_end() ; I != E; ++I) {
numReachable += scanMaybeReachableFromBlock(*I, PP, reachable);
}
if (numReachable == cfg->getNumBlockIDs())
return;
}
// There are some unreachable blocks. We need to find the root blocks that
// contain code that should be considered unreachable.
for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
const CFGBlock *block = *I;
// A block may have been marked reachable during this loop.
if (reachable[block->getBlockID()])
continue;
DeadCodeScan DS(reachable, PP);
numReachable += DS.scanBackwards(block, CB);
if (numReachable == cfg->getNumBlockIDs())
return;
}
}
CFGReverseBlockReachabilityAnalysis::CFGReverseBlockReachabilityAnalysis(const CFG &cfg)
: analyzed(cfg.getNumBlockIDs(), false) {}
/// CheckFallThrough - Check that we don't fall off the end of a
/// Statement that should return a value.
///
/// \returns AlwaysFallThrough iff we always fall off the end of the statement,
/// MaybeFallThrough iff we might or might not fall off the end,
/// NeverFallThroughOrReturn iff we never fall off the end of the statement or
/// return. We assume NeverFallThrough iff we never fall off the end of the
/// statement but we may return. We assume that functions not marked noreturn
/// will return.
static ControlFlowKind CheckFallThrough(AnalysisContext &AC) {
CFG *cfg = AC.getCFG();
if (cfg == 0) return UnknownFallThrough;
// The CFG leaves in dead things, and we don't want the dead code paths to
// confuse us, so we mark all live things first.
llvm::BitVector live(cfg->getNumBlockIDs());
unsigned count = reachable_code::ScanReachableFromBlock(cfg->getEntry(),
live);
bool AddEHEdges = AC.getAddEHEdges();
if (!AddEHEdges && count != cfg->getNumBlockIDs())
// When there are things remaining dead, and we didn't add EH edges
// from CallExprs to the catch clauses, we have to go back and
// mark them as live.
for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
CFGBlock &b = **I;
if (!live[b.getBlockID()]) {
if (b.pred_begin() == b.pred_end()) {
if (b.getTerminator() && isa<CXXTryStmt>(b.getTerminator()))
// When not adding EH edges from calls, catch clauses
// can otherwise seem dead. Avoid noting them as dead.
count += reachable_code::ScanReachableFromBlock(b, live);
continue;
}
}
}
// Now we know what is live, we check the live precessors of the exit block
// and look for fall through paths, being careful to ignore normal returns,
// and exceptional paths.
bool HasLiveReturn = false;
bool HasFakeEdge = false;
bool HasPlainEdge = false;
bool HasAbnormalEdge = false;
for (CFGBlock::pred_iterator I=cfg->getExit().pred_begin(),
E = cfg->getExit().pred_end();
I != E;
++I) {
CFGBlock& B = **I;
if (!live[B.getBlockID()])
continue;
if (B.size() == 0) {
if (B.getTerminator() && isa<CXXTryStmt>(B.getTerminator())) {
HasAbnormalEdge = true;
continue;
}
// A labeled empty statement, or the entry block...
HasPlainEdge = true;
continue;
}
Stmt *S = B[B.size()-1];
if (isa<ReturnStmt>(S)) {
HasLiveReturn = true;
continue;
}
if (isa<ObjCAtThrowStmt>(S)) {
HasFakeEdge = true;
continue;
}
if (isa<CXXThrowExpr>(S)) {
HasFakeEdge = true;
continue;
}
if (const AsmStmt *AS = dyn_cast<AsmStmt>(S)) {
if (AS->isMSAsm()) {
HasFakeEdge = true;
HasLiveReturn = true;
continue;
}
}
if (isa<CXXTryStmt>(S)) {
HasAbnormalEdge = true;
continue;
}
bool NoReturnEdge = false;
if (CallExpr *C = dyn_cast<CallExpr>(S)) {
if (std::find(B.succ_begin(), B.succ_end(), &cfg->getExit())
== B.succ_end()) {
HasAbnormalEdge = true;
continue;
}
Expr *CEE = C->getCallee()->IgnoreParenCasts();
if (getFunctionExtInfo(CEE->getType()).getNoReturn()) {
NoReturnEdge = true;
HasFakeEdge = true;
} else if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(CEE)) {
ValueDecl *VD = DRE->getDecl();
if (VD->hasAttr<NoReturnAttr>()) {
NoReturnEdge = true;
HasFakeEdge = true;
}
}
}
// FIXME: Remove this hack once temporaries and their destructors are
// modeled correctly by the CFG.
if (CXXExprWithTemporaries *E = dyn_cast<CXXExprWithTemporaries>(S)) {
for (unsigned I = 0, N = E->getNumTemporaries(); I != N; ++I) {
const FunctionDecl *FD = E->getTemporary(I)->getDestructor();
if (FD->hasAttr<NoReturnAttr>() ||
FD->getType()->getAs<FunctionType>()->getNoReturnAttr()) {
NoReturnEdge = true;
HasFakeEdge = true;
break;
}
}
}
// FIXME: Add noreturn message sends.
if (NoReturnEdge == false)
HasPlainEdge = true;
}
if (!HasPlainEdge) {
if (HasLiveReturn)
return NeverFallThrough;
return NeverFallThroughOrReturn;
}
if (HasAbnormalEdge || HasFakeEdge || HasLiveReturn)
return MaybeFallThrough;
// This says AlwaysFallThrough for calls to functions that are not marked
// noreturn, that don't return. If people would like this warning to be more
// accurate, such functions should be marked as noreturn.
return AlwaysFallThrough;
}
/// \brief Check a function's CFG for thread-safety violations.
///
/// We traverse the blocks in the CFG, compute the set of mutexes that are held
/// at the end of each block, and issue warnings for thread safety violations.
/// Each block in the CFG is traversed exactly once.
void runThreadSafetyAnalysis(AnalysisContext &AC,
ThreadSafetyHandler &Handler) {
CFG *CFGraph = AC.getCFG();
if (!CFGraph) return;
const NamedDecl *D = dyn_cast_or_null<NamedDecl>(AC.getDecl());
if (!D)
return; // Ignore anonymous functions for now.
if (D->getAttr<NoThreadSafetyAnalysisAttr>())
return;
Lockset::Factory LocksetFactory;
// FIXME: Swith to SmallVector? Otherwise improve performance impact?
std::vector<Lockset> EntryLocksets(CFGraph->getNumBlockIDs(),
LocksetFactory.getEmptyMap());
std::vector<Lockset> ExitLocksets(CFGraph->getNumBlockIDs(),
LocksetFactory.getEmptyMap());
// We need to explore the CFG via a "topological" ordering.
// That way, we will be guaranteed to have information about required
// predecessor locksets when exploring a new block.
TopologicallySortedCFG SortedGraph(CFGraph);
CFGBlockSet VisitedBlocks(CFGraph);
if (!SortedGraph.empty() && D->hasAttrs()) {
const CFGBlock *FirstBlock = *SortedGraph.begin();
Lockset &InitialLockset = EntryLocksets[FirstBlock->getBlockID()];
const AttrVec &ArgAttrs = D->getAttrs();
for(unsigned i = 0; i < ArgAttrs.size(); ++i) {
Attr *Attr = ArgAttrs[i];
SourceLocation AttrLoc = Attr->getLocation();
if (SharedLocksRequiredAttr *SLRAttr
= dyn_cast<SharedLocksRequiredAttr>(Attr)) {
for (SharedLocksRequiredAttr::args_iterator
SLRIter = SLRAttr->args_begin(),
SLREnd = SLRAttr->args_end(); SLRIter != SLREnd; ++SLRIter)
InitialLockset = addLock(Handler, LocksetFactory, InitialLockset,
*SLRIter, D, LK_Shared,
AttrLoc);
} else if (ExclusiveLocksRequiredAttr *ELRAttr
= dyn_cast<ExclusiveLocksRequiredAttr>(Attr)) {
for (ExclusiveLocksRequiredAttr::args_iterator
ELRIter = ELRAttr->args_begin(),
ELREnd = ELRAttr->args_end(); ELRIter != ELREnd; ++ELRIter)
InitialLockset = addLock(Handler, LocksetFactory, InitialLockset,
*ELRIter, D, LK_Exclusive,
AttrLoc);
}
}
}
for (TopologicallySortedCFG::iterator I = SortedGraph.begin(),
E = SortedGraph.end(); I!= E; ++I) {
const CFGBlock *CurrBlock = *I;
int CurrBlockID = CurrBlock->getBlockID();
VisitedBlocks.insert(CurrBlock);
// Use the default initial lockset in case there are no predecessors.
Lockset &Entryset = EntryLocksets[CurrBlockID];
Lockset &Exitset = ExitLocksets[CurrBlockID];
// Iterate through the predecessor blocks and warn if the lockset for all
// predecessors is not the same. We take the entry lockset of the current
// block to be the intersection of all previous locksets.
// FIXME: By keeping the intersection, we may output more errors in future
// for a lock which is not in the intersection, but was in the union. We
// may want to also keep the union in future. As an example, let's say
// the intersection contains Mutex L, and the union contains L and M.
// Later we unlock M. At this point, we would output an error because we
// never locked M; although the real error is probably that we forgot to
// lock M on all code paths. Conversely, let's say that later we lock M.
// In this case, we should compare against the intersection instead of the
// union because the real error is probably that we forgot to unlock M on
// all code paths.
bool LocksetInitialized = false;
for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
PE = CurrBlock->pred_end(); PI != PE; ++PI) {
// if *PI -> CurrBlock is a back edge
if (*PI == 0 || !VisitedBlocks.alreadySet(*PI))
continue;
int PrevBlockID = (*PI)->getBlockID();
if (!LocksetInitialized) {
Entryset = ExitLocksets[PrevBlockID];
LocksetInitialized = true;
} else {
Entryset = intersectAndWarn(Handler, Entryset,
ExitLocksets[PrevBlockID], LocksetFactory,
LEK_LockedSomePredecessors);
}
}
BuildLockset LocksetBuilder(Handler, Entryset, LocksetFactory);
for (CFGBlock::const_iterator BI = CurrBlock->begin(),
BE = CurrBlock->end(); BI != BE; ++BI) {
if (const CFGStmt *CfgStmt = dyn_cast<CFGStmt>(&*BI))
LocksetBuilder.Visit(const_cast<Stmt*>(CfgStmt->getStmt()));
}
Exitset = LocksetBuilder.getLockset();
// For every back edge from CurrBlock (the end of the loop) to another block
// (FirstLoopBlock) we need to check that the Lockset of Block is equal to
// the one held at the beginning of FirstLoopBlock. We can look up the
// Lockset held at the beginning of FirstLoopBlock in the EntryLockSets map.
for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
SE = CurrBlock->succ_end(); SI != SE; ++SI) {
// if CurrBlock -> *SI is *not* a back edge
if (*SI == 0 || !VisitedBlocks.alreadySet(*SI))
continue;
CFGBlock *FirstLoopBlock = *SI;
Lockset PreLoop = EntryLocksets[FirstLoopBlock->getBlockID()];
Lockset LoopEnd = ExitLocksets[CurrBlockID];
intersectAndWarn(Handler, LoopEnd, PreLoop, LocksetFactory,
LEK_LockedSomeLoopIterations);
}
}
Lockset InitialLockset = EntryLocksets[CFGraph->getEntry().getBlockID()];
Lockset FinalLockset = ExitLocksets[CFGraph->getExit().getBlockID()];
// FIXME: Should we call this function for all blocks which exit the function?
intersectAndWarn(Handler, InitialLockset, FinalLockset, LocksetFactory,
LEK_LockedAtEndOfFunction);
}
LiveVariables *
LiveVariables::computeLiveness(AnalysisDeclContext &AC,
bool killAtAssign) {
// No CFG? Bail out.
CFG *cfg = AC.getCFG();
if (!cfg)
return nullptr;
// The analysis currently has scalability issues for very large CFGs.
// Bail out if it looks too large.
if (cfg->getNumBlockIDs() > 300000)
return nullptr;
LiveVariablesImpl *LV = new LiveVariablesImpl(AC, killAtAssign);
// Construct the dataflow worklist. Enqueue the exit block as the
// start of the analysis.
DataflowWorklist worklist(*cfg, AC);
llvm::BitVector everAnalyzedBlock(cfg->getNumBlockIDs());
// FIXME: we should enqueue using post order.
for (CFG::const_iterator it = cfg->begin(), ei = cfg->end(); it != ei; ++it) {
const CFGBlock *block = *it;
worklist.enqueueBlock(block);
// FIXME: Scan for DeclRefExprs using in the LHS of an assignment.
// We need to do this because we lack context in the reverse analysis
// to determine if a DeclRefExpr appears in such a context, and thus
// doesn't constitute a "use".
if (killAtAssign)
for (CFGBlock::const_iterator bi = block->begin(), be = block->end();
bi != be; ++bi) {
if (Optional<CFGStmt> cs = bi->getAs<CFGStmt>()) {
if (const BinaryOperator *BO =
dyn_cast<BinaryOperator>(cs->getStmt())) {
if (BO->getOpcode() == BO_Assign) {
if (const DeclRefExpr *DR =
dyn_cast<DeclRefExpr>(BO->getLHS()->IgnoreParens())) {
LV->inAssignment[DR] = 1;
}
}
}
}
}
}
while (const CFGBlock *block = worklist.dequeue()) {
// Determine if the block's end value has changed. If not, we
// have nothing left to do for this block.
LivenessValues &prevVal = LV->blocksEndToLiveness[block];
// Merge the values of all successor blocks.
LivenessValues val;
for (CFGBlock::const_succ_iterator it = block->succ_begin(),
ei = block->succ_end(); it != ei; ++it) {
if (const CFGBlock *succ = *it) {
val = LV->merge(val, LV->blocksBeginToLiveness[succ]);
}
}
if (!everAnalyzedBlock[block->getBlockID()])
everAnalyzedBlock[block->getBlockID()] = true;
else if (prevVal.equals(val))
continue;
prevVal = val;
// Update the dataflow value for the start of this block.
LV->blocksBeginToLiveness[block] = LV->runOnBlock(block, val);
// Enqueue the value to the predecessors.
worklist.enqueuePredecessors(block);
}
return new LiveVariables(LV);
}
/// CheckFallThrough - Check that we don't fall off the end of a
/// Statement that should return a value.
///
/// \returns AlwaysFallThrough iff we always fall off the end of the statement,
/// MaybeFallThrough iff we might or might not fall off the end,
/// NeverFallThroughOrReturn iff we never fall off the end of the statement or
/// return. We assume NeverFallThrough iff we never fall off the end of the
/// statement but we may return. We assume that functions not marked noreturn
/// will return.
static ControlFlowKind CheckFallThrough(AnalysisContext &AC) {
CFG *cfg = AC.getCFG();
if (cfg == 0) return UnknownFallThrough;
// The CFG leaves in dead things, and we don't want the dead code paths to
// confuse us, so we mark all live things first.
llvm::BitVector live(cfg->getNumBlockIDs());
unsigned count = reachable_code::ScanReachableFromBlock(cfg->getEntry(),
live);
bool AddEHEdges = AC.getAddEHEdges();
if (!AddEHEdges && count != cfg->getNumBlockIDs())
// When there are things remaining dead, and we didn't add EH edges
// from CallExprs to the catch clauses, we have to go back and
// mark them as live.
for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
CFGBlock &b = **I;
if (!live[b.getBlockID()]) {
if (b.pred_begin() == b.pred_end()) {
if (b.getTerminator() && isa<CXXTryStmt>(b.getTerminator()))
// When not adding EH edges from calls, catch clauses
// can otherwise seem dead. Avoid noting them as dead.
count += reachable_code::ScanReachableFromBlock(b, live);
continue;
}
}
}
// Now we know what is live, we check the live precessors of the exit block
// and look for fall through paths, being careful to ignore normal returns,
// and exceptional paths.
bool HasLiveReturn = false;
bool HasFakeEdge = false;
bool HasPlainEdge = false;
bool HasAbnormalEdge = false;
// Ignore default cases that aren't likely to be reachable because all
// enums in a switch(X) have explicit case statements.
CFGBlock::FilterOptions FO;
FO.IgnoreDefaultsWithCoveredEnums = 1;
for (CFGBlock::filtered_pred_iterator
I = cfg->getExit().filtered_pred_start_end(FO); I.hasMore(); ++I) {
const CFGBlock& B = **I;
if (!live[B.getBlockID()])
continue;
// Destructors can appear after the 'return' in the CFG. This is
// normal. We need to look pass the destructors for the return
// statement (if it exists).
CFGBlock::const_reverse_iterator ri = B.rbegin(), re = B.rend();
bool hasNoReturnDtor = false;
for ( ; ri != re ; ++ri) {
CFGElement CE = *ri;
// FIXME: The right solution is to just sever the edges in the
// CFG itself.
if (const CFGImplicitDtor *iDtor = ri->getAs<CFGImplicitDtor>())
if (iDtor->isNoReturn(AC.getASTContext())) {
hasNoReturnDtor = true;
HasFakeEdge = true;
break;
}
if (isa<CFGStmt>(CE))
break;
}
if (hasNoReturnDtor)
continue;
// No more CFGElements in the block?
if (ri == re) {
if (B.getTerminator() && isa<CXXTryStmt>(B.getTerminator())) {
HasAbnormalEdge = true;
continue;
}
// A labeled empty statement, or the entry block...
HasPlainEdge = true;
continue;
}
CFGStmt CS = cast<CFGStmt>(*ri);
Stmt *S = CS.getStmt();
if (isa<ReturnStmt>(S)) {
HasLiveReturn = true;
continue;
}
if (isa<ObjCAtThrowStmt>(S)) {
HasFakeEdge = true;
continue;
}
if (isa<CXXThrowExpr>(S)) {
HasFakeEdge = true;
continue;
}
if (const AsmStmt *AS = dyn_cast<AsmStmt>(S)) {
if (AS->isMSAsm()) {
HasFakeEdge = true;
HasLiveReturn = true;
continue;
}
}
if (isa<CXXTryStmt>(S)) {
HasAbnormalEdge = true;
continue;
}
bool NoReturnEdge = false;
if (CallExpr *C = dyn_cast<CallExpr>(S)) {
if (std::find(B.succ_begin(), B.succ_end(), &cfg->getExit())
== B.succ_end()) {
HasAbnormalEdge = true;
continue;
}
Expr *CEE = C->getCallee()->IgnoreParenCasts();
QualType calleeType = CEE->getType();
if (calleeType == AC.getASTContext().BoundMemberTy) {
calleeType = Expr::findBoundMemberType(CEE);
assert(!calleeType.isNull() && "analyzing unresolved call?");
}
if (getFunctionExtInfo(calleeType).getNoReturn()) {
NoReturnEdge = true;
HasFakeEdge = true;
} else if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(CEE)) {
ValueDecl *VD = DRE->getDecl();
if (VD->hasAttr<NoReturnAttr>()) {
NoReturnEdge = true;
HasFakeEdge = true;
}
}
}
// FIXME: Add noreturn message sends.
if (NoReturnEdge == false)
HasPlainEdge = true;
}
if (!HasPlainEdge) {
if (HasLiveReturn)
return NeverFallThrough;
return NeverFallThroughOrReturn;
}
if (HasAbnormalEdge || HasFakeEdge || HasLiveReturn)
return MaybeFallThrough;
// This says AlwaysFallThrough for calls to functions that are not marked
// noreturn, that don't return. If people would like this warning to be more
// accurate, such functions should be marked as noreturn.
return AlwaysFallThrough;
}
void FindUnreachableCode(AnalysisContext &AC, Callback &CB) {
CFG *cfg = AC.getCFG();
if (!cfg)
return;
// Scan for reachable blocks.
llvm::BitVector reachable(cfg->getNumBlockIDs());
unsigned numReachable = ScanReachableFromBlock(cfg->getEntry(), reachable);
// If there are no unreachable blocks, we're done.
if (numReachable == cfg->getNumBlockIDs())
return;
SourceRange R1, R2;
llvm::SmallVector<ErrLoc, 24> lines;
bool AddEHEdges = AC.getAddEHEdges();
// First, give warnings for blocks with no predecessors, as they
// can't be part of a loop.
for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
CFGBlock &b = **I;
if (!reachable[b.getBlockID()]) {
if (b.pred_empty()) {
if (!AddEHEdges
&& dyn_cast_or_null<CXXTryStmt>(b.getTerminator().getStmt())) {
// When not adding EH edges from calls, catch clauses
// can otherwise seem dead. Avoid noting them as dead.
numReachable += ScanReachableFromBlock(b, reachable);
continue;
}
SourceLocation c = GetUnreachableLoc(b, R1, R2);
if (!c.isValid()) {
// Blocks without a location can't produce a warning, so don't mark
// reachable blocks from here as live.
reachable.set(b.getBlockID());
++numReachable;
continue;
}
lines.push_back(ErrLoc(c, R1, R2));
// Avoid excessive errors by marking everything reachable from here
numReachable += ScanReachableFromBlock(b, reachable);
}
}
}
if (numReachable < cfg->getNumBlockIDs()) {
// And then give warnings for the tops of loops.
for (CFG::iterator I = cfg->begin(), E = cfg->end(); I != E; ++I) {
CFGBlock &b = **I;
if (!reachable[b.getBlockID()])
// Avoid excessive errors by marking everything reachable from here
lines.push_back(ErrLoc(MarkLiveTop(&b, reachable,
AC.getASTContext().getSourceManager()),
SourceRange(), SourceRange()));
}
}
llvm::array_pod_sort(lines.begin(), lines.end(), LineCmp);
for (llvm::SmallVectorImpl<ErrLoc>::iterator I=lines.begin(), E=lines.end();
I != E; ++I)
if (I->Loc.isValid())
CB.HandleUnreachable(I->Loc, I->R1, I->R2);
}