void FindUnreachableCode(AnalysisContext &AC, 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 = ScanReachableFromBlock(&cfg->getEntry(), 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 += ScanReachableFromBlock(*I, 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);
numReachable += DS.scanBackwards(block, CB);
if (numReachable == cfg->getNumBlockIDs())
return;
}
}
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);
}
