-
- SmallPtrSet<BasicBlock*, 64> reachable;
- SmallVector<BasicBlock*, 16> unreachable;
-
- // First, collect the set of reachable blocks ...
- for (df_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 64> >
- DI = df_ext_begin(&F.getEntryBlock(), reachable),
- DE = df_ext_end(&F.getEntryBlock(), reachable); DI != DE; ++DI)
- ; // Deliberately empty, df_ext_iterator will fill in the set.
-
- // ... and then invert it into the list of unreachable ones. These
- // blocks will be removed from the function.
- for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
- if (!reachable.count(FI))
- unreachable.push_back(FI);
-
- // Prepare to remove blocks by removing the PHI node entries for those blocks
- // in their successors, and remove them from reference counting.
- for (SmallVector<BasicBlock*, 16>::iterator UI = unreachable.begin(),
- UE = unreachable.end(); UI != UE; ++UI) {
- BasicBlock* BB = *UI;
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
- SI != SE; ++SI) {
- BasicBlock* succ = *SI;
- BasicBlock::iterator succ_inst = succ->begin();
- while (PHINode* P = dyn_cast<PHINode>(succ_inst)) {
- P->removeIncomingValue(BB);
- ++succ_inst;
- }
- }
-
- BB->dropAllReferences();
- }
-
- // Finally, erase the unreachable blocks.
- for (SmallVector<BasicBlock*, 16>::iterator UI = unreachable.begin(),
- UE = unreachable.end(); UI != UE; ++UI)
- (*UI)->eraseFromParent();
-