bind_obj(this, &ADCE::markTerminatorLive));
}
- // If this basic block is live, then the terminator must be as well!
- markTerminatorLive(BB);
+ // If this basic block is live, and it ends in an unconditional branch, then
+ // the branch is alive as well...
+ if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()))
+ if (BI->isUnconditional())
+ markTerminatorLive(BB);
}
// dropReferencesOfDeadInstructionsInLiveBlock - Loop over all of the
NewEntry->getInstList().push_back(new BranchInst(&Func->front()));
Func->getBasicBlockList().push_front(NewEntry);
AliveBlocks.insert(NewEntry); // This block is always alive!
+ LiveSet.insert(NewEntry->getTerminator()); // The branch is live
}
// Loop over all of the alive blocks in the function. If any successor
BasicBlock *BB = I;
TerminatorInst *TI = BB->getTerminator();
+ // If the terminator instruction is alive, but the block it is contained
+ // in IS alive, this means that this terminator is a conditional branch
+ // on a condition that doesn't matter. Make it an unconditional branch
+ // to ONE of the successors. This has the side effect of dropping a use
+ // of the conditional value, which may also be dead.
+ if (!LiveSet.count(TI)) {
+ assert(TI->getNumSuccessors() > 1 && "Not a conditional?");
+ BranchInst *NB = new BranchInst(TI->getSuccessor(0), TI);
+
+ // Remove entries from PHI nodes to avoid confusing ourself later...
+ for (unsigned i = 1, e = TI->getNumSuccessors(); i != e; ++i)
+ TI->getSuccessor(i)->removePredecessor(BB);
+
+ BB->getInstList().erase(TI);
+ TI = NB;
+ }
+
// Loop over all of the successors, looking for ones that are not alive.
// We cannot save the number of successors in the terminator instruction
// here because we may remove them if we don't have a postdominator...