// Move all PHI nodes in BB to Succ if they are alive, otherwise
// delete them.
while (PHINode *PN = dyn_cast<PHINode>(&BB->front()))
- if (PN->use_empty())
- BB->getInstList().erase(BB->begin()); // Nuke instruction.
- else {
+ if (PN->use_empty() || Succ->getSinglePredecessor() == 0) {
+ // We can only move the PHI node into Succ if BB dominates Succ.
+ // Since BB only has a single successor (Succ), the PHI nodes
+ // will dominate Succ, unless Succ has multiple predecessors. In
+ // this case, the PHIs are either dead, or have references in dead
+ // blocks. In either case, we can just remove them.
+ if (!PN->use_empty()) // Uses in dead block?
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ PN->eraseFromParent(); // Nuke instruction.
+ } else {
// The instruction is alive, so this means that Succ must have
// *ONLY* had BB as a predecessor, and the PHI node is still valid
// now. Simply move it into Succ, because we know that BB