static void removeLifetimeIntrinsicUsers(AllocaInst *AI) {
// Knowing that this alloca is promotable, we know that it's safe to kill all
// instructions except for load and store.
// FIXME: This function isn't actually specific to lifetime instrinsics. It
// also is redundant with the actual analysis of the loads and stores and
// should be folded into that.
SmallVector<Instruction *, 8> Worklist;
SmallPtrSet<Instruction *, 8> Visited;
SmallVector<Instruction *, 8> Dead;
Worklist.push_back(AI);
do {
Instruction *I = Worklist.pop_back_val();
if (I->use_empty()) {
Dead.push_back(I);
continue;
}
for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
UI != UE; ++UI)
if (!isa<LoadInst>(*UI) && !isa<StoreInst>(*UI) &&
Visited.insert(cast<Instruction>(*UI)))
Worklist.push_back(cast<Instruction>(*UI));
} while (!Worklist.empty());
while (!Dead.empty()) {
Instruction *I = Dead.pop_back_val();
// Don't delete the alloca itself.
if (I == AI)
continue;
// Note that we open code the deletion algorithm here because we know
// apriori that all of the instructions using an alloca that reaches here
// are trivially dead when their use list becomes empty (The only risk are
// lifetime markers which we specifically want to nuke). By coding it here
// we can skip the triviality test and be more efficient.
//
// Null out all of the instruction's operands to see if any operand becomes
// dead as we go.
for (User::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE;
++OI) {
Instruction *Op = dyn_cast<Instruction>(*OI);
if (!Op)
continue;
OI->set(0);
if (!Op->use_empty())
continue;
Dead.push_back(Op);
}
I->eraseFromParent();
}
}
void Preparer::replaceUndefsWithNull(User *I, ValueSet &Replaced) {
if (Replaced.count(I))
return;
Replaced.insert(I);
for (User::op_iterator OI = I->op_begin(); OI != I->op_end(); ++OI) {
Value *V = OI->get();
if (isa<UndefValue>(V) && V->getType()->isPointerTy()) {
OI->set(ConstantPointerNull::get(cast<PointerType>(V->getType())));
}
if (User *I2 = dyn_cast<User>(V)) {
replaceUndefsWithNull(I2, Replaced);
}
}
}