MDNode *Loop::getLoopID() const {
MDNode *LoopID = nullptr;
if (isLoopSimplifyForm()) {
LoopID = getLoopLatch()->getTerminator()->getMetadata(LLVMContext::MD_loop);
} else {
// Go through each predecessor of the loop header and check the
// terminator for the metadata.
BasicBlock *H = getHeader();
for (BasicBlock *BB : this->blocks()) {
TerminatorInst *TI = BB->getTerminator();
MDNode *MD = nullptr;
// Check if this terminator branches to the loop header.
for (BasicBlock *Successor : TI->successors()) {
if (Successor == H) {
MD = TI->getMetadata(LLVMContext::MD_loop);
break;
}
}
if (!MD)
return nullptr;
if (!LoopID)
LoopID = MD;
else if (MD != LoopID)
return nullptr;
}
}
if (!LoopID || LoopID->getNumOperands() == 0 ||
LoopID->getOperand(0) != LoopID)
return nullptr;
return LoopID;
}
void MemorySSAUpdater::removeBlocks(
const SmallPtrSetImpl<BasicBlock *> &DeadBlocks) {
// First delete all uses of BB in MemoryPhis.
for (BasicBlock *BB : DeadBlocks) {
TerminatorInst *TI = BB->getTerminator();
assert(TI && "Basic block expected to have a terminator instruction");
for (BasicBlock *Succ : TI->successors())
if (!DeadBlocks.count(Succ))
if (MemoryPhi *MP = MSSA->getMemoryAccess(Succ)) {
MP->unorderedDeleteIncomingBlock(BB);
if (MP->getNumIncomingValues() == 1)
removeMemoryAccess(MP);
}
// Drop all references of all accesses in BB
if (MemorySSA::AccessList *Acc = MSSA->getWritableBlockAccesses(BB))
for (MemoryAccess &MA : *Acc)
MA.dropAllReferences();
}
// Next, delete all memory accesses in each block
for (BasicBlock *BB : DeadBlocks) {
MemorySSA::AccessList *Acc = MSSA->getWritableBlockAccesses(BB);
if (!Acc)
continue;
for (auto AB = Acc->begin(), AE = Acc->end(); AB != AE;) {
MemoryAccess *MA = &*AB;
++AB;
MSSA->removeFromLookups(MA);
MSSA->removeFromLists(MA);
}
}
}
void Loop::setLoopID(MDNode *LoopID) const {
assert(LoopID && "Loop ID should not be null");
assert(LoopID->getNumOperands() > 0 && "Loop ID needs at least one operand");
assert(LoopID->getOperand(0) == LoopID && "Loop ID should refer to itself");
if (isLoopSimplifyForm()) {
getLoopLatch()->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopID);
return;
}
BasicBlock *H = getHeader();
for (BasicBlock *BB : this->blocks()) {
TerminatorInst *TI = BB->getTerminator();
for (BasicBlock *Successor : TI->successors()) {
if (Successor == H)
TI->setMetadata(LLVMContext::MD_loop, LoopID);
}
}
}
void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) {
TerminatorInst *TI = getTerminator();
if (!TI)
// Cope with being called on a BasicBlock that doesn't have a terminator
// yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
return;
for (BasicBlock *Succ : TI->successors()) {
// N.B. Succ might not be a complete BasicBlock, so don't assume
// that it ends with a non-phi instruction.
for (iterator II = Succ->begin(), IE = Succ->end(); II != IE; ++II) {
PHINode *PN = dyn_cast<PHINode>(II);
if (!PN)
break;
int i;
while ((i = PN->getBasicBlockIndex(this)) >= 0)
PN->setIncomingBlock(i, New);
}
}
}
void llvm::DeleteDeadBlock(BasicBlock *BB, DeferredDominance *DDT) {
assert((pred_begin(BB) == pred_end(BB) ||
// Can delete self loop.
BB->getSinglePredecessor() == BB) && "Block is not dead!");
TerminatorInst *BBTerm = BB->getTerminator();
std::vector<DominatorTree::UpdateType> Updates;
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
if (DDT)
Updates.reserve(BBTerm->getNumSuccessors());
for (BasicBlock *Succ : BBTerm->successors()) {
Succ->removePredecessor(BB);
if (DDT)
Updates.push_back({DominatorTree::Delete, BB, Succ});
}
// Zap all the instructions in the block.
while (!BB->empty()) {
Instruction &I = BB->back();
// If this instruction is used, replace uses with an arbitrary value.
// Because control flow can't get here, we don't care what we replace the
// value with. Note that since this block is unreachable, and all values
// contained within it must dominate their uses, that all uses will
// eventually be removed (they are themselves dead).
if (!I.use_empty())
I.replaceAllUsesWith(UndefValue::get(I.getType()));
BB->getInstList().pop_back();
}
if (DDT) {
DDT->applyUpdates(Updates);
DDT->deleteBB(BB); // Deferred deletion of BB.
} else {
BB->eraseFromParent(); // Zap the block!
}
}
