void HexagonEarlyIfConversion::removeBlock(MachineBasicBlock *B) {
DEBUG(dbgs() << "Removing block " << PrintMB(B) << "\n");
// Transfer the immediate dominator information from B to its descendants.
MachineDomTreeNode *N = MDT->getNode(B);
MachineDomTreeNode *IDN = N->getIDom();
if (IDN) {
MachineBasicBlock *IDB = IDN->getBlock();
typedef GraphTraits<MachineDomTreeNode*> GTN;
typedef SmallVector<MachineDomTreeNode*,4> DTNodeVectType;
DTNodeVectType Cn(GTN::child_begin(N), GTN::child_end(N));
for (DTNodeVectType::iterator I = Cn.begin(), E = Cn.end(); I != E; ++I) {
MachineBasicBlock *SB = (*I)->getBlock();
MDT->changeImmediateDominator(SB, IDB);
}
}
while (B->succ_size() > 0)
B->removeSuccessor(B->succ_begin());
for (auto I = B->pred_begin(), E = B->pred_end(); I != E; ++I)
(*I)->removeSuccessor(B);
Deleted.insert(B);
MDT->eraseNode(B);
MachineFunction::iterator BI = B;
MFN->erase(BI);
}
/// Update the dominator tree after if-conversion erased some blocks.
void AArch64ConditionalCompares::updateDomTree(
ArrayRef<MachineBasicBlock *> Removed) {
// convert() removes CmpBB which was previously dominated by Head.
// CmpBB children should be transferred to Head.
MachineDomTreeNode *HeadNode = DomTree->getNode(CmpConv.Head);
for (unsigned i = 0, e = Removed.size(); i != e; ++i) {
MachineDomTreeNode *Node = DomTree->getNode(Removed[i]);
assert(Node != HeadNode && "Cannot erase the head node");
assert(Node->getIDom() == HeadNode && "CmpBB should be dominated by Head");
while (Node->getNumChildren())
DomTree->changeImmediateDominator(Node->getChildren().back(), HeadNode);
DomTree->eraseNode(Removed[i]);
}
}
// This is essentially the same iterative algorithm that SSAUpdater uses,
// except we already have a dominator tree, so we don't have to recompute it.
void LiveRangeCalc::updateSSA() {
assert(Indexes && "Missing SlotIndexes");
assert(DomTree && "Missing dominator tree");
// Interate until convergence.
unsigned Changes;
do {
Changes = 0;
// Propagate live-out values down the dominator tree, inserting phi-defs
// when necessary.
for (SmallVectorImpl<LiveInBlock>::iterator I = LiveIn.begin(),
E = LiveIn.end(); I != E; ++I) {
MachineDomTreeNode *Node = I->DomNode;
// Skip block if the live-in value has already been determined.
if (!Node)
continue;
MachineBasicBlock *MBB = Node->getBlock();
MachineDomTreeNode *IDom = Node->getIDom();
LiveOutPair IDomValue;
// We need a live-in value to a block with no immediate dominator?
// This is probably an unreachable block that has survived somehow.
bool needPHI = !IDom || !Seen.test(IDom->getBlock()->getNumber());
// IDom dominates all of our predecessors, but it may not be their
// immediate dominator. Check if any of them have live-out values that are
// properly dominated by IDom. If so, we need a phi-def here.
if (!needPHI) {
IDomValue = LiveOut[IDom->getBlock()];
// Cache the DomTree node that defined the value.
if (IDomValue.first && !IDomValue.second)
LiveOut[IDom->getBlock()].second = IDomValue.second =
DomTree->getNode(Indexes->getMBBFromIndex(IDomValue.first->def));
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
LiveOutPair &Value = LiveOut[*PI];
if (!Value.first || Value.first == IDomValue.first)
continue;
// Cache the DomTree node that defined the value.
if (!Value.second)
Value.second =
DomTree->getNode(Indexes->getMBBFromIndex(Value.first->def));
// This predecessor is carrying something other than IDomValue.
// It could be because IDomValue hasn't propagated yet, or it could be
// because MBB is in the dominance frontier of that value.
if (DomTree->dominates(IDom, Value.second)) {
needPHI = true;
break;
}
}
}
// The value may be live-through even if Kill is set, as can happen when
// we are called from extendRange. In that case LiveOutSeen is true, and
// LiveOut indicates a foreign or missing value.
LiveOutPair &LOP = LiveOut[MBB];
// Create a phi-def if required.
if (needPHI) {
++Changes;
assert(Alloc && "Need VNInfo allocator to create PHI-defs");
SlotIndex Start, End;
tie(Start, End) = Indexes->getMBBRange(MBB);
VNInfo *VNI = I->LI->getNextValue(Start, *Alloc);
I->Value = VNI;
// This block is done, we know the final value.
I->DomNode = 0;
// Add liveness since updateLiveIns now skips this node.
if (I->Kill.isValid())
I->LI->addRange(LiveRange(Start, I->Kill, VNI));
else {
I->LI->addRange(LiveRange(Start, End, VNI));
LOP = LiveOutPair(VNI, Node);
}
} else if (IDomValue.first) {
// No phi-def here. Remember incoming value.
I->Value = IDomValue.first;
// If the IDomValue is killed in the block, don't propagate through.
if (I->Kill.isValid())
continue;
// Propagate IDomValue if it isn't killed:
// MBB is live-out and doesn't define its own value.
if (LOP.first == IDomValue.first)
continue;
++Changes;
LOP = IDomValue;
}
}
} while (Changes);
}
// This is essentially the same iterative algorithm that SSAUpdater uses,
// except we already have a dominator tree, so we don't have to recompute it.
void LiveRangeCalc::updateSSA() {
assert(Indexes && "Missing SlotIndexes");
assert(DomTree && "Missing dominator tree");
// Interate until convergence.
bool Changed;
do {
Changed = false;
// Propagate live-out values down the dominator tree, inserting phi-defs
// when necessary.
for (LiveInBlock &I : LiveIn) {
MachineDomTreeNode *Node = I.DomNode;
// Skip block if the live-in value has already been determined.
if (!Node)
continue;
MachineBasicBlock *MBB = Node->getBlock();
MachineDomTreeNode *IDom = Node->getIDom();
LiveOutPair IDomValue;
// We need a live-in value to a block with no immediate dominator?
// This is probably an unreachable block that has survived somehow.
bool needPHI = !IDom || !Seen.test(IDom->getBlock()->getNumber());
// IDom dominates all of our predecessors, but it may not be their
// immediate dominator. Check if any of them have live-out values that are
// properly dominated by IDom. If so, we need a phi-def here.
if (!needPHI) {
IDomValue = Map[IDom->getBlock()];
// Cache the DomTree node that defined the value.
if (IDomValue.first && IDomValue.first != &UndefVNI &&
!IDomValue.second) {
Map[IDom->getBlock()].second = IDomValue.second =
DomTree->getNode(Indexes->getMBBFromIndex(IDomValue.first->def));
}
for (MachineBasicBlock *Pred : MBB->predecessors()) {
LiveOutPair &Value = Map[Pred];
if (!Value.first || Value.first == IDomValue.first)
continue;
if (Value.first == &UndefVNI) {
needPHI = true;
break;
}
// Cache the DomTree node that defined the value.
if (!Value.second)
Value.second =
DomTree->getNode(Indexes->getMBBFromIndex(Value.first->def));
// This predecessor is carrying something other than IDomValue.
// It could be because IDomValue hasn't propagated yet, or it could be
// because MBB is in the dominance frontier of that value.
if (DomTree->dominates(IDom, Value.second)) {
needPHI = true;
break;
}
}
}
// The value may be live-through even if Kill is set, as can happen when
// we are called from extendRange. In that case LiveOutSeen is true, and
// LiveOut indicates a foreign or missing value.
LiveOutPair &LOP = Map[MBB];
// Create a phi-def if required.
if (needPHI) {
Changed = true;
assert(Alloc && "Need VNInfo allocator to create PHI-defs");
SlotIndex Start, End;
std::tie(Start, End) = Indexes->getMBBRange(MBB);
LiveRange &LR = I.LR;
VNInfo *VNI = LR.getNextValue(Start, *Alloc);
I.Value = VNI;
// This block is done, we know the final value.
I.DomNode = nullptr;
// Add liveness since updateFromLiveIns now skips this node.
if (I.Kill.isValid()) {
if (VNI)
LR.addSegment(LiveInterval::Segment(Start, I.Kill, VNI));
} else {
if (VNI)
LR.addSegment(LiveInterval::Segment(Start, End, VNI));
LOP = LiveOutPair(VNI, Node);
}
} else if (IDomValue.first && IDomValue.first != &UndefVNI) {
// No phi-def here. Remember incoming value.
I.Value = IDomValue.first;
// If the IDomValue is killed in the block, don't propagate through.
if (I.Kill.isValid())
continue;
// Propagate IDomValue if it isn't killed:
// MBB is live-out and doesn't define its own value.
if (LOP.first == IDomValue.first)
continue;
Changed = true;
LOP = IDomValue;
}
}
} while (Changed);
}
