/// CloneDominatorInfo - Clone basicblock's dominator tree and, if available,
/// dominance info. It is expected that basic block is already cloned.
static void CloneDominatorInfo(BasicBlock *BB,
DenseMap<const Value *, Value *> &ValueMap,
DominatorTree *DT,
DominanceFrontier *DF) {
assert (DT && "DominatorTree is not available");
DenseMap<const Value *, Value*>::iterator BI = ValueMap.find(BB);
assert (BI != ValueMap.end() && "BasicBlock clone is missing");
BasicBlock *NewBB = cast<BasicBlock>(BI->second);
// NewBB already got dominator info.
if (DT->getNode(NewBB))
return;
assert (DT->getNode(BB) && "BasicBlock does not have dominator info");
// Entry block is not expected here. Infinite loops are not to cloned.
assert (DT->getNode(BB)->getIDom() && "BasicBlock does not have immediate dominator");
BasicBlock *BBDom = DT->getNode(BB)->getIDom()->getBlock();
// NewBB's dominator is either BB's dominator or BB's dominator's clone.
BasicBlock *NewBBDom = BBDom;
DenseMap<const Value *, Value*>::iterator BBDomI = ValueMap.find(BBDom);
if (BBDomI != ValueMap.end()) {
NewBBDom = cast<BasicBlock>(BBDomI->second);
if (!DT->getNode(NewBBDom))
CloneDominatorInfo(BBDom, ValueMap, DT, DF);
}
DT->addNewBlock(NewBB, NewBBDom);
// Copy cloned dominance frontiner set
if (DF) {
DominanceFrontier::DomSetType NewDFSet;
DominanceFrontier::iterator DFI = DF->find(BB);
if ( DFI != DF->end()) {
DominanceFrontier::DomSetType S = DFI->second;
for (DominanceFrontier::DomSetType::iterator I = S.begin(), E = S.end();
I != E; ++I) {
BasicBlock *DB = *I;
DenseMap<const Value*, Value*>::iterator IDM = ValueMap.find(DB);
if (IDM != ValueMap.end())
NewDFSet.insert(cast<BasicBlock>(IDM->second));
else
NewDFSet.insert(DB);
}
}
DF->addBasicBlock(NewBB, NewDFSet);
}
}
// NewBB is split and now it has one successor. Update dominace frontier to
// reflect this change.
void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
assert(NewBB->getTerminator()->getNumSuccessors() == 1
&& "NewBB should have a single successor!");
BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
SmallVector<BasicBlock*, 8> PredBlocks;
for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
PI != PE; ++PI)
PredBlocks.push_back(*PI);
if (PredBlocks.empty())
// If NewBB does not have any predecessors then it is a entry block.
// In this case, NewBB and its successor NewBBSucc dominates all
// other blocks.
return;
// NewBBSucc inherits original NewBB frontier.
DominanceFrontier::iterator NewBBI = find(NewBB);
if (NewBBI != end()) {
DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
DominanceFrontier::DomSetType NewBBSuccSet;
NewBBSuccSet.insert(NewBBSet.begin(), NewBBSet.end());
addBasicBlock(NewBBSucc, NewBBSuccSet);
}
// If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
// DF(PredBlocks[0]) without the stuff that the new block does not dominate
// a predecessor of.
DominatorTree &DT = getAnalysis<DominatorTree>();
if (DT.dominates(NewBB, NewBBSucc)) {
DominanceFrontier::iterator DFI = find(PredBlocks[0]);
if (DFI != end()) {
DominanceFrontier::DomSetType Set = DFI->second;
// Filter out stuff in Set that we do not dominate a predecessor of.
for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
E = Set.end(); SetI != E;) {
bool DominatesPred = false;
for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
PI != E; ++PI)
if (DT.dominates(NewBB, *PI))
DominatesPred = true;
if (!DominatesPred)
Set.erase(SetI++);
else
++SetI;
}
if (NewBBI != end()) {
for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
E = Set.end(); SetI != E; ++SetI) {
BasicBlock *SB = *SetI;
addToFrontier(NewBBI, SB);
}
} else
addBasicBlock(NewBB, Set);
}
} else {
// DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
// NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
// NewBBSucc)). NewBBSucc is the single successor of NewBB.
DominanceFrontier::DomSetType NewDFSet;
NewDFSet.insert(NewBBSucc);
addBasicBlock(NewBB, NewDFSet);
}
// Now we must loop over all of the dominance frontiers in the function,
// replacing occurrences of NewBBSucc with NewBB in some cases. All
// blocks that dominate a block in PredBlocks and contained NewBBSucc in
// their dominance frontier must be updated to contain NewBB instead.
//
for (Function::iterator FI = NewBB->getParent()->begin(),
FE = NewBB->getParent()->end(); FI != FE; ++FI) {
DominanceFrontier::iterator DFI = find(FI);
if (DFI == end()) continue; // unreachable block.
// Only consider nodes that have NewBBSucc in their dominator frontier.
if (!DFI->second.count(NewBBSucc)) continue;
// Verify whether this block dominates a block in predblocks. If not, do
// not update it.
bool BlockDominatesAny = false;
for (SmallVectorImpl<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
BE = PredBlocks.end(); BI != BE; ++BI) {
if (DT.dominates(FI, *BI)) {
BlockDominatesAny = true;
break;
}
}
// If NewBBSucc should not stay in our dominator frontier, remove it.
// We remove it unless there is a predecessor of NewBBSucc that we
// dominate, but we don't strictly dominate NewBBSucc.
bool ShouldRemove = true;
if ((BasicBlock*)FI == NewBBSucc || !DT.dominates(FI, NewBBSucc)) {
// Okay, we know that PredDom does not strictly dominate NewBBSucc.
// Check to see if it dominates any predecessors of NewBBSucc.
for (pred_iterator PI = pred_begin(NewBBSucc),
E = pred_end(NewBBSucc); PI != E; ++PI)
if (DT.dominates(FI, *PI)) {
ShouldRemove = false;
break;
}
}
if (ShouldRemove)
removeFromFrontier(DFI, NewBBSucc);
if (BlockDominatesAny && (&*FI == NewBB || !DT.dominates(FI, NewBB)))
addToFrontier(DFI, NewBB);
}
}
/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
/// split the critical edge. This will update DominatorTree and
/// DominatorFrontier information if it is available, thus calling this pass
/// will not invalidate either of them. This returns the new block if the edge
/// was split, null otherwise.
///
/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
/// specified successor will be merged into the same critical edge block.
/// This is most commonly interesting with switch instructions, which may
/// have many edges to any one destination. This ensures that all edges to that
/// dest go to one block instead of each going to a different block, but isn't
/// the standard definition of a "critical edge".
///
/// It is invalid to call this function on a critical edge that starts at an
/// IndirectBrInst. Splitting these edges will almost always create an invalid
/// program because the address of the new block won't be the one that is jumped
/// to.
///
BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
Pass *P, bool MergeIdenticalEdges) {
if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0;
assert(!isa<IndirectBrInst>(TI) &&
"Cannot split critical edge from IndirectBrInst");
BasicBlock *TIBB = TI->getParent();
BasicBlock *DestBB = TI->getSuccessor(SuccNum);
// Create a new basic block, linking it into the CFG.
BasicBlock *NewBB = BasicBlock::Create(TI->getContext(),
TIBB->getName() + "." + DestBB->getName() + "_crit_edge");
// Create our unconditional branch.
BranchInst::Create(DestBB, NewBB);
// Branch to the new block, breaking the edge.
TI->setSuccessor(SuccNum, NewBB);
// Insert the block into the function... right after the block TI lives in.
Function &F = *TIBB->getParent();
Function::iterator FBBI = TIBB;
F.getBasicBlockList().insert(++FBBI, NewBB);
// If there are any PHI nodes in DestBB, we need to update them so that they
// merge incoming values from NewBB instead of from TIBB.
if (PHINode *APHI = dyn_cast<PHINode>(DestBB->begin())) {
// This conceptually does:
// foreach (PHINode *PN in DestBB)
// PN->setIncomingBlock(PN->getIncomingBlock(TIBB), NewBB);
// but is optimized for two cases.
if (APHI->getNumIncomingValues() <= 8) { // Small # preds case.
unsigned BBIdx = 0;
for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
// We no longer enter through TIBB, now we come in through NewBB.
// Revector exactly one entry in the PHI node that used to come from
// TIBB to come from NewBB.
PHINode *PN = cast<PHINode>(I);
// Reuse the previous value of BBIdx if it lines up. In cases where we
// have multiple phi nodes with *lots* of predecessors, this is a speed
// win because we don't have to scan the PHI looking for TIBB. This
// happens because the BB list of PHI nodes are usually in the same
// order.
if (PN->getIncomingBlock(BBIdx) != TIBB)
BBIdx = PN->getBasicBlockIndex(TIBB);
PN->setIncomingBlock(BBIdx, NewBB);
}
} else {
// However, the foreach loop is slow for blocks with lots of predecessors
// because PHINode::getIncomingBlock is O(n) in # preds. Instead, walk
// the user list of TIBB to find the PHI nodes.
SmallPtrSet<PHINode*, 16> UpdatedPHIs;
for (Value::use_iterator UI = TIBB->use_begin(), E = TIBB->use_end();
UI != E; ) {
Value::use_iterator Use = UI++;
if (PHINode *PN = dyn_cast<PHINode>(Use)) {
// Remove one entry from each PHI.
if (PN->getParent() == DestBB && UpdatedPHIs.insert(PN))
PN->setOperand(Use.getOperandNo(), NewBB);
}
}
}
}
// If there are any other edges from TIBB to DestBB, update those to go
// through the split block, making those edges non-critical as well (and
// reducing the number of phi entries in the DestBB if relevant).
if (MergeIdenticalEdges) {
for (unsigned i = SuccNum+1, e = TI->getNumSuccessors(); i != e; ++i) {
if (TI->getSuccessor(i) != DestBB) continue;
// Remove an entry for TIBB from DestBB phi nodes.
DestBB->removePredecessor(TIBB);
// We found another edge to DestBB, go to NewBB instead.
TI->setSuccessor(i, NewBB);
}
}
// If we don't have a pass object, we can't update anything...
if (P == 0) return NewBB;
DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>();
LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>();
ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>();
// If we have nothing to update, just return.
if (DT == 0 && DF == 0 && LI == 0 && PI == 0)
return NewBB;
// Now update analysis information. Since the only predecessor of NewBB is
// the TIBB, TIBB clearly dominates NewBB. TIBB usually doesn't dominate
// anything, as there are other successors of DestBB. However, if all other
// predecessors of DestBB are already dominated by DestBB (e.g. DestBB is a
// loop header) then NewBB dominates DestBB.
SmallVector<BasicBlock*, 8> OtherPreds;
// If there is a PHI in the block, loop over predecessors with it, which is
// faster than iterating pred_begin/end.
if (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingBlock(i) != NewBB)
OtherPreds.push_back(PN->getIncomingBlock(i));
} else {
for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB);
I != E; ++I)
if (*I != NewBB)
OtherPreds.push_back(*I);
}
bool NewBBDominatesDestBB = true;
// Should we update DominatorTree information?
if (DT) {
DomTreeNode *TINode = DT->getNode(TIBB);
// The new block is not the immediate dominator for any other nodes, but
// TINode is the immediate dominator for the new node.
//
if (TINode) { // Don't break unreachable code!
DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB);
DomTreeNode *DestBBNode = 0;
// If NewBBDominatesDestBB hasn't been computed yet, do so with DT.
if (!OtherPreds.empty()) {
DestBBNode = DT->getNode(DestBB);
while (!OtherPreds.empty() && NewBBDominatesDestBB) {
if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back()))
NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode);
OtherPreds.pop_back();
}
OtherPreds.clear();
}
// If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it
// doesn't dominate anything.
if (NewBBDominatesDestBB) {
if (!DestBBNode) DestBBNode = DT->getNode(DestBB);
DT->changeImmediateDominator(DestBBNode, NewBBNode);
}
}
}
// Should we update DominanceFrontier information?
if (DF) {
// If NewBBDominatesDestBB hasn't been computed yet, do so with DF.
if (!OtherPreds.empty()) {
// FIXME: IMPLEMENT THIS!
llvm_unreachable("Requiring domfrontiers but not idom/domtree/domset."
" not implemented yet!");
}
// Since the new block is dominated by its only predecessor TIBB,
// it cannot be in any block's dominance frontier. If NewBB dominates
// DestBB, its dominance frontier is the same as DestBB's, otherwise it is
// just {DestBB}.
DominanceFrontier::DomSetType NewDFSet;
if (NewBBDominatesDestBB) {
DominanceFrontier::iterator I = DF->find(DestBB);
if (I != DF->end()) {
DF->addBasicBlock(NewBB, I->second);
if (I->second.count(DestBB)) {
// However NewBB's frontier does not include DestBB.
DominanceFrontier::iterator NF = DF->find(NewBB);
DF->removeFromFrontier(NF, DestBB);
}
}
else
DF->addBasicBlock(NewBB, DominanceFrontier::DomSetType());
} else {
DominanceFrontier::DomSetType NewDFSet;
NewDFSet.insert(DestBB);
DF->addBasicBlock(NewBB, NewDFSet);
}
}
// Update LoopInfo if it is around.
if (LI) {
if (Loop *TIL = LI->getLoopFor(TIBB)) {
// If one or the other blocks were not in a loop, the new block is not
// either, and thus LI doesn't need to be updated.
if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
if (TIL == DestLoop) {
// Both in the same loop, the NewBB joins loop.
DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
} else if (TIL->contains(DestLoop)) {
// Edge from an outer loop to an inner loop. Add to the outer loop.
TIL->addBasicBlockToLoop(NewBB, LI->getBase());
} else if (DestLoop->contains(TIL)) {
// Edge from an inner loop to an outer loop. Add to the outer loop.
DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
} else {
// Edge from two loops with no containment relation. Because these
// are natural loops, we know that the destination block must be the
// header of its loop (adding a branch into a loop elsewhere would
// create an irreducible loop).
assert(DestLoop->getHeader() == DestBB &&
"Should not create irreducible loops!");
if (Loop *P = DestLoop->getParentLoop())
P->addBasicBlockToLoop(NewBB, LI->getBase());
}
}
// If TIBB is in a loop and DestBB is outside of that loop, split the
// other exit blocks of the loop that also have predecessors outside
// the loop, to maintain a LoopSimplify guarantee.
if (!TIL->contains(DestBB) &&
P->mustPreserveAnalysisID(LoopSimplifyID)) {
assert(!TIL->contains(NewBB) &&
"Split point for loop exit is contained in loop!");
// Update LCSSA form in the newly created exit block.
if (P->mustPreserveAnalysisID(LCSSAID)) {
SmallVector<BasicBlock *, 1> OrigPred;
OrigPred.push_back(TIBB);
CreatePHIsForSplitLoopExit(OrigPred, NewBB, DestBB);
}
// For each unique exit block...
SmallVector<BasicBlock *, 4> ExitBlocks;
TIL->getExitBlocks(ExitBlocks);
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
// Collect all the preds that are inside the loop, and note
// whether there are any preds outside the loop.
SmallVector<BasicBlock *, 4> Preds;
bool HasPredOutsideOfLoop = false;
BasicBlock *Exit = ExitBlocks[i];
for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit);
I != E; ++I)
if (TIL->contains(*I))
Preds.push_back(*I);
else
HasPredOutsideOfLoop = true;
// If there are any preds not in the loop, we'll need to split
// the edges. The Preds.empty() check is needed because a block
// may appear multiple times in the list. We can't use
// getUniqueExitBlocks above because that depends on LoopSimplify
// form, which we're in the process of restoring!
if (!Preds.empty() && HasPredOutsideOfLoop) {
BasicBlock *NewExitBB =
SplitBlockPredecessors(Exit, Preds.data(), Preds.size(),
"split", P);
if (P->mustPreserveAnalysisID(LCSSAID))
CreatePHIsForSplitLoopExit(Preds, NewExitBB, Exit);
}
}
}
// LCSSA form was updated above for the case where LoopSimplify is
// available, which means that all predecessors of loop exit blocks
// are within the loop. Without LoopSimplify form, it would be
// necessary to insert a new phi.
assert((!P->mustPreserveAnalysisID(LCSSAID) ||
P->mustPreserveAnalysisID(LoopSimplifyID)) &&
"SplitCriticalEdge doesn't know how to update LCCSA form "
"without LoopSimplify!");
}
}
// Update ProfileInfo if it is around.
if (PI)
PI->splitEdge(TIBB, DestBB, NewBB, MergeIdenticalEdges);
return NewBB;
}
// NewBB is split and now it has one successor. Update dominance frontier to
// reflect this change.
void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
assert(NewBB->getTerminator()->getNumSuccessors() == 1 &&
"NewBB should have a single successor!");
BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
// NewBBSucc inherits original NewBB frontier.
DominanceFrontier::iterator NewBBI = find(NewBB);
if (NewBBI != end())
addBasicBlock(NewBBSucc, NewBBI->second);
// If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
// DF(NewBBSucc) without the stuff that the new block does not dominate
// a predecessor of.
DominatorTree &DT = getAnalysis<DominatorTree>();
DomTreeNode *NewBBNode = DT.getNode(NewBB);
DomTreeNode *NewBBSuccNode = DT.getNode(NewBBSucc);
if (DT.dominates(NewBBNode, NewBBSuccNode)) {
DominanceFrontier::iterator DFI = find(NewBBSucc);
if (DFI != end()) {
DominanceFrontier::DomSetType Set = DFI->second;
// Filter out stuff in Set that we do not dominate a predecessor of.
for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
E = Set.end(); SetI != E;) {
bool DominatesPred = false;
for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
PI != E; ++PI)
if (DT.dominates(NewBBNode, DT.getNode(*PI))) {
DominatesPred = true;
break;
}
if (!DominatesPred)
Set.erase(SetI++);
else
++SetI;
}
if (NewBBI != end()) {
for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
E = Set.end(); SetI != E; ++SetI) {
BasicBlock *SB = *SetI;
addToFrontier(NewBBI, SB);
}
} else
addBasicBlock(NewBB, Set);
}
} else {
// DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
// NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
// NewBBSucc)). NewBBSucc is the single successor of NewBB.
DominanceFrontier::DomSetType NewDFSet;
NewDFSet.insert(NewBBSucc);
addBasicBlock(NewBB, NewDFSet);
}
// Now update dominance frontiers which either used to contain NewBBSucc
// or which now need to include NewBB.
// Collect the set of blocks which dominate a predecessor of NewBB or
// NewSuccBB and which don't dominate both. This is an initial
// approximation of the blocks whose dominance frontiers will need updates.
SmallVector<DomTreeNode *, 16> AllPredDoms;
// Compute the block which dominates both NewBBSucc and NewBB. This is
// the immediate dominator of NewBBSucc unless NewBB dominates NewBBSucc.
// The code below which climbs dominator trees will stop at this point,
// because from this point up, dominance frontiers are unaffected.
DomTreeNode *DominatesBoth = 0;
if (NewBBSuccNode) {
DominatesBoth = NewBBSuccNode->getIDom();
if (DominatesBoth == NewBBNode)
DominatesBoth = NewBBNode->getIDom();
}
// Collect the set of all blocks which dominate a predecessor of NewBB.
SmallPtrSet<DomTreeNode *, 8> NewBBPredDoms;
for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); PI != E; ++PI)
for (DomTreeNode *DTN = DT.getNode(*PI); DTN; DTN = DTN->getIDom()) {
if (DTN == DominatesBoth)
break;
if (!NewBBPredDoms.insert(DTN))
break;
AllPredDoms.push_back(DTN);
}
// Collect the set of all blocks which dominate a predecessor of NewSuccBB.
SmallPtrSet<DomTreeNode *, 8> NewBBSuccPredDoms;
for (pred_iterator PI = pred_begin(NewBBSucc),
E = pred_end(NewBBSucc); PI != E; ++PI)
for (DomTreeNode *DTN = DT.getNode(*PI); DTN; DTN = DTN->getIDom()) {
if (DTN == DominatesBoth)
break;
if (!NewBBSuccPredDoms.insert(DTN))
break;
if (!NewBBPredDoms.count(DTN))
AllPredDoms.push_back(DTN);
}
// Visit all relevant dominance frontiers and make any needed updates.
for (SmallVectorImpl<DomTreeNode *>::const_iterator I = AllPredDoms.begin(),
E = AllPredDoms.end(); I != E; ++I) {
DomTreeNode *DTN = *I;
iterator DFI = find((*I)->getBlock());
// Only consider nodes that have NewBBSucc in their dominator frontier.
if (DFI == end() || !DFI->second.count(NewBBSucc)) continue;
// If the block dominates a predecessor of NewBB but does not properly
// dominate NewBB itself, add NewBB to its dominance frontier.
if (NewBBPredDoms.count(DTN) &&
!DT.properlyDominates(DTN, NewBBNode))
addToFrontier(DFI, NewBB);
// If the block does not dominate a predecessor of NewBBSucc or
// properly dominates NewBBSucc itself, remove NewBBSucc from its
// dominance frontier.
if (!NewBBSuccPredDoms.count(DTN) ||
DT.properlyDominates(DTN, NewBBSuccNode))
removeFromFrontier(DFI, NewBBSucc);
}
}