/// SplitBlock - Split the specified block at the specified instruction - every
/// thing before SplitPt stays in Old and everything starting with SplitPt moves
/// to a new block. The two blocks are joined by an unconditional branch and
/// the loop info is updated.
///
BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
BasicBlock::iterator SplitIt = SplitPt;
while (isa<PHINode>(SplitIt))
++SplitIt;
BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
// The new block lives in whichever loop the old one did. This preserves
// LCSSA as well, because we force the split point to be after any PHI nodes.
if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>())
if (Loop *L = LI->getLoopFor(Old))
L->addBasicBlockToLoop(New, LI->getBase());
if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>())
{
// Old dominates New. New node domiantes all other nodes dominated by Old.
DomTreeNode *OldNode = DT->getNode(Old);
std::vector<DomTreeNode *> Children;
for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
I != E; ++I)
Children.push_back(*I);
DomTreeNode *NewNode = DT->addNewBlock(New,Old);
for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
E = Children.end(); I != E; ++I)
DT->changeImmediateDominator(*I, NewNode);
}
if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>())
DF->splitBlock(Old);
return New;
}
/*update the dominator tree when a new block is created*/
void updateDT(BasicBlock *oldB, BasicBlock *newB, DominatorTree *DT) {
errs() << "\n -----------------------" << oldB->getName()
<< "\n dominated by \n"
<< newB->getName() << "\n";
DomTreeNode *OldNode = DT->getNode(oldB);
if (OldNode) {
std::vector<DomTreeNode *> Children;
for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end(); I != E;
++I)
Children.push_back(*I);
DomTreeNode *inDT = DT->getNode(newB);
DomTreeNode *NewNode;
if (inDT == 0)
NewNode = DT->addNewBlock(newB, oldB);
else
NewNode = DT->getNode(newB);
for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
E = Children.end();
I != E; ++I)
DT->changeImmediateDominator(*I, NewNode);
}
}
/// SinkInstruction - Determine whether it is safe to sink the specified machine
/// instruction out of its current block into a successor.
bool Sinking::SinkInstruction(Instruction *Inst,
SmallPtrSetImpl<Instruction *> &Stores) {
// Don't sink static alloca instructions. CodeGen assumes allocas outside the
// entry block are dynamically sized stack objects.
if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
if (AI->isStaticAlloca())
return false;
// Check if it's safe to move the instruction.
if (!isSafeToMove(Inst, AA, Stores))
return false;
// FIXME: This should include support for sinking instructions within the
// block they are currently in to shorten the live ranges. We often get
// instructions sunk into the top of a large block, but it would be better to
// also sink them down before their first use in the block. This xform has to
// be careful not to *increase* register pressure though, e.g. sinking
// "x = y + z" down if it kills y and z would increase the live ranges of y
// and z and only shrink the live range of x.
// SuccToSinkTo - This is the successor to sink this instruction to, once we
// decide.
BasicBlock *SuccToSinkTo = nullptr;
// Instructions can only be sunk if all their uses are in blocks
// dominated by one of the successors.
// Look at all the postdominators and see if we can sink it in one.
DomTreeNode *DTN = DT->getNode(Inst->getParent());
for (DomTreeNode::iterator I = DTN->begin(), E = DTN->end();
I != E && SuccToSinkTo == nullptr; ++I) {
BasicBlock *Candidate = (*I)->getBlock();
if ((*I)->getIDom()->getBlock() == Inst->getParent() &&
IsAcceptableTarget(Inst, Candidate))
SuccToSinkTo = Candidate;
}
// If no suitable postdominator was found, look at all the successors and
// decide which one we should sink to, if any.
for (succ_iterator I = succ_begin(Inst->getParent()),
E = succ_end(Inst->getParent()); I != E && !SuccToSinkTo; ++I) {
if (IsAcceptableTarget(Inst, *I))
SuccToSinkTo = *I;
}
// If we couldn't find a block to sink to, ignore this instruction.
if (!SuccToSinkTo)
return false;
DEBUG(dbgs() << "Sink" << *Inst << " (";
Inst->getParent()->printAsOperand(dbgs(), false);
dbgs() << " -> ";
SuccToSinkTo->printAsOperand(dbgs(), false);
dbgs() << ")\n");
// Move the instruction.
Inst->moveBefore(SuccToSinkTo->getFirstInsertionPt());
return true;
}
/// Compute the dominator tree levels for DT.
static void computeDomTreeLevels(DominanceInfo *DT,
DomTreeLevelMap &DomTreeLevels) {
// TODO: This should happen once per function.
SmallVector<DomTreeNode *, 32> Worklist;
DomTreeNode *Root = DT->getRootNode();
DomTreeLevels[Root] = 0;
Worklist.push_back(Root);
while (!Worklist.empty()) {
DomTreeNode *Node = Worklist.pop_back_val();
unsigned ChildLevel = DomTreeLevels[Node] + 1;
for (auto CI = Node->begin(), CE = Node->end(); CI != CE; ++CI) {
DomTreeLevels[*CI] = ChildLevel;
Worklist.push_back(*CI);
}
}
}
void CodeExtractor::splitReturnBlocks() {
for (BasicBlock *Block : Blocks)
if (ReturnInst *RI = dyn_cast<ReturnInst>(Block->getTerminator())) {
BasicBlock *New =
Block->splitBasicBlock(RI->getIterator(), Block->getName() + ".ret");
if (DT) {
// Old dominates New. New node dominates all other nodes dominated
// by Old.
DomTreeNode *OldNode = DT->getNode(Block);
SmallVector<DomTreeNode *, 8> Children(OldNode->begin(),
OldNode->end());
DomTreeNode *NewNode = DT->addNewBlock(New, Block);
for (DomTreeNode *I : Children)
DT->changeImmediateDominator(I, NewNode);
}
}
}
void RegionExtractor::splitReturnBlocks() {
for (SetVector<BasicBlock *>::iterator I = Blocks.begin(), E = Blocks.end();
I != E; ++I)
if (ReturnInst *RI = dyn_cast<ReturnInst>((*I)->getTerminator())) {
BasicBlock *New = (*I)->splitBasicBlock(RI, (*I)->getName()+".ret");
if (DT) {
// Old dominates New. New node dominates all other nodes dominated
// by Old.
DomTreeNode *OldNode = DT->getNode(*I);
SmallVector<DomTreeNode*, 8> Children;
for (DomTreeNode::iterator DI = OldNode->begin(), DE = OldNode->end();
DI != DE; ++DI)
Children.push_back(*DI);
DomTreeNode *NewNode = DT->addNewBlock(New, *I);
#if LLVM_VERSION_MINOR == 5
for (SmallVectorImpl<DomTreeNode *>::iterator I = Children.begin(),
#else
for (SmallVector<DomTreeNode *, 8>::iterator I = Children.begin(),
#endif
E = Children.end(); I != E; ++I)
DT->changeImmediateDominator(*I, NewNode);
}
}
void StackAllocationPromoter::promoteAllocationToPhi() {
DEBUG(llvm::dbgs() << "*** Placing Phis for : " << *ASI);
// A list of blocks that will require new Phi values.
BlockSet PhiBlocks;
// The "piggy-bank" data-structure that we use for processing the dom-tree
// bottom-up.
NodePriorityQueue PQ;
// Collect all of the stores into the AllocStack. We know that at this point
// we have at most one store per block.
for (auto UI = ASI->use_begin(), E = ASI->use_end(); UI != E; ++UI) {
SILInstruction *II = UI->getUser();
// We need to place Phis for this block.
if (isa<StoreInst>(II)) {
// If the block is in the dom tree (dominated by the entry block).
if (DomTreeNode *Node = DT->getNode(II->getParent()))
PQ.push(std::make_pair(Node, DomTreeLevels[Node]));
}
}
DEBUG(llvm::dbgs() << "*** Found: " << PQ.size() << " Defs\n");
// A list of nodes for which we already calculated the dominator frontier.
llvm::SmallPtrSet<DomTreeNode *, 32> Visited;
SmallVector<DomTreeNode *, 32> Worklist;
// Scan all of the definitions in the function bottom-up using the priority
// queue.
while (!PQ.empty()) {
DomTreeNodePair RootPair = PQ.top();
PQ.pop();
DomTreeNode *Root = RootPair.first;
unsigned RootLevel = RootPair.second;
// Walk all dom tree children of Root, inspecting their successors. Only
// J-edges, whose target level is at most Root's level are added to the
// dominance frontier.
Worklist.clear();
Worklist.push_back(Root);
while (!Worklist.empty()) {
DomTreeNode *Node = Worklist.pop_back_val();
SILBasicBlock *BB = Node->getBlock();
// For all successors of the node:
for (auto &Succ : BB->getSuccessors()) {
DomTreeNode *SuccNode = DT->getNode(Succ);
// Skip D-edges (edges that are dom-tree edges).
if (SuccNode->getIDom() == Node)
continue;
// Ignore J-edges that point to nodes that are not smaller or equal
// to the root level.
unsigned SuccLevel = DomTreeLevels[SuccNode];
if (SuccLevel > RootLevel)
continue;
// Ignore visited nodes.
if (!Visited.insert(SuccNode).second)
continue;
// If the new PHInode is not dominated by the allocation then it's dead.
if (!DT->dominates(ASI->getParent(), SuccNode->getBlock()))
continue;
// If the new PHInode is properly dominated by the deallocation then it
// is obviously a dead PHInode, so we don't need to insert it.
if (DSI && DT->properlyDominates(DSI->getParent(),
SuccNode->getBlock()))
continue;
// The successor node is a new PHINode. If this is a new PHI node
// then it may require additional definitions, so add it to the PQ.
if (PhiBlocks.insert(Succ).second)
PQ.push(std::make_pair(SuccNode, SuccLevel));
}
// Add the children in the dom-tree to the worklist.
for (auto CI = Node->begin(), CE = Node->end(); CI != CE; ++CI)
if (!Visited.count(*CI))
Worklist.push_back(*CI);
}
}
DEBUG(llvm::dbgs() << "*** Found: " << PhiBlocks.size() << " new PHIs\n");
NumPhiPlaced += PhiBlocks.size();
// At this point we calculated the locations of all of the new Phi values.
// Next, add the Phi values and promote all of the loads and stores into the
// new locations.
// Replace the dummy values with new block arguments.
addBlockArguments(PhiBlocks);
// Hook up the Phi nodes, loads, and debug_value_addr with incoming values.
fixBranchesAndUses(PhiBlocks);
DEBUG(llvm::dbgs() << "*** Finished placing Phis ***\n");
}
/// At this point, we're committed to promoting the alloca using IDF's, and the
/// standard SSA construction algorithm. Determine which blocks need phi nodes
/// and see if we can optimize out some work by avoiding insertion of dead phi
/// nodes.
void PromoteMem2Reg::DetermineInsertionPoint(AllocaInst *AI, unsigned AllocaNum,
AllocaInfo &Info) {
// Unique the set of defining blocks for efficient lookup.
SmallPtrSet<BasicBlock *, 32> DefBlocks;
DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end());
// Determine which blocks the value is live in. These are blocks which lead
// to uses.
SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks);
// Use a priority queue keyed on dominator tree level so that inserted nodes
// are handled from the bottom of the dominator tree upwards.
typedef std::priority_queue<DomTreeNodePair,
SmallVector<DomTreeNodePair, 32>,
DomTreeNodeCompare> IDFPriorityQueue;
IDFPriorityQueue PQ;
for (SmallPtrSet<BasicBlock *, 32>::const_iterator I = DefBlocks.begin(),
E = DefBlocks.end();
I != E; ++I) {
if (DomTreeNode *Node = DT.getNode(*I))
PQ.push(std::make_pair(Node, DomLevels[Node]));
}
SmallVector<std::pair<unsigned, BasicBlock *>, 32> DFBlocks;
SmallPtrSet<DomTreeNode *, 32> Visited;
SmallVector<DomTreeNode *, 32> Worklist;
while (!PQ.empty()) {
DomTreeNodePair RootPair = PQ.top();
PQ.pop();
DomTreeNode *Root = RootPair.first;
unsigned RootLevel = RootPair.second;
// Walk all dominator tree children of Root, inspecting their CFG edges with
// targets elsewhere on the dominator tree. Only targets whose level is at
// most Root's level are added to the iterated dominance frontier of the
// definition set.
Worklist.clear();
Worklist.push_back(Root);
while (!Worklist.empty()) {
DomTreeNode *Node = Worklist.pop_back_val();
BasicBlock *BB = Node->getBlock();
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
++SI) {
DomTreeNode *SuccNode = DT.getNode(*SI);
// Quickly skip all CFG edges that are also dominator tree edges instead
// of catching them below.
if (SuccNode->getIDom() == Node)
continue;
unsigned SuccLevel = DomLevels[SuccNode];
if (SuccLevel > RootLevel)
continue;
if (!Visited.insert(SuccNode))
continue;
BasicBlock *SuccBB = SuccNode->getBlock();
if (!LiveInBlocks.count(SuccBB))
continue;
DFBlocks.push_back(std::make_pair(BBNumbers[SuccBB], SuccBB));
if (!DefBlocks.count(SuccBB))
PQ.push(std::make_pair(SuccNode, SuccLevel));
}
for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end(); CI != CE;
++CI) {
if (!Visited.count(*CI))
Worklist.push_back(*CI);
}
}
}
if (DFBlocks.size() > 1)
std::sort(DFBlocks.begin(), DFBlocks.end());
unsigned CurrentVersion = 0;
for (unsigned i = 0, e = DFBlocks.size(); i != e; ++i)
QueuePhiNode(DFBlocks[i].second, AllocaNum, CurrentVersion);
}
void PromoteMem2Reg::run() {
Function &F = *DT.getRoot()->getParent();
if (AST)
PointerAllocaValues.resize(Allocas.size());
AllocaDbgDeclares.resize(Allocas.size());
AllocaInfo Info;
LargeBlockInfo LBI;
for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
AllocaInst *AI = Allocas[AllocaNum];
//assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!");
assert(AI->getParent()->getParent() == &F &&
"All allocas should be in the same function, which is same as DF!");
removeLifetimeIntrinsicUsers(AI);
if (AI->use_empty()) {
// If there are no uses of the alloca, just delete it now.
if (AST)
AST->deleteValue(AI);
AI->eraseFromParent();
// Remove the alloca from the Allocas list, since it has been processed
RemoveFromAllocasList(AllocaNum);
++NumDeadAlloca;
continue;
}
// Calculate the set of read and write-locations for each alloca. This is
// analogous to finding the 'uses' and 'definitions' of each variable.
bool Good = Info.analyzeAlloca(*AI);
(void)Good;
assert(Good && "Cannot promote non-promotable alloca!");
// If there is only a single store to this value, replace any loads of
// it that are directly dominated by the definition with the value stored.
if (Info.DefiningBlocks.size() == 1) {
if (rewriteSingleStoreAlloca(AI, Info, LBI, DT, AST)) {
// The alloca has been processed, move on.
RemoveFromAllocasList(AllocaNum);
++NumSingleStore;
continue;
}
}
// If the alloca is only read and written in one basic block, just perform a
// linear sweep over the block to eliminate it.
if (Info.OnlyUsedInOneBlock) {
promoteSingleBlockAlloca(AI, Info, LBI, AST);
// The alloca has been processed, move on.
RemoveFromAllocasList(AllocaNum);
continue;
}
// If we haven't computed dominator tree levels, do so now.
if (DomLevels.empty()) {
SmallVector<DomTreeNode *, 32> Worklist;
DomTreeNode *Root = DT.getRootNode();
DomLevels[Root] = 0;
Worklist.push_back(Root);
while (!Worklist.empty()) {
DomTreeNode *Node = Worklist.pop_back_val();
unsigned ChildLevel = DomLevels[Node] + 1;
for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end();
CI != CE; ++CI) {
DomLevels[*CI] = ChildLevel;
Worklist.push_back(*CI);
}
}
}
// If we haven't computed a numbering for the BB's in the function, do so
// now.
if (BBNumbers.empty()) {
unsigned ID = 0;
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
BBNumbers[I] = ID++;
}
// If we have an AST to keep updated, remember some pointer value that is
// stored into the alloca.
if (AST)
PointerAllocaValues[AllocaNum] = Info.AllocaPointerVal;
// Remember the dbg.declare intrinsic describing this alloca, if any.
if (Info.DbgDeclare)
AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare;
// Keep the reverse mapping of the 'Allocas' array for the rename pass.
AllocaLookup[Allocas[AllocaNum]] = AllocaNum;
// At this point, we're committed to promoting the alloca using IDF's, and
// the standard SSA construction algorithm. Determine which blocks need PHI
// nodes and see if we can optimize out some work by avoiding insertion of
// dead phi nodes.
DetermineInsertionPoint(AI, AllocaNum, Info);
}
if (Allocas.empty())
return; // All of the allocas must have been trivial!
LBI.clear();
// Set the incoming values for the basic block to be null values for all of
// the alloca's. We do this in case there is a load of a value that has not
// been stored yet. In this case, it will get this null value.
//
RenamePassData::ValVector Values(Allocas.size());
for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
Values[i] = UndefValue::get(Allocas[i]->getAllocatedType());
// Walks all basic blocks in the function performing the SSA rename algorithm
// and inserting the phi nodes we marked as necessary
//
std::vector<RenamePassData> RenamePassWorkList;
RenamePassWorkList.push_back(RenamePassData(F.begin(), 0, Values));
do {
RenamePassData RPD;
RPD.swap(RenamePassWorkList.back());
RenamePassWorkList.pop_back();
// RenamePass may add new worklist entries.
RenamePass(RPD.BB, RPD.Pred, RPD.Values, RenamePassWorkList);
} while (!RenamePassWorkList.empty());
// The renamer uses the Visited set to avoid infinite loops. Clear it now.
Visited.clear();
// Remove the allocas themselves from the function.
for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
Instruction *A = Allocas[i];
// If there are any uses of the alloca instructions left, they must be in
// unreachable basic blocks that were not processed by walking the dominator
// tree. Just delete the users now.
if (!A->use_empty())
A->replaceAllUsesWith(UndefValue::get(A->getType()));
if (AST)
AST->deleteValue(A);
A->eraseFromParent();
}
// Remove alloca's dbg.declare instrinsics from the function.
for (unsigned i = 0, e = AllocaDbgDeclares.size(); i != e; ++i)
if (DbgDeclareInst *DDI = AllocaDbgDeclares[i])
DDI->eraseFromParent();
// Loop over all of the PHI nodes and see if there are any that we can get
// rid of because they merge all of the same incoming values. This can
// happen due to undef values coming into the PHI nodes. This process is
// iterative, because eliminating one PHI node can cause others to be removed.
bool EliminatedAPHI = true;
while (EliminatedAPHI) {
EliminatedAPHI = false;
// Iterating over NewPhiNodes is deterministic, so it is safe to try to
// simplify and RAUW them as we go. If it was not, we could add uses to
// the values we replace with in a non deterministic order, thus creating
// non deterministic def->use chains.
for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator
I = NewPhiNodes.begin(),
E = NewPhiNodes.end();
I != E;) {
PHINode *PN = I->second;
// If this PHI node merges one value and/or undefs, get the value.
if (Value *V = SimplifyInstruction(PN, 0, 0, &DT)) {
if (AST && PN->getType()->isPointerTy())
AST->deleteValue(PN);
PN->replaceAllUsesWith(V);
PN->eraseFromParent();
NewPhiNodes.erase(I++);
EliminatedAPHI = true;
continue;
}
++I;
}
}
// At this point, the renamer has added entries to PHI nodes for all reachable
// code. Unfortunately, there may be unreachable blocks which the renamer
// hasn't traversed. If this is the case, the PHI nodes may not
// have incoming values for all predecessors. Loop over all PHI nodes we have
// created, inserting undef values if they are missing any incoming values.
//
for (DenseMap<std::pair<unsigned, unsigned>, PHINode *>::iterator
I = NewPhiNodes.begin(),
E = NewPhiNodes.end();
I != E; ++I) {
// We want to do this once per basic block. As such, only process a block
// when we find the PHI that is the first entry in the block.
PHINode *SomePHI = I->second;
BasicBlock *BB = SomePHI->getParent();
if (&BB->front() != SomePHI)
continue;
// Only do work here if there the PHI nodes are missing incoming values. We
// know that all PHI nodes that were inserted in a block will have the same
// number of incoming values, so we can just check any of them.
if (SomePHI->getNumIncomingValues() == getNumPreds(BB))
continue;
// Get the preds for BB.
SmallVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB));
// Ok, now we know that all of the PHI nodes are missing entries for some
// basic blocks. Start by sorting the incoming predecessors for efficient
// access.
std::sort(Preds.begin(), Preds.end());
// Now we loop through all BB's which have entries in SomePHI and remove
// them from the Preds list.
for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i) {
// Do a log(n) search of the Preds list for the entry we want.
SmallVectorImpl<BasicBlock *>::iterator EntIt = std::lower_bound(
Preds.begin(), Preds.end(), SomePHI->getIncomingBlock(i));
assert(EntIt != Preds.end() && *EntIt == SomePHI->getIncomingBlock(i) &&
"PHI node has entry for a block which is not a predecessor!");
// Remove the entry
Preds.erase(EntIt);
}
// At this point, the blocks left in the preds list must have dummy
// entries inserted into every PHI nodes for the block. Update all the phi
// nodes in this block that we are inserting (there could be phis before
// mem2reg runs).
unsigned NumBadPreds = SomePHI->getNumIncomingValues();
BasicBlock::iterator BBI = BB->begin();
while ((SomePHI = dyn_cast<PHINode>(BBI++)) &&
SomePHI->getNumIncomingValues() == NumBadPreds) {
Value *UndefVal = UndefValue::get(SomePHI->getType());
for (unsigned pred = 0, e = Preds.size(); pred != e; ++pred)
SomePHI->addIncoming(UndefVal, Preds[pred]);
}
}
NewPhiNodes.clear();
}
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
// Can't merge the entry block. Don't merge away blocks who have their
// address taken: this is a bug if the predecessor block is the entry node
// (because we'd end up taking the address of the entry) and undesirable in
// any case.
if (pred_begin(BB) == pred_end(BB) ||
BB->hasAddressTaken()) return false;
BasicBlock *PredBB = *PI++;
for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
if (*PI != PredBB) {
PredBB = 0; // There are multiple different predecessors...
break;
}
// Can't merge if there are multiple predecessors.
if (!PredBB) return false;
// Don't break self-loops.
if (PredBB == BB) return false;
// Don't break invokes.
if (isa<InvokeInst>(PredBB->getTerminator())) return false;
succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
BasicBlock* OnlySucc = BB;
for (; SI != SE; ++SI)
if (*SI != OnlySucc) {
OnlySucc = 0; // There are multiple distinct successors!
break;
}
// Can't merge if there are multiple successors.
if (!OnlySucc) return false;
// Can't merge if there is PHI loop.
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
if (PHINode *PN = dyn_cast<PHINode>(BI)) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == PN)
return false;
} else
break;
}
// Begin by getting rid of unneeded PHIs.
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
PN->replaceAllUsesWith(PN->getIncomingValue(0));
BB->getInstList().pop_front(); // Delete the phi node...
}
// Delete the unconditional branch from the predecessor...
PredBB->getInstList().pop_back();
// Move all definitions in the successor to the predecessor...
PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
// Make all PHI nodes that referred to BB now refer to Pred as their
// source...
BB->replaceAllUsesWith(PredBB);
// Inherit predecessors name if it exists.
if (!PredBB->hasName())
PredBB->takeName(BB);
// Finally, erase the old block and update dominator info.
if (P) {
if (DominatorTree* DT = P->getAnalysisIfAvailable<DominatorTree>()) {
DomTreeNode* DTN = DT->getNode(BB);
DomTreeNode* PredDTN = DT->getNode(PredBB);
if (DTN) {
SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(),
DE = Children.end(); DI != DE; ++DI)
DT->changeImmediateDominator(*DI, PredDTN);
DT->eraseNode(BB);
}
}
}
BB->eraseFromParent();
return true;
}
void DSWP::buildPDG(Loop *L) {
//Initialize PDG
for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
BasicBlock *BB = *bi;
for (BasicBlock::iterator ui = BB->begin(); ui != BB->end(); ui++) {
Instruction *inst = &(*ui);
//standardlize the name for all expr
if (util.hasNewDef(inst)) {
inst->setName(util.genId());
dname[inst] = inst->getNameStr();
} else {
dname[inst] = util.genId();
}
pdg[inst] = new vector<Edge>();
rev[inst] = new vector<Edge>();
}
}
//LoopInfo &li = getAnalysis<LoopInfo>();
/*
* Memory dependency analysis
*/
MemoryDependenceAnalysis &mda = getAnalysis<MemoryDependenceAnalysis>();
for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
BasicBlock *BB = *bi;
for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
Instruction *inst = &(*ii);
//data dependence = register dependence + memory dependence
//begin register dependence
for (Value::use_iterator ui = ii->use_begin(); ui != ii->use_end(); ui++) {
if (Instruction *user = dyn_cast<Instruction>(*ui)) {
addEdge(inst, user, REG);
}
}
//finish register dependence
//begin memory dependence
MemDepResult mdr = mda.getDependency(inst);
//TODO not sure clobbers mean!!
if (mdr.isDef()) {
Instruction *dep = mdr.getInst();
if (isa<LoadInst>(inst)) {
if (isa<StoreInst>(dep)) {
addEdge(dep, inst, DTRUE); //READ AFTER WRITE
}
}
if (isa<StoreInst>(inst)) {
if (isa<LoadInst>(dep)) {
addEdge(dep, inst, DANTI); //WRITE AFTER READ
}
if (isa<StoreInst>(dep)) {
addEdge(dep, inst, DOUT); //WRITE AFTER WRITE
}
}
//READ AFTER READ IS INSERT AFTER PDG BUILD
}
//end memory dependence
}//for ii
}//for bi
/*
* begin control dependence
*/
PostDominatorTree &pdt = getAnalysis<PostDominatorTree>();
//cout << pdt.getRootNode()->getBlock()->getNameStr() << endl;
/*
* alien code part 1
*/
LoopInfo *LI = &getAnalysis<LoopInfo>();
std::set<BranchInst*> backedgeParents;
for (Loop::block_iterator bi = L->getBlocks().begin(); bi
!= L->getBlocks().end(); bi++) {
BasicBlock *BB = *bi;
for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
Instruction *inst = ii;
if (BranchInst *brInst = dyn_cast<BranchInst>(inst)) {
// get the loop this instruction (and therefore basic block) belongs to
Loop *instLoop = LI->getLoopFor(BB);
bool branchesToHeader = false;
for (int i = brInst->getNumSuccessors() - 1; i >= 0
&& !branchesToHeader; i--) {
// if the branch could exit, store it
if (LI->getLoopFor(brInst->getSuccessor(i)) != instLoop) {
branchesToHeader = true;
}
}
if (branchesToHeader) {
backedgeParents.insert(brInst);
}
}
}
}
//build information for predecessor of blocks in post dominator tree
for (Function::iterator bi = func->begin(); bi != func->end(); bi++) {
BasicBlock *BB = bi;
DomTreeNode *dn = pdt.getNode(BB);
for (DomTreeNode::iterator di = dn->begin(); di != dn->end(); di++) {
BasicBlock *CB = (*di)->getBlock();
pre[CB] = BB;
}
}
//
// //add dependency within a basicblock
// for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
// BasicBlock *BB = *bi;
// Instruction *pre = NULL;
// for (BasicBlock::iterator ui = BB->begin(); ui != BB->end(); ui++) {
// Instruction *inst = &(*ui);
// if (pre != NULL) {
// addEdge(pre, inst, CONTROL);
// }
// pre = inst;
// }
// }
// //the special kind of dependence need loop peeling ? I don't know whether this is needed
// for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
// BasicBlock *BB = *bi;
// for (succ_iterator PI = succ_begin(BB); PI != succ_end(BB); ++PI) {
// BasicBlock *succ = *PI;
//
// checkControlDependence(BB, succ, pdt);
// }
// }
/*
* alien code part 2
*/
// add normal control dependencies
// loop through each instruction
for (Loop::block_iterator bbIter = L->block_begin(); bbIter
!= L->block_end(); ++bbIter) {
BasicBlock *bb = *bbIter;
// check the successors of this basic block
if (BranchInst *branchInst = dyn_cast<BranchInst>(bb->getTerminator())) {
if (branchInst->getNumSuccessors() > 1) {
BasicBlock * succ = branchInst->getSuccessor(0);
// if the successor is nested shallower than the current basic block, continue
if (LI->getLoopDepth(bb) < LI->getLoopDepth(succ)) {
continue;
}
// otherwise, add all instructions to graph as control dependence
while (succ != NULL && succ != bb && LI->getLoopDepth(succ)
>= LI->getLoopDepth(bb)) {
Instruction *terminator = bb->getTerminator();
for (BasicBlock::iterator succInstIter = succ->begin(); &(*succInstIter)
!= succ->getTerminator(); ++succInstIter) {
addEdge(terminator, &(*succInstIter), CONTROL);
}
if (BranchInst *succBrInst = dyn_cast<BranchInst>(succ->getTerminator())) {
if (succBrInst->getNumSuccessors() > 1) {
addEdge(terminator, succ->getTerminator(),
CONTROL);
}
}
if (BranchInst *br = dyn_cast<BranchInst>(succ->getTerminator())) {
if (br->getNumSuccessors() == 1) {
succ = br->getSuccessor(0);
} else {
succ = NULL;
}
} else {
succ = NULL;
}
}
}
}
}
/*
* alien code part 3
*/
for (std::set<BranchInst*>::iterator exitIter = backedgeParents.begin(); exitIter != backedgeParents.end(); ++exitIter) {
BranchInst *exitBranch = *exitIter;
if (exitBranch->isConditional()) {
BasicBlock *header = LI->getLoopFor(exitBranch->getParent())->getHeader();
for (BasicBlock::iterator ctrlIter = header->begin(); ctrlIter != header->end(); ++ctrlIter) {
addEdge(exitBranch, &(*ctrlIter), CONTROL);
}
}
}
//end control dependence
}
/// Renames all variables in the specified BasicBlock.
/// Only variables that need to be rename will be.
///
void SSI::rename(BasicBlock *BB) {
SmallPtrSet<Instruction*, 8> defined;
// Iterate through instructions and make appropriate renaming.
// For SSI_PHI (b = PHI()), store b at value_stack as a new
// definition of the variable it represents.
// For SSI_SIG (b = PHI(a)), substitute a with the current
// value of a, present in the value_stack.
// Then store bin the value_stack as the new definition of a.
// For all other instructions (b = OP(a, c, d, ...)), we need to substitute
// all operands with its current value, present in value_stack.
for (BasicBlock::iterator begin = BB->begin(), end = BB->end();
begin != end; ++begin) {
Instruction *I = begin;
if (PHINode *PN = dyn_cast<PHINode>(I)) { // Treat PHI functions
Instruction* position;
// Treat SSI_PHI
if ((position = getPositionPhi(PN))) {
value_stack[position].push_back(PN);
defined.insert(position);
// Treat SSI_SIG
} else if ((position = getPositionSigma(PN))) {
substituteUse(I);
value_stack[position].push_back(PN);
defined.insert(position);
}
// Treat all other PHI functions
else {
substituteUse(I);
}
}
// Treat all other functions
else {
substituteUse(I);
}
}
// This loop iterates in all BasicBlocks that are successors of the current
// BasicBlock. For each SSI_PHI instruction found, insert an operand.
// This operand is the current operand in value_stack for the variable
// in "position". And the BasicBlock this operand represents is the current
// BasicBlock.
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) {
BasicBlock *BB_succ = *SI;
for (BasicBlock::iterator begin = BB_succ->begin(),
notPhi = BB_succ->getFirstNonPHI(); begin != *notPhi; ++begin) {
Instruction *I = begin;
PHINode *PN = dyn_cast<PHINode>(I);
Instruction* position;
if (PN && ((position = getPositionPhi(PN)))) {
PN->addIncoming(value_stack[position].back(), BB);
}
}
}
// This loop calls rename on all children from this block. This time children
// refers to a successor block in the dominance tree.
DomTreeNode *DTN = DT_->getNode(BB);
for (DomTreeNode::iterator begin = DTN->begin(), end = DTN->end();
begin != end; ++begin) {
DomTreeNodeBase<BasicBlock> *DTN_children = *begin;
BasicBlock *BB_children = DTN_children->getBlock();
rename(BB_children);
}
// Now we remove all inserted definitions of a variable from the top of
// the stack leaving the previous one as the top.
for (SmallPtrSet<Instruction*, 8>::iterator DI = defined.begin(),
DE = defined.end(); DI != DE; ++DI)
value_stack[*DI].pop_back();
}
