namespace {
struct BreakCriticalEdges : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
- BreakCriticalEdges() : FunctionPass(&ID) {}
+ BreakCriticalEdges() : FunctionPass(ID) {}
virtual bool runOnFunction(Function &F);
X("break-crit-edges", "Break critical edges in CFG");
// Publically exposed interface to pass...
-const PassInfo *const llvm::BreakCriticalEdgesID = &X;
+char &llvm::BreakCriticalEdgesID = BreakCriticalEdges::ID;
FunctionPass *llvm::createBreakCriticalEdgesPass() {
return new BreakCriticalEdges();
}
if (TI->getNumSuccessors() == 1) return false;
const BasicBlock *Dest = TI->getSuccessor(SuccNum);
- pred_const_iterator I = pred_begin(Dest), E = pred_end(Dest);
+ const_pred_iterator I = pred_begin(Dest), E = pred_end(Dest);
// If there is more than one predecessor, this is a critical edge...
assert(I != E && "No preds, but we have an edge to the block?");
// If AllowIdenticalEdges is true, then we allow this edge to be considered
// non-critical iff all preds come from TI's block.
while (I != E) {
- if (*I != FirstPred)
+ const BasicBlock *P = *I;
+ if (P != FirstPred)
return true;
// Note: leave this as is until no one ever compiles with either gcc 4.0.1
// or Xcode 2. This seems to work around the pred_iterator assert in PR 2207
- E = pred_end(*I);
+ E = pred_end(P);
++I;
}
return false;
// 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...
+ // Create our unconditional branch.
BranchInst::Create(DestBB, NewBB);
// Branch to the new block, breaking the edge.
// 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.
- //
- for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
- PHINode *PN = cast<PHINode>(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.
- int BBIdx = PN->getBasicBlockIndex(TIBB);
- PN->setIncomingBlock(BBIdx, NewBB);
+ 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 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
// loop header) then NewBB dominates DestBB.
SmallVector<BasicBlock*, 8> OtherPreds;
- for (pred_iterator I = pred_begin(DestBB), E = pred_end(DestBB); I != E; ++I)
- if (*I != NewBB)
- OtherPreds.push_back(*I);
-
+ // 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) {
+ BasicBlock *P = *I;
+ if (P != NewBB)
+ OtherPreds.push_back(P);
+ }
+ }
+
bool NewBBDominatesDestBB = true;
// Should we update DominatorTree information?
- if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
+ if (DT) {
DomTreeNode *TINode = DT->getNode(TIBB);
// The new block is not the immediate dominator for any other nodes, but
}
// Should we update DominanceFrontier information?
- if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>()) {
+ if (DF) {
// If NewBBDominatesDestBB hasn't been computed yet, do so with DF.
if (!OtherPreds.empty()) {
// FIXME: IMPLEMENT THIS!
}
// Update LoopInfo if it is around.
- if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>()) {
+ 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 (TIL == DestLoop) {
// Both in the same loop, the NewBB joins loop.
DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
- } else if (TIL->contains(DestLoop->getHeader())) {
+ } 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->getHeader())) {
+ } 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 {
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);
+ I != E; ++I) {
+ BasicBlock *P = *I;
+ if (TIL->contains(P))
+ Preds.push_back(P);
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
}
// Update ProfileInfo if it is around.
- if (ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>()) {
- PI->splitEdge(TIBB,DestBB,NewBB,MergeIdenticalEdges);
- }
+ if (PI)
+ PI->splitEdge(TIBB, DestBB, NewBB, MergeIdenticalEdges);
return NewBB;
}
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