INITIALIZE_PASS(BreakCriticalEdges, "break-crit-edges",
"Break critical edges in CFG", false, false)
-// Publically exposed interface to pass...
+// Publicly exposed interface to pass...
char &llvm::BreakCriticalEdgesID = BreakCriticalEdges::ID;
FunctionPass *llvm::createBreakCriticalEdgesPass() {
return new BreakCriticalEdges();
BasicBlock *TIBB = TI->getParent();
BasicBlock *DestBB = TI->getSuccessor(SuccNum);
+ // Splitting the critical edge to a landing pad block is non-trivial. Don't do
+ // it in this generic function.
+ assert(!DestBB->isLandingPad() &&
+ "Cannot split critical edge to a landing pad block!");
+
// 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);
+ BranchInst *NewBI = BranchInst::Create(DestBB, NewBB);
+ NewBI->setDebugLoc(TI->getDebugLoc());
// Branch to the new block, breaking the edge.
TI->setSuccessor(SuccNum, 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);
- }
- }
+ {
+ 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);
}
}
}
// For each unique exit block...
+ // FIXME: This code is functionally equivalent to the corresponding
+ // loop in LoopSimplify.
SmallVector<BasicBlock *, 4> ExitBlocks;
TIL->getExitBlocks(ExitBlocks);
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit);
I != E; ++I) {
BasicBlock *P = *I;
- if (TIL->contains(P))
+ if (TIL->contains(P)) {
+ if (isa<IndirectBrInst>(P->getTerminator())) {
+ Preds.clear();
+ break;
+ }
Preds.push_back(P);
- else
+ } 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