- // we should sink to.
- // We give successors with smaller loop depth higher priority.
- SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(), MBB->succ_end());
- // Sort Successors according to their loop depth.
+ // we should sink to. If we have reliable block frequency information
+ // (frequency != 0) available, give successors with smaller frequencies
+ // higher priority, otherwise prioritize smaller loop depths.
+ SmallVector<MachineBasicBlock*, 4> Succs(MBB->succ_begin(),
+ MBB->succ_end());
+
+ // Handle cases where sinking can happen but where the sink point isn't a
+ // successor. For example:
+ //
+ // x = computation
+ // if () {} else {}
+ // use x
+ //
+ const std::vector<MachineDomTreeNode *> &Children =
+ DT->getNode(MBB)->getChildren();
+ for (const auto &DTChild : Children)
+ // DomTree children of MBB that have MBB as immediate dominator are added.
+ if (DTChild->getIDom()->getBlock() == MI->getParent() &&
+ // Skip MBBs already added to the Succs vector above.
+ !MBB->isSuccessor(DTChild->getBlock()))
+ Succs.push_back(DTChild->getBlock());
+
+ // Sort Successors according to their loop depth or block frequency info.