// at this point.
FuncInfo->clear();
+ // XXX-update: Right after instruction selection, check through the
+ // intentionally added fake conditional branches and mark them as unremovable.
+ for (auto& MBB : *MF) {
+ // Check whether MBB has two successors which only contains an unconditional
+ // branch to the same destination.
+ if (MBB.succ_size() != 2 ||
+ !MBB.getLastNonDebugInstr()->isUnconditionalBranch()) {
+ continue;
+ }
+ auto MBBSuccIter = MBB.succ_begin();
+ auto* Succ1 = *MBBSuccIter;
+ MBBSuccIter++;
+ auto* Succ2 = *MBBSuccIter;
+
+ MachineBasicBlock* Succ1Succ = nullptr;
+ MachineBasicBlock* Succ2Succ = nullptr;
+ if ((Succ1->size() == 1 && Succ1->begin()->isUnconditionalBranch()) ||
+ (Succ1->size() == 0)) {
+ Succ1Succ = *Succ1->succ_begin();
+ }
+ if ((Succ2->size() == 1 && Succ2->begin()->isUnconditionalBranch()) ||
+ (Succ2->size() == 0)) {
+ Succ2Succ = *Succ2->succ_begin();
+ }
+
+ bool HasCommonDest = Succ1Succ && Succ1Succ == Succ2Succ;
+ if (HasCommonDest) {
+ auto MBBIter = MBB.end();
+ std::advance(MBBIter, -2);
+ assert(MBBIter->isConditionalBranch());
+ MBBIter->disableCanEliminateMachineInstr();
+ MBB.disableCanEliminateMachineBB();
+ Succ1->disableCanEliminateMachineBB();
+ Succ2->disableCanEliminateMachineBB();
+ Succ1Succ->disableCanEliminateMachineBB();
+ DEBUG(dbgs() << "Mark as unremovable machine basic block: " << MBB
+ << "\nMark as unremovable branch instruction: " << *MBBIter
+ << "\n");
+ }
+ }
+
DEBUG(dbgs() << "*** MachineFunction at end of ISel ***\n");
DEBUG(MF->print(dbgs()));