Index: llvm/lib/CodeGen/MachineBlockPlacement.cpp =================================================================== --- llvm/lib/CodeGen/MachineBlockPlacement.cpp +++ llvm/lib/CodeGen/MachineBlockPlacement.cpp @@ -2730,6 +2730,30 @@ TII->removeBranch(*ChainBB); TII->insertBranch(*ChainBB, FBB, TBB, Cond, dl); ChainBB->updateTerminator(); + } else if (Cond.empty() && TBB && ChainBB != TBB && + !TBB->canFallThrough()) { + // If ChainBB unconditional branch to the TBB, and TBB has no + // fallthrough predecessor and fallthrough successor, or ChainBB has + // only one unconditonal branch and TBB has only one predecessor. We can + // do the tail dupliction for ChainBB and remove TBB. + MachineFunction::iterator I(TBB); + if (((TBB == &*F->begin()) || !std::prev(I)->isSuccessor(TBB)) && + (TailDup.isSimpleBB(ChainBB) || (TBB->pred_size() == 1))) { + TII->removeBranch(*ChainBB); + ChainBB->removeSuccessor(TBB); + + // Update the CFG. + for (MachineBasicBlock::pred_iterator PI = TBB->pred_begin(), + PE = TBB->pred_end(); PI != PE; PI++) + (*PI)->ReplaceUsesOfBlockWith(TBB, ChainBB); + + for (MachineBasicBlock *Succ : TBB->successors()) + ChainBB->addSuccessor(Succ, MBPI->getEdgeProbability(TBB, Succ)); + + // Move all the instructions of TBB to ChainBB. + ChainBB->splice(ChainBB->end(), TBB, TBB->begin(), TBB->end()); + F->remove(TBB); + } } } } Index: llvm/test/CodeGen/PowerPC/block-placement.mir =================================================================== --- llvm/test/CodeGen/PowerPC/block-placement.mir +++ llvm/test/CodeGen/PowerPC/block-placement.mir @@ -209,9 +209,9 @@ BLR8 implicit $lr8, implicit $rm, implicit killed $x3 ; CHECK: bb.5.if.else.i: - ; CHECK: B %bb.11 - - ; CHECK: bb.11: + ; CHECK-NOT: B %bb.11 ; CHECK: renamable $x3 = LI8 1 ; CHECK-NEXT: BLR8 implicit $lr8, implicit $rm, implicit killed $x3 + + ; CHECK-NOT: bb.11: ...