| 1 | //===- LoopTraversal.cpp - Optimal basic block traversal order --*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #include "llvm/CodeGen/LoopTraversal.h" |
| 10 | #include "llvm/ADT/PostOrderIterator.h" |
| 11 | #include "llvm/CodeGen/MachineFunction.h" |
| 12 | |
| 13 | using namespace llvm; |
| 14 | |
| 15 | bool LoopTraversal::isBlockDone(MachineBasicBlock *MBB) { |
| 16 | unsigned MBBNumber = MBB->getNumber(); |
| 17 | assert(MBBNumber < MBBInfos.size() && "Unexpected basic block number."); |
| 18 | return MBBInfos[MBBNumber].PrimaryCompleted && |
| 19 | MBBInfos[MBBNumber].IncomingCompleted == |
| 20 | MBBInfos[MBBNumber].PrimaryIncoming && |
| 21 | MBBInfos[MBBNumber].IncomingProcessed == MBB->pred_size(); |
| 22 | } |
| 23 | |
| 24 | LoopTraversal::TraversalOrder LoopTraversal::traverse(MachineFunction &MF) { |
| 25 | // Initialize the MMBInfos |
| 26 | MBBInfos.assign(NumElts: MF.getNumBlockIDs(), Elt: MBBInfo()); |
| 27 | |
| 28 | MachineBasicBlock *Entry = &*MF.begin(); |
| 29 | ReversePostOrderTraversal<MachineBasicBlock *> RPOT(Entry); |
| 30 | SmallVector<MachineBasicBlock *, 4> Workqueue; |
| 31 | SmallVector<TraversedMBBInfo, 4> MBBTraversalOrder; |
| 32 | for (MachineBasicBlock *MBB : RPOT) { |
| 33 | // N.B: IncomingProcessed and IncomingCompleted were already updated while |
| 34 | // processing this block's predecessors. |
| 35 | unsigned MBBNumber = MBB->getNumber(); |
| 36 | assert(MBBNumber < MBBInfos.size() && "Unexpected basic block number."); |
| 37 | MBBInfos[MBBNumber].PrimaryCompleted = true; |
| 38 | MBBInfos[MBBNumber].PrimaryIncoming = MBBInfos[MBBNumber].IncomingProcessed; |
| 39 | bool Primary = true; |
| 40 | Workqueue.push_back(Elt: MBB); |
| 41 | while (!Workqueue.empty()) { |
| 42 | MachineBasicBlock *ActiveMBB = Workqueue.pop_back_val(); |
| 43 | bool Done = isBlockDone(MBB: ActiveMBB); |
| 44 | MBBTraversalOrder.push_back(Elt: TraversedMBBInfo(ActiveMBB, Primary, Done)); |
| 45 | for (MachineBasicBlock *Succ : ActiveMBB->successors()) { |
| 46 | unsigned SuccNumber = Succ->getNumber(); |
| 47 | assert(SuccNumber < MBBInfos.size() && |
| 48 | "Unexpected basic block number."); |
| 49 | if (!isBlockDone(MBB: Succ)) { |
| 50 | if (Primary) |
| 51 | MBBInfos[SuccNumber].IncomingProcessed++; |
| 52 | if (Done) |
| 53 | MBBInfos[SuccNumber].IncomingCompleted++; |
| 54 | if (isBlockDone(MBB: Succ)) |
| 55 | Workqueue.push_back(Elt: Succ); |
| 56 | } |
| 57 | } |
| 58 | Primary = false; |
| 59 | } |
| 60 | } |
| 61 | |
| 62 | // We need to go through again and finalize any blocks that are not done yet. |
| 63 | // This is possible if blocks have dead predecessors, so we didn't visit them |
| 64 | // above. |
| 65 | for (MachineBasicBlock *MBB : RPOT) { |
| 66 | if (!isBlockDone(MBB)) |
| 67 | MBBTraversalOrder.push_back(Elt: TraversedMBBInfo(MBB, false, true)); |
| 68 | // Don't update successors here. We'll get to them anyway through this |
| 69 | // loop. |
| 70 | } |
| 71 | |
| 72 | MBBInfos.clear(); |
| 73 | |
| 74 | return MBBTraversalOrder; |
| 75 | } |
| 76 |