76 lines
2.9 KiB
C++
76 lines
2.9 KiB
C++
//===- LoopTraversal.cpp - Optimal basic block traversal order --*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/LoopTraversal.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/CodeGen/MachineFunction.h"
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using namespace llvm;
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bool LoopTraversal::isBlockDone(MachineBasicBlock *MBB) {
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unsigned MBBNumber = MBB->getNumber();
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assert(MBBNumber < MBBInfos.size() && "Unexpected basic block number.");
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return MBBInfos[MBBNumber].PrimaryCompleted &&
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MBBInfos[MBBNumber].IncomingCompleted ==
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MBBInfos[MBBNumber].PrimaryIncoming &&
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MBBInfos[MBBNumber].IncomingProcessed == MBB->pred_size();
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}
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LoopTraversal::TraversalOrder LoopTraversal::traverse(MachineFunction &MF) {
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// Initialize the MMBInfos
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MBBInfos.assign(MF.getNumBlockIDs(), MBBInfo());
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MachineBasicBlock *Entry = &*MF.begin();
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ReversePostOrderTraversal<MachineBasicBlock *> RPOT(Entry);
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SmallVector<MachineBasicBlock *, 4> Workqueue;
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SmallVector<TraversedMBBInfo, 4> MBBTraversalOrder;
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for (MachineBasicBlock *MBB : RPOT) {
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// N.B: IncomingProcessed and IncomingCompleted were already updated while
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// processing this block's predecessors.
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unsigned MBBNumber = MBB->getNumber();
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assert(MBBNumber < MBBInfos.size() && "Unexpected basic block number.");
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MBBInfos[MBBNumber].PrimaryCompleted = true;
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MBBInfos[MBBNumber].PrimaryIncoming = MBBInfos[MBBNumber].IncomingProcessed;
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bool Primary = true;
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Workqueue.push_back(MBB);
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while (!Workqueue.empty()) {
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MachineBasicBlock *ActiveMBB = Workqueue.pop_back_val();
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bool Done = isBlockDone(ActiveMBB);
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MBBTraversalOrder.push_back(TraversedMBBInfo(ActiveMBB, Primary, Done));
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for (MachineBasicBlock *Succ : ActiveMBB->successors()) {
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unsigned SuccNumber = Succ->getNumber();
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assert(SuccNumber < MBBInfos.size() &&
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"Unexpected basic block number.");
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if (!isBlockDone(Succ)) {
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if (Primary)
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MBBInfos[SuccNumber].IncomingProcessed++;
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if (Done)
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MBBInfos[SuccNumber].IncomingCompleted++;
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if (isBlockDone(Succ))
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Workqueue.push_back(Succ);
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}
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}
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Primary = false;
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}
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}
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// We need to go through again and finalize any blocks that are not done yet.
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// This is possible if blocks have dead predecessors, so we didn't visit them
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// above.
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for (MachineBasicBlock *MBB : RPOT) {
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if (!isBlockDone(MBB))
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MBBTraversalOrder.push_back(TraversedMBBInfo(MBB, false, true));
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// Don't update successors here. We'll get to them anyway through this
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// loop.
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}
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MBBInfos.clear();
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return MBBTraversalOrder;
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}
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