llvm/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGVLIW.cpp

//===- ScheduleDAGVLIW.cpp - SelectionDAG list scheduler for VLIW -*- C++ -*-=//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This implements a top-down list scheduler, using standard algorithms.
// The basic approach uses a priority queue of available nodes to schedule.
// One at a time, nodes are taken from the priority queue (thus in priority
// order), checked for legality to schedule, and emitted if legal.
//
// Nodes may not be legal to schedule either due to structural hazards (e.g.
// pipeline or resource constraints) or because an input to the instruction has
// not completed execution.
//
//===----------------------------------------------------------------------===//

#include "ScheduleDAGSDNodes.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/ResourcePriorityQueue.h"
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/CodeGen/SchedulerRegistry.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumNoops , "Number of noops inserted");
STATISTIC(NumStalls, "Number of pipeline stalls");

static RegisterScheduler
  VLIWScheduler("vliw-td", "VLIW scheduler",
                createVLIWDAGScheduler);

namespace {
//===----------------------------------------------------------------------===//
/// ScheduleDAGVLIW - The actual DFA list scheduler implementation.  This
/// supports / top-down scheduling.
///
class ScheduleDAGVLIW : public ScheduleDAGSDNodes { … };
}  // end anonymous namespace

/// Schedule - Schedule the DAG using list scheduling.
void ScheduleDAGVLIW::Schedule() { … }

//===----------------------------------------------------------------------===//
//  Top-Down Scheduling
//===----------------------------------------------------------------------===//

/// releaseSucc - Decrement the NumPredsLeft count of a successor. Add it to
/// the PendingQueue if the count reaches zero. Also update its cycle bound.
void ScheduleDAGVLIW::releaseSucc(SUnit *SU, const SDep &D) { … }

void ScheduleDAGVLIW::releaseSuccessors(SUnit *SU) { … }

/// scheduleNodeTopDown - Add the node to the schedule. Decrement the pending
/// count of its successors. If a successor pending count is zero, add it to
/// the Available queue.
void ScheduleDAGVLIW::scheduleNodeTopDown(SUnit *SU, unsigned CurCycle) { … }

/// listScheduleTopDown - The main loop of list scheduling for top-down
/// schedulers.
void ScheduleDAGVLIW::listScheduleTopDown() { … }

//===----------------------------------------------------------------------===//
//                         Public Constructor Functions
//===----------------------------------------------------------------------===//

/// createVLIWDAGScheduler - This creates a top-down list scheduler.
ScheduleDAGSDNodes *llvm::createVLIWDAGScheduler(SelectionDAGISel *IS,
                                                 CodeGenOptLevel) { … }