+++ /dev/null
-//===---- ScheduleDAGList.cpp - Implement a list scheduler for isel DAG ---===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// 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.
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "pre-RA-sched"
-#include "ScheduleDAGSDNodes.h"
-#include "llvm/CodeGen/LatencyPriorityQueue.h"
-#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
-#include "llvm/CodeGen/SchedulerRegistry.h"
-#include "llvm/CodeGen/SelectionDAGISel.h"
-#include "llvm/Target/TargetRegisterInfo.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/ADT/Statistic.h"
-#include <climits>
-using namespace llvm;
-
-STATISTIC(NumNoops , "Number of noops inserted");
-STATISTIC(NumStalls, "Number of pipeline stalls");
-
-static RegisterScheduler
- tdListDAGScheduler("list-td", "Top-down list scheduler",
- createTDListDAGScheduler);
-
-namespace {
-//===----------------------------------------------------------------------===//
-/// ScheduleDAGList - The actual list scheduler implementation. This supports
-/// top-down scheduling.
-///
-class ScheduleDAGList : public ScheduleDAGSDNodes {
-private:
- /// AvailableQueue - The priority queue to use for the available SUnits.
- ///
- SchedulingPriorityQueue *AvailableQueue;
-
- /// PendingQueue - This contains all of the instructions whose operands have
- /// been issued, but their results are not ready yet (due to the latency of
- /// the operation). Once the operands become available, the instruction is
- /// added to the AvailableQueue.
- std::vector<SUnit*> PendingQueue;
-
- /// HazardRec - The hazard recognizer to use.
- ScheduleHazardRecognizer *HazardRec;
-
-public:
- ScheduleDAGList(MachineFunction &mf,
- SchedulingPriorityQueue *availqueue)
- : ScheduleDAGSDNodes(mf), AvailableQueue(availqueue) {
-
- const TargetMachine &tm = mf.getTarget();
- HazardRec = tm.getInstrInfo()->CreateTargetHazardRecognizer(&tm, this);
- }
-
- ~ScheduleDAGList() {
- delete HazardRec;
- delete AvailableQueue;
- }
-
- void Schedule();
-
-private:
- void ReleaseSucc(SUnit *SU, const SDep &D);
- void ReleaseSuccessors(SUnit *SU);
- void ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle);
- void ListScheduleTopDown();
-};
-} // end anonymous namespace
-
-/// Schedule - Schedule the DAG using list scheduling.
-void ScheduleDAGList::Schedule() {
- DEBUG(dbgs() << "********** List Scheduling **********\n");
-
- // Build the scheduling graph.
- BuildSchedGraph(NULL);
-
- AvailableQueue->initNodes(SUnits);
-
- ListScheduleTopDown();
-
- AvailableQueue->releaseState();
-}
-
-//===----------------------------------------------------------------------===//
-// 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 ScheduleDAGList::ReleaseSucc(SUnit *SU, const SDep &D) {
- SUnit *SuccSU = D.getSUnit();
-
-#ifndef NDEBUG
- if (SuccSU->NumPredsLeft == 0) {
- dbgs() << "*** Scheduling failed! ***\n";
- SuccSU->dump(this);
- dbgs() << " has been released too many times!\n";
- llvm_unreachable(0);
- }
-#endif
- --SuccSU->NumPredsLeft;
-
- SuccSU->setDepthToAtLeast(SU->getDepth() + D.getLatency());
-
- // If all the node's predecessors are scheduled, this node is ready
- // to be scheduled. Ignore the special ExitSU node.
- if (SuccSU->NumPredsLeft == 0 && SuccSU != &ExitSU)
- PendingQueue.push_back(SuccSU);
-}
-
-void ScheduleDAGList::ReleaseSuccessors(SUnit *SU) {
- // Top down: release successors.
- for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
- I != E; ++I) {
- assert(!I->isAssignedRegDep() &&
- "The list-td scheduler doesn't yet support physreg dependencies!");
-
- ReleaseSucc(SU, *I);
- }
-}
-
-/// 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 ScheduleDAGList::ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle) {
- DEBUG(dbgs() << "*** Scheduling [" << CurCycle << "]: ");
- DEBUG(SU->dump(this));
-
- Sequence.push_back(SU);
- assert(CurCycle >= SU->getDepth() && "Node scheduled above its depth!");
- SU->setDepthToAtLeast(CurCycle);
-
- ReleaseSuccessors(SU);
- SU->isScheduled = true;
- AvailableQueue->ScheduledNode(SU);
-}
-
-/// ListScheduleTopDown - The main loop of list scheduling for top-down
-/// schedulers.
-void ScheduleDAGList::ListScheduleTopDown() {
- unsigned CurCycle = 0;
-
- // Release any successors of the special Entry node.
- ReleaseSuccessors(&EntrySU);
-
- // All leaves to Available queue.
- for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
- // It is available if it has no predecessors.
- if (SUnits[i].Preds.empty()) {
- AvailableQueue->push(&SUnits[i]);
- SUnits[i].isAvailable = true;
- }
- }
-
- // While Available queue is not empty, grab the node with the highest
- // priority. If it is not ready put it back. Schedule the node.
- std::vector<SUnit*> NotReady;
- Sequence.reserve(SUnits.size());
- while (!AvailableQueue->empty() || !PendingQueue.empty()) {
- // Check to see if any of the pending instructions are ready to issue. If
- // so, add them to the available queue.
- for (unsigned i = 0, e = PendingQueue.size(); i != e; ++i) {
- if (PendingQueue[i]->getDepth() == CurCycle) {
- AvailableQueue->push(PendingQueue[i]);
- PendingQueue[i]->isAvailable = true;
- PendingQueue[i] = PendingQueue.back();
- PendingQueue.pop_back();
- --i; --e;
- } else {
- assert(PendingQueue[i]->getDepth() > CurCycle && "Negative latency?");
- }
- }
-
- // If there are no instructions available, don't try to issue anything, and
- // don't advance the hazard recognizer.
- if (AvailableQueue->empty()) {
- ++CurCycle;
- continue;
- }
-
- SUnit *FoundSUnit = 0;
-
- bool HasNoopHazards = false;
- while (!AvailableQueue->empty()) {
- SUnit *CurSUnit = AvailableQueue->pop();
-
- ScheduleHazardRecognizer::HazardType HT =
- HazardRec->getHazardType(CurSUnit, 0/*no stalls*/);
- if (HT == ScheduleHazardRecognizer::NoHazard) {
- FoundSUnit = CurSUnit;
- break;
- }
-
- // Remember if this is a noop hazard.
- HasNoopHazards |= HT == ScheduleHazardRecognizer::NoopHazard;
-
- NotReady.push_back(CurSUnit);
- }
-
- // Add the nodes that aren't ready back onto the available list.
- if (!NotReady.empty()) {
- AvailableQueue->push_all(NotReady);
- NotReady.clear();
- }
-
- // If we found a node to schedule, do it now.
- if (FoundSUnit) {
- ScheduleNodeTopDown(FoundSUnit, CurCycle);
- HazardRec->EmitInstruction(FoundSUnit);
-
- // If this is a pseudo-op node, we don't want to increment the current
- // cycle.
- if (FoundSUnit->Latency) // Don't increment CurCycle for pseudo-ops!
- ++CurCycle;
- } else if (!HasNoopHazards) {
- // Otherwise, we have a pipeline stall, but no other problem, just advance
- // the current cycle and try again.
- DEBUG(dbgs() << "*** Advancing cycle, no work to do\n");
- HazardRec->AdvanceCycle();
- ++NumStalls;
- ++CurCycle;
- } else {
- // Otherwise, we have no instructions to issue and we have instructions
- // that will fault if we don't do this right. This is the case for
- // processors without pipeline interlocks and other cases.
- DEBUG(dbgs() << "*** Emitting noop\n");
- HazardRec->EmitNoop();
- Sequence.push_back(0); // NULL here means noop
- ++NumNoops;
- ++CurCycle;
- }
- }
-
-#ifndef NDEBUG
- VerifySchedule(/*isBottomUp=*/false);
-#endif
-}
-
-//===----------------------------------------------------------------------===//
-// Public Constructor Functions
-//===----------------------------------------------------------------------===//
-
-/// createTDListDAGScheduler - This creates a top-down list scheduler.
-ScheduleDAGSDNodes *
-llvm::createTDListDAGScheduler(SelectionDAGISel *IS, CodeGenOpt::Level) {
- return new ScheduleDAGList(*IS->MF, new LatencyPriorityQueue());
-}
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