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https://github.com/c64scene-ar/llvm-6502.git
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speeds up isel as a whole time by 2.6%. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33810 91177308-0d34-0410-b5e6-96231b3b80d8
532 lines
18 KiB
C++
532 lines
18 KiB
C++
//===---- ScheduleDAGList.cpp - Implement a list scheduler for isel DAG ---===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Evan Cheng and is distributed under the
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// University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This implements a top-down list scheduler, using standard algorithms.
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// The basic approach uses a priority queue of available nodes to schedule.
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// One at a time, nodes are taken from the priority queue (thus in priority
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// order), checked for legality to schedule, and emitted if legal.
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//
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// Nodes may not be legal to schedule either due to structural hazards (e.g.
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// pipeline or resource constraints) or because an input to the instruction has
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// not completed execution.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "sched"
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#include "llvm/CodeGen/ScheduleDAG.h"
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#include "llvm/CodeGen/SchedulerRegistry.h"
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#include "llvm/CodeGen/SelectionDAGISel.h"
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#include "llvm/CodeGen/SSARegMap.h"
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#include "llvm/Target/MRegisterInfo.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/ADT/Statistic.h"
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#include <climits>
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#include <queue>
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using namespace llvm;
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STATISTIC(NumNoops , "Number of noops inserted");
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STATISTIC(NumStalls, "Number of pipeline stalls");
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static RegisterScheduler
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tdListDAGScheduler("list-td", " Top-down list scheduler",
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createTDListDAGScheduler);
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namespace {
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//===----------------------------------------------------------------------===//
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/// ScheduleDAGList - The actual list scheduler implementation. This supports
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/// top-down scheduling.
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///
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class VISIBILITY_HIDDEN ScheduleDAGList : public ScheduleDAG {
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private:
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/// AvailableQueue - The priority queue to use for the available SUnits.
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///
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SchedulingPriorityQueue *AvailableQueue;
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/// PendingQueue - This contains all of the instructions whose operands have
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/// been issued, but their results are not ready yet (due to the latency of
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/// the operation). Once the operands becomes available, the instruction is
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/// added to the AvailableQueue. This keeps track of each SUnit and the
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/// number of cycles left to execute before the operation is available.
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std::vector<std::pair<unsigned, SUnit*> > PendingQueue;
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/// HazardRec - The hazard recognizer to use.
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HazardRecognizer *HazardRec;
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public:
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ScheduleDAGList(SelectionDAG &dag, MachineBasicBlock *bb,
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const TargetMachine &tm,
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SchedulingPriorityQueue *availqueue,
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HazardRecognizer *HR)
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: ScheduleDAG(dag, bb, tm),
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AvailableQueue(availqueue), HazardRec(HR) {
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}
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~ScheduleDAGList() {
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delete HazardRec;
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delete AvailableQueue;
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}
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void Schedule();
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private:
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void ReleaseSucc(SUnit *SuccSU, bool isChain);
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void ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle);
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void ListScheduleTopDown();
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};
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} // end anonymous namespace
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HazardRecognizer::~HazardRecognizer() {}
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/// Schedule - Schedule the DAG using list scheduling.
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void ScheduleDAGList::Schedule() {
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DOUT << "********** List Scheduling **********\n";
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// Build scheduling units.
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BuildSchedUnits();
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AvailableQueue->initNodes(SUnitMap, SUnits);
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ListScheduleTopDown();
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AvailableQueue->releaseState();
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DOUT << "*** Final schedule ***\n";
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DEBUG(dumpSchedule());
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DOUT << "\n";
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// Emit in scheduled order
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EmitSchedule();
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}
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//===----------------------------------------------------------------------===//
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// Top-Down Scheduling
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//===----------------------------------------------------------------------===//
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/// ReleaseSucc - Decrement the NumPredsLeft count of a successor. Add it to
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/// the PendingQueue if the count reaches zero.
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void ScheduleDAGList::ReleaseSucc(SUnit *SuccSU, bool isChain) {
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if (!isChain)
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SuccSU->NumPredsLeft--;
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else
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SuccSU->NumChainPredsLeft--;
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assert(SuccSU->NumPredsLeft >= 0 && SuccSU->NumChainPredsLeft >= 0 &&
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"List scheduling internal error");
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if ((SuccSU->NumPredsLeft + SuccSU->NumChainPredsLeft) == 0) {
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// Compute how many cycles it will be before this actually becomes
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// available. This is the max of the start time of all predecessors plus
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// their latencies.
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unsigned AvailableCycle = 0;
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for (SUnit::pred_iterator I = SuccSU->Preds.begin(),
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E = SuccSU->Preds.end(); I != E; ++I) {
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// If this is a token edge, we don't need to wait for the latency of the
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// preceeding instruction (e.g. a long-latency load) unless there is also
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// some other data dependence.
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SUnit &Pred = *I->first;
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unsigned PredDoneCycle = Pred.Cycle;
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if (!I->second)
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PredDoneCycle += Pred.Latency;
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else if (Pred.Latency)
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PredDoneCycle += 1;
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AvailableCycle = std::max(AvailableCycle, PredDoneCycle);
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}
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PendingQueue.push_back(std::make_pair(AvailableCycle, SuccSU));
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}
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}
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/// ScheduleNodeTopDown - Add the node to the schedule. Decrement the pending
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/// count of its successors. If a successor pending count is zero, add it to
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/// the Available queue.
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void ScheduleDAGList::ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle) {
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DOUT << "*** Scheduling [" << CurCycle << "]: ";
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DEBUG(SU->dump(&DAG));
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Sequence.push_back(SU);
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SU->Cycle = CurCycle;
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// Bottom up: release successors.
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for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
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I != E; ++I)
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ReleaseSucc(I->first, I->second);
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}
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/// ListScheduleTopDown - The main loop of list scheduling for top-down
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/// schedulers.
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void ScheduleDAGList::ListScheduleTopDown() {
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unsigned CurCycle = 0;
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SUnit *Entry = SUnitMap[DAG.getEntryNode().Val];
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// All leaves to Available queue.
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for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
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// It is available if it has no predecessors.
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if (SUnits[i].Preds.size() == 0 && &SUnits[i] != Entry) {
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AvailableQueue->push(&SUnits[i]);
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SUnits[i].isAvailable = SUnits[i].isPending = true;
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}
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}
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// Emit the entry node first.
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ScheduleNodeTopDown(Entry, CurCycle);
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HazardRec->EmitInstruction(Entry->Node);
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// While Available queue is not empty, grab the node with the highest
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// priority. If it is not ready put it back. Schedule the node.
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std::vector<SUnit*> NotReady;
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while (!AvailableQueue->empty() || !PendingQueue.empty()) {
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// Check to see if any of the pending instructions are ready to issue. If
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// so, add them to the available queue.
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for (unsigned i = 0, e = PendingQueue.size(); i != e; ++i) {
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if (PendingQueue[i].first == CurCycle) {
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AvailableQueue->push(PendingQueue[i].second);
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PendingQueue[i].second->isAvailable = true;
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PendingQueue[i] = PendingQueue.back();
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PendingQueue.pop_back();
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--i; --e;
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} else {
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assert(PendingQueue[i].first > CurCycle && "Negative latency?");
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}
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}
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// If there are no instructions available, don't try to issue anything, and
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// don't advance the hazard recognizer.
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if (AvailableQueue->empty()) {
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++CurCycle;
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continue;
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}
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SUnit *FoundSUnit = 0;
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SDNode *FoundNode = 0;
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bool HasNoopHazards = false;
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while (!AvailableQueue->empty()) {
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SUnit *CurSUnit = AvailableQueue->pop();
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// Get the node represented by this SUnit.
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FoundNode = CurSUnit->Node;
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// If this is a pseudo op, like copyfromreg, look to see if there is a
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// real target node flagged to it. If so, use the target node.
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for (unsigned i = 0, e = CurSUnit->FlaggedNodes.size();
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FoundNode->getOpcode() < ISD::BUILTIN_OP_END && i != e; ++i)
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FoundNode = CurSUnit->FlaggedNodes[i];
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HazardRecognizer::HazardType HT = HazardRec->getHazardType(FoundNode);
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if (HT == HazardRecognizer::NoHazard) {
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FoundSUnit = CurSUnit;
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break;
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}
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// Remember if this is a noop hazard.
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HasNoopHazards |= HT == HazardRecognizer::NoopHazard;
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NotReady.push_back(CurSUnit);
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}
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// Add the nodes that aren't ready back onto the available list.
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if (!NotReady.empty()) {
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AvailableQueue->push_all(NotReady);
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NotReady.clear();
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}
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// If we found a node to schedule, do it now.
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if (FoundSUnit) {
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ScheduleNodeTopDown(FoundSUnit, CurCycle);
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HazardRec->EmitInstruction(FoundNode);
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FoundSUnit->isScheduled = true;
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AvailableQueue->ScheduledNode(FoundSUnit);
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// If this is a pseudo-op node, we don't want to increment the current
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// cycle.
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if (FoundSUnit->Latency) // Don't increment CurCycle for pseudo-ops!
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++CurCycle;
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} else if (!HasNoopHazards) {
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// Otherwise, we have a pipeline stall, but no other problem, just advance
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// the current cycle and try again.
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DOUT << "*** Advancing cycle, no work to do\n";
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HazardRec->AdvanceCycle();
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++NumStalls;
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++CurCycle;
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} else {
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// Otherwise, we have no instructions to issue and we have instructions
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// that will fault if we don't do this right. This is the case for
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// processors without pipeline interlocks and other cases.
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DOUT << "*** Emitting noop\n";
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HazardRec->EmitNoop();
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Sequence.push_back(0); // NULL SUnit* -> noop
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++NumNoops;
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++CurCycle;
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}
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}
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#ifndef NDEBUG
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// Verify that all SUnits were scheduled.
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bool AnyNotSched = false;
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for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
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if (SUnits[i].NumPredsLeft != 0 || SUnits[i].NumChainPredsLeft != 0) {
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if (!AnyNotSched)
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cerr << "*** List scheduling failed! ***\n";
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SUnits[i].dump(&DAG);
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cerr << "has not been scheduled!\n";
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AnyNotSched = true;
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}
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}
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assert(!AnyNotSched);
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#endif
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}
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//===----------------------------------------------------------------------===//
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// LatencyPriorityQueue Implementation
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//===----------------------------------------------------------------------===//
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//
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// This is a SchedulingPriorityQueue that schedules using latency information to
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// reduce the length of the critical path through the basic block.
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//
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namespace {
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class LatencyPriorityQueue;
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/// Sorting functions for the Available queue.
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struct latency_sort : public std::binary_function<SUnit*, SUnit*, bool> {
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LatencyPriorityQueue *PQ;
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latency_sort(LatencyPriorityQueue *pq) : PQ(pq) {}
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latency_sort(const latency_sort &RHS) : PQ(RHS.PQ) {}
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bool operator()(const SUnit* left, const SUnit* right) const;
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};
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} // end anonymous namespace
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namespace {
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class LatencyPriorityQueue : public SchedulingPriorityQueue {
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// SUnits - The SUnits for the current graph.
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std::vector<SUnit> *SUnits;
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// Latencies - The latency (max of latency from this node to the bb exit)
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// for each node.
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std::vector<int> Latencies;
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/// NumNodesSolelyBlocking - This vector contains, for every node in the
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/// Queue, the number of nodes that the node is the sole unscheduled
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/// predecessor for. This is used as a tie-breaker heuristic for better
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/// mobility.
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std::vector<unsigned> NumNodesSolelyBlocking;
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std::priority_queue<SUnit*, std::vector<SUnit*>, latency_sort> Queue;
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public:
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LatencyPriorityQueue() : Queue(latency_sort(this)) {
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}
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void initNodes(DenseMap<SDNode*, SUnit*> &sumap,
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std::vector<SUnit> &sunits) {
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SUnits = &sunits;
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// Calculate node priorities.
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CalculatePriorities();
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}
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void releaseState() {
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SUnits = 0;
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Latencies.clear();
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}
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unsigned getLatency(unsigned NodeNum) const {
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assert(NodeNum < Latencies.size());
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return Latencies[NodeNum];
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}
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unsigned getNumSolelyBlockNodes(unsigned NodeNum) const {
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assert(NodeNum < NumNodesSolelyBlocking.size());
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return NumNodesSolelyBlocking[NodeNum];
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}
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bool empty() const { return Queue.empty(); }
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virtual void push(SUnit *U) {
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push_impl(U);
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}
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void push_impl(SUnit *U);
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void push_all(const std::vector<SUnit *> &Nodes) {
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for (unsigned i = 0, e = Nodes.size(); i != e; ++i)
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push_impl(Nodes[i]);
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}
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SUnit *pop() {
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if (empty()) return NULL;
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SUnit *V = Queue.top();
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Queue.pop();
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return V;
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}
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// ScheduledNode - As nodes are scheduled, we look to see if there are any
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// successor nodes that have a single unscheduled predecessor. If so, that
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// single predecessor has a higher priority, since scheduling it will make
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// the node available.
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void ScheduledNode(SUnit *Node);
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private:
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void CalculatePriorities();
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int CalcLatency(const SUnit &SU);
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void AdjustPriorityOfUnscheduledPreds(SUnit *SU);
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SUnit *getSingleUnscheduledPred(SUnit *SU);
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/// RemoveFromPriorityQueue - This is a really inefficient way to remove a
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/// node from a priority queue. We should roll our own heap to make this
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/// better or something.
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void RemoveFromPriorityQueue(SUnit *SU) {
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std::vector<SUnit*> Temp;
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assert(!Queue.empty() && "Not in queue!");
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while (Queue.top() != SU) {
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Temp.push_back(Queue.top());
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Queue.pop();
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assert(!Queue.empty() && "Not in queue!");
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}
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// Remove the node from the PQ.
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Queue.pop();
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// Add all the other nodes back.
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for (unsigned i = 0, e = Temp.size(); i != e; ++i)
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Queue.push(Temp[i]);
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}
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};
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}
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bool latency_sort::operator()(const SUnit *LHS, const SUnit *RHS) const {
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unsigned LHSNum = LHS->NodeNum;
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unsigned RHSNum = RHS->NodeNum;
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// The most important heuristic is scheduling the critical path.
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unsigned LHSLatency = PQ->getLatency(LHSNum);
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unsigned RHSLatency = PQ->getLatency(RHSNum);
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if (LHSLatency < RHSLatency) return true;
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if (LHSLatency > RHSLatency) return false;
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// After that, if two nodes have identical latencies, look to see if one will
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// unblock more other nodes than the other.
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unsigned LHSBlocked = PQ->getNumSolelyBlockNodes(LHSNum);
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unsigned RHSBlocked = PQ->getNumSolelyBlockNodes(RHSNum);
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if (LHSBlocked < RHSBlocked) return true;
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if (LHSBlocked > RHSBlocked) return false;
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// Finally, just to provide a stable ordering, use the node number as a
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// deciding factor.
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return LHSNum < RHSNum;
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}
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/// CalcNodePriority - Calculate the maximal path from the node to the exit.
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///
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int LatencyPriorityQueue::CalcLatency(const SUnit &SU) {
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int &Latency = Latencies[SU.NodeNum];
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if (Latency != -1)
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return Latency;
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int MaxSuccLatency = 0;
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for (SUnit::const_succ_iterator I = SU.Succs.begin(), E = SU.Succs.end();
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I != E; ++I)
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MaxSuccLatency = std::max(MaxSuccLatency, CalcLatency(*I->first));
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return Latency = MaxSuccLatency + SU.Latency;
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}
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/// CalculatePriorities - Calculate priorities of all scheduling units.
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void LatencyPriorityQueue::CalculatePriorities() {
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Latencies.assign(SUnits->size(), -1);
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NumNodesSolelyBlocking.assign(SUnits->size(), 0);
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for (unsigned i = 0, e = SUnits->size(); i != e; ++i)
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CalcLatency((*SUnits)[i]);
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}
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/// getSingleUnscheduledPred - If there is exactly one unscheduled predecessor
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/// of SU, return it, otherwise return null.
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SUnit *LatencyPriorityQueue::getSingleUnscheduledPred(SUnit *SU) {
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SUnit *OnlyAvailablePred = 0;
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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I != E; ++I) {
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SUnit &Pred = *I->first;
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if (!Pred.isScheduled) {
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// We found an available, but not scheduled, predecessor. If it's the
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// only one we have found, keep track of it... otherwise give up.
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if (OnlyAvailablePred && OnlyAvailablePred != &Pred)
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return 0;
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OnlyAvailablePred = &Pred;
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}
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}
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return OnlyAvailablePred;
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}
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void LatencyPriorityQueue::push_impl(SUnit *SU) {
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// Look at all of the successors of this node. Count the number of nodes that
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// this node is the sole unscheduled node for.
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unsigned NumNodesBlocking = 0;
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for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
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I != E; ++I)
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if (getSingleUnscheduledPred(I->first) == SU)
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++NumNodesBlocking;
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NumNodesSolelyBlocking[SU->NodeNum] = NumNodesBlocking;
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Queue.push(SU);
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}
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// ScheduledNode - As nodes are scheduled, we look to see if there are any
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// successor nodes that have a single unscheduled predecessor. If so, that
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// single predecessor has a higher priority, since scheduling it will make
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// the node available.
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void LatencyPriorityQueue::ScheduledNode(SUnit *SU) {
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for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
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I != E; ++I)
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AdjustPriorityOfUnscheduledPreds(I->first);
|
|
}
|
|
|
|
/// AdjustPriorityOfUnscheduledPreds - One of the predecessors of SU was just
|
|
/// scheduled. If SU is not itself available, then there is at least one
|
|
/// predecessor node that has not been scheduled yet. If SU has exactly ONE
|
|
/// unscheduled predecessor, we want to increase its priority: it getting
|
|
/// scheduled will make this node available, so it is better than some other
|
|
/// node of the same priority that will not make a node available.
|
|
void LatencyPriorityQueue::AdjustPriorityOfUnscheduledPreds(SUnit *SU) {
|
|
if (SU->isPending) return; // All preds scheduled.
|
|
|
|
SUnit *OnlyAvailablePred = getSingleUnscheduledPred(SU);
|
|
if (OnlyAvailablePred == 0 || !OnlyAvailablePred->isAvailable) return;
|
|
|
|
// Okay, we found a single predecessor that is available, but not scheduled.
|
|
// Since it is available, it must be in the priority queue. First remove it.
|
|
RemoveFromPriorityQueue(OnlyAvailablePred);
|
|
|
|
// Reinsert the node into the priority queue, which recomputes its
|
|
// NumNodesSolelyBlocking value.
|
|
push(OnlyAvailablePred);
|
|
}
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Public Constructor Functions
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// createTDListDAGScheduler - This creates a top-down list scheduler with a
|
|
/// new hazard recognizer. This scheduler takes ownership of the hazard
|
|
/// recognizer and deletes it when done.
|
|
ScheduleDAG* llvm::createTDListDAGScheduler(SelectionDAGISel *IS,
|
|
SelectionDAG *DAG,
|
|
MachineBasicBlock *BB) {
|
|
return new ScheduleDAGList(*DAG, BB, DAG->getTarget(),
|
|
new LatencyPriorityQueue(),
|
|
IS->CreateTargetHazardRecognizer());
|
|
}
|