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extend it a bit, and make use of it in all schedulers, to ensure consistent checking. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59689 91177308-0d34-0410-b5e6-96231b3b80d8
243 lines
7.7 KiB
C++
243 lines
7.7 KiB
C++
//===----- SchedulePostRAList.cpp - list scheduler ------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// 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 "post-RA-sched"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/ScheduleDAGInstrs.h"
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#include "llvm/CodeGen/LatencyPriorityQueue.h"
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#include "llvm/CodeGen/SchedulerRegistry.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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STATISTIC(NumStalls, "Number of pipeline stalls");
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namespace {
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class VISIBILITY_HIDDEN PostRAScheduler : public MachineFunctionPass {
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public:
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static char ID;
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PostRAScheduler() : MachineFunctionPass(&ID) {}
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private:
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MachineFunction *MF;
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const TargetMachine *TM;
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public:
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const char *getPassName() const {
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return "Post RA top-down list latency scheduler (STUB)";
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}
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bool runOnMachineFunction(MachineFunction &Fn);
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};
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char PostRAScheduler::ID = 0;
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class VISIBILITY_HIDDEN SchedulePostRATDList : public ScheduleDAGInstrs {
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public:
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SchedulePostRATDList(MachineBasicBlock *mbb, const TargetMachine &tm)
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: ScheduleDAGInstrs(mbb, tm) {}
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private:
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MachineFunction *MF;
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const TargetMachine *TM;
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/// AvailableQueue - The priority queue to use for the available SUnits.
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///
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LatencyPriorityQueue 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.
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std::vector<SUnit*> PendingQueue;
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public:
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const char *getPassName() const {
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return "Post RA top-down list latency scheduler (STUB)";
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}
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bool runOnMachineFunction(MachineFunction &Fn);
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void Schedule();
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private:
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void ReleaseSucc(SUnit *SU, 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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}
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bool PostRAScheduler::runOnMachineFunction(MachineFunction &Fn) {
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DOUT << "PostRAScheduler\n";
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MF = &Fn;
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TM = &MF->getTarget();
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// Loop over all of the basic blocks
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for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
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MBB != MBBe; ++MBB) {
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SchedulePostRATDList Scheduler(MBB, *TM);
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Scheduler.Run();
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Scheduler.EmitSchedule();
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}
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return true;
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}
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/// Schedule - Schedule the DAG using list scheduling.
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void SchedulePostRATDList::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(SUnits);
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ListScheduleTopDown();
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AvailableQueue.releaseState();
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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. Also update its cycle bound.
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void SchedulePostRATDList::ReleaseSucc(SUnit *SU, SUnit *SuccSU, bool isChain) {
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--SuccSU->NumPredsLeft;
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#ifndef NDEBUG
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if (SuccSU->NumPredsLeft < 0) {
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cerr << "*** Scheduling failed! ***\n";
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SuccSU->dump(this);
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cerr << " has been released too many times!\n";
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assert(0);
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}
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#endif
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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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// 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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unsigned PredDoneCycle = SU->Cycle;
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if (!isChain)
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PredDoneCycle += SU->Latency;
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else if (SU->Latency)
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PredDoneCycle += 1;
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SuccSU->CycleBound = std::max(SuccSU->CycleBound, PredDoneCycle);
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if (SuccSU->NumPredsLeft == 0) {
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PendingQueue.push_back(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 SchedulePostRATDList::ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle) {
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DOUT << "*** Scheduling [" << CurCycle << "]: ";
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DEBUG(SU->dump(this));
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Sequence.push_back(SU);
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SU->Cycle = CurCycle;
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// Top down: 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(SU, I->Dep, I->isCtrl);
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SU->isScheduled = true;
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AvailableQueue.ScheduledNode(SU);
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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 SchedulePostRATDList::ListScheduleTopDown() {
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unsigned CurCycle = 0;
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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.empty()) {
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AvailableQueue.push(&SUnits[i]);
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SUnits[i].isAvailable = true;
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}
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}
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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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Sequence.reserve(SUnits.size());
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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]->CycleBound == CurCycle) {
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AvailableQueue.push(PendingQueue[i]);
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PendingQueue[i]->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]->CycleBound > 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 = AvailableQueue.pop();
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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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// 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 {
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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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++NumStalls;
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++CurCycle;
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}
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}
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#ifndef NDEBUG
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VerifySchedule(/*isBottomUp=*/false);
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#endif
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}
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//===----------------------------------------------------------------------===//
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// Public Constructor Functions
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//===----------------------------------------------------------------------===//
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FunctionPass *llvm::createPostRAScheduler() {
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return new PostRAScheduler();
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}
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