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llvm-project/llvm/lib/CodeGen/PostRASchedulerList.cpp

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//===----- SchedulePostRAList.cpp - list scheduler ------------------------===//
//
// 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 "post-RA-sched"
#include "llvm/CodeGen/Passes.h"
#include "AggressiveAntiDepBreaker.h"
#include "AntiDepBreaker.h"
#include "CriticalAntiDepBreaker.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/LatencyPriorityQueue.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/CodeGen/SchedulerRegistry.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
STATISTIC(NumNoops, "Number of noops inserted");
STATISTIC(NumStalls, "Number of pipeline stalls");
STATISTIC(NumFixedAnti, "Number of fixed anti-dependencies");
// Post-RA scheduling is enabled with
// TargetSubtargetInfo.enablePostRAScheduler(). This flag can be used to
// override the target.
static cl::opt<bool>
EnablePostRAScheduler("post-RA-scheduler",
cl::desc("Enable scheduling after register allocation"),
cl::init(false), cl::Hidden);
static cl::opt<std::string>
EnableAntiDepBreaking("break-anti-dependencies",
cl::desc("Break post-RA scheduling anti-dependencies: "
"\"critical\", \"all\", or \"none\""),
cl::init("none"), cl::Hidden);
// If DebugDiv > 0 then only schedule MBB with (ID % DebugDiv) == DebugMod
static cl::opt<int>
DebugDiv("postra-sched-debugdiv",
cl::desc("Debug control MBBs that are scheduled"),
cl::init(0), cl::Hidden);
static cl::opt<int>
DebugMod("postra-sched-debugmod",
cl::desc("Debug control MBBs that are scheduled"),
cl::init(0), cl::Hidden);
AntiDepBreaker::~AntiDepBreaker() { }
namespace {
class PostRAScheduler : public MachineFunctionPass {
const TargetInstrInfo *TII;
RegisterClassInfo RegClassInfo;
public:
static char ID;
PostRAScheduler() : MachineFunctionPass(ID) {}
void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<AliasAnalysis>();
AU.addRequired<TargetPassConfig>();
AU.addRequired<MachineDominatorTree>();
AU.addPreserved<MachineDominatorTree>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
bool runOnMachineFunction(MachineFunction &Fn);
};
char PostRAScheduler::ID = 0;
class SchedulePostRATDList : public ScheduleDAGInstrs {
/// AvailableQueue - The priority queue to use for the available SUnits.
///
LatencyPriorityQueue 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 becomes available, the instruction is
/// added to the AvailableQueue.
std::vector<SUnit*> PendingQueue;
/// HazardRec - The hazard recognizer to use.
ScheduleHazardRecognizer *HazardRec;
/// AntiDepBreak - Anti-dependence breaking object, or NULL if none
AntiDepBreaker *AntiDepBreak;
/// AA - AliasAnalysis for making memory reference queries.
AliasAnalysis *AA;
/// LiveRegs - true if the register is live.
BitVector LiveRegs;
/// The schedule. Null SUnit*'s represent noop instructions.
std::vector<SUnit*> Sequence;
public:
SchedulePostRATDList(
MachineFunction &MF, MachineLoopInfo &MLI, MachineDominatorTree &MDT,
AliasAnalysis *AA, const RegisterClassInfo&,
TargetSubtargetInfo::AntiDepBreakMode AntiDepMode,
SmallVectorImpl<const TargetRegisterClass*> &CriticalPathRCs);
~SchedulePostRATDList();
/// startBlock - Initialize register live-range state for scheduling in
/// this block.
///
void startBlock(MachineBasicBlock *BB);
/// Initialize the scheduler state for the next scheduling region.
virtual void enterRegion(MachineBasicBlock *bb,
MachineBasicBlock::iterator begin,
MachineBasicBlock::iterator end,
unsigned endcount);
/// Notify that the scheduler has finished scheduling the current region.
virtual void exitRegion();
/// Schedule - Schedule the instruction range using list scheduling.
///
void schedule();
void EmitSchedule();
/// Observe - Update liveness information to account for the current
/// instruction, which will not be scheduled.
///
void Observe(MachineInstr *MI, unsigned Count);
/// finishBlock - Clean up register live-range state.
///
void finishBlock();
/// FixupKills - Fix register kill flags that have been made
/// invalid due to scheduling
///
void FixupKills(MachineBasicBlock *MBB);
private:
void ReleaseSucc(SUnit *SU, SDep *SuccEdge);
void ReleaseSuccessors(SUnit *SU);
void ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle);
void ListScheduleTopDown();
void StartBlockForKills(MachineBasicBlock *BB);
// ToggleKillFlag - Toggle a register operand kill flag. Other
// adjustments may be made to the instruction if necessary. Return
// true if the operand has been deleted, false if not.
bool ToggleKillFlag(MachineInstr *MI, MachineOperand &MO);
void dumpSchedule() const;
};
}
char &llvm::PostRASchedulerID = PostRAScheduler::ID;
INITIALIZE_PASS(PostRAScheduler, "post-RA-sched",
"Post RA top-down list latency scheduler", false, false)
SchedulePostRATDList::SchedulePostRATDList(
MachineFunction &MF, MachineLoopInfo &MLI, MachineDominatorTree &MDT,
AliasAnalysis *AA, const RegisterClassInfo &RCI,
TargetSubtargetInfo::AntiDepBreakMode AntiDepMode,
SmallVectorImpl<const TargetRegisterClass*> &CriticalPathRCs)
: ScheduleDAGInstrs(MF, MLI, MDT, /*IsPostRA=*/true), AA(AA),
LiveRegs(TRI->getNumRegs())
{
const TargetMachine &TM = MF.getTarget();
const InstrItineraryData *InstrItins = TM.getInstrItineraryData();
HazardRec =
TM.getInstrInfo()->CreateTargetPostRAHazardRecognizer(InstrItins, this);
assert((AntiDepMode == TargetSubtargetInfo::ANTIDEP_NONE ||
MRI.tracksLiveness()) &&
"Live-ins must be accurate for anti-dependency breaking");
AntiDepBreak =
((AntiDepMode == TargetSubtargetInfo::ANTIDEP_ALL) ?
(AntiDepBreaker *)new AggressiveAntiDepBreaker(MF, RCI, CriticalPathRCs) :
((AntiDepMode == TargetSubtargetInfo::ANTIDEP_CRITICAL) ?
(AntiDepBreaker *)new CriticalAntiDepBreaker(MF, RCI) : NULL));
}
SchedulePostRATDList::~SchedulePostRATDList() {
delete HazardRec;
delete AntiDepBreak;
}
/// Initialize state associated with the next scheduling region.
void SchedulePostRATDList::enterRegion(MachineBasicBlock *bb,
MachineBasicBlock::iterator begin,
MachineBasicBlock::iterator end,
unsigned endcount) {
ScheduleDAGInstrs::enterRegion(bb, begin, end, endcount);
Sequence.clear();
}
/// Print the schedule before exiting the region.
void SchedulePostRATDList::exitRegion() {
DEBUG({
dbgs() << "*** Final schedule ***\n";
dumpSchedule();
dbgs() << '\n';
});
ScheduleDAGInstrs::exitRegion();
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// dumpSchedule - dump the scheduled Sequence.
void SchedulePostRATDList::dumpSchedule() const {
for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
if (SUnit *SU = Sequence[i])
SU->dump(this);
else
dbgs() << "**** NOOP ****\n";
}
}
#endif
bool PostRAScheduler::runOnMachineFunction(MachineFunction &Fn) {
TII = Fn.getTarget().getInstrInfo();
MachineLoopInfo &MLI = getAnalysis<MachineLoopInfo>();
MachineDominatorTree &MDT = getAnalysis<MachineDominatorTree>();
AliasAnalysis *AA = &getAnalysis<AliasAnalysis>();
TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>();
RegClassInfo.runOnMachineFunction(Fn);
// Check for explicit enable/disable of post-ra scheduling.
TargetSubtargetInfo::AntiDepBreakMode AntiDepMode =
TargetSubtargetInfo::ANTIDEP_NONE;
SmallVector<const TargetRegisterClass*, 4> CriticalPathRCs;
if (EnablePostRAScheduler.getPosition() > 0) {
if (!EnablePostRAScheduler)
return false;
} else {
// Check that post-RA scheduling is enabled for this target.
// This may upgrade the AntiDepMode.
const TargetSubtargetInfo &ST = Fn.getTarget().getSubtarget<TargetSubtargetInfo>();
if (!ST.enablePostRAScheduler(PassConfig->getOptLevel(), AntiDepMode,
CriticalPathRCs))
return false;
}
// Check for antidep breaking override...
if (EnableAntiDepBreaking.getPosition() > 0) {
AntiDepMode = (EnableAntiDepBreaking == "all")
? TargetSubtargetInfo::ANTIDEP_ALL
: ((EnableAntiDepBreaking == "critical")
? TargetSubtargetInfo::ANTIDEP_CRITICAL
: TargetSubtargetInfo::ANTIDEP_NONE);
}
DEBUG(dbgs() << "PostRAScheduler\n");
SchedulePostRATDList Scheduler(Fn, MLI, MDT, AA, RegClassInfo, AntiDepMode,
CriticalPathRCs);
// Loop over all of the basic blocks
for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
MBB != MBBe; ++MBB) {
#ifndef NDEBUG
// If DebugDiv > 0 then only schedule MBB with (ID % DebugDiv) == DebugMod
if (DebugDiv > 0) {
static int bbcnt = 0;
if (bbcnt++ % DebugDiv != DebugMod)
continue;
dbgs() << "*** DEBUG scheduling " << Fn.getName()
<< ":BB#" << MBB->getNumber() << " ***\n";
}
#endif
// Initialize register live-range state for scheduling in this block.
Scheduler.startBlock(MBB);
// Schedule each sequence of instructions not interrupted by a label
// or anything else that effectively needs to shut down scheduling.
MachineBasicBlock::iterator Current = MBB->end();
unsigned Count = MBB->size(), CurrentCount = Count;
for (MachineBasicBlock::iterator I = Current; I != MBB->begin(); ) {
MachineInstr *MI = llvm::prior(I);
// Calls are not scheduling boundaries before register allocation, but
// post-ra we don't gain anything by scheduling across calls since we
// don't need to worry about register pressure.
if (MI->isCall() || TII->isSchedulingBoundary(MI, MBB, Fn)) {
Scheduler.enterRegion(MBB, I, Current, CurrentCount);
Scheduler.schedule();
Scheduler.exitRegion();
Scheduler.EmitSchedule();
Current = MI;
CurrentCount = Count - 1;
Scheduler.Observe(MI, CurrentCount);
}
I = MI;
--Count;
if (MI->isBundle())
Count -= MI->getBundleSize();
}
assert(Count == 0 && "Instruction count mismatch!");
assert((MBB->begin() == Current || CurrentCount != 0) &&
"Instruction count mismatch!");
Scheduler.enterRegion(MBB, MBB->begin(), Current, CurrentCount);
Scheduler.schedule();
Scheduler.exitRegion();
Scheduler.EmitSchedule();
// Clean up register live-range state.
Scheduler.finishBlock();
// Update register kills
Scheduler.FixupKills(MBB);
}
return true;
}
/// StartBlock - Initialize register live-range state for scheduling in
/// this block.
///
void SchedulePostRATDList::startBlock(MachineBasicBlock *BB) {
// Call the superclass.
ScheduleDAGInstrs::startBlock(BB);
// Reset the hazard recognizer and anti-dep breaker.
HazardRec->Reset();
if (AntiDepBreak != NULL)
AntiDepBreak->StartBlock(BB);
}
/// Schedule - Schedule the instruction range using list scheduling.
///
void SchedulePostRATDList::schedule() {
// Build the scheduling graph.
buildSchedGraph(AA);
if (AntiDepBreak != NULL) {
unsigned Broken =
AntiDepBreak->BreakAntiDependencies(SUnits, RegionBegin, RegionEnd,
EndIndex, DbgValues);
if (Broken != 0) {
// We made changes. Update the dependency graph.
// Theoretically we could update the graph in place:
// When a live range is changed to use a different register, remove
// the def's anti-dependence *and* output-dependence edges due to
// that register, and add new anti-dependence and output-dependence
// edges based on the next live range of the register.
ScheduleDAG::clearDAG();
buildSchedGraph(AA);
NumFixedAnti += Broken;
}
}
DEBUG(dbgs() << "********** List Scheduling **********\n");
DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su)
SUnits[su].dumpAll(this));
AvailableQueue.initNodes(SUnits);
ListScheduleTopDown();
AvailableQueue.releaseState();
}
/// Observe - Update liveness information to account for the current
/// instruction, which will not be scheduled.
///
void SchedulePostRATDList::Observe(MachineInstr *MI, unsigned Count) {
if (AntiDepBreak != NULL)
AntiDepBreak->Observe(MI, Count, EndIndex);
}
/// FinishBlock - Clean up register live-range state.
///
void SchedulePostRATDList::finishBlock() {
if (AntiDepBreak != NULL)
AntiDepBreak->FinishBlock();
// Call the superclass.
ScheduleDAGInstrs::finishBlock();
}
/// StartBlockForKills - Initialize register live-range state for updating kills
///
void SchedulePostRATDList::StartBlockForKills(MachineBasicBlock *BB) {
// Start with no live registers.
LiveRegs.reset();
// Determine the live-out physregs for this block.
if (!BB->empty() && BB->back().isReturn()) {
// In a return block, examine the function live-out regs.
for (MachineRegisterInfo::liveout_iterator I = MRI.liveout_begin(),
E = MRI.liveout_end(); I != E; ++I) {
unsigned Reg = *I;
LiveRegs.set(Reg);
// Repeat, for all subregs.
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
LiveRegs.set(*SubRegs);
}
}
else {
// In a non-return block, examine the live-in regs of all successors.
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI) {
for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
E = (*SI)->livein_end(); I != E; ++I) {
unsigned Reg = *I;
LiveRegs.set(Reg);
// Repeat, for all subregs.
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
LiveRegs.set(*SubRegs);
}
}
}
}
bool SchedulePostRATDList::ToggleKillFlag(MachineInstr *MI,
MachineOperand &MO) {
// Setting kill flag...
if (!MO.isKill()) {
MO.setIsKill(true);
return false;
}
// If MO itself is live, clear the kill flag...
if (LiveRegs.test(MO.getReg())) {
MO.setIsKill(false);
return false;
}
// If any subreg of MO is live, then create an imp-def for that
// subreg and keep MO marked as killed.
MO.setIsKill(false);
bool AllDead = true;
const unsigned SuperReg = MO.getReg();
MachineInstrBuilder MIB(MF, MI);
for (MCSubRegIterator SubRegs(SuperReg, TRI); SubRegs.isValid(); ++SubRegs) {
if (LiveRegs.test(*SubRegs)) {
MIB.addReg(*SubRegs, RegState::ImplicitDefine);
AllDead = false;
}
}
if(AllDead)
MO.setIsKill(true);
return false;
}
/// FixupKills - Fix the register kill flags, they may have been made
/// incorrect by instruction reordering.
///
void SchedulePostRATDList::FixupKills(MachineBasicBlock *MBB) {
DEBUG(dbgs() << "Fixup kills for BB#" << MBB->getNumber() << '\n');
BitVector killedRegs(TRI->getNumRegs());
StartBlockForKills(MBB);
// Examine block from end to start...
unsigned Count = MBB->size();
for (MachineBasicBlock::iterator I = MBB->end(), E = MBB->begin();
I != E; --Count) {
MachineInstr *MI = --I;
if (MI->isDebugValue())
continue;
// Update liveness. Registers that are defed but not used in this
// instruction are now dead. Mark register and all subregs as they
// are completely defined.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isRegMask())
LiveRegs.clearBitsNotInMask(MO.getRegMask());
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (!MO.isDef()) continue;
// Ignore two-addr defs.
if (MI->isRegTiedToUseOperand(i)) continue;
LiveRegs.reset(Reg);
// Repeat for all subregs.
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
LiveRegs.reset(*SubRegs);
}
// Examine all used registers and set/clear kill flag. When a
// register is used multiple times we only set the kill flag on
// the first use.
killedRegs.reset();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isUse()) continue;
unsigned Reg = MO.getReg();
if ((Reg == 0) || MRI.isReserved(Reg)) continue;
bool kill = false;
if (!killedRegs.test(Reg)) {
kill = true;
// A register is not killed if any subregs are live...
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
if (LiveRegs.test(*SubRegs)) {
kill = false;
break;
}
}
// If subreg is not live, then register is killed if it became
// live in this instruction
if (kill)
kill = !LiveRegs.test(Reg);
}
if (MO.isKill() != kill) {
DEBUG(dbgs() << "Fixing " << MO << " in ");
// Warning: ToggleKillFlag may invalidate MO.
ToggleKillFlag(MI, MO);
DEBUG(MI->dump());
}
killedRegs.set(Reg);
}
// Mark any used register (that is not using undef) and subregs as
// now live...
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue;
unsigned Reg = MO.getReg();
if ((Reg == 0) || MRI.isReserved(Reg)) continue;
LiveRegs.set(Reg);
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
LiveRegs.set(*SubRegs);
}
}
}
//===----------------------------------------------------------------------===//
// Top-Down Scheduling
//===----------------------------------------------------------------------===//
/// ReleaseSucc - Decrement the NumPredsLeft count of a successor. Add it to
/// the PendingQueue if the count reaches zero.
void SchedulePostRATDList::ReleaseSucc(SUnit *SU, SDep *SuccEdge) {
SUnit *SuccSU = SuccEdge->getSUnit();
if (SuccEdge->isWeak()) {
--SuccSU->WeakPredsLeft;
return;
}
#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;
// Standard scheduler algorithms will recompute the depth of the successor
// here as such:
// SuccSU->setDepthToAtLeast(SU->getDepth() + SuccEdge->getLatency());
//
// However, we lazily compute node depth instead. Note that
// ScheduleNodeTopDown has already updated the depth of this node which causes
// all descendents to be marked dirty. Setting the successor depth explicitly
// here would cause depth to be recomputed for all its ancestors. If the
// successor is not yet ready (because of a transitively redundant edge) then
// this causes depth computation to be quadratic in the size of the DAG.
// 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);
}
/// ReleaseSuccessors - Call ReleaseSucc on each of SU's successors.
void SchedulePostRATDList::ReleaseSuccessors(SUnit *SU) {
for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
I != E; ++I) {
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 SchedulePostRATDList::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 SchedulePostRATDList::ListScheduleTopDown() {
unsigned CurCycle = 0;
// We're scheduling top-down but we're visiting the regions in
// bottom-up order, so we don't know the hazards at the start of a
// region. So assume no hazards (this should usually be ok as most
// blocks are a single region).
HazardRec->Reset();
// Release any successors of the special Entry node.
ReleaseSuccessors(&EntrySU);
// Add 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].NumPredsLeft && !SUnits[i].isAvailable) {
AvailableQueue.push(&SUnits[i]);
SUnits[i].isAvailable = true;
}
}
// In any cycle where we can't schedule any instructions, we must
// stall or emit a noop, depending on the target.
bool CycleHasInsts = false;
// 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.
unsigned MinDepth = ~0u;
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 if (PendingQueue[i]->getDepth() < MinDepth)
MinDepth = PendingQueue[i]->getDepth();
}
DEBUG(dbgs() << "\n*** Examining Available\n"; AvailableQueue.dump(this));
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...
if (FoundSUnit) {
// ... schedule the node...
ScheduleNodeTopDown(FoundSUnit, CurCycle);
HazardRec->EmitInstruction(FoundSUnit);
CycleHasInsts = true;
if (HazardRec->atIssueLimit()) {
DEBUG(dbgs() << "*** Max instructions per cycle " << CurCycle << '\n');
HazardRec->AdvanceCycle();
++CurCycle;
CycleHasInsts = false;
}
} else {
if (CycleHasInsts) {
DEBUG(dbgs() << "*** Finished cycle " << CurCycle << '\n');
HazardRec->AdvanceCycle();
} else if (!HasNoopHazards) {
// Otherwise, we have a pipeline stall, but no other problem,
// just advance the current cycle and try again.
DEBUG(dbgs() << "*** Stall in cycle " << CurCycle << '\n');
HazardRec->AdvanceCycle();
++NumStalls;
} 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 in cycle " << CurCycle << '\n');
HazardRec->EmitNoop();
Sequence.push_back(0); // NULL here means noop
++NumNoops;
}
++CurCycle;
CycleHasInsts = false;
}
}
#ifndef NDEBUG
unsigned ScheduledNodes = VerifyScheduledDAG(/*isBottomUp=*/false);
unsigned Noops = 0;
for (unsigned i = 0, e = Sequence.size(); i != e; ++i)
if (!Sequence[i])
++Noops;
assert(Sequence.size() - Noops == ScheduledNodes &&
"The number of nodes scheduled doesn't match the expected number!");
#endif // NDEBUG
}
// EmitSchedule - Emit the machine code in scheduled order.
void SchedulePostRATDList::EmitSchedule() {
RegionBegin = RegionEnd;
// If first instruction was a DBG_VALUE then put it back.
if (FirstDbgValue)
BB->splice(RegionEnd, BB, FirstDbgValue);
// Then re-insert them according to the given schedule.
for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
if (SUnit *SU = Sequence[i])
BB->splice(RegionEnd, BB, SU->getInstr());
else
// Null SUnit* is a noop.
TII->insertNoop(*BB, RegionEnd);
// Update the Begin iterator, as the first instruction in the block
// may have been scheduled later.
if (i == 0)
RegionBegin = prior(RegionEnd);
}
// Reinsert any remaining debug_values.
for (std::vector<std::pair<MachineInstr *, MachineInstr *> >::iterator
DI = DbgValues.end(), DE = DbgValues.begin(); DI != DE; --DI) {
std::pair<MachineInstr *, MachineInstr *> P = *prior(DI);
MachineInstr *DbgValue = P.first;
MachineBasicBlock::iterator OrigPrivMI = P.second;
BB->splice(++OrigPrivMI, BB, DbgValue);
}
DbgValues.clear();
FirstDbgValue = NULL;
}
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