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llvm-project/llvm/lib/Target/AMDGPU/GCNIterativeScheduler.cpp

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//===--------------------- GCNIterativeScheduler.cpp - --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file
//
//===----------------------------------------------------------------------===//
#include "GCNIterativeScheduler.h"
#include "GCNSchedStrategy.h"
#include "SIMachineFunctionInfo.h"
using namespace llvm;
#define DEBUG_TYPE "misched"
namespace llvm {
std::vector<const SUnit*> makeMinRegSchedule(ArrayRef<const SUnit*> TopRoots,
const ScheduleDAG &DAG);
}
// shim accessors for different order containers
static inline MachineInstr *getMachineInstr(MachineInstr *MI) {
return MI;
}
static inline MachineInstr *getMachineInstr(const SUnit *SU) {
return SU->getInstr();
}
static inline MachineInstr *getMachineInstr(const SUnit &SU) {
return SU.getInstr();
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD
static void printRegion(raw_ostream &OS,
MachineBasicBlock::iterator Begin,
MachineBasicBlock::iterator End,
const LiveIntervals *LIS,
unsigned MaxInstNum =
std::numeric_limits<unsigned>::max()) {
auto BB = Begin->getParent();
OS << BB->getParent()->getName() << ":BB#" << BB->getNumber()
<< ' ' << BB->getName() << ":\n";
auto I = Begin;
MaxInstNum = std::max(MaxInstNum, 1u);
for (; I != End && MaxInstNum; ++I, --MaxInstNum) {
if (!I->isDebugValue() && LIS)
OS << LIS->getInstructionIndex(*I);
OS << '\t' << *I;
}
if (I != End) {
OS << "\t...\n";
I = std::prev(End);
if (!I->isDebugValue() && LIS)
OS << LIS->getInstructionIndex(*I);
OS << '\t' << *I;
}
if (End != BB->end()) { // print boundary inst if present
OS << "----\n";
if (LIS) OS << LIS->getInstructionIndex(*End) << '\t';
OS << *End;
}
}
LLVM_DUMP_METHOD
static void printLivenessInfo(raw_ostream &OS,
MachineBasicBlock::iterator Begin,
MachineBasicBlock::iterator End,
const LiveIntervals *LIS) {
const auto BB = Begin->getParent();
const auto &MRI = BB->getParent()->getRegInfo();
const auto LiveIns = getLiveRegsBefore(*Begin, *LIS);
OS << "LIn RP: ";
getRegPressure(MRI, LiveIns).print(OS);
const auto BottomMI = End == BB->end() ? std::prev(End) : End;
const auto LiveOuts = getLiveRegsAfter(*BottomMI, *LIS);
OS << "LOt RP: ";
getRegPressure(MRI, LiveOuts).print(OS);
}
LLVM_DUMP_METHOD
void GCNIterativeScheduler::printRegions(raw_ostream &OS) const {
const auto &ST = MF.getSubtarget<SISubtarget>();
for (const auto R : Regions) {
OS << "Region to schedule ";
printRegion(OS, R->Begin, R->End, LIS, 1);
printLivenessInfo(OS, R->Begin, R->End, LIS);
OS << "Max RP: ";
R->MaxPressure.print(OS, &ST);
}
}
LLVM_DUMP_METHOD
void GCNIterativeScheduler::printSchedResult(raw_ostream &OS,
const Region *R,
const GCNRegPressure &RP) const {
OS << "\nAfter scheduling ";
printRegion(OS, R->Begin, R->End, LIS);
printSchedRP(OS, R->MaxPressure, RP);
OS << '\n';
}
LLVM_DUMP_METHOD
void GCNIterativeScheduler::printSchedRP(raw_ostream &OS,
const GCNRegPressure &Before,
const GCNRegPressure &After) const {
const auto &ST = MF.getSubtarget<SISubtarget>();
OS << "RP before: ";
Before.print(OS, &ST);
OS << "RP after: ";
After.print(OS, &ST);
}
#endif
// DAG builder helper
class GCNIterativeScheduler::BuildDAG {
GCNIterativeScheduler &Sch;
SmallVector<SUnit*, 8> TopRoots;
public:
BuildDAG(const Region &R, GCNIterativeScheduler &_Sch)
: Sch(_Sch) {
auto BB = R.Begin->getParent();
Sch.BaseClass::startBlock(BB);
Sch.BaseClass::enterRegion(BB, R.Begin, R.End, R.NumRegionInstrs);
Sch.buildSchedGraph(Sch.AA, nullptr, nullptr, nullptr,
/*TrackLaneMask*/true);
Sch.Topo.InitDAGTopologicalSorting();
SmallVector<SUnit*, 8> BotRoots;
Sch.findRootsAndBiasEdges(TopRoots, BotRoots);
}
~BuildDAG() {
Sch.BaseClass::exitRegion();
Sch.BaseClass::finishBlock();
}
ArrayRef<const SUnit*> getTopRoots() const {
return TopRoots;
}
};
class GCNIterativeScheduler::OverrideLegacyStrategy {
GCNIterativeScheduler &Sch;
Region &Rgn;
std::unique_ptr<MachineSchedStrategy> SaveSchedImpl;
GCNRegPressure SaveMaxRP;
public:
OverrideLegacyStrategy(Region &R,
MachineSchedStrategy &OverrideStrategy,
GCNIterativeScheduler &_Sch)
: Sch(_Sch)
, Rgn(R)
, SaveSchedImpl(std::move(_Sch.SchedImpl))
, SaveMaxRP(R.MaxPressure) {
Sch.SchedImpl.reset(&OverrideStrategy);
auto BB = R.Begin->getParent();
Sch.BaseClass::startBlock(BB);
Sch.BaseClass::enterRegion(BB, R.Begin, R.End, R.NumRegionInstrs);
}
~OverrideLegacyStrategy() {
Sch.BaseClass::exitRegion();
Sch.BaseClass::finishBlock();
Sch.SchedImpl.release();
Sch.SchedImpl = std::move(SaveSchedImpl);
}
void schedule() {
assert(Sch.RegionBegin == Rgn.Begin && Sch.RegionEnd == Rgn.End);
DEBUG(dbgs() << "\nScheduling ";
printRegion(dbgs(), Rgn.Begin, Rgn.End, Sch.LIS, 2));
Sch.BaseClass::schedule();
// Unfortunatelly placeDebugValues incorrectly modifies RegionEnd, restore
Sch.RegionEnd = Rgn.End;
//assert(Rgn.End == Sch.RegionEnd);
Rgn.Begin = Sch.RegionBegin;
Rgn.MaxPressure.clear();
}
void restoreOrder() {
assert(Sch.RegionBegin == Rgn.Begin && Sch.RegionEnd == Rgn.End);
// DAG SUnits are stored using original region's order
// so just use SUnits as the restoring schedule
Sch.scheduleRegion(Rgn, Sch.SUnits, SaveMaxRP);
}
};
namespace {
// just a stub to make base class happy
class SchedStrategyStub : public MachineSchedStrategy {
public:
bool shouldTrackPressure() const override { return false; }
bool shouldTrackLaneMasks() const override { return false; }
void initialize(ScheduleDAGMI *DAG) override {}
SUnit *pickNode(bool &IsTopNode) override { return nullptr; }
void schedNode(SUnit *SU, bool IsTopNode) override {}
void releaseTopNode(SUnit *SU) override {}
void releaseBottomNode(SUnit *SU) override {}
};
} // namespace
GCNIterativeScheduler::GCNIterativeScheduler(MachineSchedContext *C,
StrategyKind S)
: BaseClass(C, llvm::make_unique<SchedStrategyStub>())
, Context(C)
, Strategy(S)
, UPTracker(*LIS) {
}
// returns max pressure for a region
GCNRegPressure
GCNIterativeScheduler::getRegionPressure(MachineBasicBlock::iterator Begin,
MachineBasicBlock::iterator End)
const {
// For the purpose of pressure tracking bottom inst of the region should
// be also processed. End is either BB end, BB terminator inst or sched
// boundary inst.
auto const BBEnd = Begin->getParent()->end();
auto const BottomMI = End == BBEnd ? std::prev(End) : End;
// scheduleRegions walks bottom to top, so its likely we just get next
// instruction to track
auto AfterBottomMI = std::next(BottomMI);
if (AfterBottomMI == BBEnd ||
&*AfterBottomMI != UPTracker.getLastTrackedMI()) {
UPTracker.reset(*BottomMI);
} else {
assert(UPTracker.isValid());
}
for (auto I = BottomMI; I != Begin; --I)
UPTracker.recede(*I);
UPTracker.recede(*Begin);
assert(UPTracker.isValid() ||
(dbgs() << "Tracked region ",
printRegion(dbgs(), Begin, End, LIS), false));
return UPTracker.moveMaxPressure();
}
// returns max pressure for a tentative schedule
template <typename Range> GCNRegPressure
GCNIterativeScheduler::getSchedulePressure(const Region &R,
Range &&Schedule) const {
auto const BBEnd = R.Begin->getParent()->end();
GCNUpwardRPTracker RPTracker(*LIS);
if (R.End != BBEnd) {
// R.End points to the boundary instruction but the
// schedule doesn't include it
RPTracker.reset(*R.End);
RPTracker.recede(*R.End);
} else {
// R.End doesn't point to the boundary instruction
RPTracker.reset(*std::prev(BBEnd));
}
for (auto I = Schedule.end(), B = Schedule.begin(); I != B;) {
RPTracker.recede(*getMachineInstr(*--I));
}
return RPTracker.moveMaxPressure();
}
void GCNIterativeScheduler::enterRegion(MachineBasicBlock *BB, // overriden
MachineBasicBlock::iterator Begin,
MachineBasicBlock::iterator End,
unsigned NumRegionInstrs) {
BaseClass::enterRegion(BB, Begin, End, NumRegionInstrs);
if (NumRegionInstrs > 2) {
Regions.push_back(
new (Alloc.Allocate())
Region { Begin, End, NumRegionInstrs,
getRegionPressure(Begin, End), nullptr });
}
}
void GCNIterativeScheduler::schedule() { // overriden
// do nothing
DEBUG(
printLivenessInfo(dbgs(), RegionBegin, RegionEnd, LIS);
if (!Regions.empty() && Regions.back()->Begin == RegionBegin) {
dbgs() << "Max RP: ";
Regions.back()->MaxPressure.print(dbgs(), &MF.getSubtarget<SISubtarget>());
}
dbgs() << '\n';
);
}
void GCNIterativeScheduler::finalizeSchedule() { // overriden
if (Regions.empty())
return;
switch (Strategy) {
case SCHEDULE_MINREGONLY: scheduleMinReg(); break;
case SCHEDULE_MINREGFORCED: scheduleMinReg(true); break;
case SCHEDULE_LEGACYMAXOCCUPANCY: scheduleLegacyMaxOccupancy(); break;
}
}
// Detach schedule from SUnits and interleave it with debug values.
// Returned schedule becomes independent of DAG state.
std::vector<MachineInstr*>
GCNIterativeScheduler::detachSchedule(ScheduleRef Schedule) const {
std::vector<MachineInstr*> Res;
Res.reserve(Schedule.size() * 2);
if (FirstDbgValue)
Res.push_back(FirstDbgValue);
const auto DbgB = DbgValues.begin(), DbgE = DbgValues.end();
for (auto SU : Schedule) {
Res.push_back(SU->getInstr());
const auto &D = std::find_if(DbgB, DbgE, [SU](decltype(*DbgB) &P) {
return P.second == SU->getInstr();
});
if (D != DbgE)
Res.push_back(D->first);
}
return Res;
}
void GCNIterativeScheduler::setBestSchedule(Region &R,
ScheduleRef Schedule,
const GCNRegPressure &MaxRP) {
R.BestSchedule.reset(
new TentativeSchedule{ detachSchedule(Schedule), MaxRP });
}
void GCNIterativeScheduler::scheduleBest(Region &R) {
assert(R.BestSchedule.get() && "No schedule specified");
scheduleRegion(R, R.BestSchedule->Schedule, R.BestSchedule->MaxPressure);
R.BestSchedule.reset();
}
// minimal required region scheduler, works for ranges of SUnits*,
// SUnits or MachineIntrs*
template <typename Range>
void GCNIterativeScheduler::scheduleRegion(Region &R, Range &&Schedule,
const GCNRegPressure &MaxRP) {
assert(RegionBegin == R.Begin && RegionEnd == R.End);
assert(LIS != nullptr);
#ifndef NDEBUG
const auto SchedMaxRP = getSchedulePressure(R, Schedule);
#endif
auto BB = R.Begin->getParent();
auto Top = R.Begin;
for (const auto &I : Schedule) {
auto MI = getMachineInstr(I);
if (MI != &*Top) {
BB->remove(MI);
BB->insert(Top, MI);
if (!MI->isDebugValue())
LIS->handleMove(*MI, true);
}
if (!MI->isDebugValue()) {
// Reset read - undef flags and update them later.
for (auto &Op : MI->operands())
if (Op.isReg() && Op.isDef())
Op.setIsUndef(false);
RegisterOperands RegOpers;
RegOpers.collect(*MI, *TRI, MRI, /*ShouldTrackLaneMasks*/true,
/*IgnoreDead*/false);
// Adjust liveness and add missing dead+read-undef flags.
auto SlotIdx = LIS->getInstructionIndex(*MI).getRegSlot();
RegOpers.adjustLaneLiveness(*LIS, MRI, SlotIdx, MI);
}
Top = std::next(MI->getIterator());
}
RegionBegin = getMachineInstr(Schedule.front());
// Schedule consisting of MachineInstr* is considered 'detached'
// and already interleaved with debug values
if (!std::is_same<decltype(*Schedule.begin()), MachineInstr*>::value) {
placeDebugValues();
// Unfortunatelly placeDebugValues incorrectly modifies RegionEnd, restore
//assert(R.End == RegionEnd);
RegionEnd = R.End;
}
R.Begin = RegionBegin;
R.MaxPressure = MaxRP;
#ifndef NDEBUG
const auto RegionMaxRP = getRegionPressure(R);
const auto &ST = MF.getSubtarget<SISubtarget>();
#endif
assert((SchedMaxRP == RegionMaxRP && (MaxRP.empty() || SchedMaxRP == MaxRP))
|| (dbgs() << "Max RP mismatch!!!\n"
"RP for schedule (calculated): ",
SchedMaxRP.print(dbgs(), &ST),
dbgs() << "RP for schedule (reported): ",
MaxRP.print(dbgs(), &ST),
dbgs() << "RP after scheduling: ",
RegionMaxRP.print(dbgs(), &ST),
false));
}
// Sort recorded regions by pressure - highest at the front
void GCNIterativeScheduler::sortRegionsByPressure(unsigned TargetOcc) {
const auto &ST = MF.getSubtarget<SISubtarget>();
std::sort(Regions.begin(), Regions.end(),
[&ST, TargetOcc](const Region *R1, const Region *R2) {
return R2->MaxPressure.less(ST, R1->MaxPressure, TargetOcc);
});
}
///////////////////////////////////////////////////////////////////////////////
// Legacy MaxOccupancy Strategy
// Tries to increase occupancy applying minreg scheduler for a sequence of
// most demanding regions. Obtained schedules are saved as BestSchedule for a
// region.
// TargetOcc is the best achievable occupancy for a kernel.
// Returns better occupancy on success or current occupancy on fail.
// BestSchedules aren't deleted on fail.
unsigned GCNIterativeScheduler::tryMaximizeOccupancy(unsigned TargetOcc) {
// TODO: assert Regions are sorted descending by pressure
const auto &ST = MF.getSubtarget<SISubtarget>();
const auto Occ = Regions.front()->MaxPressure.getOccupancy(ST);
DEBUG(dbgs() << "Trying to to improve occupancy, target = " << TargetOcc
<< ", current = " << Occ << '\n');
auto NewOcc = TargetOcc;
for (auto R : Regions) {
if (R->MaxPressure.getOccupancy(ST) >= NewOcc)
break;
DEBUG(printRegion(dbgs(), R->Begin, R->End, LIS, 3);
printLivenessInfo(dbgs(), R->Begin, R->End, LIS));
BuildDAG DAG(*R, *this);
const auto MinSchedule = makeMinRegSchedule(DAG.getTopRoots(), *this);
const auto MaxRP = getSchedulePressure(*R, MinSchedule);
DEBUG(dbgs() << "Occupancy improvement attempt:\n";
printSchedRP(dbgs(), R->MaxPressure, MaxRP));
NewOcc = std::min(NewOcc, MaxRP.getOccupancy(ST));
if (NewOcc <= Occ)
break;
setBestSchedule(*R, MinSchedule, MaxRP);
}
DEBUG(dbgs() << "New occupancy = " << NewOcc
<< ", prev occupancy = " << Occ << '\n');
return std::max(NewOcc, Occ);
}
void GCNIterativeScheduler::scheduleLegacyMaxOccupancy(
bool TryMaximizeOccupancy) {
const auto &ST = MF.getSubtarget<SISubtarget>();
auto TgtOcc = ST.getOccupancyWithLocalMemSize(MF);
sortRegionsByPressure(TgtOcc);
auto Occ = Regions.front()->MaxPressure.getOccupancy(ST);
if (TryMaximizeOccupancy && Occ < TgtOcc)
Occ = tryMaximizeOccupancy(TgtOcc);
// This is really weird but for some magic scheduling regions twice
// gives performance improvement
const int NumPasses = Occ < TgtOcc ? 2 : 1;
TgtOcc = std::min(Occ, TgtOcc);
DEBUG(dbgs() << "Scheduling using default scheduler, "
"target occupancy = " << TgtOcc << '\n');
GCNMaxOccupancySchedStrategy LStrgy(Context);
for (int I = 0; I < NumPasses; ++I) {
// running first pass with TargetOccupancy = 0 mimics previous scheduling
// approach and is a performance magic
LStrgy.setTargetOccupancy(I == 0 ? 0 : TgtOcc);
for (auto R : Regions) {
OverrideLegacyStrategy Ovr(*R, LStrgy, *this);
Ovr.schedule();
const auto RP = getRegionPressure(*R);
DEBUG(printSchedRP(dbgs(), R->MaxPressure, RP));
if (RP.getOccupancy(ST) < TgtOcc) {
DEBUG(dbgs() << "Didn't fit into target occupancy O" << TgtOcc);
if (R->BestSchedule.get() &&
R->BestSchedule->MaxPressure.getOccupancy(ST) >= TgtOcc) {
DEBUG(dbgs() << ", scheduling minimal register\n");
scheduleBest(*R);
} else {
DEBUG(dbgs() << ", restoring\n");
Ovr.restoreOrder();
assert(R->MaxPressure.getOccupancy(ST) >= TgtOcc);
}
}
}
}
}
///////////////////////////////////////////////////////////////////////////////
// Minimal Register Strategy
void GCNIterativeScheduler::scheduleMinReg(bool force) {
const auto &ST = MF.getSubtarget<SISubtarget>();
const auto TgtOcc = ST.getOccupancyWithLocalMemSize(MF);
sortRegionsByPressure(TgtOcc);
auto MaxPressure = Regions.front()->MaxPressure;
for (auto R : Regions) {
if (!force && R->MaxPressure.less(ST, MaxPressure, TgtOcc))
break;
BuildDAG DAG(*R, *this);
const auto MinSchedule = makeMinRegSchedule(DAG.getTopRoots(), *this);
const auto RP = getSchedulePressure(*R, MinSchedule);
DEBUG(if (R->MaxPressure.less(ST, RP, TgtOcc)) {
dbgs() << "\nWarning: Pressure becomes worse after minreg!";
printSchedRP(dbgs(), R->MaxPressure, RP);
});
if (!force && MaxPressure.less(ST, RP, TgtOcc))
break;
scheduleRegion(*R, MinSchedule, RP);
DEBUG(printSchedResult(dbgs(), R, RP));
MaxPressure = RP;
}
}
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