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

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//===-- GCNSchedStrategy.cpp - GCN Scheduler Strategy ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file
/// This contains a MachineSchedStrategy implementation for maximizing wave
/// occupancy on GCN hardware.
//===----------------------------------------------------------------------===//
#include "GCNSchedStrategy.h"
#include "AMDGPUSubtarget.h"
#include "SIInstrInfo.h"
#include "SIMachineFunctionInfo.h"
#include "SIRegisterInfo.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/Support/MathExtras.h"
#define DEBUG_TYPE "machine-scheduler"
using namespace llvm;
GCNMaxOccupancySchedStrategy::GCNMaxOccupancySchedStrategy(
const MachineSchedContext *C) :
GenericScheduler(C), TargetOccupancy(0), MF(nullptr) { }
static unsigned getMaxWaves(unsigned SGPRs, unsigned VGPRs,
const MachineFunction &MF) {
const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
unsigned MinRegOccupancy = std::min(ST.getOccupancyWithNumSGPRs(SGPRs),
ST.getOccupancyWithNumVGPRs(VGPRs));
return std::min(MinRegOccupancy,
ST.getOccupancyWithLocalMemSize(MFI->getLDSSize(),
MF.getFunction()));
}
void GCNMaxOccupancySchedStrategy::initialize(ScheduleDAGMI *DAG) {
GenericScheduler::initialize(DAG);
const SIRegisterInfo *SRI = static_cast<const SIRegisterInfo*>(TRI);
MF = &DAG->MF;
const SISubtarget &ST = MF->getSubtarget<SISubtarget>();
// FIXME: This is also necessary, because some passes that run after
// scheduling and before regalloc increase register pressure.
const int ErrorMargin = 3;
SGPRExcessLimit = Context->RegClassInfo
->getNumAllocatableRegs(&AMDGPU::SGPR_32RegClass) - ErrorMargin;
VGPRExcessLimit = Context->RegClassInfo
->getNumAllocatableRegs(&AMDGPU::VGPR_32RegClass) - ErrorMargin;
if (TargetOccupancy) {
SGPRCriticalLimit = ST.getMaxNumSGPRs(TargetOccupancy, true);
VGPRCriticalLimit = ST.getMaxNumVGPRs(TargetOccupancy);
} else {
SGPRCriticalLimit = SRI->getRegPressureSetLimit(DAG->MF,
SRI->getSGPRPressureSet());
VGPRCriticalLimit = SRI->getRegPressureSetLimit(DAG->MF,
SRI->getVGPRPressureSet());
}
SGPRCriticalLimit -= ErrorMargin;
VGPRCriticalLimit -= ErrorMargin;
}
void GCNMaxOccupancySchedStrategy::initCandidate(SchedCandidate &Cand, SUnit *SU,
bool AtTop, const RegPressureTracker &RPTracker,
const SIRegisterInfo *SRI,
unsigned SGPRPressure,
unsigned VGPRPressure) {
Cand.SU = SU;
Cand.AtTop = AtTop;
// getDownwardPressure() and getUpwardPressure() make temporary changes to
// the tracker, so we need to pass those function a non-const copy.
RegPressureTracker &TempTracker = const_cast<RegPressureTracker&>(RPTracker);
std::vector<unsigned> Pressure;
std::vector<unsigned> MaxPressure;
if (AtTop)
TempTracker.getDownwardPressure(SU->getInstr(), Pressure, MaxPressure);
else {
// FIXME: I think for bottom up scheduling, the register pressure is cached
// and can be retrieved by DAG->getPressureDif(SU).
TempTracker.getUpwardPressure(SU->getInstr(), Pressure, MaxPressure);
}
unsigned NewSGPRPressure = Pressure[SRI->getSGPRPressureSet()];
unsigned NewVGPRPressure = Pressure[SRI->getVGPRPressureSet()];
// If two instructions increase the pressure of different register sets
// by the same amount, the generic scheduler will prefer to schedule the
// instruction that increases the set with the least amount of registers,
// which in our case would be SGPRs. This is rarely what we want, so
// when we report excess/critical register pressure, we do it either
// only for VGPRs or only for SGPRs.
// FIXME: Better heuristics to determine whether to prefer SGPRs or VGPRs.
const unsigned MaxVGPRPressureInc = 16;
bool ShouldTrackVGPRs = VGPRPressure + MaxVGPRPressureInc >= VGPRExcessLimit;
bool ShouldTrackSGPRs = !ShouldTrackVGPRs && SGPRPressure >= SGPRExcessLimit;
// FIXME: We have to enter REG-EXCESS before we reach the actual threshold
// to increase the likelihood we don't go over the limits. We should improve
// the analysis to look through dependencies to find the path with the least
// register pressure.
// We only need to update the RPDelata for instructions that increase
// register pressure. Instructions that decrease or keep reg pressure
// the same will be marked as RegExcess in tryCandidate() when they
// are compared with instructions that increase the register pressure.
if (ShouldTrackVGPRs && NewVGPRPressure >= VGPRExcessLimit) {
Cand.RPDelta.Excess = PressureChange(SRI->getVGPRPressureSet());
Cand.RPDelta.Excess.setUnitInc(NewVGPRPressure - VGPRExcessLimit);
}
if (ShouldTrackSGPRs && NewSGPRPressure >= SGPRExcessLimit) {
Cand.RPDelta.Excess = PressureChange(SRI->getSGPRPressureSet());
Cand.RPDelta.Excess.setUnitInc(NewSGPRPressure - SGPRExcessLimit);
}
// Register pressure is considered 'CRITICAL' if it is approaching a value
// that would reduce the wave occupancy for the execution unit. When
// register pressure is 'CRITICAL', increading SGPR and VGPR pressure both
// has the same cost, so we don't need to prefer one over the other.
int SGPRDelta = NewSGPRPressure - SGPRCriticalLimit;
int VGPRDelta = NewVGPRPressure - VGPRCriticalLimit;
if (SGPRDelta >= 0 || VGPRDelta >= 0) {
if (SGPRDelta > VGPRDelta) {
Cand.RPDelta.CriticalMax = PressureChange(SRI->getSGPRPressureSet());
Cand.RPDelta.CriticalMax.setUnitInc(SGPRDelta);
} else {
Cand.RPDelta.CriticalMax = PressureChange(SRI->getVGPRPressureSet());
Cand.RPDelta.CriticalMax.setUnitInc(VGPRDelta);
}
}
}
// This function is mostly cut and pasted from
// GenericScheduler::pickNodeFromQueue()
void GCNMaxOccupancySchedStrategy::pickNodeFromQueue(SchedBoundary &Zone,
const CandPolicy &ZonePolicy,
const RegPressureTracker &RPTracker,
SchedCandidate &Cand) {
const SIRegisterInfo *SRI = static_cast<const SIRegisterInfo*>(TRI);
ArrayRef<unsigned> Pressure = RPTracker.getRegSetPressureAtPos();
unsigned SGPRPressure = Pressure[SRI->getSGPRPressureSet()];
unsigned VGPRPressure = Pressure[SRI->getVGPRPressureSet()];
ReadyQueue &Q = Zone.Available;
for (SUnit *SU : Q) {
SchedCandidate TryCand(ZonePolicy);
initCandidate(TryCand, SU, Zone.isTop(), RPTracker, SRI,
SGPRPressure, VGPRPressure);
// Pass SchedBoundary only when comparing nodes from the same boundary.
SchedBoundary *ZoneArg = Cand.AtTop == TryCand.AtTop ? &Zone : nullptr;
GenericScheduler::tryCandidate(Cand, TryCand, ZoneArg);
if (TryCand.Reason != NoCand) {
// Initialize resource delta if needed in case future heuristics query it.
if (TryCand.ResDelta == SchedResourceDelta())
TryCand.initResourceDelta(Zone.DAG, SchedModel);
Cand.setBest(TryCand);
}
}
}
// This function is mostly cut and pasted from
// GenericScheduler::pickNodeBidirectional()
SUnit *GCNMaxOccupancySchedStrategy::pickNodeBidirectional(bool &IsTopNode) {
// Schedule as far as possible in the direction of no choice. This is most
// efficient, but also provides the best heuristics for CriticalPSets.
if (SUnit *SU = Bot.pickOnlyChoice()) {
IsTopNode = false;
return SU;
}
if (SUnit *SU = Top.pickOnlyChoice()) {
IsTopNode = true;
return SU;
}
// Set the bottom-up policy based on the state of the current bottom zone and
// the instructions outside the zone, including the top zone.
CandPolicy BotPolicy;
setPolicy(BotPolicy, /*IsPostRA=*/false, Bot, &Top);
// Set the top-down policy based on the state of the current top zone and
// the instructions outside the zone, including the bottom zone.
CandPolicy TopPolicy;
setPolicy(TopPolicy, /*IsPostRA=*/false, Top, &Bot);
// See if BotCand is still valid (because we previously scheduled from Top).
LLVM_DEBUG(dbgs() << "Picking from Bot:\n");
if (!BotCand.isValid() || BotCand.SU->isScheduled ||
BotCand.Policy != BotPolicy) {
BotCand.reset(CandPolicy());
pickNodeFromQueue(Bot, BotPolicy, DAG->getBotRPTracker(), BotCand);
assert(BotCand.Reason != NoCand && "failed to find the first candidate");
} else {
LLVM_DEBUG(traceCandidate(BotCand));
}
// Check if the top Q has a better candidate.
LLVM_DEBUG(dbgs() << "Picking from Top:\n");
if (!TopCand.isValid() || TopCand.SU->isScheduled ||
TopCand.Policy != TopPolicy) {
TopCand.reset(CandPolicy());
pickNodeFromQueue(Top, TopPolicy, DAG->getTopRPTracker(), TopCand);
assert(TopCand.Reason != NoCand && "failed to find the first candidate");
} else {
LLVM_DEBUG(traceCandidate(TopCand));
}
// Pick best from BotCand and TopCand.
LLVM_DEBUG(dbgs() << "Top Cand: "; traceCandidate(TopCand);
dbgs() << "Bot Cand: "; traceCandidate(BotCand););
SchedCandidate Cand;
if (TopCand.Reason == BotCand.Reason) {
Cand = BotCand;
GenericSchedulerBase::CandReason TopReason = TopCand.Reason;
TopCand.Reason = NoCand;
GenericScheduler::tryCandidate(Cand, TopCand, nullptr);
if (TopCand.Reason != NoCand) {
Cand.setBest(TopCand);
} else {
TopCand.Reason = TopReason;
}
} else {
if (TopCand.Reason == RegExcess && TopCand.RPDelta.Excess.getUnitInc() <= 0) {
Cand = TopCand;
} else if (BotCand.Reason == RegExcess && BotCand.RPDelta.Excess.getUnitInc() <= 0) {
Cand = BotCand;
} else if (TopCand.Reason == RegCritical && TopCand.RPDelta.CriticalMax.getUnitInc() <= 0) {
Cand = TopCand;
} else if (BotCand.Reason == RegCritical && BotCand.RPDelta.CriticalMax.getUnitInc() <= 0) {
Cand = BotCand;
} else {
if (BotCand.Reason > TopCand.Reason) {
Cand = TopCand;
} else {
Cand = BotCand;
}
}
}
LLVM_DEBUG(dbgs() << "Picking: "; traceCandidate(Cand););
IsTopNode = Cand.AtTop;
return Cand.SU;
}
// This function is mostly cut and pasted from
// GenericScheduler::pickNode()
SUnit *GCNMaxOccupancySchedStrategy::pickNode(bool &IsTopNode) {
if (DAG->top() == DAG->bottom()) {
assert(Top.Available.empty() && Top.Pending.empty() &&
Bot.Available.empty() && Bot.Pending.empty() && "ReadyQ garbage");
return nullptr;
}
SUnit *SU;
do {
if (RegionPolicy.OnlyTopDown) {
SU = Top.pickOnlyChoice();
if (!SU) {
CandPolicy NoPolicy;
TopCand.reset(NoPolicy);
pickNodeFromQueue(Top, NoPolicy, DAG->getTopRPTracker(), TopCand);
assert(TopCand.Reason != NoCand && "failed to find a candidate");
SU = TopCand.SU;
}
IsTopNode = true;
} else if (RegionPolicy.OnlyBottomUp) {
SU = Bot.pickOnlyChoice();
if (!SU) {
CandPolicy NoPolicy;
BotCand.reset(NoPolicy);
pickNodeFromQueue(Bot, NoPolicy, DAG->getBotRPTracker(), BotCand);
assert(BotCand.Reason != NoCand && "failed to find a candidate");
SU = BotCand.SU;
}
IsTopNode = false;
} else {
SU = pickNodeBidirectional(IsTopNode);
}
} while (SU->isScheduled);
if (SU->isTopReady())
Top.removeReady(SU);
if (SU->isBottomReady())
Bot.removeReady(SU);
LLVM_DEBUG(dbgs() << "Scheduling SU(" << SU->NodeNum << ") "
<< *SU->getInstr());
return SU;
}
GCNScheduleDAGMILive::GCNScheduleDAGMILive(MachineSchedContext *C,
std::unique_ptr<MachineSchedStrategy> S) :
ScheduleDAGMILive(C, std::move(S)),
ST(MF.getSubtarget<SISubtarget>()),
MFI(*MF.getInfo<SIMachineFunctionInfo>()),
StartingOccupancy(MFI.getOccupancy()),
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
MinOccupancy(StartingOccupancy), Stage(0), RegionIdx(0) {
LLVM_DEBUG(dbgs() << "Starting occupancy is " << StartingOccupancy << ".\n");
}
void GCNScheduleDAGMILive::schedule() {
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
if (Stage == 0) {
// Just record regions at the first pass.
Regions.push_back(std::make_pair(RegionBegin, RegionEnd));
return;
}
std::vector<MachineInstr*> Unsched;
Unsched.reserve(NumRegionInstrs);
for (auto &I : *this) {
Unsched.push_back(&I);
}
GCNRegPressure PressureBefore;
if (LIS) {
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
PressureBefore = Pressure[RegionIdx];
LLVM_DEBUG(dbgs() << "Pressure before scheduling:\nRegion live-ins:";
GCNRPTracker::printLiveRegs(dbgs(), LiveIns[RegionIdx], MRI);
dbgs() << "Region live-in pressure: ";
llvm::getRegPressure(MRI, LiveIns[RegionIdx]).print(dbgs());
dbgs() << "Region register pressure: ";
PressureBefore.print(dbgs()));
}
ScheduleDAGMILive::schedule();
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
Regions[RegionIdx] = std::make_pair(RegionBegin, RegionEnd);
if (!LIS)
return;
// Check the results of scheduling.
GCNMaxOccupancySchedStrategy &S = (GCNMaxOccupancySchedStrategy&)*SchedImpl;
auto PressureAfter = getRealRegPressure();
LLVM_DEBUG(dbgs() << "Pressure after scheduling: ";
PressureAfter.print(dbgs()));
if (PressureAfter.getSGPRNum() <= S.SGPRCriticalLimit &&
PressureAfter.getVGPRNum() <= S.VGPRCriticalLimit) {
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
Pressure[RegionIdx] = PressureAfter;
LLVM_DEBUG(dbgs() << "Pressure in desired limits, done.\n");
return;
}
unsigned WavesAfter = getMaxWaves(PressureAfter.getSGPRNum(),
PressureAfter.getVGPRNum(), MF);
unsigned WavesBefore = getMaxWaves(PressureBefore.getSGPRNum(),
PressureBefore.getVGPRNum(), MF);
WavesAfter = std::min(WavesAfter, MFI.getMaxWavesPerEU());
WavesBefore = std::min(WavesBefore, MFI.getMaxWavesPerEU());
LLVM_DEBUG(dbgs() << "Occupancy before scheduling: " << WavesBefore
<< ", after " << WavesAfter << ".\n");
// We could not keep current target occupancy because of the just scheduled
// region. Record new occupancy for next scheduling cycle.
unsigned NewOccupancy = std::max(WavesAfter, WavesBefore);
// Allow memory bound functions to drop to 4 waves if not limited by an
// attribute.
if (WavesAfter < WavesBefore && WavesAfter < MinOccupancy &&
WavesAfter >= MFI.getMinAllowedOccupancy()) {
LLVM_DEBUG(dbgs() << "Function is memory bound, allow occupancy drop up to "
<< MFI.getMinAllowedOccupancy() << " waves\n");
NewOccupancy = WavesAfter;
}
if (NewOccupancy < MinOccupancy) {
MinOccupancy = NewOccupancy;
MFI.limitOccupancy(MinOccupancy);
LLVM_DEBUG(dbgs() << "Occupancy lowered for the function to "
<< MinOccupancy << ".\n");
}
if (WavesAfter >= MinOccupancy) {
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
Pressure[RegionIdx] = PressureAfter;
return;
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
}
LLVM_DEBUG(dbgs() << "Attempting to revert scheduling.\n");
RegionEnd = RegionBegin;
for (MachineInstr *MI : Unsched) {
if (MI->isDebugInstr())
continue;
if (MI->getIterator() != RegionEnd) {
BB->remove(MI);
BB->insert(RegionEnd, MI);
if (!MI->isDebugInstr())
LIS->handleMove(*MI, true);
}
// 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, false);
if (!MI->isDebugInstr()) {
if (ShouldTrackLaneMasks) {
// Adjust liveness and add missing dead+read-undef flags.
SlotIndex SlotIdx = LIS->getInstructionIndex(*MI).getRegSlot();
RegOpers.adjustLaneLiveness(*LIS, MRI, SlotIdx, MI);
} else {
// Adjust for missing dead-def flags.
RegOpers.detectDeadDefs(*MI, *LIS);
}
}
RegionEnd = MI->getIterator();
++RegionEnd;
LLVM_DEBUG(dbgs() << "Scheduling " << *MI);
}
RegionBegin = Unsched.front()->getIterator();
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
Regions[RegionIdx] = std::make_pair(RegionBegin, RegionEnd);
placeDebugValues();
}
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
GCNRegPressure GCNScheduleDAGMILive::getRealRegPressure() const {
GCNDownwardRPTracker RPTracker(*LIS);
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
RPTracker.advance(begin(), end(), &LiveIns[RegionIdx]);
return RPTracker.moveMaxPressure();
}
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
void GCNScheduleDAGMILive::computeBlockPressure(const MachineBasicBlock *MBB) {
GCNDownwardRPTracker RPTracker(*LIS);
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
// If the block has the only successor then live-ins of that successor are
// live-outs of the current block. We can reuse calculated live set if the
// successor will be sent to scheduling past current block.
const MachineBasicBlock *OnlySucc = nullptr;
if (MBB->succ_size() == 1 && !(*MBB->succ_begin())->empty()) {
SlotIndexes *Ind = LIS->getSlotIndexes();
if (Ind->getMBBStartIdx(MBB) < Ind->getMBBStartIdx(*MBB->succ_begin()))
OnlySucc = *MBB->succ_begin();
}
// Scheduler sends regions from the end of the block upwards.
size_t CurRegion = RegionIdx;
for (size_t E = Regions.size(); CurRegion != E; ++CurRegion)
if (Regions[CurRegion].first->getParent() != MBB)
break;
--CurRegion;
auto I = MBB->begin();
auto LiveInIt = MBBLiveIns.find(MBB);
if (LiveInIt != MBBLiveIns.end()) {
auto LiveIn = std::move(LiveInIt->second);
RPTracker.reset(*MBB->begin(), &LiveIn);
MBBLiveIns.erase(LiveInIt);
} else {
I = Regions[CurRegion].first;
RPTracker.reset(*I);
}
for ( ; ; ) {
I = RPTracker.getNext();
if (Regions[CurRegion].first == I) {
LiveIns[CurRegion] = RPTracker.getLiveRegs();
RPTracker.clearMaxPressure();
}
if (Regions[CurRegion].second == I) {
Pressure[CurRegion] = RPTracker.moveMaxPressure();
if (CurRegion-- == RegionIdx)
break;
}
RPTracker.advanceToNext();
RPTracker.advanceBeforeNext();
}
if (OnlySucc) {
if (I != MBB->end()) {
RPTracker.advanceToNext();
RPTracker.advance(MBB->end());
}
RPTracker.reset(*OnlySucc->begin(), &RPTracker.getLiveRegs());
RPTracker.advanceBeforeNext();
MBBLiveIns[OnlySucc] = RPTracker.moveLiveRegs();
}
}
void GCNScheduleDAGMILive::finalizeSchedule() {
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
GCNMaxOccupancySchedStrategy &S = (GCNMaxOccupancySchedStrategy&)*SchedImpl;
LLVM_DEBUG(dbgs() << "All regions recorded, starting actual scheduling.\n");
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
LiveIns.resize(Regions.size());
Pressure.resize(Regions.size());
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
do {
Stage++;
RegionIdx = 0;
MachineBasicBlock *MBB = nullptr;
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
if (Stage > 1) {
// Retry function scheduling if we found resulting occupancy and it is
// lower than used for first pass scheduling. This will give more freedom
// to schedule low register pressure blocks.
// Code is partially copied from MachineSchedulerBase::scheduleRegions().
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
if (!LIS || StartingOccupancy <= MinOccupancy)
break;
LLVM_DEBUG(
dbgs()
<< "Retrying function scheduling with lowest recorded occupancy "
<< MinOccupancy << ".\n");
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
S.setTargetOccupancy(MinOccupancy);
}
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
for (auto Region : Regions) {
RegionBegin = Region.first;
RegionEnd = Region.second;
if (RegionBegin->getParent() != MBB) {
if (MBB) finishBlock();
MBB = RegionBegin->getParent();
startBlock(MBB);
if (Stage == 1)
computeBlockPressure(MBB);
}
unsigned NumRegionInstrs = std::distance(begin(), end());
enterRegion(MBB, begin(), end(), NumRegionInstrs);
// Skip empty scheduling regions (0 or 1 schedulable instructions).
if (begin() == end() || begin() == std::prev(end())) {
exitRegion();
continue;
}
LLVM_DEBUG(dbgs() << "********** MI Scheduling **********\n");
LLVM_DEBUG(dbgs() << MF.getName() << ":" << printMBBReference(*MBB) << " "
<< MBB->getName() << "\n From: " << *begin()
<< " To: ";
if (RegionEnd != MBB->end()) dbgs() << *RegionEnd;
else dbgs() << "End";
dbgs() << " RegionInstrs: " << NumRegionInstrs << '\n');
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
schedule();
exitRegion();
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
++RegionIdx;
}
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
finishBlock();
[AMDGPU] Cache live-ins and register pressure in scheduler Using LIS can be quite expensive, so caching of calculated region live-ins and pressure is implemented. It does two things: 1. Caches the info for the second stage when we schedule with decreased target occupancy. 2. Tracks the basic block from top to bottom thus eliminating the need to scan whole register file liveness at every region split in the middle of the block. The scheduling is now done in 3 stages instead of two, with the first one being really a no-op and only used to collect scheduling regions as sent by the scheduler driver. There is no functional change to the current behavior, only compilation speed is affected. In general computeBlockPressure() could be simplified if we switch to backward RP tracker, because scheduler sends regions within a block starting from the last upward. We could use a natural order of upward tracker to seamlessly change between regions of the same block, since live reg set of a previous tracked region would become a live-out of the next region. That however requires fixing upward tracker to properly account defs and uses of the same instruction as both are contributing to the current pressure. When we converge on the produced pressure we should be able to switch between them back and forth. In addition, backward tracker is less expensive as it uses LIS in recede less often than forward uses it in advance. At the moment the worst known case compilation time has improved from 26 minutes to 8.5. Differential Revision: https://reviews.llvm.org/D33117 llvm-svn: 303184
2017-05-17 00:11:26 +08:00
} while (Stage < 2);
}