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

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//===- RegisterPressure.cpp - Dynamic Register Pressure -------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the RegisterPressure class which can be used to track
// MachineInstr level register pressure.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/RegisterPressure.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/LiveIntervals.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBundle.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/MC/LaneBitmask.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <iterator>
#include <limits>
#include <utility>
#include <vector>
using namespace llvm;
/// Increase pressure for each pressure set provided by TargetRegisterInfo.
static void increaseSetPressure(std::vector<unsigned> &CurrSetPressure,
const MachineRegisterInfo &MRI, unsigned Reg,
LaneBitmask PrevMask, LaneBitmask NewMask) {
assert((PrevMask & ~NewMask).none() && "Must not remove bits");
if (PrevMask.any() || NewMask.none())
return;
PSetIterator PSetI = MRI.getPressureSets(Reg);
unsigned Weight = PSetI.getWeight();
for (; PSetI.isValid(); ++PSetI)
CurrSetPressure[*PSetI] += Weight;
}
/// Decrease pressure for each pressure set provided by TargetRegisterInfo.
static void decreaseSetPressure(std::vector<unsigned> &CurrSetPressure,
const MachineRegisterInfo &MRI, unsigned Reg,
LaneBitmask PrevMask, LaneBitmask NewMask) {
//assert((NewMask & !PrevMask) == 0 && "Must not add bits");
if (NewMask.any() || PrevMask.none())
return;
PSetIterator PSetI = MRI.getPressureSets(Reg);
unsigned Weight = PSetI.getWeight();
for (; PSetI.isValid(); ++PSetI) {
assert(CurrSetPressure[*PSetI] >= Weight && "register pressure underflow");
CurrSetPressure[*PSetI] -= Weight;
}
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD
void llvm::dumpRegSetPressure(ArrayRef<unsigned> SetPressure,
const TargetRegisterInfo *TRI) {
bool Empty = true;
for (unsigned i = 0, e = SetPressure.size(); i < e; ++i) {
if (SetPressure[i] != 0) {
dbgs() << TRI->getRegPressureSetName(i) << "=" << SetPressure[i] << '\n';
Empty = false;
}
}
if (Empty)
dbgs() << "\n";
}
LLVM_DUMP_METHOD
void RegisterPressure::dump(const TargetRegisterInfo *TRI) const {
dbgs() << "Max Pressure: ";
dumpRegSetPressure(MaxSetPressure, TRI);
dbgs() << "Live In: ";
for (const RegisterMaskPair &P : LiveInRegs) {
dbgs() << printVRegOrUnit(P.RegUnit, TRI);
if (!P.LaneMask.all())
dbgs() << ':' << PrintLaneMask(P.LaneMask);
dbgs() << ' ';
}
dbgs() << '\n';
dbgs() << "Live Out: ";
for (const RegisterMaskPair &P : LiveOutRegs) {
dbgs() << printVRegOrUnit(P.RegUnit, TRI);
if (!P.LaneMask.all())
dbgs() << ':' << PrintLaneMask(P.LaneMask);
dbgs() << ' ';
}
dbgs() << '\n';
}
LLVM_DUMP_METHOD
void RegPressureTracker::dump() const {
if (!isTopClosed() || !isBottomClosed()) {
dbgs() << "Curr Pressure: ";
dumpRegSetPressure(CurrSetPressure, TRI);
}
P.dump(TRI);
}
LLVM_DUMP_METHOD
void PressureDiff::dump(const TargetRegisterInfo &TRI) const {
const char *sep = "";
for (const PressureChange &Change : *this) {
if (!Change.isValid())
break;
dbgs() << sep << TRI.getRegPressureSetName(Change.getPSet())
<< " " << Change.getUnitInc();
sep = " ";
}
dbgs() << '\n';
}
#endif
void RegPressureTracker::increaseRegPressure(unsigned RegUnit,
LaneBitmask PreviousMask,
LaneBitmask NewMask) {
if (PreviousMask.any() || NewMask.none())
return;
PSetIterator PSetI = MRI->getPressureSets(RegUnit);
unsigned Weight = PSetI.getWeight();
for (; PSetI.isValid(); ++PSetI) {
CurrSetPressure[*PSetI] += Weight;
P.MaxSetPressure[*PSetI] =
std::max(P.MaxSetPressure[*PSetI], CurrSetPressure[*PSetI]);
}
}
void RegPressureTracker::decreaseRegPressure(unsigned RegUnit,
LaneBitmask PreviousMask,
LaneBitmask NewMask) {
decreaseSetPressure(CurrSetPressure, *MRI, RegUnit, PreviousMask, NewMask);
}
/// Clear the result so it can be used for another round of pressure tracking.
void IntervalPressure::reset() {
TopIdx = BottomIdx = SlotIndex();
MaxSetPressure.clear();
LiveInRegs.clear();
LiveOutRegs.clear();
}
/// Clear the result so it can be used for another round of pressure tracking.
void RegionPressure::reset() {
TopPos = BottomPos = MachineBasicBlock::const_iterator();
MaxSetPressure.clear();
LiveInRegs.clear();
LiveOutRegs.clear();
}
/// If the current top is not less than or equal to the next index, open it.
/// We happen to need the SlotIndex for the next top for pressure update.
void IntervalPressure::openTop(SlotIndex NextTop) {
if (TopIdx <= NextTop)
return;
TopIdx = SlotIndex();
LiveInRegs.clear();
}
/// If the current top is the previous instruction (before receding), open it.
void RegionPressure::openTop(MachineBasicBlock::const_iterator PrevTop) {
if (TopPos != PrevTop)
return;
TopPos = MachineBasicBlock::const_iterator();
LiveInRegs.clear();
}
/// If the current bottom is not greater than the previous index, open it.
void IntervalPressure::openBottom(SlotIndex PrevBottom) {
if (BottomIdx > PrevBottom)
return;
BottomIdx = SlotIndex();
LiveInRegs.clear();
}
/// If the current bottom is the previous instr (before advancing), open it.
void RegionPressure::openBottom(MachineBasicBlock::const_iterator PrevBottom) {
if (BottomPos != PrevBottom)
return;
BottomPos = MachineBasicBlock::const_iterator();
LiveInRegs.clear();
}
void LiveRegSet::init(const MachineRegisterInfo &MRI) {
const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
unsigned NumRegUnits = TRI.getNumRegs();
unsigned NumVirtRegs = MRI.getNumVirtRegs();
Regs.setUniverse(NumRegUnits + NumVirtRegs);
this->NumRegUnits = NumRegUnits;
}
void LiveRegSet::clear() {
Regs.clear();
}
static const LiveRange *getLiveRange(const LiveIntervals &LIS, unsigned Reg) {
if (Register::isVirtualRegister(Reg))
return &LIS.getInterval(Reg);
return LIS.getCachedRegUnit(Reg);
}
void RegPressureTracker::reset() {
MBB = nullptr;
LIS = nullptr;
CurrSetPressure.clear();
LiveThruPressure.clear();
P.MaxSetPressure.clear();
if (RequireIntervals)
static_cast<IntervalPressure&>(P).reset();
else
static_cast<RegionPressure&>(P).reset();
LiveRegs.clear();
UntiedDefs.clear();
}
/// Setup the RegPressureTracker.
///
/// TODO: Add support for pressure without LiveIntervals.
void RegPressureTracker::init(const MachineFunction *mf,
const RegisterClassInfo *rci,
const LiveIntervals *lis,
const MachineBasicBlock *mbb,
MachineBasicBlock::const_iterator pos,
bool TrackLaneMasks, bool TrackUntiedDefs) {
reset();
MF = mf;
TRI = MF->getSubtarget().getRegisterInfo();
RCI = rci;
MRI = &MF->getRegInfo();
MBB = mbb;
this->TrackUntiedDefs = TrackUntiedDefs;
this->TrackLaneMasks = TrackLaneMasks;
if (RequireIntervals) {
assert(lis && "IntervalPressure requires LiveIntervals");
LIS = lis;
}
CurrPos = pos;
CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
P.MaxSetPressure = CurrSetPressure;
LiveRegs.init(*MRI);
if (TrackUntiedDefs)
UntiedDefs.setUniverse(MRI->getNumVirtRegs());
}
/// Does this pressure result have a valid top position and live ins.
bool RegPressureTracker::isTopClosed() const {
if (RequireIntervals)
return static_cast<IntervalPressure&>(P).TopIdx.isValid();
return (static_cast<RegionPressure&>(P).TopPos ==
MachineBasicBlock::const_iterator());
}
/// Does this pressure result have a valid bottom position and live outs.
bool RegPressureTracker::isBottomClosed() const {
if (RequireIntervals)
return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
return (static_cast<RegionPressure&>(P).BottomPos ==
MachineBasicBlock::const_iterator());
}
SlotIndex RegPressureTracker::getCurrSlot() const {
MachineBasicBlock::const_iterator IdxPos =
skipDebugInstructionsForward(CurrPos, MBB->end());
if (IdxPos == MBB->end())
return LIS->getMBBEndIdx(MBB);
return LIS->getInstructionIndex(*IdxPos).getRegSlot();
}
/// Set the boundary for the top of the region and summarize live ins.
void RegPressureTracker::closeTop() {
if (RequireIntervals)
static_cast<IntervalPressure&>(P).TopIdx = getCurrSlot();
else
static_cast<RegionPressure&>(P).TopPos = CurrPos;
assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
P.LiveInRegs.reserve(LiveRegs.size());
LiveRegs.appendTo(P.LiveInRegs);
}
/// Set the boundary for the bottom of the region and summarize live outs.
void RegPressureTracker::closeBottom() {
if (RequireIntervals)
static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
else
static_cast<RegionPressure&>(P).BottomPos = CurrPos;
assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
P.LiveOutRegs.reserve(LiveRegs.size());
LiveRegs.appendTo(P.LiveOutRegs);
}
/// Finalize the region boundaries and record live ins and live outs.
void RegPressureTracker::closeRegion() {
if (!isTopClosed() && !isBottomClosed()) {
assert(LiveRegs.size() == 0 && "no region boundary");
return;
}
if (!isBottomClosed())
closeBottom();
else if (!isTopClosed())
closeTop();
// If both top and bottom are closed, do nothing.
}
/// The register tracker is unaware of global liveness so ignores normal
/// live-thru ranges. However, two-address or coalesced chains can also lead
/// to live ranges with no holes. Count these to inform heuristics that we
/// can never drop below this pressure.
void RegPressureTracker::initLiveThru(const RegPressureTracker &RPTracker) {
LiveThruPressure.assign(TRI->getNumRegPressureSets(), 0);
assert(isBottomClosed() && "need bottom-up tracking to intialize.");
for (const RegisterMaskPair &Pair : P.LiveOutRegs) {
unsigned RegUnit = Pair.RegUnit;
if (Register::isVirtualRegister(RegUnit)
&& !RPTracker.hasUntiedDef(RegUnit))
increaseSetPressure(LiveThruPressure, *MRI, RegUnit,
LaneBitmask::getNone(), Pair.LaneMask);
}
}
static LaneBitmask getRegLanes(ArrayRef<RegisterMaskPair> RegUnits,
unsigned RegUnit) {
auto I = llvm::find_if(RegUnits, [RegUnit](const RegisterMaskPair Other) {
return Other.RegUnit == RegUnit;
});
if (I == RegUnits.end())
return LaneBitmask::getNone();
return I->LaneMask;
}
static void addRegLanes(SmallVectorImpl<RegisterMaskPair> &RegUnits,
RegisterMaskPair Pair) {
unsigned RegUnit = Pair.RegUnit;
assert(Pair.LaneMask.any());
auto I = llvm::find_if(RegUnits, [RegUnit](const RegisterMaskPair Other) {
return Other.RegUnit == RegUnit;
});
if (I == RegUnits.end()) {
RegUnits.push_back(Pair);
} else {
I->LaneMask |= Pair.LaneMask;
}
}
static void setRegZero(SmallVectorImpl<RegisterMaskPair> &RegUnits,
unsigned RegUnit) {
auto I = llvm::find_if(RegUnits, [RegUnit](const RegisterMaskPair Other) {
return Other.RegUnit == RegUnit;
});
if (I == RegUnits.end()) {
RegUnits.push_back(RegisterMaskPair(RegUnit, LaneBitmask::getNone()));
} else {
I->LaneMask = LaneBitmask::getNone();
}
}
static void removeRegLanes(SmallVectorImpl<RegisterMaskPair> &RegUnits,
RegisterMaskPair Pair) {
unsigned RegUnit = Pair.RegUnit;
assert(Pair.LaneMask.any());
auto I = llvm::find_if(RegUnits, [RegUnit](const RegisterMaskPair Other) {
return Other.RegUnit == RegUnit;
});
if (I != RegUnits.end()) {
I->LaneMask &= ~Pair.LaneMask;
if (I->LaneMask.none())
RegUnits.erase(I);
}
}
static LaneBitmask getLanesWithProperty(const LiveIntervals &LIS,
const MachineRegisterInfo &MRI, bool TrackLaneMasks, unsigned RegUnit,
SlotIndex Pos, LaneBitmask SafeDefault,
bool(*Property)(const LiveRange &LR, SlotIndex Pos)) {
if (Register::isVirtualRegister(RegUnit)) {
const LiveInterval &LI = LIS.getInterval(RegUnit);
LaneBitmask Result;
if (TrackLaneMasks && LI.hasSubRanges()) {
for (const LiveInterval::SubRange &SR : LI.subranges()) {
if (Property(SR, Pos))
Result |= SR.LaneMask;
}
} else if (Property(LI, Pos)) {
Result = TrackLaneMasks ? MRI.getMaxLaneMaskForVReg(RegUnit)
: LaneBitmask::getAll();
}
return Result;
} else {
const LiveRange *LR = LIS.getCachedRegUnit(RegUnit);
// Be prepared for missing liveranges: We usually do not compute liveranges
// for physical registers on targets with many registers (GPUs).
if (LR == nullptr)
return SafeDefault;
return Property(*LR, Pos) ? LaneBitmask::getAll() : LaneBitmask::getNone();
}
}
static LaneBitmask getLiveLanesAt(const LiveIntervals &LIS,
const MachineRegisterInfo &MRI,
bool TrackLaneMasks, unsigned RegUnit,
SlotIndex Pos) {
return getLanesWithProperty(LIS, MRI, TrackLaneMasks, RegUnit, Pos,
LaneBitmask::getAll(),
[](const LiveRange &LR, SlotIndex Pos) {
return LR.liveAt(Pos);
});
}
namespace {
/// Collect this instruction's unique uses and defs into SmallVectors for
/// processing defs and uses in order.
///
/// FIXME: always ignore tied opers
class RegisterOperandsCollector {
friend class llvm::RegisterOperands;
RegisterOperands &RegOpers;
const TargetRegisterInfo &TRI;
const MachineRegisterInfo &MRI;
bool IgnoreDead;
RegisterOperandsCollector(RegisterOperands &RegOpers,
const TargetRegisterInfo &TRI,
const MachineRegisterInfo &MRI, bool IgnoreDead)
: RegOpers(RegOpers), TRI(TRI), MRI(MRI), IgnoreDead(IgnoreDead) {}
void collectInstr(const MachineInstr &MI) const {
for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
collectOperand(*OperI);
// Remove redundant physreg dead defs.
for (const RegisterMaskPair &P : RegOpers.Defs)
removeRegLanes(RegOpers.DeadDefs, P);
}
void collectInstrLanes(const MachineInstr &MI) const {
for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
collectOperandLanes(*OperI);
// Remove redundant physreg dead defs.
for (const RegisterMaskPair &P : RegOpers.Defs)
removeRegLanes(RegOpers.DeadDefs, P);
}
/// Push this operand's register onto the correct vectors.
void collectOperand(const MachineOperand &MO) const {
if (!MO.isReg() || !MO.getReg())
return;
unsigned Reg = MO.getReg();
if (MO.isUse()) {
if (!MO.isUndef() && !MO.isInternalRead())
pushReg(Reg, RegOpers.Uses);
} else {
assert(MO.isDef());
// Subregister definitions may imply a register read.
if (MO.readsReg())
pushReg(Reg, RegOpers.Uses);
if (MO.isDead()) {
if (!IgnoreDead)
pushReg(Reg, RegOpers.DeadDefs);
} else
pushReg(Reg, RegOpers.Defs);
}
}
void pushReg(unsigned Reg,
SmallVectorImpl<RegisterMaskPair> &RegUnits) const {
if (Register::isVirtualRegister(Reg)) {
addRegLanes(RegUnits, RegisterMaskPair(Reg, LaneBitmask::getAll()));
} else if (MRI.isAllocatable(Reg)) {
for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units)
addRegLanes(RegUnits, RegisterMaskPair(*Units, LaneBitmask::getAll()));
}
}
void collectOperandLanes(const MachineOperand &MO) const {
if (!MO.isReg() || !MO.getReg())
return;
unsigned Reg = MO.getReg();
unsigned SubRegIdx = MO.getSubReg();
if (MO.isUse()) {
if (!MO.isUndef() && !MO.isInternalRead())
pushRegLanes(Reg, SubRegIdx, RegOpers.Uses);
} else {
assert(MO.isDef());
// Treat read-undef subreg defs as definitions of the whole register.
if (MO.isUndef())
SubRegIdx = 0;
if (MO.isDead()) {
if (!IgnoreDead)
pushRegLanes(Reg, SubRegIdx, RegOpers.DeadDefs);
} else
pushRegLanes(Reg, SubRegIdx, RegOpers.Defs);
}
}
void pushRegLanes(unsigned Reg, unsigned SubRegIdx,
SmallVectorImpl<RegisterMaskPair> &RegUnits) const {
if (Register::isVirtualRegister(Reg)) {
LaneBitmask LaneMask = SubRegIdx != 0
? TRI.getSubRegIndexLaneMask(SubRegIdx)
: MRI.getMaxLaneMaskForVReg(Reg);
addRegLanes(RegUnits, RegisterMaskPair(Reg, LaneMask));
} else if (MRI.isAllocatable(Reg)) {
for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units)
addRegLanes(RegUnits, RegisterMaskPair(*Units, LaneBitmask::getAll()));
}
}
};
} // end anonymous namespace
void RegisterOperands::collect(const MachineInstr &MI,
const TargetRegisterInfo &TRI,
const MachineRegisterInfo &MRI,
bool TrackLaneMasks, bool IgnoreDead) {
RegisterOperandsCollector Collector(*this, TRI, MRI, IgnoreDead);
if (TrackLaneMasks)
Collector.collectInstrLanes(MI);
else
Collector.collectInstr(MI);
}
void RegisterOperands::detectDeadDefs(const MachineInstr &MI,
const LiveIntervals &LIS) {
SlotIndex SlotIdx = LIS.getInstructionIndex(MI);
for (auto RI = Defs.begin(); RI != Defs.end(); /*empty*/) {
unsigned Reg = RI->RegUnit;
const LiveRange *LR = getLiveRange(LIS, Reg);
if (LR != nullptr) {
LiveQueryResult LRQ = LR->Query(SlotIdx);
if (LRQ.isDeadDef()) {
// LiveIntervals knows this is a dead even though it's MachineOperand is
// not flagged as such.
DeadDefs.push_back(*RI);
RI = Defs.erase(RI);
continue;
}
}
++RI;
}
}
void RegisterOperands::adjustLaneLiveness(const LiveIntervals &LIS,
const MachineRegisterInfo &MRI,
SlotIndex Pos,
MachineInstr *AddFlagsMI) {
for (auto I = Defs.begin(); I != Defs.end(); ) {
LaneBitmask LiveAfter = getLiveLanesAt(LIS, MRI, true, I->RegUnit,
Pos.getDeadSlot());
// If the def is all that is live after the instruction, then in case
// of a subregister def we need a read-undef flag.
unsigned RegUnit = I->RegUnit;
if (Register::isVirtualRegister(RegUnit) &&
AddFlagsMI != nullptr && (LiveAfter & ~I->LaneMask).none())
AddFlagsMI->setRegisterDefReadUndef(RegUnit);
LaneBitmask ActualDef = I->LaneMask & LiveAfter;
if (ActualDef.none()) {
I = Defs.erase(I);
} else {
I->LaneMask = ActualDef;
++I;
}
}
for (auto I = Uses.begin(); I != Uses.end(); ) {
LaneBitmask LiveBefore = getLiveLanesAt(LIS, MRI, true, I->RegUnit,
Pos.getBaseIndex());
LaneBitmask LaneMask = I->LaneMask & LiveBefore;
if (LaneMask.none()) {
I = Uses.erase(I);
} else {
I->LaneMask = LaneMask;
++I;
}
}
if (AddFlagsMI != nullptr) {
for (const RegisterMaskPair &P : DeadDefs) {
unsigned RegUnit = P.RegUnit;
if (!Register::isVirtualRegister(RegUnit))
continue;
LaneBitmask LiveAfter = getLiveLanesAt(LIS, MRI, true, RegUnit,
Pos.getDeadSlot());
if (LiveAfter.none())
AddFlagsMI->setRegisterDefReadUndef(RegUnit);
}
}
}
/// Initialize an array of N PressureDiffs.
void PressureDiffs::init(unsigned N) {
Size = N;
if (N <= Max) {
memset(PDiffArray, 0, N * sizeof(PressureDiff));
return;
}
Max = Size;
free(PDiffArray);
PDiffArray = static_cast<PressureDiff*>(safe_calloc(N, sizeof(PressureDiff)));
}
void PressureDiffs::addInstruction(unsigned Idx,
const RegisterOperands &RegOpers,
const MachineRegisterInfo &MRI) {
PressureDiff &PDiff = (*this)[Idx];
assert(!PDiff.begin()->isValid() && "stale PDiff");
for (const RegisterMaskPair &P : RegOpers.Defs)
PDiff.addPressureChange(P.RegUnit, true, &MRI);
for (const RegisterMaskPair &P : RegOpers.Uses)
PDiff.addPressureChange(P.RegUnit, false, &MRI);
}
/// Add a change in pressure to the pressure diff of a given instruction.
void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
const MachineRegisterInfo *MRI) {
PSetIterator PSetI = MRI->getPressureSets(RegUnit);
int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
for (; PSetI.isValid(); ++PSetI) {
// Find an existing entry in the pressure diff for this PSet.
PressureDiff::iterator I = nonconst_begin(), E = nonconst_end();
for (; I != E && I->isValid(); ++I) {
if (I->getPSet() >= *PSetI)
break;
}
// If all pressure sets are more constrained, skip the remaining PSets.
if (I == E)
break;
// Insert this PressureChange.
if (!I->isValid() || I->getPSet() != *PSetI) {
PressureChange PTmp = PressureChange(*PSetI);
for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
std::swap(*J, PTmp);
}
// Update the units for this pressure set.
unsigned NewUnitInc = I->getUnitInc() + Weight;
if (NewUnitInc != 0) {
I->setUnitInc(NewUnitInc);
} else {
// Remove entry
PressureDiff::iterator J;
for (J = std::next(I); J != E && J->isValid(); ++J, ++I)
*I = *J;
*I = PressureChange();
}
}
}
/// Force liveness of registers.
void RegPressureTracker::addLiveRegs(ArrayRef<RegisterMaskPair> Regs) {
for (const RegisterMaskPair &P : Regs) {
LaneBitmask PrevMask = LiveRegs.insert(P);
LaneBitmask NewMask = PrevMask | P.LaneMask;
increaseRegPressure(P.RegUnit, PrevMask, NewMask);
}
}
void RegPressureTracker::discoverLiveInOrOut(RegisterMaskPair Pair,
SmallVectorImpl<RegisterMaskPair> &LiveInOrOut) {
assert(Pair.LaneMask.any());
unsigned RegUnit = Pair.RegUnit;
auto I = llvm::find_if(LiveInOrOut, [RegUnit](const RegisterMaskPair &Other) {
return Other.RegUnit == RegUnit;
});
LaneBitmask PrevMask;
LaneBitmask NewMask;
if (I == LiveInOrOut.end()) {
PrevMask = LaneBitmask::getNone();
NewMask = Pair.LaneMask;
LiveInOrOut.push_back(Pair);
} else {
PrevMask = I->LaneMask;
NewMask = PrevMask | Pair.LaneMask;
I->LaneMask = NewMask;
}
increaseSetPressure(P.MaxSetPressure, *MRI, RegUnit, PrevMask, NewMask);
}
void RegPressureTracker::discoverLiveIn(RegisterMaskPair Pair) {
discoverLiveInOrOut(Pair, P.LiveInRegs);
}
void RegPressureTracker::discoverLiveOut(RegisterMaskPair Pair) {
discoverLiveInOrOut(Pair, P.LiveOutRegs);
}
void RegPressureTracker::bumpDeadDefs(ArrayRef<RegisterMaskPair> DeadDefs) {
for (const RegisterMaskPair &P : DeadDefs) {
unsigned Reg = P.RegUnit;
LaneBitmask LiveMask = LiveRegs.contains(Reg);
LaneBitmask BumpedMask = LiveMask | P.LaneMask;
increaseRegPressure(Reg, LiveMask, BumpedMask);
}
for (const RegisterMaskPair &P : DeadDefs) {
unsigned Reg = P.RegUnit;
LaneBitmask LiveMask = LiveRegs.contains(Reg);
LaneBitmask BumpedMask = LiveMask | P.LaneMask;
decreaseRegPressure(Reg, BumpedMask, LiveMask);
}
}
/// Recede across the previous instruction. If LiveUses is provided, record any
/// RegUnits that are made live by the current instruction's uses. This includes
/// registers that are both defined and used by the instruction. If a pressure
/// difference pointer is provided record the changes is pressure caused by this
/// instruction independent of liveness.
void RegPressureTracker::recede(const RegisterOperands &RegOpers,
SmallVectorImpl<RegisterMaskPair> *LiveUses) {
assert(!CurrPos->isDebugInstr());
// Boost pressure for all dead defs together.
bumpDeadDefs(RegOpers.DeadDefs);
// Kill liveness at live defs.
// TODO: consider earlyclobbers?
for (const RegisterMaskPair &Def : RegOpers.Defs) {
unsigned Reg = Def.RegUnit;
LaneBitmask PreviousMask = LiveRegs.erase(Def);
LaneBitmask NewMask = PreviousMask & ~Def.LaneMask;
LaneBitmask LiveOut = Def.LaneMask & ~PreviousMask;
if (LiveOut.any()) {
discoverLiveOut(RegisterMaskPair(Reg, LiveOut));
// Retroactively model effects on pressure of the live out lanes.
increaseSetPressure(CurrSetPressure, *MRI, Reg, LaneBitmask::getNone(),
LiveOut);
PreviousMask = LiveOut;
}
if (NewMask.none()) {
// Add a 0 entry to LiveUses as a marker that the complete vreg has become
// dead.
if (TrackLaneMasks && LiveUses != nullptr)
setRegZero(*LiveUses, Reg);
}
decreaseRegPressure(Reg, PreviousMask, NewMask);
}
SlotIndex SlotIdx;
if (RequireIntervals)
SlotIdx = LIS->getInstructionIndex(*CurrPos).getRegSlot();
// Generate liveness for uses.
for (const RegisterMaskPair &Use : RegOpers.Uses) {
unsigned Reg = Use.RegUnit;
assert(Use.LaneMask.any());
LaneBitmask PreviousMask = LiveRegs.insert(Use);
LaneBitmask NewMask = PreviousMask | Use.LaneMask;
if (NewMask == PreviousMask)
continue;
// Did the register just become live?
if (PreviousMask.none()) {
if (LiveUses != nullptr) {
if (!TrackLaneMasks) {
addRegLanes(*LiveUses, RegisterMaskPair(Reg, NewMask));
} else {
auto I =
llvm::find_if(*LiveUses, [Reg](const RegisterMaskPair Other) {
return Other.RegUnit == Reg;
});
bool IsRedef = I != LiveUses->end();
if (IsRedef) {
// ignore re-defs here...
assert(I->LaneMask.none());
removeRegLanes(*LiveUses, RegisterMaskPair(Reg, NewMask));
} else {
addRegLanes(*LiveUses, RegisterMaskPair(Reg, NewMask));
}
}
}
// Discover live outs if this may be the first occurance of this register.
if (RequireIntervals) {
LaneBitmask LiveOut = getLiveThroughAt(Reg, SlotIdx);
if (LiveOut.any())
discoverLiveOut(RegisterMaskPair(Reg, LiveOut));
}
}
increaseRegPressure(Reg, PreviousMask, NewMask);
}
if (TrackUntiedDefs) {
for (const RegisterMaskPair &Def : RegOpers.Defs) {
unsigned RegUnit = Def.RegUnit;
if (Register::isVirtualRegister(RegUnit) &&
(LiveRegs.contains(RegUnit) & Def.LaneMask).none())
UntiedDefs.insert(RegUnit);
}
}
}
void RegPressureTracker::recedeSkipDebugValues() {
assert(CurrPos != MBB->begin());
if (!isBottomClosed())
closeBottom();
// Open the top of the region using block iterators.
if (!RequireIntervals && isTopClosed())
static_cast<RegionPressure&>(P).openTop(CurrPos);
// Find the previous instruction.
CurrPos = skipDebugInstructionsBackward(std::prev(CurrPos), MBB->begin());
SlotIndex SlotIdx;
if (RequireIntervals && !CurrPos->isDebugInstr())
SlotIdx = LIS->getInstructionIndex(*CurrPos).getRegSlot();
// Open the top of the region using slot indexes.
if (RequireIntervals && isTopClosed())
static_cast<IntervalPressure&>(P).openTop(SlotIdx);
}
void RegPressureTracker::recede(SmallVectorImpl<RegisterMaskPair> *LiveUses) {
recedeSkipDebugValues();
if (CurrPos->isDebugValue()) {
// It's possible to only have debug_value instructions and hit the start of
// the block.
assert(CurrPos == MBB->begin());
return;
}
const MachineInstr &MI = *CurrPos;
RegisterOperands RegOpers;
RegOpers.collect(MI, *TRI, *MRI, TrackLaneMasks, false);
if (TrackLaneMasks) {
SlotIndex SlotIdx = LIS->getInstructionIndex(*CurrPos).getRegSlot();
RegOpers.adjustLaneLiveness(*LIS, *MRI, SlotIdx);
} else if (RequireIntervals) {
RegOpers.detectDeadDefs(MI, *LIS);
}
recede(RegOpers, LiveUses);
}
/// Advance across the current instruction.
void RegPressureTracker::advance(const RegisterOperands &RegOpers) {
assert(!TrackUntiedDefs && "unsupported mode");
assert(CurrPos != MBB->end());
if (!isTopClosed())
closeTop();
SlotIndex SlotIdx;
if (RequireIntervals)
SlotIdx = getCurrSlot();
// Open the bottom of the region using slot indexes.
if (isBottomClosed()) {
if (RequireIntervals)
static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
else
static_cast<RegionPressure&>(P).openBottom(CurrPos);
}
for (const RegisterMaskPair &Use : RegOpers.Uses) {
unsigned Reg = Use.RegUnit;
LaneBitmask LiveMask = LiveRegs.contains(Reg);
LaneBitmask LiveIn = Use.LaneMask & ~LiveMask;
if (LiveIn.any()) {
discoverLiveIn(RegisterMaskPair(Reg, LiveIn));
increaseRegPressure(Reg, LiveMask, LiveMask | LiveIn);
LiveRegs.insert(RegisterMaskPair(Reg, LiveIn));
}
// Kill liveness at last uses.
if (RequireIntervals) {
LaneBitmask LastUseMask = getLastUsedLanes(Reg, SlotIdx);
if (LastUseMask.any()) {
LiveRegs.erase(RegisterMaskPair(Reg, LastUseMask));
decreaseRegPressure(Reg, LiveMask, LiveMask & ~LastUseMask);
}
}
}
// Generate liveness for defs.
for (const RegisterMaskPair &Def : RegOpers.Defs) {
LaneBitmask PreviousMask = LiveRegs.insert(Def);
LaneBitmask NewMask = PreviousMask | Def.LaneMask;
increaseRegPressure(Def.RegUnit, PreviousMask, NewMask);
}
// Boost pressure for all dead defs together.
bumpDeadDefs(RegOpers.DeadDefs);
// Find the next instruction.
CurrPos = skipDebugInstructionsForward(std::next(CurrPos), MBB->end());
}
void RegPressureTracker::advance() {
const MachineInstr &MI = *CurrPos;
RegisterOperands RegOpers;
RegOpers.collect(MI, *TRI, *MRI, TrackLaneMasks, false);
if (TrackLaneMasks) {
SlotIndex SlotIdx = getCurrSlot();
RegOpers.adjustLaneLiveness(*LIS, *MRI, SlotIdx);
}
advance(RegOpers);
}
/// Find the max change in excess pressure across all sets.
static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
ArrayRef<unsigned> NewPressureVec,
RegPressureDelta &Delta,
const RegisterClassInfo *RCI,
ArrayRef<unsigned> LiveThruPressureVec) {
Delta.Excess = PressureChange();
for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
unsigned POld = OldPressureVec[i];
unsigned PNew = NewPressureVec[i];
int PDiff = (int)PNew - (int)POld;
if (!PDiff) // No change in this set in the common case.
continue;
// Only consider change beyond the limit.
unsigned Limit = RCI->getRegPressureSetLimit(i);
if (!LiveThruPressureVec.empty())
Limit += LiveThruPressureVec[i];
if (Limit > POld) {
if (Limit > PNew)
PDiff = 0; // Under the limit
else
PDiff = PNew - Limit; // Just exceeded limit.
} else if (Limit > PNew)
PDiff = Limit - POld; // Just obeyed limit.
if (PDiff) {
Delta.Excess = PressureChange(i);
Delta.Excess.setUnitInc(PDiff);
break;
}
}
}
/// Find the max change in max pressure that either surpasses a critical PSet
/// limit or exceeds the current MaxPressureLimit.
///
/// FIXME: comparing each element of the old and new MaxPressure vectors here is
/// silly. It's done now to demonstrate the concept but will go away with a
/// RegPressureTracker API change to work with pressure differences.
static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
ArrayRef<unsigned> NewMaxPressureVec,
ArrayRef<PressureChange> CriticalPSets,
ArrayRef<unsigned> MaxPressureLimit,
RegPressureDelta &Delta) {
Delta.CriticalMax = PressureChange();
Delta.CurrentMax = PressureChange();
unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
unsigned POld = OldMaxPressureVec[i];
unsigned PNew = NewMaxPressureVec[i];
if (PNew == POld) // No change in this set in the common case.
continue;
if (!Delta.CriticalMax.isValid()) {
while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
++CritIdx;
if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
if (PDiff > 0) {
Delta.CriticalMax = PressureChange(i);
Delta.CriticalMax.setUnitInc(PDiff);
}
}
}
// Find the first increase above MaxPressureLimit.
// (Ignores negative MDiff).
if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
Delta.CurrentMax = PressureChange(i);
Delta.CurrentMax.setUnitInc(PNew - POld);
if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
break;
}
}
}
/// Record the upward impact of a single instruction on current register
/// pressure. Unlike the advance/recede pressure tracking interface, this does
/// not discover live in/outs.
///
/// This is intended for speculative queries. It leaves pressure inconsistent
/// with the current position, so must be restored by the caller.
void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
assert(!MI->isDebugInstr() && "Expect a nondebug instruction.");
SlotIndex SlotIdx;
if (RequireIntervals)
SlotIdx = LIS->getInstructionIndex(*MI).getRegSlot();
// Account for register pressure similar to RegPressureTracker::recede().
RegisterOperands RegOpers;
RegOpers.collect(*MI, *TRI, *MRI, TrackLaneMasks, /*IgnoreDead=*/true);
assert(RegOpers.DeadDefs.size() == 0);
if (TrackLaneMasks)
RegOpers.adjustLaneLiveness(*LIS, *MRI, SlotIdx);
else if (RequireIntervals)
RegOpers.detectDeadDefs(*MI, *LIS);
// Boost max pressure for all dead defs together.
// Since CurrSetPressure and MaxSetPressure
bumpDeadDefs(RegOpers.DeadDefs);
// Kill liveness at live defs.
for (const RegisterMaskPair &P : RegOpers.Defs) {
unsigned Reg = P.RegUnit;
LaneBitmask LiveLanes = LiveRegs.contains(Reg);
LaneBitmask UseLanes = getRegLanes(RegOpers.Uses, Reg);
LaneBitmask DefLanes = P.LaneMask;
LaneBitmask LiveAfter = (LiveLanes & ~DefLanes) | UseLanes;
decreaseRegPressure(Reg, LiveLanes, LiveAfter);
}
// Generate liveness for uses.
for (const RegisterMaskPair &P : RegOpers.Uses) {
unsigned Reg = P.RegUnit;
LaneBitmask LiveLanes = LiveRegs.contains(Reg);
LaneBitmask LiveAfter = LiveLanes | P.LaneMask;
increaseRegPressure(Reg, LiveLanes, LiveAfter);
}
}
/// Consider the pressure increase caused by traversing this instruction
/// bottom-up. Find the pressure set with the most change beyond its pressure
/// limit based on the tracker's current pressure, and return the change in
/// number of register units of that pressure set introduced by this
/// instruction.
///
/// This assumes that the current LiveOut set is sufficient.
///
/// This is expensive for an on-the-fly query because it calls
/// bumpUpwardPressure to recompute the pressure sets based on current
/// liveness. This mainly exists to verify correctness, e.g. with
/// -verify-misched. getUpwardPressureDelta is the fast version of this query
/// that uses the per-SUnit cache of the PressureDiff.
void RegPressureTracker::
getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
RegPressureDelta &Delta,
ArrayRef<PressureChange> CriticalPSets,
ArrayRef<unsigned> MaxPressureLimit) {
// Snapshot Pressure.
// FIXME: The snapshot heap space should persist. But I'm planning to
// summarize the pressure effect so we don't need to snapshot at all.
std::vector<unsigned> SavedPressure = CurrSetPressure;
std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
bumpUpwardPressure(MI);
computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
LiveThruPressure);
computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
MaxPressureLimit, Delta);
assert(Delta.CriticalMax.getUnitInc() >= 0 &&
Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
// Restore the tracker's state.
P.MaxSetPressure.swap(SavedMaxPressure);
CurrSetPressure.swap(SavedPressure);
#ifndef NDEBUG
if (!PDiff)
return;
// Check if the alternate algorithm yields the same result.
RegPressureDelta Delta2;
getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
if (Delta != Delta2) {
dbgs() << "PDiff: ";
PDiff->dump(*TRI);
dbgs() << "DELTA: " << *MI;
if (Delta.Excess.isValid())
dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
<< " " << Delta.Excess.getUnitInc() << "\n";
if (Delta.CriticalMax.isValid())
dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
<< " " << Delta.CriticalMax.getUnitInc() << "\n";
if (Delta.CurrentMax.isValid())
dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
<< " " << Delta.CurrentMax.getUnitInc() << "\n";
if (Delta2.Excess.isValid())
dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
<< " " << Delta2.Excess.getUnitInc() << "\n";
if (Delta2.CriticalMax.isValid())
dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
<< " " << Delta2.CriticalMax.getUnitInc() << "\n";
if (Delta2.CurrentMax.isValid())
dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
<< " " << Delta2.CurrentMax.getUnitInc() << "\n";
llvm_unreachable("RegP Delta Mismatch");
}
#endif
}
/// This is the fast version of querying register pressure that does not
/// directly depend on current liveness.
///
/// @param Delta captures information needed for heuristics.
///
/// @param CriticalPSets Are the pressure sets that are known to exceed some
/// limit within the region, not necessarily at the current position.
///
/// @param MaxPressureLimit Is the max pressure within the region, not
/// necessarily at the current position.
void RegPressureTracker::
getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
RegPressureDelta &Delta,
ArrayRef<PressureChange> CriticalPSets,
ArrayRef<unsigned> MaxPressureLimit) const {
unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
for (PressureDiff::const_iterator
PDiffI = PDiff.begin(), PDiffE = PDiff.end();
PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
unsigned PSetID = PDiffI->getPSet();
unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
if (!LiveThruPressure.empty())
Limit += LiveThruPressure[PSetID];
unsigned POld = CurrSetPressure[PSetID];
unsigned MOld = P.MaxSetPressure[PSetID];
unsigned MNew = MOld;
// Ignore DeadDefs here because they aren't captured by PressureChange.
unsigned PNew = POld + PDiffI->getUnitInc();
assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld)
&& "PSet overflow/underflow");
if (PNew > MOld)
MNew = PNew;
// Check if current pressure has exceeded the limit.
if (!Delta.Excess.isValid()) {
unsigned ExcessInc = 0;
if (PNew > Limit)
ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
else if (POld > Limit)
ExcessInc = Limit - POld;
if (ExcessInc) {
Delta.Excess = PressureChange(PSetID);
Delta.Excess.setUnitInc(ExcessInc);
}
}
// Check if max pressure has exceeded a critical pressure set max.
if (MNew == MOld)
continue;
if (!Delta.CriticalMax.isValid()) {
while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
++CritIdx;
if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
if (CritInc > 0 && CritInc <= std::numeric_limits<int16_t>::max()) {
Delta.CriticalMax = PressureChange(PSetID);
Delta.CriticalMax.setUnitInc(CritInc);
}
}
}
// Check if max pressure has exceeded the current max.
if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
Delta.CurrentMax = PressureChange(PSetID);
Delta.CurrentMax.setUnitInc(MNew - MOld);
}
}
}
/// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
/// The query starts with a lane bitmask which gets lanes/bits removed for every
/// use we find.
static LaneBitmask findUseBetween(unsigned Reg, LaneBitmask LastUseMask,
SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
const MachineRegisterInfo &MRI,
const LiveIntervals *LIS) {
const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
for (const MachineOperand &MO : MRI.use_nodbg_operands(Reg)) {
if (MO.isUndef())
continue;
const MachineInstr *MI = MO.getParent();
SlotIndex InstSlot = LIS->getInstructionIndex(*MI).getRegSlot();
if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx) {
unsigned SubRegIdx = MO.getSubReg();
LaneBitmask UseMask = TRI.getSubRegIndexLaneMask(SubRegIdx);
LastUseMask &= ~UseMask;
if (LastUseMask.none())
return LaneBitmask::getNone();
}
}
return LastUseMask;
}
LaneBitmask RegPressureTracker::getLiveLanesAt(unsigned RegUnit,
SlotIndex Pos) const {
assert(RequireIntervals);
return getLanesWithProperty(*LIS, *MRI, TrackLaneMasks, RegUnit, Pos,
LaneBitmask::getAll(),
[](const LiveRange &LR, SlotIndex Pos) {
return LR.liveAt(Pos);
});
}
LaneBitmask RegPressureTracker::getLastUsedLanes(unsigned RegUnit,
SlotIndex Pos) const {
assert(RequireIntervals);
return getLanesWithProperty(*LIS, *MRI, TrackLaneMasks, RegUnit,
Pos.getBaseIndex(), LaneBitmask::getNone(),
[](const LiveRange &LR, SlotIndex Pos) {
const LiveRange::Segment *S = LR.getSegmentContaining(Pos);
return S != nullptr && S->end == Pos.getRegSlot();
});
}
LaneBitmask RegPressureTracker::getLiveThroughAt(unsigned RegUnit,
SlotIndex Pos) const {
assert(RequireIntervals);
return getLanesWithProperty(*LIS, *MRI, TrackLaneMasks, RegUnit, Pos,
LaneBitmask::getNone(),
[](const LiveRange &LR, SlotIndex Pos) {
const LiveRange::Segment *S = LR.getSegmentContaining(Pos);
return S != nullptr && S->start < Pos.getRegSlot(true) &&
S->end != Pos.getDeadSlot();
});
}
/// Record the downward impact of a single instruction on current register
/// pressure. Unlike the advance/recede pressure tracking interface, this does
/// not discover live in/outs.
///
/// This is intended for speculative queries. It leaves pressure inconsistent
/// with the current position, so must be restored by the caller.
void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
assert(!MI->isDebugInstr() && "Expect a nondebug instruction.");
SlotIndex SlotIdx;
if (RequireIntervals)
SlotIdx = LIS->getInstructionIndex(*MI).getRegSlot();
// Account for register pressure similar to RegPressureTracker::recede().
RegisterOperands RegOpers;
RegOpers.collect(*MI, *TRI, *MRI, TrackLaneMasks, false);
if (TrackLaneMasks)
RegOpers.adjustLaneLiveness(*LIS, *MRI, SlotIdx);
if (RequireIntervals) {
for (const RegisterMaskPair &Use : RegOpers.Uses) {
unsigned Reg = Use.RegUnit;
LaneBitmask LastUseMask = getLastUsedLanes(Reg, SlotIdx);
if (LastUseMask.none())
continue;
// The LastUseMask is queried from the liveness information of instruction
// which may be further down the schedule. Some lanes may actually not be
// last uses for the current position.
// FIXME: allow the caller to pass in the list of vreg uses that remain
// to be bottom-scheduled to avoid searching uses at each query.
SlotIndex CurrIdx = getCurrSlot();
LastUseMask
= findUseBetween(Reg, LastUseMask, CurrIdx, SlotIdx, *MRI, LIS);
if (LastUseMask.none())
continue;
LaneBitmask LiveMask = LiveRegs.contains(Reg);
LaneBitmask NewMask = LiveMask & ~LastUseMask;
decreaseRegPressure(Reg, LiveMask, NewMask);
}
}
// Generate liveness for defs.
for (const RegisterMaskPair &Def : RegOpers.Defs) {
unsigned Reg = Def.RegUnit;
LaneBitmask LiveMask = LiveRegs.contains(Reg);
LaneBitmask NewMask = LiveMask | Def.LaneMask;
increaseRegPressure(Reg, LiveMask, NewMask);
}
// Boost pressure for all dead defs together.
bumpDeadDefs(RegOpers.DeadDefs);
}
/// Consider the pressure increase caused by traversing this instruction
/// top-down. Find the register class with the most change in its pressure limit
/// based on the tracker's current pressure, and return the number of excess
/// register units of that pressure set introduced by this instruction.
///
/// This assumes that the current LiveIn set is sufficient.
///
/// This is expensive for an on-the-fly query because it calls
/// bumpDownwardPressure to recompute the pressure sets based on current
/// liveness. We don't yet have a fast version of downward pressure tracking
/// analogous to getUpwardPressureDelta.
void RegPressureTracker::
getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
ArrayRef<PressureChange> CriticalPSets,
ArrayRef<unsigned> MaxPressureLimit) {
// Snapshot Pressure.
std::vector<unsigned> SavedPressure = CurrSetPressure;
std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
bumpDownwardPressure(MI);
computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
LiveThruPressure);
computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
MaxPressureLimit, Delta);
assert(Delta.CriticalMax.getUnitInc() >= 0 &&
Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
// Restore the tracker's state.
P.MaxSetPressure.swap(SavedMaxPressure);
CurrSetPressure.swap(SavedPressure);
}
/// Get the pressure of each PSet after traversing this instruction bottom-up.
void RegPressureTracker::
getUpwardPressure(const MachineInstr *MI,
std::vector<unsigned> &PressureResult,
std::vector<unsigned> &MaxPressureResult) {
// Snapshot pressure.
PressureResult = CurrSetPressure;
MaxPressureResult = P.MaxSetPressure;
bumpUpwardPressure(MI);
// Current pressure becomes the result. Restore current pressure.
P.MaxSetPressure.swap(MaxPressureResult);
CurrSetPressure.swap(PressureResult);
}
/// Get the pressure of each PSet after traversing this instruction top-down.
void RegPressureTracker::
getDownwardPressure(const MachineInstr *MI,
std::vector<unsigned> &PressureResult,
std::vector<unsigned> &MaxPressureResult) {
// Snapshot pressure.
PressureResult = CurrSetPressure;
MaxPressureResult = P.MaxSetPressure;
bumpDownwardPressure(MI);
// Current pressure becomes the result. Restore current pressure.
P.MaxSetPressure.swap(MaxPressureResult);
CurrSetPressure.swap(PressureResult);
}
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