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freebsd-dev/lib/CodeGen/RegisterPressure.cpp

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//===-- RegisterPressure.cpp - Dynamic Register Pressure ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the RegisterPressure class which can be used to track
// MachineInstr level register pressure.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/RegisterPressure.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
/// Increase pressure for each pressure set provided by TargetRegisterInfo.
static void increaseSetPressure(std::vector<unsigned> &CurrSetPressure,
PSetIterator PSetI) {
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,
PSetIterator PSetI) {
unsigned Weight = PSetI.getWeight();
for (; PSetI.isValid(); ++PSetI) {
assert(CurrSetPressure[*PSetI] >= Weight && "register pressure underflow");
CurrSetPressure[*PSetI] -= Weight;
}
}
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 (unsigned Reg : LiveInRegs)
dbgs() << PrintVRegOrUnit(Reg, TRI) << " ";
dbgs() << '\n';
dbgs() << "Live Out: ";
for (unsigned Reg : LiveOutRegs)
dbgs() << PrintVRegOrUnit(Reg, TRI) << " ";
dbgs() << '\n';
}
LLVM_DUMP_METHOD
void RegPressureTracker::dump() const {
if (!isTopClosed() || !isBottomClosed()) {
dbgs() << "Curr Pressure: ";
dumpRegSetPressure(CurrSetPressure, TRI);
}
P.dump(TRI);
}
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';
}
/// Increase the current pressure as impacted by these registers and bump
/// the high water mark if needed.
void RegPressureTracker::increaseRegPressure(ArrayRef<unsigned> RegUnits) {
for (unsigned RegUnit : RegUnits) {
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]);
}
}
}
/// Simply decrease the current pressure as impacted by these registers.
void RegPressureTracker::decreaseRegPressure(ArrayRef<unsigned> RegUnits) {
for (unsigned RegUnit : RegUnits)
decreaseSetPressure(CurrSetPressure, MRI->getPressureSets(RegUnit));
}
/// 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 (TargetRegisterInfo::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 ShouldTrackUntiedDefs)
{
reset();
MF = mf;
TRI = MF->getSubtarget().getRegisterInfo();
RCI = rci;
MRI = &MF->getRegInfo();
MBB = mbb;
TrackUntiedDefs = ShouldTrackUntiedDefs;
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 = CurrPos;
while (IdxPos != MBB->end() && IdxPos->isDebugValue())
++IdxPos;
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 (unsigned Reg : P.LiveOutRegs) {
if (TargetRegisterInfo::isVirtualRegister(Reg)
&& !RPTracker.hasUntiedDef(Reg)) {
increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
}
}
}
/// \brief Convenient wrapper for checking membership in RegisterOperands.
/// (std::count() doesn't have an early exit).
static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
}
namespace {
/// List of register defined and used by a machine instruction.
class RegisterOperands {
public:
SmallVector<unsigned, 8> Uses;
SmallVector<unsigned, 8> Defs;
SmallVector<unsigned, 8> DeadDefs;
void collect(const MachineInstr &MI, const TargetRegisterInfo &TRI,
const MachineRegisterInfo &MRI, bool IgnoreDead = false);
/// Use liveness information to find dead defs not marked with a dead flag
/// and move them to the DeadDefs vector.
void detectDeadDefs(const MachineInstr &MI, const LiveIntervals &LIS);
};
/// Collect this instruction's unique uses and defs into SmallVectors for
/// processing defs and uses in order.
///
/// FIXME: always ignore tied opers
class RegisterOperandsCollector {
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.
SmallVectorImpl<unsigned>::iterator I =
std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
}
/// 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.readsReg())
pushRegUnits(Reg, RegOpers.Uses);
if (MO.isDef()) {
if (MO.isDead()) {
if (!IgnoreDead)
pushRegUnits(Reg, RegOpers.DeadDefs);
} else
pushRegUnits(Reg, RegOpers.Defs);
}
}
void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) const {
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
if (containsReg(RegUnits, Reg))
return;
RegUnits.push_back(Reg);
} else if (MRI.isAllocatable(Reg)) {
for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units) {
if (containsReg(RegUnits, *Units))
continue;
RegUnits.push_back(*Units);
}
}
}
friend class RegisterOperands;
};
void RegisterOperands::collect(const MachineInstr &MI,
const TargetRegisterInfo &TRI,
const MachineRegisterInfo &MRI,
bool IgnoreDead) {
RegisterOperandsCollector Collector(*this, TRI, MRI, IgnoreDead);
Collector.collectInstr(MI);
}
void RegisterOperands::detectDeadDefs(const MachineInstr &MI,
const LiveIntervals &LIS) {
SlotIndex SlotIdx = LIS.getInstructionIndex(&MI);
for (SmallVectorImpl<unsigned>::iterator RI = Defs.begin();
RI != Defs.end(); /*empty*/) {
unsigned Reg = *RI;
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(Reg);
RI = Defs.erase(RI);
continue;
}
}
++RI;
}
}
} // namespace
/// 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 = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
}
/// 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;
if (J != E)
*I = *J;
}
}
}
/// Record the pressure difference induced by the given operand list.
static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
const MachineRegisterInfo *MRI) {
assert(!PDiff.begin()->isValid() && "stale PDiff");
for (unsigned Reg : RegOpers.Defs)
PDiff.addPressureChange(Reg, true, MRI);
for (unsigned Reg : RegOpers.Uses)
PDiff.addPressureChange(Reg, false, MRI);
}
/// Force liveness of registers.
void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
for (unsigned Reg : Regs) {
if (LiveRegs.insert(Reg))
increaseRegPressure(Reg);
}
}
/// Add Reg to the live in set and increase max pressure.
void RegPressureTracker::discoverLiveIn(unsigned Reg) {
assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
if (containsReg(P.LiveInRegs, Reg))
return;
// At live in discovery, unconditionally increase the high water mark.
P.LiveInRegs.push_back(Reg);
increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
}
/// Add Reg to the live out set and increase max pressure.
void RegPressureTracker::discoverLiveOut(unsigned Reg) {
assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
if (containsReg(P.LiveOutRegs, Reg))
return;
// At live out discovery, unconditionally increase the high water mark.
P.LiveOutRegs.push_back(Reg);
increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
}
/// 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(SmallVectorImpl<unsigned> *LiveUses,
PressureDiff *PDiff) {
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.
do
--CurrPos;
while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
assert(!CurrPos->isDebugValue());
SlotIndex SlotIdx;
if (RequireIntervals)
SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
// Open the top of the region using slot indexes.
if (RequireIntervals && isTopClosed())
static_cast<IntervalPressure&>(P).openTop(SlotIdx);
const MachineInstr &MI = *CurrPos;
RegisterOperands RegOpers;
RegOpers.collect(MI, *TRI, *MRI);
if (RequireIntervals)
RegOpers.detectDeadDefs(MI, *LIS);
if (PDiff)
collectPDiff(*PDiff, RegOpers, MRI);
// Boost pressure for all dead defs together.
increaseRegPressure(RegOpers.DeadDefs);
decreaseRegPressure(RegOpers.DeadDefs);
// Kill liveness at live defs.
// TODO: consider earlyclobbers?
for (unsigned Reg : RegOpers.Defs) {
if (LiveRegs.erase(Reg))
decreaseRegPressure(Reg);
else
discoverLiveOut(Reg);
}
// Generate liveness for uses.
for (unsigned Reg : RegOpers.Uses) {
if (!LiveRegs.contains(Reg)) {
// Adjust liveouts if LiveIntervals are available.
if (RequireIntervals) {
const LiveRange *LR = getLiveRange(*LIS, Reg);
if (LR) {
LiveQueryResult LRQ = LR->Query(SlotIdx);
if (!LRQ.isKill() && !LRQ.valueDefined())
discoverLiveOut(Reg);
}
}
increaseRegPressure(Reg);
LiveRegs.insert(Reg);
if (LiveUses && !containsReg(*LiveUses, Reg))
LiveUses->push_back(Reg);
}
}
if (TrackUntiedDefs) {
for (unsigned Reg : RegOpers.Defs) {
if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
UntiedDefs.insert(Reg);
}
}
}
/// Advance across the current instruction.
void RegPressureTracker::advance() {
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);
}
RegisterOperands RegOpers;
RegOpers.collect(*CurrPos, *TRI, *MRI);
for (unsigned Reg : RegOpers.Uses) {
// Discover live-ins.
bool isLive = LiveRegs.contains(Reg);
if (!isLive)
discoverLiveIn(Reg);
// Kill liveness at last uses.
bool lastUse = false;
if (RequireIntervals) {
const LiveRange *LR = getLiveRange(*LIS, Reg);
lastUse = LR && LR->Query(SlotIdx).isKill();
} else {
// Allocatable physregs are always single-use before register rewriting.
lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
}
if (lastUse && isLive) {
LiveRegs.erase(Reg);
decreaseRegPressure(Reg);
} else if (!lastUse && !isLive)
increaseRegPressure(Reg);
}
// Generate liveness for defs.
for (unsigned Reg : RegOpers.Defs) {
if (LiveRegs.insert(Reg))
increaseRegPressure(Reg);
}
// Boost pressure for all dead defs together.
increaseRegPressure(RegOpers.DeadDefs);
decreaseRegPressure(RegOpers.DeadDefs);
// Find the next instruction.
do
++CurrPos;
while (CurrPos != MBB->end() && CurrPos->isDebugValue());
}
/// 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->isDebugValue() && "Expect a nondebug instruction.");
// Account for register pressure similar to RegPressureTracker::recede().
RegisterOperands RegOpers;
RegOpers.collect(*MI, *TRI, *MRI, /*IgnoreDead=*/true);
assert(RegOpers.DeadDefs.size() == 0);
if (RequireIntervals)
RegOpers.detectDeadDefs(*MI, *LIS);
// Kill liveness at live defs.
for (unsigned Reg : RegOpers.Defs) {
if (!containsReg(RegOpers.Uses, Reg))
decreaseRegPressure(Reg);
}
// Generate liveness for uses.
for (unsigned Reg : RegOpers.Uses) {
if (!LiveRegs.contains(Reg))
increaseRegPressure(Reg);
}
}
/// 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 <= INT16_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).
static bool findUseBetween(unsigned Reg, SlotIndex PriorUseIdx,
SlotIndex NextUseIdx, const MachineRegisterInfo &MRI,
const LiveIntervals *LIS) {
for (const MachineInstr &MI : MRI.use_nodbg_instructions(Reg)) {
SlotIndex InstSlot = LIS->getInstructionIndex(&MI).getRegSlot();
if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
return true;
}
return false;
}
/// 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->isDebugValue() && "Expect a nondebug instruction.");
// Account for register pressure similar to RegPressureTracker::recede().
RegisterOperands RegOpers;
RegOpers.collect(*MI, *TRI, *MRI);
// Kill liveness at last uses. Assume allocatable physregs are single-use
// rather than checking LiveIntervals.
SlotIndex SlotIdx;
if (RequireIntervals)
SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
for (unsigned Reg : RegOpers.Uses) {
if (RequireIntervals) {
// 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();
const LiveRange *LR = getLiveRange(*LIS, Reg);
if (LR) {
LiveQueryResult LRQ = LR->Query(SlotIdx);
if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, *MRI, LIS))
decreaseRegPressure(Reg);
}
} else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
// Allocatable physregs are always single-use before register rewriting.
decreaseRegPressure(Reg);
}
}
// Generate liveness for defs.
increaseRegPressure(RegOpers.Defs);
// Boost pressure for all dead defs together.
increaseRegPressure(RegOpers.DeadDefs);
decreaseRegPressure(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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