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Diffstat (limited to 'contrib/llvm/lib/CodeGen/RegisterPressure.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/RegisterPressure.cpp | 1015 |
1 files changed, 1015 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/RegisterPressure.cpp b/contrib/llvm/lib/CodeGen/RegisterPressure.cpp new file mode 100644 index 0000000..8382b09 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/RegisterPressure.cpp @@ -0,0 +1,1015 @@ +//===-- 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; + if (CurrSetPressure[*PSetI] > P.MaxSetPressure[*PSetI]) { + 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); +} |
