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Diffstat (limited to 'lib/CodeGen/RegAllocLinearScan.cpp')
| -rw-r--r-- | lib/CodeGen/RegAllocLinearScan.cpp | 1543 |
1 files changed, 0 insertions, 1543 deletions
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp deleted file mode 100644 index ce3fb90b1126..000000000000 --- a/lib/CodeGen/RegAllocLinearScan.cpp +++ /dev/null @@ -1,1543 +0,0 @@ -//===-- RegAllocLinearScan.cpp - Linear Scan register allocator -----------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements a linear scan register allocator. -// -//===----------------------------------------------------------------------===// - -#define DEBUG_TYPE "regalloc" -#include "LiveDebugVariables.h" -#include "LiveRangeEdit.h" -#include "VirtRegMap.h" -#include "VirtRegRewriter.h" -#include "RegisterClassInfo.h" -#include "Spiller.h" -#include "llvm/Analysis/AliasAnalysis.h" -#include "llvm/Function.h" -#include "llvm/CodeGen/CalcSpillWeights.h" -#include "llvm/CodeGen/LiveIntervalAnalysis.h" -#include "llvm/CodeGen/MachineFunctionPass.h" -#include "llvm/CodeGen/MachineInstr.h" -#include "llvm/CodeGen/MachineLoopInfo.h" -#include "llvm/CodeGen/MachineRegisterInfo.h" -#include "llvm/CodeGen/Passes.h" -#include "llvm/CodeGen/RegAllocRegistry.h" -#include "llvm/Target/TargetRegisterInfo.h" -#include "llvm/Target/TargetMachine.h" -#include "llvm/Target/TargetOptions.h" -#include "llvm/Target/TargetInstrInfo.h" -#include "llvm/ADT/EquivalenceClasses.h" -#include "llvm/ADT/SmallSet.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/ErrorHandling.h" -#include "llvm/Support/raw_ostream.h" -#include <algorithm> -#include <queue> -#include <memory> -#include <cmath> - -using namespace llvm; - -STATISTIC(NumIters , "Number of iterations performed"); -STATISTIC(NumBacktracks, "Number of times we had to backtrack"); -STATISTIC(NumCoalesce, "Number of copies coalesced"); -STATISTIC(NumDowngrade, "Number of registers downgraded"); - -static cl::opt<bool> -NewHeuristic("new-spilling-heuristic", - cl::desc("Use new spilling heuristic"), - cl::init(false), cl::Hidden); - -static cl::opt<bool> -TrivCoalesceEnds("trivial-coalesce-ends", - cl::desc("Attempt trivial coalescing of interval ends"), - cl::init(false), cl::Hidden); - -static cl::opt<bool> -AvoidWAWHazard("avoid-waw-hazard", - cl::desc("Avoid write-write hazards for some register classes"), - cl::init(false), cl::Hidden); - -static RegisterRegAlloc -linearscanRegAlloc("linearscan", "linear scan register allocator", - createLinearScanRegisterAllocator); - -namespace { - // When we allocate a register, add it to a fixed-size queue of - // registers to skip in subsequent allocations. This trades a small - // amount of register pressure and increased spills for flexibility in - // the post-pass scheduler. - // - // Note that in a the number of registers used for reloading spills - // will be one greater than the value of this option. - // - // One big limitation of this is that it doesn't differentiate between - // different register classes. So on x86-64, if there is xmm register - // pressure, it can caused fewer GPRs to be held in the queue. - static cl::opt<unsigned> - NumRecentlyUsedRegs("linearscan-skip-count", - cl::desc("Number of registers for linearscan to remember" - "to skip."), - cl::init(0), - cl::Hidden); - - struct RALinScan : public MachineFunctionPass { - static char ID; - RALinScan() : MachineFunctionPass(ID) { - initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry()); - initializeLiveIntervalsPass(*PassRegistry::getPassRegistry()); - initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry()); - initializeRegisterCoalescerPass( - *PassRegistry::getPassRegistry()); - initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry()); - initializeLiveStacksPass(*PassRegistry::getPassRegistry()); - initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry()); - initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry()); - initializeVirtRegMapPass(*PassRegistry::getPassRegistry()); - initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry()); - - // Initialize the queue to record recently-used registers. - if (NumRecentlyUsedRegs > 0) - RecentRegs.resize(NumRecentlyUsedRegs, 0); - RecentNext = RecentRegs.begin(); - avoidWAW_ = 0; - } - - typedef std::pair<LiveInterval*, LiveInterval::iterator> IntervalPtr; - typedef SmallVector<IntervalPtr, 32> IntervalPtrs; - private: - /// RelatedRegClasses - This structure is built the first time a function is - /// compiled, and keeps track of which register classes have registers that - /// belong to multiple classes or have aliases that are in other classes. - EquivalenceClasses<const TargetRegisterClass*> RelatedRegClasses; - DenseMap<unsigned, const TargetRegisterClass*> OneClassForEachPhysReg; - - // NextReloadMap - For each register in the map, it maps to the another - // register which is defined by a reload from the same stack slot and - // both reloads are in the same basic block. - DenseMap<unsigned, unsigned> NextReloadMap; - - // DowngradedRegs - A set of registers which are being "downgraded", i.e. - // un-favored for allocation. - SmallSet<unsigned, 8> DowngradedRegs; - - // DowngradeMap - A map from virtual registers to physical registers being - // downgraded for the virtual registers. - DenseMap<unsigned, unsigned> DowngradeMap; - - MachineFunction* mf_; - MachineRegisterInfo* mri_; - const TargetMachine* tm_; - const TargetRegisterInfo* tri_; - const TargetInstrInfo* tii_; - BitVector allocatableRegs_; - BitVector reservedRegs_; - LiveIntervals* li_; - MachineLoopInfo *loopInfo; - RegisterClassInfo RegClassInfo; - - /// handled_ - Intervals are added to the handled_ set in the order of their - /// start value. This is uses for backtracking. - std::vector<LiveInterval*> handled_; - - /// fixed_ - Intervals that correspond to machine registers. - /// - IntervalPtrs fixed_; - - /// active_ - Intervals that are currently being processed, and which have a - /// live range active for the current point. - IntervalPtrs active_; - - /// inactive_ - Intervals that are currently being processed, but which have - /// a hold at the current point. - IntervalPtrs inactive_; - - typedef std::priority_queue<LiveInterval*, - SmallVector<LiveInterval*, 64>, - greater_ptr<LiveInterval> > IntervalHeap; - IntervalHeap unhandled_; - - /// regUse_ - Tracks register usage. - SmallVector<unsigned, 32> regUse_; - SmallVector<unsigned, 32> regUseBackUp_; - - /// vrm_ - Tracks register assignments. - VirtRegMap* vrm_; - - std::auto_ptr<VirtRegRewriter> rewriter_; - - std::auto_ptr<Spiller> spiller_; - - // The queue of recently-used registers. - SmallVector<unsigned, 4> RecentRegs; - SmallVector<unsigned, 4>::iterator RecentNext; - - // Last write-after-write register written. - unsigned avoidWAW_; - - // Record that we just picked this register. - void recordRecentlyUsed(unsigned reg) { - assert(reg != 0 && "Recently used register is NOREG!"); - if (!RecentRegs.empty()) { - *RecentNext++ = reg; - if (RecentNext == RecentRegs.end()) - RecentNext = RecentRegs.begin(); - } - } - - public: - virtual const char* getPassName() const { - return "Linear Scan Register Allocator"; - } - - virtual void getAnalysisUsage(AnalysisUsage &AU) const { - AU.setPreservesCFG(); - AU.addRequired<AliasAnalysis>(); - AU.addPreserved<AliasAnalysis>(); - AU.addRequired<LiveIntervals>(); - AU.addPreserved<SlotIndexes>(); - if (StrongPHIElim) - AU.addRequiredID(StrongPHIEliminationID); - // Make sure PassManager knows which analyses to make available - // to coalescing and which analyses coalescing invalidates. - AU.addRequiredTransitiveID(RegisterCoalescerPassID); - AU.addRequired<CalculateSpillWeights>(); - AU.addRequiredID(LiveStacksID); - AU.addPreservedID(LiveStacksID); - AU.addRequired<MachineLoopInfo>(); - AU.addPreserved<MachineLoopInfo>(); - AU.addRequired<VirtRegMap>(); - AU.addPreserved<VirtRegMap>(); - AU.addRequired<LiveDebugVariables>(); - AU.addPreserved<LiveDebugVariables>(); - AU.addRequiredID(MachineDominatorsID); - AU.addPreservedID(MachineDominatorsID); - MachineFunctionPass::getAnalysisUsage(AU); - } - - /// runOnMachineFunction - register allocate the whole function - bool runOnMachineFunction(MachineFunction&); - - // Determine if we skip this register due to its being recently used. - bool isRecentlyUsed(unsigned reg) const { - return reg == avoidWAW_ || - std::find(RecentRegs.begin(), RecentRegs.end(), reg) != RecentRegs.end(); - } - - private: - /// linearScan - the linear scan algorithm - void linearScan(); - - /// initIntervalSets - initialize the interval sets. - /// - void initIntervalSets(); - - /// processActiveIntervals - expire old intervals and move non-overlapping - /// ones to the inactive list. - void processActiveIntervals(SlotIndex CurPoint); - - /// processInactiveIntervals - expire old intervals and move overlapping - /// ones to the active list. - void processInactiveIntervals(SlotIndex CurPoint); - - /// hasNextReloadInterval - Return the next liveinterval that's being - /// defined by a reload from the same SS as the specified one. - LiveInterval *hasNextReloadInterval(LiveInterval *cur); - - /// DowngradeRegister - Downgrade a register for allocation. - void DowngradeRegister(LiveInterval *li, unsigned Reg); - - /// UpgradeRegister - Upgrade a register for allocation. - void UpgradeRegister(unsigned Reg); - - /// assignRegOrStackSlotAtInterval - assign a register if one - /// is available, or spill. - void assignRegOrStackSlotAtInterval(LiveInterval* cur); - - void updateSpillWeights(std::vector<float> &Weights, - unsigned reg, float weight, - const TargetRegisterClass *RC); - - /// findIntervalsToSpill - Determine the intervals to spill for the - /// specified interval. It's passed the physical registers whose spill - /// weight is the lowest among all the registers whose live intervals - /// conflict with the interval. - void findIntervalsToSpill(LiveInterval *cur, - std::vector<std::pair<unsigned,float> > &Candidates, - unsigned NumCands, - SmallVector<LiveInterval*, 8> &SpillIntervals); - - /// attemptTrivialCoalescing - If a simple interval is defined by a copy, - /// try to allocate the definition to the same register as the source, - /// if the register is not defined during the life time of the interval. - /// This eliminates a copy, and is used to coalesce copies which were not - /// coalesced away before allocation either due to dest and src being in - /// different register classes or because the coalescer was overly - /// conservative. - unsigned attemptTrivialCoalescing(LiveInterval &cur, unsigned Reg); - - /// - /// Register usage / availability tracking helpers. - /// - - void initRegUses() { - regUse_.resize(tri_->getNumRegs(), 0); - regUseBackUp_.resize(tri_->getNumRegs(), 0); - } - - void finalizeRegUses() { -#ifndef NDEBUG - // Verify all the registers are "freed". - bool Error = false; - for (unsigned i = 0, e = tri_->getNumRegs(); i != e; ++i) { - if (regUse_[i] != 0) { - dbgs() << tri_->getName(i) << " is still in use!\n"; - Error = true; - } - } - if (Error) - llvm_unreachable(0); -#endif - regUse_.clear(); - regUseBackUp_.clear(); - } - - void addRegUse(unsigned physReg) { - assert(TargetRegisterInfo::isPhysicalRegister(physReg) && - "should be physical register!"); - ++regUse_[physReg]; - for (const unsigned* as = tri_->getAliasSet(physReg); *as; ++as) - ++regUse_[*as]; - } - - void delRegUse(unsigned physReg) { - assert(TargetRegisterInfo::isPhysicalRegister(physReg) && - "should be physical register!"); - assert(regUse_[physReg] != 0); - --regUse_[physReg]; - for (const unsigned* as = tri_->getAliasSet(physReg); *as; ++as) { - assert(regUse_[*as] != 0); - --regUse_[*as]; - } - } - - bool isRegAvail(unsigned physReg) const { - assert(TargetRegisterInfo::isPhysicalRegister(physReg) && - "should be physical register!"); - return regUse_[physReg] == 0; - } - - void backUpRegUses() { - regUseBackUp_ = regUse_; - } - - void restoreRegUses() { - regUse_ = regUseBackUp_; - } - - /// - /// Register handling helpers. - /// - - /// getFreePhysReg - return a free physical register for this virtual - /// register interval if we have one, otherwise return 0. - unsigned getFreePhysReg(LiveInterval* cur); - unsigned getFreePhysReg(LiveInterval* cur, - const TargetRegisterClass *RC, - unsigned MaxInactiveCount, - SmallVector<unsigned, 256> &inactiveCounts, - bool SkipDGRegs); - - /// getFirstNonReservedPhysReg - return the first non-reserved physical - /// register in the register class. - unsigned getFirstNonReservedPhysReg(const TargetRegisterClass *RC) { - ArrayRef<unsigned> O = RegClassInfo.getOrder(RC); - assert(!O.empty() && "All registers reserved?!"); - return O.front(); - } - - void ComputeRelatedRegClasses(); - - template <typename ItTy> - void printIntervals(const char* const str, ItTy i, ItTy e) const { - DEBUG({ - if (str) - dbgs() << str << " intervals:\n"; - - for (; i != e; ++i) { - dbgs() << '\t' << *i->first << " -> "; - - unsigned reg = i->first->reg; - if (TargetRegisterInfo::isVirtualRegister(reg)) - reg = vrm_->getPhys(reg); - - dbgs() << tri_->getName(reg) << '\n'; - } - }); - } - }; - char RALinScan::ID = 0; -} - -INITIALIZE_PASS_BEGIN(RALinScan, "linearscan-regalloc", - "Linear Scan Register Allocator", false, false) -INITIALIZE_PASS_DEPENDENCY(LiveIntervals) -INITIALIZE_PASS_DEPENDENCY(StrongPHIElimination) -INITIALIZE_PASS_DEPENDENCY(CalculateSpillWeights) -INITIALIZE_PASS_DEPENDENCY(LiveStacks) -INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) -INITIALIZE_PASS_DEPENDENCY(VirtRegMap) -INITIALIZE_PASS_DEPENDENCY(RegisterCoalescer) -INITIALIZE_AG_DEPENDENCY(AliasAnalysis) -INITIALIZE_PASS_END(RALinScan, "linearscan-regalloc", - "Linear Scan Register Allocator", false, false) - -void RALinScan::ComputeRelatedRegClasses() { - // First pass, add all reg classes to the union, and determine at least one - // reg class that each register is in. - bool HasAliases = false; - for (TargetRegisterInfo::regclass_iterator RCI = tri_->regclass_begin(), - E = tri_->regclass_end(); RCI != E; ++RCI) { - RelatedRegClasses.insert(*RCI); - for (TargetRegisterClass::iterator I = (*RCI)->begin(), E = (*RCI)->end(); - I != E; ++I) { - HasAliases = HasAliases || *tri_->getAliasSet(*I) != 0; - - const TargetRegisterClass *&PRC = OneClassForEachPhysReg[*I]; - if (PRC) { - // Already processed this register. Just make sure we know that - // multiple register classes share a register. - RelatedRegClasses.unionSets(PRC, *RCI); - } else { - PRC = *RCI; - } - } - } - - // Second pass, now that we know conservatively what register classes each reg - // belongs to, add info about aliases. We don't need to do this for targets - // without register aliases. - if (HasAliases) - for (DenseMap<unsigned, const TargetRegisterClass*>::iterator - I = OneClassForEachPhysReg.begin(), E = OneClassForEachPhysReg.end(); - I != E; ++I) - for (const unsigned *AS = tri_->getAliasSet(I->first); *AS; ++AS) { - const TargetRegisterClass *AliasClass = - OneClassForEachPhysReg.lookup(*AS); - if (AliasClass) - RelatedRegClasses.unionSets(I->second, AliasClass); - } -} - -/// attemptTrivialCoalescing - If a simple interval is defined by a copy, try -/// allocate the definition the same register as the source register if the -/// register is not defined during live time of the interval. If the interval is -/// killed by a copy, try to use the destination register. This eliminates a -/// copy. This is used to coalesce copies which were not coalesced away before -/// allocation either due to dest and src being in different register classes or -/// because the coalescer was overly conservative. -unsigned RALinScan::attemptTrivialCoalescing(LiveInterval &cur, unsigned Reg) { - unsigned Preference = vrm_->getRegAllocPref(cur.reg); - if ((Preference && Preference == Reg) || !cur.containsOneValue()) - return Reg; - - // We cannot handle complicated live ranges. Simple linear stuff only. - if (cur.ranges.size() != 1) - return Reg; - - const LiveRange &range = cur.ranges.front(); - - VNInfo *vni = range.valno; - if (vni->isUnused() || !vni->def.isValid()) - return Reg; - - unsigned CandReg; - { - MachineInstr *CopyMI; - if ((CopyMI = li_->getInstructionFromIndex(vni->def)) && CopyMI->isCopy()) - // Defined by a copy, try to extend SrcReg forward - CandReg = CopyMI->getOperand(1).getReg(); - else if (TrivCoalesceEnds && - (CopyMI = li_->getInstructionFromIndex(range.end.getBaseIndex())) && - CopyMI->isCopy() && cur.reg == CopyMI->getOperand(1).getReg()) - // Only used by a copy, try to extend DstReg backwards - CandReg = CopyMI->getOperand(0).getReg(); - else - return Reg; - - // If the target of the copy is a sub-register then don't coalesce. - if(CopyMI->getOperand(0).getSubReg()) - return Reg; - } - - if (TargetRegisterInfo::isVirtualRegister(CandReg)) { - if (!vrm_->isAssignedReg(CandReg)) - return Reg; - CandReg = vrm_->getPhys(CandReg); - } - if (Reg == CandReg) - return Reg; - - const TargetRegisterClass *RC = mri_->getRegClass(cur.reg); - if (!RC->contains(CandReg)) - return Reg; - - if (li_->conflictsWithPhysReg(cur, *vrm_, CandReg)) - return Reg; - - // Try to coalesce. - DEBUG(dbgs() << "Coalescing: " << cur << " -> " << tri_->getName(CandReg) - << '\n'); - vrm_->clearVirt(cur.reg); - vrm_->assignVirt2Phys(cur.reg, CandReg); - - ++NumCoalesce; - return CandReg; -} - -bool RALinScan::runOnMachineFunction(MachineFunction &fn) { - mf_ = &fn; - mri_ = &fn.getRegInfo(); - tm_ = &fn.getTarget(); - tri_ = tm_->getRegisterInfo(); - tii_ = tm_->getInstrInfo(); - allocatableRegs_ = tri_->getAllocatableSet(fn); - reservedRegs_ = tri_->getReservedRegs(fn); - li_ = &getAnalysis<LiveIntervals>(); - loopInfo = &getAnalysis<MachineLoopInfo>(); - RegClassInfo.runOnMachineFunction(fn); - - // We don't run the coalescer here because we have no reason to - // interact with it. If the coalescer requires interaction, it - // won't do anything. If it doesn't require interaction, we assume - // it was run as a separate pass. - - // If this is the first function compiled, compute the related reg classes. - if (RelatedRegClasses.empty()) - ComputeRelatedRegClasses(); - - // Also resize register usage trackers. - initRegUses(); - - vrm_ = &getAnalysis<VirtRegMap>(); - if (!rewriter_.get()) rewriter_.reset(createVirtRegRewriter()); - - spiller_.reset(createSpiller(*this, *mf_, *vrm_)); - - initIntervalSets(); - - linearScan(); - - // Rewrite spill code and update the PhysRegsUsed set. - rewriter_->runOnMachineFunction(*mf_, *vrm_, li_); - - // Write out new DBG_VALUE instructions. - getAnalysis<LiveDebugVariables>().emitDebugValues(vrm_); - - assert(unhandled_.empty() && "Unhandled live intervals remain!"); - - finalizeRegUses(); - - fixed_.clear(); - active_.clear(); - inactive_.clear(); - handled_.clear(); - NextReloadMap.clear(); - DowngradedRegs.clear(); - DowngradeMap.clear(); - spiller_.reset(0); - - return true; -} - -/// initIntervalSets - initialize the interval sets. -/// -void RALinScan::initIntervalSets() -{ - assert(unhandled_.empty() && fixed_.empty() && - active_.empty() && inactive_.empty() && - "interval sets should be empty on initialization"); - - handled_.reserve(li_->getNumIntervals()); - - for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i) { - if (TargetRegisterInfo::isPhysicalRegister(i->second->reg)) { - if (!i->second->empty() && allocatableRegs_.test(i->second->reg)) { - mri_->setPhysRegUsed(i->second->reg); - fixed_.push_back(std::make_pair(i->second, i->second->begin())); - } - } else { - if (i->second->empty()) { - assignRegOrStackSlotAtInterval(i->second); - } - else - unhandled_.push(i->second); - } - } -} - -void RALinScan::linearScan() { - // linear scan algorithm - DEBUG({ - dbgs() << "********** LINEAR SCAN **********\n" - << "********** Function: " - << mf_->getFunction()->getName() << '\n'; - printIntervals("fixed", fixed_.begin(), fixed_.end()); - }); - - while (!unhandled_.empty()) { - // pick the interval with the earliest start point - LiveInterval* cur = unhandled_.top(); - unhandled_.pop(); - ++NumIters; - DEBUG(dbgs() << "\n*** CURRENT ***: " << *cur << '\n'); - - assert(!cur->empty() && "Empty interval in unhandled set."); - - processActiveIntervals(cur->beginIndex()); - processInactiveIntervals(cur->beginIndex()); - - assert(TargetRegisterInfo::isVirtualRegister(cur->reg) && - "Can only allocate virtual registers!"); - - // Allocating a virtual register. try to find a free - // physical register or spill an interval (possibly this one) in order to - // assign it one. - assignRegOrStackSlotAtInterval(cur); - - DEBUG({ - printIntervals("active", active_.begin(), active_.end()); - printIntervals("inactive", inactive_.begin(), inactive_.end()); - }); - } - - // Expire any remaining active intervals - while (!active_.empty()) { - IntervalPtr &IP = active_.back(); - unsigned reg = IP.first->reg; - DEBUG(dbgs() << "\tinterval " << *IP.first << " expired\n"); - assert(TargetRegisterInfo::isVirtualRegister(reg) && - "Can only allocate virtual registers!"); - reg = vrm_->getPhys(reg); - delRegUse(reg); - active_.pop_back(); - } - - // Expire any remaining inactive intervals - DEBUG({ - for (IntervalPtrs::reverse_iterator - i = inactive_.rbegin(); i != inactive_.rend(); ++i) - dbgs() << "\tinterval " << *i->first << " expired\n"; - }); - inactive_.clear(); - - // Add live-ins to every BB except for entry. Also perform trivial coalescing. - MachineFunction::iterator EntryMBB = mf_->begin(); - SmallVector<MachineBasicBlock*, 8> LiveInMBBs; - for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i) { - LiveInterval &cur = *i->second; - unsigned Reg = 0; - bool isPhys = TargetRegisterInfo::isPhysicalRegister(cur.reg); - if (isPhys) - Reg = cur.reg; - else if (vrm_->isAssignedReg(cur.reg)) - Reg = attemptTrivialCoalescing(cur, vrm_->getPhys(cur.reg)); - if (!Reg) - continue; - // Ignore splited live intervals. - if (!isPhys && vrm_->getPreSplitReg(cur.reg)) - continue; - - for (LiveInterval::Ranges::const_iterator I = cur.begin(), E = cur.end(); - I != E; ++I) { - const LiveRange &LR = *I; - if (li_->findLiveInMBBs(LR.start, LR.end, LiveInMBBs)) { - for (unsigned i = 0, e = LiveInMBBs.size(); i != e; ++i) - if (LiveInMBBs[i] != EntryMBB) { - assert(TargetRegisterInfo::isPhysicalRegister(Reg) && - "Adding a virtual register to livein set?"); - LiveInMBBs[i]->addLiveIn(Reg); - } - LiveInMBBs.clear(); - } - } - } - - DEBUG(dbgs() << *vrm_); - - // Look for physical registers that end up not being allocated even though - // register allocator had to spill other registers in its register class. - if (!vrm_->FindUnusedRegisters(li_)) - return; -} - -/// processActiveIntervals - expire old intervals and move non-overlapping ones -/// to the inactive list. -void RALinScan::processActiveIntervals(SlotIndex CurPoint) -{ - DEBUG(dbgs() << "\tprocessing active intervals:\n"); - - for (unsigned i = 0, e = active_.size(); i != e; ++i) { - LiveInterval *Interval = active_[i].first; - LiveInterval::iterator IntervalPos = active_[i].second; - unsigned reg = Interval->reg; - - IntervalPos = Interval->advanceTo(IntervalPos, CurPoint); - - if (IntervalPos == Interval->end()) { // Remove expired intervals. - DEBUG(dbgs() << "\t\tinterval " << *Interval << " expired\n"); - assert(TargetRegisterInfo::isVirtualRegister(reg) && - "Can only allocate virtual registers!"); - reg = vrm_->getPhys(reg); - delRegUse(reg); - - // Pop off the end of the list. - active_[i] = active_.back(); - active_.pop_back(); - --i; --e; - - } else if (IntervalPos->start > CurPoint) { - // Move inactive intervals to inactive list. - DEBUG(dbgs() << "\t\tinterval " << *Interval << " inactive\n"); - assert(TargetRegisterInfo::isVirtualRegister(reg) && - "Can only allocate virtual registers!"); - reg = vrm_->getPhys(reg); - delRegUse(reg); - // add to inactive. - inactive_.push_back(std::make_pair(Interval, IntervalPos)); - - // Pop off the end of the list. - active_[i] = active_.back(); - active_.pop_back(); - --i; --e; - } else { - // Otherwise, just update the iterator position. - active_[i].second = IntervalPos; - } - } -} - -/// processInactiveIntervals - expire old intervals and move overlapping -/// ones to the active list. -void RALinScan::processInactiveIntervals(SlotIndex CurPoint) -{ - DEBUG(dbgs() << "\tprocessing inactive intervals:\n"); - - for (unsigned i = 0, e = inactive_.size(); i != e; ++i) { - LiveInterval *Interval = inactive_[i].first; - LiveInterval::iterator IntervalPos = inactive_[i].second; - unsigned reg = Interval->reg; - - IntervalPos = Interval->advanceTo(IntervalPos, CurPoint); - - if (IntervalPos == Interval->end()) { // remove expired intervals. - DEBUG(dbgs() << "\t\tinterval " << *Interval << " expired\n"); - - // Pop off the end of the list. - inactive_[i] = inactive_.back(); - inactive_.pop_back(); - --i; --e; - } else if (IntervalPos->start <= CurPoint) { - // move re-activated intervals in active list - DEBUG(dbgs() << "\t\tinterval " << *Interval << " active\n"); - assert(TargetRegisterInfo::isVirtualRegister(reg) && - "Can only allocate virtual registers!"); - reg = vrm_->getPhys(reg); - addRegUse(reg); - // add to active - active_.push_back(std::make_pair(Interval, IntervalPos)); - - // Pop off the end of the list. - inactive_[i] = inactive_.back(); - inactive_.pop_back(); - --i; --e; - } else { - // Otherwise, just update the iterator position. - inactive_[i].second = IntervalPos; - } - } -} - -/// updateSpillWeights - updates the spill weights of the specifed physical -/// register and its weight. -void RALinScan::updateSpillWeights(std::vector<float> &Weights, - unsigned reg, float weight, - const TargetRegisterClass *RC) { - SmallSet<unsigned, 4> Processed; - SmallSet<unsigned, 4> SuperAdded; - SmallVector<unsigned, 4> Supers; - Weights[reg] += weight; - Processed.insert(reg); - for (const unsigned* as = tri_->getAliasSet(reg); *as; ++as) { - Weights[*as] += weight; - Processed.insert(*as); - if (tri_->isSubRegister(*as, reg) && - SuperAdded.insert(*as) && - RC->contains(*as)) { - Supers.push_back(*as); - } - } - - // If the alias is a super-register, and the super-register is in the - // register class we are trying to allocate. Then add the weight to all - // sub-registers of the super-register even if they are not aliases. - // e.g. allocating for GR32, bh is not used, updating bl spill weight. - // bl should get the same spill weight otherwise it will be chosen - // as a spill candidate since spilling bh doesn't make ebx available. - for (unsigned i = 0, e = Supers.size(); i != e; ++i) { - for (const unsigned *sr = tri_->getSubRegisters(Supers[i]); *sr; ++sr) - if (!Processed.count(*sr)) - Weights[*sr] += weight; - } -} - -static -RALinScan::IntervalPtrs::iterator -FindIntervalInVector(RALinScan::IntervalPtrs &IP, LiveInterval *LI) { - for (RALinScan::IntervalPtrs::iterator I = IP.begin(), E = IP.end(); - I != E; ++I) - if (I->first == LI) return I; - return IP.end(); -} - -static void RevertVectorIteratorsTo(RALinScan::IntervalPtrs &V, - SlotIndex Point){ - for (unsigned i = 0, e = V.size(); i != e; ++i) { - RALinScan::IntervalPtr &IP = V[i]; - LiveInterval::iterator I = std::upper_bound(IP.first->begin(), - IP.second, Point); - if (I != IP.first->begin()) --I; - IP.second = I; - } -} - -/// getConflictWeight - Return the number of conflicts between cur -/// live interval and defs and uses of Reg weighted by loop depthes. -static -float getConflictWeight(LiveInterval *cur, unsigned Reg, LiveIntervals *li_, - MachineRegisterInfo *mri_, - MachineLoopInfo *loopInfo) { - float Conflicts = 0; - for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(Reg), - E = mri_->reg_end(); I != E; ++I) { - MachineInstr *MI = &*I; - if (cur->liveAt(li_->getInstructionIndex(MI))) { - unsigned loopDepth = loopInfo->getLoopDepth(MI->getParent()); - Conflicts += std::pow(10.0f, (float)loopDepth); - } - } - return Conflicts; -} - -/// findIntervalsToSpill - Determine the intervals to spill for the -/// specified interval. It's passed the physical registers whose spill -/// weight is the lowest among all the registers whose live intervals -/// conflict with the interval. -void RALinScan::findIntervalsToSpill(LiveInterval *cur, - std::vector<std::pair<unsigned,float> > &Candidates, - unsigned NumCands, - SmallVector<LiveInterval*, 8> &SpillIntervals) { - // We have figured out the *best* register to spill. But there are other - // registers that are pretty good as well (spill weight within 3%). Spill - // the one that has fewest defs and uses that conflict with cur. - float Conflicts[3] = { 0.0f, 0.0f, 0.0f }; - SmallVector<LiveInterval*, 8> SLIs[3]; - - DEBUG({ - dbgs() << "\tConsidering " << NumCands << " candidates: "; - for (unsigned i = 0; i != NumCands; ++i) - dbgs() << tri_->getName(Candidates[i].first) << " "; - dbgs() << "\n"; - }); - - // Calculate the number of conflicts of each candidate. - for (IntervalPtrs::iterator i = active_.begin(); i != active_.end(); ++i) { - unsigned Reg = i->first->reg; - unsigned PhysReg = vrm_->getPhys(Reg); - if (!cur->overlapsFrom(*i->first, i->second)) - continue; - for (unsigned j = 0; j < NumCands; ++j) { - unsigned Candidate = Candidates[j].first; - if (tri_->regsOverlap(PhysReg, Candidate)) { - if (NumCands > 1) - Conflicts[j] += getConflictWeight(cur, Reg, li_, mri_, loopInfo); - SLIs[j].push_back(i->first); - } - } - } - - for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end(); ++i){ - unsigned Reg = i->first->reg; - unsigned PhysReg = vrm_->getPhys(Reg); - if (!cur->overlapsFrom(*i->first, i->second-1)) - continue; - for (unsigned j = 0; j < NumCands; ++j) { - unsigned Candidate = Candidates[j].first; - if (tri_->regsOverlap(PhysReg, Candidate)) { - if (NumCands > 1) - Conflicts[j] += getConflictWeight(cur, Reg, li_, mri_, loopInfo); - SLIs[j].push_back(i->first); - } - } - } - - // Which is the best candidate? - unsigned BestCandidate = 0; - float MinConflicts = Conflicts[0]; - for (unsigned i = 1; i != NumCands; ++i) { - if (Conflicts[i] < MinConflicts) { - BestCandidate = i; - MinConflicts = Conflicts[i]; - } - } - - std::copy(SLIs[BestCandidate].begin(), SLIs[BestCandidate].end(), - std::back_inserter(SpillIntervals)); -} - -namespace { - struct WeightCompare { - private: - const RALinScan &Allocator; - - public: - WeightCompare(const RALinScan &Alloc) : Allocator(Alloc) {} - - typedef std::pair<unsigned, float> RegWeightPair; - bool operator()(const RegWeightPair &LHS, const RegWeightPair &RHS) const { - return LHS.second < RHS.second && !Allocator.isRecentlyUsed(LHS.first); - } - }; -} - -static bool weightsAreClose(float w1, float w2) { - if (!NewHeuristic) - return false; - - float diff = w1 - w2; - if (diff <= 0.02f) // Within 0.02f - return true; - return (diff / w2) <= 0.05f; // Within 5%. -} - -LiveInterval *RALinScan::hasNextReloadInterval(LiveInterval *cur) { - DenseMap<unsigned, unsigned>::iterator I = NextReloadMap.find(cur->reg); - if (I == NextReloadMap.end()) - return 0; - return &li_->getInterval(I->second); -} - -void RALinScan::DowngradeRegister(LiveInterval *li, unsigned Reg) { - for (const unsigned *AS = tri_->getOverlaps(Reg); *AS; ++AS) { - bool isNew = DowngradedRegs.insert(*AS); - (void)isNew; // Silence compiler warning. - assert(isNew && "Multiple reloads holding the same register?"); - DowngradeMap.insert(std::make_pair(li->reg, *AS)); - } - ++NumDowngrade; -} - -void RALinScan::UpgradeRegister(unsigned Reg) { - if (Reg) { - DowngradedRegs.erase(Reg); - for (const unsigned *AS = tri_->getAliasSet(Reg); *AS; ++AS) - DowngradedRegs.erase(*AS); - } -} - -namespace { - struct LISorter { - bool operator()(LiveInterval* A, LiveInterval* B) { - return A->beginIndex() < B->beginIndex(); - } - }; -} - -/// assignRegOrStackSlotAtInterval - assign a register if one is available, or -/// spill. -void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur) { - const TargetRegisterClass *RC = mri_->getRegClass(cur->reg); - DEBUG(dbgs() << "\tallocating current interval from " - << RC->getName() << ": "); - - // This is an implicitly defined live interval, just assign any register. - if (cur->empty()) { - unsigned physReg = vrm_->getRegAllocPref(cur->reg); - if (!physReg) - physReg = getFirstNonReservedPhysReg(RC); - DEBUG(dbgs() << tri_->getName(physReg) << '\n'); - // Note the register is not really in use. - vrm_->assignVirt2Phys(cur->reg, physReg); - return; - } - - backUpRegUses(); - - std::vector<std::pair<unsigned, float> > SpillWeightsToAdd; - SlotIndex StartPosition = cur->beginIndex(); - const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC); - - // If start of this live interval is defined by a move instruction and its - // source is assigned a physical register that is compatible with the target - // register class, then we should try to assign it the same register. - // This can happen when the move is from a larger register class to a smaller - // one, e.g. X86::mov32to32_. These move instructions are not coalescable. - if (!vrm_->getRegAllocPref(cur->reg) && cur->hasAtLeastOneValue()) { - VNInfo *vni = cur->begin()->valno; - if (!vni->isUnused() && vni->def.isValid()) { - MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def); - if (CopyMI && CopyMI->isCopy()) { - unsigned DstSubReg = CopyMI->getOperand(0).getSubReg(); - unsigned SrcReg = CopyMI->getOperand(1).getReg(); - unsigned SrcSubReg = CopyMI->getOperand(1).getSubReg(); - unsigned Reg = 0; - if (TargetRegisterInfo::isPhysicalRegister(SrcReg)) - Reg = SrcReg; - else if (vrm_->isAssignedReg(SrcReg)) - Reg = vrm_->getPhys(SrcReg); - if (Reg) { - if (SrcSubReg) - Reg = tri_->getSubReg(Reg, SrcSubReg); - if (DstSubReg) - Reg = tri_->getMatchingSuperReg(Reg, DstSubReg, RC); - if (Reg && allocatableRegs_[Reg] && RC->contains(Reg)) - mri_->setRegAllocationHint(cur->reg, 0, Reg); - } - } - } - } - - // For every interval in inactive we overlap with, mark the - // register as not free and update spill weights. - for (IntervalPtrs::const_iterator i = inactive_.begin(), - e = inactive_.end(); i != e; ++i) { - unsigned Reg = i->first->reg; - assert(TargetRegisterInfo::isVirtualRegister(Reg) && - "Can only allocate virtual registers!"); - const TargetRegisterClass *RegRC = mri_->getRegClass(Reg); - // If this is not in a related reg class to the register we're allocating, - // don't check it. - if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader && - cur->overlapsFrom(*i->first, i->second-1)) { - Reg = vrm_->getPhys(Reg); - addRegUse(Reg); - SpillWeightsToAdd.push_back(std::make_pair(Reg, i->first->weight)); - } - } - - // Speculatively check to see if we can get a register right now. If not, - // we know we won't be able to by adding more constraints. If so, we can - // check to see if it is valid. Doing an exhaustive search of the fixed_ list - // is very bad (it contains all callee clobbered registers for any functions - // with a call), so we want to avoid doing that if possible. - unsigned physReg = getFreePhysReg(cur); - unsigned BestPhysReg = physReg; - if (physReg) { - // We got a register. However, if it's in the fixed_ list, we might - // conflict with it. Check to see if we conflict with it or any of its - // aliases. - SmallSet<unsigned, 8> RegAliases; - for (const unsigned *AS = tri_->getAliasSet(physReg); *AS; ++AS) - RegAliases.insert(*AS); - - bool ConflictsWithFixed = false; - for (unsigned i = 0, e = fixed_.size(); i != e; ++i) { - IntervalPtr &IP = fixed_[i]; - if (physReg == IP.first->reg || RegAliases.count(IP.first->reg)) { - // Okay, this reg is on the fixed list. Check to see if we actually - // conflict. - LiveInterval *I = IP.first; - if (I->endIndex() > StartPosition) { - LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition); - IP.second = II; - if (II != I->begin() && II->start > StartPosition) - --II; - if (cur->overlapsFrom(*I, II)) { - ConflictsWithFixed = true; - break; - } - } - } - } - - // Okay, the register picked by our speculative getFreePhysReg call turned - // out to be in use. Actually add all of the conflicting fixed registers to - // regUse_ so we can do an accurate query. - if (ConflictsWithFixed) { - // For every interval in fixed we overlap with, mark the register as not - // free and update spill weights. - for (unsigned i = 0, e = fixed_.size(); i != e; ++i) { - IntervalPtr &IP = fixed_[i]; - LiveInterval *I = IP.first; - - const TargetRegisterClass *RegRC = OneClassForEachPhysReg[I->reg]; - if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader && - I->endIndex() > StartPosition) { - LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition); - IP.second = II; - if (II != I->begin() && II->start > StartPosition) - --II; - if (cur->overlapsFrom(*I, II)) { - unsigned reg = I->reg; - addRegUse(reg); - SpillWeightsToAdd.push_back(std::make_pair(reg, I->weight)); - } - } - } - - // Using the newly updated regUse_ object, which includes conflicts in the - // future, see if there are any registers available. - physReg = getFreePhysReg(cur); - } - } - - // Restore the physical register tracker, removing information about the - // future. - restoreRegUses(); - - // If we find a free register, we are done: assign this virtual to - // the free physical register and add this interval to the active - // list. - if (physReg) { - DEBUG(dbgs() << tri_->getName(physReg) << '\n'); - assert(RC->contains(physReg) && "Invalid candidate"); - vrm_->assignVirt2Phys(cur->reg, physReg); - addRegUse(physReg); - active_.push_back(std::make_pair(cur, cur->begin())); - handled_.push_back(cur); - - // Remember physReg for avoiding a write-after-write hazard in the next - // instruction. - if (AvoidWAWHazard && - tri_->avoidWriteAfterWrite(mri_->getRegClass(cur->reg))) - avoidWAW_ = physReg; - - // "Upgrade" the physical register since it has been allocated. - UpgradeRegister(physReg); - if (LiveInterval *NextReloadLI = hasNextReloadInterval(cur)) { - // "Downgrade" physReg to try to keep physReg from being allocated until - // the next reload from the same SS is allocated. - mri_->setRegAllocationHint(NextReloadLI->reg, 0, physReg); - DowngradeRegister(cur, physReg); - } - return; - } - DEBUG(dbgs() << "no free registers\n"); - - // Compile the spill weights into an array that is better for scanning. - std::vector<float> SpillWeights(tri_->getNumRegs(), 0.0f); - for (std::vector<std::pair<unsigned, float> >::iterator - I = SpillWeightsToAdd.begin(), E = SpillWeightsToAdd.end(); I != E; ++I) - updateSpillWeights(SpillWeights, I->first, I->second, RC); - - // for each interval in active, update spill weights. - for (IntervalPtrs::const_iterator i = active_.begin(), e = active_.end(); - i != e; ++i) { - unsigned reg = i->first->reg; - assert(TargetRegisterInfo::isVirtualRegister(reg) && - "Can only allocate virtual registers!"); - reg = vrm_->getPhys(reg); - updateSpillWeights(SpillWeights, reg, i->first->weight, RC); - } - - DEBUG(dbgs() << "\tassigning stack slot at interval "<< *cur << ":\n"); - - // Find a register to spill. - float minWeight = HUGE_VALF; - unsigned minReg = 0; - - bool Found = false; - std::vector<std::pair<unsigned,float> > RegsWeights; - ArrayRef<unsigned> Order = RegClassInfo.getOrder(RC); - if (!minReg || SpillWeights[minReg] == HUGE_VALF) - for (unsigned i = 0; i != Order.size(); ++i) { - unsigned reg = Order[i]; - float regWeight = SpillWeights[reg]; - // Skip recently allocated registers and reserved registers. - if (minWeight > regWeight && !isRecentlyUsed(reg)) - Found = true; - RegsWeights.push_back(std::make_pair(reg, regWeight)); - } - - // If we didn't find a register that is spillable, try aliases? - if (!Found) { - for (unsigned i = 0; i != Order.size(); ++i) { - unsigned reg = Order[i]; - // No need to worry about if the alias register size < regsize of RC. - // We are going to spill all registers that alias it anyway. - for (const unsigned* as = tri_->getAliasSet(reg); *as; ++as) - RegsWeights.push_back(std::make_pair(*as, SpillWeights[*as])); - } - } - - // Sort all potential spill candidates by weight. - std::sort(RegsWeights.begin(), RegsWeights.end(), WeightCompare(*this)); - minReg = RegsWeights[0].first; - minWeight = RegsWeights[0].second; - if (minWeight == HUGE_VALF) { - // All registers must have inf weight. Just grab one! - minReg = BestPhysReg ? BestPhysReg : getFirstNonReservedPhysReg(RC); - if (cur->weight == HUGE_VALF || - li_->getApproximateInstructionCount(*cur) == 0) { - // Spill a physical register around defs and uses. - if (li_->spillPhysRegAroundRegDefsUses(*cur, minReg, *vrm_)) { - // spillPhysRegAroundRegDefsUses may have invalidated iterator stored - // in fixed_. Reset them. - for (unsigned i = 0, e = fixed_.size(); i != e; ++i) { - IntervalPtr &IP = fixed_[i]; - LiveInterval *I = IP.first; - if (I->reg == minReg || tri_->isSubRegister(minReg, I->reg)) - IP.second = I->advanceTo(I->begin(), StartPosition); - } - - DowngradedRegs.clear(); - assignRegOrStackSlotAtInterval(cur); - } else { - assert(false && "Ran out of registers during register allocation!"); - report_fatal_error("Ran out of registers during register allocation!"); - } - return; - } - } - - // Find up to 3 registers to consider as spill candidates. - unsigned LastCandidate = RegsWeights.size() >= 3 ? 3 : 1; - while (LastCandidate > 1) { - if (weightsAreClose(RegsWeights[LastCandidate-1].second, minWeight)) - break; - --LastCandidate; - } - - DEBUG({ - dbgs() << "\t\tregister(s) with min weight(s): "; - - for (unsigned i = 0; i != LastCandidate; ++i) - dbgs() << tri_->getName(RegsWeights[i].first) - << " (" << RegsWeights[i].second << ")\n"; - }); - - // If the current has the minimum weight, we need to spill it and - // add any added intervals back to unhandled, and restart - // linearscan. - if (cur->weight != HUGE_VALF && cur->weight <= minWeight) { - DEBUG(dbgs() << "\t\t\tspilling(c): " << *cur << '\n'); - SmallVector<LiveInterval*, 8> added; - LiveRangeEdit LRE(*cur, added); - spiller_->spill(LRE); - - std::sort(added.begin(), added.end(), LISorter()); - if (added.empty()) - return; // Early exit if all spills were folded. - - // Merge added with unhandled. Note that we have already sorted - // intervals returned by addIntervalsForSpills by their starting - // point. - // This also update the NextReloadMap. That is, it adds mapping from a - // register defined by a reload from SS to the next reload from SS in the - // same basic block. - MachineBasicBlock *LastReloadMBB = 0; - LiveInterval *LastReload = 0; - int LastReloadSS = VirtRegMap::NO_STACK_SLOT; - for (unsigned i = 0, e = added.size(); i != e; ++i) { - LiveInterval *ReloadLi = added[i]; - if (ReloadLi->weight == HUGE_VALF && - li_->getApproximateInstructionCount(*ReloadLi) == 0) { - SlotIndex ReloadIdx = ReloadLi->beginIndex(); - MachineBasicBlock *ReloadMBB = li_->getMBBFromIndex(ReloadIdx); - int ReloadSS = vrm_->getStackSlot(ReloadLi->reg); - if (LastReloadMBB == ReloadMBB && LastReloadSS == ReloadSS) { - // Last reload of same SS is in the same MBB. We want to try to - // allocate both reloads the same register and make sure the reg - // isn't clobbered in between if at all possible. - assert(LastReload->beginIndex() < ReloadIdx); - NextReloadMap.insert(std::make_pair(LastReload->reg, ReloadLi->reg)); - } - LastReloadMBB = ReloadMBB; - LastReload = ReloadLi; - LastReloadSS = ReloadSS; - } - unhandled_.push(ReloadLi); - } - return; - } - - ++NumBacktracks; - - // Push the current interval back to unhandled since we are going - // to re-run at least this iteration. Since we didn't modify it it - // should go back right in the front of the list - unhandled_.push(cur); - - assert(TargetRegisterInfo::isPhysicalRegister(minReg) && - "did not choose a register to spill?"); - - // We spill all intervals aliasing the register with - // minimum weight, rollback to the interval with the earliest - // start point and let the linear scan algorithm run again - SmallVector<LiveInterval*, 8> spillIs; - - // Determine which intervals have to be spilled. - findIntervalsToSpill(cur, RegsWeights, LastCandidate, spillIs); - - // Set of spilled vregs (used later to rollback properly) - SmallSet<unsigned, 8> spilled; - - // The earliest start of a Spilled interval indicates up to where - // in handled we need to roll back - assert(!spillIs.empty() && "No spill intervals?"); - SlotIndex earliestStart = spillIs[0]->beginIndex(); - - // Spill live intervals of virtual regs mapped to the physical register we - // want to clear (and its aliases). We only spill those that overlap with the - // current interval as the rest do not affect its allocation. we also keep - // track of the earliest start of all spilled live intervals since this will - // mark our rollback point. - SmallVector<LiveInterval*, 8> added; - while (!spillIs.empty()) { - LiveInterval *sli = spillIs.back(); - spillIs.pop_back(); - DEBUG(dbgs() << "\t\t\tspilling(a): " << *sli << '\n'); - if (sli->beginIndex() < earliestStart) - earliestStart = sli->beginIndex(); - LiveRangeEdit LRE(*sli, added, 0, &spillIs); - spiller_->spill(LRE); - spilled.insert(sli->reg); - } - - // Include any added intervals in earliestStart. - for (unsigned i = 0, e = added.size(); i != e; ++i) { - SlotIndex SI = added[i]->beginIndex(); - if (SI < earliestStart) - earliestStart = SI; - } - - DEBUG(dbgs() << "\t\trolling back to: " << earliestStart << '\n'); - - // Scan handled in reverse order up to the earliest start of a - // spilled live interval and undo each one, restoring the state of - // unhandled. - while (!handled_.empty()) { - LiveInterval* i = handled_.back(); - // If this interval starts before t we are done. - if (!i->empty() && i->beginIndex() < earliestStart) - break; - DEBUG(dbgs() << "\t\t\tundo changes for: " << *i << '\n'); - handled_.pop_back(); - - // When undoing a live interval allocation we must know if it is active or - // inactive to properly update regUse_ and the VirtRegMap. - IntervalPtrs::iterator it; - if ((it = FindIntervalInVector(active_, i)) != active_.end()) { - active_.erase(it); - assert(!TargetRegisterInfo::isPhysicalRegister(i->reg)); - if (!spilled.count(i->reg)) - unhandled_.push(i); - delRegUse(vrm_->getPhys(i->reg)); - vrm_->clearVirt(i->reg); - } else if ((it = FindIntervalInVector(inactive_, i)) != inactive_.end()) { - inactive_.erase(it); - assert(!TargetRegisterInfo::isPhysicalRegister(i->reg)); - if (!spilled.count(i->reg)) - unhandled_.push(i); - vrm_->clearVirt(i->reg); - } else { - assert(TargetRegisterInfo::isVirtualRegister(i->reg) && - "Can only allocate virtual registers!"); - vrm_->clearVirt(i->reg); - unhandled_.push(i); - } - - DenseMap<unsigned, unsigned>::iterator ii = DowngradeMap.find(i->reg); - if (ii == DowngradeMap.end()) - // It interval has a preference, it must be defined by a copy. Clear the - // preference now since the source interval allocation may have been - // undone as well. - mri_->setRegAllocationHint(i->reg, 0, 0); - else { - UpgradeRegister(ii->second); - } - } - - // Rewind the iterators in the active, inactive, and fixed lists back to the - // point we reverted to. - RevertVectorIteratorsTo(active_, earliestStart); - RevertVectorIteratorsTo(inactive_, earliestStart); - RevertVectorIteratorsTo(fixed_, earliestStart); - - // Scan the rest and undo each interval that expired after t and - // insert it in active (the next iteration of the algorithm will - // put it in inactive if required) - for (unsigned i = 0, e = handled_.size(); i != e; ++i) { - LiveInterval *HI = handled_[i]; - if (!HI->expiredAt(earliestStart) && - HI->expiredAt(cur->beginIndex())) { - DEBUG(dbgs() << "\t\t\tundo changes for: " << *HI << '\n'); - active_.push_back(std::make_pair(HI, HI->begin())); - assert(!TargetRegisterInfo::isPhysicalRegister(HI->reg)); - addRegUse(vrm_->getPhys(HI->reg)); - } - } - - // Merge added with unhandled. - // This also update the NextReloadMap. That is, it adds mapping from a - // register defined by a reload from SS to the next reload from SS in the - // same basic block. - MachineBasicBlock *LastReloadMBB = 0; - LiveInterval *LastReload = 0; - int LastReloadSS = VirtRegMap::NO_STACK_SLOT; - std::sort(added.begin(), added.end(), LISorter()); - for (unsigned i = 0, e = added.size(); i != e; ++i) { - LiveInterval *ReloadLi = added[i]; - if (ReloadLi->weight == HUGE_VALF && - li_->getApproximateInstructionCount(*ReloadLi) == 0) { - SlotIndex ReloadIdx = ReloadLi->beginIndex(); - MachineBasicBlock *ReloadMBB = li_->getMBBFromIndex(ReloadIdx); - int ReloadSS = vrm_->getStackSlot(ReloadLi->reg); - if (LastReloadMBB == ReloadMBB && LastReloadSS == ReloadSS) { - // Last reload of same SS is in the same MBB. We want to try to - // allocate both reloads the same register and make sure the reg - // isn't clobbered in between if at all possible. - assert(LastReload->beginIndex() < ReloadIdx); - NextReloadMap.insert(std::make_pair(LastReload->reg, ReloadLi->reg)); - } - LastReloadMBB = ReloadMBB; - LastReload = ReloadLi; - LastReloadSS = ReloadSS; - } - unhandled_.push(ReloadLi); - } -} - -unsigned RALinScan::getFreePhysReg(LiveInterval* cur, - const TargetRegisterClass *RC, - unsigned MaxInactiveCount, - SmallVector<unsigned, 256> &inactiveCounts, - bool SkipDGRegs) { - unsigned FreeReg = 0; - unsigned FreeRegInactiveCount = 0; - - std::pair<unsigned, unsigned> Hint = mri_->getRegAllocationHint(cur->reg); - // Resolve second part of the hint (if possible) given the current allocation. - unsigned physReg = Hint.second; - if (TargetRegisterInfo::isVirtualRegister(physReg) && vrm_->hasPhys(physReg)) - physReg = vrm_->getPhys(physReg); - - ArrayRef<unsigned> Order; - if (Hint.first) - Order = tri_->getRawAllocationOrder(RC, Hint.first, physReg, *mf_); - else - Order = RegClassInfo.getOrder(RC); - - assert(!Order.empty() && "No allocatable register in this register class!"); - - // Scan for the first available register. - for (unsigned i = 0; i != Order.size(); ++i) { - unsigned Reg = Order[i]; - // Ignore "downgraded" registers. - if (SkipDGRegs && DowngradedRegs.count(Reg)) - continue; - // Skip reserved registers. - if (reservedRegs_.test(Reg)) - continue; - // Skip recently allocated registers. - if (isRegAvail(Reg) && (!SkipDGRegs || !isRecentlyUsed(Reg))) { - FreeReg = Reg; - if (FreeReg < inactiveCounts.size()) - FreeRegInactiveCount = inactiveCounts[FreeReg]; - else - FreeRegInactiveCount = 0; - break; - } - } - - // If there are no free regs, or if this reg has the max inactive count, - // return this register. - if (FreeReg == 0 || FreeRegInactiveCount == MaxInactiveCount) { - // Remember what register we picked so we can skip it next time. - if (FreeReg != 0) recordRecentlyUsed(FreeReg); - return FreeReg; - } - - // Continue scanning the registers, looking for the one with the highest - // inactive count. Alkis found that this reduced register pressure very - // slightly on X86 (in rev 1.94 of this file), though this should probably be - // reevaluated now. - for (unsigned i = 0; i != Order.size(); ++i) { - unsigned Reg = Order[i]; - // Ignore "downgraded" registers. - if (SkipDGRegs && DowngradedRegs.count(Reg)) - continue; - // Skip reserved registers. - if (reservedRegs_.test(Reg)) - continue; - if (isRegAvail(Reg) && Reg < inactiveCounts.size() && - FreeRegInactiveCount < inactiveCounts[Reg] && - (!SkipDGRegs || !isRecentlyUsed(Reg))) { - FreeReg = Reg; - FreeRegInactiveCount = inactiveCounts[Reg]; - if (FreeRegInactiveCount == MaxInactiveCount) - break; // We found the one with the max inactive count. - } - } - - // Remember what register we picked so we can skip it next time. - recordRecentlyUsed(FreeReg); - - return FreeReg; -} - -/// getFreePhysReg - return a free physical register for this virtual register -/// interval if we have one, otherwise return 0. -unsigned RALinScan::getFreePhysReg(LiveInterval *cur) { - SmallVector<unsigned, 256> inactiveCounts; - unsigned MaxInactiveCount = 0; - - const TargetRegisterClass *RC = mri_->getRegClass(cur->reg); - const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC); - - for (IntervalPtrs::iterator i = inactive_.begin(), e = inactive_.end(); - i != e; ++i) { - unsigned reg = i->first->reg; - assert(TargetRegisterInfo::isVirtualRegister(reg) && - "Can only allocate virtual registers!"); - - // If this is not in a related reg class to the register we're allocating, - // don't check it. - const TargetRegisterClass *RegRC = mri_->getRegClass(reg); - if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader) { - reg = vrm_->getPhys(reg); - if (inactiveCounts.size() <= reg) - inactiveCounts.resize(reg+1); - ++inactiveCounts[reg]; - MaxInactiveCount = std::max(MaxInactiveCount, inactiveCounts[reg]); - } - } - - // If copy coalescer has assigned a "preferred" register, check if it's - // available first. - unsigned Preference = vrm_->getRegAllocPref(cur->reg); - if (Preference) { - DEBUG(dbgs() << "(preferred: " << tri_->getName(Preference) << ") "); - if (isRegAvail(Preference) && - RC->contains(Preference)) - return Preference; - } - - unsigned FreeReg = getFreePhysReg(cur, RC, MaxInactiveCount, inactiveCounts, - true); - if (FreeReg) - return FreeReg; - return getFreePhysReg(cur, RC, MaxInactiveCount, inactiveCounts, false); -} - -FunctionPass* llvm::createLinearScanRegisterAllocator() { - return new RALinScan(); -} |