diff options
Diffstat (limited to 'llvm/lib/CodeGen/RegAllocGreedy.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/RegAllocGreedy.cpp | 3266 |
1 files changed, 3266 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp new file mode 100644 index 000000000000..d27db678f02a --- /dev/null +++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp @@ -0,0 +1,3266 @@ +//===- RegAllocGreedy.cpp - greedy register allocator ---------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file defines the RAGreedy function pass for register allocation in +// optimized builds. +// +//===----------------------------------------------------------------------===// + +#include "AllocationOrder.h" +#include "InterferenceCache.h" +#include "LiveDebugVariables.h" +#include "RegAllocBase.h" +#include "SpillPlacement.h" +#include "Spiller.h" +#include "SplitKit.h" +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/BitVector.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/IndexedMap.h" +#include "llvm/ADT/MapVector.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/StringRef.h" +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/OptimizationRemarkEmitter.h" +#include "llvm/CodeGen/CalcSpillWeights.h" +#include "llvm/CodeGen/EdgeBundles.h" +#include "llvm/CodeGen/LiveInterval.h" +#include "llvm/CodeGen/LiveIntervalUnion.h" +#include "llvm/CodeGen/LiveIntervals.h" +#include "llvm/CodeGen/LiveRangeEdit.h" +#include "llvm/CodeGen/LiveRegMatrix.h" +#include "llvm/CodeGen/LiveStacks.h" +#include "llvm/CodeGen/MachineBasicBlock.h" +#include "llvm/CodeGen/MachineBlockFrequencyInfo.h" +#include "llvm/CodeGen/MachineDominators.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/CodeGen/MachineInstr.h" +#include "llvm/CodeGen/MachineLoopInfo.h" +#include "llvm/CodeGen/MachineOperand.h" +#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/RegAllocRegistry.h" +#include "llvm/CodeGen/RegisterClassInfo.h" +#include "llvm/CodeGen/SlotIndexes.h" +#include "llvm/CodeGen/TargetInstrInfo.h" +#include "llvm/CodeGen/TargetRegisterInfo.h" +#include "llvm/CodeGen/TargetSubtargetInfo.h" +#include "llvm/CodeGen/VirtRegMap.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/MC/MCRegisterInfo.h" +#include "llvm/Pass.h" +#include "llvm/Support/BlockFrequency.h" +#include "llvm/Support/BranchProbability.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/MathExtras.h" +#include "llvm/Support/Timer.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetMachine.h" +#include <algorithm> +#include <cassert> +#include <cstdint> +#include <memory> +#include <queue> +#include <tuple> +#include <utility> + +using namespace llvm; + +#define DEBUG_TYPE "regalloc" + +STATISTIC(NumGlobalSplits, "Number of split global live ranges"); +STATISTIC(NumLocalSplits, "Number of split local live ranges"); +STATISTIC(NumEvicted, "Number of interferences evicted"); + +static cl::opt<SplitEditor::ComplementSpillMode> SplitSpillMode( + "split-spill-mode", cl::Hidden, + cl::desc("Spill mode for splitting live ranges"), + cl::values(clEnumValN(SplitEditor::SM_Partition, "default", "Default"), + clEnumValN(SplitEditor::SM_Size, "size", "Optimize for size"), + clEnumValN(SplitEditor::SM_Speed, "speed", "Optimize for speed")), + cl::init(SplitEditor::SM_Speed)); + +static cl::opt<unsigned> +LastChanceRecoloringMaxDepth("lcr-max-depth", cl::Hidden, + cl::desc("Last chance recoloring max depth"), + cl::init(5)); + +static cl::opt<unsigned> LastChanceRecoloringMaxInterference( + "lcr-max-interf", cl::Hidden, + cl::desc("Last chance recoloring maximum number of considered" + " interference at a time"), + cl::init(8)); + +static cl::opt<bool> ExhaustiveSearch( + "exhaustive-register-search", cl::NotHidden, + cl::desc("Exhaustive Search for registers bypassing the depth " + "and interference cutoffs of last chance recoloring"), + cl::Hidden); + +static cl::opt<bool> EnableLocalReassignment( + "enable-local-reassign", cl::Hidden, + cl::desc("Local reassignment can yield better allocation decisions, but " + "may be compile time intensive"), + cl::init(false)); + +static cl::opt<bool> EnableDeferredSpilling( + "enable-deferred-spilling", cl::Hidden, + cl::desc("Instead of spilling a variable right away, defer the actual " + "code insertion to the end of the allocation. That way the " + "allocator might still find a suitable coloring for this " + "variable because of other evicted variables."), + cl::init(false)); + +static cl::opt<unsigned> + HugeSizeForSplit("huge-size-for-split", cl::Hidden, + cl::desc("A threshold of live range size which may cause " + "high compile time cost in global splitting."), + cl::init(5000)); + +// FIXME: Find a good default for this flag and remove the flag. +static cl::opt<unsigned> +CSRFirstTimeCost("regalloc-csr-first-time-cost", + cl::desc("Cost for first time use of callee-saved register."), + cl::init(0), cl::Hidden); + +static cl::opt<bool> ConsiderLocalIntervalCost( + "consider-local-interval-cost", cl::Hidden, + cl::desc("Consider the cost of local intervals created by a split " + "candidate when choosing the best split candidate."), + cl::init(false)); + +static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator", + createGreedyRegisterAllocator); + +namespace { + +class RAGreedy : public MachineFunctionPass, + public RegAllocBase, + private LiveRangeEdit::Delegate { + // Convenient shortcuts. + using PQueue = std::priority_queue<std::pair<unsigned, unsigned>>; + using SmallLISet = SmallPtrSet<LiveInterval *, 4>; + using SmallVirtRegSet = SmallSet<unsigned, 16>; + + // context + MachineFunction *MF; + + // Shortcuts to some useful interface. + const TargetInstrInfo *TII; + const TargetRegisterInfo *TRI; + RegisterClassInfo RCI; + + // analyses + SlotIndexes *Indexes; + MachineBlockFrequencyInfo *MBFI; + MachineDominatorTree *DomTree; + MachineLoopInfo *Loops; + MachineOptimizationRemarkEmitter *ORE; + EdgeBundles *Bundles; + SpillPlacement *SpillPlacer; + LiveDebugVariables *DebugVars; + AliasAnalysis *AA; + + // state + std::unique_ptr<Spiller> SpillerInstance; + PQueue Queue; + unsigned NextCascade; + + // Live ranges pass through a number of stages as we try to allocate them. + // Some of the stages may also create new live ranges: + // + // - Region splitting. + // - Per-block splitting. + // - Local splitting. + // - Spilling. + // + // Ranges produced by one of the stages skip the previous stages when they are + // dequeued. This improves performance because we can skip interference checks + // that are unlikely to give any results. It also guarantees that the live + // range splitting algorithm terminates, something that is otherwise hard to + // ensure. + enum LiveRangeStage { + /// Newly created live range that has never been queued. + RS_New, + + /// Only attempt assignment and eviction. Then requeue as RS_Split. + RS_Assign, + + /// Attempt live range splitting if assignment is impossible. + RS_Split, + + /// Attempt more aggressive live range splitting that is guaranteed to make + /// progress. This is used for split products that may not be making + /// progress. + RS_Split2, + + /// Live range will be spilled. No more splitting will be attempted. + RS_Spill, + + + /// Live range is in memory. Because of other evictions, it might get moved + /// in a register in the end. + RS_Memory, + + /// There is nothing more we can do to this live range. Abort compilation + /// if it can't be assigned. + RS_Done + }; + + // Enum CutOffStage to keep a track whether the register allocation failed + // because of the cutoffs encountered in last chance recoloring. + // Note: This is used as bitmask. New value should be next power of 2. + enum CutOffStage { + // No cutoffs encountered + CO_None = 0, + + // lcr-max-depth cutoff encountered + CO_Depth = 1, + + // lcr-max-interf cutoff encountered + CO_Interf = 2 + }; + + uint8_t CutOffInfo; + +#ifndef NDEBUG + static const char *const StageName[]; +#endif + + // RegInfo - Keep additional information about each live range. + struct RegInfo { + LiveRangeStage Stage = RS_New; + + // Cascade - Eviction loop prevention. See canEvictInterference(). + unsigned Cascade = 0; + + RegInfo() = default; + }; + + IndexedMap<RegInfo, VirtReg2IndexFunctor> ExtraRegInfo; + + LiveRangeStage getStage(const LiveInterval &VirtReg) const { + return ExtraRegInfo[VirtReg.reg].Stage; + } + + void setStage(const LiveInterval &VirtReg, LiveRangeStage Stage) { + ExtraRegInfo.resize(MRI->getNumVirtRegs()); + ExtraRegInfo[VirtReg.reg].Stage = Stage; + } + + template<typename Iterator> + void setStage(Iterator Begin, Iterator End, LiveRangeStage NewStage) { + ExtraRegInfo.resize(MRI->getNumVirtRegs()); + for (;Begin != End; ++Begin) { + unsigned Reg = *Begin; + if (ExtraRegInfo[Reg].Stage == RS_New) + ExtraRegInfo[Reg].Stage = NewStage; + } + } + + /// Cost of evicting interference. + struct EvictionCost { + unsigned BrokenHints = 0; ///< Total number of broken hints. + float MaxWeight = 0; ///< Maximum spill weight evicted. + + EvictionCost() = default; + + bool isMax() const { return BrokenHints == ~0u; } + + void setMax() { BrokenHints = ~0u; } + + void setBrokenHints(unsigned NHints) { BrokenHints = NHints; } + + bool operator<(const EvictionCost &O) const { + return std::tie(BrokenHints, MaxWeight) < + std::tie(O.BrokenHints, O.MaxWeight); + } + }; + + /// EvictionTrack - Keeps track of past evictions in order to optimize region + /// split decision. + class EvictionTrack { + + public: + using EvictorInfo = + std::pair<unsigned /* evictor */, unsigned /* physreg */>; + using EvicteeInfo = llvm::DenseMap<unsigned /* evictee */, EvictorInfo>; + + private: + /// Each Vreg that has been evicted in the last stage of selectOrSplit will + /// be mapped to the evictor Vreg and the PhysReg it was evicted from. + EvicteeInfo Evictees; + + public: + /// Clear all eviction information. + void clear() { Evictees.clear(); } + + /// Clear eviction information for the given evictee Vreg. + /// E.g. when Vreg get's a new allocation, the old eviction info is no + /// longer relevant. + /// \param Evictee The evictee Vreg for whom we want to clear collected + /// eviction info. + void clearEvicteeInfo(unsigned Evictee) { Evictees.erase(Evictee); } + + /// Track new eviction. + /// The Evictor vreg has evicted the Evictee vreg from Physreg. + /// \param PhysReg The physical register Evictee was evicted from. + /// \param Evictor The evictor Vreg that evicted Evictee. + /// \param Evictee The evictee Vreg. + void addEviction(unsigned PhysReg, unsigned Evictor, unsigned Evictee) { + Evictees[Evictee].first = Evictor; + Evictees[Evictee].second = PhysReg; + } + + /// Return the Evictor Vreg which evicted Evictee Vreg from PhysReg. + /// \param Evictee The evictee vreg. + /// \return The Evictor vreg which evicted Evictee vreg from PhysReg. 0 if + /// nobody has evicted Evictee from PhysReg. + EvictorInfo getEvictor(unsigned Evictee) { + if (Evictees.count(Evictee)) { + return Evictees[Evictee]; + } + + return EvictorInfo(0, 0); + } + }; + + // Keeps track of past evictions in order to optimize region split decision. + EvictionTrack LastEvicted; + + // splitting state. + std::unique_ptr<SplitAnalysis> SA; + std::unique_ptr<SplitEditor> SE; + + /// Cached per-block interference maps + InterferenceCache IntfCache; + + /// All basic blocks where the current register has uses. + SmallVector<SpillPlacement::BlockConstraint, 8> SplitConstraints; + + /// Global live range splitting candidate info. + struct GlobalSplitCandidate { + // Register intended for assignment, or 0. + unsigned PhysReg; + + // SplitKit interval index for this candidate. + unsigned IntvIdx; + + // Interference for PhysReg. + InterferenceCache::Cursor Intf; + + // Bundles where this candidate should be live. + BitVector LiveBundles; + SmallVector<unsigned, 8> ActiveBlocks; + + void reset(InterferenceCache &Cache, unsigned Reg) { + PhysReg = Reg; + IntvIdx = 0; + Intf.setPhysReg(Cache, Reg); + LiveBundles.clear(); + ActiveBlocks.clear(); + } + + // Set B[i] = C for every live bundle where B[i] was NoCand. + unsigned getBundles(SmallVectorImpl<unsigned> &B, unsigned C) { + unsigned Count = 0; + for (unsigned i : LiveBundles.set_bits()) + if (B[i] == NoCand) { + B[i] = C; + Count++; + } + return Count; + } + }; + + /// Candidate info for each PhysReg in AllocationOrder. + /// This vector never shrinks, but grows to the size of the largest register + /// class. + SmallVector<GlobalSplitCandidate, 32> GlobalCand; + + enum : unsigned { NoCand = ~0u }; + + /// Candidate map. Each edge bundle is assigned to a GlobalCand entry, or to + /// NoCand which indicates the stack interval. + SmallVector<unsigned, 32> BundleCand; + + /// Callee-save register cost, calculated once per machine function. + BlockFrequency CSRCost; + + /// Run or not the local reassignment heuristic. This information is + /// obtained from the TargetSubtargetInfo. + bool EnableLocalReassign; + + /// Enable or not the consideration of the cost of local intervals created + /// by a split candidate when choosing the best split candidate. + bool EnableAdvancedRASplitCost; + + /// Set of broken hints that may be reconciled later because of eviction. + SmallSetVector<LiveInterval *, 8> SetOfBrokenHints; + +public: + RAGreedy(); + + /// Return the pass name. + StringRef getPassName() const override { return "Greedy Register Allocator"; } + + /// RAGreedy analysis usage. + void getAnalysisUsage(AnalysisUsage &AU) const override; + void releaseMemory() override; + Spiller &spiller() override { return *SpillerInstance; } + void enqueue(LiveInterval *LI) override; + LiveInterval *dequeue() override; + unsigned selectOrSplit(LiveInterval&, SmallVectorImpl<unsigned>&) override; + void aboutToRemoveInterval(LiveInterval &) override; + + /// Perform register allocation. + bool runOnMachineFunction(MachineFunction &mf) override; + + MachineFunctionProperties getRequiredProperties() const override { + return MachineFunctionProperties().set( + MachineFunctionProperties::Property::NoPHIs); + } + + static char ID; + +private: + unsigned selectOrSplitImpl(LiveInterval &, SmallVectorImpl<unsigned> &, + SmallVirtRegSet &, unsigned = 0); + + bool LRE_CanEraseVirtReg(unsigned) override; + void LRE_WillShrinkVirtReg(unsigned) override; + void LRE_DidCloneVirtReg(unsigned, unsigned) override; + void enqueue(PQueue &CurQueue, LiveInterval *LI); + LiveInterval *dequeue(PQueue &CurQueue); + + BlockFrequency calcSpillCost(); + bool addSplitConstraints(InterferenceCache::Cursor, BlockFrequency&); + bool addThroughConstraints(InterferenceCache::Cursor, ArrayRef<unsigned>); + bool growRegion(GlobalSplitCandidate &Cand); + bool splitCanCauseEvictionChain(unsigned Evictee, GlobalSplitCandidate &Cand, + unsigned BBNumber, + const AllocationOrder &Order); + bool splitCanCauseLocalSpill(unsigned VirtRegToSplit, + GlobalSplitCandidate &Cand, unsigned BBNumber, + const AllocationOrder &Order); + BlockFrequency calcGlobalSplitCost(GlobalSplitCandidate &, + const AllocationOrder &Order, + bool *CanCauseEvictionChain); + bool calcCompactRegion(GlobalSplitCandidate&); + void splitAroundRegion(LiveRangeEdit&, ArrayRef<unsigned>); + void calcGapWeights(unsigned, SmallVectorImpl<float>&); + unsigned canReassign(LiveInterval &VirtReg, unsigned PrevReg); + bool shouldEvict(LiveInterval &A, bool, LiveInterval &B, bool); + bool canEvictInterference(LiveInterval&, unsigned, bool, EvictionCost&, + const SmallVirtRegSet&); + bool canEvictInterferenceInRange(LiveInterval &VirtReg, unsigned PhysReg, + SlotIndex Start, SlotIndex End, + EvictionCost &MaxCost); + unsigned getCheapestEvicteeWeight(const AllocationOrder &Order, + LiveInterval &VirtReg, SlotIndex Start, + SlotIndex End, float *BestEvictWeight); + void evictInterference(LiveInterval&, unsigned, + SmallVectorImpl<unsigned>&); + bool mayRecolorAllInterferences(unsigned PhysReg, LiveInterval &VirtReg, + SmallLISet &RecoloringCandidates, + const SmallVirtRegSet &FixedRegisters); + + unsigned tryAssign(LiveInterval&, AllocationOrder&, + SmallVectorImpl<unsigned>&, + const SmallVirtRegSet&); + unsigned tryEvict(LiveInterval&, AllocationOrder&, + SmallVectorImpl<unsigned>&, unsigned, + const SmallVirtRegSet&); + unsigned tryRegionSplit(LiveInterval&, AllocationOrder&, + SmallVectorImpl<unsigned>&); + unsigned isSplitBenefitWorthCost(LiveInterval &VirtReg); + /// Calculate cost of region splitting. + unsigned calculateRegionSplitCost(LiveInterval &VirtReg, + AllocationOrder &Order, + BlockFrequency &BestCost, + unsigned &NumCands, bool IgnoreCSR, + bool *CanCauseEvictionChain = nullptr); + /// Perform region splitting. + unsigned doRegionSplit(LiveInterval &VirtReg, unsigned BestCand, + bool HasCompact, + SmallVectorImpl<unsigned> &NewVRegs); + /// Check other options before using a callee-saved register for the first + /// time. + unsigned tryAssignCSRFirstTime(LiveInterval &VirtReg, AllocationOrder &Order, + unsigned PhysReg, unsigned &CostPerUseLimit, + SmallVectorImpl<unsigned> &NewVRegs); + void initializeCSRCost(); + unsigned tryBlockSplit(LiveInterval&, AllocationOrder&, + SmallVectorImpl<unsigned>&); + unsigned tryInstructionSplit(LiveInterval&, AllocationOrder&, + SmallVectorImpl<unsigned>&); + unsigned tryLocalSplit(LiveInterval&, AllocationOrder&, + SmallVectorImpl<unsigned>&); + unsigned trySplit(LiveInterval&, AllocationOrder&, + SmallVectorImpl<unsigned>&, + const SmallVirtRegSet&); + unsigned tryLastChanceRecoloring(LiveInterval &, AllocationOrder &, + SmallVectorImpl<unsigned> &, + SmallVirtRegSet &, unsigned); + bool tryRecoloringCandidates(PQueue &, SmallVectorImpl<unsigned> &, + SmallVirtRegSet &, unsigned); + void tryHintRecoloring(LiveInterval &); + void tryHintsRecoloring(); + + /// Model the information carried by one end of a copy. + struct HintInfo { + /// The frequency of the copy. + BlockFrequency Freq; + /// The virtual register or physical register. + unsigned Reg; + /// Its currently assigned register. + /// In case of a physical register Reg == PhysReg. + unsigned PhysReg; + + HintInfo(BlockFrequency Freq, unsigned Reg, unsigned PhysReg) + : Freq(Freq), Reg(Reg), PhysReg(PhysReg) {} + }; + using HintsInfo = SmallVector<HintInfo, 4>; + + BlockFrequency getBrokenHintFreq(const HintsInfo &, unsigned); + void collectHintInfo(unsigned, HintsInfo &); + + bool isUnusedCalleeSavedReg(unsigned PhysReg) const; + + /// Compute and report the number of spills and reloads for a loop. + void reportNumberOfSplillsReloads(MachineLoop *L, unsigned &Reloads, + unsigned &FoldedReloads, unsigned &Spills, + unsigned &FoldedSpills); + + /// Report the number of spills and reloads for each loop. + void reportNumberOfSplillsReloads() { + for (MachineLoop *L : *Loops) { + unsigned Reloads, FoldedReloads, Spills, FoldedSpills; + reportNumberOfSplillsReloads(L, Reloads, FoldedReloads, Spills, + FoldedSpills); + } + } +}; + +} // end anonymous namespace + +char RAGreedy::ID = 0; +char &llvm::RAGreedyID = RAGreedy::ID; + +INITIALIZE_PASS_BEGIN(RAGreedy, "greedy", + "Greedy Register Allocator", false, false) +INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables) +INITIALIZE_PASS_DEPENDENCY(SlotIndexes) +INITIALIZE_PASS_DEPENDENCY(LiveIntervals) +INITIALIZE_PASS_DEPENDENCY(RegisterCoalescer) +INITIALIZE_PASS_DEPENDENCY(MachineScheduler) +INITIALIZE_PASS_DEPENDENCY(LiveStacks) +INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) +INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) +INITIALIZE_PASS_DEPENDENCY(VirtRegMap) +INITIALIZE_PASS_DEPENDENCY(LiveRegMatrix) +INITIALIZE_PASS_DEPENDENCY(EdgeBundles) +INITIALIZE_PASS_DEPENDENCY(SpillPlacement) +INITIALIZE_PASS_DEPENDENCY(MachineOptimizationRemarkEmitterPass) +INITIALIZE_PASS_END(RAGreedy, "greedy", + "Greedy Register Allocator", false, false) + +#ifndef NDEBUG +const char *const RAGreedy::StageName[] = { + "RS_New", + "RS_Assign", + "RS_Split", + "RS_Split2", + "RS_Spill", + "RS_Memory", + "RS_Done" +}; +#endif + +// Hysteresis to use when comparing floats. +// This helps stabilize decisions based on float comparisons. +const float Hysteresis = (2007 / 2048.0f); // 0.97998046875 + +FunctionPass* llvm::createGreedyRegisterAllocator() { + return new RAGreedy(); +} + +RAGreedy::RAGreedy(): MachineFunctionPass(ID) { +} + +void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesCFG(); + AU.addRequired<MachineBlockFrequencyInfo>(); + AU.addPreserved<MachineBlockFrequencyInfo>(); + AU.addRequired<AAResultsWrapperPass>(); + AU.addPreserved<AAResultsWrapperPass>(); + AU.addRequired<LiveIntervals>(); + AU.addPreserved<LiveIntervals>(); + AU.addRequired<SlotIndexes>(); + AU.addPreserved<SlotIndexes>(); + AU.addRequired<LiveDebugVariables>(); + AU.addPreserved<LiveDebugVariables>(); + AU.addRequired<LiveStacks>(); + AU.addPreserved<LiveStacks>(); + AU.addRequired<MachineDominatorTree>(); + AU.addPreserved<MachineDominatorTree>(); + AU.addRequired<MachineLoopInfo>(); + AU.addPreserved<MachineLoopInfo>(); + AU.addRequired<VirtRegMap>(); + AU.addPreserved<VirtRegMap>(); + AU.addRequired<LiveRegMatrix>(); + AU.addPreserved<LiveRegMatrix>(); + AU.addRequired<EdgeBundles>(); + AU.addRequired<SpillPlacement>(); + AU.addRequired<MachineOptimizationRemarkEmitterPass>(); + MachineFunctionPass::getAnalysisUsage(AU); +} + +//===----------------------------------------------------------------------===// +// LiveRangeEdit delegate methods +//===----------------------------------------------------------------------===// + +bool RAGreedy::LRE_CanEraseVirtReg(unsigned VirtReg) { + LiveInterval &LI = LIS->getInterval(VirtReg); + if (VRM->hasPhys(VirtReg)) { + Matrix->unassign(LI); + aboutToRemoveInterval(LI); + return true; + } + // Unassigned virtreg is probably in the priority queue. + // RegAllocBase will erase it after dequeueing. + // Nonetheless, clear the live-range so that the debug + // dump will show the right state for that VirtReg. + LI.clear(); + return false; +} + +void RAGreedy::LRE_WillShrinkVirtReg(unsigned VirtReg) { + if (!VRM->hasPhys(VirtReg)) + return; + + // Register is assigned, put it back on the queue for reassignment. + LiveInterval &LI = LIS->getInterval(VirtReg); + Matrix->unassign(LI); + enqueue(&LI); +} + +void RAGreedy::LRE_DidCloneVirtReg(unsigned New, unsigned Old) { + // Cloning a register we haven't even heard about yet? Just ignore it. + if (!ExtraRegInfo.inBounds(Old)) + return; + + // LRE may clone a virtual register because dead code elimination causes it to + // be split into connected components. The new components are much smaller + // than the original, so they should get a new chance at being assigned. + // same stage as the parent. + ExtraRegInfo[Old].Stage = RS_Assign; + ExtraRegInfo.grow(New); + ExtraRegInfo[New] = ExtraRegInfo[Old]; +} + +void RAGreedy::releaseMemory() { + SpillerInstance.reset(); + ExtraRegInfo.clear(); + GlobalCand.clear(); +} + +void RAGreedy::enqueue(LiveInterval *LI) { enqueue(Queue, LI); } + +void RAGreedy::enqueue(PQueue &CurQueue, LiveInterval *LI) { + // Prioritize live ranges by size, assigning larger ranges first. + // The queue holds (size, reg) pairs. + const unsigned Size = LI->getSize(); + const unsigned Reg = LI->reg; + assert(Register::isVirtualRegister(Reg) && + "Can only enqueue virtual registers"); + unsigned Prio; + + ExtraRegInfo.grow(Reg); + if (ExtraRegInfo[Reg].Stage == RS_New) + ExtraRegInfo[Reg].Stage = RS_Assign; + + if (ExtraRegInfo[Reg].Stage == RS_Split) { + // Unsplit ranges that couldn't be allocated immediately are deferred until + // everything else has been allocated. + Prio = Size; + } else if (ExtraRegInfo[Reg].Stage == RS_Memory) { + // Memory operand should be considered last. + // Change the priority such that Memory operand are assigned in + // the reverse order that they came in. + // TODO: Make this a member variable and probably do something about hints. + static unsigned MemOp = 0; + Prio = MemOp++; + } else { + // Giant live ranges fall back to the global assignment heuristic, which + // prevents excessive spilling in pathological cases. + bool ReverseLocal = TRI->reverseLocalAssignment(); + const TargetRegisterClass &RC = *MRI->getRegClass(Reg); + bool ForceGlobal = !ReverseLocal && + (Size / SlotIndex::InstrDist) > (2 * RC.getNumRegs()); + + if (ExtraRegInfo[Reg].Stage == RS_Assign && !ForceGlobal && !LI->empty() && + LIS->intervalIsInOneMBB(*LI)) { + // Allocate original local ranges in linear instruction order. Since they + // are singly defined, this produces optimal coloring in the absence of + // global interference and other constraints. + if (!ReverseLocal) + Prio = LI->beginIndex().getInstrDistance(Indexes->getLastIndex()); + else { + // Allocating bottom up may allow many short LRGs to be assigned first + // to one of the cheap registers. This could be much faster for very + // large blocks on targets with many physical registers. + Prio = Indexes->getZeroIndex().getInstrDistance(LI->endIndex()); + } + Prio |= RC.AllocationPriority << 24; + } else { + // Allocate global and split ranges in long->short order. Long ranges that + // don't fit should be spilled (or split) ASAP so they don't create + // interference. Mark a bit to prioritize global above local ranges. + Prio = (1u << 29) + Size; + } + // Mark a higher bit to prioritize global and local above RS_Split. + Prio |= (1u << 31); + + // Boost ranges that have a physical register hint. + if (VRM->hasKnownPreference(Reg)) + Prio |= (1u << 30); + } + // The virtual register number is a tie breaker for same-sized ranges. + // Give lower vreg numbers higher priority to assign them first. + CurQueue.push(std::make_pair(Prio, ~Reg)); +} + +LiveInterval *RAGreedy::dequeue() { return dequeue(Queue); } + +LiveInterval *RAGreedy::dequeue(PQueue &CurQueue) { + if (CurQueue.empty()) + return nullptr; + LiveInterval *LI = &LIS->getInterval(~CurQueue.top().second); + CurQueue.pop(); + return LI; +} + +//===----------------------------------------------------------------------===// +// Direct Assignment +//===----------------------------------------------------------------------===// + +/// tryAssign - Try to assign VirtReg to an available register. +unsigned RAGreedy::tryAssign(LiveInterval &VirtReg, + AllocationOrder &Order, + SmallVectorImpl<unsigned> &NewVRegs, + const SmallVirtRegSet &FixedRegisters) { + Order.rewind(); + unsigned PhysReg; + while ((PhysReg = Order.next())) + if (!Matrix->checkInterference(VirtReg, PhysReg)) + break; + if (!PhysReg || Order.isHint()) + return PhysReg; + + // PhysReg is available, but there may be a better choice. + + // If we missed a simple hint, try to cheaply evict interference from the + // preferred register. + if (unsigned Hint = MRI->getSimpleHint(VirtReg.reg)) + if (Order.isHint(Hint)) { + LLVM_DEBUG(dbgs() << "missed hint " << printReg(Hint, TRI) << '\n'); + EvictionCost MaxCost; + MaxCost.setBrokenHints(1); + if (canEvictInterference(VirtReg, Hint, true, MaxCost, FixedRegisters)) { + evictInterference(VirtReg, Hint, NewVRegs); + return Hint; + } + // Record the missed hint, we may be able to recover + // at the end if the surrounding allocation changed. + SetOfBrokenHints.insert(&VirtReg); + } + + // Try to evict interference from a cheaper alternative. + unsigned Cost = TRI->getCostPerUse(PhysReg); + + // Most registers have 0 additional cost. + if (!Cost) + return PhysReg; + + LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << " is available at cost " + << Cost << '\n'); + unsigned CheapReg = tryEvict(VirtReg, Order, NewVRegs, Cost, FixedRegisters); + return CheapReg ? CheapReg : PhysReg; +} + +//===----------------------------------------------------------------------===// +// Interference eviction +//===----------------------------------------------------------------------===// + +unsigned RAGreedy::canReassign(LiveInterval &VirtReg, unsigned PrevReg) { + AllocationOrder Order(VirtReg.reg, *VRM, RegClassInfo, Matrix); + unsigned PhysReg; + while ((PhysReg = Order.next())) { + if (PhysReg == PrevReg) + continue; + + MCRegUnitIterator Units(PhysReg, TRI); + for (; Units.isValid(); ++Units) { + // Instantiate a "subquery", not to be confused with the Queries array. + LiveIntervalUnion::Query subQ(VirtReg, Matrix->getLiveUnions()[*Units]); + if (subQ.checkInterference()) + break; + } + // If no units have interference, break out with the current PhysReg. + if (!Units.isValid()) + break; + } + if (PhysReg) + LLVM_DEBUG(dbgs() << "can reassign: " << VirtReg << " from " + << printReg(PrevReg, TRI) << " to " + << printReg(PhysReg, TRI) << '\n'); + return PhysReg; +} + +/// shouldEvict - determine if A should evict the assigned live range B. The +/// eviction policy defined by this function together with the allocation order +/// defined by enqueue() decides which registers ultimately end up being split +/// and spilled. +/// +/// Cascade numbers are used to prevent infinite loops if this function is a +/// cyclic relation. +/// +/// @param A The live range to be assigned. +/// @param IsHint True when A is about to be assigned to its preferred +/// register. +/// @param B The live range to be evicted. +/// @param BreaksHint True when B is already assigned to its preferred register. +bool RAGreedy::shouldEvict(LiveInterval &A, bool IsHint, + LiveInterval &B, bool BreaksHint) { + bool CanSplit = getStage(B) < RS_Spill; + + // Be fairly aggressive about following hints as long as the evictee can be + // split. + if (CanSplit && IsHint && !BreaksHint) + return true; + + if (A.weight > B.weight) { + LLVM_DEBUG(dbgs() << "should evict: " << B << " w= " << B.weight << '\n'); + return true; + } + return false; +} + +/// canEvictInterference - Return true if all interferences between VirtReg and +/// PhysReg can be evicted. +/// +/// @param VirtReg Live range that is about to be assigned. +/// @param PhysReg Desired register for assignment. +/// @param IsHint True when PhysReg is VirtReg's preferred register. +/// @param MaxCost Only look for cheaper candidates and update with new cost +/// when returning true. +/// @returns True when interference can be evicted cheaper than MaxCost. +bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg, + bool IsHint, EvictionCost &MaxCost, + const SmallVirtRegSet &FixedRegisters) { + // It is only possible to evict virtual register interference. + if (Matrix->checkInterference(VirtReg, PhysReg) > LiveRegMatrix::IK_VirtReg) + return false; + + bool IsLocal = LIS->intervalIsInOneMBB(VirtReg); + + // Find VirtReg's cascade number. This will be unassigned if VirtReg was never + // involved in an eviction before. If a cascade number was assigned, deny + // evicting anything with the same or a newer cascade number. This prevents + // infinite eviction loops. + // + // This works out so a register without a cascade number is allowed to evict + // anything, and it can be evicted by anything. + unsigned Cascade = ExtraRegInfo[VirtReg.reg].Cascade; + if (!Cascade) + Cascade = NextCascade; + + EvictionCost Cost; + for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) { + LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units); + // If there is 10 or more interferences, chances are one is heavier. + if (Q.collectInterferingVRegs(10) >= 10) + return false; + + // Check if any interfering live range is heavier than MaxWeight. + for (unsigned i = Q.interferingVRegs().size(); i; --i) { + LiveInterval *Intf = Q.interferingVRegs()[i - 1]; + assert(Register::isVirtualRegister(Intf->reg) && + "Only expecting virtual register interference from query"); + + // Do not allow eviction of a virtual register if we are in the middle + // of last-chance recoloring and this virtual register is one that we + // have scavenged a physical register for. + if (FixedRegisters.count(Intf->reg)) + return false; + + // Never evict spill products. They cannot split or spill. + if (getStage(*Intf) == RS_Done) + return false; + // Once a live range becomes small enough, it is urgent that we find a + // register for it. This is indicated by an infinite spill weight. These + // urgent live ranges get to evict almost anything. + // + // Also allow urgent evictions of unspillable ranges from a strictly + // larger allocation order. + bool Urgent = !VirtReg.isSpillable() && + (Intf->isSpillable() || + RegClassInfo.getNumAllocatableRegs(MRI->getRegClass(VirtReg.reg)) < + RegClassInfo.getNumAllocatableRegs(MRI->getRegClass(Intf->reg))); + // Only evict older cascades or live ranges without a cascade. + unsigned IntfCascade = ExtraRegInfo[Intf->reg].Cascade; + if (Cascade <= IntfCascade) { + if (!Urgent) + return false; + // We permit breaking cascades for urgent evictions. It should be the + // last resort, though, so make it really expensive. + Cost.BrokenHints += 10; + } + // Would this break a satisfied hint? + bool BreaksHint = VRM->hasPreferredPhys(Intf->reg); + // Update eviction cost. + Cost.BrokenHints += BreaksHint; + Cost.MaxWeight = std::max(Cost.MaxWeight, Intf->weight); + // Abort if this would be too expensive. + if (!(Cost < MaxCost)) + return false; + if (Urgent) + continue; + // Apply the eviction policy for non-urgent evictions. + if (!shouldEvict(VirtReg, IsHint, *Intf, BreaksHint)) + return false; + // If !MaxCost.isMax(), then we're just looking for a cheap register. + // Evicting another local live range in this case could lead to suboptimal + // coloring. + if (!MaxCost.isMax() && IsLocal && LIS->intervalIsInOneMBB(*Intf) && + (!EnableLocalReassign || !canReassign(*Intf, PhysReg))) { + return false; + } + } + } + MaxCost = Cost; + return true; +} + +/// Return true if all interferences between VirtReg and PhysReg between +/// Start and End can be evicted. +/// +/// \param VirtReg Live range that is about to be assigned. +/// \param PhysReg Desired register for assignment. +/// \param Start Start of range to look for interferences. +/// \param End End of range to look for interferences. +/// \param MaxCost Only look for cheaper candidates and update with new cost +/// when returning true. +/// \return True when interference can be evicted cheaper than MaxCost. +bool RAGreedy::canEvictInterferenceInRange(LiveInterval &VirtReg, + unsigned PhysReg, SlotIndex Start, + SlotIndex End, + EvictionCost &MaxCost) { + EvictionCost Cost; + + for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) { + LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units); + + // Check if any interfering live range is heavier than MaxWeight. + for (unsigned i = Q.interferingVRegs().size(); i; --i) { + LiveInterval *Intf = Q.interferingVRegs()[i - 1]; + + // Check if interference overlast the segment in interest. + if (!Intf->overlaps(Start, End)) + continue; + + // Cannot evict non virtual reg interference. + if (!Register::isVirtualRegister(Intf->reg)) + return false; + // Never evict spill products. They cannot split or spill. + if (getStage(*Intf) == RS_Done) + return false; + + // Would this break a satisfied hint? + bool BreaksHint = VRM->hasPreferredPhys(Intf->reg); + // Update eviction cost. + Cost.BrokenHints += BreaksHint; + Cost.MaxWeight = std::max(Cost.MaxWeight, Intf->weight); + // Abort if this would be too expensive. + if (!(Cost < MaxCost)) + return false; + } + } + + if (Cost.MaxWeight == 0) + return false; + + MaxCost = Cost; + return true; +} + +/// Return the physical register that will be best +/// candidate for eviction by a local split interval that will be created +/// between Start and End. +/// +/// \param Order The allocation order +/// \param VirtReg Live range that is about to be assigned. +/// \param Start Start of range to look for interferences +/// \param End End of range to look for interferences +/// \param BestEvictweight The eviction cost of that eviction +/// \return The PhysReg which is the best candidate for eviction and the +/// eviction cost in BestEvictweight +unsigned RAGreedy::getCheapestEvicteeWeight(const AllocationOrder &Order, + LiveInterval &VirtReg, + SlotIndex Start, SlotIndex End, + float *BestEvictweight) { + EvictionCost BestEvictCost; + BestEvictCost.setMax(); + BestEvictCost.MaxWeight = VirtReg.weight; + unsigned BestEvicteePhys = 0; + + // Go over all physical registers and find the best candidate for eviction + for (auto PhysReg : Order.getOrder()) { + + if (!canEvictInterferenceInRange(VirtReg, PhysReg, Start, End, + BestEvictCost)) + continue; + + // Best so far. + BestEvicteePhys = PhysReg; + } + *BestEvictweight = BestEvictCost.MaxWeight; + return BestEvicteePhys; +} + +/// evictInterference - Evict any interferring registers that prevent VirtReg +/// from being assigned to Physreg. This assumes that canEvictInterference +/// returned true. +void RAGreedy::evictInterference(LiveInterval &VirtReg, unsigned PhysReg, + SmallVectorImpl<unsigned> &NewVRegs) { + // Make sure that VirtReg has a cascade number, and assign that cascade + // number to every evicted register. These live ranges than then only be + // evicted by a newer cascade, preventing infinite loops. + unsigned Cascade = ExtraRegInfo[VirtReg.reg].Cascade; + if (!Cascade) + Cascade = ExtraRegInfo[VirtReg.reg].Cascade = NextCascade++; + + LLVM_DEBUG(dbgs() << "evicting " << printReg(PhysReg, TRI) + << " interference: Cascade " << Cascade << '\n'); + + // Collect all interfering virtregs first. + SmallVector<LiveInterval*, 8> Intfs; + for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) { + LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units); + // We usually have the interfering VRegs cached so collectInterferingVRegs() + // should be fast, we may need to recalculate if when different physregs + // overlap the same register unit so we had different SubRanges queried + // against it. + Q.collectInterferingVRegs(); + ArrayRef<LiveInterval*> IVR = Q.interferingVRegs(); + Intfs.append(IVR.begin(), IVR.end()); + } + + // Evict them second. This will invalidate the queries. + for (unsigned i = 0, e = Intfs.size(); i != e; ++i) { + LiveInterval *Intf = Intfs[i]; + // The same VirtReg may be present in multiple RegUnits. Skip duplicates. + if (!VRM->hasPhys(Intf->reg)) + continue; + + LastEvicted.addEviction(PhysReg, VirtReg.reg, Intf->reg); + + Matrix->unassign(*Intf); + assert((ExtraRegInfo[Intf->reg].Cascade < Cascade || + VirtReg.isSpillable() < Intf->isSpillable()) && + "Cannot decrease cascade number, illegal eviction"); + ExtraRegInfo[Intf->reg].Cascade = Cascade; + ++NumEvicted; + NewVRegs.push_back(Intf->reg); + } +} + +/// Returns true if the given \p PhysReg is a callee saved register and has not +/// been used for allocation yet. +bool RAGreedy::isUnusedCalleeSavedReg(unsigned PhysReg) const { + unsigned CSR = RegClassInfo.getLastCalleeSavedAlias(PhysReg); + if (CSR == 0) + return false; + + return !Matrix->isPhysRegUsed(PhysReg); +} + +/// tryEvict - Try to evict all interferences for a physreg. +/// @param VirtReg Currently unassigned virtual register. +/// @param Order Physregs to try. +/// @return Physreg to assign VirtReg, or 0. +unsigned RAGreedy::tryEvict(LiveInterval &VirtReg, + AllocationOrder &Order, + SmallVectorImpl<unsigned> &NewVRegs, + unsigned CostPerUseLimit, + const SmallVirtRegSet &FixedRegisters) { + NamedRegionTimer T("evict", "Evict", TimerGroupName, TimerGroupDescription, + TimePassesIsEnabled); + + // Keep track of the cheapest interference seen so far. + EvictionCost BestCost; + BestCost.setMax(); + unsigned BestPhys = 0; + unsigned OrderLimit = Order.getOrder().size(); + + // When we are just looking for a reduced cost per use, don't break any + // hints, and only evict smaller spill weights. + if (CostPerUseLimit < ~0u) { + BestCost.BrokenHints = 0; + BestCost.MaxWeight = VirtReg.weight; + + // Check of any registers in RC are below CostPerUseLimit. + const TargetRegisterClass *RC = MRI->getRegClass(VirtReg.reg); + unsigned MinCost = RegClassInfo.getMinCost(RC); + if (MinCost >= CostPerUseLimit) { + LLVM_DEBUG(dbgs() << TRI->getRegClassName(RC) << " minimum cost = " + << MinCost << ", no cheaper registers to be found.\n"); + return 0; + } + + // It is normal for register classes to have a long tail of registers with + // the same cost. We don't need to look at them if they're too expensive. + if (TRI->getCostPerUse(Order.getOrder().back()) >= CostPerUseLimit) { + OrderLimit = RegClassInfo.getLastCostChange(RC); + LLVM_DEBUG(dbgs() << "Only trying the first " << OrderLimit + << " regs.\n"); + } + } + + Order.rewind(); + while (unsigned PhysReg = Order.next(OrderLimit)) { + if (TRI->getCostPerUse(PhysReg) >= CostPerUseLimit) + continue; + // The first use of a callee-saved register in a function has cost 1. + // Don't start using a CSR when the CostPerUseLimit is low. + if (CostPerUseLimit == 1 && isUnusedCalleeSavedReg(PhysReg)) { + LLVM_DEBUG( + dbgs() << printReg(PhysReg, TRI) << " would clobber CSR " + << printReg(RegClassInfo.getLastCalleeSavedAlias(PhysReg), TRI) + << '\n'); + continue; + } + + if (!canEvictInterference(VirtReg, PhysReg, false, BestCost, + FixedRegisters)) + continue; + + // Best so far. + BestPhys = PhysReg; + + // Stop if the hint can be used. + if (Order.isHint()) + break; + } + + if (!BestPhys) + return 0; + + evictInterference(VirtReg, BestPhys, NewVRegs); + return BestPhys; +} + +//===----------------------------------------------------------------------===// +// Region Splitting +//===----------------------------------------------------------------------===// + +/// addSplitConstraints - Fill out the SplitConstraints vector based on the +/// interference pattern in Physreg and its aliases. Add the constraints to +/// SpillPlacement and return the static cost of this split in Cost, assuming +/// that all preferences in SplitConstraints are met. +/// Return false if there are no bundles with positive bias. +bool RAGreedy::addSplitConstraints(InterferenceCache::Cursor Intf, + BlockFrequency &Cost) { + ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks(); + + // Reset interference dependent info. + SplitConstraints.resize(UseBlocks.size()); + BlockFrequency StaticCost = 0; + for (unsigned i = 0; i != UseBlocks.size(); ++i) { + const SplitAnalysis::BlockInfo &BI = UseBlocks[i]; + SpillPlacement::BlockConstraint &BC = SplitConstraints[i]; + + BC.Number = BI.MBB->getNumber(); + Intf.moveToBlock(BC.Number); + BC.Entry = BI.LiveIn ? SpillPlacement::PrefReg : SpillPlacement::DontCare; + BC.Exit = (BI.LiveOut && + !LIS->getInstructionFromIndex(BI.LastInstr)->isImplicitDef()) + ? SpillPlacement::PrefReg + : SpillPlacement::DontCare; + BC.ChangesValue = BI.FirstDef.isValid(); + + if (!Intf.hasInterference()) + continue; + + // Number of spill code instructions to insert. + unsigned Ins = 0; + + // Interference for the live-in value. + if (BI.LiveIn) { + if (Intf.first() <= Indexes->getMBBStartIdx(BC.Number)) { + BC.Entry = SpillPlacement::MustSpill; + ++Ins; + } else if (Intf.first() < BI.FirstInstr) { + BC.Entry = SpillPlacement::PrefSpill; + ++Ins; + } else if (Intf.first() < BI.LastInstr) { + ++Ins; + } + + // Abort if the spill cannot be inserted at the MBB' start + if (((BC.Entry == SpillPlacement::MustSpill) || + (BC.Entry == SpillPlacement::PrefSpill)) && + SlotIndex::isEarlierInstr(BI.FirstInstr, + SA->getFirstSplitPoint(BC.Number))) + return false; + } + + // Interference for the live-out value. + if (BI.LiveOut) { + if (Intf.last() >= SA->getLastSplitPoint(BC.Number)) { + BC.Exit = SpillPlacement::MustSpill; + ++Ins; + } else if (Intf.last() > BI.LastInstr) { + BC.Exit = SpillPlacement::PrefSpill; + ++Ins; + } else if (Intf.last() > BI.FirstInstr) { + ++Ins; + } + } + + // Accumulate the total frequency of inserted spill code. + while (Ins--) + StaticCost += SpillPlacer->getBlockFrequency(BC.Number); + } + Cost = StaticCost; + + // Add constraints for use-blocks. Note that these are the only constraints + // that may add a positive bias, it is downhill from here. + SpillPlacer->addConstraints(SplitConstraints); + return SpillPlacer->scanActiveBundles(); +} + +/// addThroughConstraints - Add constraints and links to SpillPlacer from the +/// live-through blocks in Blocks. +bool RAGreedy::addThroughConstraints(InterferenceCache::Cursor Intf, + ArrayRef<unsigned> Blocks) { + const unsigned GroupSize = 8; + SpillPlacement::BlockConstraint BCS[GroupSize]; + unsigned TBS[GroupSize]; + unsigned B = 0, T = 0; + + for (unsigned i = 0; i != Blocks.size(); ++i) { + unsigned Number = Blocks[i]; + Intf.moveToBlock(Number); + + if (!Intf.hasInterference()) { + assert(T < GroupSize && "Array overflow"); + TBS[T] = Number; + if (++T == GroupSize) { + SpillPlacer->addLinks(makeArrayRef(TBS, T)); + T = 0; + } + continue; + } + + assert(B < GroupSize && "Array overflow"); + BCS[B].Number = Number; + + // Abort if the spill cannot be inserted at the MBB' start + MachineBasicBlock *MBB = MF->getBlockNumbered(Number); + if (!MBB->empty() && + SlotIndex::isEarlierInstr(LIS->getInstructionIndex(MBB->instr_front()), + SA->getFirstSplitPoint(Number))) + return false; + // Interference for the live-in value. + if (Intf.first() <= Indexes->getMBBStartIdx(Number)) + BCS[B].Entry = SpillPlacement::MustSpill; + else + BCS[B].Entry = SpillPlacement::PrefSpill; + + // Interference for the live-out value. + if (Intf.last() >= SA->getLastSplitPoint(Number)) + BCS[B].Exit = SpillPlacement::MustSpill; + else + BCS[B].Exit = SpillPlacement::PrefSpill; + + if (++B == GroupSize) { + SpillPlacer->addConstraints(makeArrayRef(BCS, B)); + B = 0; + } + } + + SpillPlacer->addConstraints(makeArrayRef(BCS, B)); + SpillPlacer->addLinks(makeArrayRef(TBS, T)); + return true; +} + +bool RAGreedy::growRegion(GlobalSplitCandidate &Cand) { + // Keep track of through blocks that have not been added to SpillPlacer. + BitVector Todo = SA->getThroughBlocks(); + SmallVectorImpl<unsigned> &ActiveBlocks = Cand.ActiveBlocks; + unsigned AddedTo = 0; +#ifndef NDEBUG + unsigned Visited = 0; +#endif + + while (true) { + ArrayRef<unsigned> NewBundles = SpillPlacer->getRecentPositive(); + // Find new through blocks in the periphery of PrefRegBundles. + for (int i = 0, e = NewBundles.size(); i != e; ++i) { + unsigned Bundle = NewBundles[i]; + // Look at all blocks connected to Bundle in the full graph. + ArrayRef<unsigned> Blocks = Bundles->getBlocks(Bundle); + for (ArrayRef<unsigned>::iterator I = Blocks.begin(), E = Blocks.end(); + I != E; ++I) { + unsigned Block = *I; + if (!Todo.test(Block)) + continue; + Todo.reset(Block); + // This is a new through block. Add it to SpillPlacer later. + ActiveBlocks.push_back(Block); +#ifndef NDEBUG + ++Visited; +#endif + } + } + // Any new blocks to add? + if (ActiveBlocks.size() == AddedTo) + break; + + // Compute through constraints from the interference, or assume that all + // through blocks prefer spilling when forming compact regions. + auto NewBlocks = makeArrayRef(ActiveBlocks).slice(AddedTo); + if (Cand.PhysReg) { + if (!addThroughConstraints(Cand.Intf, NewBlocks)) + return false; + } else + // Provide a strong negative bias on through blocks to prevent unwanted + // liveness on loop backedges. + SpillPlacer->addPrefSpill(NewBlocks, /* Strong= */ true); + AddedTo = ActiveBlocks.size(); + + // Perhaps iterating can enable more bundles? + SpillPlacer->iterate(); + } + LLVM_DEBUG(dbgs() << ", v=" << Visited); + return true; +} + +/// calcCompactRegion - Compute the set of edge bundles that should be live +/// when splitting the current live range into compact regions. Compact +/// regions can be computed without looking at interference. They are the +/// regions formed by removing all the live-through blocks from the live range. +/// +/// Returns false if the current live range is already compact, or if the +/// compact regions would form single block regions anyway. +bool RAGreedy::calcCompactRegion(GlobalSplitCandidate &Cand) { + // Without any through blocks, the live range is already compact. + if (!SA->getNumThroughBlocks()) + return false; + + // Compact regions don't correspond to any physreg. + Cand.reset(IntfCache, 0); + + LLVM_DEBUG(dbgs() << "Compact region bundles"); + + // Use the spill placer to determine the live bundles. GrowRegion pretends + // that all the through blocks have interference when PhysReg is unset. + SpillPlacer->prepare(Cand.LiveBundles); + + // The static split cost will be zero since Cand.Intf reports no interference. + BlockFrequency Cost; + if (!addSplitConstraints(Cand.Intf, Cost)) { + LLVM_DEBUG(dbgs() << ", none.\n"); + return false; + } + + if (!growRegion(Cand)) { + LLVM_DEBUG(dbgs() << ", cannot spill all interferences.\n"); + return false; + } + + SpillPlacer->finish(); + + if (!Cand.LiveBundles.any()) { + LLVM_DEBUG(dbgs() << ", none.\n"); + return false; + } + + LLVM_DEBUG({ + for (int i : Cand.LiveBundles.set_bits()) + dbgs() << " EB#" << i; + dbgs() << ".\n"; + }); + return true; +} + +/// calcSpillCost - Compute how expensive it would be to split the live range in +/// SA around all use blocks instead of forming bundle regions. +BlockFrequency RAGreedy::calcSpillCost() { + BlockFrequency Cost = 0; + ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks(); + for (unsigned i = 0; i != UseBlocks.size(); ++i) { + const SplitAnalysis::BlockInfo &BI = UseBlocks[i]; + unsigned Number = BI.MBB->getNumber(); + // We normally only need one spill instruction - a load or a store. + Cost += SpillPlacer->getBlockFrequency(Number); + + // Unless the value is redefined in the block. + if (BI.LiveIn && BI.LiveOut && BI.FirstDef) + Cost += SpillPlacer->getBlockFrequency(Number); + } + return Cost; +} + +/// Check if splitting Evictee will create a local split interval in +/// basic block number BBNumber that may cause a bad eviction chain. This is +/// intended to prevent bad eviction sequences like: +/// movl %ebp, 8(%esp) # 4-byte Spill +/// movl %ecx, %ebp +/// movl %ebx, %ecx +/// movl %edi, %ebx +/// movl %edx, %edi +/// cltd +/// idivl %esi +/// movl %edi, %edx +/// movl %ebx, %edi +/// movl %ecx, %ebx +/// movl %ebp, %ecx +/// movl 16(%esp), %ebp # 4 - byte Reload +/// +/// Such sequences are created in 2 scenarios: +/// +/// Scenario #1: +/// %0 is evicted from physreg0 by %1. +/// Evictee %0 is intended for region splitting with split candidate +/// physreg0 (the reg %0 was evicted from). +/// Region splitting creates a local interval because of interference with the +/// evictor %1 (normally region splitting creates 2 interval, the "by reg" +/// and "by stack" intervals and local interval created when interference +/// occurs). +/// One of the split intervals ends up evicting %2 from physreg1. +/// Evictee %2 is intended for region splitting with split candidate +/// physreg1. +/// One of the split intervals ends up evicting %3 from physreg2, etc. +/// +/// Scenario #2 +/// %0 is evicted from physreg0 by %1. +/// %2 is evicted from physreg2 by %3 etc. +/// Evictee %0 is intended for region splitting with split candidate +/// physreg1. +/// Region splitting creates a local interval because of interference with the +/// evictor %1. +/// One of the split intervals ends up evicting back original evictor %1 +/// from physreg0 (the reg %0 was evicted from). +/// Another evictee %2 is intended for region splitting with split candidate +/// physreg1. +/// One of the split intervals ends up evicting %3 from physreg2, etc. +/// +/// \param Evictee The register considered to be split. +/// \param Cand The split candidate that determines the physical register +/// we are splitting for and the interferences. +/// \param BBNumber The number of a BB for which the region split process will +/// create a local split interval. +/// \param Order The physical registers that may get evicted by a split +/// artifact of Evictee. +/// \return True if splitting Evictee may cause a bad eviction chain, false +/// otherwise. +bool RAGreedy::splitCanCauseEvictionChain(unsigned Evictee, + GlobalSplitCandidate &Cand, + unsigned BBNumber, + const AllocationOrder &Order) { + EvictionTrack::EvictorInfo VregEvictorInfo = LastEvicted.getEvictor(Evictee); + unsigned Evictor = VregEvictorInfo.first; + unsigned PhysReg = VregEvictorInfo.second; + + // No actual evictor. + if (!Evictor || !PhysReg) + return false; + + float MaxWeight = 0; + unsigned FutureEvictedPhysReg = + getCheapestEvicteeWeight(Order, LIS->getInterval(Evictee), + Cand.Intf.first(), Cand.Intf.last(), &MaxWeight); + + // The bad eviction chain occurs when either the split candidate is the + // evicting reg or one of the split artifact will evict the evicting reg. + if ((PhysReg != Cand.PhysReg) && (PhysReg != FutureEvictedPhysReg)) + return false; + + Cand.Intf.moveToBlock(BBNumber); + + // Check to see if the Evictor contains interference (with Evictee) in the + // given BB. If so, this interference caused the eviction of Evictee from + // PhysReg. This suggest that we will create a local interval during the + // region split to avoid this interference This local interval may cause a bad + // eviction chain. + if (!LIS->hasInterval(Evictor)) + return false; + LiveInterval &EvictorLI = LIS->getInterval(Evictor); + if (EvictorLI.FindSegmentContaining(Cand.Intf.first()) == EvictorLI.end()) + return false; + + // Now, check to see if the local interval we will create is going to be + // expensive enough to evict somebody If so, this may cause a bad eviction + // chain. + VirtRegAuxInfo VRAI(*MF, *LIS, VRM, getAnalysis<MachineLoopInfo>(), *MBFI); + float splitArtifactWeight = + VRAI.futureWeight(LIS->getInterval(Evictee), + Cand.Intf.first().getPrevIndex(), Cand.Intf.last()); + if (splitArtifactWeight >= 0 && splitArtifactWeight < MaxWeight) + return false; + + return true; +} + +/// Check if splitting VirtRegToSplit will create a local split interval +/// in basic block number BBNumber that may cause a spill. +/// +/// \param VirtRegToSplit The register considered to be split. +/// \param Cand The split candidate that determines the physical +/// register we are splitting for and the interferences. +/// \param BBNumber The number of a BB for which the region split process +/// will create a local split interval. +/// \param Order The physical registers that may get evicted by a +/// split artifact of VirtRegToSplit. +/// \return True if splitting VirtRegToSplit may cause a spill, false +/// otherwise. +bool RAGreedy::splitCanCauseLocalSpill(unsigned VirtRegToSplit, + GlobalSplitCandidate &Cand, + unsigned BBNumber, + const AllocationOrder &Order) { + Cand.Intf.moveToBlock(BBNumber); + + // Check if the local interval will find a non interfereing assignment. + for (auto PhysReg : Order.getOrder()) { + if (!Matrix->checkInterference(Cand.Intf.first().getPrevIndex(), + Cand.Intf.last(), PhysReg)) + return false; + } + + // Check if the local interval will evict a cheaper interval. + float CheapestEvictWeight = 0; + unsigned FutureEvictedPhysReg = getCheapestEvicteeWeight( + Order, LIS->getInterval(VirtRegToSplit), Cand.Intf.first(), + Cand.Intf.last(), &CheapestEvictWeight); + + // Have we found an interval that can be evicted? + if (FutureEvictedPhysReg) { + VirtRegAuxInfo VRAI(*MF, *LIS, VRM, getAnalysis<MachineLoopInfo>(), *MBFI); + float splitArtifactWeight = + VRAI.futureWeight(LIS->getInterval(VirtRegToSplit), + Cand.Intf.first().getPrevIndex(), Cand.Intf.last()); + // Will the weight of the local interval be higher than the cheapest evictee + // weight? If so it will evict it and will not cause a spill. + if (splitArtifactWeight >= 0 && splitArtifactWeight > CheapestEvictWeight) + return false; + } + + // The local interval is not able to find non interferencing assignment and + // not able to evict a less worthy interval, therfore, it can cause a spill. + return true; +} + +/// calcGlobalSplitCost - Return the global split cost of following the split +/// pattern in LiveBundles. This cost should be added to the local cost of the +/// interference pattern in SplitConstraints. +/// +BlockFrequency RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand, + const AllocationOrder &Order, + bool *CanCauseEvictionChain) { + BlockFrequency GlobalCost = 0; + const BitVector &LiveBundles = Cand.LiveBundles; + unsigned VirtRegToSplit = SA->getParent().reg; + ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks(); + for (unsigned i = 0; i != UseBlocks.size(); ++i) { + const SplitAnalysis::BlockInfo &BI = UseBlocks[i]; + SpillPlacement::BlockConstraint &BC = SplitConstraints[i]; + bool RegIn = LiveBundles[Bundles->getBundle(BC.Number, false)]; + bool RegOut = LiveBundles[Bundles->getBundle(BC.Number, true)]; + unsigned Ins = 0; + + Cand.Intf.moveToBlock(BC.Number); + // Check wheather a local interval is going to be created during the region + // split. Calculate adavanced spilt cost (cost of local intervals) if option + // is enabled. + if (EnableAdvancedRASplitCost && Cand.Intf.hasInterference() && BI.LiveIn && + BI.LiveOut && RegIn && RegOut) { + + if (CanCauseEvictionChain && + splitCanCauseEvictionChain(VirtRegToSplit, Cand, BC.Number, Order)) { + // This interference causes our eviction from this assignment, we might + // evict somebody else and eventually someone will spill, add that cost. + // See splitCanCauseEvictionChain for detailed description of scenarios. + GlobalCost += SpillPlacer->getBlockFrequency(BC.Number); + GlobalCost += SpillPlacer->getBlockFrequency(BC.Number); + + *CanCauseEvictionChain = true; + + } else if (splitCanCauseLocalSpill(VirtRegToSplit, Cand, BC.Number, + Order)) { + // This interference causes local interval to spill, add that cost. + GlobalCost += SpillPlacer->getBlockFrequency(BC.Number); + GlobalCost += SpillPlacer->getBlockFrequency(BC.Number); + } + } + + if (BI.LiveIn) + Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg); + if (BI.LiveOut) + Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg); + while (Ins--) + GlobalCost += SpillPlacer->getBlockFrequency(BC.Number); + } + + for (unsigned i = 0, e = Cand.ActiveBlocks.size(); i != e; ++i) { + unsigned Number = Cand.ActiveBlocks[i]; + bool RegIn = LiveBundles[Bundles->getBundle(Number, false)]; + bool RegOut = LiveBundles[Bundles->getBundle(Number, true)]; + if (!RegIn && !RegOut) + continue; + if (RegIn && RegOut) { + // We need double spill code if this block has interference. + Cand.Intf.moveToBlock(Number); + if (Cand.Intf.hasInterference()) { + GlobalCost += SpillPlacer->getBlockFrequency(Number); + GlobalCost += SpillPlacer->getBlockFrequency(Number); + + // Check wheather a local interval is going to be created during the + // region split. + if (EnableAdvancedRASplitCost && CanCauseEvictionChain && + splitCanCauseEvictionChain(VirtRegToSplit, Cand, Number, Order)) { + // This interference cause our eviction from this assignment, we might + // evict somebody else, add that cost. + // See splitCanCauseEvictionChain for detailed description of + // scenarios. + GlobalCost += SpillPlacer->getBlockFrequency(Number); + GlobalCost += SpillPlacer->getBlockFrequency(Number); + + *CanCauseEvictionChain = true; + } + } + continue; + } + // live-in / stack-out or stack-in live-out. + GlobalCost += SpillPlacer->getBlockFrequency(Number); + } + return GlobalCost; +} + +/// splitAroundRegion - Split the current live range around the regions +/// determined by BundleCand and GlobalCand. +/// +/// Before calling this function, GlobalCand and BundleCand must be initialized +/// so each bundle is assigned to a valid candidate, or NoCand for the +/// stack-bound bundles. The shared SA/SE SplitAnalysis and SplitEditor +/// objects must be initialized for the current live range, and intervals +/// created for the used candidates. +/// +/// @param LREdit The LiveRangeEdit object handling the current split. +/// @param UsedCands List of used GlobalCand entries. Every BundleCand value +/// must appear in this list. +void RAGreedy::splitAroundRegion(LiveRangeEdit &LREdit, + ArrayRef<unsigned> UsedCands) { + // These are the intervals created for new global ranges. We may create more + // intervals for local ranges. + const unsigned NumGlobalIntvs = LREdit.size(); + LLVM_DEBUG(dbgs() << "splitAroundRegion with " << NumGlobalIntvs + << " globals.\n"); + assert(NumGlobalIntvs && "No global intervals configured"); + + // Isolate even single instructions when dealing with a proper sub-class. + // That guarantees register class inflation for the stack interval because it + // is all copies. + unsigned Reg = SA->getParent().reg; + bool SingleInstrs = RegClassInfo.isProperSubClass(MRI->getRegClass(Reg)); + + // First handle all the blocks with uses. + ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks(); + for (unsigned i = 0; i != UseBlocks.size(); ++i) { + const SplitAnalysis::BlockInfo &BI = UseBlocks[i]; + unsigned Number = BI.MBB->getNumber(); + unsigned IntvIn = 0, IntvOut = 0; + SlotIndex IntfIn, IntfOut; + if (BI.LiveIn) { + unsigned CandIn = BundleCand[Bundles->getBundle(Number, false)]; + if (CandIn != NoCand) { + GlobalSplitCandidate &Cand = GlobalCand[CandIn]; + IntvIn = Cand.IntvIdx; + Cand.Intf.moveToBlock(Number); + IntfIn = Cand.Intf.first(); + } + } + if (BI.LiveOut) { + unsigned CandOut = BundleCand[Bundles->getBundle(Number, true)]; + if (CandOut != NoCand) { + GlobalSplitCandidate &Cand = GlobalCand[CandOut]; + IntvOut = Cand.IntvIdx; + Cand.Intf.moveToBlock(Number); + IntfOut = Cand.Intf.last(); + } + } + + // Create separate intervals for isolated blocks with multiple uses. + if (!IntvIn && !IntvOut) { + LLVM_DEBUG(dbgs() << printMBBReference(*BI.MBB) << " isolated.\n"); + if (SA->shouldSplitSingleBlock(BI, SingleInstrs)) + SE->splitSingleBlock(BI); + continue; + } + + if (IntvIn && IntvOut) + SE->splitLiveThroughBlock(Number, IntvIn, IntfIn, IntvOut, IntfOut); + else if (IntvIn) + SE->splitRegInBlock(BI, IntvIn, IntfIn); + else + SE->splitRegOutBlock(BI, IntvOut, IntfOut); + } + + // Handle live-through blocks. The relevant live-through blocks are stored in + // the ActiveBlocks list with each candidate. We need to filter out + // duplicates. + BitVector Todo = SA->getThroughBlocks(); + for (unsigned c = 0; c != UsedCands.size(); ++c) { + ArrayRef<unsigned> Blocks = GlobalCand[UsedCands[c]].ActiveBlocks; + for (unsigned i = 0, e = Blocks.size(); i != e; ++i) { + unsigned Number = Blocks[i]; + if (!Todo.test(Number)) + continue; + Todo.reset(Number); + + unsigned IntvIn = 0, IntvOut = 0; + SlotIndex IntfIn, IntfOut; + + unsigned CandIn = BundleCand[Bundles->getBundle(Number, false)]; + if (CandIn != NoCand) { + GlobalSplitCandidate &Cand = GlobalCand[CandIn]; + IntvIn = Cand.IntvIdx; + Cand.Intf.moveToBlock(Number); + IntfIn = Cand.Intf.first(); + } + + unsigned CandOut = BundleCand[Bundles->getBundle(Number, true)]; + if (CandOut != NoCand) { + GlobalSplitCandidate &Cand = GlobalCand[CandOut]; + IntvOut = Cand.IntvIdx; + Cand.Intf.moveToBlock(Number); + IntfOut = Cand.Intf.last(); + } + if (!IntvIn && !IntvOut) + continue; + SE->splitLiveThroughBlock(Number, IntvIn, IntfIn, IntvOut, IntfOut); + } + } + + ++NumGlobalSplits; + + SmallVector<unsigned, 8> IntvMap; + SE->finish(&IntvMap); + DebugVars->splitRegister(Reg, LREdit.regs(), *LIS); + + ExtraRegInfo.resize(MRI->getNumVirtRegs()); + unsigned OrigBlocks = SA->getNumLiveBlocks(); + + // Sort out the new intervals created by splitting. We get four kinds: + // - Remainder intervals should not be split again. + // - Candidate intervals can be assigned to Cand.PhysReg. + // - Block-local splits are candidates for local splitting. + // - DCE leftovers should go back on the queue. + for (unsigned i = 0, e = LREdit.size(); i != e; ++i) { + LiveInterval &Reg = LIS->getInterval(LREdit.get(i)); + + // Ignore old intervals from DCE. + if (getStage(Reg) != RS_New) + continue; + + // Remainder interval. Don't try splitting again, spill if it doesn't + // allocate. + if (IntvMap[i] == 0) { + setStage(Reg, RS_Spill); + continue; + } + + // Global intervals. Allow repeated splitting as long as the number of live + // blocks is strictly decreasing. + if (IntvMap[i] < NumGlobalIntvs) { + if (SA->countLiveBlocks(&Reg) >= OrigBlocks) { + LLVM_DEBUG(dbgs() << "Main interval covers the same " << OrigBlocks + << " blocks as original.\n"); + // Don't allow repeated splitting as a safe guard against looping. + setStage(Reg, RS_Split2); + } + continue; + } + + // Other intervals are treated as new. This includes local intervals created + // for blocks with multiple uses, and anything created by DCE. + } + + if (VerifyEnabled) + MF->verify(this, "After splitting live range around region"); +} + +// Global split has high compile time cost especially for large live range. +// Return false for the case here where the potential benefit will never +// worth the cost. +unsigned RAGreedy::isSplitBenefitWorthCost(LiveInterval &VirtReg) { + MachineInstr *MI = MRI->getUniqueVRegDef(VirtReg.reg); + if (MI && TII->isTriviallyReMaterializable(*MI, AA) && + VirtReg.size() > HugeSizeForSplit) + return false; + return true; +} + +unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order, + SmallVectorImpl<unsigned> &NewVRegs) { + if (!isSplitBenefitWorthCost(VirtReg)) + return 0; + unsigned NumCands = 0; + BlockFrequency SpillCost = calcSpillCost(); + BlockFrequency BestCost; + + // Check if we can split this live range around a compact region. + bool HasCompact = calcCompactRegion(GlobalCand.front()); + if (HasCompact) { + // Yes, keep GlobalCand[0] as the compact region candidate. + NumCands = 1; + BestCost = BlockFrequency::getMaxFrequency(); + } else { + // No benefit from the compact region, our fallback will be per-block + // splitting. Make sure we find a solution that is cheaper than spilling. + BestCost = SpillCost; + LLVM_DEBUG(dbgs() << "Cost of isolating all blocks = "; + MBFI->printBlockFreq(dbgs(), BestCost) << '\n'); + } + + bool CanCauseEvictionChain = false; + unsigned BestCand = + calculateRegionSplitCost(VirtReg, Order, BestCost, NumCands, + false /*IgnoreCSR*/, &CanCauseEvictionChain); + + // Split candidates with compact regions can cause a bad eviction sequence. + // See splitCanCauseEvictionChain for detailed description of scenarios. + // To avoid it, we need to comapre the cost with the spill cost and not the + // current max frequency. + if (HasCompact && (BestCost > SpillCost) && (BestCand != NoCand) && + CanCauseEvictionChain) { + return 0; + } + + // No solutions found, fall back to single block splitting. + if (!HasCompact && BestCand == NoCand) + return 0; + + return doRegionSplit(VirtReg, BestCand, HasCompact, NewVRegs); +} + +unsigned RAGreedy::calculateRegionSplitCost(LiveInterval &VirtReg, + AllocationOrder &Order, + BlockFrequency &BestCost, + unsigned &NumCands, bool IgnoreCSR, + bool *CanCauseEvictionChain) { + unsigned BestCand = NoCand; + Order.rewind(); + while (unsigned PhysReg = Order.next()) { + if (IgnoreCSR && isUnusedCalleeSavedReg(PhysReg)) + continue; + + // Discard bad candidates before we run out of interference cache cursors. + // This will only affect register classes with a lot of registers (>32). + if (NumCands == IntfCache.getMaxCursors()) { + unsigned WorstCount = ~0u; + unsigned Worst = 0; + for (unsigned i = 0; i != NumCands; ++i) { + if (i == BestCand || !GlobalCand[i].PhysReg) + continue; + unsigned Count = GlobalCand[i].LiveBundles.count(); + if (Count < WorstCount) { + Worst = i; + WorstCount = Count; + } + } + --NumCands; + GlobalCand[Worst] = GlobalCand[NumCands]; + if (BestCand == NumCands) + BestCand = Worst; + } + + if (GlobalCand.size() <= NumCands) + GlobalCand.resize(NumCands+1); + GlobalSplitCandidate &Cand = GlobalCand[NumCands]; + Cand.reset(IntfCache, PhysReg); + + SpillPlacer->prepare(Cand.LiveBundles); + BlockFrequency Cost; + if (!addSplitConstraints(Cand.Intf, Cost)) { + LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << "\tno positive bundles\n"); + continue; + } + LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << "\tstatic = "; + MBFI->printBlockFreq(dbgs(), Cost)); + if (Cost >= BestCost) { + LLVM_DEBUG({ + if (BestCand == NoCand) + dbgs() << " worse than no bundles\n"; + else + dbgs() << " worse than " + << printReg(GlobalCand[BestCand].PhysReg, TRI) << '\n'; + }); + continue; + } + if (!growRegion(Cand)) { + LLVM_DEBUG(dbgs() << ", cannot spill all interferences.\n"); + continue; + } + + SpillPlacer->finish(); + + // No live bundles, defer to splitSingleBlocks(). + if (!Cand.LiveBundles.any()) { + LLVM_DEBUG(dbgs() << " no bundles.\n"); + continue; + } + + bool HasEvictionChain = false; + Cost += calcGlobalSplitCost(Cand, Order, &HasEvictionChain); + LLVM_DEBUG({ + dbgs() << ", total = "; + MBFI->printBlockFreq(dbgs(), Cost) << " with bundles"; + for (int i : Cand.LiveBundles.set_bits()) + dbgs() << " EB#" << i; + dbgs() << ".\n"; + }); + if (Cost < BestCost) { + BestCand = NumCands; + BestCost = Cost; + // See splitCanCauseEvictionChain for detailed description of bad + // eviction chain scenarios. + if (CanCauseEvictionChain) + *CanCauseEvictionChain = HasEvictionChain; + } + ++NumCands; + } + + if (CanCauseEvictionChain && BestCand != NoCand) { + // See splitCanCauseEvictionChain for detailed description of bad + // eviction chain scenarios. + LLVM_DEBUG(dbgs() << "Best split candidate of vreg " + << printReg(VirtReg.reg, TRI) << " may "); + if (!(*CanCauseEvictionChain)) + LLVM_DEBUG(dbgs() << "not "); + LLVM_DEBUG(dbgs() << "cause bad eviction chain\n"); + } + + return BestCand; +} + +unsigned RAGreedy::doRegionSplit(LiveInterval &VirtReg, unsigned BestCand, + bool HasCompact, + SmallVectorImpl<unsigned> &NewVRegs) { + SmallVector<unsigned, 8> UsedCands; + // Prepare split editor. + LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats); + SE->reset(LREdit, SplitSpillMode); + + // Assign all edge bundles to the preferred candidate, or NoCand. + BundleCand.assign(Bundles->getNumBundles(), NoCand); + + // Assign bundles for the best candidate region. + if (BestCand != NoCand) { + GlobalSplitCandidate &Cand = GlobalCand[BestCand]; + if (unsigned B = Cand.getBundles(BundleCand, BestCand)) { + UsedCands.push_back(BestCand); + Cand.IntvIdx = SE->openIntv(); + LLVM_DEBUG(dbgs() << "Split for " << printReg(Cand.PhysReg, TRI) << " in " + << B << " bundles, intv " << Cand.IntvIdx << ".\n"); + (void)B; + } + } + + // Assign bundles for the compact region. + if (HasCompact) { + GlobalSplitCandidate &Cand = GlobalCand.front(); + assert(!Cand.PhysReg && "Compact region has no physreg"); + if (unsigned B = Cand.getBundles(BundleCand, 0)) { + UsedCands.push_back(0); + Cand.IntvIdx = SE->openIntv(); + LLVM_DEBUG(dbgs() << "Split for compact region in " << B + << " bundles, intv " << Cand.IntvIdx << ".\n"); + (void)B; + } + } + + splitAroundRegion(LREdit, UsedCands); + return 0; +} + +//===----------------------------------------------------------------------===// +// Per-Block Splitting +//===----------------------------------------------------------------------===// + +/// tryBlockSplit - Split a global live range around every block with uses. This +/// creates a lot of local live ranges, that will be split by tryLocalSplit if +/// they don't allocate. +unsigned RAGreedy::tryBlockSplit(LiveInterval &VirtReg, AllocationOrder &Order, + SmallVectorImpl<unsigned> &NewVRegs) { + assert(&SA->getParent() == &VirtReg && "Live range wasn't analyzed"); + unsigned Reg = VirtReg.reg; + bool SingleInstrs = RegClassInfo.isProperSubClass(MRI->getRegClass(Reg)); + LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats); + SE->reset(LREdit, SplitSpillMode); + ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks(); + for (unsigned i = 0; i != UseBlocks.size(); ++i) { + const SplitAnalysis::BlockInfo &BI = UseBlocks[i]; + if (SA->shouldSplitSingleBlock(BI, SingleInstrs)) + SE->splitSingleBlock(BI); + } + // No blocks were split. + if (LREdit.empty()) + return 0; + + // We did split for some blocks. + SmallVector<unsigned, 8> IntvMap; + SE->finish(&IntvMap); + + // Tell LiveDebugVariables about the new ranges. + DebugVars->splitRegister(Reg, LREdit.regs(), *LIS); + + ExtraRegInfo.resize(MRI->getNumVirtRegs()); + + // Sort out the new intervals created by splitting. The remainder interval + // goes straight to spilling, the new local ranges get to stay RS_New. + for (unsigned i = 0, e = LREdit.size(); i != e; ++i) { + LiveInterval &LI = LIS->getInterval(LREdit.get(i)); + if (getStage(LI) == RS_New && IntvMap[i] == 0) + setStage(LI, RS_Spill); + } + + if (VerifyEnabled) + MF->verify(this, "After splitting live range around basic blocks"); + return 0; +} + +//===----------------------------------------------------------------------===// +// Per-Instruction Splitting +//===----------------------------------------------------------------------===// + +/// Get the number of allocatable registers that match the constraints of \p Reg +/// on \p MI and that are also in \p SuperRC. +static unsigned getNumAllocatableRegsForConstraints( + const MachineInstr *MI, unsigned Reg, const TargetRegisterClass *SuperRC, + const TargetInstrInfo *TII, const TargetRegisterInfo *TRI, + const RegisterClassInfo &RCI) { + assert(SuperRC && "Invalid register class"); + + const TargetRegisterClass *ConstrainedRC = + MI->getRegClassConstraintEffectForVReg(Reg, SuperRC, TII, TRI, + /* ExploreBundle */ true); + if (!ConstrainedRC) + return 0; + return RCI.getNumAllocatableRegs(ConstrainedRC); +} + +/// tryInstructionSplit - Split a live range around individual instructions. +/// This is normally not worthwhile since the spiller is doing essentially the +/// same thing. However, when the live range is in a constrained register +/// class, it may help to insert copies such that parts of the live range can +/// be moved to a larger register class. +/// +/// This is similar to spilling to a larger register class. +unsigned +RAGreedy::tryInstructionSplit(LiveInterval &VirtReg, AllocationOrder &Order, + SmallVectorImpl<unsigned> &NewVRegs) { + const TargetRegisterClass *CurRC = MRI->getRegClass(VirtReg.reg); + // There is no point to this if there are no larger sub-classes. + if (!RegClassInfo.isProperSubClass(CurRC)) + return 0; + + // Always enable split spill mode, since we're effectively spilling to a + // register. + LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats); + SE->reset(LREdit, SplitEditor::SM_Size); + + ArrayRef<SlotIndex> Uses = SA->getUseSlots(); + if (Uses.size() <= 1) + return 0; + + LLVM_DEBUG(dbgs() << "Split around " << Uses.size() + << " individual instrs.\n"); + + const TargetRegisterClass *SuperRC = + TRI->getLargestLegalSuperClass(CurRC, *MF); + unsigned SuperRCNumAllocatableRegs = RCI.getNumAllocatableRegs(SuperRC); + // Split around every non-copy instruction if this split will relax + // the constraints on the virtual register. + // Otherwise, splitting just inserts uncoalescable copies that do not help + // the allocation. + for (unsigned i = 0; i != Uses.size(); ++i) { + if (const MachineInstr *MI = Indexes->getInstructionFromIndex(Uses[i])) + if (MI->isFullCopy() || + SuperRCNumAllocatableRegs == + getNumAllocatableRegsForConstraints(MI, VirtReg.reg, SuperRC, TII, + TRI, RCI)) { + LLVM_DEBUG(dbgs() << " skip:\t" << Uses[i] << '\t' << *MI); + continue; + } + SE->openIntv(); + SlotIndex SegStart = SE->enterIntvBefore(Uses[i]); + SlotIndex SegStop = SE->leaveIntvAfter(Uses[i]); + SE->useIntv(SegStart, SegStop); + } + + if (LREdit.empty()) { + LLVM_DEBUG(dbgs() << "All uses were copies.\n"); + return 0; + } + + SmallVector<unsigned, 8> IntvMap; + SE->finish(&IntvMap); + DebugVars->splitRegister(VirtReg.reg, LREdit.regs(), *LIS); + ExtraRegInfo.resize(MRI->getNumVirtRegs()); + + // Assign all new registers to RS_Spill. This was the last chance. + setStage(LREdit.begin(), LREdit.end(), RS_Spill); + return 0; +} + +//===----------------------------------------------------------------------===// +// Local Splitting +//===----------------------------------------------------------------------===// + +/// calcGapWeights - Compute the maximum spill weight that needs to be evicted +/// in order to use PhysReg between two entries in SA->UseSlots. +/// +/// GapWeight[i] represents the gap between UseSlots[i] and UseSlots[i+1]. +/// +void RAGreedy::calcGapWeights(unsigned PhysReg, + SmallVectorImpl<float> &GapWeight) { + assert(SA->getUseBlocks().size() == 1 && "Not a local interval"); + const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front(); + ArrayRef<SlotIndex> Uses = SA->getUseSlots(); + const unsigned NumGaps = Uses.size()-1; + + // Start and end points for the interference check. + SlotIndex StartIdx = + BI.LiveIn ? BI.FirstInstr.getBaseIndex() : BI.FirstInstr; + SlotIndex StopIdx = + BI.LiveOut ? BI.LastInstr.getBoundaryIndex() : BI.LastInstr; + + GapWeight.assign(NumGaps, 0.0f); + + // Add interference from each overlapping register. + for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) { + if (!Matrix->query(const_cast<LiveInterval&>(SA->getParent()), *Units) + .checkInterference()) + continue; + + // We know that VirtReg is a continuous interval from FirstInstr to + // LastInstr, so we don't need InterferenceQuery. + // + // Interference that overlaps an instruction is counted in both gaps + // surrounding the instruction. The exception is interference before + // StartIdx and after StopIdx. + // + LiveIntervalUnion::SegmentIter IntI = + Matrix->getLiveUnions()[*Units] .find(StartIdx); + for (unsigned Gap = 0; IntI.valid() && IntI.start() < StopIdx; ++IntI) { + // Skip the gaps before IntI. + while (Uses[Gap+1].getBoundaryIndex() < IntI.start()) + if (++Gap == NumGaps) + break; + if (Gap == NumGaps) + break; + + // Update the gaps covered by IntI. + const float weight = IntI.value()->weight; + for (; Gap != NumGaps; ++Gap) { + GapWeight[Gap] = std::max(GapWeight[Gap], weight); + if (Uses[Gap+1].getBaseIndex() >= IntI.stop()) + break; + } + if (Gap == NumGaps) + break; + } + } + + // Add fixed interference. + for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) { + const LiveRange &LR = LIS->getRegUnit(*Units); + LiveRange::const_iterator I = LR.find(StartIdx); + LiveRange::const_iterator E = LR.end(); + + // Same loop as above. Mark any overlapped gaps as HUGE_VALF. + for (unsigned Gap = 0; I != E && I->start < StopIdx; ++I) { + while (Uses[Gap+1].getBoundaryIndex() < I->start) + if (++Gap == NumGaps) + break; + if (Gap == NumGaps) + break; + + for (; Gap != NumGaps; ++Gap) { + GapWeight[Gap] = huge_valf; + if (Uses[Gap+1].getBaseIndex() >= I->end) + break; + } + if (Gap == NumGaps) + break; + } + } +} + +/// tryLocalSplit - Try to split VirtReg into smaller intervals inside its only +/// basic block. +/// +unsigned RAGreedy::tryLocalSplit(LiveInterval &VirtReg, AllocationOrder &Order, + SmallVectorImpl<unsigned> &NewVRegs) { + // TODO: the function currently only handles a single UseBlock; it should be + // possible to generalize. + if (SA->getUseBlocks().size() != 1) + return 0; + + const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front(); + + // Note that it is possible to have an interval that is live-in or live-out + // while only covering a single block - A phi-def can use undef values from + // predecessors, and the block could be a single-block loop. + // We don't bother doing anything clever about such a case, we simply assume + // that the interval is continuous from FirstInstr to LastInstr. We should + // make sure that we don't do anything illegal to such an interval, though. + + ArrayRef<SlotIndex> Uses = SA->getUseSlots(); + if (Uses.size() <= 2) + return 0; + const unsigned NumGaps = Uses.size()-1; + + LLVM_DEBUG({ + dbgs() << "tryLocalSplit: "; + for (unsigned i = 0, e = Uses.size(); i != e; ++i) + dbgs() << ' ' << Uses[i]; + dbgs() << '\n'; + }); + + // If VirtReg is live across any register mask operands, compute a list of + // gaps with register masks. + SmallVector<unsigned, 8> RegMaskGaps; + if (Matrix->checkRegMaskInterference(VirtReg)) { + // Get regmask slots for the whole block. + ArrayRef<SlotIndex> RMS = LIS->getRegMaskSlotsInBlock(BI.MBB->getNumber()); + LLVM_DEBUG(dbgs() << RMS.size() << " regmasks in block:"); + // Constrain to VirtReg's live range. + unsigned ri = + llvm::lower_bound(RMS, Uses.front().getRegSlot()) - RMS.begin(); + unsigned re = RMS.size(); + for (unsigned i = 0; i != NumGaps && ri != re; ++i) { + // Look for Uses[i] <= RMS <= Uses[i+1]. + assert(!SlotIndex::isEarlierInstr(RMS[ri], Uses[i])); + if (SlotIndex::isEarlierInstr(Uses[i+1], RMS[ri])) + continue; + // Skip a regmask on the same instruction as the last use. It doesn't + // overlap the live range. + if (SlotIndex::isSameInstr(Uses[i+1], RMS[ri]) && i+1 == NumGaps) + break; + LLVM_DEBUG(dbgs() << ' ' << RMS[ri] << ':' << Uses[i] << '-' + << Uses[i + 1]); + RegMaskGaps.push_back(i); + // Advance ri to the next gap. A regmask on one of the uses counts in + // both gaps. + while (ri != re && SlotIndex::isEarlierInstr(RMS[ri], Uses[i+1])) + ++ri; + } + LLVM_DEBUG(dbgs() << '\n'); + } + + // Since we allow local split results to be split again, there is a risk of + // creating infinite loops. It is tempting to require that the new live + // ranges have less instructions than the original. That would guarantee + // convergence, but it is too strict. A live range with 3 instructions can be + // split 2+3 (including the COPY), and we want to allow that. + // + // Instead we use these rules: + // + // 1. Allow any split for ranges with getStage() < RS_Split2. (Except for the + // noop split, of course). + // 2. Require progress be made for ranges with getStage() == RS_Split2. All + // the new ranges must have fewer instructions than before the split. + // 3. New ranges with the same number of instructions are marked RS_Split2, + // smaller ranges are marked RS_New. + // + // These rules allow a 3 -> 2+3 split once, which we need. They also prevent + // excessive splitting and infinite loops. + // + bool ProgressRequired = getStage(VirtReg) >= RS_Split2; + + // Best split candidate. + unsigned BestBefore = NumGaps; + unsigned BestAfter = 0; + float BestDiff = 0; + + const float blockFreq = + SpillPlacer->getBlockFrequency(BI.MBB->getNumber()).getFrequency() * + (1.0f / MBFI->getEntryFreq()); + SmallVector<float, 8> GapWeight; + + Order.rewind(); + while (unsigned PhysReg = Order.next()) { + // Keep track of the largest spill weight that would need to be evicted in + // order to make use of PhysReg between UseSlots[i] and UseSlots[i+1]. + calcGapWeights(PhysReg, GapWeight); + + // Remove any gaps with regmask clobbers. + if (Matrix->checkRegMaskInterference(VirtReg, PhysReg)) + for (unsigned i = 0, e = RegMaskGaps.size(); i != e; ++i) + GapWeight[RegMaskGaps[i]] = huge_valf; + + // Try to find the best sequence of gaps to close. + // The new spill weight must be larger than any gap interference. + + // We will split before Uses[SplitBefore] and after Uses[SplitAfter]. + unsigned SplitBefore = 0, SplitAfter = 1; + + // MaxGap should always be max(GapWeight[SplitBefore..SplitAfter-1]). + // It is the spill weight that needs to be evicted. + float MaxGap = GapWeight[0]; + + while (true) { + // Live before/after split? + const bool LiveBefore = SplitBefore != 0 || BI.LiveIn; + const bool LiveAfter = SplitAfter != NumGaps || BI.LiveOut; + + LLVM_DEBUG(dbgs() << printReg(PhysReg, TRI) << ' ' << Uses[SplitBefore] + << '-' << Uses[SplitAfter] << " i=" << MaxGap); + + // Stop before the interval gets so big we wouldn't be making progress. + if (!LiveBefore && !LiveAfter) { + LLVM_DEBUG(dbgs() << " all\n"); + break; + } + // Should the interval be extended or shrunk? + bool Shrink = true; + + // How many gaps would the new range have? + unsigned NewGaps = LiveBefore + SplitAfter - SplitBefore + LiveAfter; + + // Legally, without causing looping? + bool Legal = !ProgressRequired || NewGaps < NumGaps; + + if (Legal && MaxGap < huge_valf) { + // Estimate the new spill weight. Each instruction reads or writes the + // register. Conservatively assume there are no read-modify-write + // instructions. + // + // Try to guess the size of the new interval. + const float EstWeight = normalizeSpillWeight( + blockFreq * (NewGaps + 1), + Uses[SplitBefore].distance(Uses[SplitAfter]) + + (LiveBefore + LiveAfter) * SlotIndex::InstrDist, + 1); + // Would this split be possible to allocate? + // Never allocate all gaps, we wouldn't be making progress. + LLVM_DEBUG(dbgs() << " w=" << EstWeight); + if (EstWeight * Hysteresis >= MaxGap) { + Shrink = false; + float Diff = EstWeight - MaxGap; + if (Diff > BestDiff) { + LLVM_DEBUG(dbgs() << " (best)"); + BestDiff = Hysteresis * Diff; + BestBefore = SplitBefore; + BestAfter = SplitAfter; + } + } + } + + // Try to shrink. + if (Shrink) { + if (++SplitBefore < SplitAfter) { + LLVM_DEBUG(dbgs() << " shrink\n"); + // Recompute the max when necessary. + if (GapWeight[SplitBefore - 1] >= MaxGap) { + MaxGap = GapWeight[SplitBefore]; + for (unsigned i = SplitBefore + 1; i != SplitAfter; ++i) + MaxGap = std::max(MaxGap, GapWeight[i]); + } + continue; + } + MaxGap = 0; + } + + // Try to extend the interval. + if (SplitAfter >= NumGaps) { + LLVM_DEBUG(dbgs() << " end\n"); + break; + } + + LLVM_DEBUG(dbgs() << " extend\n"); + MaxGap = std::max(MaxGap, GapWeight[SplitAfter++]); + } + } + + // Didn't find any candidates? + if (BestBefore == NumGaps) + return 0; + + LLVM_DEBUG(dbgs() << "Best local split range: " << Uses[BestBefore] << '-' + << Uses[BestAfter] << ", " << BestDiff << ", " + << (BestAfter - BestBefore + 1) << " instrs\n"); + + LiveRangeEdit LREdit(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats); + SE->reset(LREdit); + + SE->openIntv(); + SlotIndex SegStart = SE->enterIntvBefore(Uses[BestBefore]); + SlotIndex SegStop = SE->leaveIntvAfter(Uses[BestAfter]); + SE->useIntv(SegStart, SegStop); + SmallVector<unsigned, 8> IntvMap; + SE->finish(&IntvMap); + DebugVars->splitRegister(VirtReg.reg, LREdit.regs(), *LIS); + + // If the new range has the same number of instructions as before, mark it as + // RS_Split2 so the next split will be forced to make progress. Otherwise, + // leave the new intervals as RS_New so they can compete. + bool LiveBefore = BestBefore != 0 || BI.LiveIn; + bool LiveAfter = BestAfter != NumGaps || BI.LiveOut; + unsigned NewGaps = LiveBefore + BestAfter - BestBefore + LiveAfter; + if (NewGaps >= NumGaps) { + LLVM_DEBUG(dbgs() << "Tagging non-progress ranges: "); + assert(!ProgressRequired && "Didn't make progress when it was required."); + for (unsigned i = 0, e = IntvMap.size(); i != e; ++i) + if (IntvMap[i] == 1) { + setStage(LIS->getInterval(LREdit.get(i)), RS_Split2); + LLVM_DEBUG(dbgs() << printReg(LREdit.get(i))); + } + LLVM_DEBUG(dbgs() << '\n'); + } + ++NumLocalSplits; + + return 0; +} + +//===----------------------------------------------------------------------===// +// Live Range Splitting +//===----------------------------------------------------------------------===// + +/// trySplit - Try to split VirtReg or one of its interferences, making it +/// assignable. +/// @return Physreg when VirtReg may be assigned and/or new NewVRegs. +unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order, + SmallVectorImpl<unsigned>&NewVRegs, + const SmallVirtRegSet &FixedRegisters) { + // Ranges must be Split2 or less. + if (getStage(VirtReg) >= RS_Spill) + return 0; + + // Local intervals are handled separately. + if (LIS->intervalIsInOneMBB(VirtReg)) { + NamedRegionTimer T("local_split", "Local Splitting", TimerGroupName, + TimerGroupDescription, TimePassesIsEnabled); + SA->analyze(&VirtReg); + unsigned PhysReg = tryLocalSplit(VirtReg, Order, NewVRegs); + if (PhysReg || !NewVRegs.empty()) + return PhysReg; + return tryInstructionSplit(VirtReg, Order, NewVRegs); + } + + NamedRegionTimer T("global_split", "Global Splitting", TimerGroupName, + TimerGroupDescription, TimePassesIsEnabled); + + SA->analyze(&VirtReg); + + // FIXME: SplitAnalysis may repair broken live ranges coming from the + // coalescer. That may cause the range to become allocatable which means that + // tryRegionSplit won't be making progress. This check should be replaced with + // an assertion when the coalescer is fixed. + if (SA->didRepairRange()) { + // VirtReg has changed, so all cached queries are invalid. + Matrix->invalidateVirtRegs(); + if (unsigned PhysReg = tryAssign(VirtReg, Order, NewVRegs, FixedRegisters)) + return PhysReg; + } + + // First try to split around a region spanning multiple blocks. RS_Split2 + // ranges already made dubious progress with region splitting, so they go + // straight to single block splitting. + if (getStage(VirtReg) < RS_Split2) { + unsigned PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs); + if (PhysReg || !NewVRegs.empty()) + return PhysReg; + } + + // Then isolate blocks. + return tryBlockSplit(VirtReg, Order, NewVRegs); +} + +//===----------------------------------------------------------------------===// +// Last Chance Recoloring +//===----------------------------------------------------------------------===// + +/// Return true if \p reg has any tied def operand. +static bool hasTiedDef(MachineRegisterInfo *MRI, unsigned reg) { + for (const MachineOperand &MO : MRI->def_operands(reg)) + if (MO.isTied()) + return true; + + return false; +} + +/// mayRecolorAllInterferences - Check if the virtual registers that +/// interfere with \p VirtReg on \p PhysReg (or one of its aliases) may be +/// recolored to free \p PhysReg. +/// When true is returned, \p RecoloringCandidates has been augmented with all +/// the live intervals that need to be recolored in order to free \p PhysReg +/// for \p VirtReg. +/// \p FixedRegisters contains all the virtual registers that cannot be +/// recolored. +bool +RAGreedy::mayRecolorAllInterferences(unsigned PhysReg, LiveInterval &VirtReg, + SmallLISet &RecoloringCandidates, + const SmallVirtRegSet &FixedRegisters) { + const TargetRegisterClass *CurRC = MRI->getRegClass(VirtReg.reg); + + for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) { + LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units); + // If there is LastChanceRecoloringMaxInterference or more interferences, + // chances are one would not be recolorable. + if (Q.collectInterferingVRegs(LastChanceRecoloringMaxInterference) >= + LastChanceRecoloringMaxInterference && !ExhaustiveSearch) { + LLVM_DEBUG(dbgs() << "Early abort: too many interferences.\n"); + CutOffInfo |= CO_Interf; + return false; + } + for (unsigned i = Q.interferingVRegs().size(); i; --i) { + LiveInterval *Intf = Q.interferingVRegs()[i - 1]; + // If Intf is done and sit on the same register class as VirtReg, + // it would not be recolorable as it is in the same state as VirtReg. + // However, if VirtReg has tied defs and Intf doesn't, then + // there is still a point in examining if it can be recolorable. + if (((getStage(*Intf) == RS_Done && + MRI->getRegClass(Intf->reg) == CurRC) && + !(hasTiedDef(MRI, VirtReg.reg) && !hasTiedDef(MRI, Intf->reg))) || + FixedRegisters.count(Intf->reg)) { + LLVM_DEBUG( + dbgs() << "Early abort: the interference is not recolorable.\n"); + return false; + } + RecoloringCandidates.insert(Intf); + } + } + return true; +} + +/// tryLastChanceRecoloring - Try to assign a color to \p VirtReg by recoloring +/// its interferences. +/// Last chance recoloring chooses a color for \p VirtReg and recolors every +/// virtual register that was using it. The recoloring process may recursively +/// use the last chance recoloring. Therefore, when a virtual register has been +/// assigned a color by this mechanism, it is marked as Fixed, i.e., it cannot +/// be last-chance-recolored again during this recoloring "session". +/// E.g., +/// Let +/// vA can use {R1, R2 } +/// vB can use { R2, R3} +/// vC can use {R1 } +/// Where vA, vB, and vC cannot be split anymore (they are reloads for +/// instance) and they all interfere. +/// +/// vA is assigned R1 +/// vB is assigned R2 +/// vC tries to evict vA but vA is already done. +/// Regular register allocation fails. +/// +/// Last chance recoloring kicks in: +/// vC does as if vA was evicted => vC uses R1. +/// vC is marked as fixed. +/// vA needs to find a color. +/// None are available. +/// vA cannot evict vC: vC is a fixed virtual register now. +/// vA does as if vB was evicted => vA uses R2. +/// vB needs to find a color. +/// R3 is available. +/// Recoloring => vC = R1, vA = R2, vB = R3 +/// +/// \p Order defines the preferred allocation order for \p VirtReg. +/// \p NewRegs will contain any new virtual register that have been created +/// (split, spill) during the process and that must be assigned. +/// \p FixedRegisters contains all the virtual registers that cannot be +/// recolored. +/// \p Depth gives the current depth of the last chance recoloring. +/// \return a physical register that can be used for VirtReg or ~0u if none +/// exists. +unsigned RAGreedy::tryLastChanceRecoloring(LiveInterval &VirtReg, + AllocationOrder &Order, + SmallVectorImpl<unsigned> &NewVRegs, + SmallVirtRegSet &FixedRegisters, + unsigned Depth) { + LLVM_DEBUG(dbgs() << "Try last chance recoloring for " << VirtReg << '\n'); + // Ranges must be Done. + assert((getStage(VirtReg) >= RS_Done || !VirtReg.isSpillable()) && + "Last chance recoloring should really be last chance"); + // Set the max depth to LastChanceRecoloringMaxDepth. + // We may want to reconsider that if we end up with a too large search space + // for target with hundreds of registers. + // Indeed, in that case we may want to cut the search space earlier. + if (Depth >= LastChanceRecoloringMaxDepth && !ExhaustiveSearch) { + LLVM_DEBUG(dbgs() << "Abort because max depth has been reached.\n"); + CutOffInfo |= CO_Depth; + return ~0u; + } + + // Set of Live intervals that will need to be recolored. + SmallLISet RecoloringCandidates; + // Record the original mapping virtual register to physical register in case + // the recoloring fails. + DenseMap<unsigned, unsigned> VirtRegToPhysReg; + // Mark VirtReg as fixed, i.e., it will not be recolored pass this point in + // this recoloring "session". + assert(!FixedRegisters.count(VirtReg.reg)); + FixedRegisters.insert(VirtReg.reg); + SmallVector<unsigned, 4> CurrentNewVRegs; + + Order.rewind(); + while (unsigned PhysReg = Order.next()) { + LLVM_DEBUG(dbgs() << "Try to assign: " << VirtReg << " to " + << printReg(PhysReg, TRI) << '\n'); + RecoloringCandidates.clear(); + VirtRegToPhysReg.clear(); + CurrentNewVRegs.clear(); + + // It is only possible to recolor virtual register interference. + if (Matrix->checkInterference(VirtReg, PhysReg) > + LiveRegMatrix::IK_VirtReg) { + LLVM_DEBUG( + dbgs() << "Some interferences are not with virtual registers.\n"); + + continue; + } + + // Early give up on this PhysReg if it is obvious we cannot recolor all + // the interferences. + if (!mayRecolorAllInterferences(PhysReg, VirtReg, RecoloringCandidates, + FixedRegisters)) { + LLVM_DEBUG(dbgs() << "Some interferences cannot be recolored.\n"); + continue; + } + + // RecoloringCandidates contains all the virtual registers that interfer + // with VirtReg on PhysReg (or one of its aliases). + // Enqueue them for recoloring and perform the actual recoloring. + PQueue RecoloringQueue; + for (SmallLISet::iterator It = RecoloringCandidates.begin(), + EndIt = RecoloringCandidates.end(); + It != EndIt; ++It) { + unsigned ItVirtReg = (*It)->reg; + enqueue(RecoloringQueue, *It); + assert(VRM->hasPhys(ItVirtReg) && + "Interferences are supposed to be with allocated variables"); + + // Record the current allocation. + VirtRegToPhysReg[ItVirtReg] = VRM->getPhys(ItVirtReg); + // unset the related struct. + Matrix->unassign(**It); + } + + // Do as if VirtReg was assigned to PhysReg so that the underlying + // recoloring has the right information about the interferes and + // available colors. + Matrix->assign(VirtReg, PhysReg); + + // Save the current recoloring state. + // If we cannot recolor all the interferences, we will have to start again + // at this point for the next physical register. + SmallVirtRegSet SaveFixedRegisters(FixedRegisters); + if (tryRecoloringCandidates(RecoloringQueue, CurrentNewVRegs, + FixedRegisters, Depth)) { + // Push the queued vregs into the main queue. + for (unsigned NewVReg : CurrentNewVRegs) + NewVRegs.push_back(NewVReg); + // Do not mess up with the global assignment process. + // I.e., VirtReg must be unassigned. + Matrix->unassign(VirtReg); + return PhysReg; + } + + LLVM_DEBUG(dbgs() << "Fail to assign: " << VirtReg << " to " + << printReg(PhysReg, TRI) << '\n'); + + // The recoloring attempt failed, undo the changes. + FixedRegisters = SaveFixedRegisters; + Matrix->unassign(VirtReg); + + // For a newly created vreg which is also in RecoloringCandidates, + // don't add it to NewVRegs because its physical register will be restored + // below. Other vregs in CurrentNewVRegs are created by calling + // selectOrSplit and should be added into NewVRegs. + for (SmallVectorImpl<unsigned>::iterator Next = CurrentNewVRegs.begin(), + End = CurrentNewVRegs.end(); + Next != End; ++Next) { + if (RecoloringCandidates.count(&LIS->getInterval(*Next))) + continue; + NewVRegs.push_back(*Next); + } + + for (SmallLISet::iterator It = RecoloringCandidates.begin(), + EndIt = RecoloringCandidates.end(); + It != EndIt; ++It) { + unsigned ItVirtReg = (*It)->reg; + if (VRM->hasPhys(ItVirtReg)) + Matrix->unassign(**It); + unsigned ItPhysReg = VirtRegToPhysReg[ItVirtReg]; + Matrix->assign(**It, ItPhysReg); + } + } + + // Last chance recoloring did not worked either, give up. + return ~0u; +} + +/// tryRecoloringCandidates - Try to assign a new color to every register +/// in \RecoloringQueue. +/// \p NewRegs will contain any new virtual register created during the +/// recoloring process. +/// \p FixedRegisters[in/out] contains all the registers that have been +/// recolored. +/// \return true if all virtual registers in RecoloringQueue were successfully +/// recolored, false otherwise. +bool RAGreedy::tryRecoloringCandidates(PQueue &RecoloringQueue, + SmallVectorImpl<unsigned> &NewVRegs, + SmallVirtRegSet &FixedRegisters, + unsigned Depth) { + while (!RecoloringQueue.empty()) { + LiveInterval *LI = dequeue(RecoloringQueue); + LLVM_DEBUG(dbgs() << "Try to recolor: " << *LI << '\n'); + unsigned PhysReg; + PhysReg = selectOrSplitImpl(*LI, NewVRegs, FixedRegisters, Depth + 1); + // When splitting happens, the live-range may actually be empty. + // In that case, this is okay to continue the recoloring even + // if we did not find an alternative color for it. Indeed, + // there will not be anything to color for LI in the end. + if (PhysReg == ~0u || (!PhysReg && !LI->empty())) + return false; + + if (!PhysReg) { + assert(LI->empty() && "Only empty live-range do not require a register"); + LLVM_DEBUG(dbgs() << "Recoloring of " << *LI + << " succeeded. Empty LI.\n"); + continue; + } + LLVM_DEBUG(dbgs() << "Recoloring of " << *LI + << " succeeded with: " << printReg(PhysReg, TRI) << '\n'); + + Matrix->assign(*LI, PhysReg); + FixedRegisters.insert(LI->reg); + } + return true; +} + +//===----------------------------------------------------------------------===// +// Main Entry Point +//===----------------------------------------------------------------------===// + +unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg, + SmallVectorImpl<unsigned> &NewVRegs) { + CutOffInfo = CO_None; + LLVMContext &Ctx = MF->getFunction().getContext(); + SmallVirtRegSet FixedRegisters; + unsigned Reg = selectOrSplitImpl(VirtReg, NewVRegs, FixedRegisters); + if (Reg == ~0U && (CutOffInfo != CO_None)) { + uint8_t CutOffEncountered = CutOffInfo & (CO_Depth | CO_Interf); + if (CutOffEncountered == CO_Depth) + Ctx.emitError("register allocation failed: maximum depth for recoloring " + "reached. Use -fexhaustive-register-search to skip " + "cutoffs"); + else if (CutOffEncountered == CO_Interf) + Ctx.emitError("register allocation failed: maximum interference for " + "recoloring reached. Use -fexhaustive-register-search " + "to skip cutoffs"); + else if (CutOffEncountered == (CO_Depth | CO_Interf)) + Ctx.emitError("register allocation failed: maximum interference and " + "depth for recoloring reached. Use " + "-fexhaustive-register-search to skip cutoffs"); + } + return Reg; +} + +/// Using a CSR for the first time has a cost because it causes push|pop +/// to be added to prologue|epilogue. Splitting a cold section of the live +/// range can have lower cost than using the CSR for the first time; +/// Spilling a live range in the cold path can have lower cost than using +/// the CSR for the first time. Returns the physical register if we decide +/// to use the CSR; otherwise return 0. +unsigned RAGreedy::tryAssignCSRFirstTime(LiveInterval &VirtReg, + AllocationOrder &Order, + unsigned PhysReg, + unsigned &CostPerUseLimit, + SmallVectorImpl<unsigned> &NewVRegs) { + if (getStage(VirtReg) == RS_Spill && VirtReg.isSpillable()) { + // We choose spill over using the CSR for the first time if the spill cost + // is lower than CSRCost. + SA->analyze(&VirtReg); + if (calcSpillCost() >= CSRCost) + return PhysReg; + + // We are going to spill, set CostPerUseLimit to 1 to make sure that + // we will not use a callee-saved register in tryEvict. + CostPerUseLimit = 1; + return 0; + } + if (getStage(VirtReg) < RS_Split) { + // We choose pre-splitting over using the CSR for the first time if + // the cost of splitting is lower than CSRCost. + SA->analyze(&VirtReg); + unsigned NumCands = 0; + BlockFrequency BestCost = CSRCost; // Don't modify CSRCost. + unsigned BestCand = calculateRegionSplitCost(VirtReg, Order, BestCost, + NumCands, true /*IgnoreCSR*/); + if (BestCand == NoCand) + // Use the CSR if we can't find a region split below CSRCost. + return PhysReg; + + // Perform the actual pre-splitting. + doRegionSplit(VirtReg, BestCand, false/*HasCompact*/, NewVRegs); + return 0; + } + return PhysReg; +} + +void RAGreedy::aboutToRemoveInterval(LiveInterval &LI) { + // Do not keep invalid information around. + SetOfBrokenHints.remove(&LI); +} + +void RAGreedy::initializeCSRCost() { + // We use the larger one out of the command-line option and the value report + // by TRI. + CSRCost = BlockFrequency( + std::max((unsigned)CSRFirstTimeCost, TRI->getCSRFirstUseCost())); + if (!CSRCost.getFrequency()) + return; + + // Raw cost is relative to Entry == 2^14; scale it appropriately. + uint64_t ActualEntry = MBFI->getEntryFreq(); + if (!ActualEntry) { + CSRCost = 0; + return; + } + uint64_t FixedEntry = 1 << 14; + if (ActualEntry < FixedEntry) + CSRCost *= BranchProbability(ActualEntry, FixedEntry); + else if (ActualEntry <= UINT32_MAX) + // Invert the fraction and divide. + CSRCost /= BranchProbability(FixedEntry, ActualEntry); + else + // Can't use BranchProbability in general, since it takes 32-bit numbers. + CSRCost = CSRCost.getFrequency() * (ActualEntry / FixedEntry); +} + +/// Collect the hint info for \p Reg. +/// The results are stored into \p Out. +/// \p Out is not cleared before being populated. +void RAGreedy::collectHintInfo(unsigned Reg, HintsInfo &Out) { + for (const MachineInstr &Instr : MRI->reg_nodbg_instructions(Reg)) { + if (!Instr.isFullCopy()) + continue; + // Look for the other end of the copy. + Register OtherReg = Instr.getOperand(0).getReg(); + if (OtherReg == Reg) { + OtherReg = Instr.getOperand(1).getReg(); + if (OtherReg == Reg) + continue; + } + // Get the current assignment. + Register OtherPhysReg = Register::isPhysicalRegister(OtherReg) + ? OtherReg + : VRM->getPhys(OtherReg); + // Push the collected information. + Out.push_back(HintInfo(MBFI->getBlockFreq(Instr.getParent()), OtherReg, + OtherPhysReg)); + } +} + +/// Using the given \p List, compute the cost of the broken hints if +/// \p PhysReg was used. +/// \return The cost of \p List for \p PhysReg. +BlockFrequency RAGreedy::getBrokenHintFreq(const HintsInfo &List, + unsigned PhysReg) { + BlockFrequency Cost = 0; + for (const HintInfo &Info : List) { + if (Info.PhysReg != PhysReg) + Cost += Info.Freq; + } + return Cost; +} + +/// Using the register assigned to \p VirtReg, try to recolor +/// all the live ranges that are copy-related with \p VirtReg. +/// The recoloring is then propagated to all the live-ranges that have +/// been recolored and so on, until no more copies can be coalesced or +/// it is not profitable. +/// For a given live range, profitability is determined by the sum of the +/// frequencies of the non-identity copies it would introduce with the old +/// and new register. +void RAGreedy::tryHintRecoloring(LiveInterval &VirtReg) { + // We have a broken hint, check if it is possible to fix it by + // reusing PhysReg for the copy-related live-ranges. Indeed, we evicted + // some register and PhysReg may be available for the other live-ranges. + SmallSet<unsigned, 4> Visited; + SmallVector<unsigned, 2> RecoloringCandidates; + HintsInfo Info; + unsigned Reg = VirtReg.reg; + Register PhysReg = VRM->getPhys(Reg); + // Start the recoloring algorithm from the input live-interval, then + // it will propagate to the ones that are copy-related with it. + Visited.insert(Reg); + RecoloringCandidates.push_back(Reg); + + LLVM_DEBUG(dbgs() << "Trying to reconcile hints for: " << printReg(Reg, TRI) + << '(' << printReg(PhysReg, TRI) << ")\n"); + + do { + Reg = RecoloringCandidates.pop_back_val(); + + // We cannot recolor physical register. + if (Register::isPhysicalRegister(Reg)) + continue; + + assert(VRM->hasPhys(Reg) && "We have unallocated variable!!"); + + // Get the live interval mapped with this virtual register to be able + // to check for the interference with the new color. + LiveInterval &LI = LIS->getInterval(Reg); + Register CurrPhys = VRM->getPhys(Reg); + // Check that the new color matches the register class constraints and + // that it is free for this live range. + if (CurrPhys != PhysReg && (!MRI->getRegClass(Reg)->contains(PhysReg) || + Matrix->checkInterference(LI, PhysReg))) + continue; + + LLVM_DEBUG(dbgs() << printReg(Reg, TRI) << '(' << printReg(CurrPhys, TRI) + << ") is recolorable.\n"); + + // Gather the hint info. + Info.clear(); + collectHintInfo(Reg, Info); + // Check if recoloring the live-range will increase the cost of the + // non-identity copies. + if (CurrPhys != PhysReg) { + LLVM_DEBUG(dbgs() << "Checking profitability:\n"); + BlockFrequency OldCopiesCost = getBrokenHintFreq(Info, CurrPhys); + BlockFrequency NewCopiesCost = getBrokenHintFreq(Info, PhysReg); + LLVM_DEBUG(dbgs() << "Old Cost: " << OldCopiesCost.getFrequency() + << "\nNew Cost: " << NewCopiesCost.getFrequency() + << '\n'); + if (OldCopiesCost < NewCopiesCost) { + LLVM_DEBUG(dbgs() << "=> Not profitable.\n"); + continue; + } + // At this point, the cost is either cheaper or equal. If it is + // equal, we consider this is profitable because it may expose + // more recoloring opportunities. + LLVM_DEBUG(dbgs() << "=> Profitable.\n"); + // Recolor the live-range. + Matrix->unassign(LI); + Matrix->assign(LI, PhysReg); + } + // Push all copy-related live-ranges to keep reconciling the broken + // hints. + for (const HintInfo &HI : Info) { + if (Visited.insert(HI.Reg).second) + RecoloringCandidates.push_back(HI.Reg); + } + } while (!RecoloringCandidates.empty()); +} + +/// Try to recolor broken hints. +/// Broken hints may be repaired by recoloring when an evicted variable +/// freed up a register for a larger live-range. +/// Consider the following example: +/// BB1: +/// a = +/// b = +/// BB2: +/// ... +/// = b +/// = a +/// Let us assume b gets split: +/// BB1: +/// a = +/// b = +/// BB2: +/// c = b +/// ... +/// d = c +/// = d +/// = a +/// Because of how the allocation work, b, c, and d may be assigned different +/// colors. Now, if a gets evicted later: +/// BB1: +/// a = +/// st a, SpillSlot +/// b = +/// BB2: +/// c = b +/// ... +/// d = c +/// = d +/// e = ld SpillSlot +/// = e +/// This is likely that we can assign the same register for b, c, and d, +/// getting rid of 2 copies. +void RAGreedy::tryHintsRecoloring() { + for (LiveInterval *LI : SetOfBrokenHints) { + assert(Register::isVirtualRegister(LI->reg) && + "Recoloring is possible only for virtual registers"); + // Some dead defs may be around (e.g., because of debug uses). + // Ignore those. + if (!VRM->hasPhys(LI->reg)) + continue; + tryHintRecoloring(*LI); + } +} + +unsigned RAGreedy::selectOrSplitImpl(LiveInterval &VirtReg, + SmallVectorImpl<unsigned> &NewVRegs, + SmallVirtRegSet &FixedRegisters, + unsigned Depth) { + unsigned CostPerUseLimit = ~0u; + // First try assigning a free register. + AllocationOrder Order(VirtReg.reg, *VRM, RegClassInfo, Matrix); + if (unsigned PhysReg = tryAssign(VirtReg, Order, NewVRegs, FixedRegisters)) { + // If VirtReg got an assignment, the eviction info is no longre relevant. + LastEvicted.clearEvicteeInfo(VirtReg.reg); + // When NewVRegs is not empty, we may have made decisions such as evicting + // a virtual register, go with the earlier decisions and use the physical + // register. + if (CSRCost.getFrequency() && isUnusedCalleeSavedReg(PhysReg) && + NewVRegs.empty()) { + unsigned CSRReg = tryAssignCSRFirstTime(VirtReg, Order, PhysReg, + CostPerUseLimit, NewVRegs); + if (CSRReg || !NewVRegs.empty()) + // Return now if we decide to use a CSR or create new vregs due to + // pre-splitting. + return CSRReg; + } else + return PhysReg; + } + + LiveRangeStage Stage = getStage(VirtReg); + LLVM_DEBUG(dbgs() << StageName[Stage] << " Cascade " + << ExtraRegInfo[VirtReg.reg].Cascade << '\n'); + + // Try to evict a less worthy live range, but only for ranges from the primary + // queue. The RS_Split ranges already failed to do this, and they should not + // get a second chance until they have been split. + if (Stage != RS_Split) + if (unsigned PhysReg = + tryEvict(VirtReg, Order, NewVRegs, CostPerUseLimit, + FixedRegisters)) { + unsigned Hint = MRI->getSimpleHint(VirtReg.reg); + // If VirtReg has a hint and that hint is broken record this + // virtual register as a recoloring candidate for broken hint. + // Indeed, since we evicted a variable in its neighborhood it is + // likely we can at least partially recolor some of the + // copy-related live-ranges. + if (Hint && Hint != PhysReg) + SetOfBrokenHints.insert(&VirtReg); + // If VirtReg eviction someone, the eviction info for it as an evictee is + // no longre relevant. + LastEvicted.clearEvicteeInfo(VirtReg.reg); + return PhysReg; + } + + assert((NewVRegs.empty() || Depth) && "Cannot append to existing NewVRegs"); + + // The first time we see a live range, don't try to split or spill. + // Wait until the second time, when all smaller ranges have been allocated. + // This gives a better picture of the interference to split around. + if (Stage < RS_Split) { + setStage(VirtReg, RS_Split); + LLVM_DEBUG(dbgs() << "wait for second round\n"); + NewVRegs.push_back(VirtReg.reg); + return 0; + } + + if (Stage < RS_Spill) { + // Try splitting VirtReg or interferences. + unsigned NewVRegSizeBefore = NewVRegs.size(); + unsigned PhysReg = trySplit(VirtReg, Order, NewVRegs, FixedRegisters); + if (PhysReg || (NewVRegs.size() - NewVRegSizeBefore)) { + // If VirtReg got split, the eviction info is no longre relevant. + LastEvicted.clearEvicteeInfo(VirtReg.reg); + return PhysReg; + } + } + + // If we couldn't allocate a register from spilling, there is probably some + // invalid inline assembly. The base class will report it. + if (Stage >= RS_Done || !VirtReg.isSpillable()) + return tryLastChanceRecoloring(VirtReg, Order, NewVRegs, FixedRegisters, + Depth); + + // Finally spill VirtReg itself. + if (EnableDeferredSpilling && getStage(VirtReg) < RS_Memory) { + // TODO: This is experimental and in particular, we do not model + // the live range splitting done by spilling correctly. + // We would need a deep integration with the spiller to do the + // right thing here. Anyway, that is still good for early testing. + setStage(VirtReg, RS_Memory); + LLVM_DEBUG(dbgs() << "Do as if this register is in memory\n"); + NewVRegs.push_back(VirtReg.reg); + } else { + NamedRegionTimer T("spill", "Spiller", TimerGroupName, + TimerGroupDescription, TimePassesIsEnabled); + LiveRangeEdit LRE(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats); + spiller().spill(LRE); + setStage(NewVRegs.begin(), NewVRegs.end(), RS_Done); + + if (VerifyEnabled) + MF->verify(this, "After spilling"); + } + + // The live virtual register requesting allocation was spilled, so tell + // the caller not to allocate anything during this round. + return 0; +} + +void RAGreedy::reportNumberOfSplillsReloads(MachineLoop *L, unsigned &Reloads, + unsigned &FoldedReloads, + unsigned &Spills, + unsigned &FoldedSpills) { + Reloads = 0; + FoldedReloads = 0; + Spills = 0; + FoldedSpills = 0; + + // Sum up the spill and reloads in subloops. + for (MachineLoop *SubLoop : *L) { + unsigned SubReloads; + unsigned SubFoldedReloads; + unsigned SubSpills; + unsigned SubFoldedSpills; + + reportNumberOfSplillsReloads(SubLoop, SubReloads, SubFoldedReloads, + SubSpills, SubFoldedSpills); + Reloads += SubReloads; + FoldedReloads += SubFoldedReloads; + Spills += SubSpills; + FoldedSpills += SubFoldedSpills; + } + + const MachineFrameInfo &MFI = MF->getFrameInfo(); + const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo(); + int FI; + + for (MachineBasicBlock *MBB : L->getBlocks()) + // Handle blocks that were not included in subloops. + if (Loops->getLoopFor(MBB) == L) + for (MachineInstr &MI : *MBB) { + SmallVector<const MachineMemOperand *, 2> Accesses; + auto isSpillSlotAccess = [&MFI](const MachineMemOperand *A) { + return MFI.isSpillSlotObjectIndex( + cast<FixedStackPseudoSourceValue>(A->getPseudoValue()) + ->getFrameIndex()); + }; + + if (TII->isLoadFromStackSlot(MI, FI) && MFI.isSpillSlotObjectIndex(FI)) + ++Reloads; + else if (TII->hasLoadFromStackSlot(MI, Accesses) && + llvm::any_of(Accesses, isSpillSlotAccess)) + ++FoldedReloads; + else if (TII->isStoreToStackSlot(MI, FI) && + MFI.isSpillSlotObjectIndex(FI)) + ++Spills; + else if (TII->hasStoreToStackSlot(MI, Accesses) && + llvm::any_of(Accesses, isSpillSlotAccess)) + ++FoldedSpills; + } + + if (Reloads || FoldedReloads || Spills || FoldedSpills) { + using namespace ore; + + ORE->emit([&]() { + MachineOptimizationRemarkMissed R(DEBUG_TYPE, "LoopSpillReload", + L->getStartLoc(), L->getHeader()); + if (Spills) + R << NV("NumSpills", Spills) << " spills "; + if (FoldedSpills) + R << NV("NumFoldedSpills", FoldedSpills) << " folded spills "; + if (Reloads) + R << NV("NumReloads", Reloads) << " reloads "; + if (FoldedReloads) + R << NV("NumFoldedReloads", FoldedReloads) << " folded reloads "; + R << "generated in loop"; + return R; + }); + } +} + +bool RAGreedy::runOnMachineFunction(MachineFunction &mf) { + LLVM_DEBUG(dbgs() << "********** GREEDY REGISTER ALLOCATION **********\n" + << "********** Function: " << mf.getName() << '\n'); + + MF = &mf; + TRI = MF->getSubtarget().getRegisterInfo(); + TII = MF->getSubtarget().getInstrInfo(); + RCI.runOnMachineFunction(mf); + + EnableLocalReassign = EnableLocalReassignment || + MF->getSubtarget().enableRALocalReassignment( + MF->getTarget().getOptLevel()); + + EnableAdvancedRASplitCost = ConsiderLocalIntervalCost || + MF->getSubtarget().enableAdvancedRASplitCost(); + + if (VerifyEnabled) + MF->verify(this, "Before greedy register allocator"); + + RegAllocBase::init(getAnalysis<VirtRegMap>(), + getAnalysis<LiveIntervals>(), + getAnalysis<LiveRegMatrix>()); + Indexes = &getAnalysis<SlotIndexes>(); + MBFI = &getAnalysis<MachineBlockFrequencyInfo>(); + DomTree = &getAnalysis<MachineDominatorTree>(); + ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE(); + SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM)); + Loops = &getAnalysis<MachineLoopInfo>(); + Bundles = &getAnalysis<EdgeBundles>(); + SpillPlacer = &getAnalysis<SpillPlacement>(); + DebugVars = &getAnalysis<LiveDebugVariables>(); + AA = &getAnalysis<AAResultsWrapperPass>().getAAResults(); + + initializeCSRCost(); + + calculateSpillWeightsAndHints(*LIS, mf, VRM, *Loops, *MBFI); + + LLVM_DEBUG(LIS->dump()); + + SA.reset(new SplitAnalysis(*VRM, *LIS, *Loops)); + SE.reset(new SplitEditor(*SA, *AA, *LIS, *VRM, *DomTree, *MBFI)); + ExtraRegInfo.clear(); + ExtraRegInfo.resize(MRI->getNumVirtRegs()); + NextCascade = 1; + IntfCache.init(MF, Matrix->getLiveUnions(), Indexes, LIS, TRI); + GlobalCand.resize(32); // This will grow as needed. + SetOfBrokenHints.clear(); + LastEvicted.clear(); + + allocatePhysRegs(); + tryHintsRecoloring(); + postOptimization(); + reportNumberOfSplillsReloads(); + + releaseMemory(); + return true; +} |