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https://github.com/c64scene-ar/llvm-6502.git
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66446c803a
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130596 91177308-0d34-0410-b5e6-96231b3b80d8
1430 lines
51 KiB
C++
1430 lines
51 KiB
C++
//===-- RegAllocGreedy.cpp - greedy register allocator --------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the RAGreedy function pass for register allocation in
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// optimized builds.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "regalloc"
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#include "AllocationOrder.h"
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#include "InterferenceCache.h"
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#include "LiveDebugVariables.h"
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#include "LiveRangeEdit.h"
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#include "RegAllocBase.h"
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#include "Spiller.h"
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#include "SpillPlacement.h"
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#include "SplitKit.h"
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#include "VirtRegMap.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Function.h"
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#include "llvm/PassAnalysisSupport.h"
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#include "llvm/CodeGen/CalcSpillWeights.h"
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#include "llvm/CodeGen/EdgeBundles.h"
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#include "llvm/CodeGen/LiveIntervalAnalysis.h"
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#include "llvm/CodeGen/LiveStackAnalysis.h"
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#include "llvm/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/CodeGen/MachineLoopRanges.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/RegAllocRegistry.h"
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#include "llvm/CodeGen/RegisterCoalescer.h"
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#include "llvm/Target/TargetOptions.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/Timer.h"
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#include <queue>
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using namespace llvm;
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STATISTIC(NumGlobalSplits, "Number of split global live ranges");
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STATISTIC(NumLocalSplits, "Number of split local live ranges");
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STATISTIC(NumEvicted, "Number of interferences evicted");
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static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator",
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createGreedyRegisterAllocator);
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namespace {
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class RAGreedy : public MachineFunctionPass,
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public RegAllocBase,
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private LiveRangeEdit::Delegate {
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// context
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MachineFunction *MF;
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BitVector ReservedRegs;
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// analyses
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SlotIndexes *Indexes;
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LiveStacks *LS;
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MachineDominatorTree *DomTree;
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MachineLoopInfo *Loops;
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MachineLoopRanges *LoopRanges;
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EdgeBundles *Bundles;
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SpillPlacement *SpillPlacer;
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// state
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std::auto_ptr<Spiller> SpillerInstance;
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std::priority_queue<std::pair<unsigned, unsigned> > Queue;
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// Live ranges pass through a number of stages as we try to allocate them.
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// Some of the stages may also create new live ranges:
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//
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// - Region splitting.
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// - Per-block splitting.
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// - Local splitting.
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// - Spilling.
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//
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// Ranges produced by one of the stages skip the previous stages when they are
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// dequeued. This improves performance because we can skip interference checks
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// that are unlikely to give any results. It also guarantees that the live
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// range splitting algorithm terminates, something that is otherwise hard to
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// ensure.
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enum LiveRangeStage {
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RS_New, ///< Never seen before.
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RS_First, ///< First time in the queue.
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RS_Second, ///< Second time in the queue.
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RS_Global, ///< Produced by global splitting.
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RS_Local, ///< Produced by local splitting.
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RS_Spill ///< Produced by spilling.
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};
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IndexedMap<unsigned char, VirtReg2IndexFunctor> LRStage;
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LiveRangeStage getStage(const LiveInterval &VirtReg) const {
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return LiveRangeStage(LRStage[VirtReg.reg]);
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}
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template<typename Iterator>
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void setStage(Iterator Begin, Iterator End, LiveRangeStage NewStage) {
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LRStage.resize(MRI->getNumVirtRegs());
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for (;Begin != End; ++Begin) {
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unsigned Reg = (*Begin)->reg;
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if (LRStage[Reg] == RS_New)
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LRStage[Reg] = NewStage;
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}
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}
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// splitting state.
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std::auto_ptr<SplitAnalysis> SA;
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std::auto_ptr<SplitEditor> SE;
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/// Cached per-block interference maps
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InterferenceCache IntfCache;
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/// All basic blocks where the current register has uses.
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SmallVector<SpillPlacement::BlockConstraint, 8> SplitConstraints;
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/// Global live range splitting candidate info.
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struct GlobalSplitCandidate {
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unsigned PhysReg;
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BitVector LiveBundles;
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SmallVector<unsigned, 8> ActiveBlocks;
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void reset(unsigned Reg) {
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PhysReg = Reg;
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LiveBundles.clear();
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ActiveBlocks.clear();
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}
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};
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/// Candidate info for for each PhysReg in AllocationOrder.
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/// This vector never shrinks, but grows to the size of the largest register
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/// class.
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SmallVector<GlobalSplitCandidate, 32> GlobalCand;
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/// For every instruction in SA->UseSlots, store the previous non-copy
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/// instruction.
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SmallVector<SlotIndex, 8> PrevSlot;
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public:
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RAGreedy();
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/// Return the pass name.
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virtual const char* getPassName() const {
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return "Greedy Register Allocator";
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}
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/// RAGreedy analysis usage.
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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virtual void releaseMemory();
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virtual Spiller &spiller() { return *SpillerInstance; }
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virtual void enqueue(LiveInterval *LI);
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virtual LiveInterval *dequeue();
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virtual unsigned selectOrSplit(LiveInterval&,
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SmallVectorImpl<LiveInterval*>&);
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/// Perform register allocation.
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virtual bool runOnMachineFunction(MachineFunction &mf);
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static char ID;
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private:
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void LRE_WillEraseInstruction(MachineInstr*);
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bool LRE_CanEraseVirtReg(unsigned);
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void LRE_WillShrinkVirtReg(unsigned);
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void LRE_DidCloneVirtReg(unsigned, unsigned);
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float calcSpillCost();
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bool addSplitConstraints(InterferenceCache::Cursor, float&);
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void addThroughConstraints(InterferenceCache::Cursor, ArrayRef<unsigned>);
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void growRegion(GlobalSplitCandidate &Cand, InterferenceCache::Cursor);
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float calcGlobalSplitCost(GlobalSplitCandidate&, InterferenceCache::Cursor);
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void splitAroundRegion(LiveInterval&, GlobalSplitCandidate&,
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SmallVectorImpl<LiveInterval*>&);
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void calcGapWeights(unsigned, SmallVectorImpl<float>&);
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SlotIndex getPrevMappedIndex(const MachineInstr*);
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void calcPrevSlots();
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unsigned nextSplitPoint(unsigned);
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bool canEvictInterference(LiveInterval&, unsigned, float&);
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unsigned tryAssign(LiveInterval&, AllocationOrder&,
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SmallVectorImpl<LiveInterval*>&);
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unsigned tryEvict(LiveInterval&, AllocationOrder&,
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SmallVectorImpl<LiveInterval*>&, unsigned = ~0u);
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unsigned tryRegionSplit(LiveInterval&, AllocationOrder&,
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SmallVectorImpl<LiveInterval*>&);
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unsigned tryLocalSplit(LiveInterval&, AllocationOrder&,
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SmallVectorImpl<LiveInterval*>&);
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unsigned trySplit(LiveInterval&, AllocationOrder&,
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SmallVectorImpl<LiveInterval*>&);
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};
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} // end anonymous namespace
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char RAGreedy::ID = 0;
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// Hysteresis to use when comparing floats.
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// This helps stabilize decisions based on float comparisons.
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const float Hysteresis = 0.98f;
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FunctionPass* llvm::createGreedyRegisterAllocator() {
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return new RAGreedy();
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}
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RAGreedy::RAGreedy(): MachineFunctionPass(ID), LRStage(RS_New) {
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initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
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initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
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initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
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initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
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initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
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initializeRegisterCoalescerAnalysisGroup(*PassRegistry::getPassRegistry());
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initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
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initializeLiveStacksPass(*PassRegistry::getPassRegistry());
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initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry());
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initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
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initializeMachineLoopRangesPass(*PassRegistry::getPassRegistry());
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initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
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initializeEdgeBundlesPass(*PassRegistry::getPassRegistry());
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initializeSpillPlacementPass(*PassRegistry::getPassRegistry());
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}
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void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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AU.addRequired<AliasAnalysis>();
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AU.addPreserved<AliasAnalysis>();
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AU.addRequired<LiveIntervals>();
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AU.addRequired<SlotIndexes>();
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AU.addPreserved<SlotIndexes>();
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AU.addRequired<LiveDebugVariables>();
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AU.addPreserved<LiveDebugVariables>();
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if (StrongPHIElim)
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AU.addRequiredID(StrongPHIEliminationID);
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AU.addRequiredTransitive<RegisterCoalescer>();
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AU.addRequired<CalculateSpillWeights>();
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AU.addRequired<LiveStacks>();
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AU.addPreserved<LiveStacks>();
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AU.addRequired<MachineDominatorTree>();
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AU.addPreserved<MachineDominatorTree>();
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AU.addRequired<MachineLoopInfo>();
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AU.addPreserved<MachineLoopInfo>();
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AU.addRequired<MachineLoopRanges>();
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AU.addPreserved<MachineLoopRanges>();
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AU.addRequired<VirtRegMap>();
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AU.addPreserved<VirtRegMap>();
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AU.addRequired<EdgeBundles>();
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AU.addRequired<SpillPlacement>();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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//===----------------------------------------------------------------------===//
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// LiveRangeEdit delegate methods
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//===----------------------------------------------------------------------===//
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void RAGreedy::LRE_WillEraseInstruction(MachineInstr *MI) {
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// LRE itself will remove from SlotIndexes and parent basic block.
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VRM->RemoveMachineInstrFromMaps(MI);
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}
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bool RAGreedy::LRE_CanEraseVirtReg(unsigned VirtReg) {
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if (unsigned PhysReg = VRM->getPhys(VirtReg)) {
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unassign(LIS->getInterval(VirtReg), PhysReg);
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return true;
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}
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// Unassigned virtreg is probably in the priority queue.
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// RegAllocBase will erase it after dequeueing.
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return false;
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}
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void RAGreedy::LRE_WillShrinkVirtReg(unsigned VirtReg) {
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unsigned PhysReg = VRM->getPhys(VirtReg);
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if (!PhysReg)
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return;
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// Register is assigned, put it back on the queue for reassignment.
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LiveInterval &LI = LIS->getInterval(VirtReg);
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unassign(LI, PhysReg);
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enqueue(&LI);
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}
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void RAGreedy::LRE_DidCloneVirtReg(unsigned New, unsigned Old) {
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// LRE may clone a virtual register because dead code elimination causes it to
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// be split into connected components. Ensure that the new register gets the
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// same stage as the parent.
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LRStage.grow(New);
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LRStage[New] = LRStage[Old];
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}
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void RAGreedy::releaseMemory() {
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SpillerInstance.reset(0);
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LRStage.clear();
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GlobalCand.clear();
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RegAllocBase::releaseMemory();
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}
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void RAGreedy::enqueue(LiveInterval *LI) {
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// Prioritize live ranges by size, assigning larger ranges first.
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// The queue holds (size, reg) pairs.
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const unsigned Size = LI->getSize();
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const unsigned Reg = LI->reg;
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assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
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"Can only enqueue virtual registers");
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unsigned Prio;
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LRStage.grow(Reg);
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if (LRStage[Reg] == RS_New)
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LRStage[Reg] = RS_First;
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if (LRStage[Reg] == RS_Second)
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// Unsplit ranges that couldn't be allocated immediately are deferred until
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// everything else has been allocated. Long ranges are allocated last so
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// they are split against realistic interference.
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Prio = (1u << 31) - Size;
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else {
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// Everything else is allocated in long->short order. Long ranges that don't
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// fit should be spilled ASAP so they don't create interference.
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Prio = (1u << 31) + Size;
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// Boost ranges that have a physical register hint.
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if (TargetRegisterInfo::isPhysicalRegister(VRM->getRegAllocPref(Reg)))
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Prio |= (1u << 30);
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}
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Queue.push(std::make_pair(Prio, Reg));
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}
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LiveInterval *RAGreedy::dequeue() {
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if (Queue.empty())
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return 0;
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LiveInterval *LI = &LIS->getInterval(Queue.top().second);
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Queue.pop();
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return LI;
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}
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//===----------------------------------------------------------------------===//
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// Direct Assignment
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//===----------------------------------------------------------------------===//
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/// tryAssign - Try to assign VirtReg to an available register.
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unsigned RAGreedy::tryAssign(LiveInterval &VirtReg,
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AllocationOrder &Order,
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SmallVectorImpl<LiveInterval*> &NewVRegs) {
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Order.rewind();
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unsigned PhysReg;
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while ((PhysReg = Order.next()))
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if (!checkPhysRegInterference(VirtReg, PhysReg))
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break;
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if (!PhysReg || Order.isHint(PhysReg))
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return PhysReg;
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// PhysReg is available. Try to evict interference from a cheaper alternative.
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unsigned Cost = TRI->getCostPerUse(PhysReg);
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// Most registers have 0 additional cost.
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if (!Cost)
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return PhysReg;
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DEBUG(dbgs() << PrintReg(PhysReg, TRI) << " is available at cost " << Cost
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<< '\n');
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unsigned CheapReg = tryEvict(VirtReg, Order, NewVRegs, Cost);
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return CheapReg ? CheapReg : PhysReg;
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}
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//===----------------------------------------------------------------------===//
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// Interference eviction
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//===----------------------------------------------------------------------===//
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/// canEvict - Return true if all interferences between VirtReg and PhysReg can
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/// be evicted.
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/// Return false if any interference is heavier than MaxWeight.
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/// On return, set MaxWeight to the maximal spill weight of an interference.
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bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg,
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float &MaxWeight) {
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float Weight = 0;
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for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
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LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
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// If there is 10 or more interferences, chances are one is heavier.
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if (Q.collectInterferingVRegs(10, MaxWeight) >= 10)
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return false;
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// Check if any interfering live range is heavier than MaxWeight.
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for (unsigned i = Q.interferingVRegs().size(); i; --i) {
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LiveInterval *Intf = Q.interferingVRegs()[i - 1];
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if (TargetRegisterInfo::isPhysicalRegister(Intf->reg))
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return false;
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if (Intf->weight >= MaxWeight)
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return false;
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Weight = std::max(Weight, Intf->weight);
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}
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}
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MaxWeight = Weight;
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return true;
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}
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/// tryEvict - Try to evict all interferences for a physreg.
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/// @param VirtReg Currently unassigned virtual register.
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/// @param Order Physregs to try.
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/// @return Physreg to assign VirtReg, or 0.
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unsigned RAGreedy::tryEvict(LiveInterval &VirtReg,
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AllocationOrder &Order,
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SmallVectorImpl<LiveInterval*> &NewVRegs,
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unsigned CostPerUseLimit) {
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NamedRegionTimer T("Evict", TimerGroupName, TimePassesIsEnabled);
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// Keep track of the lightest single interference seen so far.
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float BestWeight = VirtReg.weight;
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unsigned BestPhys = 0;
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Order.rewind();
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while (unsigned PhysReg = Order.next()) {
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if (TRI->getCostPerUse(PhysReg) >= CostPerUseLimit)
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continue;
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// The first use of a register in a function has cost 1.
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if (CostPerUseLimit == 1 && !MRI->isPhysRegUsed(PhysReg))
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continue;
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float Weight = BestWeight;
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if (!canEvictInterference(VirtReg, PhysReg, Weight))
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continue;
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// This is an eviction candidate.
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DEBUG(dbgs() << PrintReg(PhysReg, TRI) << " interference = "
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<< Weight << '\n');
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if (BestPhys && Weight >= BestWeight)
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continue;
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// Best so far.
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BestPhys = PhysReg;
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BestWeight = Weight;
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// Stop if the hint can be used.
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if (Order.isHint(PhysReg))
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break;
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}
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if (!BestPhys)
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return 0;
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DEBUG(dbgs() << "evicting " << PrintReg(BestPhys, TRI) << " interference\n");
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for (const unsigned *AliasI = TRI->getOverlaps(BestPhys); *AliasI; ++AliasI) {
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LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
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assert(Q.seenAllInterferences() && "Didn't check all interfererences.");
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for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
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LiveInterval *Intf = Q.interferingVRegs()[i];
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unassign(*Intf, VRM->getPhys(Intf->reg));
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++NumEvicted;
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NewVRegs.push_back(Intf);
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}
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}
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return BestPhys;
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}
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//===----------------------------------------------------------------------===//
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// Region Splitting
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//===----------------------------------------------------------------------===//
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/// addSplitConstraints - Fill out the SplitConstraints vector based on the
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/// interference pattern in Physreg and its aliases. Add the constraints to
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/// SpillPlacement and return the static cost of this split in Cost, assuming
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/// that all preferences in SplitConstraints are met.
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/// Return false if there are no bundles with positive bias.
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bool RAGreedy::addSplitConstraints(InterferenceCache::Cursor Intf,
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float &Cost) {
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ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
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// Reset interference dependent info.
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SplitConstraints.resize(UseBlocks.size());
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float StaticCost = 0;
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for (unsigned i = 0; i != UseBlocks.size(); ++i) {
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const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
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SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
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BC.Number = BI.MBB->getNumber();
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Intf.moveToBlock(BC.Number);
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BC.Entry = BI.LiveIn ? SpillPlacement::PrefReg : SpillPlacement::DontCare;
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BC.Exit = BI.LiveOut ? SpillPlacement::PrefReg : SpillPlacement::DontCare;
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if (!Intf.hasInterference())
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continue;
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// Number of spill code instructions to insert.
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unsigned Ins = 0;
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// Interference for the live-in value.
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if (BI.LiveIn) {
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if (Intf.first() <= Indexes->getMBBStartIdx(BC.Number))
|
|
BC.Entry = SpillPlacement::MustSpill, ++Ins;
|
|
else if (Intf.first() < BI.FirstUse)
|
|
BC.Entry = SpillPlacement::PrefSpill, ++Ins;
|
|
else if (Intf.first() < (BI.LiveThrough ? BI.LastUse : BI.Kill))
|
|
++Ins;
|
|
}
|
|
|
|
// 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.LastUse)
|
|
BC.Exit = SpillPlacement::PrefSpill, ++Ins;
|
|
else if (Intf.last() > (BI.LiveThrough ? BI.FirstUse : BI.Def))
|
|
++Ins;
|
|
}
|
|
|
|
// Accumulate the total frequency of inserted spill code.
|
|
if (Ins)
|
|
StaticCost += Ins * 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.
|
|
void 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(ArrayRef<unsigned>(TBS, T));
|
|
T = 0;
|
|
}
|
|
continue;
|
|
}
|
|
|
|
assert(B < GroupSize && "Array overflow");
|
|
BCS[B].Number = Number;
|
|
|
|
// 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) {
|
|
ArrayRef<SpillPlacement::BlockConstraint> Array(BCS, B);
|
|
SpillPlacer->addConstraints(Array);
|
|
B = 0;
|
|
}
|
|
}
|
|
|
|
ArrayRef<SpillPlacement::BlockConstraint> Array(BCS, B);
|
|
SpillPlacer->addConstraints(Array);
|
|
SpillPlacer->addLinks(ArrayRef<unsigned>(TBS, T));
|
|
}
|
|
|
|
void RAGreedy::growRegion(GlobalSplitCandidate &Cand,
|
|
InterferenceCache::Cursor Intf) {
|
|
// 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
|
|
|
|
for (;;) {
|
|
ArrayRef<unsigned> NewBundles = SpillPlacer->getRecentPositive();
|
|
if (NewBundles.empty())
|
|
break;
|
|
// 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) {
|
|
ArrayRef<unsigned> Add(&ActiveBlocks[AddedTo],
|
|
ActiveBlocks.size() - AddedTo);
|
|
addThroughConstraints(Intf, Add);
|
|
AddedTo = ActiveBlocks.size();
|
|
}
|
|
// Perhaps iterating can enable more bundles?
|
|
SpillPlacer->iterate();
|
|
}
|
|
DEBUG(dbgs() << ", v=" << Visited);
|
|
}
|
|
|
|
/// calcSpillCost - Compute how expensive it would be to split the live range in
|
|
/// SA around all use blocks instead of forming bundle regions.
|
|
float RAGreedy::calcSpillCost() {
|
|
float Cost = 0;
|
|
const LiveInterval &LI = SA->getParent();
|
|
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) {
|
|
SlotIndex Start, Stop;
|
|
tie(Start, Stop) = Indexes->getMBBRange(Number);
|
|
LiveInterval::const_iterator I = LI.find(Start);
|
|
assert(I != LI.end() && "Expected live-in value");
|
|
// Is there a different live-out value? If so, we need an extra spill
|
|
// instruction.
|
|
if (I->end < Stop)
|
|
Cost += SpillPlacer->getBlockFrequency(Number);
|
|
}
|
|
}
|
|
return Cost;
|
|
}
|
|
|
|
/// 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.
|
|
///
|
|
float RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand,
|
|
InterferenceCache::Cursor Intf) {
|
|
float GlobalCost = 0;
|
|
const BitVector &LiveBundles = Cand.LiveBundles;
|
|
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, 0)];
|
|
bool RegOut = LiveBundles[Bundles->getBundle(BC.Number, 1)];
|
|
unsigned Ins = 0;
|
|
|
|
if (BI.LiveIn)
|
|
Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg);
|
|
if (BI.LiveOut)
|
|
Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg);
|
|
if (Ins)
|
|
GlobalCost += Ins * 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, 0)];
|
|
bool RegOut = LiveBundles[Bundles->getBundle(Number, 1)];
|
|
if (!RegIn && !RegOut)
|
|
continue;
|
|
if (RegIn && RegOut) {
|
|
// We need double spill code if this block has interference.
|
|
Intf.moveToBlock(Number);
|
|
if (Intf.hasInterference())
|
|
GlobalCost += 2*SpillPlacer->getBlockFrequency(Number);
|
|
continue;
|
|
}
|
|
// live-in / stack-out or stack-in live-out.
|
|
GlobalCost += SpillPlacer->getBlockFrequency(Number);
|
|
}
|
|
return GlobalCost;
|
|
}
|
|
|
|
/// splitAroundRegion - Split VirtReg around the region determined by
|
|
/// LiveBundles. Make an effort to avoid interference from PhysReg.
|
|
///
|
|
/// The 'register' interval is going to contain as many uses as possible while
|
|
/// avoiding interference. The 'stack' interval is the complement constructed by
|
|
/// SplitEditor. It will contain the rest.
|
|
///
|
|
void RAGreedy::splitAroundRegion(LiveInterval &VirtReg,
|
|
GlobalSplitCandidate &Cand,
|
|
SmallVectorImpl<LiveInterval*> &NewVRegs) {
|
|
const BitVector &LiveBundles = Cand.LiveBundles;
|
|
|
|
DEBUG({
|
|
dbgs() << "Splitting around region for " << PrintReg(Cand.PhysReg, TRI)
|
|
<< " with bundles";
|
|
for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
|
|
dbgs() << " EB#" << i;
|
|
dbgs() << ".\n";
|
|
});
|
|
|
|
InterferenceCache::Cursor Intf(IntfCache, Cand.PhysReg);
|
|
LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
|
|
SE->reset(LREdit);
|
|
|
|
// Create the main cross-block interval.
|
|
const unsigned MainIntv = SE->openIntv();
|
|
|
|
// First add all defs that are live out of a block.
|
|
ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
|
|
for (unsigned i = 0; i != UseBlocks.size(); ++i) {
|
|
const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
|
|
bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
|
|
bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
|
|
|
|
// Create separate intervals for isolated blocks with multiple uses.
|
|
if (!RegIn && !RegOut && BI.FirstUse != BI.LastUse) {
|
|
DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " isolated.\n");
|
|
SE->splitSingleBlock(BI);
|
|
SE->selectIntv(MainIntv);
|
|
continue;
|
|
}
|
|
|
|
// Should the register be live out?
|
|
if (!BI.LiveOut || !RegOut)
|
|
continue;
|
|
|
|
SlotIndex Start, Stop;
|
|
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
|
|
Intf.moveToBlock(BI.MBB->getNumber());
|
|
DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " -> EB#"
|
|
<< Bundles->getBundle(BI.MBB->getNumber(), 1)
|
|
<< " [" << Start << ';'
|
|
<< SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
|
|
<< ") intf [" << Intf.first() << ';' << Intf.last() << ')');
|
|
|
|
// The interference interval should either be invalid or overlap MBB.
|
|
assert((!Intf.hasInterference() || Intf.first() < Stop)
|
|
&& "Bad interference");
|
|
assert((!Intf.hasInterference() || Intf.last() > Start)
|
|
&& "Bad interference");
|
|
|
|
// Check interference leaving the block.
|
|
if (!Intf.hasInterference()) {
|
|
// Block is interference-free.
|
|
DEBUG(dbgs() << ", no interference");
|
|
if (!BI.LiveThrough) {
|
|
DEBUG(dbgs() << ", not live-through.\n");
|
|
SE->useIntv(SE->enterIntvBefore(BI.Def), Stop);
|
|
continue;
|
|
}
|
|
if (!RegIn) {
|
|
// Block is live-through, but entry bundle is on the stack.
|
|
// Reload just before the first use.
|
|
DEBUG(dbgs() << ", not live-in, enter before first use.\n");
|
|
SE->useIntv(SE->enterIntvBefore(BI.FirstUse), Stop);
|
|
continue;
|
|
}
|
|
DEBUG(dbgs() << ", live-through.\n");
|
|
continue;
|
|
}
|
|
|
|
// Block has interference.
|
|
DEBUG(dbgs() << ", interference to " << Intf.last());
|
|
|
|
if (!BI.LiveThrough && Intf.last() <= BI.Def) {
|
|
// The interference doesn't reach the outgoing segment.
|
|
DEBUG(dbgs() << " doesn't affect def from " << BI.Def << '\n');
|
|
SE->useIntv(BI.Def, Stop);
|
|
continue;
|
|
}
|
|
|
|
SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
|
|
if (Intf.last().getBoundaryIndex() < BI.LastUse) {
|
|
// There are interference-free uses at the end of the block.
|
|
// Find the first use that can get the live-out register.
|
|
SmallVectorImpl<SlotIndex>::const_iterator UI =
|
|
std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
|
|
Intf.last().getBoundaryIndex());
|
|
assert(UI != SA->UseSlots.end() && "Couldn't find last use");
|
|
SlotIndex Use = *UI;
|
|
assert(Use <= BI.LastUse && "Couldn't find last use");
|
|
// Only attempt a split befroe the last split point.
|
|
if (Use.getBaseIndex() <= LastSplitPoint) {
|
|
DEBUG(dbgs() << ", free use at " << Use << ".\n");
|
|
SlotIndex SegStart = SE->enterIntvBefore(Use);
|
|
assert(SegStart >= Intf.last() && "Couldn't avoid interference");
|
|
assert(SegStart < LastSplitPoint && "Impossible split point");
|
|
SE->useIntv(SegStart, Stop);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// Interference is after the last use.
|
|
DEBUG(dbgs() << " after last use.\n");
|
|
SlotIndex SegStart = SE->enterIntvAtEnd(*BI.MBB);
|
|
assert(SegStart >= Intf.last() && "Couldn't avoid interference");
|
|
}
|
|
|
|
// Now all defs leading to live bundles are handled, do everything else.
|
|
for (unsigned i = 0; i != UseBlocks.size(); ++i) {
|
|
const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
|
|
bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
|
|
bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
|
|
|
|
// Is the register live-in?
|
|
if (!BI.LiveIn || !RegIn)
|
|
continue;
|
|
|
|
// We have an incoming register. Check for interference.
|
|
SlotIndex Start, Stop;
|
|
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
|
|
Intf.moveToBlock(BI.MBB->getNumber());
|
|
DEBUG(dbgs() << "EB#" << Bundles->getBundle(BI.MBB->getNumber(), 0)
|
|
<< " -> BB#" << BI.MBB->getNumber() << " [" << Start << ';'
|
|
<< SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
|
|
<< ')');
|
|
|
|
// Check interference entering the block.
|
|
if (!Intf.hasInterference()) {
|
|
// Block is interference-free.
|
|
DEBUG(dbgs() << ", no interference");
|
|
if (!BI.LiveThrough) {
|
|
DEBUG(dbgs() << ", killed in block.\n");
|
|
SE->useIntv(Start, SE->leaveIntvAfter(BI.Kill));
|
|
continue;
|
|
}
|
|
if (!RegOut) {
|
|
SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
|
|
// Block is live-through, but exit bundle is on the stack.
|
|
// Spill immediately after the last use.
|
|
if (BI.LastUse < LastSplitPoint) {
|
|
DEBUG(dbgs() << ", uses, stack-out.\n");
|
|
SE->useIntv(Start, SE->leaveIntvAfter(BI.LastUse));
|
|
continue;
|
|
}
|
|
// The last use is after the last split point, it is probably an
|
|
// indirect jump.
|
|
DEBUG(dbgs() << ", uses at " << BI.LastUse << " after split point "
|
|
<< LastSplitPoint << ", stack-out.\n");
|
|
SlotIndex SegEnd = SE->leaveIntvBefore(LastSplitPoint);
|
|
SE->useIntv(Start, SegEnd);
|
|
// Run a double interval from the split to the last use.
|
|
// This makes it possible to spill the complement without affecting the
|
|
// indirect branch.
|
|
SE->overlapIntv(SegEnd, BI.LastUse);
|
|
continue;
|
|
}
|
|
// Register is live-through.
|
|
DEBUG(dbgs() << ", uses, live-through.\n");
|
|
SE->useIntv(Start, Stop);
|
|
continue;
|
|
}
|
|
|
|
// Block has interference.
|
|
DEBUG(dbgs() << ", interference from " << Intf.first());
|
|
|
|
if (!BI.LiveThrough && Intf.first() >= BI.Kill) {
|
|
// The interference doesn't reach the outgoing segment.
|
|
DEBUG(dbgs() << " doesn't affect kill at " << BI.Kill << '\n');
|
|
SE->useIntv(Start, BI.Kill);
|
|
continue;
|
|
}
|
|
|
|
if (Intf.first().getBaseIndex() > BI.FirstUse) {
|
|
// There are interference-free uses at the beginning of the block.
|
|
// Find the last use that can get the register.
|
|
SmallVectorImpl<SlotIndex>::const_iterator UI =
|
|
std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
|
|
Intf.first().getBaseIndex());
|
|
assert(UI != SA->UseSlots.begin() && "Couldn't find first use");
|
|
SlotIndex Use = (--UI)->getBoundaryIndex();
|
|
DEBUG(dbgs() << ", free use at " << *UI << ".\n");
|
|
SlotIndex SegEnd = SE->leaveIntvAfter(Use);
|
|
assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
|
|
SE->useIntv(Start, SegEnd);
|
|
continue;
|
|
}
|
|
|
|
// Interference is before the first use.
|
|
DEBUG(dbgs() << " before first use.\n");
|
|
SlotIndex SegEnd = SE->leaveIntvAtTop(*BI.MBB);
|
|
assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
|
|
}
|
|
|
|
// Handle live-through blocks.
|
|
for (unsigned i = 0, e = Cand.ActiveBlocks.size(); i != e; ++i) {
|
|
unsigned Number = Cand.ActiveBlocks[i];
|
|
bool RegIn = LiveBundles[Bundles->getBundle(Number, 0)];
|
|
bool RegOut = LiveBundles[Bundles->getBundle(Number, 1)];
|
|
DEBUG(dbgs() << "Live through BB#" << Number << '\n');
|
|
if (RegIn && RegOut) {
|
|
Intf.moveToBlock(Number);
|
|
if (!Intf.hasInterference()) {
|
|
SE->useIntv(Indexes->getMBBStartIdx(Number),
|
|
Indexes->getMBBEndIdx(Number));
|
|
continue;
|
|
}
|
|
}
|
|
MachineBasicBlock *MBB = MF->getBlockNumbered(Number);
|
|
if (RegIn)
|
|
SE->leaveIntvAtTop(*MBB);
|
|
if (RegOut)
|
|
SE->enterIntvAtEnd(*MBB);
|
|
}
|
|
|
|
++NumGlobalSplits;
|
|
|
|
SmallVector<unsigned, 8> IntvMap;
|
|
SE->finish(&IntvMap);
|
|
LRStage.resize(MRI->getNumVirtRegs());
|
|
unsigned OrigBlocks = SA->getNumThroughBlocks() + SA->getUseBlocks().size();
|
|
|
|
// 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) {
|
|
unsigned Reg = LREdit.get(i)->reg;
|
|
|
|
// Ignore old intervals from DCE.
|
|
if (LRStage[Reg] != RS_New)
|
|
continue;
|
|
|
|
// Remainder interval. Don't try splitting again, spill if it doesn't
|
|
// allocate.
|
|
if (IntvMap[i] == 0) {
|
|
LRStage[Reg] = RS_Global;
|
|
continue;
|
|
}
|
|
|
|
// Main interval. Allow repeated splitting as long as the number of live
|
|
// blocks is strictly decreasing.
|
|
if (IntvMap[i] == MainIntv) {
|
|
if (SA->countLiveBlocks(LREdit.get(i)) >= OrigBlocks) {
|
|
DEBUG(dbgs() << "Main interval covers the same " << OrigBlocks
|
|
<< " blocks as original.\n");
|
|
// Don't allow repeated splitting as a safe guard against looping.
|
|
LRStage[Reg] = RS_Global;
|
|
}
|
|
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");
|
|
}
|
|
|
|
unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
|
|
SmallVectorImpl<LiveInterval*> &NewVRegs) {
|
|
float BestCost = Hysteresis * calcSpillCost();
|
|
DEBUG(dbgs() << "Cost of isolating all blocks = " << BestCost << '\n');
|
|
const unsigned NoCand = ~0u;
|
|
unsigned BestCand = NoCand;
|
|
|
|
Order.rewind();
|
|
for (unsigned Cand = 0; unsigned PhysReg = Order.next(); ++Cand) {
|
|
if (GlobalCand.size() <= Cand)
|
|
GlobalCand.resize(Cand+1);
|
|
GlobalCand[Cand].reset(PhysReg);
|
|
|
|
SpillPlacer->prepare(GlobalCand[Cand].LiveBundles);
|
|
float Cost;
|
|
InterferenceCache::Cursor Intf(IntfCache, PhysReg);
|
|
if (!addSplitConstraints(Intf, Cost)) {
|
|
DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tno positive bundles\n");
|
|
continue;
|
|
}
|
|
DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tstatic = " << Cost);
|
|
if (Cost >= BestCost) {
|
|
DEBUG({
|
|
if (BestCand == NoCand)
|
|
dbgs() << " worse than no bundles\n";
|
|
else
|
|
dbgs() << " worse than "
|
|
<< PrintReg(GlobalCand[BestCand].PhysReg, TRI) << '\n';
|
|
});
|
|
continue;
|
|
}
|
|
growRegion(GlobalCand[Cand], Intf);
|
|
|
|
SpillPlacer->finish();
|
|
|
|
// No live bundles, defer to splitSingleBlocks().
|
|
if (!GlobalCand[Cand].LiveBundles.any()) {
|
|
DEBUG(dbgs() << " no bundles.\n");
|
|
continue;
|
|
}
|
|
|
|
Cost += calcGlobalSplitCost(GlobalCand[Cand], Intf);
|
|
DEBUG({
|
|
dbgs() << ", total = " << Cost << " with bundles";
|
|
for (int i = GlobalCand[Cand].LiveBundles.find_first(); i>=0;
|
|
i = GlobalCand[Cand].LiveBundles.find_next(i))
|
|
dbgs() << " EB#" << i;
|
|
dbgs() << ".\n";
|
|
});
|
|
if (Cost < BestCost) {
|
|
BestCand = Cand;
|
|
BestCost = Hysteresis * Cost; // Prevent rounding effects.
|
|
}
|
|
}
|
|
|
|
if (BestCand == NoCand)
|
|
return 0;
|
|
|
|
splitAroundRegion(VirtReg, GlobalCand[BestCand], NewVRegs);
|
|
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();
|
|
const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
|
|
const unsigned NumGaps = Uses.size()-1;
|
|
|
|
// Start and end points for the interference check.
|
|
SlotIndex StartIdx = BI.LiveIn ? BI.FirstUse.getBaseIndex() : BI.FirstUse;
|
|
SlotIndex StopIdx = BI.LiveOut ? BI.LastUse.getBoundaryIndex() : BI.LastUse;
|
|
|
|
GapWeight.assign(NumGaps, 0.0f);
|
|
|
|
// Add interference from each overlapping register.
|
|
for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
|
|
if (!query(const_cast<LiveInterval&>(SA->getParent()), *AI)
|
|
.checkInterference())
|
|
continue;
|
|
|
|
// We know that VirtReg is a continuous interval from FirstUse to LastUse,
|
|
// 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 = PhysReg2LiveUnion[*AI].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;
|
|
}
|
|
}
|
|
}
|
|
|
|
/// getPrevMappedIndex - Return the slot index of the last non-copy instruction
|
|
/// before MI that has a slot index. If MI is the first mapped instruction in
|
|
/// its block, return the block start index instead.
|
|
///
|
|
SlotIndex RAGreedy::getPrevMappedIndex(const MachineInstr *MI) {
|
|
assert(MI && "Missing MachineInstr");
|
|
const MachineBasicBlock *MBB = MI->getParent();
|
|
MachineBasicBlock::const_iterator B = MBB->begin(), I = MI;
|
|
while (I != B)
|
|
if (!(--I)->isDebugValue() && !I->isCopy())
|
|
return Indexes->getInstructionIndex(I);
|
|
return Indexes->getMBBStartIdx(MBB);
|
|
}
|
|
|
|
/// calcPrevSlots - Fill in the PrevSlot array with the index of the previous
|
|
/// real non-copy instruction for each instruction in SA->UseSlots.
|
|
///
|
|
void RAGreedy::calcPrevSlots() {
|
|
const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
|
|
PrevSlot.clear();
|
|
PrevSlot.reserve(Uses.size());
|
|
for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
|
|
const MachineInstr *MI = Indexes->getInstructionFromIndex(Uses[i]);
|
|
PrevSlot.push_back(getPrevMappedIndex(MI).getDefIndex());
|
|
}
|
|
}
|
|
|
|
/// nextSplitPoint - Find the next index into SA->UseSlots > i such that it may
|
|
/// be beneficial to split before UseSlots[i].
|
|
///
|
|
/// 0 is always a valid split point
|
|
unsigned RAGreedy::nextSplitPoint(unsigned i) {
|
|
const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
|
|
const unsigned Size = Uses.size();
|
|
assert(i != Size && "No split points after the end");
|
|
// Allow split before i when Uses[i] is not adjacent to the previous use.
|
|
while (++i != Size && PrevSlot[i].getBaseIndex() <= Uses[i-1].getBaseIndex())
|
|
;
|
|
return i;
|
|
}
|
|
|
|
/// tryLocalSplit - Try to split VirtReg into smaller intervals inside its only
|
|
/// basic block.
|
|
///
|
|
unsigned RAGreedy::tryLocalSplit(LiveInterval &VirtReg, AllocationOrder &Order,
|
|
SmallVectorImpl<LiveInterval*> &NewVRegs) {
|
|
assert(SA->getUseBlocks().size() == 1 && "Not a local interval");
|
|
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 FirstUse to LastUse. We should make
|
|
// sure that we don't do anything illegal to such an interval, though.
|
|
|
|
const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
|
|
if (Uses.size() <= 2)
|
|
return 0;
|
|
const unsigned NumGaps = Uses.size()-1;
|
|
|
|
DEBUG({
|
|
dbgs() << "tryLocalSplit: ";
|
|
for (unsigned i = 0, e = Uses.size(); i != e; ++i)
|
|
dbgs() << ' ' << SA->UseSlots[i];
|
|
dbgs() << '\n';
|
|
});
|
|
|
|
// For every use, find the previous mapped non-copy instruction.
|
|
// We use this to detect valid split points, and to estimate new interval
|
|
// sizes.
|
|
calcPrevSlots();
|
|
|
|
unsigned BestBefore = NumGaps;
|
|
unsigned BestAfter = 0;
|
|
float BestDiff = 0;
|
|
|
|
const float blockFreq = SpillPlacer->getBlockFrequency(BI.MBB->getNumber());
|
|
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);
|
|
|
|
// 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 = nextSplitPoint(1) - 1;
|
|
|
|
// MaxGap should always be max(GapWeight[SplitBefore..SplitAfter-1]).
|
|
// It is the spill weight that needs to be evicted.
|
|
float MaxGap = GapWeight[0];
|
|
for (unsigned i = 1; i != SplitAfter; ++i)
|
|
MaxGap = std::max(MaxGap, GapWeight[i]);
|
|
|
|
for (;;) {
|
|
// Live before/after split?
|
|
const bool LiveBefore = SplitBefore != 0 || BI.LiveIn;
|
|
const bool LiveAfter = SplitAfter != NumGaps || BI.LiveOut;
|
|
|
|
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) {
|
|
DEBUG(dbgs() << " all\n");
|
|
break;
|
|
}
|
|
// Should the interval be extended or shrunk?
|
|
bool Shrink = true;
|
|
if (MaxGap < HUGE_VALF) {
|
|
// Estimate the new spill weight.
|
|
//
|
|
// Each instruction reads and writes the register, except the first
|
|
// instr doesn't read when !FirstLive, and the last instr doesn't write
|
|
// when !LastLive.
|
|
//
|
|
// We will be inserting copies before and after, so the total number of
|
|
// reads and writes is 2 * EstUses.
|
|
//
|
|
const unsigned EstUses = 2*(SplitAfter - SplitBefore) +
|
|
2*(LiveBefore + LiveAfter);
|
|
|
|
// Try to guess the size of the new interval. This should be trivial,
|
|
// but the slot index of an inserted copy can be a lot smaller than the
|
|
// instruction it is inserted before if there are many dead indexes
|
|
// between them.
|
|
//
|
|
// We measure the distance from the instruction before SplitBefore to
|
|
// get a conservative estimate.
|
|
//
|
|
// The final distance can still be different if inserting copies
|
|
// triggers a slot index renumbering.
|
|
//
|
|
const float EstWeight = normalizeSpillWeight(blockFreq * EstUses,
|
|
PrevSlot[SplitBefore].distance(Uses[SplitAfter]));
|
|
// Would this split be possible to allocate?
|
|
// Never allocate all gaps, we wouldn't be making progress.
|
|
DEBUG(dbgs() << " w=" << EstWeight);
|
|
if (EstWeight * Hysteresis >= MaxGap) {
|
|
Shrink = false;
|
|
float Diff = EstWeight - MaxGap;
|
|
if (Diff > BestDiff) {
|
|
DEBUG(dbgs() << " (best)");
|
|
BestDiff = Hysteresis * Diff;
|
|
BestBefore = SplitBefore;
|
|
BestAfter = SplitAfter;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Try to shrink.
|
|
if (Shrink) {
|
|
SplitBefore = nextSplitPoint(SplitBefore);
|
|
if (SplitBefore < SplitAfter) {
|
|
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) {
|
|
DEBUG(dbgs() << " end\n");
|
|
break;
|
|
}
|
|
|
|
DEBUG(dbgs() << " extend\n");
|
|
for (unsigned e = nextSplitPoint(SplitAfter + 1) - 1;
|
|
SplitAfter != e; ++SplitAfter)
|
|
MaxGap = std::max(MaxGap, GapWeight[SplitAfter]);
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// Didn't find any candidates?
|
|
if (BestBefore == NumGaps)
|
|
return 0;
|
|
|
|
DEBUG(dbgs() << "Best local split range: " << Uses[BestBefore]
|
|
<< '-' << Uses[BestAfter] << ", " << BestDiff
|
|
<< ", " << (BestAfter - BestBefore + 1) << " instrs\n");
|
|
|
|
LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
|
|
SE->reset(LREdit);
|
|
|
|
SE->openIntv();
|
|
SlotIndex SegStart = SE->enterIntvBefore(Uses[BestBefore]);
|
|
SlotIndex SegStop = SE->leaveIntvAfter(Uses[BestAfter]);
|
|
SE->useIntv(SegStart, SegStop);
|
|
SE->finish();
|
|
setStage(NewVRegs.begin(), NewVRegs.end(), RS_Local);
|
|
++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<LiveInterval*>&NewVRegs) {
|
|
// Local intervals are handled separately.
|
|
if (LIS->intervalIsInOneMBB(VirtReg)) {
|
|
NamedRegionTimer T("Local Splitting", TimerGroupName, TimePassesIsEnabled);
|
|
SA->analyze(&VirtReg);
|
|
return tryLocalSplit(VirtReg, Order, NewVRegs);
|
|
}
|
|
|
|
NamedRegionTimer T("Global Splitting", TimerGroupName, TimePassesIsEnabled);
|
|
|
|
// Don't iterate global splitting.
|
|
// Move straight to spilling if this range was produced by a global split.
|
|
if (getStage(VirtReg) >= RS_Global)
|
|
return 0;
|
|
|
|
SA->analyze(&VirtReg);
|
|
|
|
// First try to split around a region spanning multiple blocks.
|
|
unsigned PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs);
|
|
if (PhysReg || !NewVRegs.empty())
|
|
return PhysReg;
|
|
|
|
// Then isolate blocks with multiple uses.
|
|
SplitAnalysis::BlockPtrSet Blocks;
|
|
if (SA->getMultiUseBlocks(Blocks)) {
|
|
LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
|
|
SE->reset(LREdit);
|
|
SE->splitSingleBlocks(Blocks);
|
|
setStage(NewVRegs.begin(), NewVRegs.end(), RS_Global);
|
|
if (VerifyEnabled)
|
|
MF->verify(this, "After splitting live range around basic blocks");
|
|
}
|
|
|
|
// Don't assign any physregs.
|
|
return 0;
|
|
}
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Main Entry Point
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg,
|
|
SmallVectorImpl<LiveInterval*> &NewVRegs) {
|
|
// First try assigning a free register.
|
|
AllocationOrder Order(VirtReg.reg, *VRM, ReservedRegs);
|
|
if (unsigned PhysReg = tryAssign(VirtReg, Order, NewVRegs))
|
|
return PhysReg;
|
|
|
|
if (unsigned PhysReg = tryEvict(VirtReg, Order, NewVRegs))
|
|
return PhysReg;
|
|
|
|
assert(NewVRegs.empty() && "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.
|
|
LiveRangeStage Stage = getStage(VirtReg);
|
|
if (Stage == RS_First) {
|
|
LRStage[VirtReg.reg] = RS_Second;
|
|
DEBUG(dbgs() << "wait for second round\n");
|
|
NewVRegs.push_back(&VirtReg);
|
|
return 0;
|
|
}
|
|
|
|
assert(Stage < RS_Spill && "Cannot allocate after spilling");
|
|
|
|
// Try splitting VirtReg or interferences.
|
|
unsigned PhysReg = trySplit(VirtReg, Order, NewVRegs);
|
|
if (PhysReg || !NewVRegs.empty())
|
|
return PhysReg;
|
|
|
|
// Finally spill VirtReg itself.
|
|
NamedRegionTimer T("Spiller", TimerGroupName, TimePassesIsEnabled);
|
|
LiveRangeEdit LRE(VirtReg, NewVRegs, this);
|
|
spiller().spill(LRE);
|
|
setStage(NewVRegs.begin(), NewVRegs.end(), RS_Spill);
|
|
|
|
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;
|
|
}
|
|
|
|
bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
|
|
DEBUG(dbgs() << "********** GREEDY REGISTER ALLOCATION **********\n"
|
|
<< "********** Function: "
|
|
<< ((Value*)mf.getFunction())->getName() << '\n');
|
|
|
|
MF = &mf;
|
|
if (VerifyEnabled)
|
|
MF->verify(this, "Before greedy register allocator");
|
|
|
|
RegAllocBase::init(getAnalysis<VirtRegMap>(), getAnalysis<LiveIntervals>());
|
|
Indexes = &getAnalysis<SlotIndexes>();
|
|
DomTree = &getAnalysis<MachineDominatorTree>();
|
|
ReservedRegs = TRI->getReservedRegs(*MF);
|
|
SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM));
|
|
Loops = &getAnalysis<MachineLoopInfo>();
|
|
LoopRanges = &getAnalysis<MachineLoopRanges>();
|
|
Bundles = &getAnalysis<EdgeBundles>();
|
|
SpillPlacer = &getAnalysis<SpillPlacement>();
|
|
|
|
SA.reset(new SplitAnalysis(*VRM, *LIS, *Loops));
|
|
SE.reset(new SplitEditor(*SA, *LIS, *VRM, *DomTree));
|
|
LRStage.clear();
|
|
LRStage.resize(MRI->getNumVirtRegs());
|
|
IntfCache.init(MF, &PhysReg2LiveUnion[0], Indexes, TRI);
|
|
|
|
allocatePhysRegs();
|
|
addMBBLiveIns(MF);
|
|
LIS->addKillFlags();
|
|
|
|
// Run rewriter
|
|
{
|
|
NamedRegionTimer T("Rewriter", TimerGroupName, TimePassesIsEnabled);
|
|
VRM->rewrite(Indexes);
|
|
}
|
|
|
|
// Write out new DBG_VALUE instructions.
|
|
getAnalysis<LiveDebugVariables>().emitDebugValues(VRM);
|
|
|
|
// The pass output is in VirtRegMap. Release all the transient data.
|
|
releaseMemory();
|
|
|
|
return true;
|
|
}
|