| //===-------- SplitKit.h - Toolkit for splitting live ranges ----*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains the SplitAnalysis class as well as mutator functions for |
| // live range splitting. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CODEGEN_SPLITKIT_H |
| #define LLVM_CODEGEN_SPLITKIT_H |
| |
| #include "LiveRangeCalc.h" |
| #include "llvm/ADT/ArrayRef.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/IntervalMap.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| |
| namespace llvm { |
| |
| class ConnectedVNInfoEqClasses; |
| class LiveInterval; |
| class LiveIntervals; |
| class LiveRangeEdit; |
| class MachineInstr; |
| class MachineLoopInfo; |
| class MachineRegisterInfo; |
| class TargetInstrInfo; |
| class TargetRegisterInfo; |
| class VirtRegMap; |
| class VNInfo; |
| class raw_ostream; |
| |
| /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting |
| /// opportunities. |
| class SplitAnalysis { |
| public: |
| const MachineFunction &MF; |
| const VirtRegMap &VRM; |
| const LiveIntervals &LIS; |
| const MachineLoopInfo &Loops; |
| const TargetInstrInfo &TII; |
| |
| /// Additional information about basic blocks where the current variable is |
| /// live. Such a block will look like one of these templates: |
| /// |
| /// 1. | o---x | Internal to block. Variable is only live in this block. |
| /// 2. |---x | Live-in, kill. |
| /// 3. | o---| Def, live-out. |
| /// 4. |---x o---| Live-in, kill, def, live-out. Counted by NumGapBlocks. |
| /// 5. |---o---o---| Live-through with uses or defs. |
| /// 6. |-----------| Live-through without uses. Counted by NumThroughBlocks. |
| /// |
| /// Two BlockInfo entries are created for template 4. One for the live-in |
| /// segment, and one for the live-out segment. These entries look as if the |
| /// block were split in the middle where the live range isn't live. |
| /// |
| /// Live-through blocks without any uses don't get BlockInfo entries. They |
| /// are simply listed in ThroughBlocks instead. |
| /// |
| struct BlockInfo { |
| MachineBasicBlock *MBB; |
| SlotIndex FirstInstr; ///< First instr accessing current reg. |
| SlotIndex LastInstr; ///< Last instr accessing current reg. |
| SlotIndex FirstDef; ///< First non-phi valno->def, or SlotIndex(). |
| bool LiveIn; ///< Current reg is live in. |
| bool LiveOut; ///< Current reg is live out. |
| |
| /// isOneInstr - Returns true when this BlockInfo describes a single |
| /// instruction. |
| bool isOneInstr() const { |
| return SlotIndex::isSameInstr(FirstInstr, LastInstr); |
| } |
| }; |
| |
| private: |
| // Current live interval. |
| const LiveInterval *CurLI; |
| |
| // Sorted slot indexes of using instructions. |
| SmallVector<SlotIndex, 8> UseSlots; |
| |
| /// LastSplitPoint - Last legal split point in each basic block in the current |
| /// function. The first entry is the first terminator, the second entry is the |
| /// last valid split point for a variable that is live in to a landing pad |
| /// successor. |
| SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint; |
| |
| /// UseBlocks - Blocks where CurLI has uses. |
| SmallVector<BlockInfo, 8> UseBlocks; |
| |
| /// NumGapBlocks - Number of duplicate entries in UseBlocks for blocks where |
| /// the live range has a gap. |
| unsigned NumGapBlocks; |
| |
| /// ThroughBlocks - Block numbers where CurLI is live through without uses. |
| BitVector ThroughBlocks; |
| |
| /// NumThroughBlocks - Number of live-through blocks. |
| unsigned NumThroughBlocks; |
| |
| /// DidRepairRange - analyze was forced to shrinkToUses(). |
| bool DidRepairRange; |
| |
| SlotIndex computeLastSplitPoint(unsigned Num); |
| |
| // Sumarize statistics by counting instructions using CurLI. |
| void analyzeUses(); |
| |
| /// calcLiveBlockInfo - Compute per-block information about CurLI. |
| bool calcLiveBlockInfo(); |
| |
| public: |
| SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis, |
| const MachineLoopInfo &mli); |
| |
| /// analyze - set CurLI to the specified interval, and analyze how it may be |
| /// split. |
| void analyze(const LiveInterval *li); |
| |
| /// didRepairRange() - Returns true if CurLI was invalid and has been repaired |
| /// by analyze(). This really shouldn't happen, but sometimes the coalescer |
| /// can create live ranges that end in mid-air. |
| bool didRepairRange() const { return DidRepairRange; } |
| |
| /// clear - clear all data structures so SplitAnalysis is ready to analyze a |
| /// new interval. |
| void clear(); |
| |
| /// getParent - Return the last analyzed interval. |
| const LiveInterval &getParent() const { return *CurLI; } |
| |
| /// getLastSplitPoint - Return the base index of the last valid split point |
| /// in the basic block numbered Num. |
| SlotIndex getLastSplitPoint(unsigned Num) { |
| // Inline the common simple case. |
| if (LastSplitPoint[Num].first.isValid() && |
| !LastSplitPoint[Num].second.isValid()) |
| return LastSplitPoint[Num].first; |
| return computeLastSplitPoint(Num); |
| } |
| |
| /// getLastSplitPointIter - Returns the last split point as an iterator. |
| MachineBasicBlock::iterator getLastSplitPointIter(MachineBasicBlock*); |
| |
| /// isOriginalEndpoint - Return true if the original live range was killed or |
| /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def, |
| /// and 'use' for an early-clobber def. |
| /// This can be used to recognize code inserted by earlier live range |
| /// splitting. |
| bool isOriginalEndpoint(SlotIndex Idx) const; |
| |
| /// getUseSlots - Return an array of SlotIndexes of instructions using CurLI. |
| /// This include both use and def operands, at most one entry per instruction. |
| ArrayRef<SlotIndex> getUseSlots() const { return UseSlots; } |
| |
| /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks |
| /// where CurLI has uses. |
| ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; } |
| |
| /// getNumThroughBlocks - Return the number of through blocks. |
| unsigned getNumThroughBlocks() const { return NumThroughBlocks; } |
| |
| /// isThroughBlock - Return true if CurLI is live through MBB without uses. |
| bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); } |
| |
| /// getThroughBlocks - Return the set of through blocks. |
| const BitVector &getThroughBlocks() const { return ThroughBlocks; } |
| |
| /// getNumLiveBlocks - Return the number of blocks where CurLI is live. |
| unsigned getNumLiveBlocks() const { |
| return getUseBlocks().size() - NumGapBlocks + getNumThroughBlocks(); |
| } |
| |
| /// countLiveBlocks - Return the number of blocks where li is live. This is |
| /// guaranteed to return the same number as getNumLiveBlocks() after calling |
| /// analyze(li). |
| unsigned countLiveBlocks(const LiveInterval *li) const; |
| |
| typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; |
| |
| /// shouldSplitSingleBlock - Returns true if it would help to create a local |
| /// live range for the instructions in BI. There is normally no benefit to |
| /// creating a live range for a single instruction, but it does enable |
| /// register class inflation if the instruction has a restricted register |
| /// class. |
| /// |
| /// @param BI The block to be isolated. |
| /// @param SingleInstrs True when single instructions should be isolated. |
| bool shouldSplitSingleBlock(const BlockInfo &BI, bool SingleInstrs) const; |
| }; |
| |
| |
| /// SplitEditor - Edit machine code and LiveIntervals for live range |
| /// splitting. |
| /// |
| /// - Create a SplitEditor from a SplitAnalysis. |
| /// - Start a new live interval with openIntv. |
| /// - Mark the places where the new interval is entered using enterIntv* |
| /// - Mark the ranges where the new interval is used with useIntv* |
| /// - Mark the places where the interval is exited with exitIntv*. |
| /// - Finish the current interval with closeIntv and repeat from 2. |
| /// - Rewrite instructions with finish(). |
| /// |
| class SplitEditor { |
| SplitAnalysis &SA; |
| LiveIntervals &LIS; |
| VirtRegMap &VRM; |
| MachineRegisterInfo &MRI; |
| MachineDominatorTree &MDT; |
| const TargetInstrInfo &TII; |
| const TargetRegisterInfo &TRI; |
| |
| public: |
| |
| /// ComplementSpillMode - Select how the complement live range should be |
| /// created. SplitEditor automatically creates interval 0 to contain |
| /// anything that isn't added to another interval. This complement interval |
| /// can get quite complicated, and it can sometimes be an advantage to allow |
| /// it to overlap the other intervals. If it is going to spill anyway, no |
| /// registers are wasted by keeping a value in two places at the same time. |
| enum ComplementSpillMode { |
| /// SM_Partition(Default) - Try to create the complement interval so it |
| /// doesn't overlap any other intervals, and the original interval is |
| /// partitioned. This may require a large number of back copies and extra |
| /// PHI-defs. Only segments marked with overlapIntv will be overlapping. |
| SM_Partition, |
| |
| /// SM_Size - Overlap intervals to minimize the number of inserted COPY |
| /// instructions. Copies to the complement interval are hoisted to their |
| /// common dominator, so only one COPY is required per value in the |
| /// complement interval. This also means that no extra PHI-defs need to be |
| /// inserted in the complement interval. |
| SM_Size, |
| |
| /// SM_Speed - Overlap intervals to minimize the expected execution |
| /// frequency of the inserted copies. This is very similar to SM_Size, but |
| /// the complement interval may get some extra PHI-defs. |
| SM_Speed |
| }; |
| |
| private: |
| |
| /// Edit - The current parent register and new intervals created. |
| LiveRangeEdit *Edit; |
| |
| /// Index into Edit of the currently open interval. |
| /// The index 0 is used for the complement, so the first interval started by |
| /// openIntv will be 1. |
| unsigned OpenIdx; |
| |
| /// The current spill mode, selected by reset(). |
| ComplementSpillMode SpillMode; |
| |
| typedef IntervalMap<SlotIndex, unsigned> RegAssignMap; |
| |
| /// Allocator for the interval map. This will eventually be shared with |
| /// SlotIndexes and LiveIntervals. |
| RegAssignMap::Allocator Allocator; |
| |
| /// RegAssign - Map of the assigned register indexes. |
| /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at |
| /// Idx. |
| RegAssignMap RegAssign; |
| |
| typedef PointerIntPair<VNInfo*, 1> ValueForcePair; |
| typedef DenseMap<std::pair<unsigned, unsigned>, ValueForcePair> ValueMap; |
| |
| /// Values - keep track of the mapping from parent values to values in the new |
| /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains: |
| /// |
| /// 1. No entry - the value is not mapped to Edit.get(RegIdx). |
| /// 2. (Null, false) - the value is mapped to multiple values in |
| /// Edit.get(RegIdx). Each value is represented by a minimal live range at |
| /// its def. The full live range can be inferred exactly from the range |
| /// of RegIdx in RegAssign. |
| /// 3. (Null, true). As above, but the ranges in RegAssign are too large, and |
| /// the live range must be recomputed using LiveRangeCalc::extend(). |
| /// 4. (VNI, false) The value is mapped to a single new value. |
| /// The new value has no live ranges anywhere. |
| ValueMap Values; |
| |
| /// LRCalc - Cache for computing live ranges and SSA update. Each instance |
| /// can only handle non-overlapping live ranges, so use a separate |
| /// LiveRangeCalc instance for the complement interval when in spill mode. |
| LiveRangeCalc LRCalc[2]; |
| |
| /// getLRCalc - Return the LRCalc to use for RegIdx. In spill mode, the |
| /// complement interval can overlap the other intervals, so it gets its own |
| /// LRCalc instance. When not in spill mode, all intervals can share one. |
| LiveRangeCalc &getLRCalc(unsigned RegIdx) { |
| return LRCalc[SpillMode != SM_Partition && RegIdx != 0]; |
| } |
| |
| /// defValue - define a value in RegIdx from ParentVNI at Idx. |
| /// Idx does not have to be ParentVNI->def, but it must be contained within |
| /// ParentVNI's live range in ParentLI. The new value is added to the value |
| /// map. |
| /// Return the new LI value. |
| VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx); |
| |
| /// forceRecompute - Force the live range of ParentVNI in RegIdx to be |
| /// recomputed by LiveRangeCalc::extend regardless of the number of defs. |
| /// This is used for values whose live range doesn't match RegAssign exactly. |
| /// They could have rematerialized, or back-copies may have been moved. |
| void forceRecompute(unsigned RegIdx, const VNInfo *ParentVNI); |
| |
| /// defFromParent - Define Reg from ParentVNI at UseIdx using either |
| /// rematerialization or a COPY from parent. Return the new value. |
| VNInfo *defFromParent(unsigned RegIdx, |
| VNInfo *ParentVNI, |
| SlotIndex UseIdx, |
| MachineBasicBlock &MBB, |
| MachineBasicBlock::iterator I); |
| |
| /// removeBackCopies - Remove the copy instructions that defines the values |
| /// in the vector in the complement interval. |
| void removeBackCopies(SmallVectorImpl<VNInfo*> &Copies); |
| |
| /// getShallowDominator - Returns the least busy dominator of MBB that is |
| /// also dominated by DefMBB. Busy is measured by loop depth. |
| MachineBasicBlock *findShallowDominator(MachineBasicBlock *MBB, |
| MachineBasicBlock *DefMBB); |
| |
| /// hoistCopiesForSize - Hoist back-copies to the complement interval in a |
| /// way that minimizes code size. This implements the SM_Size spill mode. |
| void hoistCopiesForSize(); |
| |
| /// transferValues - Transfer values to the new ranges. |
| /// Return true if any ranges were skipped. |
| bool transferValues(); |
| |
| /// extendPHIKillRanges - Extend the ranges of all values killed by original |
| /// parent PHIDefs. |
| void extendPHIKillRanges(); |
| |
| /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers. |
| void rewriteAssigned(bool ExtendRanges); |
| |
| /// deleteRematVictims - Delete defs that are dead after rematerializing. |
| void deleteRematVictims(); |
| |
| public: |
| /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. |
| /// Newly created intervals will be appended to newIntervals. |
| SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, |
| MachineDominatorTree&); |
| |
| /// reset - Prepare for a new split. |
| void reset(LiveRangeEdit&, ComplementSpillMode = SM_Partition); |
| |
| /// Create a new virtual register and live interval. |
| /// Return the interval index, starting from 1. Interval index 0 is the |
| /// implicit complement interval. |
| unsigned openIntv(); |
| |
| /// currentIntv - Return the current interval index. |
| unsigned currentIntv() const { return OpenIdx; } |
| |
| /// selectIntv - Select a previously opened interval index. |
| void selectIntv(unsigned Idx); |
| |
| /// enterIntvBefore - Enter the open interval before the instruction at Idx. |
| /// If the parent interval is not live before Idx, a COPY is not inserted. |
| /// Return the beginning of the new live range. |
| SlotIndex enterIntvBefore(SlotIndex Idx); |
| |
| /// enterIntvAfter - Enter the open interval after the instruction at Idx. |
| /// Return the beginning of the new live range. |
| SlotIndex enterIntvAfter(SlotIndex Idx); |
| |
| /// enterIntvAtEnd - Enter the open interval at the end of MBB. |
| /// Use the open interval from he inserted copy to the MBB end. |
| /// Return the beginning of the new live range. |
| SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB); |
| |
| /// useIntv - indicate that all instructions in MBB should use OpenLI. |
| void useIntv(const MachineBasicBlock &MBB); |
| |
| /// useIntv - indicate that all instructions in range should use OpenLI. |
| void useIntv(SlotIndex Start, SlotIndex End); |
| |
| /// leaveIntvAfter - Leave the open interval after the instruction at Idx. |
| /// Return the end of the live range. |
| SlotIndex leaveIntvAfter(SlotIndex Idx); |
| |
| /// leaveIntvBefore - Leave the open interval before the instruction at Idx. |
| /// Return the end of the live range. |
| SlotIndex leaveIntvBefore(SlotIndex Idx); |
| |
| /// leaveIntvAtTop - Leave the interval at the top of MBB. |
| /// Add liveness from the MBB top to the copy. |
| /// Return the end of the live range. |
| SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB); |
| |
| /// overlapIntv - Indicate that all instructions in range should use the open |
| /// interval, but also let the complement interval be live. |
| /// |
| /// This doubles the register pressure, but is sometimes required to deal with |
| /// register uses after the last valid split point. |
| /// |
| /// The Start index should be a return value from a leaveIntv* call, and End |
| /// should be in the same basic block. The parent interval must have the same |
| /// value across the range. |
| /// |
| void overlapIntv(SlotIndex Start, SlotIndex End); |
| |
| /// finish - after all the new live ranges have been created, compute the |
| /// remaining live range, and rewrite instructions to use the new registers. |
| /// @param LRMap When not null, this vector will map each live range in Edit |
| /// back to the indices returned by openIntv. |
| /// There may be extra indices created by dead code elimination. |
| void finish(SmallVectorImpl<unsigned> *LRMap = 0); |
| |
| /// dump - print the current interval maping to dbgs(). |
| void dump() const; |
| |
| // ===--- High level methods ---=== |
| |
| /// splitSingleBlock - Split CurLI into a separate live interval around the |
| /// uses in a single block. This is intended to be used as part of a larger |
| /// split, and doesn't call finish(). |
| void splitSingleBlock(const SplitAnalysis::BlockInfo &BI); |
| |
| /// splitLiveThroughBlock - Split CurLI in the given block such that it |
| /// enters the block in IntvIn and leaves it in IntvOut. There may be uses in |
| /// the block, but they will be ignored when placing split points. |
| /// |
| /// @param MBBNum Block number. |
| /// @param IntvIn Interval index entering the block. |
| /// @param LeaveBefore When set, leave IntvIn before this point. |
| /// @param IntvOut Interval index leaving the block. |
| /// @param EnterAfter When set, enter IntvOut after this point. |
| void splitLiveThroughBlock(unsigned MBBNum, |
| unsigned IntvIn, SlotIndex LeaveBefore, |
| unsigned IntvOut, SlotIndex EnterAfter); |
| |
| /// splitRegInBlock - Split CurLI in the given block such that it enters the |
| /// block in IntvIn and leaves it on the stack (or not at all). Split points |
| /// are placed in a way that avoids putting uses in the stack interval. This |
| /// may require creating a local interval when there is interference. |
| /// |
| /// @param BI Block descriptor. |
| /// @param IntvIn Interval index entering the block. Not 0. |
| /// @param LeaveBefore When set, leave IntvIn before this point. |
| void splitRegInBlock(const SplitAnalysis::BlockInfo &BI, |
| unsigned IntvIn, SlotIndex LeaveBefore); |
| |
| /// splitRegOutBlock - Split CurLI in the given block such that it enters the |
| /// block on the stack (or isn't live-in at all) and leaves it in IntvOut. |
| /// Split points are placed to avoid interference and such that the uses are |
| /// not in the stack interval. This may require creating a local interval |
| /// when there is interference. |
| /// |
| /// @param BI Block descriptor. |
| /// @param IntvOut Interval index leaving the block. |
| /// @param EnterAfter When set, enter IntvOut after this point. |
| void splitRegOutBlock(const SplitAnalysis::BlockInfo &BI, |
| unsigned IntvOut, SlotIndex EnterAfter); |
| }; |
| |
| } |
| |
| #endif |