Coverage Report

Created: 2017-10-03 07:32

/Users/buildslave/jenkins/sharedspace/clang-stage2-coverage-R@2/llvm/lib/CodeGen/SplitKit.h
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//===- SplitKit.h - Toolkit for splitting live ranges -----------*- C++ -*-===//
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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 contains the SplitAnalysis class as well as mutator functions for
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// live range splitting.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_CODEGEN_SPLITKIT_H
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#define LLVM_LIB_CODEGEN_SPLITKIT_H
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#include "LiveRangeCalc.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/BitVector.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/IntervalMap.h"
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#include "llvm/ADT/PointerIntPair.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/CodeGen/LiveInterval.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/SlotIndexes.h"
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#include "llvm/MC/LaneBitmask.h"
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#include "llvm/Support/Compiler.h"
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#include <utility>
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namespace llvm {
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class LiveIntervals;
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class LiveRangeEdit;
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class MachineBlockFrequencyInfo;
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class MachineDominatorTree;
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class MachineLoopInfo;
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class MachineRegisterInfo;
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class TargetInstrInfo;
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class TargetRegisterInfo;
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class VirtRegMap;
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/// Determines the latest safe point in a block in which we can insert a split,
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/// spill or other instruction related with CurLI.
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class LLVM_LIBRARY_VISIBILITY InsertPointAnalysis {
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private:
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  const LiveIntervals &LIS;
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  /// Last legal insert point in each basic block in the current function.
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  /// The first entry is the first terminator, the second entry is the
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  /// last valid point to insert a split or spill for a variable that is
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  /// live into a landing pad successor.
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  SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastInsertPoint;
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  SlotIndex computeLastInsertPoint(const LiveInterval &CurLI,
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                                   const MachineBasicBlock &MBB);
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public:
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  InsertPointAnalysis(const LiveIntervals &lis, unsigned BBNum);
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  /// Return the base index of the last valid insert point for \pCurLI in \pMBB.
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  SlotIndex getLastInsertPoint(const LiveInterval &CurLI,
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43.5M
                               const MachineBasicBlock &MBB) {
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43.5M
    unsigned Num = MBB.getNumber();
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43.5M
    // Inline the common simple case.
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43.5M
    if (LastInsertPoint[Num].first.isValid() &&
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42.3M
        !LastInsertPoint[Num].second.isValid())
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41.4M
      return LastInsertPoint[Num].first;
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2.05M
    return computeLastInsertPoint(CurLI, MBB);
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43.5M
  }
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  /// Returns the last insert point as an iterator for \pCurLI in \pMBB.
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  MachineBasicBlock::iterator getLastInsertPointIter(const LiveInterval &CurLI,
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                                                     MachineBasicBlock &MBB);
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};
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/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
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/// opportunities.
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class LLVM_LIBRARY_VISIBILITY SplitAnalysis {
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public:
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  const MachineFunction &MF;
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  const VirtRegMap &VRM;
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  const LiveIntervals &LIS;
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  const MachineLoopInfo &Loops;
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  const TargetInstrInfo &TII;
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  /// Additional information about basic blocks where the current variable is
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  /// live. Such a block will look like one of these templates:
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  ///
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  ///  1. |   o---x   | Internal to block. Variable is only live in this block.
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  ///  2. |---x       | Live-in, kill.
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  ///  3. |       o---| Def, live-out.
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  ///  4. |---x   o---| Live-in, kill, def, live-out. Counted by NumGapBlocks.
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  ///  5. |---o---o---| Live-through with uses or defs.
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  ///  6. |-----------| Live-through without uses. Counted by NumThroughBlocks.
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  ///
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  /// Two BlockInfo entries are created for template 4. One for the live-in
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  /// segment, and one for the live-out segment. These entries look as if the
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  /// block were split in the middle where the live range isn't live.
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  ///
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  /// Live-through blocks without any uses don't get BlockInfo entries. They
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  /// are simply listed in ThroughBlocks instead.
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  ///
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  struct BlockInfo {
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    MachineBasicBlock *MBB;
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    SlotIndex FirstInstr; ///< First instr accessing current reg.
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    SlotIndex LastInstr;  ///< Last instr accessing current reg.
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    SlotIndex FirstDef;   ///< First non-phi valno->def, or SlotIndex().
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    bool LiveIn;          ///< Current reg is live in.
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    bool LiveOut;         ///< Current reg is live out.
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    /// isOneInstr - Returns true when this BlockInfo describes a single
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    /// instruction.
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408k
    bool isOneInstr() const {
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408k
      return SlotIndex::isSameInstr(FirstInstr, LastInstr);
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408k
    }
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  };
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private:
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  // Current live interval.
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  const LiveInterval *CurLI = nullptr;
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  /// Insert Point Analysis.
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  InsertPointAnalysis IPA;
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  // Sorted slot indexes of using instructions.
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  SmallVector<SlotIndex, 8> UseSlots;
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  /// UseBlocks - Blocks where CurLI has uses.
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  SmallVector<BlockInfo, 8> UseBlocks;
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  /// NumGapBlocks - Number of duplicate entries in UseBlocks for blocks where
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  /// the live range has a gap.
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  unsigned NumGapBlocks;
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  /// ThroughBlocks - Block numbers where CurLI is live through without uses.
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  BitVector ThroughBlocks;
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  /// NumThroughBlocks - Number of live-through blocks.
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  unsigned NumThroughBlocks;
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  /// DidRepairRange - analyze was forced to shrinkToUses().
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  bool DidRepairRange;
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  // Sumarize statistics by counting instructions using CurLI.
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  void analyzeUses();
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  /// calcLiveBlockInfo - Compute per-block information about CurLI.
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  bool calcLiveBlockInfo();
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public:
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  SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
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                const MachineLoopInfo &mli);
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  /// analyze - set CurLI to the specified interval, and analyze how it may be
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  /// split.
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  void analyze(const LiveInterval *li);
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  /// didRepairRange() - Returns true if CurLI was invalid and has been repaired
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  /// by analyze(). This really shouldn't happen, but sometimes the coalescer
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  /// can create live ranges that end in mid-air.
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225k
  bool didRepairRange() const { return DidRepairRange; }
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  /// clear - clear all data structures so SplitAnalysis is ready to analyze a
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  /// new interval.
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  void clear();
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  /// getParent - Return the last analyzed interval.
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671k
  const LiveInterval &getParent() const { return *CurLI; }
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  /// isOriginalEndpoint - Return true if the original live range was killed or
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  /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def,
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  /// and 'use' for an early-clobber def.
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  /// This can be used to recognize code inserted by earlier live range
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  /// splitting.
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  bool isOriginalEndpoint(SlotIndex Idx) const;
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  /// getUseSlots - Return an array of SlotIndexes of instructions using CurLI.
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  /// This include both use and def operands, at most one entry per instruction.
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649k
  ArrayRef<SlotIndex> getUseSlots() const { return UseSlots; }
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  /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks
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  /// where CurLI has uses.
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14.1M
  ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; }
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  /// getNumThroughBlocks - Return the number of through blocks.
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305k
  unsigned getNumThroughBlocks() const { return NumThroughBlocks; }
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  /// isThroughBlock - Return true if CurLI is live through MBB without uses.
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0
  bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); }
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  /// getThroughBlocks - Return the set of through blocks.
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4.47M
  const BitVector &getThroughBlocks() const { return ThroughBlocks; }
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  /// getNumLiveBlocks - Return the number of blocks where CurLI is live.
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80.5k
  unsigned getNumLiveBlocks() const {
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80.5k
    return getUseBlocks().size() - NumGapBlocks + getNumThroughBlocks();
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80.5k
  }
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  /// countLiveBlocks - Return the number of blocks where li is live. This is
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  /// guaranteed to return the same number as getNumLiveBlocks() after calling
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  /// analyze(li).
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  unsigned countLiveBlocks(const LiveInterval *li) const;
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  using BlockPtrSet = SmallPtrSet<const MachineBasicBlock *, 16>;
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  /// shouldSplitSingleBlock - Returns true if it would help to create a local
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  /// live range for the instructions in BI. There is normally no benefit to
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  /// creating a live range for a single instruction, but it does enable
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  /// register class inflation if the instruction has a restricted register
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  /// class.
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  ///
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  /// @param BI           The block to be isolated.
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  /// @param SingleInstrs True when single instructions should be isolated.
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  bool shouldSplitSingleBlock(const BlockInfo &BI, bool SingleInstrs) const;
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43.1M
  SlotIndex getLastSplitPoint(unsigned Num) {
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43.1M
    return IPA.getLastInsertPoint(*CurLI, *MF.getBlockNumbered(Num));
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43.1M
  }
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113k
  MachineBasicBlock::iterator getLastSplitPointIter(MachineBasicBlock *BB) {
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113k
    return IPA.getLastInsertPointIter(*CurLI, *BB);
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113k
  }
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};
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/// SplitEditor - Edit machine code and LiveIntervals for live range
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/// splitting.
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///
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/// - Create a SplitEditor from a SplitAnalysis.
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/// - Start a new live interval with openIntv.
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/// - Mark the places where the new interval is entered using enterIntv*
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/// - Mark the ranges where the new interval is used with useIntv* 
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/// - Mark the places where the interval is exited with exitIntv*.
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/// - Finish the current interval with closeIntv and repeat from 2.
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/// - Rewrite instructions with finish().
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///
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class LLVM_LIBRARY_VISIBILITY SplitEditor {
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  SplitAnalysis &SA;
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  AliasAnalysis &AA;
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  LiveIntervals &LIS;
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  VirtRegMap &VRM;
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  MachineRegisterInfo &MRI;
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  MachineDominatorTree &MDT;
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  const TargetInstrInfo &TII;
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  const TargetRegisterInfo &TRI;
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  const MachineBlockFrequencyInfo &MBFI;
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public:
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  /// ComplementSpillMode - Select how the complement live range should be
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  /// created.  SplitEditor automatically creates interval 0 to contain
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  /// anything that isn't added to another interval.  This complement interval
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  /// can get quite complicated, and it can sometimes be an advantage to allow
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  /// it to overlap the other intervals.  If it is going to spill anyway, no
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  /// registers are wasted by keeping a value in two places at the same time.
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  enum ComplementSpillMode {
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    /// SM_Partition(Default) - Try to create the complement interval so it
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    /// doesn't overlap any other intervals, and the original interval is
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    /// partitioned.  This may require a large number of back copies and extra
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    /// PHI-defs.  Only segments marked with overlapIntv will be overlapping.
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    SM_Partition,
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    /// SM_Size - Overlap intervals to minimize the number of inserted COPY
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    /// instructions.  Copies to the complement interval are hoisted to their
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    /// common dominator, so only one COPY is required per value in the
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    /// complement interval.  This also means that no extra PHI-defs need to be
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    /// inserted in the complement interval.
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    SM_Size,
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    /// SM_Speed - Overlap intervals to minimize the expected execution
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    /// frequency of the inserted copies.  This is very similar to SM_Size, but
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    /// the complement interval may get some extra PHI-defs.
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    SM_Speed
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  };
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private:
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  /// Edit - The current parent register and new intervals created.
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  LiveRangeEdit *Edit = nullptr;
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  /// Index into Edit of the currently open interval.
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  /// The index 0 is used for the complement, so the first interval started by
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  /// openIntv will be 1.
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  unsigned OpenIdx = 0;
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  /// The current spill mode, selected by reset().
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  ComplementSpillMode SpillMode = SM_Partition;
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  using RegAssignMap = IntervalMap<SlotIndex, unsigned>;
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  /// Allocator for the interval map. This will eventually be shared with
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  /// SlotIndexes and LiveIntervals.
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  RegAssignMap::Allocator Allocator;
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  /// RegAssign - Map of the assigned register indexes.
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  /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
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  /// Idx.
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  RegAssignMap RegAssign;
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  using ValueForcePair = PointerIntPair<VNInfo *, 1>;
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  using ValueMap = DenseMap<std::pair<unsigned, unsigned>, ValueForcePair>;
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  /// Values - keep track of the mapping from parent values to values in the new
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  /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains:
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  ///
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  /// 1. No entry - the value is not mapped to Edit.get(RegIdx).
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  /// 2. (Null, false) - the value is mapped to multiple values in
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  ///    Edit.get(RegIdx).  Each value is represented by a minimal live range at
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  ///    its def.  The full live range can be inferred exactly from the range
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  ///    of RegIdx in RegAssign.
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  /// 3. (Null, true).  As above, but the ranges in RegAssign are too large, and
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  ///    the live range must be recomputed using LiveRangeCalc::extend().
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  /// 4. (VNI, false) The value is mapped to a single new value.
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  ///    The new value has no live ranges anywhere.
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  ValueMap Values;
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  /// LRCalc - Cache for computing live ranges and SSA update.  Each instance
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  /// can only handle non-overlapping live ranges, so use a separate
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  /// LiveRangeCalc instance for the complement interval when in spill mode.
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  LiveRangeCalc LRCalc[2];
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  /// getLRCalc - Return the LRCalc to use for RegIdx.  In spill mode, the
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  /// complement interval can overlap the other intervals, so it gets its own
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  /// LRCalc instance.  When not in spill mode, all intervals can share one.
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753k
  LiveRangeCalc &getLRCalc(unsigned RegIdx) {
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747k
    return LRCalc[SpillMode != SM_Partition && RegIdx != 0];
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753k
  }
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  /// Find a subrange corresponding to the lane mask @p LM in the live
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  /// interval @p LI. The interval @p LI is assumed to contain such a subrange.
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  /// This function is used to find corresponding subranges between the
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  /// original interval and the new intervals.
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  LiveInterval::SubRange &getSubRangeForMask(LaneBitmask LM, LiveInterval &LI);
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  /// Add a segment to the interval LI for the value number VNI. If LI has
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  /// subranges, corresponding segments will be added to them as well, but
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  /// with newly created value numbers. If Original is true, dead def will
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  /// only be added a subrange of LI if the corresponding subrange of the
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  /// original interval has a def at this index. Otherwise, all subranges
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  /// of LI will be updated.
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  void addDeadDef(LiveInterval &LI, VNInfo *VNI, bool Original);
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  /// defValue - define a value in RegIdx from ParentVNI at Idx.
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  /// Idx does not have to be ParentVNI->def, but it must be contained within
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  /// ParentVNI's live range in ParentLI. The new value is added to the value
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  /// map. The value being defined may either come from rematerialization
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  /// (or an inserted copy), or it may be coming from the original interval.
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  /// The parameter Original should be true in the latter case, otherwise
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  /// it should be false.
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  /// Return the new LI value.
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  VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx,
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                   bool Original);
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  /// forceRecompute - Force the live range of ParentVNI in RegIdx to be
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  /// recomputed by LiveRangeCalc::extend regardless of the number of defs.
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  /// This is used for values whose live range doesn't match RegAssign exactly.
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  /// They could have rematerialized, or back-copies may have been moved.
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  void forceRecompute(unsigned RegIdx, const VNInfo *ParentVNI);
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362
  /// defFromParent - Define Reg from ParentVNI at UseIdx using either
363
  /// rematerialization or a COPY from parent. Return the new value.
364
  VNInfo *defFromParent(unsigned RegIdx,
365
                        VNInfo *ParentVNI,
366
                        SlotIndex UseIdx,
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                        MachineBasicBlock &MBB,
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                        MachineBasicBlock::iterator I);
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370
  /// removeBackCopies - Remove the copy instructions that defines the values
371
  /// in the vector in the complement interval.
372
  void removeBackCopies(SmallVectorImpl<VNInfo*> &Copies);
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374
  /// getShallowDominator - Returns the least busy dominator of MBB that is
375
  /// also dominated by DefMBB.  Busy is measured by loop depth.
376
  MachineBasicBlock *findShallowDominator(MachineBasicBlock *MBB,
377
                                          MachineBasicBlock *DefMBB);
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379
  /// Find out all the backCopies dominated by others.
380
  void computeRedundantBackCopies(DenseSet<unsigned> &NotToHoistSet,
381
                                  SmallVectorImpl<VNInfo *> &BackCopies);
382
383
  /// Hoist back-copies to the complement interval. It tries to hoist all
384
  /// the back-copies to one BB if it is beneficial, or else simply remove
385
  /// redundant backcopies dominated by others.
386
  void hoistCopies();
387
388
  /// transferValues - Transfer values to the new ranges.
389
  /// Return true if any ranges were skipped.
390
  bool transferValues();
391
392
  /// Live range @p LR corresponding to the lane Mask @p LM has a live
393
  /// PHI def at the beginning of block @p B. Extend the range @p LR of
394
  /// all predecessor values that reach this def. If @p LR is a subrange,
395
  /// the array @p Undefs is the set of all locations where it is undefined
396
  /// via <def,read-undef> in other subranges for the same register.
397
  void extendPHIRange(MachineBasicBlock &B, LiveRangeCalc &LRC,
398
                      LiveRange &LR, LaneBitmask LM,
399
                      ArrayRef<SlotIndex> Undefs);
400
401
  /// extendPHIKillRanges - Extend the ranges of all values killed by original
402
  /// parent PHIDefs.
403
  void extendPHIKillRanges();
404
405
  /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
406
  void rewriteAssigned(bool ExtendRanges);
407
408
  /// deleteRematVictims - Delete defs that are dead after rematerializing.
409
  void deleteRematVictims();
410
411
  /// Add a copy instruction copying \p FromReg to \p ToReg before
412
  /// \p InsertBefore. This can be invoked with a \p LaneMask which may make it
413
  /// necessary to construct a sequence of copies to cover it exactly.
414
  SlotIndex buildCopy(unsigned FromReg, unsigned ToReg, LaneBitmask LaneMask,
415
      MachineBasicBlock &MBB, MachineBasicBlock::iterator InsertBefore,
416
      bool Late, unsigned RegIdx);
417
418
  SlotIndex buildSingleSubRegCopy(unsigned FromReg, unsigned ToReg,
419
      MachineBasicBlock &MB, MachineBasicBlock::iterator InsertBefore,
420
      unsigned SubIdx, LiveInterval &DestLI, bool Late, SlotIndex PrevCopy);
421
422
public:
423
  /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
424
  /// Newly created intervals will be appended to newIntervals.
425
  SplitEditor(SplitAnalysis &sa, AliasAnalysis &aa, LiveIntervals &lis,
426
              VirtRegMap &vrm, MachineDominatorTree &mdt,
427
              MachineBlockFrequencyInfo &mbfi);
428
429
  /// reset - Prepare for a new split.
430
  void reset(LiveRangeEdit&, ComplementSpillMode = SM_Partition);
431
432
  /// Create a new virtual register and live interval.
433
  /// Return the interval index, starting from 1. Interval index 0 is the
434
  /// implicit complement interval.
435
  unsigned openIntv();
436
437
  /// currentIntv - Return the current interval index.
438
0
  unsigned currentIntv() const { return OpenIdx; }
439
440
  /// selectIntv - Select a previously opened interval index.
441
  void selectIntv(unsigned Idx);
442
443
  /// enterIntvBefore - Enter the open interval before the instruction at Idx.
444
  /// If the parent interval is not live before Idx, a COPY is not inserted.
445
  /// Return the beginning of the new live range.
446
  SlotIndex enterIntvBefore(SlotIndex Idx);
447
448
  /// enterIntvAfter - Enter the open interval after the instruction at Idx.
449
  /// Return the beginning of the new live range.
450
  SlotIndex enterIntvAfter(SlotIndex Idx);
451
452
  /// enterIntvAtEnd - Enter the open interval at the end of MBB.
453
  /// Use the open interval from the inserted copy to the MBB end.
454
  /// Return the beginning of the new live range.
455
  SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
456
457
  /// useIntv - indicate that all instructions in MBB should use OpenLI.
458
  void useIntv(const MachineBasicBlock &MBB);
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460
  /// useIntv - indicate that all instructions in range should use OpenLI.
461
  void useIntv(SlotIndex Start, SlotIndex End);
462
463
  /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
464
  /// Return the end of the live range.
465
  SlotIndex leaveIntvAfter(SlotIndex Idx);
466
467
  /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
468
  /// Return the end of the live range.
469
  SlotIndex leaveIntvBefore(SlotIndex Idx);
470
471
  /// leaveIntvAtTop - Leave the interval at the top of MBB.
472
  /// Add liveness from the MBB top to the copy.
473
  /// Return the end of the live range.
474
  SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
475
476
  /// overlapIntv - Indicate that all instructions in range should use the open
477
  /// interval, but also let the complement interval be live.
478
  ///
479
  /// This doubles the register pressure, but is sometimes required to deal with
480
  /// register uses after the last valid split point.
481
  ///
482
  /// The Start index should be a return value from a leaveIntv* call, and End
483
  /// should be in the same basic block. The parent interval must have the same
484
  /// value across the range.
485
  ///
486
  void overlapIntv(SlotIndex Start, SlotIndex End);
487
488
  /// finish - after all the new live ranges have been created, compute the
489
  /// remaining live range, and rewrite instructions to use the new registers.
490
  /// @param LRMap When not null, this vector will map each live range in Edit
491
  ///              back to the indices returned by openIntv.
492
  ///              There may be extra indices created by dead code elimination.
493
  void finish(SmallVectorImpl<unsigned> *LRMap = nullptr);
494
495
  /// dump - print the current interval mapping to dbgs().
496
  void dump() const;
497
498
  // ===--- High level methods ---===
499
500
  /// splitSingleBlock - Split CurLI into a separate live interval around the
501
  /// uses in a single block. This is intended to be used as part of a larger
502
  /// split, and doesn't call finish().
503
  void splitSingleBlock(const SplitAnalysis::BlockInfo &BI);
504
505
  /// splitLiveThroughBlock - Split CurLI in the given block such that it
506
  /// enters the block in IntvIn and leaves it in IntvOut. There may be uses in
507
  /// the block, but they will be ignored when placing split points.
508
  ///
509
  /// @param MBBNum      Block number.
510
  /// @param IntvIn      Interval index entering the block.
511
  /// @param LeaveBefore When set, leave IntvIn before this point.
512
  /// @param IntvOut     Interval index leaving the block.
513
  /// @param EnterAfter  When set, enter IntvOut after this point.
514
  void splitLiveThroughBlock(unsigned MBBNum,
515
                             unsigned IntvIn, SlotIndex LeaveBefore,
516
                             unsigned IntvOut, SlotIndex EnterAfter);
517
518
  /// splitRegInBlock - Split CurLI in the given block such that it enters the
519
  /// block in IntvIn and leaves it on the stack (or not at all). Split points
520
  /// are placed in a way that avoids putting uses in the stack interval. This
521
  /// may require creating a local interval when there is interference.
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  ///
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  /// @param BI          Block descriptor.
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  /// @param IntvIn      Interval index entering the block. Not 0.
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  /// @param LeaveBefore When set, leave IntvIn before this point.
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  void splitRegInBlock(const SplitAnalysis::BlockInfo &BI,
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                       unsigned IntvIn, SlotIndex LeaveBefore);
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  /// splitRegOutBlock - Split CurLI in the given block such that it enters the
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  /// block on the stack (or isn't live-in at all) and leaves it in IntvOut.
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  /// Split points are placed to avoid interference and such that the uses are
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  /// not in the stack interval. This may require creating a local interval
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  /// when there is interference.
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  ///
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  /// @param BI          Block descriptor.
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  /// @param IntvOut     Interval index leaving the block.
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  /// @param EnterAfter  When set, enter IntvOut after this point.
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  void splitRegOutBlock(const SplitAnalysis::BlockInfo &BI,
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                        unsigned IntvOut, SlotIndex EnterAfter);
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};
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} // end namespace llvm
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#endif // LLVM_LIB_CODEGEN_SPLITKIT_H