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map discovers the iterated dominance frontier for free. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111400 91177308-0d34-0410-b5e6-96231b3b80d8
322 lines
12 KiB
C++
322 lines
12 KiB
C++
//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===//
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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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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/CodeGen/SlotIndexes.h"
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namespace llvm {
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class LiveInterval;
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class LiveIntervals;
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class MachineInstr;
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class MachineLoop;
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class MachineLoopInfo;
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class MachineRegisterInfo;
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class TargetInstrInfo;
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class VirtRegMap;
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class VNInfo;
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/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
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/// opportunities.
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class SplitAnalysis {
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public:
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const MachineFunction &mf_;
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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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// Instructions using the the current register.
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typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
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InstrPtrSet usingInstrs_;
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// The number of instructions using curli in each basic block.
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typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
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BlockCountMap usingBlocks_;
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// The number of basic block using curli in each loop.
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typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap;
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LoopCountMap usingLoops_;
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private:
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// Current live interval.
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const LiveInterval *curli_;
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// Sumarize statistics by counting instructions using curli_.
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void analyzeUses();
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/// canAnalyzeBranch - Return true if MBB ends in a branch that can be
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/// analyzed.
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bool canAnalyzeBranch(const MachineBasicBlock *MBB);
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public:
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SplitAnalysis(const MachineFunction &mf, 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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/// removeUse - Update statistics by noting that mi no longer uses curli.
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void removeUse(const MachineInstr *mi);
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const LiveInterval *getCurLI() { return curli_; }
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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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typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
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typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
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// Sets of basic blocks surrounding a machine loop.
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struct LoopBlocks {
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BlockPtrSet Loop; // Blocks in the loop.
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BlockPtrSet Preds; // Loop predecessor blocks.
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BlockPtrSet Exits; // Loop exit blocks.
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void clear() {
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Loop.clear();
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Preds.clear();
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Exits.clear();
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}
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};
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// Calculate the block sets surrounding the loop.
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void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks);
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/// LoopPeripheralUse - how is a variable used in and around a loop?
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/// Peripheral blocks are the loop predecessors and exit blocks.
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enum LoopPeripheralUse {
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ContainedInLoop, // All uses are inside the loop.
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SinglePeripheral, // At most one instruction per peripheral block.
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MultiPeripheral, // Multiple instructions in some peripheral blocks.
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OutsideLoop // Uses outside loop periphery.
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};
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/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
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/// and around the Loop.
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LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&);
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/// getCriticalExits - It may be necessary to partially break critical edges
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/// leaving the loop if an exit block has phi uses of curli. Collect the exit
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/// blocks that need special treatment into CriticalExits.
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void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits);
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/// canSplitCriticalExits - Return true if it is possible to insert new exit
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/// blocks before the blocks in CriticalExits.
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bool canSplitCriticalExits(const LoopBlocks &Blocks,
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BlockPtrSet &CriticalExits);
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/// getBestSplitLoop - Return the loop where curli may best be split to a
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/// separate register, or NULL.
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const MachineLoop *getBestSplitLoop();
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/// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
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/// having curli split to a new live interval. Return true if Blocks can be
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/// passed to SplitEditor::splitSingleBlocks.
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bool getMultiUseBlocks(BlockPtrSet &Blocks);
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/// getBlockForInsideSplit - If curli is contained inside a single basic block,
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/// and it wou pay to subdivide the interval inside that block, return it.
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/// Otherwise return NULL. The returned block can be passed to
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/// SplitEditor::splitInsideBlock.
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const MachineBasicBlock *getBlockForInsideSplit();
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};
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/// LiveIntervalMap - Map values from a large LiveInterval into a small
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/// interval that is a subset. Insert phi-def values as needed. This class is
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/// used by SplitEditor to create new smaller LiveIntervals.
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///
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/// parentli_ is the larger interval, li_ is the subset interval. Every value
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/// in li_ corresponds to exactly one value in parentli_, and the live range
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/// of the value is contained within the live range of the parentli_ value.
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/// Values in parentli_ may map to any number of openli_ values, including 0.
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class LiveIntervalMap {
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LiveIntervals &lis_;
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// The parent interval is never changed.
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const LiveInterval &parentli_;
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// The child interval's values are fully contained inside parentli_ values.
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LiveInterval &li_;
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typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
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// Map parentli_ values to simple values in li_ that are defined at the same
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// SlotIndex, or NULL for parentli_ values that have complex li_ defs.
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// Note there is a difference between values mapping to NULL (complex), and
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// values not present (unknown/unmapped).
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ValueMap valueMap_;
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// extendTo - Find the last li_ value defined in MBB at or before Idx. The
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// parentli_ is assumed to be live at Idx. Extend the live range to Idx.
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// Return the found VNInfo, or NULL.
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VNInfo *extendTo(MachineBasicBlock *MBB, SlotIndex Idx);
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// addSimpleRange - Add a simple range from parentli_ to li_.
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// ParentVNI must be live in the [Start;End) interval.
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void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
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public:
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LiveIntervalMap(LiveIntervals &lis,
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const LiveInterval &parentli,
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LiveInterval &li)
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: lis_(lis), parentli_(parentli), li_(li) {}
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/// defValue - define a value in li_ from the parentli_ value VNI and 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_.
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/// Return the new li_ value.
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VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
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/// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is
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/// assumed that ParentVNI is live at Idx.
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/// If ParentVNI has not been defined by defValue, it is assumed that
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/// ParentVNI->def dominates Idx.
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/// If ParentVNI has been defined by defValue one or more times, a value that
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/// dominates Idx will be returned. This may require creating extra phi-def
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/// values and adding live ranges to li_.
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VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx);
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/// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
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/// All needed values whose def is not inside [Start;End) must be defined
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/// beforehand so mapValue will work.
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void addRange(SlotIndex Start, SlotIndex End);
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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 rewrite().
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///
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class SplitEditor {
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SplitAnalysis &sa_;
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LiveIntervals &lis_;
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VirtRegMap &vrm_;
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MachineRegisterInfo &mri_;
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const TargetInstrInfo &tii_;
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/// curli_ - The immutable interval we are currently splitting.
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const LiveInterval *const curli_;
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/// dupli_ - Created as a copy of curli_, ranges are carved out as new
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/// intervals get added through openIntv / closeIntv. This is used to avoid
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/// editing curli_.
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LiveInterval *dupli_;
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/// Currently open LiveInterval.
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LiveInterval *openli_;
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/// createInterval - Create a new virtual register and LiveInterval with same
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/// register class and spill slot as curli.
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LiveInterval *createInterval();
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/// getDupLI - Ensure dupli is created and return it.
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LiveInterval *getDupLI();
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/// valueMap_ - Map values in cupli to values in openli. These are direct 1-1
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/// mappings, and do not include values created by inserted copies.
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DenseMap<const VNInfo*, VNInfo*> valueMap_;
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/// mapValue - Return the openIntv value that corresponds to the given curli
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/// value.
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VNInfo *mapValue(const VNInfo *curliVNI);
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/// A dupli value is live through openIntv.
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bool liveThrough_;
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/// All the new intervals created for this split are added to intervals_.
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SmallVectorImpl<LiveInterval*> &intervals_;
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/// The index into intervals_ of the first interval we added. There may be
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/// others from before we got it.
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unsigned firstInterval;
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/// Insert a COPY instruction curli -> li. Allocate a new value from li
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/// defined by the COPY
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VNInfo *insertCopy(LiveInterval &LI,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator I);
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public:
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/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
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/// Newly created intervals will be appended to newIntervals.
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SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
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SmallVectorImpl<LiveInterval*> &newIntervals);
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/// getAnalysis - Get the corresponding analysis.
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SplitAnalysis &getAnalysis() { return sa_; }
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/// Create a new virtual register and live interval.
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void openIntv();
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/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
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/// not live before Idx, a COPY is not inserted.
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void enterIntvBefore(SlotIndex Idx);
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/// enterIntvAtEnd - Enter openli at the end of MBB.
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/// PhiMBB is a successor inside openli where a PHI value is created.
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/// Currently, all entries must share the same PhiMBB.
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void enterIntvAtEnd(MachineBasicBlock &MBB, MachineBasicBlock &PhiMBB);
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/// useIntv - indicate that all instructions in MBB should use openli.
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void useIntv(const MachineBasicBlock &MBB);
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/// useIntv - indicate that all instructions in range should use openli.
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void useIntv(SlotIndex Start, SlotIndex End);
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/// leaveIntvAfter - Leave openli after the instruction at Idx.
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void leaveIntvAfter(SlotIndex Idx);
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/// leaveIntvAtTop - Leave the interval at the top of MBB.
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/// Currently, only one value can leave the interval.
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void leaveIntvAtTop(MachineBasicBlock &MBB);
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/// closeIntv - Indicate that we are done editing the currently open
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/// LiveInterval, and ranges can be trimmed.
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void closeIntv();
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/// rewrite - after all the new live ranges have been created, rewrite
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/// instructions using curli to use the new intervals.
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void rewrite();
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// ===--- High level methods ---===
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/// splitAroundLoop - Split curli into a separate live interval inside
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/// the loop. Return true if curli has been completely replaced, false if
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/// curli is still intact, and needs to be spilled or split further.
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bool splitAroundLoop(const MachineLoop*);
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/// splitSingleBlocks - Split curli into a separate live interval inside each
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/// basic block in Blocks. Return true if curli has been completely replaced,
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/// false if curli is still intact, and needs to be spilled or split further.
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bool splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
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/// splitInsideBlock - Split curli into multiple intervals inside MBB. Return
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/// true if curli has been completely replaced, false if curli is still
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/// intact, and needs to be spilled or split further.
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bool splitInsideBlock(const MachineBasicBlock *);
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};
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}
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