SplitKit.h revision f0179004e94259a8adab6c48f295ea9ab18af4c3
1//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file contains the SplitAnalysis class as well as mutator functions for 11// live range splitting. 12// 13//===----------------------------------------------------------------------===// 14 15#include "llvm/ADT/SmallPtrSet.h" 16#include "llvm/ADT/DenseMap.h" 17#include "llvm/CodeGen/SlotIndexes.h" 18 19namespace llvm { 20 21class LiveInterval; 22class LiveIntervals; 23class MachineInstr; 24class MachineLoop; 25class MachineLoopInfo; 26class MachineRegisterInfo; 27class TargetInstrInfo; 28class VirtRegMap; 29class VNInfo; 30 31/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting 32/// opportunities. 33class SplitAnalysis { 34 const MachineFunction &mf_; 35 const LiveIntervals &lis_; 36 const MachineLoopInfo &loops_; 37 const TargetInstrInfo &tii_; 38 39 // Current live interval. 40 const LiveInterval *curli_; 41 42 // Instructions using the the current register. 43 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet; 44 InstrPtrSet usingInstrs_; 45 46 // The number of instructions using curli in each basic block. 47 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap; 48 BlockCountMap usingBlocks_; 49 50 // Loops where the curent interval is used. 51 typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet; 52 LoopPtrSet usingLoops_; 53 54 // Sumarize statistics by counting instructions using curli_. 55 void analyzeUses(); 56 57 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be 58 /// analyzed. 59 bool canAnalyzeBranch(const MachineBasicBlock *MBB); 60 61public: 62 SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis, 63 const MachineLoopInfo &mli); 64 65 /// analyze - set curli to the specified interval, and analyze how it may be 66 /// split. 67 void analyze(const LiveInterval *li); 68 69 const LiveInterval *getCurLI() { return curli_; } 70 71 /// clear - clear all data structures so SplitAnalysis is ready to analyze a 72 /// new interval. 73 void clear(); 74 75 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; 76 77 // Sets of basic blocks surrounding a machine loop. 78 struct LoopBlocks { 79 BlockPtrSet Loop; // Blocks in the loop. 80 BlockPtrSet Preds; // Loop predecessor blocks. 81 BlockPtrSet Exits; // Loop exit blocks. 82 83 void clear() { 84 Loop.clear(); 85 Preds.clear(); 86 Exits.clear(); 87 } 88 }; 89 90 // Calculate the block sets surrounding the loop. 91 void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks); 92 93 /// LoopPeripheralUse - how is a variable used in and around a loop? 94 /// Peripheral blocks are the loop predecessors and exit blocks. 95 enum LoopPeripheralUse { 96 ContainedInLoop, // All uses are inside the loop. 97 SinglePeripheral, // At most one instruction per peripheral block. 98 MultiPeripheral, // Multiple instructions in some peripheral blocks. 99 OutsideLoop // Uses outside loop periphery. 100 }; 101 102 /// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in 103 /// and around the Loop. 104 LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&); 105 106 /// getCriticalExits - It may be necessary to partially break critical edges 107 /// leaving the loop if an exit block has phi uses of curli. Collect the exit 108 /// blocks that need special treatment into CriticalExits. 109 void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits); 110 111 /// canSplitCriticalExits - Return true if it is possible to insert new exit 112 /// blocks before the blocks in CriticalExits. 113 bool canSplitCriticalExits(const LoopBlocks &Blocks, 114 BlockPtrSet &CriticalExits); 115 116 /// getBestSplitLoop - Return the loop where curli may best be split to a 117 /// separate register, or NULL. 118 const MachineLoop *getBestSplitLoop(); 119}; 120 121/// SplitEditor - Edit machine code and LiveIntervals for live range 122/// splitting. 123/// 124/// 1. Create a SplitEditor from a SplitAnalysis. This will create a new 125/// LiveInterval, dupli, that is identical to SA.curli. 126/// 2. Start a new live interval with openLI. 127/// 3. Insert copies to the new interval with copyTo* and mark the ranges where 128/// it should be used with use*. 129/// 4. Insert back-copies with copyFromLI. 130/// 5. Finish the current LI with closeLI and repeat from 2. 131/// 6. Rewrite instructions with rewrite(). 132/// 133class SplitEditor { 134 SplitAnalysis &sa_; 135 LiveIntervals &lis_; 136 VirtRegMap &vrm_; 137 MachineRegisterInfo &mri_; 138 const TargetInstrInfo &tii_; 139 140 /// dupli_ - Created as a copy of sa_.curli_, ranges are carved out as new 141 /// intervals get added through openLI / closeLI. 142 LiveInterval *dupli_; 143 144 /// Currently open LiveInterval. 145 LiveInterval *openli_; 146 147 /// createInterval - Create a new virtual register and LiveInterval with same 148 /// register class and spill slot as curli. 149 LiveInterval *createInterval(); 150 151 /// valueMap_ - Map values in dupli to values in openli. These are direct 1-1 152 /// mappings, and do not include values created by inserted copies. 153 DenseMap<VNInfo*,VNInfo*> valueMap_; 154 155 /// mapValue - Return the openli value that corresponds to the given dupli 156 /// value. 157 VNInfo *mapValue(VNInfo *dupliVNI); 158 159public: 160 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA. 161 SplitEditor(SplitAnalysis&, LiveIntervals&, VirtRegMap&); 162 163 /// getAnalysis - Get the corresponding analysis. 164 SplitAnalysis &getAnalysis() { return sa_; } 165 166 /// Create a new virtual register and live interval to be used by following 167 /// use* and copy* calls. 168 void openLI(); 169 170 /// copyToPHI - Insert a copy to openli at the end of A, and catch it with a 171 /// PHI def at the beginning of the successor B. This call is ignored if dupli 172 /// is not live out of A. 173 void copyToPHI(MachineBasicBlock &A, MachineBasicBlock &B); 174 175 /// useLI - indicate that all instructions in MBB should use openli. 176 void useLI(const MachineBasicBlock &MBB); 177 178 /// useLI - indicate that all instructions in range should use openli. 179 void useLI(SlotIndex Start, SlotIndex End); 180 181 /// copyFromLI - Insert a copy back to dupli from openli at position I. 182 /// This also marks the remainder of MBB as not used by openli. 183 SlotIndex copyFromLI(MachineBasicBlock &MBB, MachineBasicBlock::iterator I); 184 185 /// closeLI - Indicate that we are done editing the currently open 186 /// LiveInterval, and ranges can be trimmed. 187 void closeLI(); 188 189 /// rewrite - after all the new live ranges have been created, rewrite 190 /// instructions using curli to use the new intervals. 191 void rewrite(); 192 193 // ===--- High level methods ---=== 194 195 /// splitAroundLoop - Split curli into a separate live interval inside 196 /// the loop. 197 void splitAroundLoop(const MachineLoop*); 198 199}; 200 201 202} 203