1 //===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the SplitAnalysis class as well as mutator functions for
11 // live range splitting.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/CodeGen/SlotIndexes.h"
25 class MachineLoopInfo;
26 class MachineRegisterInfo;
27 class TargetInstrInfo;
31 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
35 const MachineFunction &mf_;
36 const LiveIntervals &lis_;
37 const MachineLoopInfo &loops_;
38 const TargetInstrInfo &tii_;
40 // Instructions using the the current register.
41 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
42 InstrPtrSet usingInstrs_;
44 // The number of instructions using curli in each basic block.
45 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
46 BlockCountMap usingBlocks_;
48 // The number of basic block using curli in each loop.
49 typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap;
50 LoopCountMap usingLoops_;
53 // Current live interval.
54 const LiveInterval *curli_;
56 // Sumarize statistics by counting instructions using curli_.
59 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be
61 bool canAnalyzeBranch(const MachineBasicBlock *MBB);
64 SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis,
65 const MachineLoopInfo &mli);
67 /// analyze - set curli to the specified interval, and analyze how it may be
69 void analyze(const LiveInterval *li);
71 /// removeUse - Update statistics by noting that mi no longer uses curli.
72 void removeUse(const MachineInstr *mi);
74 const LiveInterval *getCurLI() { return curli_; }
76 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
80 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
81 typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
83 // Sets of basic blocks surrounding a machine loop.
85 BlockPtrSet Loop; // Blocks in the loop.
86 BlockPtrSet Preds; // Loop predecessor blocks.
87 BlockPtrSet Exits; // Loop exit blocks.
96 // Calculate the block sets surrounding the loop.
97 void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks);
99 /// LoopPeripheralUse - how is a variable used in and around a loop?
100 /// Peripheral blocks are the loop predecessors and exit blocks.
101 enum LoopPeripheralUse {
102 ContainedInLoop, // All uses are inside the loop.
103 SinglePeripheral, // At most one instruction per peripheral block.
104 MultiPeripheral, // Multiple instructions in some peripheral blocks.
105 OutsideLoop // Uses outside loop periphery.
108 /// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
109 /// and around the Loop.
110 LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&);
112 /// getCriticalExits - It may be necessary to partially break critical edges
113 /// leaving the loop if an exit block has phi uses of curli. Collect the exit
114 /// blocks that need special treatment into CriticalExits.
115 void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits);
117 /// canSplitCriticalExits - Return true if it is possible to insert new exit
118 /// blocks before the blocks in CriticalExits.
119 bool canSplitCriticalExits(const LoopBlocks &Blocks,
120 BlockPtrSet &CriticalExits);
122 /// getBestSplitLoop - Return the loop where curli may best be split to a
123 /// separate register, or NULL.
124 const MachineLoop *getBestSplitLoop();
126 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
127 /// having curli split to a new live interval. Return true if Blocks can be
128 /// passed to SplitEditor::splitSingleBlocks.
129 bool getMultiUseBlocks(BlockPtrSet &Blocks);
131 /// getBlockForInsideSplit - If curli is contained inside a single basic block,
132 /// and it wou pay to subdivide the interval inside that block, return it.
133 /// Otherwise return NULL. The returned block can be passed to
134 /// SplitEditor::splitInsideBlock.
135 const MachineBasicBlock *getBlockForInsideSplit();
138 /// SplitEditor - Edit machine code and LiveIntervals for live range
141 /// - Create a SplitEditor from a SplitAnalysis.
142 /// - Start a new live interval with openIntv.
143 /// - Mark the places where the new interval is entered using enterIntv*
144 /// - Mark the ranges where the new interval is used with useIntv*
145 /// - Mark the places where the interval is exited with exitIntv*.
146 /// - Finish the current interval with closeIntv and repeat from 2.
147 /// - Rewrite instructions with rewrite().
153 MachineRegisterInfo &mri_;
154 const TargetInstrInfo &tii_;
156 /// curli_ - The immutable interval we are currently splitting.
157 const LiveInterval *const curli_;
159 /// dupli_ - Created as a copy of curli_, ranges are carved out as new
160 /// intervals get added through openIntv / closeIntv. This is used to avoid
162 LiveInterval *dupli_;
164 /// Currently open LiveInterval.
165 LiveInterval *openli_;
167 /// createInterval - Create a new virtual register and LiveInterval with same
168 /// register class and spill slot as curli.
169 LiveInterval *createInterval();
171 /// getDupLI - Ensure dupli is created and return it.
172 LiveInterval *getDupLI();
174 /// valueMap_ - Map values in cupli to values in openli. These are direct 1-1
175 /// mappings, and do not include values created by inserted copies.
176 DenseMap<const VNInfo*, VNInfo*> valueMap_;
178 /// mapValue - Return the openIntv value that corresponds to the given curli
180 VNInfo *mapValue(const VNInfo *curliVNI);
182 /// A dupli value is live through openIntv.
185 /// All the new intervals created for this split are added to intervals_.
186 std::vector<LiveInterval*> &intervals_;
188 /// The index into intervals_ of the first interval we added. There may be
189 /// others from before we got it.
190 unsigned firstInterval;
192 /// Insert a COPY instruction curli -> li. Allocate a new value from li
193 /// defined by the COPY
194 VNInfo *insertCopy(LiveInterval &LI,
195 MachineBasicBlock &MBB,
196 MachineBasicBlock::iterator I);
199 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
200 /// Newly created intervals will be appended to newIntervals.
201 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
202 std::vector<LiveInterval*> &newIntervals);
204 /// getAnalysis - Get the corresponding analysis.
205 SplitAnalysis &getAnalysis() { return sa_; }
207 /// Create a new virtual register and live interval.
210 /// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
211 /// not live before Idx, a COPY is not inserted.
212 void enterIntvBefore(SlotIndex Idx);
214 /// enterIntvAtEnd - Enter openli at the end of MBB.
215 /// PhiMBB is a successor inside openli where a PHI value is created.
216 /// Currently, all entries must share the same PhiMBB.
217 void enterIntvAtEnd(MachineBasicBlock &MBB, MachineBasicBlock &PhiMBB);
219 /// useIntv - indicate that all instructions in MBB should use openli.
220 void useIntv(const MachineBasicBlock &MBB);
222 /// useIntv - indicate that all instructions in range should use openli.
223 void useIntv(SlotIndex Start, SlotIndex End);
225 /// leaveIntvAfter - Leave openli after the instruction at Idx.
226 void leaveIntvAfter(SlotIndex Idx);
228 /// leaveIntvAtTop - Leave the interval at the top of MBB.
229 /// Currently, only one value can leave the interval.
230 void leaveIntvAtTop(MachineBasicBlock &MBB);
232 /// closeIntv - Indicate that we are done editing the currently open
233 /// LiveInterval, and ranges can be trimmed.
236 /// rewrite - after all the new live ranges have been created, rewrite
237 /// instructions using curli to use the new intervals.
240 // ===--- High level methods ---===
242 /// splitAroundLoop - Split curli into a separate live interval inside
243 /// the loop. Return true if curli has been completely replaced, false if
244 /// curli is still intact, and needs to be spilled or split further.
245 bool splitAroundLoop(const MachineLoop*);
247 /// splitSingleBlocks - Split curli into a separate live interval inside each
248 /// basic block in Blocks. Return true if curli has been completely replaced,
249 /// false if curli is still intact, and needs to be spilled or split further.
250 bool splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
252 /// splitInsideBlock - Split curli into multiple intervals inside MBB. Return
253 /// true if curli has been completely replaced, false if curli is still
254 /// intact, and needs to be spilled or split further.
255 bool splitInsideBlock(const MachineBasicBlock *);