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();
139 /// LiveIntervalMap - Map values from a large LiveInterval into a small
140 /// interval that is a subset. Insert phi-def values as needed. This class is
141 /// used by SplitEditor to create new smaller LiveIntervals.
143 /// parentli_ is the larger interval, li_ is the subset interval. Every value
144 /// in li_ corresponds to exactly one value in parentli_, and the live range
145 /// of the value is contained within the live range of the parentli_ value.
146 /// Values in parentli_ may map to any number of openli_ values, including 0.
147 class LiveIntervalMap {
150 // The parent interval is never changed.
151 const LiveInterval &parentli_;
153 // The child interval's values are fully contained inside parentli_ values.
156 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
158 // Map parentli_ values to simple values in li_ that are defined at the same
159 // SlotIndex, or NULL for parentli_ values that have complex li_ defs.
160 // Note there is a difference between values mapping to NULL (complex), and
161 // values not present (unknown/unmapped).
164 // extendTo - Find the last li_ value defined in MBB at or before Idx. The
165 // parentli_ is assumed to be live at Idx. Extend the live range to Idx.
166 // Return the found VNInfo, or NULL.
167 VNInfo *extendTo(MachineBasicBlock *MBB, SlotIndex Idx);
169 // addSimpleRange - Add a simple range from parentli_ to li_.
170 // ParentVNI must be live in the [Start;End) interval.
171 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
174 LiveIntervalMap(LiveIntervals &lis,
175 const LiveInterval &parentli,
177 : lis_(lis), parentli_(parentli), li_(li) {}
179 /// defValue - define a value in li_ from the parentli_ value VNI and Idx.
180 /// Idx does not have to be ParentVNI->def, but it must be contained within
181 /// ParentVNI's live range in parentli_.
182 /// Return the new li_ value.
183 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
185 /// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is
186 /// assumed that ParentVNI is live at Idx.
187 /// If ParentVNI has not been defined by defValue, it is assumed that
188 /// ParentVNI->def dominates Idx.
189 /// If ParentVNI has been defined by defValue one or more times, a value that
190 /// dominates Idx will be returned. This may require creating extra phi-def
191 /// values and adding live ranges to li_.
192 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx);
194 /// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
195 /// All needed values whose def is not inside [Start;End) must be defined
196 /// beforehand so mapValue will work.
197 void addRange(SlotIndex Start, SlotIndex End);
201 /// SplitEditor - Edit machine code and LiveIntervals for live range
204 /// - Create a SplitEditor from a SplitAnalysis.
205 /// - Start a new live interval with openIntv.
206 /// - Mark the places where the new interval is entered using enterIntv*
207 /// - Mark the ranges where the new interval is used with useIntv*
208 /// - Mark the places where the interval is exited with exitIntv*.
209 /// - Finish the current interval with closeIntv and repeat from 2.
210 /// - Rewrite instructions with rewrite().
216 MachineRegisterInfo &mri_;
217 const TargetInstrInfo &tii_;
219 /// curli_ - The immutable interval we are currently splitting.
220 const LiveInterval *const curli_;
222 /// dupli_ - Created as a copy of curli_, ranges are carved out as new
223 /// intervals get added through openIntv / closeIntv. This is used to avoid
225 LiveInterval *dupli_;
227 /// Currently open LiveInterval.
228 LiveInterval *openli_;
230 /// createInterval - Create a new virtual register and LiveInterval with same
231 /// register class and spill slot as curli.
232 LiveInterval *createInterval();
234 /// getDupLI - Ensure dupli is created and return it.
235 LiveInterval *getDupLI();
237 /// valueMap_ - Map values in cupli to values in openli. These are direct 1-1
238 /// mappings, and do not include values created by inserted copies.
239 DenseMap<const VNInfo*, VNInfo*> valueMap_;
241 /// mapValue - Return the openIntv value that corresponds to the given curli
243 VNInfo *mapValue(const VNInfo *curliVNI);
245 /// A dupli value is live through openIntv.
248 /// All the new intervals created for this split are added to intervals_.
249 SmallVectorImpl<LiveInterval*> &intervals_;
251 /// The index into intervals_ of the first interval we added. There may be
252 /// others from before we got it.
253 unsigned firstInterval;
255 /// Insert a COPY instruction curli -> li. Allocate a new value from li
256 /// defined by the COPY
257 VNInfo *insertCopy(LiveInterval &LI,
258 MachineBasicBlock &MBB,
259 MachineBasicBlock::iterator I);
262 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
263 /// Newly created intervals will be appended to newIntervals.
264 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
265 SmallVectorImpl<LiveInterval*> &newIntervals);
267 /// getAnalysis - Get the corresponding analysis.
268 SplitAnalysis &getAnalysis() { return sa_; }
270 /// Create a new virtual register and live interval.
273 /// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
274 /// not live before Idx, a COPY is not inserted.
275 void enterIntvBefore(SlotIndex Idx);
277 /// enterIntvAtEnd - Enter openli at the end of MBB.
278 /// PhiMBB is a successor inside openli where a PHI value is created.
279 /// Currently, all entries must share the same PhiMBB.
280 void enterIntvAtEnd(MachineBasicBlock &MBB, MachineBasicBlock &PhiMBB);
282 /// useIntv - indicate that all instructions in MBB should use openli.
283 void useIntv(const MachineBasicBlock &MBB);
285 /// useIntv - indicate that all instructions in range should use openli.
286 void useIntv(SlotIndex Start, SlotIndex End);
288 /// leaveIntvAfter - Leave openli after the instruction at Idx.
289 void leaveIntvAfter(SlotIndex Idx);
291 /// leaveIntvAtTop - Leave the interval at the top of MBB.
292 /// Currently, only one value can leave the interval.
293 void leaveIntvAtTop(MachineBasicBlock &MBB);
295 /// closeIntv - Indicate that we are done editing the currently open
296 /// LiveInterval, and ranges can be trimmed.
299 /// rewrite - after all the new live ranges have been created, rewrite
300 /// instructions using curli to use the new intervals.
303 // ===--- High level methods ---===
305 /// splitAroundLoop - Split curli into a separate live interval inside
306 /// the loop. Return true if curli has been completely replaced, false if
307 /// curli is still intact, and needs to be spilled or split further.
308 bool splitAroundLoop(const MachineLoop*);
310 /// splitSingleBlocks - Split curli into a separate live interval inside each
311 /// basic block in Blocks. Return true if curli has been completely replaced,
312 /// false if curli is still intact, and needs to be spilled or split further.
313 bool splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
315 /// splitInsideBlock - Split curli into multiple intervals inside MBB. Return
316 /// true if curli has been completely replaced, false if curli is still
317 /// intact, and needs to be spilled or split further.
318 bool splitInsideBlock(const MachineBasicBlock *);