1 //===-------- SplitKit.cpp - Toolkit for splitting live ranges --*- C++ -*-===//
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"
26 class MachineLoopInfo;
27 class MachineRegisterInfo;
28 class TargetInstrInfo;
29 class TargetRegisterInfo;
34 /// At some point we should just include MachineDominators.h:
35 class MachineDominatorTree;
36 template <class NodeT> class DomTreeNodeBase;
37 typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
39 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
43 const MachineFunction &mf_;
44 const LiveIntervals &lis_;
45 const MachineLoopInfo &loops_;
46 const TargetInstrInfo &tii_;
48 // Instructions using the the current register.
49 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
50 InstrPtrSet usingInstrs_;
52 // The number of instructions using curli in each basic block.
53 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
54 BlockCountMap usingBlocks_;
56 // The number of basic block using curli in each loop.
57 typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap;
58 LoopCountMap usingLoops_;
61 // Current live interval.
62 const LiveInterval *curli_;
64 // Sumarize statistics by counting instructions using curli_.
67 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be
69 bool canAnalyzeBranch(const MachineBasicBlock *MBB);
72 SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis,
73 const MachineLoopInfo &mli);
75 /// analyze - set curli to the specified interval, and analyze how it may be
77 void analyze(const LiveInterval *li);
79 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
83 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
84 typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
86 // Print a set of blocks with use counts.
87 void print(const BlockPtrSet&, raw_ostream&) const;
89 // Sets of basic blocks surrounding a machine loop.
91 BlockPtrSet Loop; // Blocks in the loop.
92 BlockPtrSet Preds; // Loop predecessor blocks.
93 BlockPtrSet Exits; // Loop exit blocks.
102 // Print loop blocks with use counts.
103 void print(const LoopBlocks&, raw_ostream&) const;
105 // Calculate the block sets surrounding the loop.
106 void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks);
108 /// LoopPeripheralUse - how is a variable used in and around a loop?
109 /// Peripheral blocks are the loop predecessors and exit blocks.
110 enum LoopPeripheralUse {
111 ContainedInLoop, // All uses are inside the loop.
112 SinglePeripheral, // At most one instruction per peripheral block.
113 MultiPeripheral, // Multiple instructions in some peripheral blocks.
114 OutsideLoop // Uses outside loop periphery.
117 /// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
118 /// and around the Loop.
119 LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&);
121 /// getCriticalExits - It may be necessary to partially break critical edges
122 /// leaving the loop if an exit block has phi uses of curli. Collect the exit
123 /// blocks that need special treatment into CriticalExits.
124 void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits);
126 /// canSplitCriticalExits - Return true if it is possible to insert new exit
127 /// blocks before the blocks in CriticalExits.
128 bool canSplitCriticalExits(const LoopBlocks &Blocks,
129 BlockPtrSet &CriticalExits);
131 /// getCriticalPreds - Get the set of loop predecessors with critical edges to
132 /// blocks outside the loop that have curli live in. We don't have to break
133 /// these edges, but they do require special treatment.
134 void getCriticalPreds(const LoopBlocks &Blocks, BlockPtrSet &CriticalPreds);
136 /// getSplitLoops - Get the set of loops that have curli uses and would be
137 /// profitable to split.
138 void getSplitLoops(LoopPtrSet&);
140 /// getBestSplitLoop - Return the loop where curli may best be split to a
141 /// separate register, or NULL.
142 const MachineLoop *getBestSplitLoop();
144 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
145 /// having curli split to a new live interval. Return true if Blocks can be
146 /// passed to SplitEditor::splitSingleBlocks.
147 bool getMultiUseBlocks(BlockPtrSet &Blocks);
149 /// getBlockForInsideSplit - If curli is contained inside a single basic block,
150 /// and it wou pay to subdivide the interval inside that block, return it.
151 /// Otherwise return NULL. The returned block can be passed to
152 /// SplitEditor::splitInsideBlock.
153 const MachineBasicBlock *getBlockForInsideSplit();
157 /// LiveIntervalMap - Map values from a large LiveInterval into a small
158 /// interval that is a subset. Insert phi-def values as needed. This class is
159 /// used by SplitEditor to create new smaller LiveIntervals.
161 /// parentli_ is the larger interval, li_ is the subset interval. Every value
162 /// in li_ corresponds to exactly one value in parentli_, and the live range
163 /// of the value is contained within the live range of the parentli_ value.
164 /// Values in parentli_ may map to any number of openli_ values, including 0.
165 class LiveIntervalMap {
167 MachineDominatorTree &mdt_;
169 // The parent interval is never changed.
170 const LiveInterval &parentli_;
172 // The child interval's values are fully contained inside parentli_ values.
175 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
177 // Map parentli_ values to simple values in li_ that are defined at the same
178 // SlotIndex, or NULL for parentli_ values that have complex li_ defs.
179 // Note there is a difference between values mapping to NULL (complex), and
180 // values not present (unknown/unmapped).
183 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
184 typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap;
186 // liveOutCache_ - Map each basic block where li_ is live out to the live-out
187 // value and its defining block. One of these conditions shall be true:
189 // 1. !liveOutCache_.count(MBB)
190 // 2. liveOutCache_[MBB].second.getNode() == MBB
191 // 3. forall P in preds(MBB): liveOutCache_[P] == liveOutCache_[MBB]
193 // This is only a cache, the values can be computed as:
195 // VNI = li_->getVNInfoAt(lis_.getMBBEndIdx(MBB))
196 // Node = mbt_[lis_.getMBBFromIndex(VNI->def)]
198 // The cache is also used as a visiteed set by mapValue().
199 LiveOutMap liveOutCache_;
202 LiveIntervalMap(LiveIntervals &lis,
203 MachineDominatorTree &mdt,
204 const LiveInterval &parentli)
205 : lis_(lis), mdt_(mdt), parentli_(parentli), li_(0) {}
207 /// reset - clear all data structures and start a new live interval.
208 void reset(LiveInterval *);
210 /// getLI - return the current live interval.
211 LiveInterval *getLI() const { return li_; }
213 /// defValue - define a value in li_ from the parentli_ value VNI and Idx.
214 /// Idx does not have to be ParentVNI->def, but it must be contained within
215 /// ParentVNI's live range in parentli_.
216 /// Return the new li_ value.
217 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
219 /// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is
220 /// assumed that ParentVNI is live at Idx.
221 /// If ParentVNI has not been defined by defValue, it is assumed that
222 /// ParentVNI->def dominates Idx.
223 /// If ParentVNI has been defined by defValue one or more times, a value that
224 /// dominates Idx will be returned. This may require creating extra phi-def
225 /// values and adding live ranges to li_.
226 /// If simple is not NULL, *simple will indicate if ParentVNI is a simply
228 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0);
230 // extendTo - Find the last li_ value defined in MBB at or before Idx. The
231 // parentli is assumed to be live at Idx. Extend the live range to include
232 // Idx. Return the found VNInfo, or NULL.
233 VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx);
235 /// isMapped - Return true is ParentVNI is a known mapped value. It may be a
236 /// simple 1-1 mapping or a complex mapping to later defs.
237 bool isMapped(const VNInfo *ParentVNI) const {
238 return valueMap_.count(ParentVNI);
241 /// isComplexMapped - Return true if ParentVNI has received new definitions
243 bool isComplexMapped(const VNInfo *ParentVNI) const;
245 // addSimpleRange - Add a simple range from parentli_ to li_.
246 // ParentVNI must be live in the [Start;End) interval.
247 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
249 /// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
250 /// All needed values whose def is not inside [Start;End) must be defined
251 /// beforehand so mapValue will work.
252 void addRange(SlotIndex Start, SlotIndex End);
256 /// SplitEditor - Edit machine code and LiveIntervals for live range
259 /// - Create a SplitEditor from a SplitAnalysis.
260 /// - Start a new live interval with openIntv.
261 /// - Mark the places where the new interval is entered using enterIntv*
262 /// - Mark the ranges where the new interval is used with useIntv*
263 /// - Mark the places where the interval is exited with exitIntv*.
264 /// - Finish the current interval with closeIntv and repeat from 2.
265 /// - Rewrite instructions with finish().
271 MachineRegisterInfo &mri_;
272 const TargetInstrInfo &tii_;
273 const TargetRegisterInfo &tri_;
275 /// edit_ - The current parent register and new intervals created.
276 LiveRangeEdit &edit_;
278 /// dupli_ - Created as a copy of curli_, ranges are carved out as new
279 /// intervals get added through openIntv / closeIntv. This is used to avoid
281 LiveIntervalMap dupli_;
283 /// Currently open LiveInterval.
284 LiveIntervalMap openli_;
286 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
287 /// rematerialization or a COPY from parent. Return the new value.
288 VNInfo *defFromParent(LiveIntervalMap &Reg,
291 MachineBasicBlock &MBB,
292 MachineBasicBlock::iterator I);
294 /// intervalsLiveAt - Return true if any member of intervals_ is live at Idx.
295 bool intervalsLiveAt(SlotIndex Idx) const;
297 /// Values in curli whose live range has been truncated when entering an open
299 SmallPtrSet<const VNInfo*, 8> truncatedValues;
301 /// addTruncSimpleRange - Add the given simple range to dupli_ after
302 /// truncating any overlap with intervals_.
303 void addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI);
305 /// criticalPreds_ - Set of basic blocks where both dupli and openli should be
306 /// live out because of a critical edge.
307 SplitAnalysis::BlockPtrSet criticalPreds_;
309 /// computeRemainder - Compute the dupli liveness as the complement of all the
311 void computeRemainder();
313 /// rewrite - Rewrite all uses of reg to use the new registers.
314 void rewrite(unsigned reg);
317 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
318 /// Newly created intervals will be appended to newIntervals.
319 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
320 MachineDominatorTree&, LiveRangeEdit&);
322 /// getAnalysis - Get the corresponding analysis.
323 SplitAnalysis &getAnalysis() { return sa_; }
325 /// Create a new virtual register and live interval.
328 /// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
329 /// not live before Idx, a COPY is not inserted.
330 void enterIntvBefore(SlotIndex Idx);
332 /// enterIntvAtEnd - Enter openli at the end of MBB.
333 void enterIntvAtEnd(MachineBasicBlock &MBB);
335 /// useIntv - indicate that all instructions in MBB should use openli.
336 void useIntv(const MachineBasicBlock &MBB);
338 /// useIntv - indicate that all instructions in range should use openli.
339 void useIntv(SlotIndex Start, SlotIndex End);
341 /// leaveIntvAfter - Leave openli after the instruction at Idx.
342 void leaveIntvAfter(SlotIndex Idx);
344 /// leaveIntvAtTop - Leave the interval at the top of MBB.
345 /// Currently, only one value can leave the interval.
346 void leaveIntvAtTop(MachineBasicBlock &MBB);
348 /// closeIntv - Indicate that we are done editing the currently open
349 /// LiveInterval, and ranges can be trimmed.
352 /// finish - after all the new live ranges have been created, compute the
353 /// remaining live range, and rewrite instructions to use the new registers.
356 // ===--- High level methods ---===
358 /// splitAroundLoop - Split curli into a separate live interval inside
360 void splitAroundLoop(const MachineLoop*);
362 /// splitSingleBlocks - Split curli into a separate live interval inside each
363 /// basic block in Blocks.
364 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
366 /// splitInsideBlock - Split curli into multiple intervals inside MBB.
367 void splitInsideBlock(const MachineBasicBlock *);