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 /// isBypassLoop - Return true if curli is live through Loop and has no uses
145 /// inside the loop. Bypass loops are candidates for splitting because it can
146 /// prevent interference inside the loop.
147 bool isBypassLoop(const MachineLoop *Loop);
149 /// getBypassLoops - Get all the maximal bypass loops. These are the bypass
150 /// loops whose parent is not a bypass loop.
151 void getBypassLoops(LoopPtrSet&);
153 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
154 /// having curli split to a new live interval. Return true if Blocks can be
155 /// passed to SplitEditor::splitSingleBlocks.
156 bool getMultiUseBlocks(BlockPtrSet &Blocks);
158 /// getBlockForInsideSplit - If curli is contained inside a single basic block,
159 /// and it wou pay to subdivide the interval inside that block, return it.
160 /// Otherwise return NULL. The returned block can be passed to
161 /// SplitEditor::splitInsideBlock.
162 const MachineBasicBlock *getBlockForInsideSplit();
166 /// LiveIntervalMap - Map values from a large LiveInterval into a small
167 /// interval that is a subset. Insert phi-def values as needed. This class is
168 /// used by SplitEditor to create new smaller LiveIntervals.
170 /// parentli_ is the larger interval, li_ is the subset interval. Every value
171 /// in li_ corresponds to exactly one value in parentli_, and the live range
172 /// of the value is contained within the live range of the parentli_ value.
173 /// Values in parentli_ may map to any number of openli_ values, including 0.
174 class LiveIntervalMap {
176 MachineDominatorTree &mdt_;
178 // The parent interval is never changed.
179 const LiveInterval &parentli_;
181 // The child interval's values are fully contained inside parentli_ values.
184 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
186 // Map parentli_ values to simple values in li_ that are defined at the same
187 // SlotIndex, or NULL for parentli_ values that have complex li_ defs.
188 // Note there is a difference between values mapping to NULL (complex), and
189 // values not present (unknown/unmapped).
192 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
193 typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap;
195 // liveOutCache_ - Map each basic block where li_ is live out to the live-out
196 // value and its defining block. One of these conditions shall be true:
198 // 1. !liveOutCache_.count(MBB)
199 // 2. liveOutCache_[MBB].second.getNode() == MBB
200 // 3. forall P in preds(MBB): liveOutCache_[P] == liveOutCache_[MBB]
202 // This is only a cache, the values can be computed as:
204 // VNI = li_->getVNInfoAt(lis_.getMBBEndIdx(MBB))
205 // Node = mbt_[lis_.getMBBFromIndex(VNI->def)]
207 // The cache is also used as a visiteed set by mapValue().
208 LiveOutMap liveOutCache_;
211 LiveIntervalMap(LiveIntervals &lis,
212 MachineDominatorTree &mdt,
213 const LiveInterval &parentli)
214 : lis_(lis), mdt_(mdt), parentli_(parentli), li_(0) {}
216 /// reset - clear all data structures and start a new live interval.
217 void reset(LiveInterval *);
219 /// getLI - return the current live interval.
220 LiveInterval *getLI() const { return li_; }
222 /// defValue - define a value in li_ from the parentli_ value VNI and Idx.
223 /// Idx does not have to be ParentVNI->def, but it must be contained within
224 /// ParentVNI's live range in parentli_.
225 /// Return the new li_ value.
226 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
228 /// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is
229 /// assumed that ParentVNI is live at Idx.
230 /// If ParentVNI has not been defined by defValue, it is assumed that
231 /// ParentVNI->def dominates Idx.
232 /// If ParentVNI has been defined by defValue one or more times, a value that
233 /// dominates Idx will be returned. This may require creating extra phi-def
234 /// values and adding live ranges to li_.
235 /// If simple is not NULL, *simple will indicate if ParentVNI is a simply
237 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0);
239 // extendTo - Find the last li_ value defined in MBB at or before Idx. The
240 // parentli is assumed to be live at Idx. Extend the live range to include
241 // Idx. Return the found VNInfo, or NULL.
242 VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx);
244 /// isMapped - Return true is ParentVNI is a known mapped value. It may be a
245 /// simple 1-1 mapping or a complex mapping to later defs.
246 bool isMapped(const VNInfo *ParentVNI) const {
247 return valueMap_.count(ParentVNI);
250 /// isComplexMapped - Return true if ParentVNI has received new definitions
252 bool isComplexMapped(const VNInfo *ParentVNI) const;
254 // addSimpleRange - Add a simple range from parentli_ to li_.
255 // ParentVNI must be live in the [Start;End) interval.
256 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
258 /// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
259 /// All needed values whose def is not inside [Start;End) must be defined
260 /// beforehand so mapValue will work.
261 void addRange(SlotIndex Start, SlotIndex End);
265 /// SplitEditor - Edit machine code and LiveIntervals for live range
268 /// - Create a SplitEditor from a SplitAnalysis.
269 /// - Start a new live interval with openIntv.
270 /// - Mark the places where the new interval is entered using enterIntv*
271 /// - Mark the ranges where the new interval is used with useIntv*
272 /// - Mark the places where the interval is exited with exitIntv*.
273 /// - Finish the current interval with closeIntv and repeat from 2.
274 /// - Rewrite instructions with finish().
280 MachineRegisterInfo &mri_;
281 const TargetInstrInfo &tii_;
282 const TargetRegisterInfo &tri_;
284 /// edit_ - The current parent register and new intervals created.
285 LiveRangeEdit &edit_;
287 /// dupli_ - Created as a copy of curli_, ranges are carved out as new
288 /// intervals get added through openIntv / closeIntv. This is used to avoid
290 LiveIntervalMap dupli_;
292 /// Currently open LiveInterval.
293 LiveIntervalMap openli_;
295 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
296 /// rematerialization or a COPY from parent. Return the new value.
297 VNInfo *defFromParent(LiveIntervalMap &Reg,
300 MachineBasicBlock &MBB,
301 MachineBasicBlock::iterator I);
303 /// intervalsLiveAt - Return true if any member of intervals_ is live at Idx.
304 bool intervalsLiveAt(SlotIndex Idx) const;
306 /// Values in curli whose live range has been truncated when entering an open
308 SmallPtrSet<const VNInfo*, 8> truncatedValues;
310 /// addTruncSimpleRange - Add the given simple range to dupli_ after
311 /// truncating any overlap with intervals_.
312 void addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI);
314 /// criticalPreds_ - Set of basic blocks where both dupli and openli should be
315 /// live out because of a critical edge.
316 SplitAnalysis::BlockPtrSet criticalPreds_;
318 /// computeRemainder - Compute the dupli liveness as the complement of all the
320 void computeRemainder();
322 /// rewrite - Rewrite all uses of reg to use the new registers.
323 void rewrite(unsigned reg);
326 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
327 /// Newly created intervals will be appended to newIntervals.
328 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
329 MachineDominatorTree&, LiveRangeEdit&);
331 /// getAnalysis - Get the corresponding analysis.
332 SplitAnalysis &getAnalysis() { return sa_; }
334 /// Create a new virtual register and live interval.
337 /// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
338 /// not live before Idx, a COPY is not inserted.
339 void enterIntvBefore(SlotIndex Idx);
341 /// enterIntvAtEnd - Enter openli at the end of MBB.
342 void enterIntvAtEnd(MachineBasicBlock &MBB);
344 /// useIntv - indicate that all instructions in MBB should use openli.
345 void useIntv(const MachineBasicBlock &MBB);
347 /// useIntv - indicate that all instructions in range should use openli.
348 void useIntv(SlotIndex Start, SlotIndex End);
350 /// leaveIntvAfter - Leave openli after the instruction at Idx.
351 void leaveIntvAfter(SlotIndex Idx);
353 /// leaveIntvAtTop - Leave the interval at the top of MBB.
354 /// Currently, only one value can leave the interval.
355 void leaveIntvAtTop(MachineBasicBlock &MBB);
357 /// closeIntv - Indicate that we are done editing the currently open
358 /// LiveInterval, and ranges can be trimmed.
361 /// finish - after all the new live ranges have been created, compute the
362 /// remaining live range, and rewrite instructions to use the new registers.
365 // ===--- High level methods ---===
367 /// splitAroundLoop - Split curli into a separate live interval inside
369 void splitAroundLoop(const MachineLoop*);
371 /// splitSingleBlocks - Split curli into a separate live interval inside each
372 /// basic block in Blocks.
373 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
375 /// splitInsideBlock - Split curli into multiple intervals inside MBB.
376 void splitInsideBlock(const MachineBasicBlock *);