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;
33 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
37 const MachineFunction &mf_;
38 const LiveIntervals &lis_;
39 const MachineLoopInfo &loops_;
40 const TargetInstrInfo &tii_;
42 // Instructions using the the current register.
43 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
44 InstrPtrSet usingInstrs_;
46 // The number of instructions using curli in each basic block.
47 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
48 BlockCountMap usingBlocks_;
50 // The number of basic block using curli in each loop.
51 typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap;
52 LoopCountMap usingLoops_;
55 // Current live interval.
56 const LiveInterval *curli_;
58 // Sumarize statistics by counting instructions using curli_.
61 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be
63 bool canAnalyzeBranch(const MachineBasicBlock *MBB);
66 SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis,
67 const MachineLoopInfo &mli);
69 /// analyze - set curli to the specified interval, and analyze how it may be
71 void analyze(const LiveInterval *li);
73 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
77 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
78 typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
80 // Print a set of blocks with use counts.
81 void print(const BlockPtrSet&, raw_ostream&) const;
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 // Print loop blocks with use counts.
97 void print(const LoopBlocks&, raw_ostream&) const;
99 // Calculate the block sets surrounding the loop.
100 void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks);
102 /// LoopPeripheralUse - how is a variable used in and around a loop?
103 /// Peripheral blocks are the loop predecessors and exit blocks.
104 enum LoopPeripheralUse {
105 ContainedInLoop, // All uses are inside the loop.
106 SinglePeripheral, // At most one instruction per peripheral block.
107 MultiPeripheral, // Multiple instructions in some peripheral blocks.
108 OutsideLoop // Uses outside loop periphery.
111 /// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
112 /// and around the Loop.
113 LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&);
115 /// getCriticalExits - It may be necessary to partially break critical edges
116 /// leaving the loop if an exit block has phi uses of curli. Collect the exit
117 /// blocks that need special treatment into CriticalExits.
118 void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits);
120 /// canSplitCriticalExits - Return true if it is possible to insert new exit
121 /// blocks before the blocks in CriticalExits.
122 bool canSplitCriticalExits(const LoopBlocks &Blocks,
123 BlockPtrSet &CriticalExits);
125 /// getCriticalPreds - Get the set of loop predecessors with critical edges to
126 /// blocks outside the loop that have curli live in. We don't have to break
127 /// these edges, but they do require special treatment.
128 void getCriticalPreds(const LoopBlocks &Blocks, BlockPtrSet &CriticalPreds);
130 /// getBestSplitLoop - Return the loop where curli may best be split to a
131 /// separate register, or NULL.
132 const MachineLoop *getBestSplitLoop();
134 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
135 /// having curli split to a new live interval. Return true if Blocks can be
136 /// passed to SplitEditor::splitSingleBlocks.
137 bool getMultiUseBlocks(BlockPtrSet &Blocks);
139 /// getBlockForInsideSplit - If curli is contained inside a single basic block,
140 /// and it wou pay to subdivide the interval inside that block, return it.
141 /// Otherwise return NULL. The returned block can be passed to
142 /// SplitEditor::splitInsideBlock.
143 const MachineBasicBlock *getBlockForInsideSplit();
147 /// LiveIntervalMap - Map values from a large LiveInterval into a small
148 /// interval that is a subset. Insert phi-def values as needed. This class is
149 /// used by SplitEditor to create new smaller LiveIntervals.
151 /// parentli_ is the larger interval, li_ is the subset interval. Every value
152 /// in li_ corresponds to exactly one value in parentli_, and the live range
153 /// of the value is contained within the live range of the parentli_ value.
154 /// Values in parentli_ may map to any number of openli_ values, including 0.
155 class LiveIntervalMap {
158 // The parent interval is never changed.
159 const LiveInterval &parentli_;
161 // The child interval's values are fully contained inside parentli_ values.
164 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
166 // Map parentli_ values to simple values in li_ that are defined at the same
167 // SlotIndex, or NULL for parentli_ values that have complex li_ defs.
168 // Note there is a difference between values mapping to NULL (complex), and
169 // values not present (unknown/unmapped).
173 LiveIntervalMap(LiveIntervals &lis,
174 const LiveInterval &parentli)
175 : lis_(lis), parentli_(parentli), li_(0) {}
177 /// reset - clear all data structures and start a new live interval.
178 void reset(LiveInterval *);
180 /// getLI - return the current live interval.
181 LiveInterval *getLI() const { return li_; }
183 /// defValue - define a value in li_ from the parentli_ value VNI and Idx.
184 /// Idx does not have to be ParentVNI->def, but it must be contained within
185 /// ParentVNI's live range in parentli_.
186 /// Return the new li_ value.
187 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
189 /// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is
190 /// assumed that ParentVNI is live at Idx.
191 /// If ParentVNI has not been defined by defValue, it is assumed that
192 /// ParentVNI->def dominates Idx.
193 /// If ParentVNI has been defined by defValue one or more times, a value that
194 /// dominates Idx will be returned. This may require creating extra phi-def
195 /// values and adding live ranges to li_.
196 /// If simple is not NULL, *simple will indicate if ParentVNI is a simply
198 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0);
200 // extendTo - Find the last li_ value defined in MBB at or before Idx. The
201 // parentli is assumed to be live at Idx. Extend the live range to include
202 // Idx. Return the found VNInfo, or NULL.
203 VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx);
205 /// isMapped - Return true is ParentVNI is a known mapped value. It may be a
206 /// simple 1-1 mapping or a complex mapping to later defs.
207 bool isMapped(const VNInfo *ParentVNI) const {
208 return valueMap_.count(ParentVNI);
211 /// isComplexMapped - Return true if ParentVNI has received new definitions
213 bool isComplexMapped(const VNInfo *ParentVNI) const;
215 // addSimpleRange - Add a simple range from parentli_ to li_.
216 // ParentVNI must be live in the [Start;End) interval.
217 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
219 /// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
220 /// All needed values whose def is not inside [Start;End) must be defined
221 /// beforehand so mapValue will work.
222 void addRange(SlotIndex Start, SlotIndex End);
224 /// defByCopyFrom - Insert a copy from Reg to li, assuming that Reg carries
225 /// ParentVNI. Add a minimal live range for the new value and return it.
226 VNInfo *defByCopyFrom(unsigned Reg,
227 const VNInfo *ParentVNI,
228 MachineBasicBlock &MBB,
229 MachineBasicBlock::iterator I);
234 /// SplitEditor - Edit machine code and LiveIntervals for live range
237 /// - Create a SplitEditor from a SplitAnalysis.
238 /// - Start a new live interval with openIntv.
239 /// - Mark the places where the new interval is entered using enterIntv*
240 /// - Mark the ranges where the new interval is used with useIntv*
241 /// - Mark the places where the interval is exited with exitIntv*.
242 /// - Finish the current interval with closeIntv and repeat from 2.
243 /// - Rewrite instructions with finish().
249 MachineRegisterInfo &mri_;
250 const TargetInstrInfo &tii_;
252 /// edit_ - The current parent register and new intervals created.
253 LiveRangeEdit &edit_;
255 /// dupli_ - Created as a copy of curli_, ranges are carved out as new
256 /// intervals get added through openIntv / closeIntv. This is used to avoid
258 LiveIntervalMap dupli_;
260 /// Currently open LiveInterval.
261 LiveIntervalMap openli_;
263 /// intervalsLiveAt - Return true if any member of intervals_ is live at Idx.
264 bool intervalsLiveAt(SlotIndex Idx) const;
266 /// Values in curli whose live range has been truncated when entering an open
268 SmallPtrSet<const VNInfo*, 8> truncatedValues;
270 /// addTruncSimpleRange - Add the given simple range to dupli_ after
271 /// truncating any overlap with intervals_.
272 void addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI);
274 /// criticalPreds_ - Set of basic blocks where both dupli and openli should be
275 /// live out because of a critical edge.
276 SplitAnalysis::BlockPtrSet criticalPreds_;
278 /// computeRemainder - Compute the dupli liveness as the complement of all the
280 void computeRemainder();
282 /// rewrite - Rewrite all uses of reg to use the new registers.
283 void rewrite(unsigned reg);
286 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
287 /// Newly created intervals will be appended to newIntervals.
288 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&, LiveRangeEdit&);
290 /// getAnalysis - Get the corresponding analysis.
291 SplitAnalysis &getAnalysis() { return sa_; }
293 /// Create a new virtual register and live interval.
296 /// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
297 /// not live before Idx, a COPY is not inserted.
298 void enterIntvBefore(SlotIndex Idx);
300 /// enterIntvAtEnd - Enter openli at the end of MBB.
301 void enterIntvAtEnd(MachineBasicBlock &MBB);
303 /// useIntv - indicate that all instructions in MBB should use openli.
304 void useIntv(const MachineBasicBlock &MBB);
306 /// useIntv - indicate that all instructions in range should use openli.
307 void useIntv(SlotIndex Start, SlotIndex End);
309 /// leaveIntvAfter - Leave openli after the instruction at Idx.
310 void leaveIntvAfter(SlotIndex Idx);
312 /// leaveIntvAtTop - Leave the interval at the top of MBB.
313 /// Currently, only one value can leave the interval.
314 void leaveIntvAtTop(MachineBasicBlock &MBB);
316 /// closeIntv - Indicate that we are done editing the currently open
317 /// LiveInterval, and ranges can be trimmed.
320 /// finish - after all the new live ranges have been created, compute the
321 /// remaining live range, and rewrite instructions to use the new registers.
324 // ===--- High level methods ---===
326 /// splitAroundLoop - Split curli into a separate live interval inside
328 void splitAroundLoop(const MachineLoop*);
330 /// splitSingleBlocks - Split curli into a separate live interval inside each
331 /// basic block in Blocks.
332 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
334 /// splitInsideBlock - Split curli into multiple intervals inside MBB.
335 void splitInsideBlock(const MachineBasicBlock *);