1 //===-------- SplitKit.h - 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/DenseMap.h"
16 #include "llvm/ADT/IntervalMap.h"
17 #include "llvm/ADT/SmallPtrSet.h"
18 #include "llvm/CodeGen/SlotIndexes.h"
22 class ConnectedVNInfoEqClasses;
28 class MachineLoopInfo;
29 class MachineRegisterInfo;
30 class TargetInstrInfo;
31 class TargetRegisterInfo;
36 /// At some point we should just include MachineDominators.h:
37 class MachineDominatorTree;
38 template <class NodeT> class DomTreeNodeBase;
39 typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
42 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
46 const MachineFunction &MF;
47 const LiveIntervals &LIS;
48 const MachineLoopInfo &Loops;
49 const TargetInstrInfo &TII;
51 // Instructions using the the current register.
52 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
53 InstrPtrSet UsingInstrs;
55 // Sorted slot indexes of using instructions.
56 SmallVector<SlotIndex, 8> UseSlots;
58 // The number of instructions using CurLI in each basic block.
59 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
60 BlockCountMap UsingBlocks;
62 // The number of basic block using CurLI in each loop.
63 typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap;
64 LoopCountMap UsingLoops;
66 /// Additional information about basic blocks where the current variable is
67 /// live. Such a block will look like one of these templates:
69 /// 1. | o---x | Internal to block. Variable is only live in this block.
70 /// 2. |---x | Live-in, kill.
71 /// 3. | o---| Def, live-out.
72 /// 4. |---x o---| Live-in, kill, def, live-out.
73 /// 5. |---o---o---| Live-through with uses or defs.
74 /// 6. |-----------| Live-through without uses. Transparent.
77 MachineBasicBlock *MBB;
78 SlotIndex FirstUse; ///< First instr using current reg.
79 SlotIndex LastUse; ///< Last instr using current reg.
80 SlotIndex Kill; ///< Interval end point inside block.
81 SlotIndex Def; ///< Interval start point inside block.
82 /// Last possible point for splitting live ranges.
83 SlotIndex LastSplitPoint;
84 bool Uses; ///< Current reg has uses or defs in block.
85 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above).
86 bool LiveIn; ///< Current reg is live in.
87 bool LiveOut; ///< Current reg is live out.
89 // Per-interference pattern scratch data.
90 bool OverlapEntry; ///< Interference overlaps entering interval.
91 bool OverlapExit; ///< Interference overlaps exiting interval.
94 /// Basic blocks where var is live. This array is parallel to
96 SmallVector<BlockInfo, 8> LiveBlocks;
99 // Current live interval.
100 const LiveInterval *CurLI;
102 // Sumarize statistics by counting instructions using CurLI.
105 /// calcLiveBlockInfo - Compute per-block information about CurLI.
106 void calcLiveBlockInfo();
108 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be
110 bool canAnalyzeBranch(const MachineBasicBlock *MBB);
113 SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis,
114 const MachineLoopInfo &mli);
116 /// analyze - set CurLI to the specified interval, and analyze how it may be
118 void analyze(const LiveInterval *li);
120 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
124 /// hasUses - Return true if MBB has any uses of CurLI.
125 bool hasUses(const MachineBasicBlock *MBB) const {
126 return UsingBlocks.lookup(MBB);
129 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
130 typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
132 // Print a set of blocks with use counts.
133 void print(const BlockPtrSet&, raw_ostream&) const;
135 // Sets of basic blocks surrounding a machine loop.
137 BlockPtrSet Loop; // Blocks in the loop.
138 BlockPtrSet Preds; // Loop predecessor blocks.
139 BlockPtrSet Exits; // Loop exit blocks.
148 // Print loop blocks with use counts.
149 void print(const LoopBlocks&, raw_ostream&) const;
151 // Calculate the block sets surrounding the loop.
152 void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks);
154 /// LoopPeripheralUse - how is a variable used in and around a loop?
155 /// Peripheral blocks are the loop predecessors and exit blocks.
156 enum LoopPeripheralUse {
157 ContainedInLoop, // All uses are inside the loop.
158 SinglePeripheral, // At most one instruction per peripheral block.
159 MultiPeripheral, // Multiple instructions in some peripheral blocks.
160 OutsideLoop // Uses outside loop periphery.
163 /// analyzeLoopPeripheralUse - Return an enum describing how CurLI is used in
164 /// and around the Loop.
165 LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&);
167 /// getCriticalExits - It may be necessary to partially break critical edges
168 /// leaving the loop if an exit block has phi uses of CurLI. Collect the exit
169 /// blocks that need special treatment into CriticalExits.
170 void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits);
172 /// canSplitCriticalExits - Return true if it is possible to insert new exit
173 /// blocks before the blocks in CriticalExits.
174 bool canSplitCriticalExits(const LoopBlocks &Blocks,
175 BlockPtrSet &CriticalExits);
177 /// getCriticalPreds - Get the set of loop predecessors with critical edges to
178 /// blocks outside the loop that have CurLI live in. We don't have to break
179 /// these edges, but they do require special treatment.
180 void getCriticalPreds(const LoopBlocks &Blocks, BlockPtrSet &CriticalPreds);
182 /// getSplitLoops - Get the set of loops that have CurLI uses and would be
183 /// profitable to split.
184 void getSplitLoops(LoopPtrSet&);
186 /// getBestSplitLoop - Return the loop where CurLI may best be split to a
187 /// separate register, or NULL.
188 const MachineLoop *getBestSplitLoop();
190 /// isBypassLoop - Return true if CurLI is live through Loop and has no uses
191 /// inside the loop. Bypass loops are candidates for splitting because it can
192 /// prevent interference inside the loop.
193 bool isBypassLoop(const MachineLoop *Loop);
195 /// getBypassLoops - Get all the maximal bypass loops. These are the bypass
196 /// loops whose parent is not a bypass loop.
197 void getBypassLoops(LoopPtrSet&);
199 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
200 /// having CurLI split to a new live interval. Return true if Blocks can be
201 /// passed to SplitEditor::splitSingleBlocks.
202 bool getMultiUseBlocks(BlockPtrSet &Blocks);
204 /// getBlockForInsideSplit - If CurLI is contained inside a single basic
205 /// block, and it would pay to subdivide the interval inside that block,
206 /// return it. Otherwise return NULL. The returned block can be passed to
207 /// SplitEditor::splitInsideBlock.
208 const MachineBasicBlock *getBlockForInsideSplit();
212 /// LiveIntervalMap - Map values from a large LiveInterval into a small
213 /// interval that is a subset. Insert phi-def values as needed. This class is
214 /// used by SplitEditor to create new smaller LiveIntervals.
216 /// ParentLI is the larger interval, LI is the subset interval. Every value
217 /// in LI corresponds to exactly one value in ParentLI, and the live range
218 /// of the value is contained within the live range of the ParentLI value.
219 /// Values in ParentLI may map to any number of OpenLI values, including 0.
220 class LiveIntervalMap {
222 MachineDominatorTree &MDT;
224 // The parent interval is never changed.
225 const LiveInterval &ParentLI;
227 // The child interval's values are fully contained inside ParentLI values.
230 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
232 // Map ParentLI values to simple values in LI that are defined at the same
233 // SlotIndex, or NULL for ParentLI values that have complex LI defs.
234 // Note there is a difference between values mapping to NULL (complex), and
235 // values not present (unknown/unmapped).
238 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
239 typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap;
241 // LiveOutCache - Map each basic block where LI is live out to the live-out
242 // value and its defining block. One of these conditions shall be true:
244 // 1. !LiveOutCache.count(MBB)
245 // 2. LiveOutCache[MBB].second.getNode() == MBB
246 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
248 // This is only a cache, the values can be computed as:
250 // VNI = LI->getVNInfoAt(LIS.getMBBEndIdx(MBB))
251 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
253 // The cache is also used as a visiteed set by mapValue().
254 LiveOutMap LiveOutCache;
256 // Dump the live-out cache to dbgs().
260 LiveIntervalMap(LiveIntervals &lis,
261 MachineDominatorTree &mdt,
262 const LiveInterval &parentli)
263 : LIS(lis), MDT(mdt), ParentLI(parentli), LI(0) {}
265 /// reset - clear all data structures and start a new live interval.
266 void reset(LiveInterval *);
268 /// getLI - return the current live interval.
269 LiveInterval *getLI() const { return LI; }
271 /// defValue - define a value in LI from the ParentLI value VNI and Idx.
272 /// Idx does not have to be ParentVNI->def, but it must be contained within
273 /// ParentVNI's live range in ParentLI.
274 /// Return the new LI value.
275 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
277 /// mapValue - map ParentVNI to the corresponding LI value at Idx. It is
278 /// assumed that ParentVNI is live at Idx.
279 /// If ParentVNI has not been defined by defValue, it is assumed that
280 /// ParentVNI->def dominates Idx.
281 /// If ParentVNI has been defined by defValue one or more times, a value that
282 /// dominates Idx will be returned. This may require creating extra phi-def
283 /// values and adding live ranges to LI.
284 /// If simple is not NULL, *simple will indicate if ParentVNI is a simply
286 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0);
288 // extendTo - Find the last LI value defined in MBB at or before Idx. The
289 // parentli is assumed to be live at Idx. Extend the live range to include
290 // Idx. Return the found VNInfo, or NULL.
291 VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx);
293 /// isMapped - Return true is ParentVNI is a known mapped value. It may be a
294 /// simple 1-1 mapping or a complex mapping to later defs.
295 bool isMapped(const VNInfo *ParentVNI) const {
296 return Values.count(ParentVNI);
299 /// isComplexMapped - Return true if ParentVNI has received new definitions
301 bool isComplexMapped(const VNInfo *ParentVNI) const;
303 /// markComplexMapped - Mark ParentVNI as complex mapped regardless of the
304 /// number of definitions.
305 void markComplexMapped(const VNInfo *ParentVNI) { Values[ParentVNI] = 0; }
307 // addSimpleRange - Add a simple range from ParentLI to LI.
308 // ParentVNI must be live in the [Start;End) interval.
309 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
311 /// addRange - Add live ranges to LI where [Start;End) intersects ParentLI.
312 /// All needed values whose def is not inside [Start;End) must be defined
313 /// beforehand so mapValue will work.
314 void addRange(SlotIndex Start, SlotIndex End);
318 /// SplitEditor - Edit machine code and LiveIntervals for live range
321 /// - Create a SplitEditor from a SplitAnalysis.
322 /// - Start a new live interval with openIntv.
323 /// - Mark the places where the new interval is entered using enterIntv*
324 /// - Mark the ranges where the new interval is used with useIntv*
325 /// - Mark the places where the interval is exited with exitIntv*.
326 /// - Finish the current interval with closeIntv and repeat from 2.
327 /// - Rewrite instructions with finish().
333 MachineRegisterInfo &MRI;
334 MachineDominatorTree &MDT;
335 const TargetInstrInfo &TII;
336 const TargetRegisterInfo &TRI;
338 /// Edit - The current parent register and new intervals created.
341 /// Index into Edit of the currently open interval.
342 /// The index 0 is used for the complement, so the first interval started by
343 /// openIntv will be 1.
346 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
348 /// Allocator for the interval map. This will eventually be shared with
349 /// SlotIndexes and LiveIntervals.
350 RegAssignMap::Allocator Allocator;
352 /// RegAssign - Map of the assigned register indexes.
353 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
355 RegAssignMap RegAssign;
357 /// LIMappers - One LiveIntervalMap or each interval in Edit.
358 SmallVector<LiveIntervalMap, 4> LIMappers;
360 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
361 /// rematerialization or a COPY from parent. Return the new value.
362 VNInfo *defFromParent(unsigned RegIdx,
365 MachineBasicBlock &MBB,
366 MachineBasicBlock::iterator I);
368 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
369 void rewriteAssigned();
371 /// rewriteComponents - Rewrite all uses of Intv[0] according to the eq
372 /// classes in ConEQ.
373 /// This must be done when Intvs[0] is styill live at all uses, before calling
374 /// ConEq.Distribute().
375 void rewriteComponents(const SmallVectorImpl<LiveInterval*> &Intvs,
376 const ConnectedVNInfoEqClasses &ConEq);
379 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
380 /// Newly created intervals will be appended to newIntervals.
381 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
382 MachineDominatorTree&, LiveRangeEdit&);
384 /// getAnalysis - Get the corresponding analysis.
385 SplitAnalysis &getAnalysis() { return sa_; }
387 /// Create a new virtual register and live interval.
390 /// enterIntvBefore - Enter the open interval before the instruction at Idx.
391 /// If the parent interval is not live before Idx, a COPY is not inserted.
392 /// Return the beginning of the new live range.
393 SlotIndex enterIntvBefore(SlotIndex Idx);
395 /// enterIntvAtEnd - Enter the open interval at the end of MBB.
396 /// Use the open interval from he inserted copy to the MBB end.
397 /// Return the beginning of the new live range.
398 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
400 /// useIntv - indicate that all instructions in MBB should use OpenLI.
401 void useIntv(const MachineBasicBlock &MBB);
403 /// useIntv - indicate that all instructions in range should use OpenLI.
404 void useIntv(SlotIndex Start, SlotIndex End);
406 /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
407 /// Return the end of the live range.
408 SlotIndex leaveIntvAfter(SlotIndex Idx);
410 /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
411 /// Return the end of the live range.
412 SlotIndex leaveIntvBefore(SlotIndex Idx);
414 /// leaveIntvAtTop - Leave the interval at the top of MBB.
415 /// Add liveness from the MBB top to the copy.
416 /// Return the end of the live range.
417 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
419 /// overlapIntv - Indicate that all instructions in range should use the open
420 /// interval, but also let the complement interval be live.
422 /// This doubles the register pressure, but is sometimes required to deal with
423 /// register uses after the last valid split point.
425 /// The Start index should be a return value from a leaveIntv* call, and End
426 /// should be in the same basic block. The parent interval must have the same
427 /// value across the range.
429 void overlapIntv(SlotIndex Start, SlotIndex End);
431 /// closeIntv - Indicate that we are done editing the currently open
432 /// LiveInterval, and ranges can be trimmed.
435 /// finish - after all the new live ranges have been created, compute the
436 /// remaining live range, and rewrite instructions to use the new registers.
439 /// dump - print the current interval maping to dbgs().
442 // ===--- High level methods ---===
444 /// splitAroundLoop - Split CurLI into a separate live interval inside
446 void splitAroundLoop(const MachineLoop*);
448 /// splitSingleBlocks - Split CurLI into a separate live interval inside each
449 /// basic block in Blocks.
450 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
452 /// splitInsideBlock - Split CurLI into multiple intervals inside MBB.
453 void splitInsideBlock(const MachineBasicBlock *);