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 #ifndef LLVM_CODEGEN_SPLITKIT_H
16 #define LLVM_CODEGEN_SPLITKIT_H
18 #include "llvm/ADT/ArrayRef.h"
19 #include "llvm/ADT/BitVector.h"
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/IndexedMap.h"
22 #include "llvm/ADT/IntervalMap.h"
23 #include "llvm/ADT/SmallPtrSet.h"
24 #include "llvm/CodeGen/SlotIndexes.h"
28 class ConnectedVNInfoEqClasses;
33 class MachineLoopInfo;
34 class MachineRegisterInfo;
35 class TargetInstrInfo;
36 class TargetRegisterInfo;
41 /// At some point we should just include MachineDominators.h:
42 class MachineDominatorTree;
43 template <class NodeT> class DomTreeNodeBase;
44 typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
47 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
51 const MachineFunction &MF;
52 const VirtRegMap &VRM;
53 const LiveIntervals &LIS;
54 const MachineLoopInfo &Loops;
55 const TargetInstrInfo &TII;
57 // Sorted slot indexes of using instructions.
58 SmallVector<SlotIndex, 8> UseSlots;
60 /// Additional information about basic blocks where the current variable is
61 /// live. Such a block will look like one of these templates:
63 /// 1. | o---x | Internal to block. Variable is only live in this block.
64 /// 2. |---x | Live-in, kill.
65 /// 3. | o---| Def, live-out.
66 /// 4. |---x o---| Live-in, kill, def, live-out. Counted by NumGapBlocks.
67 /// 5. |---o---o---| Live-through with uses or defs.
68 /// 6. |-----------| Live-through without uses. Counted by NumThroughBlocks.
70 /// Two BlockInfo entries are created for template 4. One for the live-in
71 /// segment, and one for the live-out segment. These entries look as if the
72 /// block were split in the middle where the live range isn't live.
74 /// Live-through blocks without any uses don't get BlockInfo entries. They
75 /// are simply listed in ThroughBlocks instead.
78 MachineBasicBlock *MBB;
79 SlotIndex FirstUse; ///< First instr using current reg.
80 SlotIndex LastUse; ///< Last instr using current reg.
81 bool LiveIn; ///< Current reg is live in.
82 bool LiveOut; ///< Current reg is live out.
84 /// isOneInstr - Returns true when this BlockInfo describes a single
86 bool isOneInstr() const {
87 return SlotIndex::isSameInstr(FirstUse, LastUse);
92 // Current live interval.
93 const LiveInterval *CurLI;
95 /// LastSplitPoint - Last legal split point in each basic block in the current
96 /// function. The first entry is the first terminator, the second entry is the
97 /// last valid split point for a variable that is live in to a landing pad
99 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint;
101 /// UseBlocks - Blocks where CurLI has uses.
102 SmallVector<BlockInfo, 8> UseBlocks;
104 /// NumGapBlocks - Number of duplicate entries in UseBlocks for blocks where
105 /// the live range has a gap.
106 unsigned NumGapBlocks;
108 /// ThroughBlocks - Block numbers where CurLI is live through without uses.
109 BitVector ThroughBlocks;
111 /// NumThroughBlocks - Number of live-through blocks.
112 unsigned NumThroughBlocks;
114 /// DidRepairRange - analyze was forced to shrinkToUses().
117 SlotIndex computeLastSplitPoint(unsigned Num);
119 // Sumarize statistics by counting instructions using CurLI.
122 /// calcLiveBlockInfo - Compute per-block information about CurLI.
123 bool calcLiveBlockInfo();
126 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
127 const MachineLoopInfo &mli);
129 /// analyze - set CurLI to the specified interval, and analyze how it may be
131 void analyze(const LiveInterval *li);
133 /// didRepairRange() - Returns true if CurLI was invalid and has been repaired
134 /// by analyze(). This really shouldn't happen, but sometimes the coalescer
135 /// can create live ranges that end in mid-air.
136 bool didRepairRange() const { return DidRepairRange; }
138 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
142 /// getParent - Return the last analyzed interval.
143 const LiveInterval &getParent() const { return *CurLI; }
145 /// getLastSplitPoint - Return that base index of the last valid split point
146 /// in the basic block numbered Num.
147 SlotIndex getLastSplitPoint(unsigned Num) {
148 // Inline the common simple case.
149 if (LastSplitPoint[Num].first.isValid() &&
150 !LastSplitPoint[Num].second.isValid())
151 return LastSplitPoint[Num].first;
152 return computeLastSplitPoint(Num);
155 /// isOriginalEndpoint - Return true if the original live range was killed or
156 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def,
157 /// and 'use' for an early-clobber def.
158 /// This can be used to recognize code inserted by earlier live range
160 bool isOriginalEndpoint(SlotIndex Idx) const;
162 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks
163 /// where CurLI has uses.
164 ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; }
166 /// getNumThroughBlocks - Return the number of through blocks.
167 unsigned getNumThroughBlocks() const { return NumThroughBlocks; }
169 /// isThroughBlock - Return true if CurLI is live through MBB without uses.
170 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); }
172 /// getThroughBlocks - Return the set of through blocks.
173 const BitVector &getThroughBlocks() const { return ThroughBlocks; }
175 /// getNumLiveBlocks - Return the number of blocks where CurLI is live.
176 unsigned getNumLiveBlocks() const {
177 return getUseBlocks().size() - NumGapBlocks + getNumThroughBlocks();
180 /// countLiveBlocks - Return the number of blocks where li is live. This is
181 /// guaranteed to return the same number as getNumLiveBlocks() after calling
183 unsigned countLiveBlocks(const LiveInterval *li) const;
185 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
187 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
188 /// having CurLI split to a new live interval. Return true if Blocks can be
189 /// passed to SplitEditor::splitSingleBlocks.
190 bool getMultiUseBlocks(BlockPtrSet &Blocks);
194 /// SplitEditor - Edit machine code and LiveIntervals for live range
197 /// - Create a SplitEditor from a SplitAnalysis.
198 /// - Start a new live interval with openIntv.
199 /// - Mark the places where the new interval is entered using enterIntv*
200 /// - Mark the ranges where the new interval is used with useIntv*
201 /// - Mark the places where the interval is exited with exitIntv*.
202 /// - Finish the current interval with closeIntv and repeat from 2.
203 /// - Rewrite instructions with finish().
209 MachineRegisterInfo &MRI;
210 MachineDominatorTree &MDT;
211 const TargetInstrInfo &TII;
212 const TargetRegisterInfo &TRI;
214 /// Edit - The current parent register and new intervals created.
217 /// Index into Edit of the currently open interval.
218 /// The index 0 is used for the complement, so the first interval started by
219 /// openIntv will be 1.
222 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
224 /// Allocator for the interval map. This will eventually be shared with
225 /// SlotIndexes and LiveIntervals.
226 RegAssignMap::Allocator Allocator;
228 /// RegAssign - Map of the assigned register indexes.
229 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
231 RegAssignMap RegAssign;
233 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap;
235 /// Values - keep track of the mapping from parent values to values in the new
236 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains:
238 /// 1. No entry - the value is not mapped to Edit.get(RegIdx).
239 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx).
240 /// Each value is represented by a minimal live range at its def.
241 /// 3. A non-null VNInfo - the value is mapped to a single new value.
242 /// The new value has no live ranges anywhere.
245 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
246 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap;
248 // LiveOutCache - Map each basic block where a new register is live out to the
249 // live-out value and its defining block.
250 // One of these conditions shall be true:
252 // 1. !LiveOutCache.count(MBB)
253 // 2. LiveOutCache[MBB].second.getNode() == MBB
254 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
256 // This is only a cache, the values can be computed as:
258 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB))
259 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
261 // The cache is also used as a visited set by extendRange(). It can be shared
262 // by all the new registers because at most one is live out of each block.
263 LiveOutMap LiveOutCache;
265 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid
266 // entry in LiveOutCache.
267 BitVector LiveOutSeen;
269 /// LiveInBlock - Info for updateSSA() about a block where a register is
271 /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA()
272 /// adds the computed live-in value.
274 // Dominator tree node for the block.
275 // Cleared by updateSSA when the final value has been determined.
276 MachineDomTreeNode *DomNode;
278 // Live-in value filled in by updateSSA once it is known.
281 // Position in block where the live-in range ends, or SlotIndex() if the
282 // range passes through the block.
285 LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {}
288 /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and
289 /// updateSSA(). This list is usually empty, it exists here to avoid frequent
291 SmallVector<LiveInBlock, 16> LiveInBlocks;
293 /// defValue - define a value in RegIdx from ParentVNI at Idx.
294 /// Idx does not have to be ParentVNI->def, but it must be contained within
295 /// ParentVNI's live range in ParentLI. The new value is added to the value
297 /// Return the new LI value.
298 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx);
300 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless
301 /// of the number of defs.
302 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI);
304 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
305 /// rematerialization or a COPY from parent. Return the new value.
306 VNInfo *defFromParent(unsigned RegIdx,
309 MachineBasicBlock &MBB,
310 MachineBasicBlock::iterator I);
312 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx.
313 /// Insert PHIDefs as needed to preserve SSA form.
314 void extendRange(unsigned RegIdx, SlotIndex Idx);
316 /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all
317 /// reaching defs for LI are found.
318 /// @param LI Live interval whose value is needed.
319 /// @param MBB Block where LI should be live-in.
320 /// @param Kill Kill point in MBB.
321 /// @return Unique value seen, or NULL.
322 VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB,
325 /// updateSSA - Compute and insert PHIDefs such that all blocks in
326 // LiveInBlocks get a known live-in value. Add live ranges to the blocks.
329 /// transferValues - Transfer values to the new ranges.
330 /// Return true if any ranges were skipped.
331 bool transferValues();
333 /// extendPHIKillRanges - Extend the ranges of all values killed by original
335 void extendPHIKillRanges();
337 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
338 void rewriteAssigned(bool ExtendRanges);
340 /// deleteRematVictims - Delete defs that are dead after rematerializing.
341 void deleteRematVictims();
344 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
345 /// Newly created intervals will be appended to newIntervals.
346 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
347 MachineDominatorTree&);
349 /// reset - Prepare for a new split.
350 void reset(LiveRangeEdit&);
352 /// Create a new virtual register and live interval.
353 /// Return the interval index, starting from 1. Interval index 0 is the
354 /// implicit complement interval.
357 /// currentIntv - Return the current interval index.
358 unsigned currentIntv() const { return OpenIdx; }
360 /// selectIntv - Select a previously opened interval index.
361 void selectIntv(unsigned Idx);
363 /// enterIntvBefore - Enter the open interval before the instruction at Idx.
364 /// If the parent interval is not live before Idx, a COPY is not inserted.
365 /// Return the beginning of the new live range.
366 SlotIndex enterIntvBefore(SlotIndex Idx);
368 /// enterIntvAfter - Enter the open interval after the instruction at Idx.
369 /// Return the beginning of the new live range.
370 SlotIndex enterIntvAfter(SlotIndex Idx);
372 /// enterIntvAtEnd - Enter the open interval at the end of MBB.
373 /// Use the open interval from he inserted copy to the MBB end.
374 /// Return the beginning of the new live range.
375 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
377 /// useIntv - indicate that all instructions in MBB should use OpenLI.
378 void useIntv(const MachineBasicBlock &MBB);
380 /// useIntv - indicate that all instructions in range should use OpenLI.
381 void useIntv(SlotIndex Start, SlotIndex End);
383 /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
384 /// Return the end of the live range.
385 SlotIndex leaveIntvAfter(SlotIndex Idx);
387 /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
388 /// Return the end of the live range.
389 SlotIndex leaveIntvBefore(SlotIndex Idx);
391 /// leaveIntvAtTop - Leave the interval at the top of MBB.
392 /// Add liveness from the MBB top to the copy.
393 /// Return the end of the live range.
394 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
396 /// overlapIntv - Indicate that all instructions in range should use the open
397 /// interval, but also let the complement interval be live.
399 /// This doubles the register pressure, but is sometimes required to deal with
400 /// register uses after the last valid split point.
402 /// The Start index should be a return value from a leaveIntv* call, and End
403 /// should be in the same basic block. The parent interval must have the same
404 /// value across the range.
406 void overlapIntv(SlotIndex Start, SlotIndex End);
408 /// finish - after all the new live ranges have been created, compute the
409 /// remaining live range, and rewrite instructions to use the new registers.
410 /// @param LRMap When not null, this vector will map each live range in Edit
411 /// back to the indices returned by openIntv.
412 /// There may be extra indices created by dead code elimination.
413 void finish(SmallVectorImpl<unsigned> *LRMap = 0);
415 /// dump - print the current interval maping to dbgs().
418 // ===--- High level methods ---===
420 /// splitSingleBlock - Split CurLI into a separate live interval around the
421 /// uses in a single block. This is intended to be used as part of a larger
422 /// split, and doesn't call finish().
423 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI);
425 /// splitSingleBlocks - Split CurLI into a separate live interval inside each
426 /// basic block in Blocks.
427 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
429 /// splitLiveThroughBlock - Split CurLI in the given block such that it
430 /// enters the block in IntvIn and leaves it in IntvOut. There may be uses in
431 /// the block, but they will be ignored when placing split points.
433 /// @param MBBNum Block number.
434 /// @param IntvIn Interval index entering the block.
435 /// @param LeaveBefore When set, leave IntvIn before this point.
436 /// @param IntvOut Interval index leaving the block.
437 /// @param EnterAfter When set, enter IntvOut after this point.
438 void splitLiveThroughBlock(unsigned MBBNum,
439 unsigned IntvIn, SlotIndex LeaveBefore,
440 unsigned IntvOut, SlotIndex EnterAfter);
442 /// splitRegInBlock - Split CurLI in the given block such that it enters the
443 /// block in IntvIn and leaves it on the stack (or not at all). Split points
444 /// are placed in a way that avoids putting uses in the stack interval. This
445 /// may require creating a local interval when there is interference.
447 /// @param BI Block descriptor.
448 /// @param IntvIn Interval index entering the block. Not 0.
449 /// @param LeaveBefore When set, leave IntvIn before this point.
450 void splitRegInBlock(const SplitAnalysis::BlockInfo &BI,
451 unsigned IntvIn, SlotIndex LeaveBefore);
453 /// splitRegOutBlock - Split CurLI in the given block such that it enters the
454 /// block on the stack (or isn't live-in at all) and leaves it in IntvOut.
455 /// Split points are placed to avoid interference and such that the uses are
456 /// not in the stack interval. This may require creating a local interval
457 /// when there is interference.
459 /// @param BI Block descriptor.
460 /// @param IntvOut Interval index leaving the block.
461 /// @param EnterAfter When set, enter IntvOut after this point.
462 void splitRegOutBlock(const SplitAnalysis::BlockInfo &BI,
463 unsigned IntvOut, SlotIndex EnterAfter);