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 LiveThrough; ///< Live in whole block (Templ 5. above).
82 bool LiveIn; ///< Current reg is live in.
83 bool LiveOut; ///< Current reg is live out.
87 // Current live interval.
88 const LiveInterval *CurLI;
90 /// LastSplitPoint - Last legal split point in each basic block in the current
91 /// function. The first entry is the first terminator, the second entry is the
92 /// last valid split point for a variable that is live in to a landing pad
94 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint;
96 /// UseBlocks - Blocks where CurLI has uses.
97 SmallVector<BlockInfo, 8> UseBlocks;
99 /// NumGapBlocks - Number of duplicate entries in UseBlocks for blocks where
100 /// the live range has a gap.
101 unsigned NumGapBlocks;
103 /// ThroughBlocks - Block numbers where CurLI is live through without uses.
104 BitVector ThroughBlocks;
106 /// NumThroughBlocks - Number of live-through blocks.
107 unsigned NumThroughBlocks;
109 /// DidRepairRange - analyze was forced to shrinkToUses().
112 SlotIndex computeLastSplitPoint(unsigned Num);
114 // Sumarize statistics by counting instructions using CurLI.
117 /// calcLiveBlockInfo - Compute per-block information about CurLI.
118 bool calcLiveBlockInfo();
121 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
122 const MachineLoopInfo &mli);
124 /// analyze - set CurLI to the specified interval, and analyze how it may be
126 void analyze(const LiveInterval *li);
128 /// didRepairRange() - Returns true if CurLI was invalid and has been repaired
129 /// by analyze(). This really shouldn't happen, but sometimes the coalescer
130 /// can create live ranges that end in mid-air.
131 bool didRepairRange() const { return DidRepairRange; }
133 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
137 /// getParent - Return the last analyzed interval.
138 const LiveInterval &getParent() const { return *CurLI; }
140 /// getLastSplitPoint - Return that base index of the last valid split point
141 /// in the basic block numbered Num.
142 SlotIndex getLastSplitPoint(unsigned Num) {
143 // Inline the common simple case.
144 if (LastSplitPoint[Num].first.isValid() &&
145 !LastSplitPoint[Num].second.isValid())
146 return LastSplitPoint[Num].first;
147 return computeLastSplitPoint(Num);
150 /// isOriginalEndpoint - Return true if the original live range was killed or
151 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def,
152 /// and 'use' for an early-clobber def.
153 /// This can be used to recognize code inserted by earlier live range
155 bool isOriginalEndpoint(SlotIndex Idx) const;
157 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks
158 /// where CurLI has uses.
159 ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; }
161 /// getNumThroughBlocks - Return the number of through blocks.
162 unsigned getNumThroughBlocks() const { return NumThroughBlocks; }
164 /// isThroughBlock - Return true if CurLI is live through MBB without uses.
165 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); }
167 /// getThroughBlocks - Return the set of through blocks.
168 const BitVector &getThroughBlocks() const { return ThroughBlocks; }
170 /// getNumLiveBlocks - Return the number of blocks where CurLI is live.
171 unsigned getNumLiveBlocks() const {
172 return getUseBlocks().size() - NumGapBlocks + getNumThroughBlocks();
175 /// countLiveBlocks - Return the number of blocks where li is live. This is
176 /// guaranteed to return the same number as getNumLiveBlocks() after calling
178 unsigned countLiveBlocks(const LiveInterval *li) const;
180 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
182 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
183 /// having CurLI split to a new live interval. Return true if Blocks can be
184 /// passed to SplitEditor::splitSingleBlocks.
185 bool getMultiUseBlocks(BlockPtrSet &Blocks);
189 /// SplitEditor - Edit machine code and LiveIntervals for live range
192 /// - Create a SplitEditor from a SplitAnalysis.
193 /// - Start a new live interval with openIntv.
194 /// - Mark the places where the new interval is entered using enterIntv*
195 /// - Mark the ranges where the new interval is used with useIntv*
196 /// - Mark the places where the interval is exited with exitIntv*.
197 /// - Finish the current interval with closeIntv and repeat from 2.
198 /// - Rewrite instructions with finish().
204 MachineRegisterInfo &MRI;
205 MachineDominatorTree &MDT;
206 const TargetInstrInfo &TII;
207 const TargetRegisterInfo &TRI;
209 /// Edit - The current parent register and new intervals created.
212 /// Index into Edit of the currently open interval.
213 /// The index 0 is used for the complement, so the first interval started by
214 /// openIntv will be 1.
217 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
219 /// Allocator for the interval map. This will eventually be shared with
220 /// SlotIndexes and LiveIntervals.
221 RegAssignMap::Allocator Allocator;
223 /// RegAssign - Map of the assigned register indexes.
224 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
226 RegAssignMap RegAssign;
228 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap;
230 /// Values - keep track of the mapping from parent values to values in the new
231 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains:
233 /// 1. No entry - the value is not mapped to Edit.get(RegIdx).
234 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx).
235 /// Each value is represented by a minimal live range at its def.
236 /// 3. A non-null VNInfo - the value is mapped to a single new value.
237 /// The new value has no live ranges anywhere.
240 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
241 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap;
243 // LiveOutCache - Map each basic block where a new register is live out to the
244 // live-out value and its defining block.
245 // One of these conditions shall be true:
247 // 1. !LiveOutCache.count(MBB)
248 // 2. LiveOutCache[MBB].second.getNode() == MBB
249 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
251 // This is only a cache, the values can be computed as:
253 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB))
254 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
256 // The cache is also used as a visited set by extendRange(). It can be shared
257 // by all the new registers because at most one is live out of each block.
258 LiveOutMap LiveOutCache;
260 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid
261 // entry in LiveOutCache.
262 BitVector LiveOutSeen;
264 /// LiveInBlock - Info for updateSSA() about a block where a register is
266 /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA()
267 /// adds the computed live-in value.
269 // Dominator tree node for the block.
270 // Cleared by updateSSA when the final value has been determined.
271 MachineDomTreeNode *DomNode;
273 // Live-in value filled in by updateSSA once it is known.
276 // Position in block where the live-in range ends, or SlotIndex() if the
277 // range passes through the block.
280 LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {}
283 /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and
284 /// updateSSA(). This list is usually empty, it exists here to avoid frequent
286 SmallVector<LiveInBlock, 16> LiveInBlocks;
288 /// defValue - define a value in RegIdx from ParentVNI at Idx.
289 /// Idx does not have to be ParentVNI->def, but it must be contained within
290 /// ParentVNI's live range in ParentLI. The new value is added to the value
292 /// Return the new LI value.
293 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx);
295 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless
296 /// of the number of defs.
297 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI);
299 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
300 /// rematerialization or a COPY from parent. Return the new value.
301 VNInfo *defFromParent(unsigned RegIdx,
304 MachineBasicBlock &MBB,
305 MachineBasicBlock::iterator I);
307 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx.
308 /// Insert PHIDefs as needed to preserve SSA form.
309 void extendRange(unsigned RegIdx, SlotIndex Idx);
311 /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all
312 /// reaching defs for LI are found.
313 /// @param LI Live interval whose value is needed.
314 /// @param MBB Block where LI should be live-in.
315 /// @param Kill Kill point in MBB.
316 /// @return Unique value seen, or NULL.
317 VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB,
320 /// updateSSA - Compute and insert PHIDefs such that all blocks in
321 // LiveInBlocks get a known live-in value. Add live ranges to the blocks.
324 /// transferValues - Transfer values to the new ranges.
325 /// Return true if any ranges were skipped.
326 bool transferValues();
328 /// extendPHIKillRanges - Extend the ranges of all values killed by original
330 void extendPHIKillRanges();
332 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
333 void rewriteAssigned(bool ExtendRanges);
335 /// deleteRematVictims - Delete defs that are dead after rematerializing.
336 void deleteRematVictims();
339 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
340 /// Newly created intervals will be appended to newIntervals.
341 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
342 MachineDominatorTree&);
344 /// reset - Prepare for a new split.
345 void reset(LiveRangeEdit&);
347 /// Create a new virtual register and live interval.
348 /// Return the interval index, starting from 1. Interval index 0 is the
349 /// implicit complement interval.
352 /// currentIntv - Return the current interval index.
353 unsigned currentIntv() const { return OpenIdx; }
355 /// selectIntv - Select a previously opened interval index.
356 void selectIntv(unsigned Idx);
358 /// enterIntvBefore - Enter the open interval before the instruction at Idx.
359 /// If the parent interval is not live before Idx, a COPY is not inserted.
360 /// Return the beginning of the new live range.
361 SlotIndex enterIntvBefore(SlotIndex Idx);
363 /// enterIntvAtEnd - Enter the open interval at the end of MBB.
364 /// Use the open interval from he inserted copy to the MBB end.
365 /// Return the beginning of the new live range.
366 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
368 /// useIntv - indicate that all instructions in MBB should use OpenLI.
369 void useIntv(const MachineBasicBlock &MBB);
371 /// useIntv - indicate that all instructions in range should use OpenLI.
372 void useIntv(SlotIndex Start, SlotIndex End);
374 /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
375 /// Return the end of the live range.
376 SlotIndex leaveIntvAfter(SlotIndex Idx);
378 /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
379 /// Return the end of the live range.
380 SlotIndex leaveIntvBefore(SlotIndex Idx);
382 /// leaveIntvAtTop - Leave the interval at the top of MBB.
383 /// Add liveness from the MBB top to the copy.
384 /// Return the end of the live range.
385 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
387 /// overlapIntv - Indicate that all instructions in range should use the open
388 /// interval, but also let the complement interval be live.
390 /// This doubles the register pressure, but is sometimes required to deal with
391 /// register uses after the last valid split point.
393 /// The Start index should be a return value from a leaveIntv* call, and End
394 /// should be in the same basic block. The parent interval must have the same
395 /// value across the range.
397 void overlapIntv(SlotIndex Start, SlotIndex End);
399 /// finish - after all the new live ranges have been created, compute the
400 /// remaining live range, and rewrite instructions to use the new registers.
401 /// @param LRMap When not null, this vector will map each live range in Edit
402 /// back to the indices returned by openIntv.
403 /// There may be extra indices created by dead code elimination.
404 void finish(SmallVectorImpl<unsigned> *LRMap = 0);
406 /// dump - print the current interval maping to dbgs().
409 // ===--- High level methods ---===
411 /// splitSingleBlock - Split CurLI into a separate live interval around the
412 /// uses in a single block. This is intended to be used as part of a larger
413 /// split, and doesn't call finish().
414 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI);
416 /// splitSingleBlocks - Split CurLI into a separate live interval inside each
417 /// basic block in Blocks.
418 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);