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/ArrayRef.h"
16 #include "llvm/ADT/BitVector.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/IndexedMap.h"
19 #include "llvm/ADT/IntervalMap.h"
20 #include "llvm/ADT/SmallPtrSet.h"
21 #include "llvm/CodeGen/SlotIndexes.h"
25 class ConnectedVNInfoEqClasses;
30 class MachineLoopInfo;
31 class MachineRegisterInfo;
32 class TargetInstrInfo;
33 class TargetRegisterInfo;
38 /// At some point we should just include MachineDominators.h:
39 class MachineDominatorTree;
40 template <class NodeT> class DomTreeNodeBase;
41 typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
44 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
48 const MachineFunction &MF;
49 const VirtRegMap &VRM;
50 const LiveIntervals &LIS;
51 const MachineLoopInfo &Loops;
52 const TargetInstrInfo &TII;
54 // Sorted slot indexes of using instructions.
55 SmallVector<SlotIndex, 8> UseSlots;
57 /// Additional information about basic blocks where the current variable is
58 /// live. Such a block will look like one of these templates:
60 /// 1. | o---x | Internal to block. Variable is only live in this block.
61 /// 2. |---x | Live-in, kill.
62 /// 3. | o---| Def, live-out.
63 /// 4. |---x o---| Live-in, kill, def, live-out.
64 /// 5. |---o---o---| Live-through with uses or defs.
65 /// 6. |-----------| Live-through without uses. Transparent.
68 MachineBasicBlock *MBB;
69 SlotIndex FirstUse; ///< First instr using current reg.
70 SlotIndex LastUse; ///< Last instr using current reg.
71 SlotIndex Kill; ///< Interval end point inside block.
72 SlotIndex Def; ///< Interval start point inside block.
73 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above).
74 bool LiveIn; ///< Current reg is live in.
75 bool LiveOut; ///< Current reg is live out.
79 // Current live interval.
80 const LiveInterval *CurLI;
82 /// LastSplitPoint - Last legal split point in each basic block in the current
83 /// function. The first entry is the first terminator, the second entry is the
84 /// last valid split point for a variable that is live in to a landing pad
86 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint;
88 /// UseBlocks - Blocks where CurLI has uses.
89 SmallVector<BlockInfo, 8> UseBlocks;
91 /// ThroughBlocks - Block numbers where CurLI is live through without uses.
92 BitVector ThroughBlocks;
94 /// NumThroughBlocks - Number of live-through blocks.
95 unsigned NumThroughBlocks;
97 SlotIndex computeLastSplitPoint(unsigned Num);
99 // Sumarize statistics by counting instructions using CurLI.
102 /// calcLiveBlockInfo - Compute per-block information about CurLI.
103 bool calcLiveBlockInfo();
106 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
107 const MachineLoopInfo &mli);
109 /// analyze - set CurLI to the specified interval, and analyze how it may be
111 void analyze(const LiveInterval *li);
113 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
117 /// getParent - Return the last analyzed interval.
118 const LiveInterval &getParent() const { return *CurLI; }
120 /// getLastSplitPoint - Return that base index of the last valid split point
121 /// in the basic block numbered Num.
122 SlotIndex getLastSplitPoint(unsigned Num) {
123 // Inline the common simple case.
124 if (LastSplitPoint[Num].first.isValid() &&
125 !LastSplitPoint[Num].second.isValid())
126 return LastSplitPoint[Num].first;
127 return computeLastSplitPoint(Num);
130 /// isOriginalEndpoint - Return true if the original live range was killed or
131 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def,
132 /// and 'use' for an early-clobber def.
133 /// This can be used to recognize code inserted by earlier live range
135 bool isOriginalEndpoint(SlotIndex Idx) const;
137 /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks
138 /// where CurLI has uses.
139 ArrayRef<BlockInfo> getUseBlocks() { return UseBlocks; }
141 /// getNumThroughBlocks - Return the number of through blocks.
142 unsigned getNumThroughBlocks() const { return NumThroughBlocks; }
144 /// isThroughBlock - Return true if CurLI is live through MBB without uses.
145 bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); }
147 /// getThroughBlocks - Return the set of through blocks.
148 const BitVector &getThroughBlocks() const { return ThroughBlocks; }
150 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
152 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
153 /// having CurLI split to a new live interval. Return true if Blocks can be
154 /// passed to SplitEditor::splitSingleBlocks.
155 bool getMultiUseBlocks(BlockPtrSet &Blocks);
159 /// SplitEditor - Edit machine code and LiveIntervals for live range
162 /// - Create a SplitEditor from a SplitAnalysis.
163 /// - Start a new live interval with openIntv.
164 /// - Mark the places where the new interval is entered using enterIntv*
165 /// - Mark the ranges where the new interval is used with useIntv*
166 /// - Mark the places where the interval is exited with exitIntv*.
167 /// - Finish the current interval with closeIntv and repeat from 2.
168 /// - Rewrite instructions with finish().
174 MachineRegisterInfo &MRI;
175 MachineDominatorTree &MDT;
176 const TargetInstrInfo &TII;
177 const TargetRegisterInfo &TRI;
179 /// Edit - The current parent register and new intervals created.
182 /// Index into Edit of the currently open interval.
183 /// The index 0 is used for the complement, so the first interval started by
184 /// openIntv will be 1.
187 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
189 /// Allocator for the interval map. This will eventually be shared with
190 /// SlotIndexes and LiveIntervals.
191 RegAssignMap::Allocator Allocator;
193 /// RegAssign - Map of the assigned register indexes.
194 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
196 RegAssignMap RegAssign;
198 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap;
200 /// Values - keep track of the mapping from parent values to values in the new
201 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains:
203 /// 1. No entry - the value is not mapped to Edit.get(RegIdx).
204 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx).
205 /// Each value is represented by a minimal live range at its def.
206 /// 3. A non-null VNInfo - the value is mapped to a single new value.
207 /// The new value has no live ranges anywhere.
210 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
211 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap;
213 // LiveOutCache - Map each basic block where a new register is live out to the
214 // live-out value and its defining block.
215 // One of these conditions shall be true:
217 // 1. !LiveOutCache.count(MBB)
218 // 2. LiveOutCache[MBB].second.getNode() == MBB
219 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
221 // This is only a cache, the values can be computed as:
223 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB))
224 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
226 // The cache is also used as a visited set by extendRange(). It can be shared
227 // by all the new registers because at most one is live out of each block.
228 LiveOutMap LiveOutCache;
230 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid
231 // entry in LiveOutCache.
232 BitVector LiveOutSeen;
234 /// LiveInBlock - Info for updateSSA() about a block where a register is
236 /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA()
237 /// adds the computed live-in value.
239 // Dominator tree node for the block.
240 // Cleared by updateSSA when the final value has been determined.
241 MachineDomTreeNode *DomNode;
243 // Live-in value filled in by updateSSA once it is known.
246 // Position in block where the live-in range ends, or SlotIndex() if the
247 // range passes through the block.
250 LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {}
253 /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and
254 /// updateSSA(). This list is usually empty, it exists here to avoid frequent
256 SmallVector<LiveInBlock, 16> LiveInBlocks;
258 /// defValue - define a value in RegIdx from ParentVNI at Idx.
259 /// Idx does not have to be ParentVNI->def, but it must be contained within
260 /// ParentVNI's live range in ParentLI. The new value is added to the value
262 /// Return the new LI value.
263 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx);
265 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless
266 /// of the number of defs.
267 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI);
269 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
270 /// rematerialization or a COPY from parent. Return the new value.
271 VNInfo *defFromParent(unsigned RegIdx,
274 MachineBasicBlock &MBB,
275 MachineBasicBlock::iterator I);
277 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx.
278 /// Insert PHIDefs as needed to preserve SSA form.
279 void extendRange(unsigned RegIdx, SlotIndex Idx);
281 /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all
282 /// reaching defs for LI are found.
283 /// @param LI Live interval whose value is needed.
284 /// @param MBB Block where LI should be live-in.
285 /// @param Kill Kill point in MBB.
286 /// @return Unique value seen, or NULL.
287 VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB,
290 /// updateSSA - Compute and insert PHIDefs such that all blocks in
291 // LiveInBlocks get a known live-in value. Add live ranges to the blocks.
294 /// transferValues - Transfer values to the new ranges.
295 /// Return true if any ranges were skipped.
296 bool transferValues();
298 /// extendPHIKillRanges - Extend the ranges of all values killed by original
300 void extendPHIKillRanges();
302 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
303 void rewriteAssigned(bool ExtendRanges);
305 /// deleteRematVictims - Delete defs that are dead after rematerializing.
306 void deleteRematVictims();
309 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
310 /// Newly created intervals will be appended to newIntervals.
311 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
312 MachineDominatorTree&);
314 /// reset - Prepare for a new split.
315 void reset(LiveRangeEdit&);
317 /// Create a new virtual register and live interval.
318 /// Return the interval index, starting from 1. Interval index 0 is the
319 /// implicit complement interval.
322 /// currentIntv - Return the current interval index.
323 unsigned currentIntv() const { return OpenIdx; }
325 /// selectIntv - Select a previously opened interval index.
326 void selectIntv(unsigned Idx);
328 /// enterIntvBefore - Enter the open interval before the instruction at Idx.
329 /// If the parent interval is not live before Idx, a COPY is not inserted.
330 /// Return the beginning of the new live range.
331 SlotIndex enterIntvBefore(SlotIndex Idx);
333 /// enterIntvAtEnd - Enter the open interval at the end of MBB.
334 /// Use the open interval from he inserted copy to the MBB end.
335 /// Return the beginning of the new live range.
336 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
338 /// useIntv - indicate that all instructions in MBB should use OpenLI.
339 void useIntv(const MachineBasicBlock &MBB);
341 /// useIntv - indicate that all instructions in range should use OpenLI.
342 void useIntv(SlotIndex Start, SlotIndex End);
344 /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
345 /// Return the end of the live range.
346 SlotIndex leaveIntvAfter(SlotIndex Idx);
348 /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
349 /// Return the end of the live range.
350 SlotIndex leaveIntvBefore(SlotIndex Idx);
352 /// leaveIntvAtTop - Leave the interval at the top of MBB.
353 /// Add liveness from the MBB top to the copy.
354 /// Return the end of the live range.
355 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
357 /// overlapIntv - Indicate that all instructions in range should use the open
358 /// interval, but also let the complement interval be live.
360 /// This doubles the register pressure, but is sometimes required to deal with
361 /// register uses after the last valid split point.
363 /// The Start index should be a return value from a leaveIntv* call, and End
364 /// should be in the same basic block. The parent interval must have the same
365 /// value across the range.
367 void overlapIntv(SlotIndex Start, SlotIndex End);
369 /// finish - after all the new live ranges have been created, compute the
370 /// remaining live range, and rewrite instructions to use the new registers.
371 /// @param LRMap When not null, this vector will map each live range in Edit
372 /// back to the indices returned by openIntv.
373 /// There may be extra indices created by dead code elimination.
374 void finish(SmallVectorImpl<unsigned> *LRMap = 0);
376 /// dump - print the current interval maping to dbgs().
379 // ===--- High level methods ---===
381 /// splitSingleBlock - Split CurLI into a separate live interval around the
382 /// uses in a single block. This is intended to be used as part of a larger
383 /// split, and doesn't call finish().
384 void splitSingleBlock(const SplitAnalysis::BlockInfo &BI);
386 /// splitSingleBlocks - Split CurLI into a separate live interval inside each
387 /// basic block in Blocks.
388 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);