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/BitVector.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/IndexedMap.h"
18 #include "llvm/ADT/IntervalMap.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/CodeGen/SlotIndexes.h"
24 class ConnectedVNInfoEqClasses;
29 class MachineLoopInfo;
30 class MachineRegisterInfo;
31 class TargetInstrInfo;
32 class TargetRegisterInfo;
37 /// At some point we should just include MachineDominators.h:
38 class MachineDominatorTree;
39 template <class NodeT> class DomTreeNodeBase;
40 typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
43 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
47 const MachineFunction &MF;
48 const VirtRegMap &VRM;
49 const LiveIntervals &LIS;
50 const MachineLoopInfo &Loops;
51 const TargetInstrInfo &TII;
53 // Instructions using the the current register.
54 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
55 InstrPtrSet UsingInstrs;
57 // Sorted slot indexes of using instructions.
58 SmallVector<SlotIndex, 8> UseSlots;
60 // The number of instructions using CurLI in each basic block.
61 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
62 BlockCountMap UsingBlocks;
64 /// Additional information about basic blocks where the current variable is
65 /// live. Such a block will look like one of these templates:
67 /// 1. | o---x | Internal to block. Variable is only live in this block.
68 /// 2. |---x | Live-in, kill.
69 /// 3. | o---| Def, live-out.
70 /// 4. |---x o---| Live-in, kill, def, live-out.
71 /// 5. |---o---o---| Live-through with uses or defs.
72 /// 6. |-----------| Live-through without uses. Transparent.
75 MachineBasicBlock *MBB;
76 SlotIndex FirstUse; ///< First instr using current reg.
77 SlotIndex LastUse; ///< Last instr using current reg.
78 SlotIndex Kill; ///< Interval end point inside block.
79 SlotIndex Def; ///< Interval start point inside block.
80 /// Last possible point for splitting live ranges.
81 SlotIndex LastSplitPoint;
82 bool Uses; ///< Current reg has uses or defs in block.
83 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above).
84 bool LiveIn; ///< Current reg is live in.
85 bool LiveOut; ///< Current reg is live out.
88 /// Basic blocks where var is live. This array is parallel to
90 SmallVector<BlockInfo, 8> LiveBlocks;
93 // Current live interval.
94 const LiveInterval *CurLI;
96 // Sumarize statistics by counting instructions using CurLI.
99 /// calcLiveBlockInfo - Compute per-block information about CurLI.
100 bool calcLiveBlockInfo();
102 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be
104 bool canAnalyzeBranch(const MachineBasicBlock *MBB);
107 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
108 const MachineLoopInfo &mli);
110 /// analyze - set CurLI to the specified interval, and analyze how it may be
112 void analyze(const LiveInterval *li);
114 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
118 /// getParent - Return the last analyzed interval.
119 const LiveInterval &getParent() const { return *CurLI; }
121 /// hasUses - Return true if MBB has any uses of CurLI.
122 bool hasUses(const MachineBasicBlock *MBB) const {
123 return UsingBlocks.lookup(MBB);
126 /// isOriginalEndpoint - Return true if the original live range was killed or
127 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def,
128 /// and 'use' for an early-clobber def.
129 /// This can be used to recognize code inserted by earlier live range
131 bool isOriginalEndpoint(SlotIndex Idx) const;
133 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
135 // Print a set of blocks with use counts.
136 void print(const BlockPtrSet&, raw_ostream&) const;
138 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
139 /// having CurLI split to a new live interval. Return true if Blocks can be
140 /// passed to SplitEditor::splitSingleBlocks.
141 bool getMultiUseBlocks(BlockPtrSet &Blocks);
145 /// SplitEditor - Edit machine code and LiveIntervals for live range
148 /// - Create a SplitEditor from a SplitAnalysis.
149 /// - Start a new live interval with openIntv.
150 /// - Mark the places where the new interval is entered using enterIntv*
151 /// - Mark the ranges where the new interval is used with useIntv*
152 /// - Mark the places where the interval is exited with exitIntv*.
153 /// - Finish the current interval with closeIntv and repeat from 2.
154 /// - Rewrite instructions with finish().
160 MachineRegisterInfo &MRI;
161 MachineDominatorTree &MDT;
162 const TargetInstrInfo &TII;
163 const TargetRegisterInfo &TRI;
165 /// Edit - The current parent register and new intervals created.
168 /// Index into Edit of the currently open interval.
169 /// The index 0 is used for the complement, so the first interval started by
170 /// openIntv will be 1.
173 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
175 /// Allocator for the interval map. This will eventually be shared with
176 /// SlotIndexes and LiveIntervals.
177 RegAssignMap::Allocator Allocator;
179 /// RegAssign - Map of the assigned register indexes.
180 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
182 RegAssignMap RegAssign;
184 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap;
186 /// Values - keep track of the mapping from parent values to values in the new
187 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains:
189 /// 1. No entry - the value is not mapped to Edit.get(RegIdx).
190 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx).
191 /// Each value is represented by a minimal live range at its def.
192 /// 3. A non-null VNInfo - the value is mapped to a single new value.
193 /// The new value has no live ranges anywhere.
196 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
197 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap;
199 // LiveOutCache - Map each basic block where a new register is live out to the
200 // live-out value and its defining block.
201 // One of these conditions shall be true:
203 // 1. !LiveOutCache.count(MBB)
204 // 2. LiveOutCache[MBB].second.getNode() == MBB
205 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
207 // This is only a cache, the values can be computed as:
209 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB))
210 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
212 // The cache is also used as a visited set by extendRange(). It can be shared
213 // by all the new registers because at most one is live out of each block.
214 LiveOutMap LiveOutCache;
216 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid
217 // entry in LiveOutCache.
218 BitVector LiveOutSeen;
220 /// defValue - define a value in RegIdx from ParentVNI at Idx.
221 /// Idx does not have to be ParentVNI->def, but it must be contained within
222 /// ParentVNI's live range in ParentLI. The new value is added to the value
224 /// Return the new LI value.
225 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx);
227 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless
228 /// of the number of defs.
229 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI);
231 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
232 /// rematerialization or a COPY from parent. Return the new value.
233 VNInfo *defFromParent(unsigned RegIdx,
236 MachineBasicBlock &MBB,
237 MachineBasicBlock::iterator I);
239 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx.
240 /// Insert PHIDefs as needed to preserve SSA form.
241 void extendRange(unsigned RegIdx, SlotIndex Idx);
243 /// updateSSA - Insert PHIDefs as necessary and update LiveOutCache such that
244 /// Edit.get(RegIdx) is live-in to all the blocks in LiveIn.
245 /// Return the value that is eventually live-in to IdxMBB.
246 VNInfo *updateSSA(unsigned RegIdx,
247 SmallVectorImpl<MachineDomTreeNode*> &LiveIn,
249 const MachineBasicBlock *IdxMBB);
251 /// transferSimpleValues - Transfer simply defined values to the new ranges.
252 /// Return true if any complex ranges were skipped.
253 bool transferSimpleValues();
255 /// extendPHIKillRanges - Extend the ranges of all values killed by original
257 void extendPHIKillRanges();
259 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
260 void rewriteAssigned(bool ExtendRanges);
262 /// deleteRematVictims - Delete defs that are dead after rematerializing.
263 void deleteRematVictims();
266 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
267 /// Newly created intervals will be appended to newIntervals.
268 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
269 MachineDominatorTree&);
271 /// reset - Prepare for a new split.
272 void reset(LiveRangeEdit&);
274 /// Create a new virtual register and live interval.
277 /// enterIntvBefore - Enter the open interval before the instruction at Idx.
278 /// If the parent interval is not live before Idx, a COPY is not inserted.
279 /// Return the beginning of the new live range.
280 SlotIndex enterIntvBefore(SlotIndex Idx);
282 /// enterIntvAtEnd - Enter the open interval at the end of MBB.
283 /// Use the open interval from he inserted copy to the MBB end.
284 /// Return the beginning of the new live range.
285 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
287 /// useIntv - indicate that all instructions in MBB should use OpenLI.
288 void useIntv(const MachineBasicBlock &MBB);
290 /// useIntv - indicate that all instructions in range should use OpenLI.
291 void useIntv(SlotIndex Start, SlotIndex End);
293 /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
294 /// Return the end of the live range.
295 SlotIndex leaveIntvAfter(SlotIndex Idx);
297 /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
298 /// Return the end of the live range.
299 SlotIndex leaveIntvBefore(SlotIndex Idx);
301 /// leaveIntvAtTop - Leave the interval at the top of MBB.
302 /// Add liveness from the MBB top to the copy.
303 /// Return the end of the live range.
304 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
306 /// overlapIntv - Indicate that all instructions in range should use the open
307 /// interval, but also let the complement interval be live.
309 /// This doubles the register pressure, but is sometimes required to deal with
310 /// register uses after the last valid split point.
312 /// The Start index should be a return value from a leaveIntv* call, and End
313 /// should be in the same basic block. The parent interval must have the same
314 /// value across the range.
316 void overlapIntv(SlotIndex Start, SlotIndex End);
318 /// closeIntv - Indicate that we are done editing the currently open
319 /// LiveInterval, and ranges can be trimmed.
322 /// finish - after all the new live ranges have been created, compute the
323 /// remaining live range, and rewrite instructions to use the new registers.
326 /// dump - print the current interval maping to dbgs().
329 // ===--- High level methods ---===
331 /// splitSingleBlocks - Split CurLI into a separate live interval inside each
332 /// basic block in Blocks.
333 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);