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 // Sorted slot indexes of using instructions.
54 SmallVector<SlotIndex, 8> UseSlots;
56 /// Additional information about basic blocks where the current variable is
57 /// live. Such a block will look like one of these templates:
59 /// 1. | o---x | Internal to block. Variable is only live in this block.
60 /// 2. |---x | Live-in, kill.
61 /// 3. | o---| Def, live-out.
62 /// 4. |---x o---| Live-in, kill, def, live-out.
63 /// 5. |---o---o---| Live-through with uses or defs.
64 /// 6. |-----------| Live-through without uses. Transparent.
67 MachineBasicBlock *MBB;
68 SlotIndex FirstUse; ///< First instr using current reg.
69 SlotIndex LastUse; ///< Last instr using current reg.
70 SlotIndex Kill; ///< Interval end point inside block.
71 SlotIndex Def; ///< Interval start point inside block.
72 bool Uses; ///< Current reg has uses or defs in 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.
78 /// Basic blocks where var is live. This array is parallel to
80 SmallVector<BlockInfo, 8> LiveBlocks;
83 // Current live interval.
84 const LiveInterval *CurLI;
86 /// LastSplitPoint - Last legal split point in each basic block in the current
87 /// function. The first entry is the first terminator, the second entry is the
88 /// last valid split point for a variable that is live in to a landing pad
90 SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint;
92 SlotIndex computeLastSplitPoint(unsigned Num);
94 // Sumarize statistics by counting instructions using CurLI.
97 /// calcLiveBlockInfo - Compute per-block information about CurLI.
98 bool calcLiveBlockInfo();
101 SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
102 const MachineLoopInfo &mli);
104 /// analyze - set CurLI to the specified interval, and analyze how it may be
106 void analyze(const LiveInterval *li);
108 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
112 /// getParent - Return the last analyzed interval.
113 const LiveInterval &getParent() const { return *CurLI; }
115 /// getLastSplitPoint - Return that base index of the last valid split point
116 /// in the basic block numbered Num.
117 SlotIndex getLastSplitPoint(unsigned Num) {
118 // Inline the common simple case.
119 if (LastSplitPoint[Num].first.isValid() &&
120 !LastSplitPoint[Num].second.isValid())
121 return LastSplitPoint[Num].first;
122 return computeLastSplitPoint(Num);
125 /// isOriginalEndpoint - Return true if the original live range was killed or
126 /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def,
127 /// and 'use' for an early-clobber def.
128 /// This can be used to recognize code inserted by earlier live range
130 bool isOriginalEndpoint(SlotIndex Idx) const;
132 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
134 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
135 /// having CurLI split to a new live interval. Return true if Blocks can be
136 /// passed to SplitEditor::splitSingleBlocks.
137 bool getMultiUseBlocks(BlockPtrSet &Blocks);
141 /// SplitEditor - Edit machine code and LiveIntervals for live range
144 /// - Create a SplitEditor from a SplitAnalysis.
145 /// - Start a new live interval with openIntv.
146 /// - Mark the places where the new interval is entered using enterIntv*
147 /// - Mark the ranges where the new interval is used with useIntv*
148 /// - Mark the places where the interval is exited with exitIntv*.
149 /// - Finish the current interval with closeIntv and repeat from 2.
150 /// - Rewrite instructions with finish().
156 MachineRegisterInfo &MRI;
157 MachineDominatorTree &MDT;
158 const TargetInstrInfo &TII;
159 const TargetRegisterInfo &TRI;
161 /// Edit - The current parent register and new intervals created.
164 /// Index into Edit of the currently open interval.
165 /// The index 0 is used for the complement, so the first interval started by
166 /// openIntv will be 1.
169 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
171 /// Allocator for the interval map. This will eventually be shared with
172 /// SlotIndexes and LiveIntervals.
173 RegAssignMap::Allocator Allocator;
175 /// RegAssign - Map of the assigned register indexes.
176 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
178 RegAssignMap RegAssign;
180 typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap;
182 /// Values - keep track of the mapping from parent values to values in the new
183 /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains:
185 /// 1. No entry - the value is not mapped to Edit.get(RegIdx).
186 /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx).
187 /// Each value is represented by a minimal live range at its def.
188 /// 3. A non-null VNInfo - the value is mapped to a single new value.
189 /// The new value has no live ranges anywhere.
192 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
193 typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap;
195 // LiveOutCache - Map each basic block where a new register is live out to the
196 // live-out value and its defining block.
197 // One of these conditions shall be true:
199 // 1. !LiveOutCache.count(MBB)
200 // 2. LiveOutCache[MBB].second.getNode() == MBB
201 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
203 // This is only a cache, the values can be computed as:
205 // VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB))
206 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
208 // The cache is also used as a visited set by extendRange(). It can be shared
209 // by all the new registers because at most one is live out of each block.
210 LiveOutMap LiveOutCache;
212 // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid
213 // entry in LiveOutCache.
214 BitVector LiveOutSeen;
216 /// defValue - define a value in RegIdx from ParentVNI at Idx.
217 /// Idx does not have to be ParentVNI->def, but it must be contained within
218 /// ParentVNI's live range in ParentLI. The new value is added to the value
220 /// Return the new LI value.
221 VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx);
223 /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless
224 /// of the number of defs.
225 void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI);
227 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
228 /// rematerialization or a COPY from parent. Return the new value.
229 VNInfo *defFromParent(unsigned RegIdx,
232 MachineBasicBlock &MBB,
233 MachineBasicBlock::iterator I);
235 /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx.
236 /// Insert PHIDefs as needed to preserve SSA form.
237 void extendRange(unsigned RegIdx, SlotIndex Idx);
239 /// updateSSA - Insert PHIDefs as necessary and update LiveOutCache such that
240 /// Edit.get(RegIdx) is live-in to all the blocks in LiveIn.
241 /// Return the value that is eventually live-in to IdxMBB.
242 VNInfo *updateSSA(unsigned RegIdx,
243 SmallVectorImpl<MachineDomTreeNode*> &LiveIn,
245 const MachineBasicBlock *IdxMBB);
247 /// transferSimpleValues - Transfer simply defined values to the new ranges.
248 /// Return true if any complex ranges were skipped.
249 bool transferSimpleValues();
251 /// extendPHIKillRanges - Extend the ranges of all values killed by original
253 void extendPHIKillRanges();
255 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
256 void rewriteAssigned(bool ExtendRanges);
258 /// deleteRematVictims - Delete defs that are dead after rematerializing.
259 void deleteRematVictims();
262 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
263 /// Newly created intervals will be appended to newIntervals.
264 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
265 MachineDominatorTree&);
267 /// reset - Prepare for a new split.
268 void reset(LiveRangeEdit&);
270 /// Create a new virtual register and live interval.
273 /// enterIntvBefore - Enter the open interval before the instruction at Idx.
274 /// If the parent interval is not live before Idx, a COPY is not inserted.
275 /// Return the beginning of the new live range.
276 SlotIndex enterIntvBefore(SlotIndex Idx);
278 /// enterIntvAtEnd - Enter the open interval at the end of MBB.
279 /// Use the open interval from he inserted copy to the MBB end.
280 /// Return the beginning of the new live range.
281 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
283 /// useIntv - indicate that all instructions in MBB should use OpenLI.
284 void useIntv(const MachineBasicBlock &MBB);
286 /// useIntv - indicate that all instructions in range should use OpenLI.
287 void useIntv(SlotIndex Start, SlotIndex End);
289 /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
290 /// Return the end of the live range.
291 SlotIndex leaveIntvAfter(SlotIndex Idx);
293 /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
294 /// Return the end of the live range.
295 SlotIndex leaveIntvBefore(SlotIndex Idx);
297 /// leaveIntvAtTop - Leave the interval at the top of MBB.
298 /// Add liveness from the MBB top to the copy.
299 /// Return the end of the live range.
300 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
302 /// overlapIntv - Indicate that all instructions in range should use the open
303 /// interval, but also let the complement interval be live.
305 /// This doubles the register pressure, but is sometimes required to deal with
306 /// register uses after the last valid split point.
308 /// The Start index should be a return value from a leaveIntv* call, and End
309 /// should be in the same basic block. The parent interval must have the same
310 /// value across the range.
312 void overlapIntv(SlotIndex Start, SlotIndex End);
314 /// closeIntv - Indicate that we are done editing the currently open
315 /// LiveInterval, and ranges can be trimmed.
318 /// finish - after all the new live ranges have been created, compute the
319 /// remaining live range, and rewrite instructions to use the new registers.
322 /// dump - print the current interval maping to dbgs().
325 // ===--- High level methods ---===
327 /// splitSingleBlocks - Split CurLI into a separate live interval inside each
328 /// basic block in Blocks.
329 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);