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/DenseMap.h"
16 #include "llvm/ADT/IntervalMap.h"
17 #include "llvm/ADT/SmallPtrSet.h"
18 #include "llvm/CodeGen/SlotIndexes.h"
22 class ConnectedVNInfoEqClasses;
27 class MachineLoopInfo;
28 class MachineRegisterInfo;
29 class TargetInstrInfo;
30 class TargetRegisterInfo;
35 /// At some point we should just include MachineDominators.h:
36 class MachineDominatorTree;
37 template <class NodeT> class DomTreeNodeBase;
38 typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
41 /// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
45 const MachineFunction &MF;
46 const LiveIntervals &LIS;
47 const MachineLoopInfo &Loops;
48 const TargetInstrInfo &TII;
50 // Instructions using the the current register.
51 typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
52 InstrPtrSet UsingInstrs;
54 // Sorted slot indexes of using instructions.
55 SmallVector<SlotIndex, 8> UseSlots;
57 // The number of instructions using CurLI in each basic block.
58 typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
59 BlockCountMap UsingBlocks;
61 /// Additional information about basic blocks where the current variable is
62 /// live. Such a block will look like one of these templates:
64 /// 1. | o---x | Internal to block. Variable is only live in this block.
65 /// 2. |---x | Live-in, kill.
66 /// 3. | o---| Def, live-out.
67 /// 4. |---x o---| Live-in, kill, def, live-out.
68 /// 5. |---o---o---| Live-through with uses or defs.
69 /// 6. |-----------| Live-through without uses. Transparent.
72 MachineBasicBlock *MBB;
73 SlotIndex FirstUse; ///< First instr using current reg.
74 SlotIndex LastUse; ///< Last instr using current reg.
75 SlotIndex Kill; ///< Interval end point inside block.
76 SlotIndex Def; ///< Interval start point inside block.
77 /// Last possible point for splitting live ranges.
78 SlotIndex LastSplitPoint;
79 bool Uses; ///< Current reg has uses or defs in block.
80 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above).
81 bool LiveIn; ///< Current reg is live in.
82 bool LiveOut; ///< Current reg is live out.
84 // Per-interference pattern scratch data.
85 bool OverlapEntry; ///< Interference overlaps entering interval.
86 bool OverlapExit; ///< Interference overlaps exiting interval.
89 /// Basic blocks where var is live. This array is parallel to
91 SmallVector<BlockInfo, 8> LiveBlocks;
94 // Current live interval.
95 const LiveInterval *CurLI;
97 // Sumarize statistics by counting instructions using CurLI.
100 /// calcLiveBlockInfo - Compute per-block information about CurLI.
101 void calcLiveBlockInfo();
103 /// canAnalyzeBranch - Return true if MBB ends in a branch that can be
105 bool canAnalyzeBranch(const MachineBasicBlock *MBB);
108 SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis,
109 const MachineLoopInfo &mli);
111 /// analyze - set CurLI to the specified interval, and analyze how it may be
113 void analyze(const LiveInterval *li);
115 /// clear - clear all data structures so SplitAnalysis is ready to analyze a
119 /// getParent - Return the last analyzed interval.
120 const LiveInterval &getParent() const { return *CurLI; }
122 /// hasUses - Return true if MBB has any uses of CurLI.
123 bool hasUses(const MachineBasicBlock *MBB) const {
124 return UsingBlocks.lookup(MBB);
127 typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
129 // Print a set of blocks with use counts.
130 void print(const BlockPtrSet&, raw_ostream&) const;
132 /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
133 /// having CurLI split to a new live interval. Return true if Blocks can be
134 /// passed to SplitEditor::splitSingleBlocks.
135 bool getMultiUseBlocks(BlockPtrSet &Blocks);
137 /// getBlockForInsideSplit - If CurLI is contained inside a single basic
138 /// block, and it would pay to subdivide the interval inside that block,
139 /// return it. Otherwise return NULL. The returned block can be passed to
140 /// SplitEditor::splitInsideBlock.
141 const MachineBasicBlock *getBlockForInsideSplit();
145 /// LiveIntervalMap - Map values from a large LiveInterval into a small
146 /// interval that is a subset. Insert phi-def values as needed. This class is
147 /// used by SplitEditor to create new smaller LiveIntervals.
149 /// ParentLI is the larger interval, LI is the subset interval. Every value
150 /// in LI corresponds to exactly one value in ParentLI, and the live range
151 /// of the value is contained within the live range of the ParentLI value.
152 /// Values in ParentLI may map to any number of OpenLI values, including 0.
153 class LiveIntervalMap {
155 MachineDominatorTree &MDT;
157 // The parent interval is never changed.
158 const LiveInterval &ParentLI;
160 // The child interval's values are fully contained inside ParentLI values.
163 typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
165 // Map ParentLI values to simple values in LI that are defined at the same
166 // SlotIndex, or NULL for ParentLI values that have complex LI defs.
167 // Note there is a difference between values mapping to NULL (complex), and
168 // values not present (unknown/unmapped).
171 typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
172 typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap;
174 // LiveOutCache - Map each basic block where LI is live out to the live-out
175 // value and its defining block. One of these conditions shall be true:
177 // 1. !LiveOutCache.count(MBB)
178 // 2. LiveOutCache[MBB].second.getNode() == MBB
179 // 3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
181 // This is only a cache, the values can be computed as:
183 // VNI = LI->getVNInfoAt(LIS.getMBBEndIdx(MBB))
184 // Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
186 // The cache is also used as a visiteed set by mapValue().
187 LiveOutMap LiveOutCache;
189 // Dump the live-out cache to dbgs().
193 LiveIntervalMap(LiveIntervals &lis,
194 MachineDominatorTree &mdt,
195 const LiveInterval &parentli)
196 : LIS(lis), MDT(mdt), ParentLI(parentli), LI(0) {}
198 /// reset - clear all data structures and start a new live interval.
199 void reset(LiveInterval *);
201 /// getLI - return the current live interval.
202 LiveInterval *getLI() const { return LI; }
204 /// defValue - define a value in LI from the ParentLI value VNI and Idx.
205 /// Idx does not have to be ParentVNI->def, but it must be contained within
206 /// ParentVNI's live range in ParentLI.
207 /// Return the new LI value.
208 VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
210 /// mapValue - map ParentVNI to the corresponding LI value at Idx. It is
211 /// assumed that ParentVNI is live at Idx.
212 /// If ParentVNI has not been defined by defValue, it is assumed that
213 /// ParentVNI->def dominates Idx.
214 /// If ParentVNI has been defined by defValue one or more times, a value that
215 /// dominates Idx will be returned. This may require creating extra phi-def
216 /// values and adding live ranges to LI.
217 /// If simple is not NULL, *simple will indicate if ParentVNI is a simply
219 VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0);
221 // extendTo - Find the last LI value defined in MBB at or before Idx. The
222 // parentli is assumed to be live at Idx. Extend the live range to include
223 // Idx. Return the found VNInfo, or NULL.
224 VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx);
226 /// isMapped - Return true is ParentVNI is a known mapped value. It may be a
227 /// simple 1-1 mapping or a complex mapping to later defs.
228 bool isMapped(const VNInfo *ParentVNI) const {
229 return Values.count(ParentVNI);
232 /// isComplexMapped - Return true if ParentVNI has received new definitions
234 bool isComplexMapped(const VNInfo *ParentVNI) const;
236 /// markComplexMapped - Mark ParentVNI as complex mapped regardless of the
237 /// number of definitions.
238 void markComplexMapped(const VNInfo *ParentVNI) { Values[ParentVNI] = 0; }
240 // addSimpleRange - Add a simple range from ParentLI to LI.
241 // ParentVNI must be live in the [Start;End) interval.
242 void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
244 /// addRange - Add live ranges to LI where [Start;End) intersects ParentLI.
245 /// All needed values whose def is not inside [Start;End) must be defined
246 /// beforehand so mapValue will work.
247 void addRange(SlotIndex Start, SlotIndex End);
251 /// SplitEditor - Edit machine code and LiveIntervals for live range
254 /// - Create a SplitEditor from a SplitAnalysis.
255 /// - Start a new live interval with openIntv.
256 /// - Mark the places where the new interval is entered using enterIntv*
257 /// - Mark the ranges where the new interval is used with useIntv*
258 /// - Mark the places where the interval is exited with exitIntv*.
259 /// - Finish the current interval with closeIntv and repeat from 2.
260 /// - Rewrite instructions with finish().
266 MachineRegisterInfo &MRI;
267 MachineDominatorTree &MDT;
268 const TargetInstrInfo &TII;
269 const TargetRegisterInfo &TRI;
271 /// Edit - The current parent register and new intervals created.
274 /// Index into Edit of the currently open interval.
275 /// The index 0 is used for the complement, so the first interval started by
276 /// openIntv will be 1.
279 typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
281 /// Allocator for the interval map. This will eventually be shared with
282 /// SlotIndexes and LiveIntervals.
283 RegAssignMap::Allocator Allocator;
285 /// RegAssign - Map of the assigned register indexes.
286 /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
288 RegAssignMap RegAssign;
290 /// LIMappers - One LiveIntervalMap or each interval in Edit.
291 SmallVector<LiveIntervalMap, 4> LIMappers;
293 /// defFromParent - Define Reg from ParentVNI at UseIdx using either
294 /// rematerialization or a COPY from parent. Return the new value.
295 VNInfo *defFromParent(unsigned RegIdx,
298 MachineBasicBlock &MBB,
299 MachineBasicBlock::iterator I);
301 /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
302 void rewriteAssigned();
304 /// rewriteComponents - Rewrite all uses of Intv[0] according to the eq
305 /// classes in ConEQ.
306 /// This must be done when Intvs[0] is styill live at all uses, before calling
307 /// ConEq.Distribute().
308 void rewriteComponents(const SmallVectorImpl<LiveInterval*> &Intvs,
309 const ConnectedVNInfoEqClasses &ConEq);
312 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
313 /// Newly created intervals will be appended to newIntervals.
314 SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
315 MachineDominatorTree&, LiveRangeEdit&);
317 /// getAnalysis - Get the corresponding analysis.
318 SplitAnalysis &getAnalysis() { return SA; }
320 /// Create a new virtual register and live interval.
323 /// enterIntvBefore - Enter the open interval before the instruction at Idx.
324 /// If the parent interval is not live before Idx, a COPY is not inserted.
325 /// Return the beginning of the new live range.
326 SlotIndex enterIntvBefore(SlotIndex Idx);
328 /// enterIntvAtEnd - Enter the open interval at the end of MBB.
329 /// Use the open interval from he inserted copy to the MBB end.
330 /// Return the beginning of the new live range.
331 SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
333 /// useIntv - indicate that all instructions in MBB should use OpenLI.
334 void useIntv(const MachineBasicBlock &MBB);
336 /// useIntv - indicate that all instructions in range should use OpenLI.
337 void useIntv(SlotIndex Start, SlotIndex End);
339 /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
340 /// Return the end of the live range.
341 SlotIndex leaveIntvAfter(SlotIndex Idx);
343 /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
344 /// Return the end of the live range.
345 SlotIndex leaveIntvBefore(SlotIndex Idx);
347 /// leaveIntvAtTop - Leave the interval at the top of MBB.
348 /// Add liveness from the MBB top to the copy.
349 /// Return the end of the live range.
350 SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
352 /// overlapIntv - Indicate that all instructions in range should use the open
353 /// interval, but also let the complement interval be live.
355 /// This doubles the register pressure, but is sometimes required to deal with
356 /// register uses after the last valid split point.
358 /// The Start index should be a return value from a leaveIntv* call, and End
359 /// should be in the same basic block. The parent interval must have the same
360 /// value across the range.
362 void overlapIntv(SlotIndex Start, SlotIndex End);
364 /// closeIntv - Indicate that we are done editing the currently open
365 /// LiveInterval, and ranges can be trimmed.
368 /// finish - after all the new live ranges have been created, compute the
369 /// remaining live range, and rewrite instructions to use the new registers.
372 /// dump - print the current interval maping to dbgs().
375 // ===--- High level methods ---===
377 /// splitSingleBlocks - Split CurLI into a separate live interval inside each
378 /// basic block in Blocks.
379 void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
381 /// splitInsideBlock - Split CurLI into multiple intervals inside MBB.
382 void splitInsideBlock(const MachineBasicBlock *);