SplitKit.cpp revision 2780d3ca8114ae11fb43f61655a5ddde22518fb8 
1//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the SplitAnalysis class as well as mutator functions for
11// live range splitting.
12//
13//===----------------------------------------------------------------------===//
14
15#define DEBUG_TYPE "splitter"
16#include "SplitKit.h"
17#include "VirtRegMap.h"
18#include "llvm/CodeGen/CalcSpillWeights.h"
19#include "llvm/CodeGen/LiveIntervalAnalysis.h"
20#include "llvm/CodeGen/MachineFunctionPass.h"
21#include "llvm/CodeGen/MachineInstrBuilder.h"
22#include "llvm/CodeGen/MachineLoopInfo.h"
23#include "llvm/CodeGen/MachineRegisterInfo.h"
24#include "llvm/Support/CommandLine.h"
25#include "llvm/Support/Debug.h"
26#include "llvm/Support/raw_ostream.h"
27#include "llvm/Target/TargetInstrInfo.h"
28#include "llvm/Target/TargetMachine.h"
29
30using namespace llvm;
31
32static cl::opt<bool>
33AllowSplit("spiller-splits-edges",
34           cl::desc("Allow critical edge splitting during spilling"));
35
36//===----------------------------------------------------------------------===//
37//                                 Split Analysis
38//===----------------------------------------------------------------------===//
39
40SplitAnalysis::SplitAnalysis(const MachineFunction &mf,
41                             const LiveIntervals &lis,
42                             const MachineLoopInfo &mli)
43  : mf_(mf),
44    lis_(lis),
45    loops_(mli),
46    tii_(*mf.getTarget().getInstrInfo()),
47    curli_(0) {}
48
49void SplitAnalysis::clear() {
50  usingInstrs_.clear();
51  usingBlocks_.clear();
52  usingLoops_.clear();
53  curli_ = 0;
54}
55
56bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) {
57  MachineBasicBlock *T, *F;
58  SmallVector<MachineOperand, 4> Cond;
59  return !tii_.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond);
60}
61
62/// analyzeUses - Count instructions, basic blocks, and loops using curli.
63void SplitAnalysis::analyzeUses() {
64  const MachineRegisterInfo &MRI = mf_.getRegInfo();
65  for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(curli_->reg);
66       MachineInstr *MI = I.skipInstruction();) {
67    if (MI->isDebugValue() || !usingInstrs_.insert(MI))
68      continue;
69    MachineBasicBlock *MBB = MI->getParent();
70    if (usingBlocks_[MBB]++)
71      continue;
72    if (MachineLoop *Loop = loops_.getLoopFor(MBB))
73      usingLoops_[Loop]++;
74  }
75  DEBUG(dbgs() << "  counted "
76               << usingInstrs_.size() << " instrs, "
77               << usingBlocks_.size() << " blocks, "
78               << usingLoops_.size()  << " loops.\n");
79}
80
81/// removeUse - Update statistics by noting that MI no longer uses curli.
82void SplitAnalysis::removeUse(const MachineInstr *MI) {
83  if (!usingInstrs_.erase(MI))
84    return;
85
86  // Decrement MBB count.
87  const MachineBasicBlock *MBB = MI->getParent();
88  BlockCountMap::iterator bi = usingBlocks_.find(MBB);
89  assert(bi != usingBlocks_.end() && "MBB missing");
90  assert(bi->second && "0 count in map");
91  if (--bi->second)
92    return;
93  // No more uses in MBB.
94  usingBlocks_.erase(bi);
95
96  // Decrement loop count.
97  MachineLoop *Loop = loops_.getLoopFor(MBB);
98  if (!Loop)
99    return;
100  LoopCountMap::iterator li = usingLoops_.find(Loop);
101  assert(li != usingLoops_.end() && "Loop missing");
102  assert(li->second && "0 count in map");
103  if (--li->second)
104    return;
105  // No more blocks in Loop.
106  usingLoops_.erase(li);
107}
108
109// Get three sets of basic blocks surrounding a loop: Blocks inside the loop,
110// predecessor blocks, and exit blocks.
111void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) {
112  Blocks.clear();
113
114  // Blocks in the loop.
115  Blocks.Loop.insert(Loop->block_begin(), Loop->block_end());
116
117  // Predecessor blocks.
118  const MachineBasicBlock *Header = Loop->getHeader();
119  for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(),
120       E = Header->pred_end(); I != E; ++I)
121    if (!Blocks.Loop.count(*I))
122      Blocks.Preds.insert(*I);
123
124  // Exit blocks.
125  for (MachineLoop::block_iterator I = Loop->block_begin(),
126       E = Loop->block_end(); I != E; ++I) {
127    const MachineBasicBlock *MBB = *I;
128    for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
129       SE = MBB->succ_end(); SI != SE; ++SI)
130      if (!Blocks.Loop.count(*SI))
131        Blocks.Exits.insert(*SI);
132  }
133}
134
135/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
136/// and around the Loop.
137SplitAnalysis::LoopPeripheralUse SplitAnalysis::
138analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) {
139  LoopPeripheralUse use = ContainedInLoop;
140  for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
141       I != E; ++I) {
142    const MachineBasicBlock *MBB = I->first;
143    // Is this a peripheral block?
144    if (use < MultiPeripheral &&
145        (Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) {
146      if (I->second > 1) use = MultiPeripheral;
147      else               use = SinglePeripheral;
148      continue;
149    }
150    // Is it a loop block?
151    if (Blocks.Loop.count(MBB))
152      continue;
153    // It must be an unrelated block.
154    return OutsideLoop;
155  }
156  return use;
157}
158
159/// getCriticalExits - It may be necessary to partially break critical edges
160/// leaving the loop if an exit block has phi uses of curli. Collect the exit
161/// blocks that need special treatment into CriticalExits.
162void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
163                                     BlockPtrSet &CriticalExits) {
164  CriticalExits.clear();
165
166  // A critical exit block contains a phi def of curli, and has a predecessor
167  // that is not in the loop nor a loop predecessor.
168  // For such an exit block, the edges carrying the new variable must be moved
169  // to a new pre-exit block.
170  for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end();
171       I != E; ++I) {
172    const MachineBasicBlock *Succ = *I;
173    SlotIndex SuccIdx = lis_.getMBBStartIdx(Succ);
174    VNInfo *SuccVNI = curli_->getVNInfoAt(SuccIdx);
175    // This exit may not have curli live in at all. No need to split.
176    if (!SuccVNI)
177      continue;
178    // If this is not a PHI def, it is either using a value from before the
179    // loop, or a value defined inside the loop. Both are safe.
180    if (!SuccVNI->isPHIDef() || SuccVNI->def.getBaseIndex() != SuccIdx)
181      continue;
182    // This exit block does have a PHI. Does it also have a predecessor that is
183    // not a loop block or loop predecessor?
184    for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
185         PE = Succ->pred_end(); PI != PE; ++PI) {
186      const MachineBasicBlock *Pred = *PI;
187      if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred))
188        continue;
189      // This is a critical exit block, and we need to split the exit edge.
190      CriticalExits.insert(Succ);
191      break;
192    }
193  }
194}
195
196/// canSplitCriticalExits - Return true if it is possible to insert new exit
197/// blocks before the blocks in CriticalExits.
198bool
199SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
200                                     BlockPtrSet &CriticalExits) {
201  // If we don't allow critical edge splitting, require no critical exits.
202  if (!AllowSplit)
203    return CriticalExits.empty();
204
205  for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end();
206       I != E; ++I) {
207    const MachineBasicBlock *Succ = *I;
208    // We want to insert a new pre-exit MBB before Succ, and change all the
209    // in-loop blocks to branch to the pre-exit instead of Succ.
210    // Check that all the in-loop predecessors can be changed.
211    for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
212         PE = Succ->pred_end(); PI != PE; ++PI) {
213      const MachineBasicBlock *Pred = *PI;
214      // The external predecessors won't be altered.
215      if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred))
216        continue;
217      if (!canAnalyzeBranch(Pred))
218        return false;
219    }
220
221    // If Succ's layout predecessor falls through, that too must be analyzable.
222    // We need to insert the pre-exit block in the gap.
223    MachineFunction::const_iterator MFI = Succ;
224    if (MFI == mf_.begin())
225      continue;
226    if (!canAnalyzeBranch(--MFI))
227      return false;
228  }
229  // No problems found.
230  return true;
231}
232
233void SplitAnalysis::analyze(const LiveInterval *li) {
234  clear();
235  curli_ = li;
236  analyzeUses();
237}
238
239const MachineLoop *SplitAnalysis::getBestSplitLoop() {
240  assert(curli_ && "Call analyze() before getBestSplitLoop");
241  if (usingLoops_.empty())
242    return 0;
243
244  LoopPtrSet Loops, SecondLoops;
245  LoopBlocks Blocks;
246  BlockPtrSet CriticalExits;
247
248  // Find first-class and second class candidate loops.
249  // We prefer to split around loops where curli is used outside the periphery.
250  for (LoopCountMap::const_iterator I = usingLoops_.begin(),
251       E = usingLoops_.end(); I != E; ++I) {
252    const MachineLoop *Loop = I->first;
253    getLoopBlocks(Loop, Blocks);
254
255    // FIXME: We need an SSA updater to properly handle multiple exit blocks.
256    if (Blocks.Exits.size() > 1) {
257      DEBUG(dbgs() << "  multiple exits from " << *Loop);
258      continue;
259    }
260
261    LoopPtrSet *LPS = 0;
262    switch(analyzeLoopPeripheralUse(Blocks)) {
263    case OutsideLoop:
264      LPS = &Loops;
265      break;
266    case MultiPeripheral:
267      LPS = &SecondLoops;
268      break;
269    case ContainedInLoop:
270      DEBUG(dbgs() << "  contained in " << *Loop);
271      continue;
272    case SinglePeripheral:
273      DEBUG(dbgs() << "  single peripheral use in " << *Loop);
274      continue;
275    }
276    // Will it be possible to split around this loop?
277    getCriticalExits(Blocks, CriticalExits);
278    DEBUG(dbgs() << "  " << CriticalExits.size() << " critical exits from "
279                 << *Loop);
280    if (!canSplitCriticalExits(Blocks, CriticalExits))
281      continue;
282    // This is a possible split.
283    assert(LPS);
284    LPS->insert(Loop);
285  }
286
287  DEBUG(dbgs() << "  getBestSplitLoop found " << Loops.size() << " + "
288               << SecondLoops.size() << " candidate loops.\n");
289
290  // If there are no first class loops available, look at second class loops.
291  if (Loops.empty())
292    Loops = SecondLoops;
293
294  if (Loops.empty())
295    return 0;
296
297  // Pick the earliest loop.
298  // FIXME: Are there other heuristics to consider?
299  const MachineLoop *Best = 0;
300  SlotIndex BestIdx;
301  for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E;
302       ++I) {
303    SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader());
304    if (!Best || Idx < BestIdx)
305      Best = *I, BestIdx = Idx;
306  }
307  DEBUG(dbgs() << "  getBestSplitLoop found " << *Best);
308  return Best;
309}
310
311/// getMultiUseBlocks - if curli has more than one use in a basic block, it
312/// may be an advantage to split curli for the duration of the block.
313bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) {
314  // If curli is local to one block, there is no point to splitting it.
315  if (usingBlocks_.size() <= 1)
316    return false;
317  // Add blocks with multiple uses.
318  for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
319       I != E; ++I)
320    switch (I->second) {
321    case 0:
322    case 1:
323      continue;
324    case 2: {
325      // It doesn't pay to split a 2-instr block if it redefines curli.
326      VNInfo *VN1 = curli_->getVNInfoAt(lis_.getMBBStartIdx(I->first));
327      VNInfo *VN2 =
328        curli_->getVNInfoAt(lis_.getMBBEndIdx(I->first).getPrevIndex());
329      // live-in and live-out with a different value.
330      if (VN1 && VN2 && VN1 != VN2)
331        continue;
332    } // Fall through.
333    default:
334      Blocks.insert(I->first);
335    }
336  return !Blocks.empty();
337}
338
339//===----------------------------------------------------------------------===//
340//                               Split Editor
341//===----------------------------------------------------------------------===//
342
343/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
344SplitEditor::SplitEditor(SplitAnalysis &sa, LiveIntervals &lis, VirtRegMap &vrm,
345                         std::vector<LiveInterval*> &intervals)
346  : sa_(sa), lis_(lis), vrm_(vrm),
347    mri_(vrm.getMachineFunction().getRegInfo()),
348    tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()),
349    curli_(sa_.getCurLI()),
350    dupli_(0), openli_(0),
351    intervals_(intervals),
352    firstInterval(intervals_.size())
353{
354  assert(curli_ && "SplitEditor created from empty SplitAnalysis");
355
356  // Make sure curli_ is assigned a stack slot, so all our intervals get the
357  // same slot as curli_.
358  if (vrm_.getStackSlot(curli_->reg) == VirtRegMap::NO_STACK_SLOT)
359    vrm_.assignVirt2StackSlot(curli_->reg);
360
361}
362
363LiveInterval *SplitEditor::createInterval() {
364  unsigned curli = sa_.getCurLI()->reg;
365  unsigned Reg = mri_.createVirtualRegister(mri_.getRegClass(curli));
366  LiveInterval &Intv = lis_.getOrCreateInterval(Reg);
367  vrm_.grow();
368  vrm_.assignVirt2StackSlot(Reg, vrm_.getStackSlot(curli));
369  return &Intv;
370}
371
372LiveInterval *SplitEditor::getDupLI() {
373  if (!dupli_) {
374    // Create an interval for dupli that is a copy of curli.
375    dupli_ = createInterval();
376    dupli_->Copy(*curli_, &mri_, lis_.getVNInfoAllocator());
377  }
378  return dupli_;
379}
380
381VNInfo *SplitEditor::mapValue(const VNInfo *curliVNI) {
382  VNInfo *&VNI = valueMap_[curliVNI];
383  if (!VNI)
384    VNI = openli_->createValueCopy(curliVNI, lis_.getVNInfoAllocator());
385  return VNI;
386}
387
388/// Insert a COPY instruction curli -> li. Allocate a new value from li
389/// defined by the COPY. Note that rewrite() will deal with the curli
390/// register, so this function can be used to copy from any interval - openli,
391/// curli, or dupli.
392VNInfo *SplitEditor::insertCopy(LiveInterval &LI,
393                                MachineBasicBlock &MBB,
394                                MachineBasicBlock::iterator I) {
395  MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY),
396                             LI.reg).addReg(curli_->reg);
397  SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
398  return LI.getNextValue(DefIdx, MI, true, lis_.getVNInfoAllocator());
399}
400
401/// Create a new virtual register and live interval.
402void SplitEditor::openIntv() {
403  assert(!openli_ && "Previous LI not closed before openIntv");
404  openli_ = createInterval();
405  intervals_.push_back(openli_);
406  liveThrough_ = false;
407}
408
409/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
410/// not live before Idx, a COPY is not inserted.
411void SplitEditor::enterIntvBefore(SlotIndex Idx) {
412  assert(openli_ && "openIntv not called before enterIntvBefore");
413
414  // Copy from curli_ if it is live.
415  if (VNInfo *CurVNI = curli_->getVNInfoAt(Idx.getUseIndex())) {
416    MachineInstr *MI = lis_.getInstructionFromIndex(Idx);
417    assert(MI && "enterIntvBefore called with invalid index");
418    VNInfo *VNI = insertCopy(*openli_, *MI->getParent(), MI);
419    openli_->addRange(LiveRange(VNI->def, Idx.getDefIndex(), VNI));
420
421    // Make sure CurVNI is properly mapped.
422    VNInfo *&mapVNI = valueMap_[CurVNI];
423    // We dont have SSA update yet, so only one entry per value is allowed.
424    assert(!mapVNI && "enterIntvBefore called more than once for the same value");
425    mapVNI = VNI;
426  }
427  DEBUG(dbgs() << "    enterIntvBefore " << Idx << ": " << *openli_ << '\n');
428}
429
430/// enterIntvAtEnd - Enter openli at the end of MBB.
431/// PhiMBB is a successor inside openli where a PHI value is created.
432/// Currently, all entries must share the same PhiMBB.
433void SplitEditor::enterIntvAtEnd(MachineBasicBlock &A, MachineBasicBlock &B) {
434  assert(openli_ && "openIntv not called before enterIntvAtEnd");
435
436  SlotIndex EndA = lis_.getMBBEndIdx(&A);
437  VNInfo *CurVNIA = curli_->getVNInfoAt(EndA.getPrevIndex());
438  if (!CurVNIA) {
439    DEBUG(dbgs() << "    enterIntvAtEnd, curli not live out of BB#"
440                 << A.getNumber() << ".\n");
441    return;
442  }
443
444  // Add a phi kill value and live range out of A.
445  VNInfo *VNIA = insertCopy(*openli_, A, A.getFirstTerminator());
446  openli_->addRange(LiveRange(VNIA->def, EndA, VNIA));
447
448  // FIXME: If this is the only entry edge, we don't need the extra PHI value.
449  // FIXME: If there are multiple entry blocks (so not a loop), we need proper
450  // SSA update.
451
452  // Now look at the start of B.
453  SlotIndex StartB = lis_.getMBBStartIdx(&B);
454  SlotIndex EndB = lis_.getMBBEndIdx(&B);
455  const LiveRange *CurB = curli_->getLiveRangeContaining(StartB);
456  if (!CurB) {
457    DEBUG(dbgs() << "    enterIntvAtEnd: curli not live in to BB#"
458                 << B.getNumber() << ".\n");
459    return;
460  }
461
462  VNInfo *VNIB = openli_->getVNInfoAt(StartB);
463  if (!VNIB) {
464    // Create a phi value.
465    VNIB = openli_->getNextValue(SlotIndex(StartB, true), 0, false,
466                                 lis_.getVNInfoAllocator());
467    VNIB->setIsPHIDef(true);
468    VNInfo *&mapVNI = valueMap_[CurB->valno];
469    if (mapVNI) {
470      // Multiple copies - must create PHI value.
471      abort();
472    } else {
473      // This is the first copy of dupLR. Mark the mapping.
474      mapVNI = VNIB;
475    }
476
477  }
478
479  DEBUG(dbgs() << "    enterIntvAtEnd: " << *openli_ << '\n');
480}
481
482/// useIntv - indicate that all instructions in MBB should use openli.
483void SplitEditor::useIntv(const MachineBasicBlock &MBB) {
484  useIntv(lis_.getMBBStartIdx(&MBB), lis_.getMBBEndIdx(&MBB));
485}
486
487void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) {
488  assert(openli_ && "openIntv not called before useIntv");
489
490  // Map the curli values from the interval into openli_
491  LiveInterval::const_iterator B = curli_->begin(), E = curli_->end();
492  LiveInterval::const_iterator I = std::lower_bound(B, E, Start);
493
494  if (I != B) {
495    --I;
496    // I begins before Start, but overlaps.
497    if (I->end > Start)
498      openli_->addRange(LiveRange(Start, std::min(End, I->end),
499                        mapValue(I->valno)));
500    ++I;
501  }
502
503  // The remaining ranges begin after Start.
504  for (;I != E && I->start < End; ++I)
505    openli_->addRange(LiveRange(I->start, std::min(End, I->end),
506                                mapValue(I->valno)));
507  DEBUG(dbgs() << "    use [" << Start << ';' << End << "): " << *openli_
508               << '\n');
509}
510
511/// leaveIntvAfter - Leave openli after the instruction at Idx.
512void SplitEditor::leaveIntvAfter(SlotIndex Idx) {
513  assert(openli_ && "openIntv not called before leaveIntvAfter");
514
515  const LiveRange *CurLR = curli_->getLiveRangeContaining(Idx.getDefIndex());
516  if (!CurLR || CurLR->end <= Idx.getBoundaryIndex()) {
517    DEBUG(dbgs() << "    leaveIntvAfter " << Idx << ": not live\n");
518    return;
519  }
520
521  // Was this value of curli live through openli?
522  if (!openli_->liveAt(CurLR->valno->def)) {
523    DEBUG(dbgs() << "    leaveIntvAfter " << Idx << ": using external value\n");
524    liveThrough_ = true;
525    return;
526  }
527
528  // We are going to insert a back copy, so we must have a dupli_.
529  LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Idx.getDefIndex());
530  assert(DupLR && "dupli not live into black, but curli is?");
531
532  // Insert the COPY instruction.
533  MachineBasicBlock::iterator I = lis_.getInstructionFromIndex(Idx);
534  MachineInstr *MI = BuildMI(*I->getParent(), llvm::next(I), I->getDebugLoc(),
535                             tii_.get(TargetOpcode::COPY), dupli_->reg)
536                       .addReg(openli_->reg);
537  SlotIndex CopyIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
538  openli_->addRange(LiveRange(Idx.getDefIndex(), CopyIdx,
539                    mapValue(CurLR->valno)));
540  DupLR->valno->def = CopyIdx;
541  DEBUG(dbgs() << "    leaveIntvAfter " << Idx << ": " << *openli_ << '\n');
542}
543
544/// leaveIntvAtTop - Leave the interval at the top of MBB.
545/// Currently, only one value can leave the interval.
546void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
547  assert(openli_ && "openIntv not called before leaveIntvAtTop");
548
549  SlotIndex Start = lis_.getMBBStartIdx(&MBB);
550  const LiveRange *CurLR = curli_->getLiveRangeContaining(Start);
551
552  // Is curli even live-in to MBB?
553  if (!CurLR) {
554    DEBUG(dbgs() << "    leaveIntvAtTop at " << Start << ": not live\n");
555    return;
556  }
557
558  // Is curli defined by PHI at the beginning of MBB?
559  bool isPHIDef = CurLR->valno->isPHIDef() &&
560                  CurLR->valno->def.getBaseIndex() == Start;
561
562  // If MBB is using a value of curli that was defined outside the openli range,
563  // we don't want to copy it back here.
564  if (!isPHIDef && !openli_->liveAt(CurLR->valno->def)) {
565    DEBUG(dbgs() << "    leaveIntvAtTop at " << Start
566                 << ": using external value\n");
567    liveThrough_ = true;
568    return;
569  }
570
571  // We are going to insert a back copy, so we must have a dupli_.
572  LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Start);
573  assert(DupLR && "dupli not live into black, but curli is?");
574
575  // Insert the COPY instruction.
576  MachineInstr *MI = BuildMI(MBB, MBB.begin(), DebugLoc(),
577                             tii_.get(TargetOpcode::COPY), dupli_->reg)
578                       .addReg(openli_->reg);
579  SlotIndex Idx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
580
581  // Adjust dupli and openli values.
582  if (isPHIDef) {
583    // dupli was already a PHI on entry to MBB. Simply insert an openli PHI,
584    // and shift the dupli def down to the COPY.
585    VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
586                                        lis_.getVNInfoAllocator());
587    VNI->setIsPHIDef(true);
588    openli_->addRange(LiveRange(VNI->def, Idx, VNI));
589
590    dupli_->removeRange(Start, Idx);
591    DupLR->valno->def = Idx;
592    DupLR->valno->setIsPHIDef(false);
593  } else {
594    // The dupli value was defined somewhere inside the openli range.
595    DEBUG(dbgs() << "    leaveIntvAtTop source value defined at "
596                 << DupLR->valno->def << "\n");
597    // FIXME: We may not need a PHI here if all predecessors have the same
598    // value.
599    VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
600                                        lis_.getVNInfoAllocator());
601    VNI->setIsPHIDef(true);
602    openli_->addRange(LiveRange(VNI->def, Idx, VNI));
603
604    // FIXME: What if DupLR->valno is used by multiple exits? SSA Update.
605
606    // closeIntv is going to remove the superfluous live ranges.
607    DupLR->valno->def = Idx;
608    DupLR->valno->setIsPHIDef(false);
609  }
610
611  DEBUG(dbgs() << "    leaveIntvAtTop at " << Idx << ": " << *openli_ << '\n');
612}
613
614/// closeIntv - Indicate that we are done editing the currently open
615/// LiveInterval, and ranges can be trimmed.
616void SplitEditor::closeIntv() {
617  assert(openli_ && "openIntv not called before closeIntv");
618
619  DEBUG(dbgs() << "    closeIntv cleaning up\n");
620  DEBUG(dbgs() << "    open " << *openli_ << '\n');
621
622  if (liveThrough_) {
623    DEBUG(dbgs() << "    value live through region, leaving dupli as is.\n");
624  } else {
625    // live out with copies inserted, or killed by region. Either way we need to
626    // remove the overlapping region from dupli.
627    getDupLI();
628    for (LiveInterval::iterator I = openli_->begin(), E = openli_->end();
629         I != E; ++I) {
630      dupli_->removeRange(I->start, I->end);
631    }
632    // FIXME: A block branching to the entry block may also branch elsewhere
633    // curli is live. We need both openli and curli to be live in that case.
634    DEBUG(dbgs() << "    dup2 " << *dupli_ << '\n');
635  }
636  openli_ = 0;
637  valueMap_.clear();
638}
639
640/// rewrite - after all the new live ranges have been created, rewrite
641/// instructions using curli to use the new intervals.
642void SplitEditor::rewrite() {
643  assert(!openli_ && "Previous LI not closed before rewrite");
644  const LiveInterval *curli = sa_.getCurLI();
645  for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(curli->reg),
646       RE = mri_.reg_end(); RI != RE;) {
647    MachineOperand &MO = RI.getOperand();
648    MachineInstr *MI = MO.getParent();
649    ++RI;
650    if (MI->isDebugValue()) {
651      DEBUG(dbgs() << "Zapping " << *MI);
652      // FIXME: We can do much better with debug values.
653      MO.setReg(0);
654      continue;
655    }
656    SlotIndex Idx = lis_.getInstructionIndex(MI);
657    Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex();
658    LiveInterval *LI = dupli_;
659    for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
660      LiveInterval *testli = intervals_[i];
661      if (testli->liveAt(Idx)) {
662        LI = testli;
663        break;
664      }
665    }
666    if (LI) {
667      MO.setReg(LI->reg);
668      sa_.removeUse(MI);
669      DEBUG(dbgs() << "  rewrite " << Idx << '\t' << *MI);
670    }
671  }
672
673  // dupli_ goes in last, after rewriting.
674  if (dupli_) {
675    if (dupli_->empty()) {
676      DEBUG(dbgs() << "  dupli became empty?\n");
677      lis_.removeInterval(dupli_->reg);
678      dupli_ = 0;
679    } else {
680      dupli_->RenumberValues(lis_);
681      intervals_.push_back(dupli_);
682    }
683  }
684
685  // Calculate spill weight and allocation hints for new intervals.
686  VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_);
687  for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
688    LiveInterval &li = *intervals_[i];
689    vrai.CalculateRegClass(li.reg);
690    vrai.CalculateWeightAndHint(li);
691    DEBUG(dbgs() << "  new interval " << mri_.getRegClass(li.reg)->getName()
692                 << ":" << li << '\n');
693  }
694}
695
696
697//===----------------------------------------------------------------------===//
698//                               Loop Splitting
699//===----------------------------------------------------------------------===//
700
701bool SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
702  SplitAnalysis::LoopBlocks Blocks;
703  sa_.getLoopBlocks(Loop, Blocks);
704
705  // Break critical edges as needed.
706  SplitAnalysis::BlockPtrSet CriticalExits;
707  sa_.getCriticalExits(Blocks, CriticalExits);
708  assert(CriticalExits.empty() && "Cannot break critical exits yet");
709
710  // Create new live interval for the loop.
711  openIntv();
712
713  // Insert copies in the predecessors.
714  for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(),
715       E = Blocks.Preds.end(); I != E; ++I) {
716    MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
717    enterIntvAtEnd(MBB, *Loop->getHeader());
718  }
719
720  // Switch all loop blocks.
721  for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(),
722       E = Blocks.Loop.end(); I != E; ++I)
723     useIntv(**I);
724
725  // Insert back copies in the exit blocks.
726  for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(),
727       E = Blocks.Exits.end(); I != E; ++I) {
728    MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
729    leaveIntvAtTop(MBB);
730  }
731
732  // Done.
733  closeIntv();
734  rewrite();
735  return dupli_;
736}
737
738
739//===----------------------------------------------------------------------===//
740//                            Single Block Splitting
741//===----------------------------------------------------------------------===//
742
743/// splitSingleBlocks - Split curli into a separate live interval inside each
744/// basic block in Blocks. Return true if curli has been completely replaced,
745/// false if curli is still intact, and needs to be spilled or split further.
746bool SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) {
747  DEBUG(dbgs() << "  splitSingleBlocks for " << Blocks.size() << " blocks.\n");
748  // Determine the first and last instruction using curli in each block.
749  typedef std::pair<SlotIndex,SlotIndex> IndexPair;
750  typedef DenseMap<const MachineBasicBlock*,IndexPair> IndexPairMap;
751  IndexPairMap MBBRange;
752  for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(),
753       E = sa_.usingInstrs_.end(); I != E; ++I) {
754    const MachineBasicBlock *MBB = (*I)->getParent();
755    if (!Blocks.count(MBB))
756      continue;
757    SlotIndex Idx = lis_.getInstructionIndex(*I);
758    DEBUG(dbgs() << "  BB#" << MBB->getNumber() << '\t' << Idx << '\t' << **I);
759    IndexPair &IP = MBBRange[MBB];
760    if (!IP.first.isValid() || Idx < IP.first)
761      IP.first = Idx;
762    if (!IP.second.isValid() || Idx > IP.second)
763      IP.second = Idx;
764  }
765
766  // Create a new interval for each block.
767  for (SplitAnalysis::BlockPtrSet::const_iterator I = Blocks.begin(),
768       E = Blocks.end(); I != E; ++I) {
769    IndexPair &IP = MBBRange[*I];
770    DEBUG(dbgs() << "  splitting for BB#" << (*I)->getNumber() << ": ["
771                 << IP.first << ';' << IP.second << ")\n");
772    assert(IP.first.isValid() && IP.second.isValid());
773
774    openIntv();
775    enterIntvBefore(IP.first);
776    useIntv(IP.first.getBaseIndex(), IP.second.getBoundaryIndex());
777    leaveIntvAfter(IP.second);
778    closeIntv();
779  }
780  rewrite();
781  return dupli_;
782}
783
784