SplitKit.cpp revision b38f02435b58eaba878d7a1894b610c4679fbd41 
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_.insert(Loop);
74  }
75  DEBUG(dbgs() << "Counted "
76               << usingInstrs_.size() << " instrs, "
77               << usingBlocks_.size() << " blocks, "
78               << usingLoops_.size()  << " loops in "
79               << *curli_ << "\n");
80}
81
82// Get three sets of basic blocks surrounding a loop: Blocks inside the loop,
83// predecessor blocks, and exit blocks.
84void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) {
85  Blocks.clear();
86
87  // Blocks in the loop.
88  Blocks.Loop.insert(Loop->block_begin(), Loop->block_end());
89
90  // Predecessor blocks.
91  const MachineBasicBlock *Header = Loop->getHeader();
92  for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(),
93       E = Header->pred_end(); I != E; ++I)
94    if (!Blocks.Loop.count(*I))
95      Blocks.Preds.insert(*I);
96
97  // Exit blocks.
98  for (MachineLoop::block_iterator I = Loop->block_begin(),
99       E = Loop->block_end(); I != E; ++I) {
100    const MachineBasicBlock *MBB = *I;
101    for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
102       SE = MBB->succ_end(); SI != SE; ++SI)
103      if (!Blocks.Loop.count(*SI))
104        Blocks.Exits.insert(*SI);
105  }
106}
107
108/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
109/// and around the Loop.
110SplitAnalysis::LoopPeripheralUse SplitAnalysis::
111analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) {
112  LoopPeripheralUse use = ContainedInLoop;
113  for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
114       I != E; ++I) {
115    const MachineBasicBlock *MBB = I->first;
116    // Is this a peripheral block?
117    if (use < MultiPeripheral &&
118        (Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) {
119      if (I->second > 1) use = MultiPeripheral;
120      else               use = SinglePeripheral;
121      continue;
122    }
123    // Is it a loop block?
124    if (Blocks.Loop.count(MBB))
125      continue;
126    // It must be an unrelated block.
127    return OutsideLoop;
128  }
129  return use;
130}
131
132/// getCriticalExits - It may be necessary to partially break critical edges
133/// leaving the loop if an exit block has phi uses of curli. Collect the exit
134/// blocks that need special treatment into CriticalExits.
135void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
136                                     BlockPtrSet &CriticalExits) {
137  CriticalExits.clear();
138
139  // A critical exit block contains a phi def of curli, and has a predecessor
140  // that is not in the loop nor a loop predecessor.
141  // For such an exit block, the edges carrying the new variable must be moved
142  // to a new pre-exit block.
143  for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end();
144       I != E; ++I) {
145    const MachineBasicBlock *Succ = *I;
146    SlotIndex SuccIdx = lis_.getMBBStartIdx(Succ);
147    VNInfo *SuccVNI = curli_->getVNInfoAt(SuccIdx);
148    // This exit may not have curli live in at all. No need to split.
149    if (!SuccVNI)
150      continue;
151    // If this is not a PHI def, it is either using a value from before the
152    // loop, or a value defined inside the loop. Both are safe.
153    if (!SuccVNI->isPHIDef() || SuccVNI->def.getBaseIndex() != SuccIdx)
154      continue;
155    // This exit block does have a PHI. Does it also have a predecessor that is
156    // not a loop block or loop predecessor?
157    for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
158         PE = Succ->pred_end(); PI != PE; ++PI) {
159      const MachineBasicBlock *Pred = *PI;
160      if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred))
161        continue;
162      // This is a critical exit block, and we need to split the exit edge.
163      CriticalExits.insert(Succ);
164      break;
165    }
166  }
167}
168
169/// canSplitCriticalExits - Return true if it is possible to insert new exit
170/// blocks before the blocks in CriticalExits.
171bool
172SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
173                                     BlockPtrSet &CriticalExits) {
174  // If we don't allow critical edge splitting, require no critical exits.
175  if (!AllowSplit)
176    return CriticalExits.empty();
177
178  for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end();
179       I != E; ++I) {
180    const MachineBasicBlock *Succ = *I;
181    // We want to insert a new pre-exit MBB before Succ, and change all the
182    // in-loop blocks to branch to the pre-exit instead of Succ.
183    // Check that all the in-loop predecessors can be changed.
184    for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
185         PE = Succ->pred_end(); PI != PE; ++PI) {
186      const MachineBasicBlock *Pred = *PI;
187      // The external predecessors won't be altered.
188      if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred))
189        continue;
190      if (!canAnalyzeBranch(Pred))
191        return false;
192    }
193
194    // If Succ's layout predecessor falls through, that too must be analyzable.
195    // We need to insert the pre-exit block in the gap.
196    MachineFunction::const_iterator MFI = Succ;
197    if (MFI == mf_.begin())
198      continue;
199    if (!canAnalyzeBranch(--MFI))
200      return false;
201  }
202  // No problems found.
203  return true;
204}
205
206void SplitAnalysis::analyze(const LiveInterval *li) {
207  clear();
208  curli_ = li;
209  analyzeUses();
210}
211
212const MachineLoop *SplitAnalysis::getBestSplitLoop() {
213  assert(curli_ && "Call analyze() before getBestSplitLoop");
214  if (usingLoops_.empty())
215    return 0;
216
217  LoopPtrSet Loops, SecondLoops;
218  LoopBlocks Blocks;
219  BlockPtrSet CriticalExits;
220
221  // Find first-class and second class candidate loops.
222  // We prefer to split around loops where curli is used outside the periphery.
223  for (LoopPtrSet::const_iterator I = usingLoops_.begin(),
224       E = usingLoops_.end(); I != E; ++I) {
225    getLoopBlocks(*I, Blocks);
226
227    // FIXME: We need an SSA updater to properly handle multiple exit blocks.
228    if (Blocks.Exits.size() > 1) {
229      DEBUG(dbgs() << "MultipleExits: " << **I);
230      continue;
231    }
232
233    LoopPtrSet *LPS = 0;
234    switch(analyzeLoopPeripheralUse(Blocks)) {
235    case OutsideLoop:
236      LPS = &Loops;
237      break;
238    case MultiPeripheral:
239      LPS = &SecondLoops;
240      break;
241    case ContainedInLoop:
242      DEBUG(dbgs() << "ContainedInLoop: " << **I);
243      continue;
244    case SinglePeripheral:
245      DEBUG(dbgs() << "SinglePeripheral: " << **I);
246      continue;
247    }
248    // Will it be possible to split around this loop?
249    getCriticalExits(Blocks, CriticalExits);
250    DEBUG(dbgs() << CriticalExits.size() << " critical exits: " << **I);
251    if (!canSplitCriticalExits(Blocks, CriticalExits))
252      continue;
253    // This is a possible split.
254    assert(LPS);
255    LPS->insert(*I);
256  }
257
258  DEBUG(dbgs() << "Got " << Loops.size() << " + " << SecondLoops.size()
259               << " candidate loops\n");
260
261  // If there are no first class loops available, look at second class loops.
262  if (Loops.empty())
263    Loops = SecondLoops;
264
265  if (Loops.empty())
266    return 0;
267
268  // Pick the earliest loop.
269  // FIXME: Are there other heuristics to consider?
270  const MachineLoop *Best = 0;
271  SlotIndex BestIdx;
272  for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E;
273       ++I) {
274    SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader());
275    if (!Best || Idx < BestIdx)
276      Best = *I, BestIdx = Idx;
277  }
278  DEBUG(dbgs() << "Best: " << *Best);
279  return Best;
280}
281
282
283//===----------------------------------------------------------------------===//
284//                               Split Editor
285//===----------------------------------------------------------------------===//
286
287/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
288SplitEditor::SplitEditor(SplitAnalysis &sa, LiveIntervals &lis, VirtRegMap &vrm,
289                         std::vector<LiveInterval*> &intervals)
290  : sa_(sa), lis_(lis), vrm_(vrm),
291    mri_(vrm.getMachineFunction().getRegInfo()),
292    tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()),
293    curli_(sa_.getCurLI()),
294    dupli_(0), openli_(0),
295    intervals_(intervals),
296    firstInterval(intervals_.size())
297{
298  assert(curli_ && "SplitEditor created from empty SplitAnalysis");
299
300  // Make sure curli_ is assigned a stack slot, so all our intervals get the
301  // same slot as curli_.
302  if (vrm_.getStackSlot(curli_->reg) == VirtRegMap::NO_STACK_SLOT)
303    vrm_.assignVirt2StackSlot(curli_->reg);
304
305}
306
307LiveInterval *SplitEditor::createInterval() {
308  unsigned curli = sa_.getCurLI()->reg;
309  unsigned Reg = mri_.createVirtualRegister(mri_.getRegClass(curli));
310  LiveInterval &Intv = lis_.getOrCreateInterval(Reg);
311  vrm_.grow();
312  vrm_.assignVirt2StackSlot(Reg, vrm_.getStackSlot(curli));
313  return &Intv;
314}
315
316LiveInterval *SplitEditor::getDupLI() {
317  if (!dupli_) {
318    // Create an interval for dupli that is a copy of curli.
319    dupli_ = createInterval();
320    dupli_->Copy(*curli_, &mri_, lis_.getVNInfoAllocator());
321    DEBUG(dbgs() << "SplitEditor DupLI: " << *dupli_ << '\n');
322  }
323  return dupli_;
324}
325
326VNInfo *SplitEditor::mapValue(const VNInfo *curliVNI) {
327  VNInfo *&VNI = valueMap_[curliVNI];
328  if (!VNI)
329    VNI = openli_->createValueCopy(curliVNI, lis_.getVNInfoAllocator());
330  return VNI;
331}
332
333/// Insert a COPY instruction curli -> li. Allocate a new value from li
334/// defined by the COPY. Note that rewrite() will deal with the curli
335/// register, so this function can be used to copy from any interval - openli,
336/// curli, or dupli.
337VNInfo *SplitEditor::insertCopy(LiveInterval &LI,
338                                MachineBasicBlock &MBB,
339                                MachineBasicBlock::iterator I) {
340  MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY),
341                             LI.reg).addReg(curli_->reg);
342  SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
343  return LI.getNextValue(DefIdx, MI, true, lis_.getVNInfoAllocator());
344}
345
346/// Create a new virtual register and live interval.
347void SplitEditor::openIntv() {
348  assert(!openli_ && "Previous LI not closed before openIntv");
349  openli_ = createInterval();
350  intervals_.push_back(openli_);
351  liveThrough_ = false;
352}
353
354/// enterIntvAtEnd - Enter openli at the end of MBB.
355/// PhiMBB is a successor inside openli where a PHI value is created.
356/// Currently, all entries must share the same PhiMBB.
357void SplitEditor::enterIntvAtEnd(MachineBasicBlock &A, MachineBasicBlock &B) {
358  assert(openli_ && "openIntv not called before enterIntvAtEnd");
359
360  SlotIndex EndA = lis_.getMBBEndIdx(&A);
361  VNInfo *CurVNIA = curli_->getVNInfoAt(EndA.getPrevIndex());
362  if (!CurVNIA) {
363    DEBUG(dbgs() << "  ignoring enterIntvAtEnd, curli not live out of BB#"
364                 << A.getNumber() << ".\n");
365    return;
366  }
367
368  // Add a phi kill value and live range out of A.
369  VNInfo *VNIA = insertCopy(*openli_, A, A.getFirstTerminator());
370  openli_->addRange(LiveRange(VNIA->def, EndA, VNIA));
371
372  // FIXME: If this is the only entry edge, we don't need the extra PHI value.
373  // FIXME: If there are multiple entry blocks (so not a loop), we need proper
374  // SSA update.
375
376  // Now look at the start of B.
377  SlotIndex StartB = lis_.getMBBStartIdx(&B);
378  SlotIndex EndB = lis_.getMBBEndIdx(&B);
379  const LiveRange *CurB = curli_->getLiveRangeContaining(StartB);
380  if (!CurB) {
381    DEBUG(dbgs() << "  enterIntvAtEnd: curli not live in to BB#"
382                 << B.getNumber() << ".\n");
383    return;
384  }
385
386  VNInfo *VNIB = openli_->getVNInfoAt(StartB);
387  if (!VNIB) {
388    // Create a phi value.
389    VNIB = openli_->getNextValue(SlotIndex(StartB, true), 0, false,
390                                 lis_.getVNInfoAllocator());
391    VNIB->setIsPHIDef(true);
392    // Add a minimal range for the new value.
393    openli_->addRange(LiveRange(VNIB->def, std::min(EndB, CurB->end), VNIB));
394
395    VNInfo *&mapVNI = valueMap_[CurB->valno];
396    if (mapVNI) {
397      // Multiple copies - must create PHI value.
398      abort();
399    } else {
400      // This is the first copy of dupLR. Mark the mapping.
401      mapVNI = VNIB;
402    }
403
404  }
405
406  DEBUG(dbgs() << "  enterIntvAtEnd: " << *openli_ << '\n');
407}
408
409/// useIntv - indicate that all instructions in MBB should use openli.
410void SplitEditor::useIntv(const MachineBasicBlock &MBB) {
411  useIntv(lis_.getMBBStartIdx(&MBB), lis_.getMBBEndIdx(&MBB));
412}
413
414void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) {
415  assert(openli_ && "openIntv not called before useIntv");
416
417  // Map the curli values from the interval into openli_
418  LiveInterval::const_iterator B = curli_->begin(), E = curli_->end();
419  LiveInterval::const_iterator I = std::lower_bound(B, E, Start);
420
421  if (I != B) {
422    --I;
423    // I begins before Start, but overlaps. openli may already have a value.
424    if (I->end > Start && !openli_->liveAt(Start))
425      openli_->addRange(LiveRange(Start, std::min(End, I->end),
426                        mapValue(I->valno)));
427    ++I;
428  }
429
430  // The remaining ranges begin after Start.
431  for (;I != E && I->start < End; ++I)
432    openli_->addRange(LiveRange(I->start, std::min(End, I->end),
433                                mapValue(I->valno)));
434  DEBUG(dbgs() << "  added range [" << Start << ';' << End << "): " << *openli_
435               << '\n');
436}
437
438/// leaveIntvAtTop - Leave the interval at the top of MBB.
439/// Currently, only one value can leave the interval.
440void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
441  assert(openli_ && "openIntv not called before leaveIntvAtTop");
442
443  SlotIndex Start = lis_.getMBBStartIdx(&MBB);
444  const LiveRange *CurLR = curli_->getLiveRangeContaining(Start);
445
446  // Is curli even live-in to MBB?
447  if (!CurLR) {
448    DEBUG(dbgs() << "  leaveIntvAtTop at " << Start << ": not live\n");
449    return;
450  }
451
452  // Is curli defined by PHI at the beginning of MBB?
453  bool isPHIDef = CurLR->valno->isPHIDef() &&
454                  CurLR->valno->def.getBaseIndex() == Start;
455
456  // If MBB is using a value of curli that was defined outside the openli range,
457  // we don't want to copy it back here.
458  if (!isPHIDef && !openli_->liveAt(CurLR->valno->def)) {
459    DEBUG(dbgs() << "  leaveIntvAtTop at " << Start
460                 << ": using external value\n");
461    liveThrough_ = true;
462    return;
463  }
464
465  // We are going to insert a back copy, so we must have a dupli_.
466  LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Start);
467  assert(DupLR && "dupli not live into black, but curli is?");
468
469  // Insert the COPY instruction.
470  MachineInstr *MI = BuildMI(MBB, MBB.begin(), DebugLoc(),
471                             tii_.get(TargetOpcode::COPY), dupli_->reg)
472                       .addReg(openli_->reg);
473  SlotIndex Idx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
474
475  // Adjust dupli and openli values.
476  if (isPHIDef) {
477    // dupli was already a PHI on entry to MBB. Simply insert an openli PHI,
478    // and shift the dupli def down to the COPY.
479    VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
480                                        lis_.getVNInfoAllocator());
481    VNI->setIsPHIDef(true);
482    openli_->addRange(LiveRange(VNI->def, Idx, VNI));
483
484    dupli_->removeRange(Start, Idx);
485    DupLR->valno->def = Idx;
486    DupLR->valno->setIsPHIDef(false);
487  } else {
488    // The dupli value was defined somewhere inside the openli range.
489    DEBUG(dbgs() << "  leaveIntvAtTop source value defined at "
490                 << DupLR->valno->def << "\n");
491    // FIXME: We may not need a PHI here if all predecessors have the same
492    // value.
493    VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
494                                        lis_.getVNInfoAllocator());
495    VNI->setIsPHIDef(true);
496    openli_->addRange(LiveRange(VNI->def, Idx, VNI));
497
498    // FIXME: What if DupLR->valno is used by multiple exits? SSA Update.
499
500    // closeIntv is going to remove the superfluous live ranges.
501    DupLR->valno->def = Idx;
502    DupLR->valno->setIsPHIDef(false);
503  }
504
505  DEBUG(dbgs() << "  leaveIntvAtTop at " << Idx << ": " << *openli_ << '\n');
506}
507
508/// closeIntv - Indicate that we are done editing the currently open
509/// LiveInterval, and ranges can be trimmed.
510void SplitEditor::closeIntv() {
511  assert(openli_ && "openIntv not called before closeIntv");
512
513  DEBUG(dbgs() << "  closeIntv cleaning up\n");
514  DEBUG(dbgs() << "    open " << *openli_ << '\n');
515
516  if (liveThrough_) {
517    DEBUG(dbgs() << "  value live through region, leaving dupli as is.\n");
518  } else {
519    // live out with copies inserted, or killed by region. Either way we need to
520    // remove the overlapping region from dupli.
521    getDupLI();
522    for (LiveInterval::iterator I = openli_->begin(), E = openli_->end();
523         I != E; ++I) {
524      dupli_->removeRange(I->start, I->end);
525    }
526    // FIXME: A block branching to the entry block may also branch elsewhere
527    // curli is live. We need both openli and curli to be live in that case.
528    DEBUG(dbgs() << "    dup2 " << *dupli_ << '\n');
529  }
530  openli_ = 0;
531}
532
533/// rewrite - after all the new live ranges have been created, rewrite
534/// instructions using curli to use the new intervals.
535void SplitEditor::rewrite() {
536  assert(!openli_ && "Previous LI not closed before rewrite");
537  const LiveInterval *curli = sa_.getCurLI();
538  for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(curli->reg),
539       RE = mri_.reg_end(); RI != RE;) {
540    MachineOperand &MO = RI.getOperand();
541    MachineInstr *MI = MO.getParent();
542    ++RI;
543    if (MI->isDebugValue()) {
544      DEBUG(dbgs() << "Zapping " << *MI);
545      // FIXME: We can do much better with debug values.
546      MO.setReg(0);
547      continue;
548    }
549    SlotIndex Idx = lis_.getInstructionIndex(MI);
550    Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex();
551    LiveInterval *LI = dupli_;
552    for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
553      LiveInterval *testli = intervals_[i];
554      if (testli->liveAt(Idx)) {
555        LI = testli;
556        break;
557      }
558    }
559    if (LI)
560      MO.setReg(LI->reg);
561    DEBUG(dbgs() << "rewrite " << Idx << '\t' << *MI);
562  }
563
564  // dupli_ goes in last, after rewriting.
565  if (dupli_) {
566    dupli_->RenumberValues();
567    intervals_.push_back(dupli_);
568  }
569
570  // Calculate spill weight and allocation hints for new intervals.
571  VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_);
572  for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
573    LiveInterval &li = *intervals_[i];
574    vrai.CalculateWeightAndHint(li);
575  }
576}
577
578
579//===----------------------------------------------------------------------===//
580//                               Loop Splitting
581//===----------------------------------------------------------------------===//
582
583bool SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
584  SplitAnalysis::LoopBlocks Blocks;
585  sa_.getLoopBlocks(Loop, Blocks);
586
587  // Break critical edges as needed.
588  SplitAnalysis::BlockPtrSet CriticalExits;
589  sa_.getCriticalExits(Blocks, CriticalExits);
590  assert(CriticalExits.empty() && "Cannot break critical exits yet");
591
592  // Create new live interval for the loop.
593  openIntv();
594
595  // Insert copies in the predecessors.
596  for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(),
597       E = Blocks.Preds.end(); I != E; ++I) {
598    MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
599    enterIntvAtEnd(MBB, *Loop->getHeader());
600  }
601
602  // Switch all loop blocks.
603  for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(),
604       E = Blocks.Loop.end(); I != E; ++I)
605     useIntv(**I);
606
607  // Insert back copies in the exit blocks.
608  for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(),
609       E = Blocks.Exits.end(); I != E; ++I) {
610    MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
611    leaveIntvAtTop(MBB);
612  }
613
614  // Done.
615  closeIntv();
616  rewrite();
617  return dupli_;
618}
619
620