Spiller.cpp revision 0363e36c4f3eeb28bf7f069b23735fe39a1f3edc 
1//===-- llvm/CodeGen/Spiller.cpp -  Spiller -------------------------------===//
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#define DEBUG_TYPE "spiller"
11
12#include "Spiller.h"
13#include "VirtRegMap.h"
14#include "llvm/CodeGen/LiveIntervalAnalysis.h"
15#include "llvm/CodeGen/MachineFrameInfo.h"
16#include "llvm/CodeGen/MachineFunction.h"
17#include "llvm/CodeGen/MachineInstrBuilder.h"
18#include "llvm/CodeGen/MachineLoopInfo.h"
19#include "llvm/CodeGen/MachineRegisterInfo.h"
20#include "llvm/Target/TargetMachine.h"
21#include "llvm/Target/TargetInstrInfo.h"
22#include "llvm/Support/CommandLine.h"
23#include "llvm/Support/Debug.h"
24#include "llvm/Support/ErrorHandling.h"
25#include "llvm/Support/raw_ostream.h"
26#include <set>
27
28using namespace llvm;
29
30namespace {
31  enum SpillerName { trivial, standard, splitting, inline_ };
32}
33
34static cl::opt<SpillerName>
35spillerOpt("spiller",
36           cl::desc("Spiller to use: (default: standard)"),
37           cl::Prefix,
38           cl::values(clEnumVal(trivial,   "trivial spiller"),
39                      clEnumVal(standard,  "default spiller"),
40                      clEnumVal(splitting, "splitting spiller"),
41                      clEnumValN(inline_,  "inline", "inline spiller"),
42                      clEnumValEnd),
43           cl::init(standard));
44
45// Spiller virtual destructor implementation.
46Spiller::~Spiller() {}
47
48namespace {
49
50/// Utility class for spillers.
51class SpillerBase : public Spiller {
52protected:
53  MachineFunctionPass *pass;
54  MachineFunction *mf;
55  VirtRegMap *vrm;
56  LiveIntervals *lis;
57  MachineFrameInfo *mfi;
58  MachineRegisterInfo *mri;
59  const TargetInstrInfo *tii;
60  const TargetRegisterInfo *tri;
61
62  /// Construct a spiller base.
63  SpillerBase(MachineFunctionPass &pass, MachineFunction &mf, VirtRegMap &vrm)
64    : pass(&pass), mf(&mf), vrm(&vrm)
65  {
66    lis = &pass.getAnalysis<LiveIntervals>();
67    mfi = mf.getFrameInfo();
68    mri = &mf.getRegInfo();
69    tii = mf.getTarget().getInstrInfo();
70    tri = mf.getTarget().getRegisterInfo();
71  }
72
73  /// Add spill ranges for every use/def of the live interval, inserting loads
74  /// immediately before each use, and stores after each def. No folding or
75  /// remat is attempted.
76  void trivialSpillEverywhere(LiveInterval *li,
77                              SmallVectorImpl<LiveInterval*> &newIntervals) {
78    DEBUG(dbgs() << "Spilling everywhere " << *li << "\n");
79
80    assert(li->weight != HUGE_VALF &&
81           "Attempting to spill already spilled value.");
82
83    assert(!li->isStackSlot() &&
84           "Trying to spill a stack slot.");
85
86    DEBUG(dbgs() << "Trivial spill everywhere of reg" << li->reg << "\n");
87
88    const TargetRegisterClass *trc = mri->getRegClass(li->reg);
89    unsigned ss = vrm->assignVirt2StackSlot(li->reg);
90
91    // Iterate over reg uses/defs.
92    for (MachineRegisterInfo::reg_iterator
93         regItr = mri->reg_begin(li->reg); regItr != mri->reg_end();) {
94
95      // Grab the use/def instr.
96      MachineInstr *mi = &*regItr;
97
98      DEBUG(dbgs() << "  Processing " << *mi);
99
100      // Step regItr to the next use/def instr.
101      do {
102        ++regItr;
103      } while (regItr != mri->reg_end() && (&*regItr == mi));
104
105      // Collect uses & defs for this instr.
106      SmallVector<unsigned, 2> indices;
107      bool hasUse = false;
108      bool hasDef = false;
109      for (unsigned i = 0; i != mi->getNumOperands(); ++i) {
110        MachineOperand &op = mi->getOperand(i);
111        if (!op.isReg() || op.getReg() != li->reg)
112          continue;
113        hasUse |= mi->getOperand(i).isUse();
114        hasDef |= mi->getOperand(i).isDef();
115        indices.push_back(i);
116      }
117
118      // Create a new vreg & interval for this instr.
119      unsigned newVReg = mri->createVirtualRegister(trc);
120      vrm->grow();
121      vrm->assignVirt2StackSlot(newVReg, ss);
122      LiveInterval *newLI = &lis->getOrCreateInterval(newVReg);
123      newLI->weight = HUGE_VALF;
124
125      // Update the reg operands & kill flags.
126      for (unsigned i = 0; i < indices.size(); ++i) {
127        unsigned mopIdx = indices[i];
128        MachineOperand &mop = mi->getOperand(mopIdx);
129        mop.setReg(newVReg);
130        if (mop.isUse() && !mi->isRegTiedToDefOperand(mopIdx)) {
131          mop.setIsKill(true);
132        }
133      }
134      assert(hasUse || hasDef);
135
136      // Insert reload if necessary.
137      MachineBasicBlock::iterator miItr(mi);
138      if (hasUse) {
139        tii->loadRegFromStackSlot(*mi->getParent(), miItr, newVReg, ss, trc,
140                                  tri);
141        MachineInstr *loadInstr(prior(miItr));
142        SlotIndex loadIndex =
143          lis->InsertMachineInstrInMaps(loadInstr).getDefIndex();
144        vrm->addSpillSlotUse(ss, loadInstr);
145        SlotIndex endIndex = loadIndex.getNextIndex();
146        VNInfo *loadVNI =
147          newLI->getNextValue(loadIndex, 0, true, lis->getVNInfoAllocator());
148        newLI->addRange(LiveRange(loadIndex, endIndex, loadVNI));
149      }
150
151      // Insert store if necessary.
152      if (hasDef) {
153        tii->storeRegToStackSlot(*mi->getParent(), llvm::next(miItr), newVReg,
154                                 true, ss, trc, tri);
155        MachineInstr *storeInstr(llvm::next(miItr));
156        SlotIndex storeIndex =
157          lis->InsertMachineInstrInMaps(storeInstr).getDefIndex();
158        vrm->addSpillSlotUse(ss, storeInstr);
159        SlotIndex beginIndex = storeIndex.getPrevIndex();
160        VNInfo *storeVNI =
161          newLI->getNextValue(beginIndex, 0, true, lis->getVNInfoAllocator());
162        newLI->addRange(LiveRange(beginIndex, storeIndex, storeVNI));
163      }
164
165      newIntervals.push_back(newLI);
166    }
167  }
168};
169
170} // end anonymous namespace
171
172namespace {
173
174/// Spills any live range using the spill-everywhere method with no attempt at
175/// folding.
176class TrivialSpiller : public SpillerBase {
177public:
178
179  TrivialSpiller(MachineFunctionPass &pass, MachineFunction &mf,
180                 VirtRegMap &vrm)
181    : SpillerBase(pass, mf, vrm) {}
182
183  void spill(LiveInterval *li,
184             SmallVectorImpl<LiveInterval*> &newIntervals,
185             SmallVectorImpl<LiveInterval*> &) {
186    // Ignore spillIs - we don't use it.
187    trivialSpillEverywhere(li, newIntervals);
188  }
189};
190
191} // end anonymous namespace
192
193namespace {
194
195/// Falls back on LiveIntervals::addIntervalsForSpills.
196class StandardSpiller : public Spiller {
197protected:
198  LiveIntervals *lis;
199  MachineLoopInfo *loopInfo;
200  VirtRegMap *vrm;
201public:
202  StandardSpiller(MachineFunctionPass &pass, MachineFunction &mf,
203                  VirtRegMap &vrm)
204    : lis(&pass.getAnalysis<LiveIntervals>()),
205      loopInfo(pass.getAnalysisIfAvailable<MachineLoopInfo>()),
206      vrm(&vrm) {}
207
208  /// Falls back on LiveIntervals::addIntervalsForSpills.
209  void spill(LiveInterval *li,
210             SmallVectorImpl<LiveInterval*> &newIntervals,
211             SmallVectorImpl<LiveInterval*> &spillIs) {
212    std::vector<LiveInterval*> added =
213      lis->addIntervalsForSpills(*li, spillIs, loopInfo, *vrm);
214    newIntervals.insert(newIntervals.end(), added.begin(), added.end());
215  }
216};
217
218} // end anonymous namespace
219
220namespace {
221
222/// When a call to spill is placed this spiller will first try to break the
223/// interval up into its component values (one new interval per value).
224/// If this fails, or if a call is placed to spill a previously split interval
225/// then the spiller falls back on the standard spilling mechanism.
226class SplittingSpiller : public StandardSpiller {
227public:
228  SplittingSpiller(MachineFunctionPass &pass, MachineFunction &mf,
229                   VirtRegMap &vrm)
230    : StandardSpiller(pass, mf, vrm) {
231    mri = &mf.getRegInfo();
232    tii = mf.getTarget().getInstrInfo();
233    tri = mf.getTarget().getRegisterInfo();
234  }
235
236  void spill(LiveInterval *li,
237             SmallVectorImpl<LiveInterval*> &newIntervals,
238             SmallVectorImpl<LiveInterval*> &spillIs) {
239    if (worthTryingToSplit(li))
240      tryVNISplit(li);
241    else
242      StandardSpiller::spill(li, newIntervals, spillIs);
243  }
244
245private:
246
247  MachineRegisterInfo *mri;
248  const TargetInstrInfo *tii;
249  const TargetRegisterInfo *tri;
250  DenseSet<LiveInterval*> alreadySplit;
251
252  bool worthTryingToSplit(LiveInterval *li) const {
253    return (!alreadySplit.count(li) && li->getNumValNums() > 1);
254  }
255
256  /// Try to break a LiveInterval into its component values.
257  std::vector<LiveInterval*> tryVNISplit(LiveInterval *li) {
258
259    DEBUG(dbgs() << "Trying VNI split of %reg" << *li << "\n");
260
261    std::vector<LiveInterval*> added;
262    SmallVector<VNInfo*, 4> vnis;
263
264    std::copy(li->vni_begin(), li->vni_end(), std::back_inserter(vnis));
265
266    for (SmallVectorImpl<VNInfo*>::iterator vniItr = vnis.begin(),
267         vniEnd = vnis.end(); vniItr != vniEnd; ++vniItr) {
268      VNInfo *vni = *vniItr;
269
270      // Skip unused VNIs.
271      if (vni->isUnused())
272        continue;
273
274      DEBUG(dbgs() << "  Extracted Val #" << vni->id << " as ");
275      LiveInterval *splitInterval = extractVNI(li, vni);
276
277      if (splitInterval != 0) {
278        DEBUG(dbgs() << *splitInterval << "\n");
279        added.push_back(splitInterval);
280        alreadySplit.insert(splitInterval);
281      } else {
282        DEBUG(dbgs() << "0\n");
283      }
284    }
285
286    DEBUG(dbgs() << "Original LI: " << *li << "\n");
287
288    // If there original interval still contains some live ranges
289    // add it to added and alreadySplit.
290    if (!li->empty()) {
291      added.push_back(li);
292      alreadySplit.insert(li);
293    }
294
295    return added;
296  }
297
298  /// Extract the given value number from the interval.
299  LiveInterval* extractVNI(LiveInterval *li, VNInfo *vni) const {
300    assert(vni->isDefAccurate() || vni->isPHIDef());
301
302    // Create a new vreg and live interval, copy VNI ranges over.
303    const TargetRegisterClass *trc = mri->getRegClass(li->reg);
304    unsigned newVReg = mri->createVirtualRegister(trc);
305    vrm->grow();
306    LiveInterval *newLI = &lis->getOrCreateInterval(newVReg);
307    VNInfo *newVNI = newLI->createValueCopy(vni, lis->getVNInfoAllocator());
308
309    // Start by copying all live ranges in the VN to the new interval.
310    for (LiveInterval::iterator rItr = li->begin(), rEnd = li->end();
311         rItr != rEnd; ++rItr) {
312      if (rItr->valno == vni) {
313        newLI->addRange(LiveRange(rItr->start, rItr->end, newVNI));
314      }
315    }
316
317    // Erase the old VNI & ranges.
318    li->removeValNo(vni);
319
320    // Collect all current uses of the register belonging to the given VNI.
321    // We'll use this to rename the register after we've dealt with the def.
322    std::set<MachineInstr*> uses;
323    for (MachineRegisterInfo::use_iterator
324         useItr = mri->use_begin(li->reg), useEnd = mri->use_end();
325         useItr != useEnd; ++useItr) {
326      uses.insert(&*useItr);
327    }
328
329    // Process the def instruction for this VNI.
330    if (newVNI->isPHIDef()) {
331      // Insert a copy at the start of the MBB. The range proceeding the
332      // copy will be attached to the original LiveInterval.
333      MachineBasicBlock *defMBB = lis->getMBBFromIndex(newVNI->def);
334      MachineInstr *copyMI = BuildMI(*defMBB, defMBB->begin(), DebugLoc(),
335                                     tii->get(TargetOpcode::COPY), newVReg)
336                               .addReg(li->reg, RegState::Kill);
337      SlotIndex copyIdx = lis->InsertMachineInstrInMaps(copyMI);
338      VNInfo *phiDefVNI = li->getNextValue(lis->getMBBStartIdx(defMBB),
339                                           0, false, lis->getVNInfoAllocator());
340      phiDefVNI->setIsPHIDef(true);
341      li->addRange(LiveRange(phiDefVNI->def, copyIdx.getDefIndex(), phiDefVNI));
342      LiveRange *oldPHIDefRange =
343        newLI->getLiveRangeContaining(lis->getMBBStartIdx(defMBB));
344
345      // If the old phi def starts in the middle of the range chop it up.
346      if (oldPHIDefRange->start < lis->getMBBStartIdx(defMBB)) {
347        LiveRange oldPHIDefRange2(copyIdx.getDefIndex(), oldPHIDefRange->end,
348                                  oldPHIDefRange->valno);
349        oldPHIDefRange->end = lis->getMBBStartIdx(defMBB);
350        newLI->addRange(oldPHIDefRange2);
351      } else if (oldPHIDefRange->start == lis->getMBBStartIdx(defMBB)) {
352        // Otherwise if it's at the start of the range just trim it.
353        oldPHIDefRange->start = copyIdx.getDefIndex();
354      } else {
355        assert(false && "PHI def range doesn't cover PHI def?");
356      }
357
358      newVNI->def = copyIdx.getDefIndex();
359      newVNI->setCopy(copyMI);
360      newVNI->setIsPHIDef(false); // not a PHI def anymore.
361      newVNI->setIsDefAccurate(true);
362    } else {
363      // non-PHI def. Rename the def. If it's two-addr that means renaming the
364      // use and inserting a new copy too.
365      MachineInstr *defInst = lis->getInstructionFromIndex(newVNI->def);
366      // We'll rename this now, so we can remove it from uses.
367      uses.erase(defInst);
368      unsigned defOpIdx = defInst->findRegisterDefOperandIdx(li->reg);
369      bool isTwoAddr = defInst->isRegTiedToUseOperand(defOpIdx),
370        twoAddrUseIsUndef = false;
371
372      for (unsigned i = 0; i < defInst->getNumOperands(); ++i) {
373        MachineOperand &mo = defInst->getOperand(i);
374        if (mo.isReg() && (mo.isDef() || isTwoAddr) && (mo.getReg()==li->reg)) {
375          mo.setReg(newVReg);
376          if (isTwoAddr && mo.isUse() && mo.isUndef())
377            twoAddrUseIsUndef = true;
378        }
379      }
380
381      SlotIndex defIdx = lis->getInstructionIndex(defInst);
382      newVNI->def = defIdx.getDefIndex();
383
384      if (isTwoAddr && !twoAddrUseIsUndef) {
385        MachineBasicBlock *defMBB = defInst->getParent();
386        MachineInstr *copyMI = BuildMI(*defMBB, defInst, DebugLoc(),
387                                       tii->get(TargetOpcode::COPY), newVReg)
388                                 .addReg(li->reg, RegState::Kill);
389        SlotIndex copyIdx = lis->InsertMachineInstrInMaps(copyMI);
390        LiveRange *origUseRange =
391          li->getLiveRangeContaining(newVNI->def.getUseIndex());
392        origUseRange->end = copyIdx.getDefIndex();
393        VNInfo *copyVNI = newLI->getNextValue(copyIdx.getDefIndex(), copyMI,
394                                              true, lis->getVNInfoAllocator());
395        LiveRange copyRange(copyIdx.getDefIndex(),defIdx.getDefIndex(),copyVNI);
396        newLI->addRange(copyRange);
397      }
398    }
399
400    for (std::set<MachineInstr*>::iterator
401         usesItr = uses.begin(), usesEnd = uses.end();
402         usesItr != usesEnd; ++usesItr) {
403      MachineInstr *useInst = *usesItr;
404      SlotIndex useIdx = lis->getInstructionIndex(useInst);
405      LiveRange *useRange =
406        newLI->getLiveRangeContaining(useIdx.getUseIndex());
407
408      // If this use doesn't belong to the new interval skip it.
409      if (useRange == 0)
410        continue;
411
412      // This use doesn't belong to the VNI, skip it.
413      if (useRange->valno != newVNI)
414        continue;
415
416      // Check if this instr is two address.
417      unsigned useOpIdx = useInst->findRegisterUseOperandIdx(li->reg);
418      bool isTwoAddress = useInst->isRegTiedToDefOperand(useOpIdx);
419
420      // Rename uses (and defs for two-address instrs).
421      for (unsigned i = 0; i < useInst->getNumOperands(); ++i) {
422        MachineOperand &mo = useInst->getOperand(i);
423        if (mo.isReg() && (mo.isUse() || isTwoAddress) &&
424            (mo.getReg() == li->reg)) {
425          mo.setReg(newVReg);
426        }
427      }
428
429      // If this is a two address instruction we've got some extra work to do.
430      if (isTwoAddress) {
431        // We modified the def operand, so we need to copy back to the original
432        // reg.
433        MachineBasicBlock *useMBB = useInst->getParent();
434        MachineBasicBlock::iterator useItr(useInst);
435        MachineInstr *copyMI = BuildMI(*useMBB, llvm::next(useItr), DebugLoc(),
436                                       tii->get(TargetOpcode::COPY), newVReg)
437                                 .addReg(li->reg, RegState::Kill);
438        SlotIndex copyIdx = lis->InsertMachineInstrInMaps(copyMI);
439
440        // Change the old two-address defined range & vni to start at
441        // (and be defined by) the copy.
442        LiveRange *origDefRange =
443          li->getLiveRangeContaining(useIdx.getDefIndex());
444        origDefRange->start = copyIdx.getDefIndex();
445        origDefRange->valno->def = copyIdx.getDefIndex();
446        origDefRange->valno->setCopy(copyMI);
447
448        // Insert a new range & vni for the two-address-to-copy value. This
449        // will be attached to the new live interval.
450        VNInfo *copyVNI =
451          newLI->getNextValue(useIdx.getDefIndex(), 0, true,
452                              lis->getVNInfoAllocator());
453        LiveRange copyRange(useIdx.getDefIndex(),copyIdx.getDefIndex(),copyVNI);
454        newLI->addRange(copyRange);
455      }
456    }
457
458    // Iterate over any PHI kills - we'll need to insert new copies for them.
459    for (LiveInterval::iterator LRI = newLI->begin(), LRE = newLI->end();
460         LRI != LRE; ++LRI) {
461      if (LRI->valno != newVNI)
462        continue;
463      SlotIndex killIdx = LRI->end;
464      MachineBasicBlock *killMBB = lis->getMBBFromIndex(killIdx);
465      MachineInstr *copyMI = BuildMI(*killMBB, killMBB->getFirstTerminator(),
466                                     DebugLoc(), tii->get(TargetOpcode::COPY),
467                                     li->reg)
468                               .addReg(newVReg, RegState::Kill);
469      SlotIndex copyIdx = lis->InsertMachineInstrInMaps(copyMI);
470
471      // Save the current end. We may need it to add a new range if the
472      // current range runs of the end of the MBB.
473      SlotIndex newKillRangeEnd = LRI->end;
474      LRI->end = copyIdx.getDefIndex();
475
476      if (newKillRangeEnd != lis->getMBBEndIdx(killMBB)) {
477        assert(newKillRangeEnd > lis->getMBBEndIdx(killMBB) &&
478               "PHI kill range doesn't reach kill-block end. Not sane.");
479        newLI->addRange(LiveRange(lis->getMBBEndIdx(killMBB),
480                                  newKillRangeEnd, newVNI));
481      }
482
483      VNInfo *newKillVNI = li->getNextValue(copyIdx.getDefIndex(),
484                                            copyMI, true,
485                                            lis->getVNInfoAllocator());
486      newKillVNI->setHasPHIKill(true);
487      li->addRange(LiveRange(copyIdx.getDefIndex(),
488                             lis->getMBBEndIdx(killMBB),
489                             newKillVNI));
490    }
491    newVNI->setHasPHIKill(false);
492
493    return newLI;
494  }
495
496};
497
498} // end anonymous namespace
499
500
501namespace llvm {
502Spiller *createInlineSpiller(MachineFunctionPass &pass,
503                             MachineFunction &mf,
504                             VirtRegMap &vrm);
505}
506
507llvm::Spiller* llvm::createSpiller(MachineFunctionPass &pass,
508                                   MachineFunction &mf,
509                                   VirtRegMap &vrm) {
510  switch (spillerOpt) {
511  default: assert(0 && "unknown spiller");
512  case trivial: return new TrivialSpiller(pass, mf, vrm);
513  case standard: return new StandardSpiller(pass, mf, vrm);
514  case splitting: return new SplittingSpiller(pass, mf, vrm);
515  case inline_: return createInlineSpiller(pass, mf, vrm);
516  }
517}
518