1 //===-- LiveInterval.cpp - Live Interval Representation -------------------===//
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 implements the LiveRange and LiveInterval classes.  Given some
11 // numbering of each the machine instructions an interval [i, j) is said to be a
12 // live range for register v if there is no instruction with number j' >= j
13 // such that v is live at j' and there is no instruction with number i' < i such
14 // that v is live at i'. In this implementation ranges can have holes,
15 // i.e. a range might look like [1,20), [50,65), [1000,1001).  Each
16 // individual segment is represented as an instance of LiveRange::Segment,
17 // and the whole range is represented as an instance of LiveRange.
18 //
19 //===----------------------------------------------------------------------===//
20 
21 #include "llvm/CodeGen/LiveInterval.h"
22 
23 #include "LiveRangeUtils.h"
24 #include "RegisterCoalescer.h"
25 #include "llvm/ADT/STLExtras.h"
26 #include "llvm/ADT/SmallSet.h"
27 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
28 #include "llvm/CodeGen/MachineRegisterInfo.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include "llvm/Target/TargetRegisterInfo.h"
32 #include <algorithm>
33 using namespace llvm;
34 
35 namespace {
36 //===----------------------------------------------------------------------===//
37 // Implementation of various methods necessary for calculation of live ranges.
38 // The implementation of the methods abstracts from the concrete type of the
39 // segment collection.
40 //
41 // Implementation of the class follows the Template design pattern. The base
42 // class contains generic algorithms that call collection-specific methods,
43 // which are provided in concrete subclasses. In order to avoid virtual calls
44 // these methods are provided by means of C++ template instantiation.
45 // The base class calls the methods of the subclass through method impl(),
46 // which casts 'this' pointer to the type of the subclass.
47 //
48 //===----------------------------------------------------------------------===//
49 
50 template <typename ImplT, typename IteratorT, typename CollectionT>
51 class CalcLiveRangeUtilBase {
52 protected:
53   LiveRange *LR;
54 
55 protected:
CalcLiveRangeUtilBase(LiveRange * LR)56   CalcLiveRangeUtilBase(LiveRange *LR) : LR(LR) {}
57 
58 public:
59   typedef LiveRange::Segment Segment;
60   typedef IteratorT iterator;
61 
createDeadDef(SlotIndex Def,VNInfo::Allocator & VNInfoAllocator)62   VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator) {
63     assert(!Def.isDead() && "Cannot define a value at the dead slot");
64 
65     iterator I = impl().find(Def);
66     if (I == segments().end()) {
67       VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
68       impl().insertAtEnd(Segment(Def, Def.getDeadSlot(), VNI));
69       return VNI;
70     }
71 
72     Segment *S = segmentAt(I);
73     if (SlotIndex::isSameInstr(Def, S->start)) {
74       assert(S->valno->def == S->start && "Inconsistent existing value def");
75 
76       // It is possible to have both normal and early-clobber defs of the same
77       // register on an instruction. It doesn't make a lot of sense, but it is
78       // possible to specify in inline assembly.
79       //
80       // Just convert everything to early-clobber.
81       Def = std::min(Def, S->start);
82       if (Def != S->start)
83         S->start = S->valno->def = Def;
84       return S->valno;
85     }
86     assert(SlotIndex::isEarlierInstr(Def, S->start) && "Already live at def");
87     VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
88     segments().insert(I, Segment(Def, Def.getDeadSlot(), VNI));
89     return VNI;
90   }
91 
extendInBlock(SlotIndex StartIdx,SlotIndex Use)92   VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Use) {
93     if (segments().empty())
94       return nullptr;
95     iterator I =
96         impl().findInsertPos(Segment(Use.getPrevSlot(), Use, nullptr));
97     if (I == segments().begin())
98       return nullptr;
99     --I;
100     if (I->end <= StartIdx)
101       return nullptr;
102     if (I->end < Use)
103       extendSegmentEndTo(I, Use);
104     return I->valno;
105   }
106 
107   /// This method is used when we want to extend the segment specified
108   /// by I to end at the specified endpoint. To do this, we should
109   /// merge and eliminate all segments that this will overlap
110   /// with. The iterator is not invalidated.
extendSegmentEndTo(iterator I,SlotIndex NewEnd)111   void extendSegmentEndTo(iterator I, SlotIndex NewEnd) {
112     assert(I != segments().end() && "Not a valid segment!");
113     Segment *S = segmentAt(I);
114     VNInfo *ValNo = I->valno;
115 
116     // Search for the first segment that we can't merge with.
117     iterator MergeTo = std::next(I);
118     for (; MergeTo != segments().end() && NewEnd >= MergeTo->end; ++MergeTo)
119       assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
120 
121     // If NewEnd was in the middle of a segment, make sure to get its endpoint.
122     S->end = std::max(NewEnd, std::prev(MergeTo)->end);
123 
124     // If the newly formed segment now touches the segment after it and if they
125     // have the same value number, merge the two segments into one segment.
126     if (MergeTo != segments().end() && MergeTo->start <= I->end &&
127         MergeTo->valno == ValNo) {
128       S->end = MergeTo->end;
129       ++MergeTo;
130     }
131 
132     // Erase any dead segments.
133     segments().erase(std::next(I), MergeTo);
134   }
135 
136   /// This method is used when we want to extend the segment specified
137   /// by I to start at the specified endpoint.  To do this, we should
138   /// merge and eliminate all segments that this will overlap with.
extendSegmentStartTo(iterator I,SlotIndex NewStart)139   iterator extendSegmentStartTo(iterator I, SlotIndex NewStart) {
140     assert(I != segments().end() && "Not a valid segment!");
141     Segment *S = segmentAt(I);
142     VNInfo *ValNo = I->valno;
143 
144     // Search for the first segment that we can't merge with.
145     iterator MergeTo = I;
146     do {
147       if (MergeTo == segments().begin()) {
148         S->start = NewStart;
149         segments().erase(MergeTo, I);
150         return I;
151       }
152       assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
153       --MergeTo;
154     } while (NewStart <= MergeTo->start);
155 
156     // If we start in the middle of another segment, just delete a range and
157     // extend that segment.
158     if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
159       segmentAt(MergeTo)->end = S->end;
160     } else {
161       // Otherwise, extend the segment right after.
162       ++MergeTo;
163       Segment *MergeToSeg = segmentAt(MergeTo);
164       MergeToSeg->start = NewStart;
165       MergeToSeg->end = S->end;
166     }
167 
168     segments().erase(std::next(MergeTo), std::next(I));
169     return MergeTo;
170   }
171 
addSegment(Segment S)172   iterator addSegment(Segment S) {
173     SlotIndex Start = S.start, End = S.end;
174     iterator I = impl().findInsertPos(S);
175 
176     // If the inserted segment starts in the middle or right at the end of
177     // another segment, just extend that segment to contain the segment of S.
178     if (I != segments().begin()) {
179       iterator B = std::prev(I);
180       if (S.valno == B->valno) {
181         if (B->start <= Start && B->end >= Start) {
182           extendSegmentEndTo(B, End);
183           return B;
184         }
185       } else {
186         // Check to make sure that we are not overlapping two live segments with
187         // different valno's.
188         assert(B->end <= Start &&
189                "Cannot overlap two segments with differing ValID's"
190                " (did you def the same reg twice in a MachineInstr?)");
191       }
192     }
193 
194     // Otherwise, if this segment ends in the middle of, or right next
195     // to, another segment, merge it into that segment.
196     if (I != segments().end()) {
197       if (S.valno == I->valno) {
198         if (I->start <= End) {
199           I = extendSegmentStartTo(I, Start);
200 
201           // If S is a complete superset of a segment, we may need to grow its
202           // endpoint as well.
203           if (End > I->end)
204             extendSegmentEndTo(I, End);
205           return I;
206         }
207       } else {
208         // Check to make sure that we are not overlapping two live segments with
209         // different valno's.
210         assert(I->start >= End &&
211                "Cannot overlap two segments with differing ValID's");
212       }
213     }
214 
215     // Otherwise, this is just a new segment that doesn't interact with
216     // anything.
217     // Insert it.
218     return segments().insert(I, S);
219   }
220 
221 private:
impl()222   ImplT &impl() { return *static_cast<ImplT *>(this); }
223 
segments()224   CollectionT &segments() { return impl().segmentsColl(); }
225 
segmentAt(iterator I)226   Segment *segmentAt(iterator I) { return const_cast<Segment *>(&(*I)); }
227 };
228 
229 //===----------------------------------------------------------------------===//
230 //   Instantiation of the methods for calculation of live ranges
231 //   based on a segment vector.
232 //===----------------------------------------------------------------------===//
233 
234 class CalcLiveRangeUtilVector;
235 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilVector, LiveRange::iterator,
236                               LiveRange::Segments> CalcLiveRangeUtilVectorBase;
237 
238 class CalcLiveRangeUtilVector : public CalcLiveRangeUtilVectorBase {
239 public:
CalcLiveRangeUtilVector(LiveRange * LR)240   CalcLiveRangeUtilVector(LiveRange *LR) : CalcLiveRangeUtilVectorBase(LR) {}
241 
242 private:
243   friend CalcLiveRangeUtilVectorBase;
244 
segmentsColl()245   LiveRange::Segments &segmentsColl() { return LR->segments; }
246 
insertAtEnd(const Segment & S)247   void insertAtEnd(const Segment &S) { LR->segments.push_back(S); }
248 
find(SlotIndex Pos)249   iterator find(SlotIndex Pos) { return LR->find(Pos); }
250 
findInsertPos(Segment S)251   iterator findInsertPos(Segment S) {
252     return std::upper_bound(LR->begin(), LR->end(), S.start);
253   }
254 };
255 
256 //===----------------------------------------------------------------------===//
257 //   Instantiation of the methods for calculation of live ranges
258 //   based on a segment set.
259 //===----------------------------------------------------------------------===//
260 
261 class CalcLiveRangeUtilSet;
262 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilSet,
263                               LiveRange::SegmentSet::iterator,
264                               LiveRange::SegmentSet> CalcLiveRangeUtilSetBase;
265 
266 class CalcLiveRangeUtilSet : public CalcLiveRangeUtilSetBase {
267 public:
CalcLiveRangeUtilSet(LiveRange * LR)268   CalcLiveRangeUtilSet(LiveRange *LR) : CalcLiveRangeUtilSetBase(LR) {}
269 
270 private:
271   friend CalcLiveRangeUtilSetBase;
272 
segmentsColl()273   LiveRange::SegmentSet &segmentsColl() { return *LR->segmentSet; }
274 
insertAtEnd(const Segment & S)275   void insertAtEnd(const Segment &S) {
276     LR->segmentSet->insert(LR->segmentSet->end(), S);
277   }
278 
find(SlotIndex Pos)279   iterator find(SlotIndex Pos) {
280     iterator I =
281         LR->segmentSet->upper_bound(Segment(Pos, Pos.getNextSlot(), nullptr));
282     if (I == LR->segmentSet->begin())
283       return I;
284     iterator PrevI = std::prev(I);
285     if (Pos < (*PrevI).end)
286       return PrevI;
287     return I;
288   }
289 
findInsertPos(Segment S)290   iterator findInsertPos(Segment S) {
291     iterator I = LR->segmentSet->upper_bound(S);
292     if (I != LR->segmentSet->end() && !(S.start < *I))
293       ++I;
294     return I;
295   }
296 };
297 } // namespace
298 
299 //===----------------------------------------------------------------------===//
300 //   LiveRange methods
301 //===----------------------------------------------------------------------===//
302 
find(SlotIndex Pos)303 LiveRange::iterator LiveRange::find(SlotIndex Pos) {
304   // This algorithm is basically std::upper_bound.
305   // Unfortunately, std::upper_bound cannot be used with mixed types until we
306   // adopt C++0x. Many libraries can do it, but not all.
307   if (empty() || Pos >= endIndex())
308     return end();
309   iterator I = begin();
310   size_t Len = size();
311   do {
312     size_t Mid = Len >> 1;
313     if (Pos < I[Mid].end) {
314       Len = Mid;
315     } else {
316       I += Mid + 1;
317       Len -= Mid + 1;
318     }
319   } while (Len);
320   return I;
321 }
322 
createDeadDef(SlotIndex Def,VNInfo::Allocator & VNInfoAllocator)323 VNInfo *LiveRange::createDeadDef(SlotIndex Def,
324                                   VNInfo::Allocator &VNInfoAllocator) {
325   // Use the segment set, if it is available.
326   if (segmentSet != nullptr)
327     return CalcLiveRangeUtilSet(this).createDeadDef(Def, VNInfoAllocator);
328   // Otherwise use the segment vector.
329   return CalcLiveRangeUtilVector(this).createDeadDef(Def, VNInfoAllocator);
330 }
331 
332 // overlaps - Return true if the intersection of the two live ranges is
333 // not empty.
334 //
335 // An example for overlaps():
336 //
337 // 0: A = ...
338 // 4: B = ...
339 // 8: C = A + B ;; last use of A
340 //
341 // The live ranges should look like:
342 //
343 // A = [3, 11)
344 // B = [7, x)
345 // C = [11, y)
346 //
347 // A->overlaps(C) should return false since we want to be able to join
348 // A and C.
349 //
overlapsFrom(const LiveRange & other,const_iterator StartPos) const350 bool LiveRange::overlapsFrom(const LiveRange& other,
351                              const_iterator StartPos) const {
352   assert(!empty() && "empty range");
353   const_iterator i = begin();
354   const_iterator ie = end();
355   const_iterator j = StartPos;
356   const_iterator je = other.end();
357 
358   assert((StartPos->start <= i->start || StartPos == other.begin()) &&
359          StartPos != other.end() && "Bogus start position hint!");
360 
361   if (i->start < j->start) {
362     i = std::upper_bound(i, ie, j->start);
363     if (i != begin()) --i;
364   } else if (j->start < i->start) {
365     ++StartPos;
366     if (StartPos != other.end() && StartPos->start <= i->start) {
367       assert(StartPos < other.end() && i < end());
368       j = std::upper_bound(j, je, i->start);
369       if (j != other.begin()) --j;
370     }
371   } else {
372     return true;
373   }
374 
375   if (j == je) return false;
376 
377   while (i != ie) {
378     if (i->start > j->start) {
379       std::swap(i, j);
380       std::swap(ie, je);
381     }
382 
383     if (i->end > j->start)
384       return true;
385     ++i;
386   }
387 
388   return false;
389 }
390 
overlaps(const LiveRange & Other,const CoalescerPair & CP,const SlotIndexes & Indexes) const391 bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
392                          const SlotIndexes &Indexes) const {
393   assert(!empty() && "empty range");
394   if (Other.empty())
395     return false;
396 
397   // Use binary searches to find initial positions.
398   const_iterator I = find(Other.beginIndex());
399   const_iterator IE = end();
400   if (I == IE)
401     return false;
402   const_iterator J = Other.find(I->start);
403   const_iterator JE = Other.end();
404   if (J == JE)
405     return false;
406 
407   for (;;) {
408     // J has just been advanced to satisfy:
409     assert(J->end >= I->start);
410     // Check for an overlap.
411     if (J->start < I->end) {
412       // I and J are overlapping. Find the later start.
413       SlotIndex Def = std::max(I->start, J->start);
414       // Allow the overlap if Def is a coalescable copy.
415       if (Def.isBlock() ||
416           !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
417         return true;
418     }
419     // Advance the iterator that ends first to check for more overlaps.
420     if (J->end > I->end) {
421       std::swap(I, J);
422       std::swap(IE, JE);
423     }
424     // Advance J until J->end >= I->start.
425     do
426       if (++J == JE)
427         return false;
428     while (J->end < I->start);
429   }
430 }
431 
432 /// overlaps - Return true if the live range overlaps an interval specified
433 /// by [Start, End).
overlaps(SlotIndex Start,SlotIndex End) const434 bool LiveRange::overlaps(SlotIndex Start, SlotIndex End) const {
435   assert(Start < End && "Invalid range");
436   const_iterator I = std::lower_bound(begin(), end(), End);
437   return I != begin() && (--I)->end > Start;
438 }
439 
covers(const LiveRange & Other) const440 bool LiveRange::covers(const LiveRange &Other) const {
441   if (empty())
442     return Other.empty();
443 
444   const_iterator I = begin();
445   for (const Segment &O : Other.segments) {
446     I = advanceTo(I, O.start);
447     if (I == end() || I->start > O.start)
448       return false;
449 
450     // Check adjacent live segments and see if we can get behind O.end.
451     while (I->end < O.end) {
452       const_iterator Last = I;
453       // Get next segment and abort if it was not adjacent.
454       ++I;
455       if (I == end() || Last->end != I->start)
456         return false;
457     }
458   }
459   return true;
460 }
461 
462 /// ValNo is dead, remove it.  If it is the largest value number, just nuke it
463 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
464 /// it can be nuked later.
markValNoForDeletion(VNInfo * ValNo)465 void LiveRange::markValNoForDeletion(VNInfo *ValNo) {
466   if (ValNo->id == getNumValNums()-1) {
467     do {
468       valnos.pop_back();
469     } while (!valnos.empty() && valnos.back()->isUnused());
470   } else {
471     ValNo->markUnused();
472   }
473 }
474 
475 /// RenumberValues - Renumber all values in order of appearance and delete the
476 /// remaining unused values.
RenumberValues()477 void LiveRange::RenumberValues() {
478   SmallPtrSet<VNInfo*, 8> Seen;
479   valnos.clear();
480   for (const Segment &S : segments) {
481     VNInfo *VNI = S.valno;
482     if (!Seen.insert(VNI).second)
483       continue;
484     assert(!VNI->isUnused() && "Unused valno used by live segment");
485     VNI->id = (unsigned)valnos.size();
486     valnos.push_back(VNI);
487   }
488 }
489 
addSegmentToSet(Segment S)490 void LiveRange::addSegmentToSet(Segment S) {
491   CalcLiveRangeUtilSet(this).addSegment(S);
492 }
493 
addSegment(Segment S)494 LiveRange::iterator LiveRange::addSegment(Segment S) {
495   // Use the segment set, if it is available.
496   if (segmentSet != nullptr) {
497     addSegmentToSet(S);
498     return end();
499   }
500   // Otherwise use the segment vector.
501   return CalcLiveRangeUtilVector(this).addSegment(S);
502 }
503 
append(const Segment S)504 void LiveRange::append(const Segment S) {
505   // Check that the segment belongs to the back of the list.
506   assert(segments.empty() || segments.back().end <= S.start);
507   segments.push_back(S);
508 }
509 
510 /// extendInBlock - If this range is live before Kill in the basic
511 /// block that starts at StartIdx, extend it to be live up to Kill and return
512 /// the value. If there is no live range before Kill, return NULL.
extendInBlock(SlotIndex StartIdx,SlotIndex Kill)513 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
514   // Use the segment set, if it is available.
515   if (segmentSet != nullptr)
516     return CalcLiveRangeUtilSet(this).extendInBlock(StartIdx, Kill);
517   // Otherwise use the segment vector.
518   return CalcLiveRangeUtilVector(this).extendInBlock(StartIdx, Kill);
519 }
520 
521 /// Remove the specified segment from this range.  Note that the segment must
522 /// be in a single Segment in its entirety.
removeSegment(SlotIndex Start,SlotIndex End,bool RemoveDeadValNo)523 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
524                               bool RemoveDeadValNo) {
525   // Find the Segment containing this span.
526   iterator I = find(Start);
527   assert(I != end() && "Segment is not in range!");
528   assert(I->containsInterval(Start, End)
529          && "Segment is not entirely in range!");
530 
531   // If the span we are removing is at the start of the Segment, adjust it.
532   VNInfo *ValNo = I->valno;
533   if (I->start == Start) {
534     if (I->end == End) {
535       if (RemoveDeadValNo) {
536         // Check if val# is dead.
537         bool isDead = true;
538         for (const_iterator II = begin(), EE = end(); II != EE; ++II)
539           if (II != I && II->valno == ValNo) {
540             isDead = false;
541             break;
542           }
543         if (isDead) {
544           // Now that ValNo is dead, remove it.
545           markValNoForDeletion(ValNo);
546         }
547       }
548 
549       segments.erase(I);  // Removed the whole Segment.
550     } else
551       I->start = End;
552     return;
553   }
554 
555   // Otherwise if the span we are removing is at the end of the Segment,
556   // adjust the other way.
557   if (I->end == End) {
558     I->end = Start;
559     return;
560   }
561 
562   // Otherwise, we are splitting the Segment into two pieces.
563   SlotIndex OldEnd = I->end;
564   I->end = Start;   // Trim the old segment.
565 
566   // Insert the new one.
567   segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
568 }
569 
570 /// removeValNo - Remove all the segments defined by the specified value#.
571 /// Also remove the value# from value# list.
removeValNo(VNInfo * ValNo)572 void LiveRange::removeValNo(VNInfo *ValNo) {
573   if (empty()) return;
574   segments.erase(std::remove_if(begin(), end(), [ValNo](const Segment &S) {
575     return S.valno == ValNo;
576   }), end());
577   // Now that ValNo is dead, remove it.
578   markValNoForDeletion(ValNo);
579 }
580 
join(LiveRange & Other,const int * LHSValNoAssignments,const int * RHSValNoAssignments,SmallVectorImpl<VNInfo * > & NewVNInfo)581 void LiveRange::join(LiveRange &Other,
582                      const int *LHSValNoAssignments,
583                      const int *RHSValNoAssignments,
584                      SmallVectorImpl<VNInfo *> &NewVNInfo) {
585   verify();
586 
587   // Determine if any of our values are mapped.  This is uncommon, so we want
588   // to avoid the range scan if not.
589   bool MustMapCurValNos = false;
590   unsigned NumVals = getNumValNums();
591   unsigned NumNewVals = NewVNInfo.size();
592   for (unsigned i = 0; i != NumVals; ++i) {
593     unsigned LHSValID = LHSValNoAssignments[i];
594     if (i != LHSValID ||
595         (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
596       MustMapCurValNos = true;
597       break;
598     }
599   }
600 
601   // If we have to apply a mapping to our base range assignment, rewrite it now.
602   if (MustMapCurValNos && !empty()) {
603     // Map the first live range.
604 
605     iterator OutIt = begin();
606     OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
607     for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
608       VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
609       assert(nextValNo && "Huh?");
610 
611       // If this live range has the same value # as its immediate predecessor,
612       // and if they are neighbors, remove one Segment.  This happens when we
613       // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
614       if (OutIt->valno == nextValNo && OutIt->end == I->start) {
615         OutIt->end = I->end;
616       } else {
617         // Didn't merge. Move OutIt to the next segment,
618         ++OutIt;
619         OutIt->valno = nextValNo;
620         if (OutIt != I) {
621           OutIt->start = I->start;
622           OutIt->end = I->end;
623         }
624       }
625     }
626     // If we merge some segments, chop off the end.
627     ++OutIt;
628     segments.erase(OutIt, end());
629   }
630 
631   // Rewrite Other values before changing the VNInfo ids.
632   // This can leave Other in an invalid state because we're not coalescing
633   // touching segments that now have identical values. That's OK since Other is
634   // not supposed to be valid after calling join();
635   for (Segment &S : Other.segments)
636     S.valno = NewVNInfo[RHSValNoAssignments[S.valno->id]];
637 
638   // Update val# info. Renumber them and make sure they all belong to this
639   // LiveRange now. Also remove dead val#'s.
640   unsigned NumValNos = 0;
641   for (unsigned i = 0; i < NumNewVals; ++i) {
642     VNInfo *VNI = NewVNInfo[i];
643     if (VNI) {
644       if (NumValNos >= NumVals)
645         valnos.push_back(VNI);
646       else
647         valnos[NumValNos] = VNI;
648       VNI->id = NumValNos++;  // Renumber val#.
649     }
650   }
651   if (NumNewVals < NumVals)
652     valnos.resize(NumNewVals);  // shrinkify
653 
654   // Okay, now insert the RHS live segments into the LHS.
655   LiveRangeUpdater Updater(this);
656   for (Segment &S : Other.segments)
657     Updater.add(S);
658 }
659 
660 /// Merge all of the segments in RHS into this live range as the specified
661 /// value number.  The segments in RHS are allowed to overlap with segments in
662 /// the current range, but only if the overlapping segments have the
663 /// specified value number.
MergeSegmentsInAsValue(const LiveRange & RHS,VNInfo * LHSValNo)664 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
665                                        VNInfo *LHSValNo) {
666   LiveRangeUpdater Updater(this);
667   for (const Segment &S : RHS.segments)
668     Updater.add(S.start, S.end, LHSValNo);
669 }
670 
671 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
672 /// in RHS into this live range as the specified value number.
673 /// The segments in RHS are allowed to overlap with segments in the
674 /// current range, it will replace the value numbers of the overlaped
675 /// segments with the specified value number.
MergeValueInAsValue(const LiveRange & RHS,const VNInfo * RHSValNo,VNInfo * LHSValNo)676 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
677                                     const VNInfo *RHSValNo,
678                                     VNInfo *LHSValNo) {
679   LiveRangeUpdater Updater(this);
680   for (const Segment &S : RHS.segments)
681     if (S.valno == RHSValNo)
682       Updater.add(S.start, S.end, LHSValNo);
683 }
684 
685 /// MergeValueNumberInto - This method is called when two value nubmers
686 /// are found to be equivalent.  This eliminates V1, replacing all
687 /// segments with the V1 value number with the V2 value number.  This can
688 /// cause merging of V1/V2 values numbers and compaction of the value space.
MergeValueNumberInto(VNInfo * V1,VNInfo * V2)689 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
690   assert(V1 != V2 && "Identical value#'s are always equivalent!");
691 
692   // This code actually merges the (numerically) larger value number into the
693   // smaller value number, which is likely to allow us to compactify the value
694   // space.  The only thing we have to be careful of is to preserve the
695   // instruction that defines the result value.
696 
697   // Make sure V2 is smaller than V1.
698   if (V1->id < V2->id) {
699     V1->copyFrom(*V2);
700     std::swap(V1, V2);
701   }
702 
703   // Merge V1 segments into V2.
704   for (iterator I = begin(); I != end(); ) {
705     iterator S = I++;
706     if (S->valno != V1) continue;  // Not a V1 Segment.
707 
708     // Okay, we found a V1 live range.  If it had a previous, touching, V2 live
709     // range, extend it.
710     if (S != begin()) {
711       iterator Prev = S-1;
712       if (Prev->valno == V2 && Prev->end == S->start) {
713         Prev->end = S->end;
714 
715         // Erase this live-range.
716         segments.erase(S);
717         I = Prev+1;
718         S = Prev;
719       }
720     }
721 
722     // Okay, now we have a V1 or V2 live range that is maximally merged forward.
723     // Ensure that it is a V2 live-range.
724     S->valno = V2;
725 
726     // If we can merge it into later V2 segments, do so now.  We ignore any
727     // following V1 segments, as they will be merged in subsequent iterations
728     // of the loop.
729     if (I != end()) {
730       if (I->start == S->end && I->valno == V2) {
731         S->end = I->end;
732         segments.erase(I);
733         I = S+1;
734       }
735     }
736   }
737 
738   // Now that V1 is dead, remove it.
739   markValNoForDeletion(V1);
740 
741   return V2;
742 }
743 
flushSegmentSet()744 void LiveRange::flushSegmentSet() {
745   assert(segmentSet != nullptr && "segment set must have been created");
746   assert(
747       segments.empty() &&
748       "segment set can be used only initially before switching to the array");
749   segments.append(segmentSet->begin(), segmentSet->end());
750   segmentSet = nullptr;
751   verify();
752 }
753 
isLiveAtIndexes(ArrayRef<SlotIndex> Slots) const754 bool LiveRange::isLiveAtIndexes(ArrayRef<SlotIndex> Slots) const {
755   ArrayRef<SlotIndex>::iterator SlotI = Slots.begin();
756   ArrayRef<SlotIndex>::iterator SlotE = Slots.end();
757 
758   // If there are no regmask slots, we have nothing to search.
759   if (SlotI == SlotE)
760     return false;
761 
762   // Start our search at the first segment that ends after the first slot.
763   const_iterator SegmentI = find(*SlotI);
764   const_iterator SegmentE = end();
765 
766   // If there are no segments that end after the first slot, we're done.
767   if (SegmentI == SegmentE)
768     return false;
769 
770   // Look for each slot in the live range.
771   for ( ; SlotI != SlotE; ++SlotI) {
772     // Go to the next segment that ends after the current slot.
773     // The slot may be within a hole in the range.
774     SegmentI = advanceTo(SegmentI, *SlotI);
775     if (SegmentI == SegmentE)
776       return false;
777 
778     // If this segment contains the slot, we're done.
779     if (SegmentI->contains(*SlotI))
780       return true;
781     // Otherwise, look for the next slot.
782   }
783 
784   // We didn't find a segment containing any of the slots.
785   return false;
786 }
787 
freeSubRange(SubRange * S)788 void LiveInterval::freeSubRange(SubRange *S) {
789   S->~SubRange();
790   // Memory was allocated with BumpPtr allocator and is not freed here.
791 }
792 
removeEmptySubRanges()793 void LiveInterval::removeEmptySubRanges() {
794   SubRange **NextPtr = &SubRanges;
795   SubRange *I = *NextPtr;
796   while (I != nullptr) {
797     if (!I->empty()) {
798       NextPtr = &I->Next;
799       I = *NextPtr;
800       continue;
801     }
802     // Skip empty subranges until we find the first nonempty one.
803     do {
804       SubRange *Next = I->Next;
805       freeSubRange(I);
806       I = Next;
807     } while (I != nullptr && I->empty());
808     *NextPtr = I;
809   }
810 }
811 
clearSubRanges()812 void LiveInterval::clearSubRanges() {
813   for (SubRange *I = SubRanges, *Next; I != nullptr; I = Next) {
814     Next = I->Next;
815     freeSubRange(I);
816   }
817   SubRanges = nullptr;
818 }
819 
getSize() const820 unsigned LiveInterval::getSize() const {
821   unsigned Sum = 0;
822   for (const Segment &S : segments)
823     Sum += S.start.distance(S.end);
824   return Sum;
825 }
826 
operator <<(raw_ostream & os,const LiveRange::Segment & S)827 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
828   return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ')';
829 }
830 
831 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const832 LLVM_DUMP_METHOD void LiveRange::Segment::dump() const {
833   dbgs() << *this << '\n';
834 }
835 #endif
836 
print(raw_ostream & OS) const837 void LiveRange::print(raw_ostream &OS) const {
838   if (empty())
839     OS << "EMPTY";
840   else {
841     for (const Segment &S : segments) {
842       OS << S;
843       assert(S.valno == getValNumInfo(S.valno->id) && "Bad VNInfo");
844     }
845   }
846 
847   // Print value number info.
848   if (getNumValNums()) {
849     OS << "  ";
850     unsigned vnum = 0;
851     for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
852          ++i, ++vnum) {
853       const VNInfo *vni = *i;
854       if (vnum) OS << ' ';
855       OS << vnum << '@';
856       if (vni->isUnused()) {
857         OS << 'x';
858       } else {
859         OS << vni->def;
860         if (vni->isPHIDef())
861           OS << "-phi";
862       }
863     }
864   }
865 }
866 
print(raw_ostream & OS) const867 void LiveInterval::SubRange::print(raw_ostream &OS) const {
868   OS << " L" << PrintLaneMask(LaneMask) << ' '
869      << static_cast<const LiveRange&>(*this);
870 }
871 
print(raw_ostream & OS) const872 void LiveInterval::print(raw_ostream &OS) const {
873   OS << PrintReg(reg) << ' ';
874   super::print(OS);
875   // Print subranges
876   for (const SubRange &SR : subranges())
877     OS << SR;
878 }
879 
880 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const881 LLVM_DUMP_METHOD void LiveRange::dump() const {
882   dbgs() << *this << '\n';
883 }
884 
dump() const885 LLVM_DUMP_METHOD void LiveInterval::SubRange::dump() const {
886   dbgs() << *this << '\n';
887 }
888 
dump() const889 LLVM_DUMP_METHOD void LiveInterval::dump() const {
890   dbgs() << *this << '\n';
891 }
892 #endif
893 
894 #ifndef NDEBUG
verify() const895 void LiveRange::verify() const {
896   for (const_iterator I = begin(), E = end(); I != E; ++I) {
897     assert(I->start.isValid());
898     assert(I->end.isValid());
899     assert(I->start < I->end);
900     assert(I->valno != nullptr);
901     assert(I->valno->id < valnos.size());
902     assert(I->valno == valnos[I->valno->id]);
903     if (std::next(I) != E) {
904       assert(I->end <= std::next(I)->start);
905       if (I->end == std::next(I)->start)
906         assert(I->valno != std::next(I)->valno);
907     }
908   }
909 }
910 
verify(const MachineRegisterInfo * MRI) const911 void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
912   super::verify();
913 
914   // Make sure SubRanges are fine and LaneMasks are disjunct.
915   LaneBitmask Mask = 0;
916   LaneBitmask MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg) : ~0u;
917   for (const SubRange &SR : subranges()) {
918     // Subrange lanemask should be disjunct to any previous subrange masks.
919     assert((Mask & SR.LaneMask) == 0);
920     Mask |= SR.LaneMask;
921 
922     // subrange mask should not contained in maximum lane mask for the vreg.
923     assert((Mask & ~MaxMask) == 0);
924     // empty subranges must be removed.
925     assert(!SR.empty());
926 
927     SR.verify();
928     // Main liverange should cover subrange.
929     assert(covers(SR));
930   }
931 }
932 #endif
933 
934 
935 //===----------------------------------------------------------------------===//
936 //                           LiveRangeUpdater class
937 //===----------------------------------------------------------------------===//
938 //
939 // The LiveRangeUpdater class always maintains these invariants:
940 //
941 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
942 //   This is the initial state, and the state created by flush().
943 //   In this state, isDirty() returns false.
944 //
945 // Otherwise, segments are kept in three separate areas:
946 //
947 // 1. [begin; WriteI) at the front of LR.
948 // 2. [ReadI; end) at the back of LR.
949 // 3. Spills.
950 //
951 // - LR.begin() <= WriteI <= ReadI <= LR.end().
952 // - Segments in all three areas are fully ordered and coalesced.
953 // - Segments in area 1 precede and can't coalesce with segments in area 2.
954 // - Segments in Spills precede and can't coalesce with segments in area 2.
955 // - No coalescing is possible between segments in Spills and segments in area
956 //   1, and there are no overlapping segments.
957 //
958 // The segments in Spills are not ordered with respect to the segments in area
959 // 1. They need to be merged.
960 //
961 // When they exist, Spills.back().start <= LastStart,
962 //                 and WriteI[-1].start <= LastStart.
963 
print(raw_ostream & OS) const964 void LiveRangeUpdater::print(raw_ostream &OS) const {
965   if (!isDirty()) {
966     if (LR)
967       OS << "Clean updater: " << *LR << '\n';
968     else
969       OS << "Null updater.\n";
970     return;
971   }
972   assert(LR && "Can't have null LR in dirty updater.");
973   OS << " updater with gap = " << (ReadI - WriteI)
974      << ", last start = " << LastStart
975      << ":\n  Area 1:";
976   for (const auto &S : make_range(LR->begin(), WriteI))
977     OS << ' ' << S;
978   OS << "\n  Spills:";
979   for (unsigned I = 0, E = Spills.size(); I != E; ++I)
980     OS << ' ' << Spills[I];
981   OS << "\n  Area 2:";
982   for (const auto &S : make_range(ReadI, LR->end()))
983     OS << ' ' << S;
984   OS << '\n';
985 }
986 
dump() const987 LLVM_DUMP_METHOD void LiveRangeUpdater::dump() const {
988   print(errs());
989 }
990 
991 // Determine if A and B should be coalesced.
coalescable(const LiveRange::Segment & A,const LiveRange::Segment & B)992 static inline bool coalescable(const LiveRange::Segment &A,
993                                const LiveRange::Segment &B) {
994   assert(A.start <= B.start && "Unordered live segments.");
995   if (A.end == B.start)
996     return A.valno == B.valno;
997   if (A.end < B.start)
998     return false;
999   assert(A.valno == B.valno && "Cannot overlap different values");
1000   return true;
1001 }
1002 
add(LiveRange::Segment Seg)1003 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
1004   assert(LR && "Cannot add to a null destination");
1005 
1006   // Fall back to the regular add method if the live range
1007   // is using the segment set instead of the segment vector.
1008   if (LR->segmentSet != nullptr) {
1009     LR->addSegmentToSet(Seg);
1010     return;
1011   }
1012 
1013   // Flush the state if Start moves backwards.
1014   if (!LastStart.isValid() || LastStart > Seg.start) {
1015     if (isDirty())
1016       flush();
1017     // This brings us to an uninitialized state. Reinitialize.
1018     assert(Spills.empty() && "Leftover spilled segments");
1019     WriteI = ReadI = LR->begin();
1020   }
1021 
1022   // Remember start for next time.
1023   LastStart = Seg.start;
1024 
1025   // Advance ReadI until it ends after Seg.start.
1026   LiveRange::iterator E = LR->end();
1027   if (ReadI != E && ReadI->end <= Seg.start) {
1028     // First try to close the gap between WriteI and ReadI with spills.
1029     if (ReadI != WriteI)
1030       mergeSpills();
1031     // Then advance ReadI.
1032     if (ReadI == WriteI)
1033       ReadI = WriteI = LR->find(Seg.start);
1034     else
1035       while (ReadI != E && ReadI->end <= Seg.start)
1036         *WriteI++ = *ReadI++;
1037   }
1038 
1039   assert(ReadI == E || ReadI->end > Seg.start);
1040 
1041   // Check if the ReadI segment begins early.
1042   if (ReadI != E && ReadI->start <= Seg.start) {
1043     assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
1044     // Bail if Seg is completely contained in ReadI.
1045     if (ReadI->end >= Seg.end)
1046       return;
1047     // Coalesce into Seg.
1048     Seg.start = ReadI->start;
1049     ++ReadI;
1050   }
1051 
1052   // Coalesce as much as possible from ReadI into Seg.
1053   while (ReadI != E && coalescable(Seg, *ReadI)) {
1054     Seg.end = std::max(Seg.end, ReadI->end);
1055     ++ReadI;
1056   }
1057 
1058   // Try coalescing Spills.back() into Seg.
1059   if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
1060     Seg.start = Spills.back().start;
1061     Seg.end = std::max(Spills.back().end, Seg.end);
1062     Spills.pop_back();
1063   }
1064 
1065   // Try coalescing Seg into WriteI[-1].
1066   if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
1067     WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
1068     return;
1069   }
1070 
1071   // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
1072   if (WriteI != ReadI) {
1073     *WriteI++ = Seg;
1074     return;
1075   }
1076 
1077   // Finally, append to LR or Spills.
1078   if (WriteI == E) {
1079     LR->segments.push_back(Seg);
1080     WriteI = ReadI = LR->end();
1081   } else
1082     Spills.push_back(Seg);
1083 }
1084 
1085 // Merge as many spilled segments as possible into the gap between WriteI
1086 // and ReadI. Advance WriteI to reflect the inserted instructions.
mergeSpills()1087 void LiveRangeUpdater::mergeSpills() {
1088   // Perform a backwards merge of Spills and [SpillI;WriteI).
1089   size_t GapSize = ReadI - WriteI;
1090   size_t NumMoved = std::min(Spills.size(), GapSize);
1091   LiveRange::iterator Src = WriteI;
1092   LiveRange::iterator Dst = Src + NumMoved;
1093   LiveRange::iterator SpillSrc = Spills.end();
1094   LiveRange::iterator B = LR->begin();
1095 
1096   // This is the new WriteI position after merging spills.
1097   WriteI = Dst;
1098 
1099   // Now merge Src and Spills backwards.
1100   while (Src != Dst) {
1101     if (Src != B && Src[-1].start > SpillSrc[-1].start)
1102       *--Dst = *--Src;
1103     else
1104       *--Dst = *--SpillSrc;
1105   }
1106   assert(NumMoved == size_t(Spills.end() - SpillSrc));
1107   Spills.erase(SpillSrc, Spills.end());
1108 }
1109 
flush()1110 void LiveRangeUpdater::flush() {
1111   if (!isDirty())
1112     return;
1113   // Clear the dirty state.
1114   LastStart = SlotIndex();
1115 
1116   assert(LR && "Cannot add to a null destination");
1117 
1118   // Nothing to merge?
1119   if (Spills.empty()) {
1120     LR->segments.erase(WriteI, ReadI);
1121     LR->verify();
1122     return;
1123   }
1124 
1125   // Resize the WriteI - ReadI gap to match Spills.
1126   size_t GapSize = ReadI - WriteI;
1127   if (GapSize < Spills.size()) {
1128     // The gap is too small. Make some room.
1129     size_t WritePos = WriteI - LR->begin();
1130     LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
1131     // This also invalidated ReadI, but it is recomputed below.
1132     WriteI = LR->begin() + WritePos;
1133   } else {
1134     // Shrink the gap if necessary.
1135     LR->segments.erase(WriteI + Spills.size(), ReadI);
1136   }
1137   ReadI = WriteI + Spills.size();
1138   mergeSpills();
1139   LR->verify();
1140 }
1141 
Classify(const LiveRange & LR)1142 unsigned ConnectedVNInfoEqClasses::Classify(const LiveRange &LR) {
1143   // Create initial equivalence classes.
1144   EqClass.clear();
1145   EqClass.grow(LR.getNumValNums());
1146 
1147   const VNInfo *used = nullptr, *unused = nullptr;
1148 
1149   // Determine connections.
1150   for (const VNInfo *VNI : LR.valnos) {
1151     // Group all unused values into one class.
1152     if (VNI->isUnused()) {
1153       if (unused)
1154         EqClass.join(unused->id, VNI->id);
1155       unused = VNI;
1156       continue;
1157     }
1158     used = VNI;
1159     if (VNI->isPHIDef()) {
1160       const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
1161       assert(MBB && "Phi-def has no defining MBB");
1162       // Connect to values live out of predecessors.
1163       for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
1164            PE = MBB->pred_end(); PI != PE; ++PI)
1165         if (const VNInfo *PVNI = LR.getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
1166           EqClass.join(VNI->id, PVNI->id);
1167     } else {
1168       // Normal value defined by an instruction. Check for two-addr redef.
1169       // FIXME: This could be coincidental. Should we really check for a tied
1170       // operand constraint?
1171       // Note that VNI->def may be a use slot for an early clobber def.
1172       if (const VNInfo *UVNI = LR.getVNInfoBefore(VNI->def))
1173         EqClass.join(VNI->id, UVNI->id);
1174     }
1175   }
1176 
1177   // Lump all the unused values in with the last used value.
1178   if (used && unused)
1179     EqClass.join(used->id, unused->id);
1180 
1181   EqClass.compress();
1182   return EqClass.getNumClasses();
1183 }
1184 
Distribute(LiveInterval & LI,LiveInterval * LIV[],MachineRegisterInfo & MRI)1185 void ConnectedVNInfoEqClasses::Distribute(LiveInterval &LI, LiveInterval *LIV[],
1186                                           MachineRegisterInfo &MRI) {
1187   // Rewrite instructions.
1188   for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
1189        RE = MRI.reg_end(); RI != RE;) {
1190     MachineOperand &MO = *RI;
1191     MachineInstr *MI = RI->getParent();
1192     ++RI;
1193     // DBG_VALUE instructions don't have slot indexes, so get the index of the
1194     // instruction before them.
1195     // Normally, DBG_VALUE instructions are removed before this function is
1196     // called, but it is not a requirement.
1197     SlotIndex Idx;
1198     if (MI->isDebugValue())
1199       Idx = LIS.getSlotIndexes()->getIndexBefore(*MI);
1200     else
1201       Idx = LIS.getInstructionIndex(*MI);
1202     LiveQueryResult LRQ = LI.Query(Idx);
1203     const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
1204     // In the case of an <undef> use that isn't tied to any def, VNI will be
1205     // NULL. If the use is tied to a def, VNI will be the defined value.
1206     if (!VNI)
1207       continue;
1208     if (unsigned EqClass = getEqClass(VNI))
1209       MO.setReg(LIV[EqClass-1]->reg);
1210   }
1211 
1212   // Distribute subregister liveranges.
1213   if (LI.hasSubRanges()) {
1214     unsigned NumComponents = EqClass.getNumClasses();
1215     SmallVector<unsigned, 8> VNIMapping;
1216     SmallVector<LiveInterval::SubRange*, 8> SubRanges;
1217     BumpPtrAllocator &Allocator = LIS.getVNInfoAllocator();
1218     for (LiveInterval::SubRange &SR : LI.subranges()) {
1219       // Create new subranges in the split intervals and construct a mapping
1220       // for the VNInfos in the subrange.
1221       unsigned NumValNos = SR.valnos.size();
1222       VNIMapping.clear();
1223       VNIMapping.reserve(NumValNos);
1224       SubRanges.clear();
1225       SubRanges.resize(NumComponents-1, nullptr);
1226       for (unsigned I = 0; I < NumValNos; ++I) {
1227         const VNInfo &VNI = *SR.valnos[I];
1228         unsigned ComponentNum;
1229         if (VNI.isUnused()) {
1230           ComponentNum = 0;
1231         } else {
1232           const VNInfo *MainRangeVNI = LI.getVNInfoAt(VNI.def);
1233           assert(MainRangeVNI != nullptr
1234                  && "SubRange def must have corresponding main range def");
1235           ComponentNum = getEqClass(MainRangeVNI);
1236           if (ComponentNum > 0 && SubRanges[ComponentNum-1] == nullptr) {
1237             SubRanges[ComponentNum-1]
1238               = LIV[ComponentNum-1]->createSubRange(Allocator, SR.LaneMask);
1239           }
1240         }
1241         VNIMapping.push_back(ComponentNum);
1242       }
1243       DistributeRange(SR, SubRanges.data(), VNIMapping);
1244     }
1245     LI.removeEmptySubRanges();
1246   }
1247 
1248   // Distribute main liverange.
1249   DistributeRange(LI, LIV, EqClass);
1250 }
1251