1 //===- LiveInterval.cpp - Live Interval Representation --------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the LiveRange and LiveInterval classes.  Given some
10 // numbering of each the machine instructions an interval [i, j) is said to be a
11 // live range for register v if there is no instruction with number j' >= j
12 // such that v is live at j' and there is no instruction with number i' < i such
13 // that v is live at i'. In this implementation ranges can have holes,
14 // i.e. a range might look like [1,20), [50,65), [1000,1001).  Each
15 // individual segment is represented as an instance of LiveRange::Segment,
16 // and the whole range is represented as an instance of LiveRange.
17 //
18 //===----------------------------------------------------------------------===//
19 
20 #include "llvm/CodeGen/LiveInterval.h"
21 #include "LiveRangeUtils.h"
22 #include "RegisterCoalescer.h"
23 #include "llvm/ADT/ArrayRef.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/ADT/SmallPtrSet.h"
26 #include "llvm/ADT/SmallVector.h"
27 #include "llvm/ADT/iterator_range.h"
28 #include "llvm/CodeGen/LiveIntervals.h"
29 #include "llvm/CodeGen/MachineBasicBlock.h"
30 #include "llvm/CodeGen/MachineInstr.h"
31 #include "llvm/CodeGen/MachineOperand.h"
32 #include "llvm/CodeGen/MachineRegisterInfo.h"
33 #include "llvm/CodeGen/SlotIndexes.h"
34 #include "llvm/CodeGen/TargetRegisterInfo.h"
35 #include "llvm/Config/llvm-config.h"
36 #include "llvm/MC/LaneBitmask.h"
37 #include "llvm/Support/Compiler.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/raw_ostream.h"
40 #include <algorithm>
41 #include <cassert>
42 #include <cstddef>
43 #include <iterator>
44 #include <utility>
45 
46 using namespace llvm;
47 
48 namespace {
49 
50 //===----------------------------------------------------------------------===//
51 // Implementation of various methods necessary for calculation of live ranges.
52 // The implementation of the methods abstracts from the concrete type of the
53 // segment collection.
54 //
55 // Implementation of the class follows the Template design pattern. The base
56 // class contains generic algorithms that call collection-specific methods,
57 // which are provided in concrete subclasses. In order to avoid virtual calls
58 // these methods are provided by means of C++ template instantiation.
59 // The base class calls the methods of the subclass through method impl(),
60 // which casts 'this' pointer to the type of the subclass.
61 //
62 //===----------------------------------------------------------------------===//
63 
64 template <typename ImplT, typename IteratorT, typename CollectionT>
65 class CalcLiveRangeUtilBase {
66 protected:
67   LiveRange *LR;
68 
69 protected:
CalcLiveRangeUtilBase(LiveRange * LR)70   CalcLiveRangeUtilBase(LiveRange *LR) : LR(LR) {}
71 
72 public:
73   using Segment = LiveRange::Segment;
74   using iterator = IteratorT;
75 
76   /// A counterpart of LiveRange::createDeadDef: Make sure the range has a
77   /// value defined at @p Def.
78   /// If @p ForVNI is null, and there is no value defined at @p Def, a new
79   /// value will be allocated using @p VNInfoAllocator.
80   /// If @p ForVNI is null, the return value is the value defined at @p Def,
81   /// either a pre-existing one, or the one newly created.
82   /// If @p ForVNI is not null, then @p Def should be the location where
83   /// @p ForVNI is defined. If the range does not have a value defined at
84   /// @p Def, the value @p ForVNI will be used instead of allocating a new
85   /// one. If the range already has a value defined at @p Def, it must be
86   /// same as @p ForVNI. In either case, @p ForVNI will be the return value.
createDeadDef(SlotIndex Def,VNInfo::Allocator * VNInfoAllocator,VNInfo * ForVNI)87   VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator *VNInfoAllocator,
88                         VNInfo *ForVNI) {
89     assert(!Def.isDead() && "Cannot define a value at the dead slot");
90     assert((!ForVNI || ForVNI->def == Def) &&
91            "If ForVNI is specified, it must match Def");
92     iterator I = impl().find(Def);
93     if (I == segments().end()) {
94       VNInfo *VNI = ForVNI ? ForVNI : LR->getNextValue(Def, *VNInfoAllocator);
95       impl().insertAtEnd(Segment(Def, Def.getDeadSlot(), VNI));
96       return VNI;
97     }
98 
99     Segment *S = segmentAt(I);
100     if (SlotIndex::isSameInstr(Def, S->start)) {
101       assert((!ForVNI || ForVNI == S->valno) && "Value number mismatch");
102       assert(S->valno->def == S->start && "Inconsistent existing value def");
103 
104       // It is possible to have both normal and early-clobber defs of the same
105       // register on an instruction. It doesn't make a lot of sense, but it is
106       // possible to specify in inline assembly.
107       //
108       // Just convert everything to early-clobber.
109       Def = std::min(Def, S->start);
110       if (Def != S->start)
111         S->start = S->valno->def = Def;
112       return S->valno;
113     }
114     assert(SlotIndex::isEarlierInstr(Def, S->start) && "Already live at def");
115     VNInfo *VNI = ForVNI ? ForVNI : LR->getNextValue(Def, *VNInfoAllocator);
116     segments().insert(I, Segment(Def, Def.getDeadSlot(), VNI));
117     return VNI;
118   }
119 
extendInBlock(SlotIndex StartIdx,SlotIndex Use)120   VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Use) {
121     if (segments().empty())
122       return nullptr;
123     iterator I =
124       impl().findInsertPos(Segment(Use.getPrevSlot(), Use, nullptr));
125     if (I == segments().begin())
126       return nullptr;
127     --I;
128     if (I->end <= StartIdx)
129       return nullptr;
130     if (I->end < Use)
131       extendSegmentEndTo(I, Use);
132     return I->valno;
133   }
134 
extendInBlock(ArrayRef<SlotIndex> Undefs,SlotIndex StartIdx,SlotIndex Use)135   std::pair<VNInfo*,bool> extendInBlock(ArrayRef<SlotIndex> Undefs,
136       SlotIndex StartIdx, SlotIndex Use) {
137     if (segments().empty())
138       return std::make_pair(nullptr, false);
139     SlotIndex BeforeUse = Use.getPrevSlot();
140     iterator I = impl().findInsertPos(Segment(BeforeUse, Use, nullptr));
141     if (I == segments().begin())
142       return std::make_pair(nullptr, LR->isUndefIn(Undefs, StartIdx, BeforeUse));
143     --I;
144     if (I->end <= StartIdx)
145       return std::make_pair(nullptr, LR->isUndefIn(Undefs, StartIdx, BeforeUse));
146     if (I->end < Use) {
147       if (LR->isUndefIn(Undefs, I->end, BeforeUse))
148         return std::make_pair(nullptr, true);
149       extendSegmentEndTo(I, Use);
150     }
151     return std::make_pair(I->valno, false);
152   }
153 
154   /// This method is used when we want to extend the segment specified
155   /// by I to end at the specified endpoint. To do this, we should
156   /// merge and eliminate all segments that this will overlap
157   /// with. The iterator is not invalidated.
extendSegmentEndTo(iterator I,SlotIndex NewEnd)158   void extendSegmentEndTo(iterator I, SlotIndex NewEnd) {
159     assert(I != segments().end() && "Not a valid segment!");
160     Segment *S = segmentAt(I);
161     VNInfo *ValNo = I->valno;
162 
163     // Search for the first segment that we can't merge with.
164     iterator MergeTo = std::next(I);
165     for (; MergeTo != segments().end() && NewEnd >= MergeTo->end; ++MergeTo)
166       assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
167 
168     // If NewEnd was in the middle of a segment, make sure to get its endpoint.
169     S->end = std::max(NewEnd, std::prev(MergeTo)->end);
170 
171     // If the newly formed segment now touches the segment after it and if they
172     // have the same value number, merge the two segments into one segment.
173     if (MergeTo != segments().end() && MergeTo->start <= I->end &&
174         MergeTo->valno == ValNo) {
175       S->end = MergeTo->end;
176       ++MergeTo;
177     }
178 
179     // Erase any dead segments.
180     segments().erase(std::next(I), MergeTo);
181   }
182 
183   /// This method is used when we want to extend the segment specified
184   /// by I to start at the specified endpoint.  To do this, we should
185   /// merge and eliminate all segments that this will overlap with.
extendSegmentStartTo(iterator I,SlotIndex NewStart)186   iterator extendSegmentStartTo(iterator I, SlotIndex NewStart) {
187     assert(I != segments().end() && "Not a valid segment!");
188     Segment *S = segmentAt(I);
189     VNInfo *ValNo = I->valno;
190 
191     // Search for the first segment that we can't merge with.
192     iterator MergeTo = I;
193     do {
194       if (MergeTo == segments().begin()) {
195         S->start = NewStart;
196         segments().erase(MergeTo, I);
197         return I;
198       }
199       assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
200       --MergeTo;
201     } while (NewStart <= MergeTo->start);
202 
203     // If we start in the middle of another segment, just delete a range and
204     // extend that segment.
205     if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
206       segmentAt(MergeTo)->end = S->end;
207     } else {
208       // Otherwise, extend the segment right after.
209       ++MergeTo;
210       Segment *MergeToSeg = segmentAt(MergeTo);
211       MergeToSeg->start = NewStart;
212       MergeToSeg->end = S->end;
213     }
214 
215     segments().erase(std::next(MergeTo), std::next(I));
216     return MergeTo;
217   }
218 
addSegment(Segment S)219   iterator addSegment(Segment S) {
220     SlotIndex Start = S.start, End = S.end;
221     iterator I = impl().findInsertPos(S);
222 
223     // If the inserted segment starts in the middle or right at the end of
224     // another segment, just extend that segment to contain the segment of S.
225     if (I != segments().begin()) {
226       iterator B = std::prev(I);
227       if (S.valno == B->valno) {
228         if (B->start <= Start && B->end >= Start) {
229           extendSegmentEndTo(B, End);
230           return B;
231         }
232       } else {
233         // Check to make sure that we are not overlapping two live segments with
234         // different valno's.
235         assert(B->end <= Start &&
236                "Cannot overlap two segments with differing ValID's"
237                " (did you def the same reg twice in a MachineInstr?)");
238       }
239     }
240 
241     // Otherwise, if this segment ends in the middle of, or right next
242     // to, another segment, merge it into that segment.
243     if (I != segments().end()) {
244       if (S.valno == I->valno) {
245         if (I->start <= End) {
246           I = extendSegmentStartTo(I, Start);
247 
248           // If S is a complete superset of a segment, we may need to grow its
249           // endpoint as well.
250           if (End > I->end)
251             extendSegmentEndTo(I, End);
252           return I;
253         }
254       } else {
255         // Check to make sure that we are not overlapping two live segments with
256         // different valno's.
257         assert(I->start >= End &&
258                "Cannot overlap two segments with differing ValID's");
259       }
260     }
261 
262     // Otherwise, this is just a new segment that doesn't interact with
263     // anything.
264     // Insert it.
265     return segments().insert(I, S);
266   }
267 
268 private:
impl()269   ImplT &impl() { return *static_cast<ImplT *>(this); }
270 
segments()271   CollectionT &segments() { return impl().segmentsColl(); }
272 
segmentAt(iterator I)273   Segment *segmentAt(iterator I) { return const_cast<Segment *>(&(*I)); }
274 };
275 
276 //===----------------------------------------------------------------------===//
277 //   Instantiation of the methods for calculation of live ranges
278 //   based on a segment vector.
279 //===----------------------------------------------------------------------===//
280 
281 class CalcLiveRangeUtilVector;
282 using CalcLiveRangeUtilVectorBase =
283     CalcLiveRangeUtilBase<CalcLiveRangeUtilVector, LiveRange::iterator,
284                           LiveRange::Segments>;
285 
286 class CalcLiveRangeUtilVector : public CalcLiveRangeUtilVectorBase {
287 public:
CalcLiveRangeUtilVector(LiveRange * LR)288   CalcLiveRangeUtilVector(LiveRange *LR) : CalcLiveRangeUtilVectorBase(LR) {}
289 
290 private:
291   friend CalcLiveRangeUtilVectorBase;
292 
segmentsColl()293   LiveRange::Segments &segmentsColl() { return LR->segments; }
294 
insertAtEnd(const Segment & S)295   void insertAtEnd(const Segment &S) { LR->segments.push_back(S); }
296 
find(SlotIndex Pos)297   iterator find(SlotIndex Pos) { return LR->find(Pos); }
298 
findInsertPos(Segment S)299   iterator findInsertPos(Segment S) { return llvm::upper_bound(*LR, S.start); }
300 };
301 
302 //===----------------------------------------------------------------------===//
303 //   Instantiation of the methods for calculation of live ranges
304 //   based on a segment set.
305 //===----------------------------------------------------------------------===//
306 
307 class CalcLiveRangeUtilSet;
308 using CalcLiveRangeUtilSetBase =
309     CalcLiveRangeUtilBase<CalcLiveRangeUtilSet, LiveRange::SegmentSet::iterator,
310                           LiveRange::SegmentSet>;
311 
312 class CalcLiveRangeUtilSet : public CalcLiveRangeUtilSetBase {
313 public:
CalcLiveRangeUtilSet(LiveRange * LR)314   CalcLiveRangeUtilSet(LiveRange *LR) : CalcLiveRangeUtilSetBase(LR) {}
315 
316 private:
317   friend CalcLiveRangeUtilSetBase;
318 
segmentsColl()319   LiveRange::SegmentSet &segmentsColl() { return *LR->segmentSet; }
320 
insertAtEnd(const Segment & S)321   void insertAtEnd(const Segment &S) {
322     LR->segmentSet->insert(LR->segmentSet->end(), S);
323   }
324 
find(SlotIndex Pos)325   iterator find(SlotIndex Pos) {
326     iterator I =
327         LR->segmentSet->upper_bound(Segment(Pos, Pos.getNextSlot(), nullptr));
328     if (I == LR->segmentSet->begin())
329       return I;
330     iterator PrevI = std::prev(I);
331     if (Pos < (*PrevI).end)
332       return PrevI;
333     return I;
334   }
335 
findInsertPos(Segment S)336   iterator findInsertPos(Segment S) {
337     iterator I = LR->segmentSet->upper_bound(S);
338     if (I != LR->segmentSet->end() && !(S.start < *I))
339       ++I;
340     return I;
341   }
342 };
343 
344 } // end anonymous namespace
345 
346 //===----------------------------------------------------------------------===//
347 //   LiveRange methods
348 //===----------------------------------------------------------------------===//
349 
find(SlotIndex Pos)350 LiveRange::iterator LiveRange::find(SlotIndex Pos) {
351   return llvm::partition_point(*this,
352                                [&](const Segment &X) { return X.end <= Pos; });
353 }
354 
createDeadDef(SlotIndex Def,VNInfo::Allocator & VNIAlloc)355 VNInfo *LiveRange::createDeadDef(SlotIndex Def, VNInfo::Allocator &VNIAlloc) {
356   // Use the segment set, if it is available.
357   if (segmentSet != nullptr)
358     return CalcLiveRangeUtilSet(this).createDeadDef(Def, &VNIAlloc, nullptr);
359   // Otherwise use the segment vector.
360   return CalcLiveRangeUtilVector(this).createDeadDef(Def, &VNIAlloc, nullptr);
361 }
362 
createDeadDef(VNInfo * VNI)363 VNInfo *LiveRange::createDeadDef(VNInfo *VNI) {
364   // Use the segment set, if it is available.
365   if (segmentSet != nullptr)
366     return CalcLiveRangeUtilSet(this).createDeadDef(VNI->def, nullptr, VNI);
367   // Otherwise use the segment vector.
368   return CalcLiveRangeUtilVector(this).createDeadDef(VNI->def, nullptr, VNI);
369 }
370 
371 // overlaps - Return true if the intersection of the two live ranges is
372 // not empty.
373 //
374 // An example for overlaps():
375 //
376 // 0: A = ...
377 // 4: B = ...
378 // 8: C = A + B ;; last use of A
379 //
380 // The live ranges should look like:
381 //
382 // A = [3, 11)
383 // B = [7, x)
384 // C = [11, y)
385 //
386 // A->overlaps(C) should return false since we want to be able to join
387 // A and C.
388 //
overlapsFrom(const LiveRange & other,const_iterator StartPos) const389 bool LiveRange::overlapsFrom(const LiveRange& other,
390                              const_iterator StartPos) const {
391   assert(!empty() && "empty range");
392   const_iterator i = begin();
393   const_iterator ie = end();
394   const_iterator j = StartPos;
395   const_iterator je = other.end();
396 
397   assert((StartPos->start <= i->start || StartPos == other.begin()) &&
398          StartPos != other.end() && "Bogus start position hint!");
399 
400   if (i->start < j->start) {
401     i = std::upper_bound(i, ie, j->start);
402     if (i != begin()) --i;
403   } else if (j->start < i->start) {
404     ++StartPos;
405     if (StartPos != other.end() && StartPos->start <= i->start) {
406       assert(StartPos < other.end() && i < end());
407       j = std::upper_bound(j, je, i->start);
408       if (j != other.begin()) --j;
409     }
410   } else {
411     return true;
412   }
413 
414   if (j == je) return false;
415 
416   while (i != ie) {
417     if (i->start > j->start) {
418       std::swap(i, j);
419       std::swap(ie, je);
420     }
421 
422     if (i->end > j->start)
423       return true;
424     ++i;
425   }
426 
427   return false;
428 }
429 
overlaps(const LiveRange & Other,const CoalescerPair & CP,const SlotIndexes & Indexes) const430 bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
431                          const SlotIndexes &Indexes) const {
432   assert(!empty() && "empty range");
433   if (Other.empty())
434     return false;
435 
436   // Use binary searches to find initial positions.
437   const_iterator I = find(Other.beginIndex());
438   const_iterator IE = end();
439   if (I == IE)
440     return false;
441   const_iterator J = Other.find(I->start);
442   const_iterator JE = Other.end();
443   if (J == JE)
444     return false;
445 
446   while (true) {
447     // J has just been advanced to satisfy:
448     assert(J->end >= I->start);
449     // Check for an overlap.
450     if (J->start < I->end) {
451       // I and J are overlapping. Find the later start.
452       SlotIndex Def = std::max(I->start, J->start);
453       // Allow the overlap if Def is a coalescable copy.
454       if (Def.isBlock() ||
455           !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
456         return true;
457     }
458     // Advance the iterator that ends first to check for more overlaps.
459     if (J->end > I->end) {
460       std::swap(I, J);
461       std::swap(IE, JE);
462     }
463     // Advance J until J->end >= I->start.
464     do
465       if (++J == JE)
466         return false;
467     while (J->end < I->start);
468   }
469 }
470 
471 /// overlaps - Return true if the live range overlaps an interval specified
472 /// by [Start, End).
overlaps(SlotIndex Start,SlotIndex End) const473 bool LiveRange::overlaps(SlotIndex Start, SlotIndex End) const {
474   assert(Start < End && "Invalid range");
475   const_iterator I = lower_bound(*this, End);
476   return I != begin() && (--I)->end > Start;
477 }
478 
covers(const LiveRange & Other) const479 bool LiveRange::covers(const LiveRange &Other) const {
480   if (empty())
481     return Other.empty();
482 
483   const_iterator I = begin();
484   for (const Segment &O : Other.segments) {
485     I = advanceTo(I, O.start);
486     if (I == end() || I->start > O.start)
487       return false;
488 
489     // Check adjacent live segments and see if we can get behind O.end.
490     while (I->end < O.end) {
491       const_iterator Last = I;
492       // Get next segment and abort if it was not adjacent.
493       ++I;
494       if (I == end() || Last->end != I->start)
495         return false;
496     }
497   }
498   return true;
499 }
500 
501 /// ValNo is dead, remove it.  If it is the largest value number, just nuke it
502 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
503 /// it can be nuked later.
markValNoForDeletion(VNInfo * ValNo)504 void LiveRange::markValNoForDeletion(VNInfo *ValNo) {
505   if (ValNo->id == getNumValNums()-1) {
506     do {
507       valnos.pop_back();
508     } while (!valnos.empty() && valnos.back()->isUnused());
509   } else {
510     ValNo->markUnused();
511   }
512 }
513 
514 /// RenumberValues - Renumber all values in order of appearance and delete the
515 /// remaining unused values.
RenumberValues()516 void LiveRange::RenumberValues() {
517   SmallPtrSet<VNInfo*, 8> Seen;
518   valnos.clear();
519   for (const Segment &S : segments) {
520     VNInfo *VNI = S.valno;
521     if (!Seen.insert(VNI).second)
522       continue;
523     assert(!VNI->isUnused() && "Unused valno used by live segment");
524     VNI->id = (unsigned)valnos.size();
525     valnos.push_back(VNI);
526   }
527 }
528 
addSegmentToSet(Segment S)529 void LiveRange::addSegmentToSet(Segment S) {
530   CalcLiveRangeUtilSet(this).addSegment(S);
531 }
532 
addSegment(Segment S)533 LiveRange::iterator LiveRange::addSegment(Segment S) {
534   // Use the segment set, if it is available.
535   if (segmentSet != nullptr) {
536     addSegmentToSet(S);
537     return end();
538   }
539   // Otherwise use the segment vector.
540   return CalcLiveRangeUtilVector(this).addSegment(S);
541 }
542 
append(const Segment S)543 void LiveRange::append(const Segment S) {
544   // Check that the segment belongs to the back of the list.
545   assert(segments.empty() || segments.back().end <= S.start);
546   segments.push_back(S);
547 }
548 
extendInBlock(ArrayRef<SlotIndex> Undefs,SlotIndex StartIdx,SlotIndex Kill)549 std::pair<VNInfo*,bool> LiveRange::extendInBlock(ArrayRef<SlotIndex> Undefs,
550     SlotIndex StartIdx, SlotIndex Kill) {
551   // Use the segment set, if it is available.
552   if (segmentSet != nullptr)
553     return CalcLiveRangeUtilSet(this).extendInBlock(Undefs, StartIdx, Kill);
554   // Otherwise use the segment vector.
555   return CalcLiveRangeUtilVector(this).extendInBlock(Undefs, StartIdx, Kill);
556 }
557 
extendInBlock(SlotIndex StartIdx,SlotIndex Kill)558 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
559   // Use the segment set, if it is available.
560   if (segmentSet != nullptr)
561     return CalcLiveRangeUtilSet(this).extendInBlock(StartIdx, Kill);
562   // Otherwise use the segment vector.
563   return CalcLiveRangeUtilVector(this).extendInBlock(StartIdx, Kill);
564 }
565 
566 /// Remove the specified segment from this range.  Note that the segment must
567 /// be in a single Segment in its entirety.
removeSegment(SlotIndex Start,SlotIndex End,bool RemoveDeadValNo)568 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
569                               bool RemoveDeadValNo) {
570   // Find the Segment containing this span.
571   iterator I = find(Start);
572   assert(I != end() && "Segment is not in range!");
573   assert(I->containsInterval(Start, End)
574          && "Segment is not entirely in range!");
575 
576   // If the span we are removing is at the start of the Segment, adjust it.
577   VNInfo *ValNo = I->valno;
578   if (I->start == Start) {
579     if (I->end == End) {
580       segments.erase(I);  // Removed the whole Segment.
581 
582       if (RemoveDeadValNo)
583         removeValNoIfDead(ValNo);
584     } else
585       I->start = End;
586     return;
587   }
588 
589   // Otherwise if the span we are removing is at the end of the Segment,
590   // adjust the other way.
591   if (I->end == End) {
592     I->end = Start;
593     return;
594   }
595 
596   // Otherwise, we are splitting the Segment into two pieces.
597   SlotIndex OldEnd = I->end;
598   I->end = Start;   // Trim the old segment.
599 
600   // Insert the new one.
601   segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
602 }
603 
removeSegment(iterator I,bool RemoveDeadValNo)604 LiveRange::iterator LiveRange::removeSegment(iterator I, bool RemoveDeadValNo) {
605   VNInfo *ValNo = I->valno;
606   I = segments.erase(I);
607   if (RemoveDeadValNo)
608     removeValNoIfDead(ValNo);
609   return I;
610 }
611 
removeValNoIfDead(VNInfo * ValNo)612 void LiveRange::removeValNoIfDead(VNInfo *ValNo) {
613   if (none_of(*this, [=](const Segment &S) { return S.valno == ValNo; }))
614     markValNoForDeletion(ValNo);
615 }
616 
617 /// removeValNo - Remove all the segments defined by the specified value#.
618 /// Also remove the value# from value# list.
removeValNo(VNInfo * ValNo)619 void LiveRange::removeValNo(VNInfo *ValNo) {
620   if (empty()) return;
621   llvm::erase_if(segments,
622                  [ValNo](const Segment &S) { return S.valno == ValNo; });
623   // Now that ValNo is dead, remove it.
624   markValNoForDeletion(ValNo);
625 }
626 
join(LiveRange & Other,const int * LHSValNoAssignments,const int * RHSValNoAssignments,SmallVectorImpl<VNInfo * > & NewVNInfo)627 void LiveRange::join(LiveRange &Other,
628                      const int *LHSValNoAssignments,
629                      const int *RHSValNoAssignments,
630                      SmallVectorImpl<VNInfo *> &NewVNInfo) {
631   verify();
632 
633   // Determine if any of our values are mapped.  This is uncommon, so we want
634   // to avoid the range scan if not.
635   bool MustMapCurValNos = false;
636   unsigned NumVals = getNumValNums();
637   unsigned NumNewVals = NewVNInfo.size();
638   for (unsigned i = 0; i != NumVals; ++i) {
639     unsigned LHSValID = LHSValNoAssignments[i];
640     if (i != LHSValID ||
641         (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
642       MustMapCurValNos = true;
643       break;
644     }
645   }
646 
647   // If we have to apply a mapping to our base range assignment, rewrite it now.
648   if (MustMapCurValNos && !empty()) {
649     // Map the first live range.
650 
651     iterator OutIt = begin();
652     OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
653     for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
654       VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
655       assert(nextValNo && "Huh?");
656 
657       // If this live range has the same value # as its immediate predecessor,
658       // and if they are neighbors, remove one Segment.  This happens when we
659       // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
660       if (OutIt->valno == nextValNo && OutIt->end == I->start) {
661         OutIt->end = I->end;
662       } else {
663         // Didn't merge. Move OutIt to the next segment,
664         ++OutIt;
665         OutIt->valno = nextValNo;
666         if (OutIt != I) {
667           OutIt->start = I->start;
668           OutIt->end = I->end;
669         }
670       }
671     }
672     // If we merge some segments, chop off the end.
673     ++OutIt;
674     segments.erase(OutIt, end());
675   }
676 
677   // Rewrite Other values before changing the VNInfo ids.
678   // This can leave Other in an invalid state because we're not coalescing
679   // touching segments that now have identical values. That's OK since Other is
680   // not supposed to be valid after calling join();
681   for (Segment &S : Other.segments)
682     S.valno = NewVNInfo[RHSValNoAssignments[S.valno->id]];
683 
684   // Update val# info. Renumber them and make sure they all belong to this
685   // LiveRange now. Also remove dead val#'s.
686   unsigned NumValNos = 0;
687   for (unsigned i = 0; i < NumNewVals; ++i) {
688     VNInfo *VNI = NewVNInfo[i];
689     if (VNI) {
690       if (NumValNos >= NumVals)
691         valnos.push_back(VNI);
692       else
693         valnos[NumValNos] = VNI;
694       VNI->id = NumValNos++;  // Renumber val#.
695     }
696   }
697   if (NumNewVals < NumVals)
698     valnos.resize(NumNewVals);  // shrinkify
699 
700   // Okay, now insert the RHS live segments into the LHS.
701   LiveRangeUpdater Updater(this);
702   for (Segment &S : Other.segments)
703     Updater.add(S);
704 }
705 
706 /// Merge all of the segments in RHS into this live range as the specified
707 /// value number.  The segments in RHS are allowed to overlap with segments in
708 /// the current range, but only if the overlapping segments have the
709 /// specified value number.
MergeSegmentsInAsValue(const LiveRange & RHS,VNInfo * LHSValNo)710 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
711                                        VNInfo *LHSValNo) {
712   LiveRangeUpdater Updater(this);
713   for (const Segment &S : RHS.segments)
714     Updater.add(S.start, S.end, LHSValNo);
715 }
716 
717 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
718 /// in RHS into this live range as the specified value number.
719 /// The segments in RHS are allowed to overlap with segments in the
720 /// current range, it will replace the value numbers of the overlaped
721 /// segments with the specified value number.
MergeValueInAsValue(const LiveRange & RHS,const VNInfo * RHSValNo,VNInfo * LHSValNo)722 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
723                                     const VNInfo *RHSValNo,
724                                     VNInfo *LHSValNo) {
725   LiveRangeUpdater Updater(this);
726   for (const Segment &S : RHS.segments)
727     if (S.valno == RHSValNo)
728       Updater.add(S.start, S.end, LHSValNo);
729 }
730 
731 /// MergeValueNumberInto - This method is called when two value nubmers
732 /// are found to be equivalent.  This eliminates V1, replacing all
733 /// segments with the V1 value number with the V2 value number.  This can
734 /// cause merging of V1/V2 values numbers and compaction of the value space.
MergeValueNumberInto(VNInfo * V1,VNInfo * V2)735 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
736   assert(V1 != V2 && "Identical value#'s are always equivalent!");
737 
738   // This code actually merges the (numerically) larger value number into the
739   // smaller value number, which is likely to allow us to compactify the value
740   // space.  The only thing we have to be careful of is to preserve the
741   // instruction that defines the result value.
742 
743   // Make sure V2 is smaller than V1.
744   if (V1->id < V2->id) {
745     V1->copyFrom(*V2);
746     std::swap(V1, V2);
747   }
748 
749   // Merge V1 segments into V2.
750   for (iterator I = begin(); I != end(); ) {
751     iterator S = I++;
752     if (S->valno != V1) continue;  // Not a V1 Segment.
753 
754     // Okay, we found a V1 live range.  If it had a previous, touching, V2 live
755     // range, extend it.
756     if (S != begin()) {
757       iterator Prev = S-1;
758       if (Prev->valno == V2 && Prev->end == S->start) {
759         Prev->end = S->end;
760 
761         // Erase this live-range.
762         segments.erase(S);
763         I = Prev+1;
764         S = Prev;
765       }
766     }
767 
768     // Okay, now we have a V1 or V2 live range that is maximally merged forward.
769     // Ensure that it is a V2 live-range.
770     S->valno = V2;
771 
772     // If we can merge it into later V2 segments, do so now.  We ignore any
773     // following V1 segments, as they will be merged in subsequent iterations
774     // of the loop.
775     if (I != end()) {
776       if (I->start == S->end && I->valno == V2) {
777         S->end = I->end;
778         segments.erase(I);
779         I = S+1;
780       }
781     }
782   }
783 
784   // Now that V1 is dead, remove it.
785   markValNoForDeletion(V1);
786 
787   return V2;
788 }
789 
flushSegmentSet()790 void LiveRange::flushSegmentSet() {
791   assert(segmentSet != nullptr && "segment set must have been created");
792   assert(
793       segments.empty() &&
794       "segment set can be used only initially before switching to the array");
795   segments.append(segmentSet->begin(), segmentSet->end());
796   segmentSet = nullptr;
797   verify();
798 }
799 
isLiveAtIndexes(ArrayRef<SlotIndex> Slots) const800 bool LiveRange::isLiveAtIndexes(ArrayRef<SlotIndex> Slots) const {
801   ArrayRef<SlotIndex>::iterator SlotI = Slots.begin();
802   ArrayRef<SlotIndex>::iterator SlotE = Slots.end();
803 
804   // If there are no regmask slots, we have nothing to search.
805   if (SlotI == SlotE)
806     return false;
807 
808   // Start our search at the first segment that ends after the first slot.
809   const_iterator SegmentI = find(*SlotI);
810   const_iterator SegmentE = end();
811 
812   // If there are no segments that end after the first slot, we're done.
813   if (SegmentI == SegmentE)
814     return false;
815 
816   // Look for each slot in the live range.
817   for ( ; SlotI != SlotE; ++SlotI) {
818     // Go to the next segment that ends after the current slot.
819     // The slot may be within a hole in the range.
820     SegmentI = advanceTo(SegmentI, *SlotI);
821     if (SegmentI == SegmentE)
822       return false;
823 
824     // If this segment contains the slot, we're done.
825     if (SegmentI->contains(*SlotI))
826       return true;
827     // Otherwise, look for the next slot.
828   }
829 
830   // We didn't find a segment containing any of the slots.
831   return false;
832 }
833 
freeSubRange(SubRange * S)834 void LiveInterval::freeSubRange(SubRange *S) {
835   S->~SubRange();
836   // Memory was allocated with BumpPtr allocator and is not freed here.
837 }
838 
removeEmptySubRanges()839 void LiveInterval::removeEmptySubRanges() {
840   SubRange **NextPtr = &SubRanges;
841   SubRange *I = *NextPtr;
842   while (I != nullptr) {
843     if (!I->empty()) {
844       NextPtr = &I->Next;
845       I = *NextPtr;
846       continue;
847     }
848     // Skip empty subranges until we find the first nonempty one.
849     do {
850       SubRange *Next = I->Next;
851       freeSubRange(I);
852       I = Next;
853     } while (I != nullptr && I->empty());
854     *NextPtr = I;
855   }
856 }
857 
clearSubRanges()858 void LiveInterval::clearSubRanges() {
859   for (SubRange *I = SubRanges, *Next; I != nullptr; I = Next) {
860     Next = I->Next;
861     freeSubRange(I);
862   }
863   SubRanges = nullptr;
864 }
865 
866 /// For each VNI in \p SR, check whether or not that value defines part
867 /// of the mask describe by \p LaneMask and if not, remove that value
868 /// from \p SR.
stripValuesNotDefiningMask(unsigned Reg,LiveInterval::SubRange & SR,LaneBitmask LaneMask,const SlotIndexes & Indexes,const TargetRegisterInfo & TRI,unsigned ComposeSubRegIdx)869 static void stripValuesNotDefiningMask(unsigned Reg, LiveInterval::SubRange &SR,
870                                        LaneBitmask LaneMask,
871                                        const SlotIndexes &Indexes,
872                                        const TargetRegisterInfo &TRI,
873                                        unsigned ComposeSubRegIdx) {
874   // Phys reg should not be tracked at subreg level.
875   // Same for noreg (Reg == 0).
876   if (!Register::isVirtualRegister(Reg) || !Reg)
877     return;
878   // Remove the values that don't define those lanes.
879   SmallVector<VNInfo *, 8> ToBeRemoved;
880   for (VNInfo *VNI : SR.valnos) {
881     if (VNI->isUnused())
882       continue;
883     // PHI definitions don't have MI attached, so there is nothing
884     // we can use to strip the VNI.
885     if (VNI->isPHIDef())
886       continue;
887     const MachineInstr *MI = Indexes.getInstructionFromIndex(VNI->def);
888     assert(MI && "Cannot find the definition of a value");
889     bool hasDef = false;
890     for (ConstMIBundleOperands MOI(*MI); MOI.isValid(); ++MOI) {
891       if (!MOI->isReg() || !MOI->isDef())
892         continue;
893       if (MOI->getReg() != Reg)
894         continue;
895       LaneBitmask OrigMask = TRI.getSubRegIndexLaneMask(MOI->getSubReg());
896       LaneBitmask ExpectedDefMask =
897           ComposeSubRegIdx
898               ? TRI.composeSubRegIndexLaneMask(ComposeSubRegIdx, OrigMask)
899               : OrigMask;
900       if ((ExpectedDefMask & LaneMask).none())
901         continue;
902       hasDef = true;
903       break;
904     }
905 
906     if (!hasDef)
907       ToBeRemoved.push_back(VNI);
908   }
909   for (VNInfo *VNI : ToBeRemoved)
910     SR.removeValNo(VNI);
911 
912   // If the subrange is empty at this point, the MIR is invalid. Do not assert
913   // and let the verifier catch this case.
914 }
915 
refineSubRanges(BumpPtrAllocator & Allocator,LaneBitmask LaneMask,std::function<void (LiveInterval::SubRange &)> Apply,const SlotIndexes & Indexes,const TargetRegisterInfo & TRI,unsigned ComposeSubRegIdx)916 void LiveInterval::refineSubRanges(
917     BumpPtrAllocator &Allocator, LaneBitmask LaneMask,
918     std::function<void(LiveInterval::SubRange &)> Apply,
919     const SlotIndexes &Indexes, const TargetRegisterInfo &TRI,
920     unsigned ComposeSubRegIdx) {
921   LaneBitmask ToApply = LaneMask;
922   for (SubRange &SR : subranges()) {
923     LaneBitmask SRMask = SR.LaneMask;
924     LaneBitmask Matching = SRMask & LaneMask;
925     if (Matching.none())
926       continue;
927 
928     SubRange *MatchingRange;
929     if (SRMask == Matching) {
930       // The subrange fits (it does not cover bits outside \p LaneMask).
931       MatchingRange = &SR;
932     } else {
933       // We have to split the subrange into a matching and non-matching part.
934       // Reduce lanemask of existing lane to non-matching part.
935       SR.LaneMask = SRMask & ~Matching;
936       // Create a new subrange for the matching part
937       MatchingRange = createSubRangeFrom(Allocator, Matching, SR);
938       // Now that the subrange is split in half, make sure we
939       // only keep in the subranges the VNIs that touch the related half.
940       stripValuesNotDefiningMask(reg(), *MatchingRange, Matching, Indexes, TRI,
941                                  ComposeSubRegIdx);
942       stripValuesNotDefiningMask(reg(), SR, SR.LaneMask, Indexes, TRI,
943                                  ComposeSubRegIdx);
944     }
945     Apply(*MatchingRange);
946     ToApply &= ~Matching;
947   }
948   // Create a new subrange if there are uncovered bits left.
949   if (ToApply.any()) {
950     SubRange *NewRange = createSubRange(Allocator, ToApply);
951     Apply(*NewRange);
952   }
953 }
954 
getSize() const955 unsigned LiveInterval::getSize() const {
956   unsigned Sum = 0;
957   for (const Segment &S : segments)
958     Sum += S.start.distance(S.end);
959   return Sum;
960 }
961 
computeSubRangeUndefs(SmallVectorImpl<SlotIndex> & Undefs,LaneBitmask LaneMask,const MachineRegisterInfo & MRI,const SlotIndexes & Indexes) const962 void LiveInterval::computeSubRangeUndefs(SmallVectorImpl<SlotIndex> &Undefs,
963                                          LaneBitmask LaneMask,
964                                          const MachineRegisterInfo &MRI,
965                                          const SlotIndexes &Indexes) const {
966   assert(reg().isVirtual());
967   LaneBitmask VRegMask = MRI.getMaxLaneMaskForVReg(reg());
968   assert((VRegMask & LaneMask).any());
969   const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
970   for (const MachineOperand &MO : MRI.def_operands(reg())) {
971     if (!MO.isUndef())
972       continue;
973     unsigned SubReg = MO.getSubReg();
974     assert(SubReg != 0 && "Undef should only be set on subreg defs");
975     LaneBitmask DefMask = TRI.getSubRegIndexLaneMask(SubReg);
976     LaneBitmask UndefMask = VRegMask & ~DefMask;
977     if ((UndefMask & LaneMask).any()) {
978       const MachineInstr &MI = *MO.getParent();
979       bool EarlyClobber = MO.isEarlyClobber();
980       SlotIndex Pos = Indexes.getInstructionIndex(MI).getRegSlot(EarlyClobber);
981       Undefs.push_back(Pos);
982     }
983   }
984 }
985 
operator <<(raw_ostream & OS,const LiveRange::Segment & S)986 raw_ostream& llvm::operator<<(raw_ostream& OS, const LiveRange::Segment &S) {
987   return OS << '[' << S.start << ',' << S.end << ':' << S.valno->id << ')';
988 }
989 
990 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const991 LLVM_DUMP_METHOD void LiveRange::Segment::dump() const {
992   dbgs() << *this << '\n';
993 }
994 #endif
995 
print(raw_ostream & OS) const996 void LiveRange::print(raw_ostream &OS) const {
997   if (empty())
998     OS << "EMPTY";
999   else {
1000     for (const Segment &S : segments) {
1001       OS << S;
1002       assert(S.valno == getValNumInfo(S.valno->id) && "Bad VNInfo");
1003     }
1004   }
1005 
1006   // Print value number info.
1007   if (getNumValNums()) {
1008     OS << ' ';
1009     unsigned vnum = 0;
1010     for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
1011          ++i, ++vnum) {
1012       const VNInfo *vni = *i;
1013       if (vnum) OS << ' ';
1014       OS << vnum << '@';
1015       if (vni->isUnused()) {
1016         OS << 'x';
1017       } else {
1018         OS << vni->def;
1019         if (vni->isPHIDef())
1020           OS << "-phi";
1021       }
1022     }
1023   }
1024 }
1025 
print(raw_ostream & OS) const1026 void LiveInterval::SubRange::print(raw_ostream &OS) const {
1027   OS << "  L" << PrintLaneMask(LaneMask) << ' '
1028      << static_cast<const LiveRange &>(*this);
1029 }
1030 
print(raw_ostream & OS) const1031 void LiveInterval::print(raw_ostream &OS) const {
1032   OS << printReg(reg()) << ' ';
1033   super::print(OS);
1034   // Print subranges
1035   for (const SubRange &SR : subranges())
1036     OS << SR;
1037   OS << "  weight:" << Weight;
1038 }
1039 
1040 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const1041 LLVM_DUMP_METHOD void LiveRange::dump() const {
1042   dbgs() << *this << '\n';
1043 }
1044 
dump() const1045 LLVM_DUMP_METHOD void LiveInterval::SubRange::dump() const {
1046   dbgs() << *this << '\n';
1047 }
1048 
dump() const1049 LLVM_DUMP_METHOD void LiveInterval::dump() const {
1050   dbgs() << *this << '\n';
1051 }
1052 #endif
1053 
1054 #ifndef NDEBUG
verify() const1055 void LiveRange::verify() const {
1056   for (const_iterator I = begin(), E = end(); I != E; ++I) {
1057     assert(I->start.isValid());
1058     assert(I->end.isValid());
1059     assert(I->start < I->end);
1060     assert(I->valno != nullptr);
1061     assert(I->valno->id < valnos.size());
1062     assert(I->valno == valnos[I->valno->id]);
1063     if (std::next(I) != E) {
1064       assert(I->end <= std::next(I)->start);
1065       if (I->end == std::next(I)->start)
1066         assert(I->valno != std::next(I)->valno);
1067     }
1068   }
1069 }
1070 
verify(const MachineRegisterInfo * MRI) const1071 void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
1072   super::verify();
1073 
1074   // Make sure SubRanges are fine and LaneMasks are disjunct.
1075   LaneBitmask Mask;
1076   LaneBitmask MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg())
1077                                        : LaneBitmask::getAll();
1078   for (const SubRange &SR : subranges()) {
1079     // Subrange lanemask should be disjunct to any previous subrange masks.
1080     assert((Mask & SR.LaneMask).none());
1081     Mask |= SR.LaneMask;
1082 
1083     // subrange mask should not contained in maximum lane mask for the vreg.
1084     assert((Mask & ~MaxMask).none());
1085     // empty subranges must be removed.
1086     assert(!SR.empty());
1087 
1088     SR.verify();
1089     // Main liverange should cover subrange.
1090     assert(covers(SR));
1091   }
1092 }
1093 #endif
1094 
1095 //===----------------------------------------------------------------------===//
1096 //                           LiveRangeUpdater class
1097 //===----------------------------------------------------------------------===//
1098 //
1099 // The LiveRangeUpdater class always maintains these invariants:
1100 //
1101 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
1102 //   This is the initial state, and the state created by flush().
1103 //   In this state, isDirty() returns false.
1104 //
1105 // Otherwise, segments are kept in three separate areas:
1106 //
1107 // 1. [begin; WriteI) at the front of LR.
1108 // 2. [ReadI; end) at the back of LR.
1109 // 3. Spills.
1110 //
1111 // - LR.begin() <= WriteI <= ReadI <= LR.end().
1112 // - Segments in all three areas are fully ordered and coalesced.
1113 // - Segments in area 1 precede and can't coalesce with segments in area 2.
1114 // - Segments in Spills precede and can't coalesce with segments in area 2.
1115 // - No coalescing is possible between segments in Spills and segments in area
1116 //   1, and there are no overlapping segments.
1117 //
1118 // The segments in Spills are not ordered with respect to the segments in area
1119 // 1. They need to be merged.
1120 //
1121 // When they exist, Spills.back().start <= LastStart,
1122 //                 and WriteI[-1].start <= LastStart.
1123 
1124 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
print(raw_ostream & OS) const1125 void LiveRangeUpdater::print(raw_ostream &OS) const {
1126   if (!isDirty()) {
1127     if (LR)
1128       OS << "Clean updater: " << *LR << '\n';
1129     else
1130       OS << "Null updater.\n";
1131     return;
1132   }
1133   assert(LR && "Can't have null LR in dirty updater.");
1134   OS << " updater with gap = " << (ReadI - WriteI)
1135      << ", last start = " << LastStart
1136      << ":\n  Area 1:";
1137   for (const auto &S : make_range(LR->begin(), WriteI))
1138     OS << ' ' << S;
1139   OS << "\n  Spills:";
1140   for (unsigned I = 0, E = Spills.size(); I != E; ++I)
1141     OS << ' ' << Spills[I];
1142   OS << "\n  Area 2:";
1143   for (const auto &S : make_range(ReadI, LR->end()))
1144     OS << ' ' << S;
1145   OS << '\n';
1146 }
1147 
dump() const1148 LLVM_DUMP_METHOD void LiveRangeUpdater::dump() const {
1149   print(errs());
1150 }
1151 #endif
1152 
1153 // Determine if A and B should be coalesced.
coalescable(const LiveRange::Segment & A,const LiveRange::Segment & B)1154 static inline bool coalescable(const LiveRange::Segment &A,
1155                                const LiveRange::Segment &B) {
1156   assert(A.start <= B.start && "Unordered live segments.");
1157   if (A.end == B.start)
1158     return A.valno == B.valno;
1159   if (A.end < B.start)
1160     return false;
1161   assert(A.valno == B.valno && "Cannot overlap different values");
1162   return true;
1163 }
1164 
add(LiveRange::Segment Seg)1165 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
1166   assert(LR && "Cannot add to a null destination");
1167 
1168   // Fall back to the regular add method if the live range
1169   // is using the segment set instead of the segment vector.
1170   if (LR->segmentSet != nullptr) {
1171     LR->addSegmentToSet(Seg);
1172     return;
1173   }
1174 
1175   // Flush the state if Start moves backwards.
1176   if (!LastStart.isValid() || LastStart > Seg.start) {
1177     if (isDirty())
1178       flush();
1179     // This brings us to an uninitialized state. Reinitialize.
1180     assert(Spills.empty() && "Leftover spilled segments");
1181     WriteI = ReadI = LR->begin();
1182   }
1183 
1184   // Remember start for next time.
1185   LastStart = Seg.start;
1186 
1187   // Advance ReadI until it ends after Seg.start.
1188   LiveRange::iterator E = LR->end();
1189   if (ReadI != E && ReadI->end <= Seg.start) {
1190     // First try to close the gap between WriteI and ReadI with spills.
1191     if (ReadI != WriteI)
1192       mergeSpills();
1193     // Then advance ReadI.
1194     if (ReadI == WriteI)
1195       ReadI = WriteI = LR->find(Seg.start);
1196     else
1197       while (ReadI != E && ReadI->end <= Seg.start)
1198         *WriteI++ = *ReadI++;
1199   }
1200 
1201   assert(ReadI == E || ReadI->end > Seg.start);
1202 
1203   // Check if the ReadI segment begins early.
1204   if (ReadI != E && ReadI->start <= Seg.start) {
1205     assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
1206     // Bail if Seg is completely contained in ReadI.
1207     if (ReadI->end >= Seg.end)
1208       return;
1209     // Coalesce into Seg.
1210     Seg.start = ReadI->start;
1211     ++ReadI;
1212   }
1213 
1214   // Coalesce as much as possible from ReadI into Seg.
1215   while (ReadI != E && coalescable(Seg, *ReadI)) {
1216     Seg.end = std::max(Seg.end, ReadI->end);
1217     ++ReadI;
1218   }
1219 
1220   // Try coalescing Spills.back() into Seg.
1221   if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
1222     Seg.start = Spills.back().start;
1223     Seg.end = std::max(Spills.back().end, Seg.end);
1224     Spills.pop_back();
1225   }
1226 
1227   // Try coalescing Seg into WriteI[-1].
1228   if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
1229     WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
1230     return;
1231   }
1232 
1233   // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
1234   if (WriteI != ReadI) {
1235     *WriteI++ = Seg;
1236     return;
1237   }
1238 
1239   // Finally, append to LR or Spills.
1240   if (WriteI == E) {
1241     LR->segments.push_back(Seg);
1242     WriteI = ReadI = LR->end();
1243   } else
1244     Spills.push_back(Seg);
1245 }
1246 
1247 // Merge as many spilled segments as possible into the gap between WriteI
1248 // and ReadI. Advance WriteI to reflect the inserted instructions.
mergeSpills()1249 void LiveRangeUpdater::mergeSpills() {
1250   // Perform a backwards merge of Spills and [SpillI;WriteI).
1251   size_t GapSize = ReadI - WriteI;
1252   size_t NumMoved = std::min(Spills.size(), GapSize);
1253   LiveRange::iterator Src = WriteI;
1254   LiveRange::iterator Dst = Src + NumMoved;
1255   LiveRange::iterator SpillSrc = Spills.end();
1256   LiveRange::iterator B = LR->begin();
1257 
1258   // This is the new WriteI position after merging spills.
1259   WriteI = Dst;
1260 
1261   // Now merge Src and Spills backwards.
1262   while (Src != Dst) {
1263     if (Src != B && Src[-1].start > SpillSrc[-1].start)
1264       *--Dst = *--Src;
1265     else
1266       *--Dst = *--SpillSrc;
1267   }
1268   assert(NumMoved == size_t(Spills.end() - SpillSrc));
1269   Spills.erase(SpillSrc, Spills.end());
1270 }
1271 
flush()1272 void LiveRangeUpdater::flush() {
1273   if (!isDirty())
1274     return;
1275   // Clear the dirty state.
1276   LastStart = SlotIndex();
1277 
1278   assert(LR && "Cannot add to a null destination");
1279 
1280   // Nothing to merge?
1281   if (Spills.empty()) {
1282     LR->segments.erase(WriteI, ReadI);
1283     LR->verify();
1284     return;
1285   }
1286 
1287   // Resize the WriteI - ReadI gap to match Spills.
1288   size_t GapSize = ReadI - WriteI;
1289   if (GapSize < Spills.size()) {
1290     // The gap is too small. Make some room.
1291     size_t WritePos = WriteI - LR->begin();
1292     LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
1293     // This also invalidated ReadI, but it is recomputed below.
1294     WriteI = LR->begin() + WritePos;
1295   } else {
1296     // Shrink the gap if necessary.
1297     LR->segments.erase(WriteI + Spills.size(), ReadI);
1298   }
1299   ReadI = WriteI + Spills.size();
1300   mergeSpills();
1301   LR->verify();
1302 }
1303 
Classify(const LiveRange & LR)1304 unsigned ConnectedVNInfoEqClasses::Classify(const LiveRange &LR) {
1305   // Create initial equivalence classes.
1306   EqClass.clear();
1307   EqClass.grow(LR.getNumValNums());
1308 
1309   const VNInfo *used = nullptr, *unused = nullptr;
1310 
1311   // Determine connections.
1312   for (const VNInfo *VNI : LR.valnos) {
1313     // Group all unused values into one class.
1314     if (VNI->isUnused()) {
1315       if (unused)
1316         EqClass.join(unused->id, VNI->id);
1317       unused = VNI;
1318       continue;
1319     }
1320     used = VNI;
1321     if (VNI->isPHIDef()) {
1322       const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
1323       assert(MBB && "Phi-def has no defining MBB");
1324       // Connect to values live out of predecessors.
1325       for (MachineBasicBlock *Pred : MBB->predecessors())
1326         if (const VNInfo *PVNI = LR.getVNInfoBefore(LIS.getMBBEndIdx(Pred)))
1327           EqClass.join(VNI->id, PVNI->id);
1328     } else {
1329       // Normal value defined by an instruction. Check for two-addr redef.
1330       // FIXME: This could be coincidental. Should we really check for a tied
1331       // operand constraint?
1332       // Note that VNI->def may be a use slot for an early clobber def.
1333       if (const VNInfo *UVNI = LR.getVNInfoBefore(VNI->def))
1334         EqClass.join(VNI->id, UVNI->id);
1335     }
1336   }
1337 
1338   // Lump all the unused values in with the last used value.
1339   if (used && unused)
1340     EqClass.join(used->id, unused->id);
1341 
1342   EqClass.compress();
1343   return EqClass.getNumClasses();
1344 }
1345 
Distribute(LiveInterval & LI,LiveInterval * LIV[],MachineRegisterInfo & MRI)1346 void ConnectedVNInfoEqClasses::Distribute(LiveInterval &LI, LiveInterval *LIV[],
1347                                           MachineRegisterInfo &MRI) {
1348   // Rewrite instructions.
1349   for (MachineOperand &MO :
1350        llvm::make_early_inc_range(MRI.reg_operands(LI.reg()))) {
1351     MachineInstr *MI = MO.getParent();
1352     const VNInfo *VNI;
1353     if (MI->isDebugValue()) {
1354       // DBG_VALUE instructions don't have slot indexes, so get the index of
1355       // the instruction before them. The value is defined there too.
1356       SlotIndex Idx = LIS.getSlotIndexes()->getIndexBefore(*MI);
1357       VNI = LI.Query(Idx).valueOut();
1358     } else {
1359       SlotIndex Idx = LIS.getInstructionIndex(*MI);
1360       LiveQueryResult LRQ = LI.Query(Idx);
1361       VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
1362     }
1363     // In the case of an <undef> use that isn't tied to any def, VNI will be
1364     // NULL. If the use is tied to a def, VNI will be the defined value.
1365     if (!VNI)
1366       continue;
1367     if (unsigned EqClass = getEqClass(VNI))
1368       MO.setReg(LIV[EqClass - 1]->reg());
1369   }
1370 
1371   // Distribute subregister liveranges.
1372   if (LI.hasSubRanges()) {
1373     unsigned NumComponents = EqClass.getNumClasses();
1374     SmallVector<unsigned, 8> VNIMapping;
1375     SmallVector<LiveInterval::SubRange*, 8> SubRanges;
1376     BumpPtrAllocator &Allocator = LIS.getVNInfoAllocator();
1377     for (LiveInterval::SubRange &SR : LI.subranges()) {
1378       // Create new subranges in the split intervals and construct a mapping
1379       // for the VNInfos in the subrange.
1380       unsigned NumValNos = SR.valnos.size();
1381       VNIMapping.clear();
1382       VNIMapping.reserve(NumValNos);
1383       SubRanges.clear();
1384       SubRanges.resize(NumComponents-1, nullptr);
1385       for (unsigned I = 0; I < NumValNos; ++I) {
1386         const VNInfo &VNI = *SR.valnos[I];
1387         unsigned ComponentNum;
1388         if (VNI.isUnused()) {
1389           ComponentNum = 0;
1390         } else {
1391           const VNInfo *MainRangeVNI = LI.getVNInfoAt(VNI.def);
1392           assert(MainRangeVNI != nullptr
1393                  && "SubRange def must have corresponding main range def");
1394           ComponentNum = getEqClass(MainRangeVNI);
1395           if (ComponentNum > 0 && SubRanges[ComponentNum-1] == nullptr) {
1396             SubRanges[ComponentNum-1]
1397               = LIV[ComponentNum-1]->createSubRange(Allocator, SR.LaneMask);
1398           }
1399         }
1400         VNIMapping.push_back(ComponentNum);
1401       }
1402       DistributeRange(SR, SubRanges.data(), VNIMapping);
1403     }
1404     LI.removeEmptySubRanges();
1405   }
1406 
1407   // Distribute main liverange.
1408   DistributeRange(LI, LIV, EqClass);
1409 }
1410