1 //===-- LiveInterval.cpp - Live Interval Representation -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
19 //===----------------------------------------------------------------------===//
21 #include "llvm/CodeGen/LiveInterval.h"
22 #include "RegisterCoalescer.h"
23 #include "llvm/ADT/DenseMap.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/ADT/SmallSet.h"
26 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
27 #include "llvm/CodeGen/MachineRegisterInfo.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/Format.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include "llvm/Target/TargetRegisterInfo.h"
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.
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.
48 //===----------------------------------------------------------------------===//
50 template <typename ImplT, typename IteratorT, typename CollectionT>
51 class CalcLiveRangeUtilBase {
56 CalcLiveRangeUtilBase(LiveRange *LR) : LR(LR) {}
59 typedef LiveRange::Segment Segment;
60 typedef IteratorT iterator;
62 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator) {
63 assert(!Def.isDead() && "Cannot define a value at the dead slot");
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));
72 Segment *S = segmentAt(I);
73 if (SlotIndex::isSameInstr(Def, S->start)) {
74 assert(S->valno->def == S->start && "Inconsistent existing value def");
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.
80 // Just convert everything to early-clobber.
81 Def = std::min(Def, S->start);
83 S->start = S->valno->def = Def;
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));
92 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Use) {
93 if (segments().empty())
96 impl().findInsertPos(Segment(Use.getPrevSlot(), Use, nullptr));
97 if (I == segments().begin())
100 if (I->end <= StartIdx)
103 extendSegmentEndTo(I, Use);
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.
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;
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!");
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);
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;
132 // Erase any dead segments.
133 segments().erase(std::next(I), MergeTo);
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.
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;
144 // Search for the first segment that we can't merge with.
145 iterator MergeTo = I;
147 if (MergeTo == segments().begin()) {
149 segments().erase(MergeTo, I);
152 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
154 } while (NewStart <= MergeTo->start);
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;
161 // Otherwise, extend the segment right after.
163 Segment *MergeToSeg = segmentAt(MergeTo);
164 MergeToSeg->start = NewStart;
165 MergeToSeg->end = S->end;
168 segments().erase(std::next(MergeTo), std::next(I));
172 iterator addSegment(Segment S) {
173 SlotIndex Start = S.start, End = S.end;
174 iterator I = impl().findInsertPos(S);
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);
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?)");
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);
201 // If S is a complete superset of a segment, we may need to grow its
204 extendSegmentEndTo(I, End);
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");
215 // Otherwise, this is just a new segment that doesn't interact with
218 return segments().insert(I, S);
222 ImplT &impl() { return *static_cast<ImplT *>(this); }
224 CollectionT &segments() { return impl().segmentsColl(); }
226 Segment *segmentAt(iterator I) { return const_cast<Segment *>(&(*I)); }
229 //===----------------------------------------------------------------------===//
230 // Instantiation of the methods for calculation of live ranges
231 // based on a segment vector.
232 //===----------------------------------------------------------------------===//
234 class CalcLiveRangeUtilVector;
235 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilVector, LiveRange::iterator,
236 LiveRange::Segments> CalcLiveRangeUtilVectorBase;
238 class CalcLiveRangeUtilVector : public CalcLiveRangeUtilVectorBase {
240 CalcLiveRangeUtilVector(LiveRange *LR) : CalcLiveRangeUtilVectorBase(LR) {}
243 friend CalcLiveRangeUtilVectorBase;
245 LiveRange::Segments &segmentsColl() { return LR->segments; }
247 void insertAtEnd(const Segment &S) { LR->segments.push_back(S); }
249 iterator find(SlotIndex Pos) { return LR->find(Pos); }
251 iterator findInsertPos(Segment S) {
252 return std::upper_bound(LR->begin(), LR->end(), S.start);
256 //===----------------------------------------------------------------------===//
257 // Instantiation of the methods for calculation of live ranges
258 // based on a segment set.
259 //===----------------------------------------------------------------------===//
261 class CalcLiveRangeUtilSet;
262 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilSet,
263 LiveRange::SegmentSet::iterator,
264 LiveRange::SegmentSet> CalcLiveRangeUtilSetBase;
266 class CalcLiveRangeUtilSet : public CalcLiveRangeUtilSetBase {
268 CalcLiveRangeUtilSet(LiveRange *LR) : CalcLiveRangeUtilSetBase(LR) {}
271 friend CalcLiveRangeUtilSetBase;
273 LiveRange::SegmentSet &segmentsColl() { return *LR->segmentSet; }
275 void insertAtEnd(const Segment &S) {
276 LR->segmentSet->insert(LR->segmentSet->end(), S);
279 iterator find(SlotIndex Pos) {
281 LR->segmentSet->upper_bound(Segment(Pos, Pos.getNextSlot(), nullptr));
282 if (I == LR->segmentSet->begin())
284 iterator PrevI = std::prev(I);
285 if (Pos < (*PrevI).end)
290 iterator findInsertPos(Segment S) {
291 iterator I = LR->segmentSet->upper_bound(S);
292 if (I != LR->segmentSet->end() && !(S.start < *I))
299 //===----------------------------------------------------------------------===//
301 //===----------------------------------------------------------------------===//
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())
309 iterator I = begin();
312 size_t Mid = Len >> 1;
313 if (Pos < I[Mid].end)
316 I += Mid + 1, Len -= Mid + 1;
321 VNInfo *LiveRange::createDeadDef(SlotIndex Def,
322 VNInfo::Allocator &VNInfoAllocator) {
323 // Use the segment set, if it is available.
324 if (segmentSet != nullptr)
325 return CalcLiveRangeUtilSet(this).createDeadDef(Def, VNInfoAllocator);
326 // Otherwise use the segment vector.
327 return CalcLiveRangeUtilVector(this).createDeadDef(Def, VNInfoAllocator);
330 // overlaps - Return true if the intersection of the two live ranges is
333 // An example for overlaps():
337 // 8: C = A + B ;; last use of A
339 // The live ranges should look like:
345 // A->overlaps(C) should return false since we want to be able to join
348 bool LiveRange::overlapsFrom(const LiveRange& other,
349 const_iterator StartPos) const {
350 assert(!empty() && "empty range");
351 const_iterator i = begin();
352 const_iterator ie = end();
353 const_iterator j = StartPos;
354 const_iterator je = other.end();
356 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
357 StartPos != other.end() && "Bogus start position hint!");
359 if (i->start < j->start) {
360 i = std::upper_bound(i, ie, j->start);
361 if (i != begin()) --i;
362 } else if (j->start < i->start) {
364 if (StartPos != other.end() && StartPos->start <= i->start) {
365 assert(StartPos < other.end() && i < end());
366 j = std::upper_bound(j, je, i->start);
367 if (j != other.begin()) --j;
373 if (j == je) return false;
376 if (i->start > j->start) {
381 if (i->end > j->start)
389 bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
390 const SlotIndexes &Indexes) const {
391 assert(!empty() && "empty range");
395 // Use binary searches to find initial positions.
396 const_iterator I = find(Other.beginIndex());
397 const_iterator IE = end();
400 const_iterator J = Other.find(I->start);
401 const_iterator JE = Other.end();
406 // J has just been advanced to satisfy:
407 assert(J->end >= I->start);
408 // Check for an overlap.
409 if (J->start < I->end) {
410 // I and J are overlapping. Find the later start.
411 SlotIndex Def = std::max(I->start, J->start);
412 // Allow the overlap if Def is a coalescable copy.
414 !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
417 // Advance the iterator that ends first to check for more overlaps.
418 if (J->end > I->end) {
422 // Advance J until J->end >= I->start.
426 while (J->end < I->start);
430 /// overlaps - Return true if the live range overlaps an interval specified
432 bool LiveRange::overlaps(SlotIndex Start, SlotIndex End) const {
433 assert(Start < End && "Invalid range");
434 const_iterator I = std::lower_bound(begin(), end(), End);
435 return I != begin() && (--I)->end > Start;
438 bool LiveRange::covers(const LiveRange &Other) const {
440 return Other.empty();
442 const_iterator I = begin();
443 for (const Segment &O : Other.segments) {
444 I = advanceTo(I, O.start);
445 if (I == end() || I->start > O.start)
448 // Check adjacent live segments and see if we can get behind O.end.
449 while (I->end < O.end) {
450 const_iterator Last = I;
451 // Get next segment and abort if it was not adjacent.
453 if (I == end() || Last->end != I->start)
460 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
461 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
462 /// it can be nuked later.
463 void LiveRange::markValNoForDeletion(VNInfo *ValNo) {
464 if (ValNo->id == getNumValNums()-1) {
467 } while (!valnos.empty() && valnos.back()->isUnused());
473 /// RenumberValues - Renumber all values in order of appearance and delete the
474 /// remaining unused values.
475 void LiveRange::RenumberValues() {
476 SmallPtrSet<VNInfo*, 8> Seen;
478 for (const Segment &S : segments) {
479 VNInfo *VNI = S.valno;
480 if (!Seen.insert(VNI).second)
482 assert(!VNI->isUnused() && "Unused valno used by live segment");
483 VNI->id = (unsigned)valnos.size();
484 valnos.push_back(VNI);
488 void LiveRange::addSegmentToSet(Segment S) {
489 CalcLiveRangeUtilSet(this).addSegment(S);
492 LiveRange::iterator LiveRange::addSegment(Segment S) {
493 // Use the segment set, if it is available.
494 if (segmentSet != nullptr) {
498 // Otherwise use the segment vector.
499 return CalcLiveRangeUtilVector(this).addSegment(S);
502 void LiveRange::append(const Segment S) {
503 // Check that the segment belongs to the back of the list.
504 assert(segments.empty() || segments.back().end <= S.start);
505 segments.push_back(S);
508 /// extendInBlock - If this range is live before Kill in the basic
509 /// block that starts at StartIdx, extend it to be live up to Kill and return
510 /// the value. If there is no live range before Kill, return NULL.
511 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
512 // Use the segment set, if it is available.
513 if (segmentSet != nullptr)
514 return CalcLiveRangeUtilSet(this).extendInBlock(StartIdx, Kill);
515 // Otherwise use the segment vector.
516 return CalcLiveRangeUtilVector(this).extendInBlock(StartIdx, Kill);
519 /// Remove the specified segment from this range. Note that the segment must
520 /// be in a single Segment in its entirety.
521 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
522 bool RemoveDeadValNo) {
523 // Find the Segment containing this span.
524 iterator I = find(Start);
525 assert(I != end() && "Segment is not in range!");
526 assert(I->containsInterval(Start, End)
527 && "Segment is not entirely in range!");
529 // If the span we are removing is at the start of the Segment, adjust it.
530 VNInfo *ValNo = I->valno;
531 if (I->start == Start) {
533 if (RemoveDeadValNo) {
534 // Check if val# is dead.
536 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
537 if (II != I && II->valno == ValNo) {
542 // Now that ValNo is dead, remove it.
543 markValNoForDeletion(ValNo);
547 segments.erase(I); // Removed the whole Segment.
553 // Otherwise if the span we are removing is at the end of the Segment,
554 // adjust the other way.
560 // Otherwise, we are splitting the Segment into two pieces.
561 SlotIndex OldEnd = I->end;
562 I->end = Start; // Trim the old segment.
564 // Insert the new one.
565 segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
568 /// removeValNo - Remove all the segments defined by the specified value#.
569 /// Also remove the value# from value# list.
570 void LiveRange::removeValNo(VNInfo *ValNo) {
572 segments.erase(std::remove_if(begin(), end(), [ValNo](const Segment &S) {
573 return S.valno == ValNo;
575 // Now that ValNo is dead, remove it.
576 markValNoForDeletion(ValNo);
579 void LiveRange::join(LiveRange &Other,
580 const int *LHSValNoAssignments,
581 const int *RHSValNoAssignments,
582 SmallVectorImpl<VNInfo *> &NewVNInfo) {
585 // Determine if any of our values are mapped. This is uncommon, so we want
586 // to avoid the range scan if not.
587 bool MustMapCurValNos = false;
588 unsigned NumVals = getNumValNums();
589 unsigned NumNewVals = NewVNInfo.size();
590 for (unsigned i = 0; i != NumVals; ++i) {
591 unsigned LHSValID = LHSValNoAssignments[i];
593 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
594 MustMapCurValNos = true;
599 // If we have to apply a mapping to our base range assignment, rewrite it now.
600 if (MustMapCurValNos && !empty()) {
601 // Map the first live range.
603 iterator OutIt = begin();
604 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
605 for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
606 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
607 assert(nextValNo && "Huh?");
609 // If this live range has the same value # as its immediate predecessor,
610 // and if they are neighbors, remove one Segment. This happens when we
611 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
612 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
615 // Didn't merge. Move OutIt to the next segment,
617 OutIt->valno = nextValNo;
619 OutIt->start = I->start;
624 // If we merge some segments, chop off the end.
626 segments.erase(OutIt, end());
629 // Rewrite Other values before changing the VNInfo ids.
630 // This can leave Other in an invalid state because we're not coalescing
631 // touching segments that now have identical values. That's OK since Other is
632 // not supposed to be valid after calling join();
633 for (Segment &S : Other.segments)
634 S.valno = NewVNInfo[RHSValNoAssignments[S.valno->id]];
636 // Update val# info. Renumber them and make sure they all belong to this
637 // LiveRange now. Also remove dead val#'s.
638 unsigned NumValNos = 0;
639 for (unsigned i = 0; i < NumNewVals; ++i) {
640 VNInfo *VNI = NewVNInfo[i];
642 if (NumValNos >= NumVals)
643 valnos.push_back(VNI);
645 valnos[NumValNos] = VNI;
646 VNI->id = NumValNos++; // Renumber val#.
649 if (NumNewVals < NumVals)
650 valnos.resize(NumNewVals); // shrinkify
652 // Okay, now insert the RHS live segments into the LHS.
653 LiveRangeUpdater Updater(this);
654 for (Segment &S : Other.segments)
658 /// Merge all of the segments in RHS into this live range as the specified
659 /// value number. The segments in RHS are allowed to overlap with segments in
660 /// the current range, but only if the overlapping segments have the
661 /// specified value number.
662 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
664 LiveRangeUpdater Updater(this);
665 for (const Segment &S : RHS.segments)
666 Updater.add(S.start, S.end, LHSValNo);
669 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
670 /// in RHS into this live range as the specified value number.
671 /// The segments in RHS are allowed to overlap with segments in the
672 /// current range, it will replace the value numbers of the overlaped
673 /// segments with the specified value number.
674 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
675 const VNInfo *RHSValNo,
677 LiveRangeUpdater Updater(this);
678 for (const Segment &S : RHS.segments)
679 if (S.valno == RHSValNo)
680 Updater.add(S.start, S.end, LHSValNo);
683 /// MergeValueNumberInto - This method is called when two value nubmers
684 /// are found to be equivalent. This eliminates V1, replacing all
685 /// segments with the V1 value number with the V2 value number. This can
686 /// cause merging of V1/V2 values numbers and compaction of the value space.
687 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
688 assert(V1 != V2 && "Identical value#'s are always equivalent!");
690 // This code actually merges the (numerically) larger value number into the
691 // smaller value number, which is likely to allow us to compactify the value
692 // space. The only thing we have to be careful of is to preserve the
693 // instruction that defines the result value.
695 // Make sure V2 is smaller than V1.
696 if (V1->id < V2->id) {
701 // Merge V1 segments into V2.
702 for (iterator I = begin(); I != end(); ) {
704 if (S->valno != V1) continue; // Not a V1 Segment.
706 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
710 if (Prev->valno == V2 && Prev->end == S->start) {
713 // Erase this live-range.
720 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
721 // Ensure that it is a V2 live-range.
724 // If we can merge it into later V2 segments, do so now. We ignore any
725 // following V1 segments, as they will be merged in subsequent iterations
728 if (I->start == S->end && I->valno == V2) {
736 // Now that V1 is dead, remove it.
737 markValNoForDeletion(V1);
742 void LiveRange::flushSegmentSet() {
743 assert(segmentSet != nullptr && "segment set must have been created");
746 "segment set can be used only initially before switching to the array");
747 segments.append(segmentSet->begin(), segmentSet->end());
748 segmentSet = nullptr;
752 void LiveInterval::freeSubRange(SubRange *S) {
754 // Memory was allocated with BumpPtr allocator and is not freed here.
757 void LiveInterval::removeEmptySubRanges() {
758 SubRange **NextPtr = &SubRanges;
759 SubRange *I = *NextPtr;
760 while (I != nullptr) {
766 // Skip empty subranges until we find the first nonempty one.
768 SubRange *Next = I->Next;
771 } while (I != nullptr && I->empty());
776 void LiveInterval::clearSubRanges() {
777 for (SubRange *I = SubRanges, *Next; I != nullptr; I = Next) {
784 /// Helper function for constructMainRangeFromSubranges(): Search the CFG
785 /// backwards until we find a place covered by a LiveRange segment that actually
787 static VNInfo *searchForVNI(const SlotIndexes &Indexes, LiveRange &LR,
788 const MachineBasicBlock *MBB,
789 SmallPtrSetImpl<const MachineBasicBlock*> &Visited) {
790 // We start the search at the end of MBB.
791 SlotIndex EndIdx = Indexes.getMBBEndIdx(MBB);
792 // In our use case we can't live the area covered by the live segments without
793 // finding an actual VNI def.
794 LiveRange::iterator I = LR.find(EndIdx.getPrevSlot());
795 assert(I != LR.end());
796 LiveRange::Segment &S = *I;
797 if (S.valno != nullptr)
800 VNInfo *VNI = nullptr;
801 // Continue at predecessors (we could even go to idom with domtree available).
802 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
803 // Avoid going in circles.
804 if (!Visited.insert(Pred).second)
807 VNI = searchForVNI(Indexes, LR, Pred, Visited);
808 if (VNI != nullptr) {
817 static void determineMissingVNIs(const SlotIndexes &Indexes, LiveInterval &LI) {
818 SmallPtrSet<const MachineBasicBlock*, 5> Visited;
820 LiveRange::iterator OutIt;
821 VNInfo *PrevValNo = nullptr;
822 for (LiveRange::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
823 LiveRange::Segment &S = *I;
824 // Determine final VNI if necessary.
825 if (S.valno == nullptr) {
826 // This can only happen at the begin of a basic block.
827 assert(S.start.isBlock() && "valno should only be missing at block begin");
830 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
831 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
832 VNInfo *VNI = searchForVNI(Indexes, LI, Pred, Visited);
833 if (VNI != nullptr) {
838 assert(S.valno != nullptr && "could not determine valno");
840 // Merge with previous segment if it has the same VNI.
841 if (PrevValNo == S.valno && OutIt->end == S.start) {
844 // Didn't merge. Move OutIt to next segment.
845 if (PrevValNo == nullptr)
855 // If we merged some segments chop off the end.
857 LI.segments.erase(OutIt, LI.end());
860 void LiveInterval::constructMainRangeFromSubranges(
861 const SlotIndexes &Indexes, VNInfo::Allocator &VNIAllocator) {
862 // The basic observations on which this algorithm is based:
863 // - Each Def/ValNo in a subrange must have a corresponding def on the main
864 // range, but not further defs/valnos are necessary.
865 // - If any of the subranges is live at a point the main liverange has to be
866 // live too, conversily if no subrange is live the main range mustn't be
868 // We do this by scannig through all the subranges simultaneously creating new
869 // segments in the main range as segments start/ends come up in the subranges.
870 assert(hasSubRanges() && "expected subranges to be present");
871 assert(segments.empty() && valnos.empty() && "expected empty main range");
873 // Collect subrange, iterator pairs for the walk and determine first and last
874 // SlotIndex involved.
875 SmallVector<std::pair<const SubRange*, const_iterator>, 4> SRs;
878 for (const SubRange &SR : subranges()) {
881 SRs.push_back(std::make_pair(&SR, SR.begin()));
882 if (!First.isValid() || SR.segments.front().start < First)
883 First = SR.segments.front().start;
884 if (!Last.isValid() || SR.segments.back().end > Last)
885 Last = SR.segments.back().end;
888 // Walk over all subranges simultaneously.
889 Segment CurrentSegment;
890 bool ConstructingSegment = false;
891 bool NeedVNIFixup = false;
892 unsigned ActiveMask = 0;
893 SlotIndex Pos = First;
895 SlotIndex NextPos = Last;
901 // Which subregister lanes are affected by the current event.
902 unsigned EventMask = 0;
903 // Whether a BEGIN_SEGMENT is also a valno definition point.
905 // Find the next begin or end of a subrange segment. Combine masks if we
906 // have multiple begins/ends at the same position. Ends take precedence over
908 for (auto &SRP : SRs) {
909 const SubRange &SR = *SRP.first;
910 const_iterator &I = SRP.second;
911 // Advance iterator of subrange to a segment involving Pos; the earlier
912 // segments are already merged at this point.
913 while (I != SR.end() &&
915 (I->end == Pos && (ActiveMask & SR.LaneMask) == 0)))
919 if ((ActiveMask & SR.LaneMask) == 0 &&
920 Pos <= I->start && I->start <= NextPos) {
921 // Merge multiple begins at the same position.
922 if (I->start == NextPos && Event == BEGIN_SEGMENT) {
923 EventMask |= SR.LaneMask;
924 IsDef |= I->valno->def == I->start;
925 } else if (I->start < NextPos || Event != END_SEGMENT) {
926 Event = BEGIN_SEGMENT;
928 EventMask = SR.LaneMask;
929 IsDef = I->valno->def == I->start;
932 if ((ActiveMask & SR.LaneMask) != 0 &&
933 Pos <= I->end && I->end <= NextPos) {
934 // Merge multiple ends at the same position.
935 if (I->end == NextPos && Event == END_SEGMENT)
936 EventMask |= SR.LaneMask;
940 EventMask = SR.LaneMask;
945 // Advance scan position.
947 if (Event == BEGIN_SEGMENT) {
948 if (ConstructingSegment && IsDef) {
949 // Finish previous segment because we have to start a new one.
950 CurrentSegment.end = Pos;
951 append(CurrentSegment);
952 ConstructingSegment = false;
955 // Start a new segment if necessary.
956 if (!ConstructingSegment) {
957 // Determine value number for the segment.
960 VNI = getNextValue(Pos, VNIAllocator);
962 // We have to reuse an existing value number, if we are lucky
963 // then we already passed one of the predecessor blocks and determined
964 // its value number (with blocks in reverse postorder this would be
965 // always true but we have no such guarantee).
966 assert(Pos.isBlock());
967 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Pos);
968 // See if any of the predecessor blocks has a lower number and a VNI
969 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
970 SlotIndex PredEnd = Indexes.getMBBEndIdx(Pred);
971 VNI = getVNInfoBefore(PredEnd);
975 // Def will come later: We have to do an extra fixup pass.
980 // In rare cases we can produce adjacent segments with the same value
981 // number (if they come from different subranges, but happen to have
982 // the same defining instruction). VNIFixup will fix those cases.
983 if (!empty() && segments.back().end == Pos &&
984 segments.back().valno == VNI)
986 CurrentSegment.start = Pos;
987 CurrentSegment.valno = VNI;
988 ConstructingSegment = true;
990 ActiveMask |= EventMask;
991 } else if (Event == END_SEGMENT) {
992 assert(ConstructingSegment);
993 // Finish segment if no lane is active anymore.
994 ActiveMask &= ~EventMask;
995 if (ActiveMask == 0) {
996 CurrentSegment.end = Pos;
997 append(CurrentSegment);
998 ConstructingSegment = false;
1001 // We reached the end of the last subranges and can stop.
1002 assert(Event == NOTHING);
1007 // We might not be able to assign new valnos for all segments if the basic
1008 // block containing the definition comes after a segment using the valno.
1009 // Do a fixup pass for this uncommon case.
1011 determineMissingVNIs(Indexes, *this);
1013 assert(ActiveMask == 0 && !ConstructingSegment && "all segments ended");
1017 unsigned LiveInterval::getSize() const {
1019 for (const Segment &S : segments)
1020 Sum += S.start.distance(S.end);
1024 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
1025 return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ")";
1028 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1029 void LiveRange::Segment::dump() const {
1030 dbgs() << *this << "\n";
1034 void LiveRange::print(raw_ostream &OS) const {
1038 for (const Segment &S : segments) {
1040 assert(S.valno == getValNumInfo(S.valno->id) && "Bad VNInfo");
1044 // Print value number info.
1045 if (getNumValNums()) {
1048 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
1050 const VNInfo *vni = *i;
1051 if (vnum) OS << " ";
1053 if (vni->isUnused()) {
1057 if (vni->isPHIDef())
1064 void LiveInterval::print(raw_ostream &OS) const {
1065 OS << PrintReg(reg) << ' ';
1068 for (const SubRange &SR : subranges()) {
1069 OS << format(" L%04X ", SR.LaneMask) << SR;
1073 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1074 void LiveRange::dump() const {
1075 dbgs() << *this << "\n";
1078 void LiveInterval::dump() const {
1079 dbgs() << *this << "\n";
1084 void LiveRange::verify() const {
1085 for (const_iterator I = begin(), E = end(); I != E; ++I) {
1086 assert(I->start.isValid());
1087 assert(I->end.isValid());
1088 assert(I->start < I->end);
1089 assert(I->valno != nullptr);
1090 assert(I->valno->id < valnos.size());
1091 assert(I->valno == valnos[I->valno->id]);
1092 if (std::next(I) != E) {
1093 assert(I->end <= std::next(I)->start);
1094 if (I->end == std::next(I)->start)
1095 assert(I->valno != std::next(I)->valno);
1100 void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
1103 // Make sure SubRanges are fine and LaneMasks are disjunct.
1105 unsigned MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg) : ~0u;
1106 for (const SubRange &SR : subranges()) {
1107 // Subrange lanemask should be disjunct to any previous subrange masks.
1108 assert((Mask & SR.LaneMask) == 0);
1109 Mask |= SR.LaneMask;
1111 // subrange mask should not contained in maximum lane mask for the vreg.
1112 assert((Mask & ~MaxMask) == 0);
1113 // empty subranges must be removed.
1114 assert(!SR.empty());
1117 // Main liverange should cover subrange.
1124 //===----------------------------------------------------------------------===//
1125 // LiveRangeUpdater class
1126 //===----------------------------------------------------------------------===//
1128 // The LiveRangeUpdater class always maintains these invariants:
1130 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
1131 // This is the initial state, and the state created by flush().
1132 // In this state, isDirty() returns false.
1134 // Otherwise, segments are kept in three separate areas:
1136 // 1. [begin; WriteI) at the front of LR.
1137 // 2. [ReadI; end) at the back of LR.
1140 // - LR.begin() <= WriteI <= ReadI <= LR.end().
1141 // - Segments in all three areas are fully ordered and coalesced.
1142 // - Segments in area 1 precede and can't coalesce with segments in area 2.
1143 // - Segments in Spills precede and can't coalesce with segments in area 2.
1144 // - No coalescing is possible between segments in Spills and segments in area
1145 // 1, and there are no overlapping segments.
1147 // The segments in Spills are not ordered with respect to the segments in area
1148 // 1. They need to be merged.
1150 // When they exist, Spills.back().start <= LastStart,
1151 // and WriteI[-1].start <= LastStart.
1153 void LiveRangeUpdater::print(raw_ostream &OS) const {
1156 OS << "Clean updater: " << *LR << '\n';
1158 OS << "Null updater.\n";
1161 assert(LR && "Can't have null LR in dirty updater.");
1162 OS << " updater with gap = " << (ReadI - WriteI)
1163 << ", last start = " << LastStart
1165 for (const auto &S : make_range(LR->begin(), WriteI))
1168 for (unsigned I = 0, E = Spills.size(); I != E; ++I)
1169 OS << ' ' << Spills[I];
1171 for (const auto &S : make_range(ReadI, LR->end()))
1176 void LiveRangeUpdater::dump() const
1181 // Determine if A and B should be coalesced.
1182 static inline bool coalescable(const LiveRange::Segment &A,
1183 const LiveRange::Segment &B) {
1184 assert(A.start <= B.start && "Unordered live segments.");
1185 if (A.end == B.start)
1186 return A.valno == B.valno;
1187 if (A.end < B.start)
1189 assert(A.valno == B.valno && "Cannot overlap different values");
1193 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
1194 assert(LR && "Cannot add to a null destination");
1196 // Fall back to the regular add method if the live range
1197 // is using the segment set instead of the segment vector.
1198 if (LR->segmentSet != nullptr) {
1199 LR->addSegmentToSet(Seg);
1203 // Flush the state if Start moves backwards.
1204 if (!LastStart.isValid() || LastStart > Seg.start) {
1207 // This brings us to an uninitialized state. Reinitialize.
1208 assert(Spills.empty() && "Leftover spilled segments");
1209 WriteI = ReadI = LR->begin();
1212 // Remember start for next time.
1213 LastStart = Seg.start;
1215 // Advance ReadI until it ends after Seg.start.
1216 LiveRange::iterator E = LR->end();
1217 if (ReadI != E && ReadI->end <= Seg.start) {
1218 // First try to close the gap between WriteI and ReadI with spills.
1219 if (ReadI != WriteI)
1221 // Then advance ReadI.
1222 if (ReadI == WriteI)
1223 ReadI = WriteI = LR->find(Seg.start);
1225 while (ReadI != E && ReadI->end <= Seg.start)
1226 *WriteI++ = *ReadI++;
1229 assert(ReadI == E || ReadI->end > Seg.start);
1231 // Check if the ReadI segment begins early.
1232 if (ReadI != E && ReadI->start <= Seg.start) {
1233 assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
1234 // Bail if Seg is completely contained in ReadI.
1235 if (ReadI->end >= Seg.end)
1237 // Coalesce into Seg.
1238 Seg.start = ReadI->start;
1242 // Coalesce as much as possible from ReadI into Seg.
1243 while (ReadI != E && coalescable(Seg, *ReadI)) {
1244 Seg.end = std::max(Seg.end, ReadI->end);
1248 // Try coalescing Spills.back() into Seg.
1249 if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
1250 Seg.start = Spills.back().start;
1251 Seg.end = std::max(Spills.back().end, Seg.end);
1255 // Try coalescing Seg into WriteI[-1].
1256 if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
1257 WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
1261 // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
1262 if (WriteI != ReadI) {
1267 // Finally, append to LR or Spills.
1269 LR->segments.push_back(Seg);
1270 WriteI = ReadI = LR->end();
1272 Spills.push_back(Seg);
1275 // Merge as many spilled segments as possible into the gap between WriteI
1276 // and ReadI. Advance WriteI to reflect the inserted instructions.
1277 void LiveRangeUpdater::mergeSpills() {
1278 // Perform a backwards merge of Spills and [SpillI;WriteI).
1279 size_t GapSize = ReadI - WriteI;
1280 size_t NumMoved = std::min(Spills.size(), GapSize);
1281 LiveRange::iterator Src = WriteI;
1282 LiveRange::iterator Dst = Src + NumMoved;
1283 LiveRange::iterator SpillSrc = Spills.end();
1284 LiveRange::iterator B = LR->begin();
1286 // This is the new WriteI position after merging spills.
1289 // Now merge Src and Spills backwards.
1290 while (Src != Dst) {
1291 if (Src != B && Src[-1].start > SpillSrc[-1].start)
1294 *--Dst = *--SpillSrc;
1296 assert(NumMoved == size_t(Spills.end() - SpillSrc));
1297 Spills.erase(SpillSrc, Spills.end());
1300 void LiveRangeUpdater::flush() {
1303 // Clear the dirty state.
1304 LastStart = SlotIndex();
1306 assert(LR && "Cannot add to a null destination");
1308 // Nothing to merge?
1309 if (Spills.empty()) {
1310 LR->segments.erase(WriteI, ReadI);
1315 // Resize the WriteI - ReadI gap to match Spills.
1316 size_t GapSize = ReadI - WriteI;
1317 if (GapSize < Spills.size()) {
1318 // The gap is too small. Make some room.
1319 size_t WritePos = WriteI - LR->begin();
1320 LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
1321 // This also invalidated ReadI, but it is recomputed below.
1322 WriteI = LR->begin() + WritePos;
1324 // Shrink the gap if necessary.
1325 LR->segments.erase(WriteI + Spills.size(), ReadI);
1327 ReadI = WriteI + Spills.size();
1332 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
1333 // Create initial equivalence classes.
1335 EqClass.grow(LI->getNumValNums());
1337 const VNInfo *used = nullptr, *unused = nullptr;
1339 // Determine connections.
1340 for (const VNInfo *VNI : LI->valnos) {
1341 // Group all unused values into one class.
1342 if (VNI->isUnused()) {
1344 EqClass.join(unused->id, VNI->id);
1349 if (VNI->isPHIDef()) {
1350 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
1351 assert(MBB && "Phi-def has no defining MBB");
1352 // Connect to values live out of predecessors.
1353 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
1354 PE = MBB->pred_end(); PI != PE; ++PI)
1355 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
1356 EqClass.join(VNI->id, PVNI->id);
1358 // Normal value defined by an instruction. Check for two-addr redef.
1359 // FIXME: This could be coincidental. Should we really check for a tied
1360 // operand constraint?
1361 // Note that VNI->def may be a use slot for an early clobber def.
1362 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
1363 EqClass.join(VNI->id, UVNI->id);
1367 // Lump all the unused values in with the last used value.
1369 EqClass.join(used->id, unused->id);
1372 return EqClass.getNumClasses();
1375 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
1376 MachineRegisterInfo &MRI) {
1377 assert(LIV[0] && "LIV[0] must be set");
1378 LiveInterval &LI = *LIV[0];
1380 // Rewrite instructions.
1381 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
1382 RE = MRI.reg_end(); RI != RE;) {
1383 MachineOperand &MO = *RI;
1384 MachineInstr *MI = RI->getParent();
1386 // DBG_VALUE instructions don't have slot indexes, so get the index of the
1387 // instruction before them.
1388 // Normally, DBG_VALUE instructions are removed before this function is
1389 // called, but it is not a requirement.
1391 if (MI->isDebugValue())
1392 Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
1394 Idx = LIS.getInstructionIndex(MI);
1395 LiveQueryResult LRQ = LI.Query(Idx);
1396 const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
1397 // In the case of an <undef> use that isn't tied to any def, VNI will be
1398 // NULL. If the use is tied to a def, VNI will be the defined value.
1401 MO.setReg(LIV[getEqClass(VNI)]->reg);
1404 // Move runs to new intervals.
1405 LiveInterval::iterator J = LI.begin(), E = LI.end();
1406 while (J != E && EqClass[J->valno->id] == 0)
1408 for (LiveInterval::iterator I = J; I != E; ++I) {
1409 if (unsigned eq = EqClass[I->valno->id]) {
1410 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
1411 "New intervals should be empty");
1412 LIV[eq]->segments.push_back(*I);
1416 // TODO: do not cheat anymore by simply cleaning all subranges
1417 LI.clearSubRanges();
1418 LI.segments.erase(J, E);
1420 // Transfer VNInfos to their new owners and renumber them.
1421 unsigned j = 0, e = LI.getNumValNums();
1422 while (j != e && EqClass[j] == 0)
1424 for (unsigned i = j; i != e; ++i) {
1425 VNInfo *VNI = LI.getValNumInfo(i);
1426 if (unsigned eq = EqClass[i]) {
1427 VNI->id = LIV[eq]->getNumValNums();
1428 LIV[eq]->valnos.push_back(VNI);
1431 LI.valnos[j++] = VNI;
1434 LI.valnos.resize(j);