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"
35 //===----------------------------------------------------------------------===//
36 // Implementation of various methods necessary for calculation of live ranges.
37 // The implementation of the methods abstracts from the concrete type of the
38 // segment collection.
40 // Implementation of the class follows the Template design pattern. The base
41 // class contains generic algorithms that call collection-specific methods,
42 // which are provided in concrete subclasses. In order to avoid virtual calls
43 // these methods are provided by means of C++ template instantiation.
44 // The base class calls the methods of the subclass through method impl(),
45 // which casts 'this' pointer to the type of the subclass.
47 //===----------------------------------------------------------------------===//
49 template <typename ImplT, typename IteratorT, typename CollectionT>
50 class CalcLiveRangeUtilBase {
55 CalcLiveRangeUtilBase(LiveRange *LR) : LR(LR) {}
58 typedef LiveRange::Segment Segment;
59 typedef IteratorT iterator;
61 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator) {
62 assert(!Def.isDead() && "Cannot define a value at the dead slot");
64 iterator I = impl().find(Def);
65 if (I == segments().end()) {
66 VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
67 impl().insertAtEnd(Segment(Def, Def.getDeadSlot(), VNI));
71 Segment *S = segmentAt(I);
72 if (SlotIndex::isSameInstr(Def, S->start)) {
73 assert(S->valno->def == S->start && "Inconsistent existing value def");
75 // It is possible to have both normal and early-clobber defs of the same
76 // register on an instruction. It doesn't make a lot of sense, but it is
77 // possible to specify in inline assembly.
79 // Just convert everything to early-clobber.
80 Def = std::min(Def, S->start);
82 S->start = S->valno->def = Def;
85 assert(SlotIndex::isEarlierInstr(Def, S->start) && "Already live at def");
86 VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
87 segments().insert(I, Segment(Def, Def.getDeadSlot(), VNI));
91 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Use) {
92 if (segments().empty())
95 impl().findInsertPos(Segment(Use.getPrevSlot(), Use, nullptr));
96 if (I == segments().begin())
99 if (I->end <= StartIdx)
102 extendSegmentEndTo(I, Use);
106 /// This method is used when we want to extend the segment specified
107 /// by I to end at the specified endpoint. To do this, we should
108 /// merge and eliminate all segments that this will overlap
109 /// with. The iterator is not invalidated.
110 void extendSegmentEndTo(iterator I, SlotIndex NewEnd) {
111 assert(I != segments().end() && "Not a valid segment!");
112 Segment *S = segmentAt(I);
113 VNInfo *ValNo = I->valno;
115 // Search for the first segment that we can't merge with.
116 iterator MergeTo = std::next(I);
117 for (; MergeTo != segments().end() && NewEnd >= MergeTo->end; ++MergeTo)
118 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
120 // If NewEnd was in the middle of a segment, make sure to get its endpoint.
121 S->end = std::max(NewEnd, std::prev(MergeTo)->end);
123 // If the newly formed segment now touches the segment after it and if they
124 // have the same value number, merge the two segments into one segment.
125 if (MergeTo != segments().end() && MergeTo->start <= I->end &&
126 MergeTo->valno == ValNo) {
127 S->end = MergeTo->end;
131 // Erase any dead segments.
132 segments().erase(std::next(I), MergeTo);
135 /// This method is used when we want to extend the segment specified
136 /// by I to start at the specified endpoint. To do this, we should
137 /// merge and eliminate all segments that this will overlap with.
138 iterator extendSegmentStartTo(iterator I, SlotIndex NewStart) {
139 assert(I != segments().end() && "Not a valid segment!");
140 Segment *S = segmentAt(I);
141 VNInfo *ValNo = I->valno;
143 // Search for the first segment that we can't merge with.
144 iterator MergeTo = I;
146 if (MergeTo == segments().begin()) {
148 segments().erase(MergeTo, I);
151 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
153 } while (NewStart <= MergeTo->start);
155 // If we start in the middle of another segment, just delete a range and
156 // extend that segment.
157 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
158 segmentAt(MergeTo)->end = S->end;
160 // Otherwise, extend the segment right after.
162 Segment *MergeToSeg = segmentAt(MergeTo);
163 MergeToSeg->start = NewStart;
164 MergeToSeg->end = S->end;
167 segments().erase(std::next(MergeTo), std::next(I));
171 iterator addSegment(Segment S) {
172 SlotIndex Start = S.start, End = S.end;
173 iterator I = impl().findInsertPos(S);
175 // If the inserted segment starts in the middle or right at the end of
176 // another segment, just extend that segment to contain the segment of S.
177 if (I != segments().begin()) {
178 iterator B = std::prev(I);
179 if (S.valno == B->valno) {
180 if (B->start <= Start && B->end >= Start) {
181 extendSegmentEndTo(B, End);
185 // Check to make sure that we are not overlapping two live segments with
186 // different valno's.
187 assert(B->end <= Start &&
188 "Cannot overlap two segments with differing ValID's"
189 " (did you def the same reg twice in a MachineInstr?)");
193 // Otherwise, if this segment ends in the middle of, or right next
194 // to, another segment, merge it into that segment.
195 if (I != segments().end()) {
196 if (S.valno == I->valno) {
197 if (I->start <= End) {
198 I = extendSegmentStartTo(I, Start);
200 // If S is a complete superset of a segment, we may need to grow its
203 extendSegmentEndTo(I, End);
207 // Check to make sure that we are not overlapping two live segments with
208 // different valno's.
209 assert(I->start >= End &&
210 "Cannot overlap two segments with differing ValID's");
214 // Otherwise, this is just a new segment that doesn't interact with
217 return segments().insert(I, S);
221 ImplT &impl() { return *static_cast<ImplT *>(this); }
223 CollectionT &segments() { return impl().segmentsColl(); }
225 Segment *segmentAt(iterator I) { return const_cast<Segment *>(&(*I)); }
228 //===----------------------------------------------------------------------===//
229 // Instantiation of the methods for calculation of live ranges
230 // based on a segment vector.
231 //===----------------------------------------------------------------------===//
233 class CalcLiveRangeUtilVector;
234 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilVector, LiveRange::iterator,
235 LiveRange::Segments> CalcLiveRangeUtilVectorBase;
237 class CalcLiveRangeUtilVector : public CalcLiveRangeUtilVectorBase {
239 CalcLiveRangeUtilVector(LiveRange *LR) : CalcLiveRangeUtilVectorBase(LR) {}
242 friend CalcLiveRangeUtilVectorBase;
244 LiveRange::Segments &segmentsColl() { return LR->segments; }
246 void insertAtEnd(const Segment &S) { LR->segments.push_back(S); }
248 iterator find(SlotIndex Pos) { return LR->find(Pos); }
250 iterator findInsertPos(Segment S) {
251 return std::upper_bound(LR->begin(), LR->end(), S.start);
255 //===----------------------------------------------------------------------===//
256 // Instantiation of the methods for calculation of live ranges
257 // based on a segment set.
258 //===----------------------------------------------------------------------===//
260 class CalcLiveRangeUtilSet;
261 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilSet,
262 LiveRange::SegmentSet::iterator,
263 LiveRange::SegmentSet> CalcLiveRangeUtilSetBase;
265 class CalcLiveRangeUtilSet : public CalcLiveRangeUtilSetBase {
267 CalcLiveRangeUtilSet(LiveRange *LR) : CalcLiveRangeUtilSetBase(LR) {}
270 friend CalcLiveRangeUtilSetBase;
272 LiveRange::SegmentSet &segmentsColl() { return *LR->segmentSet; }
274 void insertAtEnd(const Segment &S) {
275 LR->segmentSet->insert(LR->segmentSet->end(), S);
278 iterator find(SlotIndex Pos) {
280 LR->segmentSet->upper_bound(Segment(Pos, Pos.getNextSlot(), nullptr));
281 if (I == LR->segmentSet->begin())
283 iterator PrevI = std::prev(I);
284 if (Pos < (*PrevI).end)
289 iterator findInsertPos(Segment S) {
290 iterator I = LR->segmentSet->upper_bound(S);
291 if (I != LR->segmentSet->end() && !(S.start < *I))
297 //===----------------------------------------------------------------------===//
299 //===----------------------------------------------------------------------===//
301 LiveRange::iterator LiveRange::find(SlotIndex Pos) {
302 // This algorithm is basically std::upper_bound.
303 // Unfortunately, std::upper_bound cannot be used with mixed types until we
304 // adopt C++0x. Many libraries can do it, but not all.
305 if (empty() || Pos >= endIndex())
307 iterator I = begin();
310 size_t Mid = Len >> 1;
311 if (Pos < I[Mid].end)
314 I += Mid + 1, Len -= Mid + 1;
319 VNInfo *LiveRange::createDeadDef(SlotIndex Def,
320 VNInfo::Allocator &VNInfoAllocator) {
321 // Use the segment set, if it is available.
322 if (segmentSet != nullptr)
323 return CalcLiveRangeUtilSet(this).createDeadDef(Def, VNInfoAllocator);
324 // Otherwise use the segment vector.
325 return CalcLiveRangeUtilVector(this).createDeadDef(Def, VNInfoAllocator);
328 // overlaps - Return true if the intersection of the two live ranges is
331 // An example for overlaps():
335 // 8: C = A + B ;; last use of A
337 // The live ranges should look like:
343 // A->overlaps(C) should return false since we want to be able to join
346 bool LiveRange::overlapsFrom(const LiveRange& other,
347 const_iterator StartPos) const {
348 assert(!empty() && "empty range");
349 const_iterator i = begin();
350 const_iterator ie = end();
351 const_iterator j = StartPos;
352 const_iterator je = other.end();
354 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
355 StartPos != other.end() && "Bogus start position hint!");
357 if (i->start < j->start) {
358 i = std::upper_bound(i, ie, j->start);
359 if (i != begin()) --i;
360 } else if (j->start < i->start) {
362 if (StartPos != other.end() && StartPos->start <= i->start) {
363 assert(StartPos < other.end() && i < end());
364 j = std::upper_bound(j, je, i->start);
365 if (j != other.begin()) --j;
371 if (j == je) return false;
374 if (i->start > j->start) {
379 if (i->end > j->start)
387 bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
388 const SlotIndexes &Indexes) const {
389 assert(!empty() && "empty range");
393 // Use binary searches to find initial positions.
394 const_iterator I = find(Other.beginIndex());
395 const_iterator IE = end();
398 const_iterator J = Other.find(I->start);
399 const_iterator JE = Other.end();
404 // J has just been advanced to satisfy:
405 assert(J->end >= I->start);
406 // Check for an overlap.
407 if (J->start < I->end) {
408 // I and J are overlapping. Find the later start.
409 SlotIndex Def = std::max(I->start, J->start);
410 // Allow the overlap if Def is a coalescable copy.
412 !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
415 // Advance the iterator that ends first to check for more overlaps.
416 if (J->end > I->end) {
420 // Advance J until J->end >= I->start.
424 while (J->end < I->start);
428 /// overlaps - Return true if the live range overlaps an interval specified
430 bool LiveRange::overlaps(SlotIndex Start, SlotIndex End) const {
431 assert(Start < End && "Invalid range");
432 const_iterator I = std::lower_bound(begin(), end(), End);
433 return I != begin() && (--I)->end > Start;
436 bool LiveRange::covers(const LiveRange &Other) const {
438 return Other.empty();
440 const_iterator I = begin();
441 for (const Segment &O : Other.segments) {
442 I = advanceTo(I, O.start);
443 if (I == end() || I->start > O.start)
446 // Check adjacent live segments and see if we can get behind O.end.
447 while (I->end < O.end) {
448 const_iterator Last = I;
449 // Get next segment and abort if it was not adjacent.
451 if (I == end() || Last->end != I->start)
458 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
459 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
460 /// it can be nuked later.
461 void LiveRange::markValNoForDeletion(VNInfo *ValNo) {
462 if (ValNo->id == getNumValNums()-1) {
465 } while (!valnos.empty() && valnos.back()->isUnused());
471 /// RenumberValues - Renumber all values in order of appearance and delete the
472 /// remaining unused values.
473 void LiveRange::RenumberValues() {
474 SmallPtrSet<VNInfo*, 8> Seen;
476 for (const Segment &S : segments) {
477 VNInfo *VNI = S.valno;
478 if (!Seen.insert(VNI).second)
480 assert(!VNI->isUnused() && "Unused valno used by live segment");
481 VNI->id = (unsigned)valnos.size();
482 valnos.push_back(VNI);
486 void LiveRange::addSegmentToSet(Segment S) {
487 CalcLiveRangeUtilSet(this).addSegment(S);
490 LiveRange::iterator LiveRange::addSegment(Segment S) {
491 // Use the segment set, if it is available.
492 if (segmentSet != nullptr) {
496 // Otherwise use the segment vector.
497 return CalcLiveRangeUtilVector(this).addSegment(S);
500 void LiveRange::append(const Segment S) {
501 // Check that the segment belongs to the back of the list.
502 assert(segments.empty() || segments.back().end <= S.start);
503 segments.push_back(S);
506 /// extendInBlock - If this range is live before Kill in the basic
507 /// block that starts at StartIdx, extend it to be live up to Kill and return
508 /// the value. If there is no live range before Kill, return NULL.
509 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
510 // Use the segment set, if it is available.
511 if (segmentSet != nullptr)
512 return CalcLiveRangeUtilSet(this).extendInBlock(StartIdx, Kill);
513 // Otherwise use the segment vector.
514 return CalcLiveRangeUtilVector(this).extendInBlock(StartIdx, Kill);
517 /// Remove the specified segment from this range. Note that the segment must
518 /// be in a single Segment in its entirety.
519 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
520 bool RemoveDeadValNo) {
521 // Find the Segment containing this span.
522 iterator I = find(Start);
523 assert(I != end() && "Segment is not in range!");
524 assert(I->containsInterval(Start, End)
525 && "Segment is not entirely in range!");
527 // If the span we are removing is at the start of the Segment, adjust it.
528 VNInfo *ValNo = I->valno;
529 if (I->start == Start) {
531 if (RemoveDeadValNo) {
532 // Check if val# is dead.
534 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
535 if (II != I && II->valno == ValNo) {
540 // Now that ValNo is dead, remove it.
541 markValNoForDeletion(ValNo);
545 segments.erase(I); // Removed the whole Segment.
551 // Otherwise if the span we are removing is at the end of the Segment,
552 // adjust the other way.
558 // Otherwise, we are splitting the Segment into two pieces.
559 SlotIndex OldEnd = I->end;
560 I->end = Start; // Trim the old segment.
562 // Insert the new one.
563 segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
566 /// removeValNo - Remove all the segments defined by the specified value#.
567 /// Also remove the value# from value# list.
568 void LiveRange::removeValNo(VNInfo *ValNo) {
570 segments.erase(std::remove_if(begin(), end(), [ValNo](const Segment &S) {
571 return S.valno == ValNo;
573 // Now that ValNo is dead, remove it.
574 markValNoForDeletion(ValNo);
577 void LiveRange::join(LiveRange &Other,
578 const int *LHSValNoAssignments,
579 const int *RHSValNoAssignments,
580 SmallVectorImpl<VNInfo *> &NewVNInfo) {
583 // Determine if any of our values are mapped. This is uncommon, so we want
584 // to avoid the range scan if not.
585 bool MustMapCurValNos = false;
586 unsigned NumVals = getNumValNums();
587 unsigned NumNewVals = NewVNInfo.size();
588 for (unsigned i = 0; i != NumVals; ++i) {
589 unsigned LHSValID = LHSValNoAssignments[i];
591 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
592 MustMapCurValNos = true;
597 // If we have to apply a mapping to our base range assignment, rewrite it now.
598 if (MustMapCurValNos && !empty()) {
599 // Map the first live range.
601 iterator OutIt = begin();
602 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
603 for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
604 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
605 assert(nextValNo && "Huh?");
607 // If this live range has the same value # as its immediate predecessor,
608 // and if they are neighbors, remove one Segment. This happens when we
609 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
610 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
613 // Didn't merge. Move OutIt to the next segment,
615 OutIt->valno = nextValNo;
617 OutIt->start = I->start;
622 // If we merge some segments, chop off the end.
624 segments.erase(OutIt, end());
627 // Rewrite Other values before changing the VNInfo ids.
628 // This can leave Other in an invalid state because we're not coalescing
629 // touching segments that now have identical values. That's OK since Other is
630 // not supposed to be valid after calling join();
631 for (Segment &S : Other.segments)
632 S.valno = NewVNInfo[RHSValNoAssignments[S.valno->id]];
634 // Update val# info. Renumber them and make sure they all belong to this
635 // LiveRange now. Also remove dead val#'s.
636 unsigned NumValNos = 0;
637 for (unsigned i = 0; i < NumNewVals; ++i) {
638 VNInfo *VNI = NewVNInfo[i];
640 if (NumValNos >= NumVals)
641 valnos.push_back(VNI);
643 valnos[NumValNos] = VNI;
644 VNI->id = NumValNos++; // Renumber val#.
647 if (NumNewVals < NumVals)
648 valnos.resize(NumNewVals); // shrinkify
650 // Okay, now insert the RHS live segments into the LHS.
651 LiveRangeUpdater Updater(this);
652 for (Segment &S : Other.segments)
656 /// Merge all of the segments in RHS into this live range as the specified
657 /// value number. The segments in RHS are allowed to overlap with segments in
658 /// the current range, but only if the overlapping segments have the
659 /// specified value number.
660 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
662 LiveRangeUpdater Updater(this);
663 for (const Segment &S : RHS.segments)
664 Updater.add(S.start, S.end, LHSValNo);
667 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
668 /// in RHS into this live range as the specified value number.
669 /// The segments in RHS are allowed to overlap with segments in the
670 /// current range, it will replace the value numbers of the overlaped
671 /// segments with the specified value number.
672 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
673 const VNInfo *RHSValNo,
675 LiveRangeUpdater Updater(this);
676 for (const Segment &S : RHS.segments)
677 if (S.valno == RHSValNo)
678 Updater.add(S.start, S.end, LHSValNo);
681 /// MergeValueNumberInto - This method is called when two value nubmers
682 /// are found to be equivalent. This eliminates V1, replacing all
683 /// segments with the V1 value number with the V2 value number. This can
684 /// cause merging of V1/V2 values numbers and compaction of the value space.
685 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
686 assert(V1 != V2 && "Identical value#'s are always equivalent!");
688 // This code actually merges the (numerically) larger value number into the
689 // smaller value number, which is likely to allow us to compactify the value
690 // space. The only thing we have to be careful of is to preserve the
691 // instruction that defines the result value.
693 // Make sure V2 is smaller than V1.
694 if (V1->id < V2->id) {
699 // Merge V1 segments into V2.
700 for (iterator I = begin(); I != end(); ) {
702 if (S->valno != V1) continue; // Not a V1 Segment.
704 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
708 if (Prev->valno == V2 && Prev->end == S->start) {
711 // Erase this live-range.
718 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
719 // Ensure that it is a V2 live-range.
722 // If we can merge it into later V2 segments, do so now. We ignore any
723 // following V1 segments, as they will be merged in subsequent iterations
726 if (I->start == S->end && I->valno == V2) {
734 // Now that V1 is dead, remove it.
735 markValNoForDeletion(V1);
740 void LiveRange::flushSegmentSet() {
741 assert(segmentSet != nullptr && "segment set must have been created");
744 "segment set can be used only initially before switching to the array");
745 segments.append(segmentSet->begin(), segmentSet->end());
747 segmentSet = nullptr;
751 void LiveInterval::freeSubRange(SubRange *S) {
753 // Memory was allocated with BumpPtr allocator and is not freed here.
756 void LiveInterval::removeEmptySubRanges() {
757 SubRange **NextPtr = &SubRanges;
758 SubRange *I = *NextPtr;
759 while (I != nullptr) {
765 // Skip empty subranges until we find the first nonempty one.
767 SubRange *Next = I->Next;
770 } while (I != nullptr && I->empty());
775 void LiveInterval::clearSubRanges() {
776 for (SubRange *I = SubRanges, *Next; I != nullptr; I = Next) {
783 /// Helper function for constructMainRangeFromSubranges(): Search the CFG
784 /// backwards until we find a place covered by a LiveRange segment that actually
786 static VNInfo *searchForVNI(const SlotIndexes &Indexes, LiveRange &LR,
787 const MachineBasicBlock *MBB,
788 SmallPtrSetImpl<const MachineBasicBlock*> &Visited) {
789 // We start the search at the end of MBB.
790 SlotIndex EndIdx = Indexes.getMBBEndIdx(MBB);
791 // In our use case we can't live the area covered by the live segments without
792 // finding an actual VNI def.
793 LiveRange::iterator I = LR.find(EndIdx.getPrevSlot());
794 assert(I != LR.end());
795 LiveRange::Segment &S = *I;
796 if (S.valno != nullptr)
799 VNInfo *VNI = nullptr;
800 // Continue at predecessors (we could even go to idom with domtree available).
801 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
802 // Avoid going in circles.
803 if (!Visited.insert(Pred).second)
806 VNI = searchForVNI(Indexes, LR, Pred, Visited);
807 if (VNI != nullptr) {
816 static void determineMissingVNIs(const SlotIndexes &Indexes, LiveInterval &LI) {
817 SmallPtrSet<const MachineBasicBlock*, 5> Visited;
818 for (LiveRange::Segment &S : LI.segments) {
819 if (S.valno != nullptr)
821 // This can only happen at the begin of a basic block.
822 assert(S.start.isBlock() && "valno should only be missing at block begin");
825 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
826 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
827 VNInfo *VNI = searchForVNI(Indexes, LI, Pred, Visited);
828 if (VNI != nullptr) {
833 assert(S.valno != nullptr && "could not determine valno");
837 void LiveInterval::constructMainRangeFromSubranges(
838 const SlotIndexes &Indexes, VNInfo::Allocator &VNIAllocator) {
839 // The basic observations on which this algorithm is based:
840 // - Each Def/ValNo in a subrange must have a corresponding def on the main
841 // range, but not further defs/valnos are necessary.
842 // - If any of the subranges is live at a point the main liverange has to be
843 // live too, conversily if no subrange is live the main range mustn't be
845 // We do this by scannig through all the subranges simultaneously creating new
846 // segments in the main range as segments start/ends come up in the subranges.
847 assert(hasSubRanges() && "expected subranges to be present");
848 assert(segments.empty() && valnos.empty() && "expected empty main range");
850 // Collect subrange, iterator pairs for the walk and determine first and last
851 // SlotIndex involved.
852 SmallVector<std::pair<const SubRange*, const_iterator>, 4> SRs;
855 for (const SubRange &SR : subranges()) {
858 SRs.push_back(std::make_pair(&SR, SR.begin()));
859 if (!First.isValid() || SR.segments.front().start < First)
860 First = SR.segments.front().start;
861 if (!Last.isValid() || SR.segments.back().end > Last)
862 Last = SR.segments.back().end;
865 // Walk over all subranges simultaneously.
866 Segment CurrentSegment;
867 bool ConstructingSegment = false;
868 bool NeedVNIFixup = false;
869 unsigned ActiveMask = 0;
870 SlotIndex Pos = First;
872 SlotIndex NextPos = Last;
878 // Which subregister lanes are affected by the current event.
879 unsigned EventMask = 0;
880 // Whether a BEGIN_SEGMENT is also a valno definition point.
882 // Find the next begin or end of a subrange segment. Combine masks if we
883 // have multiple begins/ends at the same position. Ends take precedence over
885 for (auto &SRP : SRs) {
886 const SubRange &SR = *SRP.first;
887 const_iterator &I = SRP.second;
888 // Advance iterator of subrange to a segment involving Pos; the earlier
889 // segments are already merged at this point.
890 while (I != SR.end() &&
892 (I->end == Pos && (ActiveMask & SR.LaneMask) == 0)))
896 if ((ActiveMask & SR.LaneMask) == 0 &&
897 Pos <= I->start && I->start <= NextPos) {
898 // Merge multiple begins at the same position.
899 if (I->start == NextPos && Event == BEGIN_SEGMENT) {
900 EventMask |= SR.LaneMask;
901 IsDef |= I->valno->def == I->start;
902 } else if (I->start < NextPos || Event != END_SEGMENT) {
903 Event = BEGIN_SEGMENT;
905 EventMask = SR.LaneMask;
906 IsDef = I->valno->def == I->start;
909 if ((ActiveMask & SR.LaneMask) != 0 &&
910 Pos <= I->end && I->end <= NextPos) {
911 // Merge multiple ends at the same position.
912 if (I->end == NextPos && Event == END_SEGMENT)
913 EventMask |= SR.LaneMask;
917 EventMask = SR.LaneMask;
922 // Advance scan position.
924 if (Event == BEGIN_SEGMENT) {
925 if (ConstructingSegment && IsDef) {
926 // Finish previous segment because we have to start a new one.
927 CurrentSegment.end = Pos;
928 append(CurrentSegment);
929 ConstructingSegment = false;
932 // Start a new segment if necessary.
933 if (!ConstructingSegment) {
934 // Determine value number for the segment.
937 VNI = getNextValue(Pos, VNIAllocator);
939 // We have to reuse an existing value number, if we are lucky
940 // then we already passed one of the predecessor blocks and determined
941 // its value number (with blocks in reverse postorder this would be
942 // always true but we have no such guarantee).
943 assert(Pos.isBlock());
944 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Pos);
945 // See if any of the predecessor blocks has a lower number and a VNI
946 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
947 SlotIndex PredEnd = Indexes.getMBBEndIdx(Pred);
948 VNI = getVNInfoBefore(PredEnd);
952 // Def will come later: We have to do an extra fixup pass.
957 CurrentSegment.start = Pos;
958 CurrentSegment.valno = VNI;
959 ConstructingSegment = true;
961 ActiveMask |= EventMask;
962 } else if (Event == END_SEGMENT) {
963 assert(ConstructingSegment);
964 // Finish segment if no lane is active anymore.
965 ActiveMask &= ~EventMask;
966 if (ActiveMask == 0) {
967 CurrentSegment.end = Pos;
968 append(CurrentSegment);
969 ConstructingSegment = false;
972 // We reached the end of the last subranges and can stop.
973 assert(Event == NOTHING);
978 // We might not be able to assign new valnos for all segments if the basic
979 // block containing the definition comes after a segment using the valno.
980 // Do a fixup pass for this uncommon case.
982 determineMissingVNIs(Indexes, *this);
984 assert(ActiveMask == 0 && !ConstructingSegment && "all segments ended");
988 unsigned LiveInterval::getSize() const {
990 for (const Segment &S : segments)
991 Sum += S.start.distance(S.end);
995 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
996 return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ")";
999 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1000 void LiveRange::Segment::dump() const {
1001 dbgs() << *this << "\n";
1005 void LiveRange::print(raw_ostream &OS) const {
1009 for (const Segment &S : segments) {
1011 assert(S.valno == getValNumInfo(S.valno->id) && "Bad VNInfo");
1015 // Print value number info.
1016 if (getNumValNums()) {
1019 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
1021 const VNInfo *vni = *i;
1022 if (vnum) OS << " ";
1024 if (vni->isUnused()) {
1028 if (vni->isPHIDef())
1035 void LiveInterval::print(raw_ostream &OS) const {
1036 OS << PrintReg(reg) << ' ';
1039 for (const SubRange &SR : subranges()) {
1040 OS << format(" L%04X ", SR.LaneMask) << SR;
1044 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1045 void LiveRange::dump() const {
1046 dbgs() << *this << "\n";
1049 void LiveInterval::dump() const {
1050 dbgs() << *this << "\n";
1055 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);
1071 void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
1074 // Make sure SubRanges are fine and LaneMasks are disjunct.
1076 unsigned MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg) : ~0u;
1077 for (const SubRange &SR : subranges()) {
1078 // Subrange lanemask should be disjunct to any previous subrange masks.
1079 assert((Mask & SR.LaneMask) == 0);
1080 Mask |= SR.LaneMask;
1082 // subrange mask should not contained in maximum lane mask for the vreg.
1083 assert((Mask & ~MaxMask) == 0);
1086 // Main liverange should cover subrange.
1093 //===----------------------------------------------------------------------===//
1094 // LiveRangeUpdater class
1095 //===----------------------------------------------------------------------===//
1097 // The LiveRangeUpdater class always maintains these invariants:
1099 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
1100 // This is the initial state, and the state created by flush().
1101 // In this state, isDirty() returns false.
1103 // Otherwise, segments are kept in three separate areas:
1105 // 1. [begin; WriteI) at the front of LR.
1106 // 2. [ReadI; end) at the back of LR.
1109 // - LR.begin() <= WriteI <= ReadI <= LR.end().
1110 // - Segments in all three areas are fully ordered and coalesced.
1111 // - Segments in area 1 precede and can't coalesce with segments in area 2.
1112 // - Segments in Spills precede and can't coalesce with segments in area 2.
1113 // - No coalescing is possible between segments in Spills and segments in area
1114 // 1, and there are no overlapping segments.
1116 // The segments in Spills are not ordered with respect to the segments in area
1117 // 1. They need to be merged.
1119 // When they exist, Spills.back().start <= LastStart,
1120 // and WriteI[-1].start <= LastStart.
1122 void LiveRangeUpdater::print(raw_ostream &OS) const {
1125 OS << "Clean updater: " << *LR << '\n';
1127 OS << "Null updater.\n";
1130 assert(LR && "Can't have null LR in dirty updater.");
1131 OS << " updater with gap = " << (ReadI - WriteI)
1132 << ", last start = " << LastStart
1134 for (const auto &S : make_range(LR->begin(), WriteI))
1137 for (unsigned I = 0, E = Spills.size(); I != E; ++I)
1138 OS << ' ' << Spills[I];
1140 for (const auto &S : make_range(ReadI, LR->end()))
1145 void LiveRangeUpdater::dump() const
1150 // Determine if A and B should be coalesced.
1151 static inline bool coalescable(const LiveRange::Segment &A,
1152 const LiveRange::Segment &B) {
1153 assert(A.start <= B.start && "Unordered live segments.");
1154 if (A.end == B.start)
1155 return A.valno == B.valno;
1156 if (A.end < B.start)
1158 assert(A.valno == B.valno && "Cannot overlap different values");
1162 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
1163 assert(LR && "Cannot add to a null destination");
1165 // Fall back to the regular add method if the live range
1166 // is using the segment set instead of the segment vector.
1167 if (LR->segmentSet != nullptr) {
1168 LR->addSegmentToSet(Seg);
1172 // Flush the state if Start moves backwards.
1173 if (!LastStart.isValid() || LastStart > Seg.start) {
1176 // This brings us to an uninitialized state. Reinitialize.
1177 assert(Spills.empty() && "Leftover spilled segments");
1178 WriteI = ReadI = LR->begin();
1181 // Remember start for next time.
1182 LastStart = Seg.start;
1184 // Advance ReadI until it ends after Seg.start.
1185 LiveRange::iterator E = LR->end();
1186 if (ReadI != E && ReadI->end <= Seg.start) {
1187 // First try to close the gap between WriteI and ReadI with spills.
1188 if (ReadI != WriteI)
1190 // Then advance ReadI.
1191 if (ReadI == WriteI)
1192 ReadI = WriteI = LR->find(Seg.start);
1194 while (ReadI != E && ReadI->end <= Seg.start)
1195 *WriteI++ = *ReadI++;
1198 assert(ReadI == E || ReadI->end > Seg.start);
1200 // Check if the ReadI segment begins early.
1201 if (ReadI != E && ReadI->start <= Seg.start) {
1202 assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
1203 // Bail if Seg is completely contained in ReadI.
1204 if (ReadI->end >= Seg.end)
1206 // Coalesce into Seg.
1207 Seg.start = ReadI->start;
1211 // Coalesce as much as possible from ReadI into Seg.
1212 while (ReadI != E && coalescable(Seg, *ReadI)) {
1213 Seg.end = std::max(Seg.end, ReadI->end);
1217 // Try coalescing Spills.back() into Seg.
1218 if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
1219 Seg.start = Spills.back().start;
1220 Seg.end = std::max(Spills.back().end, Seg.end);
1224 // Try coalescing Seg into WriteI[-1].
1225 if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
1226 WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
1230 // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
1231 if (WriteI != ReadI) {
1236 // Finally, append to LR or Spills.
1238 LR->segments.push_back(Seg);
1239 WriteI = ReadI = LR->end();
1241 Spills.push_back(Seg);
1244 // Merge as many spilled segments as possible into the gap between WriteI
1245 // and ReadI. Advance WriteI to reflect the inserted instructions.
1246 void LiveRangeUpdater::mergeSpills() {
1247 // Perform a backwards merge of Spills and [SpillI;WriteI).
1248 size_t GapSize = ReadI - WriteI;
1249 size_t NumMoved = std::min(Spills.size(), GapSize);
1250 LiveRange::iterator Src = WriteI;
1251 LiveRange::iterator Dst = Src + NumMoved;
1252 LiveRange::iterator SpillSrc = Spills.end();
1253 LiveRange::iterator B = LR->begin();
1255 // This is the new WriteI position after merging spills.
1258 // Now merge Src and Spills backwards.
1259 while (Src != Dst) {
1260 if (Src != B && Src[-1].start > SpillSrc[-1].start)
1263 *--Dst = *--SpillSrc;
1265 assert(NumMoved == size_t(Spills.end() - SpillSrc));
1266 Spills.erase(SpillSrc, Spills.end());
1269 void LiveRangeUpdater::flush() {
1272 // Clear the dirty state.
1273 LastStart = SlotIndex();
1275 assert(LR && "Cannot add to a null destination");
1277 // Nothing to merge?
1278 if (Spills.empty()) {
1279 LR->segments.erase(WriteI, ReadI);
1284 // Resize the WriteI - ReadI gap to match Spills.
1285 size_t GapSize = ReadI - WriteI;
1286 if (GapSize < Spills.size()) {
1287 // The gap is too small. Make some room.
1288 size_t WritePos = WriteI - LR->begin();
1289 LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
1290 // This also invalidated ReadI, but it is recomputed below.
1291 WriteI = LR->begin() + WritePos;
1293 // Shrink the gap if necessary.
1294 LR->segments.erase(WriteI + Spills.size(), ReadI);
1296 ReadI = WriteI + Spills.size();
1301 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
1302 // Create initial equivalence classes.
1304 EqClass.grow(LI->getNumValNums());
1306 const VNInfo *used = nullptr, *unused = nullptr;
1308 // Determine connections.
1309 for (const VNInfo *VNI : LI->valnos) {
1310 // Group all unused values into one class.
1311 if (VNI->isUnused()) {
1313 EqClass.join(unused->id, VNI->id);
1318 if (VNI->isPHIDef()) {
1319 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
1320 assert(MBB && "Phi-def has no defining MBB");
1321 // Connect to values live out of predecessors.
1322 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
1323 PE = MBB->pred_end(); PI != PE; ++PI)
1324 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
1325 EqClass.join(VNI->id, PVNI->id);
1327 // Normal value defined by an instruction. Check for two-addr redef.
1328 // FIXME: This could be coincidental. Should we really check for a tied
1329 // operand constraint?
1330 // Note that VNI->def may be a use slot for an early clobber def.
1331 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
1332 EqClass.join(VNI->id, UVNI->id);
1336 // Lump all the unused values in with the last used value.
1338 EqClass.join(used->id, unused->id);
1341 return EqClass.getNumClasses();
1344 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
1345 MachineRegisterInfo &MRI) {
1346 assert(LIV[0] && "LIV[0] must be set");
1347 LiveInterval &LI = *LIV[0];
1349 // Rewrite instructions.
1350 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
1351 RE = MRI.reg_end(); RI != RE;) {
1352 MachineOperand &MO = *RI;
1353 MachineInstr *MI = RI->getParent();
1355 // DBG_VALUE instructions don't have slot indexes, so get the index of the
1356 // instruction before them.
1357 // Normally, DBG_VALUE instructions are removed before this function is
1358 // called, but it is not a requirement.
1360 if (MI->isDebugValue())
1361 Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
1363 Idx = LIS.getInstructionIndex(MI);
1364 LiveQueryResult LRQ = LI.Query(Idx);
1365 const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
1366 // In the case of an <undef> use that isn't tied to any def, VNI will be
1367 // NULL. If the use is tied to a def, VNI will be the defined value.
1370 MO.setReg(LIV[getEqClass(VNI)]->reg);
1373 // Move runs to new intervals.
1374 LiveInterval::iterator J = LI.begin(), E = LI.end();
1375 while (J != E && EqClass[J->valno->id] == 0)
1377 for (LiveInterval::iterator I = J; I != E; ++I) {
1378 if (unsigned eq = EqClass[I->valno->id]) {
1379 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
1380 "New intervals should be empty");
1381 LIV[eq]->segments.push_back(*I);
1385 // TODO: do not cheat anymore by simply cleaning all subranges
1386 LI.clearSubRanges();
1387 LI.segments.erase(J, E);
1389 // Transfer VNInfos to their new owners and renumber them.
1390 unsigned j = 0, e = LI.getNumValNums();
1391 while (j != e && EqClass[j] == 0)
1393 for (unsigned i = j; i != e; ++i) {
1394 VNInfo *VNI = LI.getValNumInfo(i);
1395 if (unsigned eq = EqClass[i]) {
1396 VNI->id = LIV[eq]->getNumValNums();
1397 LIV[eq]->valnos.push_back(VNI);
1400 LI.valnos[j++] = VNI;
1403 LI.valnos.resize(j);