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 LiveRange::iterator LiveRange::find(SlotIndex Pos) {
36 // This algorithm is basically std::upper_bound.
37 // Unfortunately, std::upper_bound cannot be used with mixed types until we
38 // adopt C++0x. Many libraries can do it, but not all.
39 if (empty() || Pos >= endIndex())
44 size_t Mid = Len >> 1;
48 I += Mid + 1, Len -= Mid + 1;
53 VNInfo *LiveRange::createDeadDef(SlotIndex Def,
54 VNInfo::Allocator &VNInfoAllocator) {
55 assert(!Def.isDead() && "Cannot define a value at the dead slot");
56 iterator I = find(Def);
58 VNInfo *VNI = getNextValue(Def, VNInfoAllocator);
59 segments.push_back(Segment(Def, Def.getDeadSlot(), VNI));
62 if (SlotIndex::isSameInstr(Def, I->start)) {
63 assert(I->valno->def == I->start && "Inconsistent existing value def");
65 // It is possible to have both normal and early-clobber defs of the same
66 // register on an instruction. It doesn't make a lot of sense, but it is
67 // possible to specify in inline assembly.
69 // Just convert everything to early-clobber.
70 Def = std::min(Def, I->start);
72 I->start = I->valno->def = Def;
75 assert(SlotIndex::isEarlierInstr(Def, I->start) && "Already live at def");
76 VNInfo *VNI = getNextValue(Def, VNInfoAllocator);
77 segments.insert(I, Segment(Def, Def.getDeadSlot(), VNI));
81 // overlaps - Return true if the intersection of the two live ranges is
84 // An example for overlaps():
88 // 8: C = A + B ;; last use of A
90 // The live ranges should look like:
96 // A->overlaps(C) should return false since we want to be able to join
99 bool LiveRange::overlapsFrom(const LiveRange& other,
100 const_iterator StartPos) const {
101 assert(!empty() && "empty range");
102 const_iterator i = begin();
103 const_iterator ie = end();
104 const_iterator j = StartPos;
105 const_iterator je = other.end();
107 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
108 StartPos != other.end() && "Bogus start position hint!");
110 if (i->start < j->start) {
111 i = std::upper_bound(i, ie, j->start);
112 if (i != begin()) --i;
113 } else if (j->start < i->start) {
115 if (StartPos != other.end() && StartPos->start <= i->start) {
116 assert(StartPos < other.end() && i < end());
117 j = std::upper_bound(j, je, i->start);
118 if (j != other.begin()) --j;
124 if (j == je) return false;
127 if (i->start > j->start) {
132 if (i->end > j->start)
140 bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
141 const SlotIndexes &Indexes) const {
142 assert(!empty() && "empty range");
146 // Use binary searches to find initial positions.
147 const_iterator I = find(Other.beginIndex());
148 const_iterator IE = end();
151 const_iterator J = Other.find(I->start);
152 const_iterator JE = Other.end();
157 // J has just been advanced to satisfy:
158 assert(J->end >= I->start);
159 // Check for an overlap.
160 if (J->start < I->end) {
161 // I and J are overlapping. Find the later start.
162 SlotIndex Def = std::max(I->start, J->start);
163 // Allow the overlap if Def is a coalescable copy.
165 !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
168 // Advance the iterator that ends first to check for more overlaps.
169 if (J->end > I->end) {
173 // Advance J until J->end >= I->start.
177 while (J->end < I->start);
181 /// overlaps - Return true if the live range overlaps an interval specified
183 bool LiveRange::overlaps(SlotIndex Start, SlotIndex End) const {
184 assert(Start < End && "Invalid range");
185 const_iterator I = std::lower_bound(begin(), end(), End);
186 return I != begin() && (--I)->end > Start;
189 bool LiveRange::covers(const LiveRange &Other) const {
191 return Other.empty();
193 const_iterator I = begin();
194 for (const Segment &O : Other.segments) {
195 I = advanceTo(I, O.start);
196 if (I == end() || I->start > O.start)
199 // Check adjacent live segments and see if we can get behind O.end.
200 while (I->end < O.end) {
201 const_iterator Last = I;
202 // Get next segment and abort if it was not adjacent.
204 if (I == end() || Last->end != I->start)
211 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
212 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
213 /// it can be nuked later.
214 void LiveRange::markValNoForDeletion(VNInfo *ValNo) {
215 if (ValNo->id == getNumValNums()-1) {
218 } while (!valnos.empty() && valnos.back()->isUnused());
224 /// RenumberValues - Renumber all values in order of appearance and delete the
225 /// remaining unused values.
226 void LiveRange::RenumberValues() {
227 SmallPtrSet<VNInfo*, 8> Seen;
229 for (const Segment &S : segments) {
230 VNInfo *VNI = S.valno;
231 if (!Seen.insert(VNI).second)
233 assert(!VNI->isUnused() && "Unused valno used by live segment");
234 VNI->id = (unsigned)valnos.size();
235 valnos.push_back(VNI);
239 /// This method is used when we want to extend the segment specified by I to end
240 /// at the specified endpoint. To do this, we should merge and eliminate all
241 /// segments that this will overlap with. The iterator is not invalidated.
242 void LiveRange::extendSegmentEndTo(iterator I, SlotIndex NewEnd) {
243 assert(I != end() && "Not a valid segment!");
244 VNInfo *ValNo = I->valno;
246 // Search for the first segment that we can't merge with.
247 iterator MergeTo = std::next(I);
248 for (; MergeTo != end() && NewEnd >= MergeTo->end; ++MergeTo) {
249 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
252 // If NewEnd was in the middle of a segment, make sure to get its endpoint.
253 I->end = std::max(NewEnd, std::prev(MergeTo)->end);
255 // If the newly formed segment now touches the segment after it and if they
256 // have the same value number, merge the two segments into one segment.
257 if (MergeTo != end() && MergeTo->start <= I->end &&
258 MergeTo->valno == ValNo) {
259 I->end = MergeTo->end;
263 // Erase any dead segments.
264 segments.erase(std::next(I), MergeTo);
268 /// This method is used when we want to extend the segment specified by I to
269 /// start at the specified endpoint. To do this, we should merge and eliminate
270 /// all segments that this will overlap with.
272 LiveRange::extendSegmentStartTo(iterator I, SlotIndex NewStart) {
273 assert(I != end() && "Not a valid segment!");
274 VNInfo *ValNo = I->valno;
276 // Search for the first segment that we can't merge with.
277 iterator MergeTo = I;
279 if (MergeTo == begin()) {
281 segments.erase(MergeTo, I);
284 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
286 } while (NewStart <= MergeTo->start);
288 // If we start in the middle of another segment, just delete a range and
289 // extend that segment.
290 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
291 MergeTo->end = I->end;
293 // Otherwise, extend the segment right after.
295 MergeTo->start = NewStart;
296 MergeTo->end = I->end;
299 segments.erase(std::next(MergeTo), std::next(I));
303 void LiveRange::append(const Segment S) {
304 // Check that the segment belongs to the back of the list.
305 assert(segments.empty() || segments.back().end <= S.start);
306 segments.push_back(S);
309 LiveRange::iterator LiveRange::addSegmentFrom(Segment S, iterator From) {
310 SlotIndex Start = S.start, End = S.end;
311 iterator it = std::upper_bound(From, end(), Start);
313 // If the inserted segment starts in the middle or right at the end of
314 // another segment, just extend that segment to contain the segment of S.
316 iterator B = std::prev(it);
317 if (S.valno == B->valno) {
318 if (B->start <= Start && B->end >= Start) {
319 extendSegmentEndTo(B, End);
323 // Check to make sure that we are not overlapping two live segments with
324 // different valno's.
325 assert(B->end <= Start &&
326 "Cannot overlap two segments with differing ValID's"
327 " (did you def the same reg twice in a MachineInstr?)");
331 // Otherwise, if this segment ends in the middle of, or right next to, another
332 // segment, merge it into that segment.
334 if (S.valno == it->valno) {
335 if (it->start <= End) {
336 it = extendSegmentStartTo(it, Start);
338 // If S is a complete superset of a segment, we may need to grow its
341 extendSegmentEndTo(it, End);
345 // Check to make sure that we are not overlapping two live segments with
346 // different valno's.
347 assert(it->start >= End &&
348 "Cannot overlap two segments with differing ValID's");
352 // Otherwise, this is just a new segment that doesn't interact with anything.
354 return segments.insert(it, S);
357 /// extendInBlock - If this range is live before Kill in the basic
358 /// block that starts at StartIdx, extend it to be live up to Kill and return
359 /// the value. If there is no live range before Kill, return NULL.
360 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
363 iterator I = std::upper_bound(begin(), end(), Kill.getPrevSlot());
367 if (I->end <= StartIdx)
370 extendSegmentEndTo(I, Kill);
374 /// Remove the specified segment from this range. Note that the segment must
375 /// be in a single Segment in its entirety.
376 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
377 bool RemoveDeadValNo) {
378 // Find the Segment containing this span.
379 iterator I = find(Start);
380 assert(I != end() && "Segment is not in range!");
381 assert(I->containsInterval(Start, End)
382 && "Segment is not entirely in range!");
384 // If the span we are removing is at the start of the Segment, adjust it.
385 VNInfo *ValNo = I->valno;
386 if (I->start == Start) {
388 if (RemoveDeadValNo) {
389 // Check if val# is dead.
391 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
392 if (II != I && II->valno == ValNo) {
397 // Now that ValNo is dead, remove it.
398 markValNoForDeletion(ValNo);
402 segments.erase(I); // Removed the whole Segment.
408 // Otherwise if the span we are removing is at the end of the Segment,
409 // adjust the other way.
415 // Otherwise, we are splitting the Segment into two pieces.
416 SlotIndex OldEnd = I->end;
417 I->end = Start; // Trim the old segment.
419 // Insert the new one.
420 segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
423 /// removeValNo - Remove all the segments defined by the specified value#.
424 /// Also remove the value# from value# list.
425 void LiveRange::removeValNo(VNInfo *ValNo) {
428 iterator E = begin();
431 if (I->valno == ValNo)
434 // Now that ValNo is dead, remove it.
435 markValNoForDeletion(ValNo);
438 void LiveRange::join(LiveRange &Other,
439 const int *LHSValNoAssignments,
440 const int *RHSValNoAssignments,
441 SmallVectorImpl<VNInfo *> &NewVNInfo) {
444 // Determine if any of our values are mapped. This is uncommon, so we want
445 // to avoid the range scan if not.
446 bool MustMapCurValNos = false;
447 unsigned NumVals = getNumValNums();
448 unsigned NumNewVals = NewVNInfo.size();
449 for (unsigned i = 0; i != NumVals; ++i) {
450 unsigned LHSValID = LHSValNoAssignments[i];
452 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
453 MustMapCurValNos = true;
458 // If we have to apply a mapping to our base range assignment, rewrite it now.
459 if (MustMapCurValNos && !empty()) {
460 // Map the first live range.
462 iterator OutIt = begin();
463 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
464 for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
465 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
466 assert(nextValNo && "Huh?");
468 // If this live range has the same value # as its immediate predecessor,
469 // and if they are neighbors, remove one Segment. This happens when we
470 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
471 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
474 // Didn't merge. Move OutIt to the next segment,
476 OutIt->valno = nextValNo;
478 OutIt->start = I->start;
483 // If we merge some segments, chop off the end.
485 segments.erase(OutIt, end());
488 // Rewrite Other values before changing the VNInfo ids.
489 // This can leave Other in an invalid state because we're not coalescing
490 // touching segments that now have identical values. That's OK since Other is
491 // not supposed to be valid after calling join();
492 for (Segment &S : Other.segments)
493 S.valno = NewVNInfo[RHSValNoAssignments[S.valno->id]];
495 // Update val# info. Renumber them and make sure they all belong to this
496 // LiveRange now. Also remove dead val#'s.
497 unsigned NumValNos = 0;
498 for (unsigned i = 0; i < NumNewVals; ++i) {
499 VNInfo *VNI = NewVNInfo[i];
501 if (NumValNos >= NumVals)
502 valnos.push_back(VNI);
504 valnos[NumValNos] = VNI;
505 VNI->id = NumValNos++; // Renumber val#.
508 if (NumNewVals < NumVals)
509 valnos.resize(NumNewVals); // shrinkify
511 // Okay, now insert the RHS live segments into the LHS.
512 LiveRangeUpdater Updater(this);
513 for (Segment &S : Other.segments)
517 /// Merge all of the segments in RHS into this live range as the specified
518 /// value number. The segments in RHS are allowed to overlap with segments in
519 /// the current range, but only if the overlapping segments have the
520 /// specified value number.
521 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
523 LiveRangeUpdater Updater(this);
524 for (const Segment &S : RHS.segments)
525 Updater.add(S.start, S.end, LHSValNo);
528 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
529 /// in RHS into this live range as the specified value number.
530 /// The segments in RHS are allowed to overlap with segments in the
531 /// current range, it will replace the value numbers of the overlaped
532 /// segments with the specified value number.
533 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
534 const VNInfo *RHSValNo,
536 LiveRangeUpdater Updater(this);
537 for (const Segment &S : RHS.segments)
538 if (S.valno == RHSValNo)
539 Updater.add(S.start, S.end, LHSValNo);
542 /// MergeValueNumberInto - This method is called when two value nubmers
543 /// are found to be equivalent. This eliminates V1, replacing all
544 /// segments with the V1 value number with the V2 value number. This can
545 /// cause merging of V1/V2 values numbers and compaction of the value space.
546 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
547 assert(V1 != V2 && "Identical value#'s are always equivalent!");
549 // This code actually merges the (numerically) larger value number into the
550 // smaller value number, which is likely to allow us to compactify the value
551 // space. The only thing we have to be careful of is to preserve the
552 // instruction that defines the result value.
554 // Make sure V2 is smaller than V1.
555 if (V1->id < V2->id) {
560 // Merge V1 segments into V2.
561 for (iterator I = begin(); I != end(); ) {
563 if (S->valno != V1) continue; // Not a V1 Segment.
565 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
569 if (Prev->valno == V2 && Prev->end == S->start) {
572 // Erase this live-range.
579 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
580 // Ensure that it is a V2 live-range.
583 // If we can merge it into later V2 segments, do so now. We ignore any
584 // following V1 segments, as they will be merged in subsequent iterations
587 if (I->start == S->end && I->valno == V2) {
595 // Now that V1 is dead, remove it.
596 markValNoForDeletion(V1);
601 void LiveInterval::removeEmptySubRanges() {
602 SubRange **NextPtr = &SubRanges;
603 SubRange *I = *NextPtr;
604 while (I != nullptr) {
610 // Skip empty subranges until we find the first nonempty one.
613 } while (I != nullptr && I->empty());
618 /// Helper function for constructMainRangeFromSubranges(): Search the CFG
619 /// backwards until we find a place covered by a LiveRange segment that actually
621 static VNInfo *searchForVNI(const SlotIndexes &Indexes, LiveRange &LR,
622 const MachineBasicBlock *MBB,
623 SmallPtrSetImpl<const MachineBasicBlock*> &Visited) {
624 // We start the search at the end of MBB.
625 SlotIndex EndIdx = Indexes.getMBBEndIdx(MBB);
626 // In our use case we can't live the area covered by the live segments without
627 // finding an actual VNI def.
628 LiveRange::iterator I = LR.find(EndIdx.getPrevSlot());
629 assert(I != LR.end());
630 LiveRange::Segment &S = *I;
631 if (S.valno != nullptr)
634 VNInfo *VNI = nullptr;
635 // Continue at predecessors (we could even go to idom with domtree available).
636 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
637 // Avoid going in circles.
638 if (Visited.count(Pred))
640 Visited.insert(Pred);
642 VNI = searchForVNI(Indexes, LR, Pred, Visited);
643 if (VNI != nullptr) {
652 void LiveInterval::constructMainRangeFromSubranges(
653 const SlotIndexes &Indexes, VNInfo::Allocator &VNIAllocator) {
654 // The basic observations on which this algorithm is based:
655 // - Each Def/ValNo in a subrange must have a corresponding def on the main
656 // range, but not further defs/valnos are necessary.
657 // - If any of the subranges is live at a point the main liverange has to be
658 // live too, conversily if no subrange is live the main range mustn't be
660 // We do this by scannig through all the subranges simultaneously creating new
661 // segments in the main range as segments start/ends come up in the subranges.
662 assert(hasSubRanges());
663 assert(segments.empty() && valnos.empty() && "expected empty main range");
665 // Collect subrange, iterator pairs for the walk and determine first and last
666 // SlotIndex involved.
667 SmallVector<std::pair<const SubRange*, const_iterator>, 4> SRs;
670 for (const SubRange &SR : subranges()) {
673 SRs.push_back(std::make_pair(&SR, SR.begin()));
674 if (!First.isValid() || SR.segments.front().start < First)
675 First = SR.segments.front().start;
676 if (!Last.isValid() || SR.segments.back().end > Last)
677 Last = SR.segments.back().end;
680 // Walk over all subranges simultaneously.
681 Segment CurrentSegment;
682 bool ConstructingSegment = false;
683 bool NeedVNIFixup = false;
684 unsigned ActiveMask = 0;
685 SlotIndex Pos = First;
687 SlotIndex NextPos = Last;
693 unsigned EventMask = 0;
695 // Find the next begin or end of a subrange segment. Combine masks if we
696 // have multiple begins/ends at the same position. Ends take precedence over
698 for (auto &SRP : SRs) {
699 const SubRange &SR = *SRP.first;
700 const_iterator &I = SRP.second;
701 while (I != SR.end() &&
703 (I->end == Pos && (ActiveMask & SR.LaneMask) == 0)))
707 if ((ActiveMask & SR.LaneMask) == 0 &&
708 Pos <= I->start && I->start <= NextPos) {
709 // Merge multiple begins at the same position
710 if (I->start == NextPos && Event == BEGIN_SEGMENT) {
711 EventMask |= SR.LaneMask;
712 IsDef |= I->valno->def == I->start;
713 } else if (I->start < NextPos || Event != END_SEGMENT) {
714 Event = BEGIN_SEGMENT;
716 EventMask = SR.LaneMask;
717 IsDef = I->valno->def == I->start;
720 if ((ActiveMask & SR.LaneMask) != 0 &&
721 Pos <= I->end && I->end <= NextPos) {
722 // Merge multiple ends at the same position.
723 if (I->end == NextPos && Event == END_SEGMENT)
724 EventMask |= SR.LaneMask;
728 EventMask = SR.LaneMask;
733 // Advance scan position.
735 if (Event == BEGIN_SEGMENT) {
736 if (ConstructingSegment && IsDef) {
737 // Finish previous segment because we have to start a new one.
738 CurrentSegment.end = Pos;
739 append(CurrentSegment);
740 ConstructingSegment = false;
743 // Start a new segment if necessary.
744 if (!ConstructingSegment) {
745 // Determine value number for the segment.
748 VNI = getNextValue(Pos, VNIAllocator);
750 // We have to reuse an existing value number, if we are lucky
751 // then we already passed one of the predecessor blocks and determined
752 // its value number (with blocks in reverse postorder this would be
753 // always true but we have no such guarantee).
754 assert(Pos.isBlock());
755 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Pos);
756 // See if any of the predecessor blocks has a lower number and a VNI
757 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
758 SlotIndex PredEnd = Indexes.getMBBEndIdx(Pred);
759 VNI = getVNInfoBefore(PredEnd);
763 // Def will come later: We have to do an extra fixup pass.
768 CurrentSegment.start = Pos;
769 CurrentSegment.valno = VNI;
770 ConstructingSegment = true;
772 ActiveMask |= EventMask;
773 } else if (Event == END_SEGMENT) {
774 assert(ConstructingSegment);
775 // Finish segment if no lane is active anymore.
776 ActiveMask &= ~EventMask;
777 if (ActiveMask == 0) {
778 CurrentSegment.end = Pos;
779 append(CurrentSegment);
780 ConstructingSegment = false;
783 // We reached the end of the last subranges and can stop.
784 assert(Event == NOTHING);
789 // We might not be able to assign new valnos for all segments if the basic
790 // block containing the definition comes after a segment using the valno.
791 // Do a fixup pass for this uncommon case.
793 SmallPtrSet<const MachineBasicBlock*, 5> Visited;
794 for (Segment &S : segments) {
795 if (S.valno != nullptr)
797 // This can only happen at the begin of a basic block.
798 assert(S.start.isBlock());
801 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
802 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
803 VNInfo *VNI = searchForVNI(Indexes, *this, Pred, Visited);
804 if (VNI != nullptr) {
809 assert(S.valno != nullptr);
812 assert(ActiveMask == 0 && !ConstructingSegment);
816 unsigned LiveInterval::getSize() const {
818 for (const Segment &S : segments)
819 Sum += S.start.distance(S.end);
823 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
824 return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ")";
827 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
828 void LiveRange::Segment::dump() const {
829 dbgs() << *this << "\n";
833 void LiveRange::print(raw_ostream &OS) const {
837 for (const Segment &S : segments) {
839 assert(S.valno == getValNumInfo(S.valno->id) && "Bad VNInfo");
843 // Print value number info.
844 if (getNumValNums()) {
847 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
849 const VNInfo *vni = *i;
852 if (vni->isUnused()) {
863 void LiveInterval::print(raw_ostream &OS) const {
864 OS << PrintReg(reg) << ' ';
867 for (const SubRange &SR : subranges()) {
868 OS << format(" L%04X ", SR.LaneMask) << SR;
872 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
873 void LiveRange::dump() const {
874 dbgs() << *this << "\n";
877 void LiveInterval::dump() const {
878 dbgs() << *this << "\n";
883 void LiveRange::verify() const {
884 for (const_iterator I = begin(), E = end(); I != E; ++I) {
885 assert(I->start.isValid());
886 assert(I->end.isValid());
887 assert(I->start < I->end);
888 assert(I->valno != nullptr);
889 assert(I->valno->id < valnos.size());
890 assert(I->valno == valnos[I->valno->id]);
891 if (std::next(I) != E) {
892 assert(I->end <= std::next(I)->start);
893 if (I->end == std::next(I)->start)
894 assert(I->valno != std::next(I)->valno);
899 void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
902 // Make sure SubRanges are fine and LaneMasks are disjunct.
904 unsigned MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg) : ~0u;
905 for (const SubRange &SR : subranges()) {
906 // Subrange lanemask should be disjunct to any previous subrange masks.
907 assert((Mask & SR.LaneMask) == 0);
910 // subrange mask should not contained in maximum lane mask for the vreg.
911 assert((Mask & ~MaxMask) == 0);
914 // Main liverange should cover subrange.
921 //===----------------------------------------------------------------------===//
922 // LiveRangeUpdater class
923 //===----------------------------------------------------------------------===//
925 // The LiveRangeUpdater class always maintains these invariants:
927 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
928 // This is the initial state, and the state created by flush().
929 // In this state, isDirty() returns false.
931 // Otherwise, segments are kept in three separate areas:
933 // 1. [begin; WriteI) at the front of LR.
934 // 2. [ReadI; end) at the back of LR.
937 // - LR.begin() <= WriteI <= ReadI <= LR.end().
938 // - Segments in all three areas are fully ordered and coalesced.
939 // - Segments in area 1 precede and can't coalesce with segments in area 2.
940 // - Segments in Spills precede and can't coalesce with segments in area 2.
941 // - No coalescing is possible between segments in Spills and segments in area
942 // 1, and there are no overlapping segments.
944 // The segments in Spills are not ordered with respect to the segments in area
945 // 1. They need to be merged.
947 // When they exist, Spills.back().start <= LastStart,
948 // and WriteI[-1].start <= LastStart.
950 void LiveRangeUpdater::print(raw_ostream &OS) const {
953 OS << "Clean updater: " << *LR << '\n';
955 OS << "Null updater.\n";
958 assert(LR && "Can't have null LR in dirty updater.");
959 OS << " updater with gap = " << (ReadI - WriteI)
960 << ", last start = " << LastStart
962 for (const auto &S : make_range(LR->begin(), WriteI))
965 for (unsigned I = 0, E = Spills.size(); I != E; ++I)
966 OS << ' ' << Spills[I];
968 for (const auto &S : make_range(ReadI, LR->end()))
973 void LiveRangeUpdater::dump() const
978 // Determine if A and B should be coalesced.
979 static inline bool coalescable(const LiveRange::Segment &A,
980 const LiveRange::Segment &B) {
981 assert(A.start <= B.start && "Unordered live segments.");
982 if (A.end == B.start)
983 return A.valno == B.valno;
986 assert(A.valno == B.valno && "Cannot overlap different values");
990 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
991 assert(LR && "Cannot add to a null destination");
993 // Flush the state if Start moves backwards.
994 if (!LastStart.isValid() || LastStart > Seg.start) {
997 // This brings us to an uninitialized state. Reinitialize.
998 assert(Spills.empty() && "Leftover spilled segments");
999 WriteI = ReadI = LR->begin();
1002 // Remember start for next time.
1003 LastStart = Seg.start;
1005 // Advance ReadI until it ends after Seg.start.
1006 LiveRange::iterator E = LR->end();
1007 if (ReadI != E && ReadI->end <= Seg.start) {
1008 // First try to close the gap between WriteI and ReadI with spills.
1009 if (ReadI != WriteI)
1011 // Then advance ReadI.
1012 if (ReadI == WriteI)
1013 ReadI = WriteI = LR->find(Seg.start);
1015 while (ReadI != E && ReadI->end <= Seg.start)
1016 *WriteI++ = *ReadI++;
1019 assert(ReadI == E || ReadI->end > Seg.start);
1021 // Check if the ReadI segment begins early.
1022 if (ReadI != E && ReadI->start <= Seg.start) {
1023 assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
1024 // Bail if Seg is completely contained in ReadI.
1025 if (ReadI->end >= Seg.end)
1027 // Coalesce into Seg.
1028 Seg.start = ReadI->start;
1032 // Coalesce as much as possible from ReadI into Seg.
1033 while (ReadI != E && coalescable(Seg, *ReadI)) {
1034 Seg.end = std::max(Seg.end, ReadI->end);
1038 // Try coalescing Spills.back() into Seg.
1039 if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
1040 Seg.start = Spills.back().start;
1041 Seg.end = std::max(Spills.back().end, Seg.end);
1045 // Try coalescing Seg into WriteI[-1].
1046 if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
1047 WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
1051 // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
1052 if (WriteI != ReadI) {
1057 // Finally, append to LR or Spills.
1059 LR->segments.push_back(Seg);
1060 WriteI = ReadI = LR->end();
1062 Spills.push_back(Seg);
1065 // Merge as many spilled segments as possible into the gap between WriteI
1066 // and ReadI. Advance WriteI to reflect the inserted instructions.
1067 void LiveRangeUpdater::mergeSpills() {
1068 // Perform a backwards merge of Spills and [SpillI;WriteI).
1069 size_t GapSize = ReadI - WriteI;
1070 size_t NumMoved = std::min(Spills.size(), GapSize);
1071 LiveRange::iterator Src = WriteI;
1072 LiveRange::iterator Dst = Src + NumMoved;
1073 LiveRange::iterator SpillSrc = Spills.end();
1074 LiveRange::iterator B = LR->begin();
1076 // This is the new WriteI position after merging spills.
1079 // Now merge Src and Spills backwards.
1080 while (Src != Dst) {
1081 if (Src != B && Src[-1].start > SpillSrc[-1].start)
1084 *--Dst = *--SpillSrc;
1086 assert(NumMoved == size_t(Spills.end() - SpillSrc));
1087 Spills.erase(SpillSrc, Spills.end());
1090 void LiveRangeUpdater::flush() {
1093 // Clear the dirty state.
1094 LastStart = SlotIndex();
1096 assert(LR && "Cannot add to a null destination");
1098 // Nothing to merge?
1099 if (Spills.empty()) {
1100 LR->segments.erase(WriteI, ReadI);
1105 // Resize the WriteI - ReadI gap to match Spills.
1106 size_t GapSize = ReadI - WriteI;
1107 if (GapSize < Spills.size()) {
1108 // The gap is too small. Make some room.
1109 size_t WritePos = WriteI - LR->begin();
1110 LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
1111 // This also invalidated ReadI, but it is recomputed below.
1112 WriteI = LR->begin() + WritePos;
1114 // Shrink the gap if necessary.
1115 LR->segments.erase(WriteI + Spills.size(), ReadI);
1117 ReadI = WriteI + Spills.size();
1122 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
1123 // Create initial equivalence classes.
1125 EqClass.grow(LI->getNumValNums());
1127 const VNInfo *used = nullptr, *unused = nullptr;
1129 // Determine connections.
1130 for (const VNInfo *VNI : LI->valnos) {
1131 // Group all unused values into one class.
1132 if (VNI->isUnused()) {
1134 EqClass.join(unused->id, VNI->id);
1139 if (VNI->isPHIDef()) {
1140 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
1141 assert(MBB && "Phi-def has no defining MBB");
1142 // Connect to values live out of predecessors.
1143 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
1144 PE = MBB->pred_end(); PI != PE; ++PI)
1145 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
1146 EqClass.join(VNI->id, PVNI->id);
1148 // Normal value defined by an instruction. Check for two-addr redef.
1149 // FIXME: This could be coincidental. Should we really check for a tied
1150 // operand constraint?
1151 // Note that VNI->def may be a use slot for an early clobber def.
1152 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
1153 EqClass.join(VNI->id, UVNI->id);
1157 // Lump all the unused values in with the last used value.
1159 EqClass.join(used->id, unused->id);
1162 return EqClass.getNumClasses();
1165 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
1166 MachineRegisterInfo &MRI) {
1167 assert(LIV[0] && "LIV[0] must be set");
1168 LiveInterval &LI = *LIV[0];
1170 // Rewrite instructions.
1171 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
1172 RE = MRI.reg_end(); RI != RE;) {
1173 MachineOperand &MO = *RI;
1174 MachineInstr *MI = RI->getParent();
1176 // DBG_VALUE instructions don't have slot indexes, so get the index of the
1177 // instruction before them.
1178 // Normally, DBG_VALUE instructions are removed before this function is
1179 // called, but it is not a requirement.
1181 if (MI->isDebugValue())
1182 Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
1184 Idx = LIS.getInstructionIndex(MI);
1185 LiveQueryResult LRQ = LI.Query(Idx);
1186 const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
1187 // In the case of an <undef> use that isn't tied to any def, VNI will be
1188 // NULL. If the use is tied to a def, VNI will be the defined value.
1191 MO.setReg(LIV[getEqClass(VNI)]->reg);
1194 // Move runs to new intervals.
1195 LiveInterval::iterator J = LI.begin(), E = LI.end();
1196 while (J != E && EqClass[J->valno->id] == 0)
1198 for (LiveInterval::iterator I = J; I != E; ++I) {
1199 if (unsigned eq = EqClass[I->valno->id]) {
1200 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
1201 "New intervals should be empty");
1202 LIV[eq]->segments.push_back(*I);
1206 // TODO: do not cheat anymore by simply cleaning all subranges
1207 LI.clearSubRanges();
1208 LI.segments.erase(J, E);
1210 // Transfer VNInfos to their new owners and renumber them.
1211 unsigned j = 0, e = LI.getNumValNums();
1212 while (j != e && EqClass[j] == 0)
1214 for (unsigned i = j; i != e; ++i) {
1215 VNInfo *VNI = LI.getValNumInfo(i);
1216 if (unsigned eq = EqClass[i]) {
1217 VNI->id = LIV[eq]->getNumValNums();
1218 LIV[eq]->valnos.push_back(VNI);
1221 LI.valnos[j++] = VNI;
1224 LI.valnos.resize(j);