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/raw_ostream.h"
30 #include "llvm/Target/TargetRegisterInfo.h"
34 LiveRange::iterator LiveRange::find(SlotIndex Pos) {
35 // This algorithm is basically std::upper_bound.
36 // Unfortunately, std::upper_bound cannot be used with mixed types until we
37 // adopt C++0x. Many libraries can do it, but not all.
38 if (empty() || Pos >= endIndex())
43 size_t Mid = Len >> 1;
47 I += Mid + 1, Len -= Mid + 1;
52 VNInfo *LiveRange::createDeadDef(SlotIndex Def,
53 VNInfo::Allocator &VNInfoAllocator) {
54 assert(!Def.isDead() && "Cannot define a value at the dead slot");
55 iterator I = find(Def);
57 VNInfo *VNI = getNextValue(Def, VNInfoAllocator);
58 segments.push_back(Segment(Def, Def.getDeadSlot(), VNI));
61 if (SlotIndex::isSameInstr(Def, I->start)) {
62 assert(I->valno->def == I->start && "Inconsistent existing value def");
64 // It is possible to have both normal and early-clobber defs of the same
65 // register on an instruction. It doesn't make a lot of sense, but it is
66 // possible to specify in inline assembly.
68 // Just convert everything to early-clobber.
69 Def = std::min(Def, I->start);
71 I->start = I->valno->def = Def;
74 assert(SlotIndex::isEarlierInstr(Def, I->start) && "Already live at def");
75 VNInfo *VNI = getNextValue(Def, VNInfoAllocator);
76 segments.insert(I, Segment(Def, Def.getDeadSlot(), VNI));
80 // overlaps - Return true if the intersection of the two live ranges is
83 // An example for overlaps():
87 // 8: C = A + B ;; last use of A
89 // The live ranges should look like:
95 // A->overlaps(C) should return false since we want to be able to join
98 bool LiveRange::overlapsFrom(const LiveRange& other,
99 const_iterator StartPos) const {
100 assert(!empty() && "empty range");
101 const_iterator i = begin();
102 const_iterator ie = end();
103 const_iterator j = StartPos;
104 const_iterator je = other.end();
106 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
107 StartPos != other.end() && "Bogus start position hint!");
109 if (i->start < j->start) {
110 i = std::upper_bound(i, ie, j->start);
111 if (i != begin()) --i;
112 } else if (j->start < i->start) {
114 if (StartPos != other.end() && StartPos->start <= i->start) {
115 assert(StartPos < other.end() && i < end());
116 j = std::upper_bound(j, je, i->start);
117 if (j != other.begin()) --j;
123 if (j == je) return false;
126 if (i->start > j->start) {
131 if (i->end > j->start)
139 bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
140 const SlotIndexes &Indexes) const {
141 assert(!empty() && "empty range");
145 // Use binary searches to find initial positions.
146 const_iterator I = find(Other.beginIndex());
147 const_iterator IE = end();
150 const_iterator J = Other.find(I->start);
151 const_iterator JE = Other.end();
156 // J has just been advanced to satisfy:
157 assert(J->end >= I->start);
158 // Check for an overlap.
159 if (J->start < I->end) {
160 // I and J are overlapping. Find the later start.
161 SlotIndex Def = std::max(I->start, J->start);
162 // Allow the overlap if Def is a coalescable copy.
164 !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
167 // Advance the iterator that ends first to check for more overlaps.
168 if (J->end > I->end) {
172 // Advance J until J->end >= I->start.
176 while (J->end < I->start);
180 /// overlaps - Return true if the live range overlaps an interval specified
182 bool LiveRange::overlaps(SlotIndex Start, SlotIndex End) const {
183 assert(Start < End && "Invalid range");
184 const_iterator I = std::lower_bound(begin(), end(), End);
185 return I != begin() && (--I)->end > Start;
188 bool LiveRange::covers(const LiveRange &Other) const {
190 return Other.empty();
192 const_iterator I = begin();
193 for (const_iterator O = Other.begin(), OE = Other.end(); O != OE; ++O) {
194 I = advanceTo(I, O->start);
195 if (I == end() || I->start > O->start)
198 // Check adjacent live segments and see if we can get behind O->end.
199 while (I->end < O->end) {
200 const_iterator Last = I;
201 // Get next segment and abort if it was not adjacent.
203 if (I == end() || Last->end != I->start)
210 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
211 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
212 /// it can be nuked later.
213 void LiveRange::markValNoForDeletion(VNInfo *ValNo) {
214 if (ValNo->id == getNumValNums()-1) {
217 } while (!valnos.empty() && valnos.back()->isUnused());
223 /// RenumberValues - Renumber all values in order of appearance and delete the
224 /// remaining unused values.
225 void LiveRange::RenumberValues() {
226 SmallPtrSet<VNInfo*, 8> Seen;
228 for (const_iterator I = begin(), E = end(); I != E; ++I) {
229 VNInfo *VNI = I->valno;
230 if (!Seen.insert(VNI).second)
232 assert(!VNI->isUnused() && "Unused valno used by live segment");
233 VNI->id = (unsigned)valnos.size();
234 valnos.push_back(VNI);
238 /// This method is used when we want to extend the segment specified by I to end
239 /// at the specified endpoint. To do this, we should merge and eliminate all
240 /// segments that this will overlap with. The iterator is not invalidated.
241 void LiveRange::extendSegmentEndTo(iterator I, SlotIndex NewEnd) {
242 assert(I != end() && "Not a valid segment!");
243 VNInfo *ValNo = I->valno;
245 // Search for the first segment that we can't merge with.
246 iterator MergeTo = std::next(I);
247 for (; MergeTo != end() && NewEnd >= MergeTo->end; ++MergeTo) {
248 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
251 // If NewEnd was in the middle of a segment, make sure to get its endpoint.
252 I->end = std::max(NewEnd, std::prev(MergeTo)->end);
254 // If the newly formed segment now touches the segment after it and if they
255 // have the same value number, merge the two segments into one segment.
256 if (MergeTo != end() && MergeTo->start <= I->end &&
257 MergeTo->valno == ValNo) {
258 I->end = MergeTo->end;
262 // Erase any dead segments.
263 segments.erase(std::next(I), MergeTo);
267 /// This method is used when we want to extend the segment specified by I to
268 /// start at the specified endpoint. To do this, we should merge and eliminate
269 /// all segments that this will overlap with.
271 LiveRange::extendSegmentStartTo(iterator I, SlotIndex NewStart) {
272 assert(I != end() && "Not a valid segment!");
273 VNInfo *ValNo = I->valno;
275 // Search for the first segment that we can't merge with.
276 iterator MergeTo = I;
278 if (MergeTo == begin()) {
280 segments.erase(MergeTo, I);
283 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
285 } while (NewStart <= MergeTo->start);
287 // If we start in the middle of another segment, just delete a range and
288 // extend that segment.
289 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
290 MergeTo->end = I->end;
292 // Otherwise, extend the segment right after.
294 MergeTo->start = NewStart;
295 MergeTo->end = I->end;
298 segments.erase(std::next(MergeTo), std::next(I));
302 LiveRange::iterator LiveRange::addSegmentFrom(Segment S, iterator From) {
303 SlotIndex Start = S.start, End = S.end;
304 iterator it = std::upper_bound(From, end(), Start);
306 // If the inserted segment starts in the middle or right at the end of
307 // another segment, just extend that segment to contain the segment of S.
309 iterator B = std::prev(it);
310 if (S.valno == B->valno) {
311 if (B->start <= Start && B->end >= Start) {
312 extendSegmentEndTo(B, End);
316 // Check to make sure that we are not overlapping two live segments with
317 // different valno's.
318 assert(B->end <= Start &&
319 "Cannot overlap two segments with differing ValID's"
320 " (did you def the same reg twice in a MachineInstr?)");
324 // Otherwise, if this segment ends in the middle of, or right next to, another
325 // segment, merge it into that segment.
327 if (S.valno == it->valno) {
328 if (it->start <= End) {
329 it = extendSegmentStartTo(it, Start);
331 // If S is a complete superset of a segment, we may need to grow its
334 extendSegmentEndTo(it, End);
338 // Check to make sure that we are not overlapping two live segments with
339 // different valno's.
340 assert(it->start >= End &&
341 "Cannot overlap two segments with differing ValID's");
345 // Otherwise, this is just a new segment that doesn't interact with anything.
347 return segments.insert(it, S);
350 /// extendInBlock - If this range is live before Kill in the basic
351 /// block that starts at StartIdx, extend it to be live up to Kill and return
352 /// the value. If there is no live range before Kill, return NULL.
353 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
356 iterator I = std::upper_bound(begin(), end(), Kill.getPrevSlot());
360 if (I->end <= StartIdx)
363 extendSegmentEndTo(I, Kill);
367 /// Remove the specified segment from this range. Note that the segment must
368 /// be in a single Segment in its entirety.
369 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
370 bool RemoveDeadValNo) {
371 // Find the Segment containing this span.
372 iterator I = find(Start);
373 assert(I != end() && "Segment is not in range!");
374 assert(I->containsInterval(Start, End)
375 && "Segment is not entirely in range!");
377 // If the span we are removing is at the start of the Segment, adjust it.
378 VNInfo *ValNo = I->valno;
379 if (I->start == Start) {
381 if (RemoveDeadValNo) {
382 // Check if val# is dead.
384 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
385 if (II != I && II->valno == ValNo) {
390 // Now that ValNo is dead, remove it.
391 markValNoForDeletion(ValNo);
395 segments.erase(I); // Removed the whole Segment.
401 // Otherwise if the span we are removing is at the end of the Segment,
402 // adjust the other way.
408 // Otherwise, we are splitting the Segment into two pieces.
409 SlotIndex OldEnd = I->end;
410 I->end = Start; // Trim the old segment.
412 // Insert the new one.
413 segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
416 /// removeValNo - Remove all the segments defined by the specified value#.
417 /// Also remove the value# from value# list.
418 void LiveRange::removeValNo(VNInfo *ValNo) {
421 iterator E = begin();
424 if (I->valno == ValNo)
427 // Now that ValNo is dead, remove it.
428 markValNoForDeletion(ValNo);
431 void LiveRange::join(LiveRange &Other,
432 const int *LHSValNoAssignments,
433 const int *RHSValNoAssignments,
434 SmallVectorImpl<VNInfo *> &NewVNInfo) {
437 // Determine if any of our values are mapped. This is uncommon, so we want
438 // to avoid the range scan if not.
439 bool MustMapCurValNos = false;
440 unsigned NumVals = getNumValNums();
441 unsigned NumNewVals = NewVNInfo.size();
442 for (unsigned i = 0; i != NumVals; ++i) {
443 unsigned LHSValID = LHSValNoAssignments[i];
445 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
446 MustMapCurValNos = true;
451 // If we have to apply a mapping to our base range assignment, rewrite it now.
452 if (MustMapCurValNos && !empty()) {
453 // Map the first live range.
455 iterator OutIt = begin();
456 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
457 for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
458 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
459 assert(nextValNo && "Huh?");
461 // If this live range has the same value # as its immediate predecessor,
462 // and if they are neighbors, remove one Segment. This happens when we
463 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
464 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
467 // Didn't merge. Move OutIt to the next segment,
469 OutIt->valno = nextValNo;
471 OutIt->start = I->start;
476 // If we merge some segments, chop off the end.
478 segments.erase(OutIt, end());
481 // Rewrite Other values before changing the VNInfo ids.
482 // This can leave Other in an invalid state because we're not coalescing
483 // touching segments that now have identical values. That's OK since Other is
484 // not supposed to be valid after calling join();
485 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
486 I->valno = NewVNInfo[RHSValNoAssignments[I->valno->id]];
488 // Update val# info. Renumber them and make sure they all belong to this
489 // LiveRange now. Also remove dead val#'s.
490 unsigned NumValNos = 0;
491 for (unsigned i = 0; i < NumNewVals; ++i) {
492 VNInfo *VNI = NewVNInfo[i];
494 if (NumValNos >= NumVals)
495 valnos.push_back(VNI);
497 valnos[NumValNos] = VNI;
498 VNI->id = NumValNos++; // Renumber val#.
501 if (NumNewVals < NumVals)
502 valnos.resize(NumNewVals); // shrinkify
504 // Okay, now insert the RHS live segments into the LHS.
505 LiveRangeUpdater Updater(this);
506 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
510 /// Merge all of the segments in RHS into this live range as the specified
511 /// value number. The segments in RHS are allowed to overlap with segments in
512 /// the current range, but only if the overlapping segments have the
513 /// specified value number.
514 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
516 LiveRangeUpdater Updater(this);
517 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I)
518 Updater.add(I->start, I->end, LHSValNo);
521 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
522 /// in RHS into this live range as the specified value number.
523 /// The segments in RHS are allowed to overlap with segments in the
524 /// current range, it will replace the value numbers of the overlaped
525 /// segments with the specified value number.
526 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
527 const VNInfo *RHSValNo,
529 LiveRangeUpdater Updater(this);
530 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I)
531 if (I->valno == RHSValNo)
532 Updater.add(I->start, I->end, LHSValNo);
535 /// MergeValueNumberInto - This method is called when two value nubmers
536 /// are found to be equivalent. This eliminates V1, replacing all
537 /// segments with the V1 value number with the V2 value number. This can
538 /// cause merging of V1/V2 values numbers and compaction of the value space.
539 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
540 assert(V1 != V2 && "Identical value#'s are always equivalent!");
542 // This code actually merges the (numerically) larger value number into the
543 // smaller value number, which is likely to allow us to compactify the value
544 // space. The only thing we have to be careful of is to preserve the
545 // instruction that defines the result value.
547 // Make sure V2 is smaller than V1.
548 if (V1->id < V2->id) {
553 // Merge V1 segments into V2.
554 for (iterator I = begin(); I != end(); ) {
556 if (S->valno != V1) continue; // Not a V1 Segment.
558 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
562 if (Prev->valno == V2 && Prev->end == S->start) {
565 // Erase this live-range.
572 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
573 // Ensure that it is a V2 live-range.
576 // If we can merge it into later V2 segments, do so now. We ignore any
577 // following V1 segments, as they will be merged in subsequent iterations
580 if (I->start == S->end && I->valno == V2) {
588 // Now that V1 is dead, remove it.
589 markValNoForDeletion(V1);
594 unsigned LiveInterval::getSize() const {
596 for (const_iterator I = begin(), E = end(); I != E; ++I)
597 Sum += I->start.distance(I->end);
601 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
602 return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ")";
605 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
606 void LiveRange::Segment::dump() const {
607 dbgs() << *this << "\n";
611 void LiveRange::print(raw_ostream &OS) const {
615 for (const_iterator I = begin(), E = end(); I != E; ++I) {
617 assert(I->valno == getValNumInfo(I->valno->id) && "Bad VNInfo");
621 // Print value number info.
622 if (getNumValNums()) {
625 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
627 const VNInfo *vni = *i;
630 if (vni->isUnused()) {
641 void LiveInterval::print(raw_ostream &OS) const {
642 OS << PrintReg(reg) << ' ';
646 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
647 void LiveRange::dump() const {
648 dbgs() << *this << "\n";
651 void LiveInterval::dump() const {
652 dbgs() << *this << "\n";
657 void LiveRange::verify() const {
658 for (const_iterator I = begin(), E = end(); I != E; ++I) {
659 assert(I->start.isValid());
660 assert(I->end.isValid());
661 assert(I->start < I->end);
662 assert(I->valno != nullptr);
663 assert(I->valno->id < valnos.size());
664 assert(I->valno == valnos[I->valno->id]);
665 if (std::next(I) != E) {
666 assert(I->end <= std::next(I)->start);
667 if (I->end == std::next(I)->start)
668 assert(I->valno != std::next(I)->valno);
675 //===----------------------------------------------------------------------===//
676 // LiveRangeUpdater class
677 //===----------------------------------------------------------------------===//
679 // The LiveRangeUpdater class always maintains these invariants:
681 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
682 // This is the initial state, and the state created by flush().
683 // In this state, isDirty() returns false.
685 // Otherwise, segments are kept in three separate areas:
687 // 1. [begin; WriteI) at the front of LR.
688 // 2. [ReadI; end) at the back of LR.
691 // - LR.begin() <= WriteI <= ReadI <= LR.end().
692 // - Segments in all three areas are fully ordered and coalesced.
693 // - Segments in area 1 precede and can't coalesce with segments in area 2.
694 // - Segments in Spills precede and can't coalesce with segments in area 2.
695 // - No coalescing is possible between segments in Spills and segments in area
696 // 1, and there are no overlapping segments.
698 // The segments in Spills are not ordered with respect to the segments in area
699 // 1. They need to be merged.
701 // When they exist, Spills.back().start <= LastStart,
702 // and WriteI[-1].start <= LastStart.
704 void LiveRangeUpdater::print(raw_ostream &OS) const {
707 OS << "Clean updater: " << *LR << '\n';
709 OS << "Null updater.\n";
712 assert(LR && "Can't have null LR in dirty updater.");
713 OS << " updater with gap = " << (ReadI - WriteI)
714 << ", last start = " << LastStart
716 for (LiveRange::const_iterator I = LR->begin(); I != WriteI; ++I)
719 for (unsigned I = 0, E = Spills.size(); I != E; ++I)
720 OS << ' ' << Spills[I];
722 for (LiveRange::const_iterator I = ReadI, E = LR->end(); I != E; ++I)
727 void LiveRangeUpdater::dump() const
732 // Determine if A and B should be coalesced.
733 static inline bool coalescable(const LiveRange::Segment &A,
734 const LiveRange::Segment &B) {
735 assert(A.start <= B.start && "Unordered live segments.");
736 if (A.end == B.start)
737 return A.valno == B.valno;
740 assert(A.valno == B.valno && "Cannot overlap different values");
744 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
745 assert(LR && "Cannot add to a null destination");
747 // Flush the state if Start moves backwards.
748 if (!LastStart.isValid() || LastStart > Seg.start) {
751 // This brings us to an uninitialized state. Reinitialize.
752 assert(Spills.empty() && "Leftover spilled segments");
753 WriteI = ReadI = LR->begin();
756 // Remember start for next time.
757 LastStart = Seg.start;
759 // Advance ReadI until it ends after Seg.start.
760 LiveRange::iterator E = LR->end();
761 if (ReadI != E && ReadI->end <= Seg.start) {
762 // First try to close the gap between WriteI and ReadI with spills.
765 // Then advance ReadI.
767 ReadI = WriteI = LR->find(Seg.start);
769 while (ReadI != E && ReadI->end <= Seg.start)
770 *WriteI++ = *ReadI++;
773 assert(ReadI == E || ReadI->end > Seg.start);
775 // Check if the ReadI segment begins early.
776 if (ReadI != E && ReadI->start <= Seg.start) {
777 assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
778 // Bail if Seg is completely contained in ReadI.
779 if (ReadI->end >= Seg.end)
781 // Coalesce into Seg.
782 Seg.start = ReadI->start;
786 // Coalesce as much as possible from ReadI into Seg.
787 while (ReadI != E && coalescable(Seg, *ReadI)) {
788 Seg.end = std::max(Seg.end, ReadI->end);
792 // Try coalescing Spills.back() into Seg.
793 if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
794 Seg.start = Spills.back().start;
795 Seg.end = std::max(Spills.back().end, Seg.end);
799 // Try coalescing Seg into WriteI[-1].
800 if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
801 WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
805 // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
806 if (WriteI != ReadI) {
811 // Finally, append to LR or Spills.
813 LR->segments.push_back(Seg);
814 WriteI = ReadI = LR->end();
816 Spills.push_back(Seg);
819 // Merge as many spilled segments as possible into the gap between WriteI
820 // and ReadI. Advance WriteI to reflect the inserted instructions.
821 void LiveRangeUpdater::mergeSpills() {
822 // Perform a backwards merge of Spills and [SpillI;WriteI).
823 size_t GapSize = ReadI - WriteI;
824 size_t NumMoved = std::min(Spills.size(), GapSize);
825 LiveRange::iterator Src = WriteI;
826 LiveRange::iterator Dst = Src + NumMoved;
827 LiveRange::iterator SpillSrc = Spills.end();
828 LiveRange::iterator B = LR->begin();
830 // This is the new WriteI position after merging spills.
833 // Now merge Src and Spills backwards.
835 if (Src != B && Src[-1].start > SpillSrc[-1].start)
838 *--Dst = *--SpillSrc;
840 assert(NumMoved == size_t(Spills.end() - SpillSrc));
841 Spills.erase(SpillSrc, Spills.end());
844 void LiveRangeUpdater::flush() {
847 // Clear the dirty state.
848 LastStart = SlotIndex();
850 assert(LR && "Cannot add to a null destination");
853 if (Spills.empty()) {
854 LR->segments.erase(WriteI, ReadI);
859 // Resize the WriteI - ReadI gap to match Spills.
860 size_t GapSize = ReadI - WriteI;
861 if (GapSize < Spills.size()) {
862 // The gap is too small. Make some room.
863 size_t WritePos = WriteI - LR->begin();
864 LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
865 // This also invalidated ReadI, but it is recomputed below.
866 WriteI = LR->begin() + WritePos;
868 // Shrink the gap if necessary.
869 LR->segments.erase(WriteI + Spills.size(), ReadI);
871 ReadI = WriteI + Spills.size();
876 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
877 // Create initial equivalence classes.
879 EqClass.grow(LI->getNumValNums());
881 const VNInfo *used = nullptr, *unused = nullptr;
883 // Determine connections.
884 for (LiveInterval::const_vni_iterator I = LI->vni_begin(), E = LI->vni_end();
886 const VNInfo *VNI = *I;
887 // Group all unused values into one class.
888 if (VNI->isUnused()) {
890 EqClass.join(unused->id, VNI->id);
895 if (VNI->isPHIDef()) {
896 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
897 assert(MBB && "Phi-def has no defining MBB");
898 // Connect to values live out of predecessors.
899 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
900 PE = MBB->pred_end(); PI != PE; ++PI)
901 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
902 EqClass.join(VNI->id, PVNI->id);
904 // Normal value defined by an instruction. Check for two-addr redef.
905 // FIXME: This could be coincidental. Should we really check for a tied
906 // operand constraint?
907 // Note that VNI->def may be a use slot for an early clobber def.
908 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
909 EqClass.join(VNI->id, UVNI->id);
913 // Lump all the unused values in with the last used value.
915 EqClass.join(used->id, unused->id);
918 return EqClass.getNumClasses();
921 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
922 MachineRegisterInfo &MRI) {
923 assert(LIV[0] && "LIV[0] must be set");
924 LiveInterval &LI = *LIV[0];
926 // Rewrite instructions.
927 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
928 RE = MRI.reg_end(); RI != RE;) {
929 MachineOperand &MO = *RI;
930 MachineInstr *MI = RI->getParent();
932 // DBG_VALUE instructions don't have slot indexes, so get the index of the
933 // instruction before them.
934 // Normally, DBG_VALUE instructions are removed before this function is
935 // called, but it is not a requirement.
937 if (MI->isDebugValue())
938 Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
940 Idx = LIS.getInstructionIndex(MI);
941 LiveQueryResult LRQ = LI.Query(Idx);
942 const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
943 // In the case of an <undef> use that isn't tied to any def, VNI will be
944 // NULL. If the use is tied to a def, VNI will be the defined value.
947 MO.setReg(LIV[getEqClass(VNI)]->reg);
950 // Move runs to new intervals.
951 LiveInterval::iterator J = LI.begin(), E = LI.end();
952 while (J != E && EqClass[J->valno->id] == 0)
954 for (LiveInterval::iterator I = J; I != E; ++I) {
955 if (unsigned eq = EqClass[I->valno->id]) {
956 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
957 "New intervals should be empty");
958 LIV[eq]->segments.push_back(*I);
962 LI.segments.erase(J, E);
964 // Transfer VNInfos to their new owners and renumber them.
965 unsigned j = 0, e = LI.getNumValNums();
966 while (j != e && EqClass[j] == 0)
968 for (unsigned i = j; i != e; ++i) {
969 VNInfo *VNI = LI.getValNumInfo(i);
970 if (unsigned eq = EqClass[i]) {
971 VNI->id = LIV[eq]->getNumValNums();
972 LIV[eq]->valnos.push_back(VNI);
975 LI.valnos[j++] = VNI;