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_iterator O = Other.begin(), OE = Other.end(); O != OE; ++O) {
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_iterator I = begin(), E = end(); I != E; ++I) {
230 VNInfo *VNI = I->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 LiveRange::iterator LiveRange::addSegmentFrom(Segment S, iterator From) {
304 SlotIndex Start = S.start, End = S.end;
305 iterator it = std::upper_bound(From, end(), Start);
307 // If the inserted segment starts in the middle or right at the end of
308 // another segment, just extend that segment to contain the segment of S.
310 iterator B = std::prev(it);
311 if (S.valno == B->valno) {
312 if (B->start <= Start && B->end >= Start) {
313 extendSegmentEndTo(B, End);
317 // Check to make sure that we are not overlapping two live segments with
318 // different valno's.
319 assert(B->end <= Start &&
320 "Cannot overlap two segments with differing ValID's"
321 " (did you def the same reg twice in a MachineInstr?)");
325 // Otherwise, if this segment ends in the middle of, or right next to, another
326 // segment, merge it into that segment.
328 if (S.valno == it->valno) {
329 if (it->start <= End) {
330 it = extendSegmentStartTo(it, Start);
332 // If S is a complete superset of a segment, we may need to grow its
335 extendSegmentEndTo(it, End);
339 // Check to make sure that we are not overlapping two live segments with
340 // different valno's.
341 assert(it->start >= End &&
342 "Cannot overlap two segments with differing ValID's");
346 // Otherwise, this is just a new segment that doesn't interact with anything.
348 return segments.insert(it, S);
351 /// extendInBlock - If this range is live before Kill in the basic
352 /// block that starts at StartIdx, extend it to be live up to Kill and return
353 /// the value. If there is no live range before Kill, return NULL.
354 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
357 iterator I = std::upper_bound(begin(), end(), Kill.getPrevSlot());
361 if (I->end <= StartIdx)
364 extendSegmentEndTo(I, Kill);
368 /// Remove the specified segment from this range. Note that the segment must
369 /// be in a single Segment in its entirety.
370 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
371 bool RemoveDeadValNo) {
372 // Find the Segment containing this span.
373 iterator I = find(Start);
374 assert(I != end() && "Segment is not in range!");
375 assert(I->containsInterval(Start, End)
376 && "Segment is not entirely in range!");
378 // If the span we are removing is at the start of the Segment, adjust it.
379 VNInfo *ValNo = I->valno;
380 if (I->start == Start) {
382 if (RemoveDeadValNo) {
383 // Check if val# is dead.
385 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
386 if (II != I && II->valno == ValNo) {
391 // Now that ValNo is dead, remove it.
392 markValNoForDeletion(ValNo);
396 segments.erase(I); // Removed the whole Segment.
402 // Otherwise if the span we are removing is at the end of the Segment,
403 // adjust the other way.
409 // Otherwise, we are splitting the Segment into two pieces.
410 SlotIndex OldEnd = I->end;
411 I->end = Start; // Trim the old segment.
413 // Insert the new one.
414 segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
417 /// removeValNo - Remove all the segments defined by the specified value#.
418 /// Also remove the value# from value# list.
419 void LiveRange::removeValNo(VNInfo *ValNo) {
422 iterator E = begin();
425 if (I->valno == ValNo)
428 // Now that ValNo is dead, remove it.
429 markValNoForDeletion(ValNo);
432 void LiveRange::join(LiveRange &Other,
433 const int *LHSValNoAssignments,
434 const int *RHSValNoAssignments,
435 SmallVectorImpl<VNInfo *> &NewVNInfo) {
438 // Determine if any of our values are mapped. This is uncommon, so we want
439 // to avoid the range scan if not.
440 bool MustMapCurValNos = false;
441 unsigned NumVals = getNumValNums();
442 unsigned NumNewVals = NewVNInfo.size();
443 for (unsigned i = 0; i != NumVals; ++i) {
444 unsigned LHSValID = LHSValNoAssignments[i];
446 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
447 MustMapCurValNos = true;
452 // If we have to apply a mapping to our base range assignment, rewrite it now.
453 if (MustMapCurValNos && !empty()) {
454 // Map the first live range.
456 iterator OutIt = begin();
457 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
458 for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
459 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
460 assert(nextValNo && "Huh?");
462 // If this live range has the same value # as its immediate predecessor,
463 // and if they are neighbors, remove one Segment. This happens when we
464 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
465 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
468 // Didn't merge. Move OutIt to the next segment,
470 OutIt->valno = nextValNo;
472 OutIt->start = I->start;
477 // If we merge some segments, chop off the end.
479 segments.erase(OutIt, end());
482 // Rewrite Other values before changing the VNInfo ids.
483 // This can leave Other in an invalid state because we're not coalescing
484 // touching segments that now have identical values. That's OK since Other is
485 // not supposed to be valid after calling join();
486 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
487 I->valno = NewVNInfo[RHSValNoAssignments[I->valno->id]];
489 // Update val# info. Renumber them and make sure they all belong to this
490 // LiveRange now. Also remove dead val#'s.
491 unsigned NumValNos = 0;
492 for (unsigned i = 0; i < NumNewVals; ++i) {
493 VNInfo *VNI = NewVNInfo[i];
495 if (NumValNos >= NumVals)
496 valnos.push_back(VNI);
498 valnos[NumValNos] = VNI;
499 VNI->id = NumValNos++; // Renumber val#.
502 if (NumNewVals < NumVals)
503 valnos.resize(NumNewVals); // shrinkify
505 // Okay, now insert the RHS live segments into the LHS.
506 LiveRangeUpdater Updater(this);
507 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
511 /// Merge all of the segments in RHS into this live range as the specified
512 /// value number. The segments in RHS are allowed to overlap with segments in
513 /// the current range, but only if the overlapping segments have the
514 /// specified value number.
515 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
517 LiveRangeUpdater Updater(this);
518 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I)
519 Updater.add(I->start, I->end, LHSValNo);
522 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
523 /// in RHS into this live range as the specified value number.
524 /// The segments in RHS are allowed to overlap with segments in the
525 /// current range, it will replace the value numbers of the overlaped
526 /// segments with the specified value number.
527 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
528 const VNInfo *RHSValNo,
530 LiveRangeUpdater Updater(this);
531 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I)
532 if (I->valno == RHSValNo)
533 Updater.add(I->start, I->end, LHSValNo);
536 /// MergeValueNumberInto - This method is called when two value nubmers
537 /// are found to be equivalent. This eliminates V1, replacing all
538 /// segments with the V1 value number with the V2 value number. This can
539 /// cause merging of V1/V2 values numbers and compaction of the value space.
540 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
541 assert(V1 != V2 && "Identical value#'s are always equivalent!");
543 // This code actually merges the (numerically) larger value number into the
544 // smaller value number, which is likely to allow us to compactify the value
545 // space. The only thing we have to be careful of is to preserve the
546 // instruction that defines the result value.
548 // Make sure V2 is smaller than V1.
549 if (V1->id < V2->id) {
554 // Merge V1 segments into V2.
555 for (iterator I = begin(); I != end(); ) {
557 if (S->valno != V1) continue; // Not a V1 Segment.
559 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
563 if (Prev->valno == V2 && Prev->end == S->start) {
566 // Erase this live-range.
573 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
574 // Ensure that it is a V2 live-range.
577 // If we can merge it into later V2 segments, do so now. We ignore any
578 // following V1 segments, as they will be merged in subsequent iterations
581 if (I->start == S->end && I->valno == V2) {
589 // Now that V1 is dead, remove it.
590 markValNoForDeletion(V1);
595 void LiveInterval::removeEmptySubRanges() {
596 SubRange **NextPtr = &SubRanges;
597 SubRange *I = *NextPtr;
598 while (I != nullptr) {
604 // Skip empty subranges until we find the first nonempty one.
607 } while (I != nullptr && I->empty());
612 unsigned LiveInterval::getSize() const {
614 for (const_iterator I = begin(), E = end(); I != E; ++I)
615 Sum += I->start.distance(I->end);
619 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
620 return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ")";
623 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
624 void LiveRange::Segment::dump() const {
625 dbgs() << *this << "\n";
629 void LiveRange::print(raw_ostream &OS) const {
633 for (const_iterator I = begin(), E = end(); I != E; ++I) {
635 assert(I->valno == getValNumInfo(I->valno->id) && "Bad VNInfo");
639 // Print value number info.
640 if (getNumValNums()) {
643 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
645 const VNInfo *vni = *i;
648 if (vni->isUnused()) {
659 void LiveInterval::print(raw_ostream &OS) const {
660 OS << PrintReg(reg) << ' ';
663 for (const_subrange_iterator I = subrange_begin(), E = subrange_end();
665 OS << format(" L%04X ", I->LaneMask) << *I;
669 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
670 void LiveRange::dump() const {
671 dbgs() << *this << "\n";
674 void LiveInterval::dump() const {
675 dbgs() << *this << "\n";
680 void LiveRange::verify() const {
681 for (const_iterator I = begin(), E = end(); I != E; ++I) {
682 assert(I->start.isValid());
683 assert(I->end.isValid());
684 assert(I->start < I->end);
685 assert(I->valno != nullptr);
686 assert(I->valno->id < valnos.size());
687 assert(I->valno == valnos[I->valno->id]);
688 if (std::next(I) != E) {
689 assert(I->end <= std::next(I)->start);
690 if (I->end == std::next(I)->start)
691 assert(I->valno != std::next(I)->valno);
696 void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
699 // Make sure SubRanges are fine and LaneMasks are disjunct.
701 unsigned MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg) : ~0u;
702 for (const_subrange_iterator I = subrange_begin(), E = subrange_end(); I != E;
704 // Subrange lanemask should be disjunct to any previous subrange masks.
705 assert((Mask & I->LaneMask) == 0);
708 // subrange mask should not contained in maximum lane mask for the vreg.
709 assert((Mask & ~MaxMask) == 0);
712 // Main liverange should cover subrange.
719 //===----------------------------------------------------------------------===//
720 // LiveRangeUpdater class
721 //===----------------------------------------------------------------------===//
723 // The LiveRangeUpdater class always maintains these invariants:
725 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
726 // This is the initial state, and the state created by flush().
727 // In this state, isDirty() returns false.
729 // Otherwise, segments are kept in three separate areas:
731 // 1. [begin; WriteI) at the front of LR.
732 // 2. [ReadI; end) at the back of LR.
735 // - LR.begin() <= WriteI <= ReadI <= LR.end().
736 // - Segments in all three areas are fully ordered and coalesced.
737 // - Segments in area 1 precede and can't coalesce with segments in area 2.
738 // - Segments in Spills precede and can't coalesce with segments in area 2.
739 // - No coalescing is possible between segments in Spills and segments in area
740 // 1, and there are no overlapping segments.
742 // The segments in Spills are not ordered with respect to the segments in area
743 // 1. They need to be merged.
745 // When they exist, Spills.back().start <= LastStart,
746 // and WriteI[-1].start <= LastStart.
748 void LiveRangeUpdater::print(raw_ostream &OS) const {
751 OS << "Clean updater: " << *LR << '\n';
753 OS << "Null updater.\n";
756 assert(LR && "Can't have null LR in dirty updater.");
757 OS << " updater with gap = " << (ReadI - WriteI)
758 << ", last start = " << LastStart
760 for (LiveRange::const_iterator I = LR->begin(); I != WriteI; ++I)
763 for (unsigned I = 0, E = Spills.size(); I != E; ++I)
764 OS << ' ' << Spills[I];
766 for (LiveRange::const_iterator I = ReadI, E = LR->end(); I != E; ++I)
771 void LiveRangeUpdater::dump() const
776 // Determine if A and B should be coalesced.
777 static inline bool coalescable(const LiveRange::Segment &A,
778 const LiveRange::Segment &B) {
779 assert(A.start <= B.start && "Unordered live segments.");
780 if (A.end == B.start)
781 return A.valno == B.valno;
784 assert(A.valno == B.valno && "Cannot overlap different values");
788 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
789 assert(LR && "Cannot add to a null destination");
791 // Flush the state if Start moves backwards.
792 if (!LastStart.isValid() || LastStart > Seg.start) {
795 // This brings us to an uninitialized state. Reinitialize.
796 assert(Spills.empty() && "Leftover spilled segments");
797 WriteI = ReadI = LR->begin();
800 // Remember start for next time.
801 LastStart = Seg.start;
803 // Advance ReadI until it ends after Seg.start.
804 LiveRange::iterator E = LR->end();
805 if (ReadI != E && ReadI->end <= Seg.start) {
806 // First try to close the gap between WriteI and ReadI with spills.
809 // Then advance ReadI.
811 ReadI = WriteI = LR->find(Seg.start);
813 while (ReadI != E && ReadI->end <= Seg.start)
814 *WriteI++ = *ReadI++;
817 assert(ReadI == E || ReadI->end > Seg.start);
819 // Check if the ReadI segment begins early.
820 if (ReadI != E && ReadI->start <= Seg.start) {
821 assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
822 // Bail if Seg is completely contained in ReadI.
823 if (ReadI->end >= Seg.end)
825 // Coalesce into Seg.
826 Seg.start = ReadI->start;
830 // Coalesce as much as possible from ReadI into Seg.
831 while (ReadI != E && coalescable(Seg, *ReadI)) {
832 Seg.end = std::max(Seg.end, ReadI->end);
836 // Try coalescing Spills.back() into Seg.
837 if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
838 Seg.start = Spills.back().start;
839 Seg.end = std::max(Spills.back().end, Seg.end);
843 // Try coalescing Seg into WriteI[-1].
844 if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
845 WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
849 // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
850 if (WriteI != ReadI) {
855 // Finally, append to LR or Spills.
857 LR->segments.push_back(Seg);
858 WriteI = ReadI = LR->end();
860 Spills.push_back(Seg);
863 // Merge as many spilled segments as possible into the gap between WriteI
864 // and ReadI. Advance WriteI to reflect the inserted instructions.
865 void LiveRangeUpdater::mergeSpills() {
866 // Perform a backwards merge of Spills and [SpillI;WriteI).
867 size_t GapSize = ReadI - WriteI;
868 size_t NumMoved = std::min(Spills.size(), GapSize);
869 LiveRange::iterator Src = WriteI;
870 LiveRange::iterator Dst = Src + NumMoved;
871 LiveRange::iterator SpillSrc = Spills.end();
872 LiveRange::iterator B = LR->begin();
874 // This is the new WriteI position after merging spills.
877 // Now merge Src and Spills backwards.
879 if (Src != B && Src[-1].start > SpillSrc[-1].start)
882 *--Dst = *--SpillSrc;
884 assert(NumMoved == size_t(Spills.end() - SpillSrc));
885 Spills.erase(SpillSrc, Spills.end());
888 void LiveRangeUpdater::flush() {
891 // Clear the dirty state.
892 LastStart = SlotIndex();
894 assert(LR && "Cannot add to a null destination");
897 if (Spills.empty()) {
898 LR->segments.erase(WriteI, ReadI);
903 // Resize the WriteI - ReadI gap to match Spills.
904 size_t GapSize = ReadI - WriteI;
905 if (GapSize < Spills.size()) {
906 // The gap is too small. Make some room.
907 size_t WritePos = WriteI - LR->begin();
908 LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
909 // This also invalidated ReadI, but it is recomputed below.
910 WriteI = LR->begin() + WritePos;
912 // Shrink the gap if necessary.
913 LR->segments.erase(WriteI + Spills.size(), ReadI);
915 ReadI = WriteI + Spills.size();
920 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
921 // Create initial equivalence classes.
923 EqClass.grow(LI->getNumValNums());
925 const VNInfo *used = nullptr, *unused = nullptr;
927 // Determine connections.
928 for (LiveInterval::const_vni_iterator I = LI->vni_begin(), E = LI->vni_end();
930 const VNInfo *VNI = *I;
931 // Group all unused values into one class.
932 if (VNI->isUnused()) {
934 EqClass.join(unused->id, VNI->id);
939 if (VNI->isPHIDef()) {
940 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
941 assert(MBB && "Phi-def has no defining MBB");
942 // Connect to values live out of predecessors.
943 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
944 PE = MBB->pred_end(); PI != PE; ++PI)
945 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
946 EqClass.join(VNI->id, PVNI->id);
948 // Normal value defined by an instruction. Check for two-addr redef.
949 // FIXME: This could be coincidental. Should we really check for a tied
950 // operand constraint?
951 // Note that VNI->def may be a use slot for an early clobber def.
952 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
953 EqClass.join(VNI->id, UVNI->id);
957 // Lump all the unused values in with the last used value.
959 EqClass.join(used->id, unused->id);
962 return EqClass.getNumClasses();
965 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
966 MachineRegisterInfo &MRI) {
967 assert(LIV[0] && "LIV[0] must be set");
968 LiveInterval &LI = *LIV[0];
970 // Rewrite instructions.
971 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
972 RE = MRI.reg_end(); RI != RE;) {
973 MachineOperand &MO = *RI;
974 MachineInstr *MI = RI->getParent();
976 // DBG_VALUE instructions don't have slot indexes, so get the index of the
977 // instruction before them.
978 // Normally, DBG_VALUE instructions are removed before this function is
979 // called, but it is not a requirement.
981 if (MI->isDebugValue())
982 Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
984 Idx = LIS.getInstructionIndex(MI);
985 LiveQueryResult LRQ = LI.Query(Idx);
986 const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
987 // In the case of an <undef> use that isn't tied to any def, VNI will be
988 // NULL. If the use is tied to a def, VNI will be the defined value.
991 MO.setReg(LIV[getEqClass(VNI)]->reg);
994 // Move runs to new intervals.
995 LiveInterval::iterator J = LI.begin(), E = LI.end();
996 while (J != E && EqClass[J->valno->id] == 0)
998 for (LiveInterval::iterator I = J; I != E; ++I) {
999 if (unsigned eq = EqClass[I->valno->id]) {
1000 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
1001 "New intervals should be empty");
1002 LIV[eq]->segments.push_back(*I);
1006 // TODO: do not cheat anymore by simply cleaning all subranges
1007 LI.clearSubRanges();
1008 LI.segments.erase(J, E);
1010 // Transfer VNInfos to their new owners and renumber them.
1011 unsigned j = 0, e = LI.getNumValNums();
1012 while (j != e && EqClass[j] == 0)
1014 for (unsigned i = j; i != e; ++i) {
1015 VNInfo *VNI = LI.getValNumInfo(i);
1016 if (unsigned eq = EqClass[i]) {
1017 VNI->id = LIV[eq]->getNumValNums();
1018 LIV[eq]->valnos.push_back(VNI);
1021 LI.valnos[j++] = VNI;
1024 LI.valnos.resize(j);