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 interval 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 intervals can have holes,
15 // i.e. an interval might look like [1,20), [50,65), [1000,1001). Each
16 // individual range is represented as an instance of LiveRange, and the whole
17 // interval is represented as an instance of LiveInterval.
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 LiveInterval::iterator LiveInterval::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 *LiveInterval::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 ranges.push_back(LiveRange(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 ranges.insert(I, LiveRange(Def, Def.getDeadSlot(), VNI));
80 // overlaps - Return true if the intersection of the two live intervals is
83 // An example for overlaps():
87 // 8: C = A + B ;; last use of A
89 // The live intervals should look like:
95 // A->overlaps(C) should return false since we want to be able to join
98 bool LiveInterval::overlapsFrom(const LiveInterval& other,
99 const_iterator StartPos) const {
100 assert(!empty() && "empty interval");
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 LiveInterval::overlaps(const LiveInterval &Other,
140 const CoalescerPair &CP,
141 const SlotIndexes &Indexes) const {
142 assert(!empty() && "empty interval");
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 interval overlaps a range specified
183 bool LiveInterval::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;
190 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
191 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
192 /// it can be nuked later.
193 void LiveInterval::markValNoForDeletion(VNInfo *ValNo) {
194 if (ValNo->id == getNumValNums()-1) {
197 } while (!valnos.empty() && valnos.back()->isUnused());
203 /// RenumberValues - Renumber all values in order of appearance and delete the
204 /// remaining unused values.
205 void LiveInterval::RenumberValues() {
206 SmallPtrSet<VNInfo*, 8> Seen;
208 for (const_iterator I = begin(), E = end(); I != E; ++I) {
209 VNInfo *VNI = I->valno;
210 if (!Seen.insert(VNI))
212 assert(!VNI->isUnused() && "Unused valno used by live range");
213 VNI->id = (unsigned)valnos.size();
214 valnos.push_back(VNI);
218 /// extendIntervalEndTo - This method is used when we want to extend the range
219 /// specified by I to end at the specified endpoint. To do this, we should
220 /// merge and eliminate all ranges that this will overlap with. The iterator is
222 void LiveInterval::extendIntervalEndTo(iterator I, SlotIndex NewEnd) {
223 assert(I != end() && "Not a valid interval!");
224 VNInfo *ValNo = I->valno;
226 // Search for the first interval that we can't merge with.
227 iterator MergeTo = llvm::next(I);
228 for (; MergeTo != end() && NewEnd >= MergeTo->end; ++MergeTo) {
229 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
232 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
233 I->end = std::max(NewEnd, prior(MergeTo)->end);
235 // If the newly formed range now touches the range after it and if they have
236 // the same value number, merge the two ranges into one range.
237 if (MergeTo != end() && MergeTo->start <= I->end &&
238 MergeTo->valno == ValNo) {
239 I->end = MergeTo->end;
243 // Erase any dead ranges.
244 ranges.erase(llvm::next(I), MergeTo);
248 /// extendIntervalStartTo - This method is used when we want to extend the range
249 /// specified by I to start at the specified endpoint. To do this, we should
250 /// merge and eliminate all ranges that this will overlap with.
251 LiveInterval::iterator
252 LiveInterval::extendIntervalStartTo(iterator I, SlotIndex NewStart) {
253 assert(I != end() && "Not a valid interval!");
254 VNInfo *ValNo = I->valno;
256 // Search for the first interval that we can't merge with.
257 iterator MergeTo = I;
259 if (MergeTo == begin()) {
261 ranges.erase(MergeTo, I);
264 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
266 } while (NewStart <= MergeTo->start);
268 // If we start in the middle of another interval, just delete a range and
269 // extend that interval.
270 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
271 MergeTo->end = I->end;
273 // Otherwise, extend the interval right after.
275 MergeTo->start = NewStart;
276 MergeTo->end = I->end;
279 ranges.erase(llvm::next(MergeTo), llvm::next(I));
283 LiveInterval::iterator
284 LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
285 SlotIndex Start = LR.start, End = LR.end;
286 iterator it = std::upper_bound(From, end(), Start);
288 // If the inserted interval starts in the middle or right at the end of
289 // another interval, just extend that interval to contain the range of LR.
291 iterator B = prior(it);
292 if (LR.valno == B->valno) {
293 if (B->start <= Start && B->end >= Start) {
294 extendIntervalEndTo(B, End);
298 // Check to make sure that we are not overlapping two live ranges with
299 // different valno's.
300 assert(B->end <= Start &&
301 "Cannot overlap two LiveRanges with differing ValID's"
302 " (did you def the same reg twice in a MachineInstr?)");
306 // Otherwise, if this range ends in the middle of, or right next to, another
307 // interval, merge it into that interval.
309 if (LR.valno == it->valno) {
310 if (it->start <= End) {
311 it = extendIntervalStartTo(it, Start);
313 // If LR is a complete superset of an interval, we may need to grow its
316 extendIntervalEndTo(it, End);
320 // Check to make sure that we are not overlapping two live ranges with
321 // different valno's.
322 assert(it->start >= End &&
323 "Cannot overlap two LiveRanges with differing ValID's");
327 // Otherwise, this is just a new range that doesn't interact with anything.
329 return ranges.insert(it, LR);
332 /// extendInBlock - If this interval is live before Kill in the basic
333 /// block that starts at StartIdx, extend it to be live up to Kill and return
334 /// the value. If there is no live range before Kill, return NULL.
335 VNInfo *LiveInterval::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
338 iterator I = std::upper_bound(begin(), end(), Kill.getPrevSlot());
342 if (I->end <= StartIdx)
345 extendIntervalEndTo(I, Kill);
349 /// removeRange - Remove the specified range from this interval. Note that
350 /// the range must be in a single LiveRange in its entirety.
351 void LiveInterval::removeRange(SlotIndex Start, SlotIndex End,
352 bool RemoveDeadValNo) {
353 // Find the LiveRange containing this span.
354 iterator I = find(Start);
355 assert(I != end() && "Range is not in interval!");
356 assert(I->containsRange(Start, End) && "Range is not entirely in interval!");
358 // If the span we are removing is at the start of the LiveRange, adjust it.
359 VNInfo *ValNo = I->valno;
360 if (I->start == Start) {
362 if (RemoveDeadValNo) {
363 // Check if val# is dead.
365 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
366 if (II != I && II->valno == ValNo) {
371 // Now that ValNo is dead, remove it.
372 markValNoForDeletion(ValNo);
376 ranges.erase(I); // Removed the whole LiveRange.
382 // Otherwise if the span we are removing is at the end of the LiveRange,
383 // adjust the other way.
389 // Otherwise, we are splitting the LiveRange into two pieces.
390 SlotIndex OldEnd = I->end;
391 I->end = Start; // Trim the old interval.
393 // Insert the new one.
394 ranges.insert(llvm::next(I), LiveRange(End, OldEnd, ValNo));
397 /// removeValNo - Remove all the ranges defined by the specified value#.
398 /// Also remove the value# from value# list.
399 void LiveInterval::removeValNo(VNInfo *ValNo) {
402 iterator E = begin();
405 if (I->valno == ValNo)
408 // Now that ValNo is dead, remove it.
409 markValNoForDeletion(ValNo);
412 /// join - Join two live intervals (this, and other) together. This applies
413 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
414 /// the intervals are not joinable, this aborts.
415 void LiveInterval::join(LiveInterval &Other,
416 const int *LHSValNoAssignments,
417 const int *RHSValNoAssignments,
418 SmallVectorImpl<VNInfo *> &NewVNInfo) {
421 // Determine if any of our live range values are mapped. This is uncommon, so
422 // we want to avoid the interval scan if not.
423 bool MustMapCurValNos = false;
424 unsigned NumVals = getNumValNums();
425 unsigned NumNewVals = NewVNInfo.size();
426 for (unsigned i = 0; i != NumVals; ++i) {
427 unsigned LHSValID = LHSValNoAssignments[i];
429 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
430 MustMapCurValNos = true;
435 // If we have to apply a mapping to our base interval assignment, rewrite it
437 if (MustMapCurValNos && !empty()) {
438 // Map the first live range.
440 iterator OutIt = begin();
441 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
442 for (iterator I = llvm::next(OutIt), E = end(); I != E; ++I) {
443 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
444 assert(nextValNo != 0 && "Huh?");
446 // If this live range has the same value # as its immediate predecessor,
447 // and if they are neighbors, remove one LiveRange. This happens when we
448 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
449 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
452 // Didn't merge. Move OutIt to the next interval,
454 OutIt->valno = nextValNo;
456 OutIt->start = I->start;
461 // If we merge some live ranges, chop off the end.
463 ranges.erase(OutIt, end());
466 // Rewrite Other values before changing the VNInfo ids.
467 // This can leave Other in an invalid state because we're not coalescing
468 // touching segments that now have identical values. That's OK since Other is
469 // not supposed to be valid after calling join();
470 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
471 I->valno = NewVNInfo[RHSValNoAssignments[I->valno->id]];
473 // Update val# info. Renumber them and make sure they all belong to this
474 // LiveInterval now. Also remove dead val#'s.
475 unsigned NumValNos = 0;
476 for (unsigned i = 0; i < NumNewVals; ++i) {
477 VNInfo *VNI = NewVNInfo[i];
479 if (NumValNos >= NumVals)
480 valnos.push_back(VNI);
482 valnos[NumValNos] = VNI;
483 VNI->id = NumValNos++; // Renumber val#.
486 if (NumNewVals < NumVals)
487 valnos.resize(NumNewVals); // shrinkify
489 // Okay, now insert the RHS live ranges into the LHS.
490 LiveRangeUpdater Updater(this);
491 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
495 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
496 /// interval as the specified value number. The LiveRanges in RHS are
497 /// allowed to overlap with LiveRanges in the current interval, but only if
498 /// the overlapping LiveRanges have the specified value number.
499 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
501 LiveRangeUpdater Updater(this);
502 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I)
503 Updater.add(I->start, I->end, LHSValNo);
506 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
507 /// in RHS into this live interval as the specified value number.
508 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
509 /// current interval, it will replace the value numbers of the overlaped
510 /// live ranges with the specified value number.
511 void LiveInterval::MergeValueInAsValue(const LiveInterval &RHS,
512 const VNInfo *RHSValNo,
514 LiveRangeUpdater Updater(this);
515 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I)
516 if (I->valno == RHSValNo)
517 Updater.add(I->start, I->end, LHSValNo);
520 /// MergeValueNumberInto - This method is called when two value nubmers
521 /// are found to be equivalent. This eliminates V1, replacing all
522 /// LiveRanges with the V1 value number with the V2 value number. This can
523 /// cause merging of V1/V2 values numbers and compaction of the value space.
524 VNInfo* LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
525 assert(V1 != V2 && "Identical value#'s are always equivalent!");
527 // This code actually merges the (numerically) larger value number into the
528 // smaller value number, which is likely to allow us to compactify the value
529 // space. The only thing we have to be careful of is to preserve the
530 // instruction that defines the result value.
532 // Make sure V2 is smaller than V1.
533 if (V1->id < V2->id) {
538 // Merge V1 live ranges into V2.
539 for (iterator I = begin(); I != end(); ) {
541 if (LR->valno != V1) continue; // Not a V1 LiveRange.
543 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
546 iterator Prev = LR-1;
547 if (Prev->valno == V2 && Prev->end == LR->start) {
550 // Erase this live-range.
557 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
558 // Ensure that it is a V2 live-range.
561 // If we can merge it into later V2 live ranges, do so now. We ignore any
562 // following V1 live ranges, as they will be merged in subsequent iterations
565 if (I->start == LR->end && I->valno == V2) {
573 // Now that V1 is dead, remove it.
574 markValNoForDeletion(V1);
579 unsigned LiveInterval::getSize() const {
581 for (const_iterator I = begin(), E = end(); I != E; ++I)
582 Sum += I->start.distance(I->end);
586 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange &LR) {
587 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")";
590 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
591 void LiveRange::dump() const {
592 dbgs() << *this << "\n";
596 void LiveInterval::print(raw_ostream &OS) const {
600 for (const_iterator I = begin(), E = end(); I != E; ++I) {
602 assert(I->valno == getValNumInfo(I->valno->id) && "Bad VNInfo");
606 // Print value number info.
607 if (getNumValNums()) {
610 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
612 const VNInfo *vni = *i;
615 if (vni->isUnused()) {
626 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
627 void LiveInterval::dump() const {
628 dbgs() << *this << "\n";
633 void LiveInterval::verify() const {
634 for (const_iterator I = begin(), E = end(); I != E; ++I) {
635 assert(I->start.isValid());
636 assert(I->end.isValid());
637 assert(I->start < I->end);
638 assert(I->valno != 0);
639 assert(I->valno == valnos[I->valno->id]);
640 if (llvm::next(I) != E) {
641 assert(I->end <= llvm::next(I)->start);
642 if (I->end == llvm::next(I)->start)
643 assert(I->valno != llvm::next(I)->valno);
650 void LiveRange::print(raw_ostream &os) const {
654 //===----------------------------------------------------------------------===//
655 // LiveRangeUpdater class
656 //===----------------------------------------------------------------------===//
658 // The LiveRangeUpdater class always maintains these invariants:
660 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
661 // This is the initial state, and the state created by flush().
662 // In this state, isDirty() returns false.
664 // Otherwise, segments are kept in three separate areas:
666 // 1. [begin; WriteI) at the front of LI.
667 // 2. [ReadI; end) at the back of LI.
670 // - LI.begin() <= WriteI <= ReadI <= LI.end().
671 // - Segments in all three areas are fully ordered and coalesced.
672 // - Segments in area 1 precede and can't coalesce with segments in area 2.
673 // - Segments in Spills precede and can't coalesce with segments in area 2.
674 // - No coalescing is possible between segments in Spills and segments in area
675 // 1, and there are no overlapping segments.
677 // The segments in Spills are not ordered with respect to the segments in area
678 // 1. They need to be merged.
680 // When they exist, Spills.back().start <= LastStart,
681 // and WriteI[-1].start <= LastStart.
683 void LiveRangeUpdater::print(raw_ostream &OS) const {
686 OS << "Clean " << PrintReg(LI->reg) << " updater: " << *LI << '\n';
688 OS << "Null updater.\n";
691 assert(LI && "Can't have null LI in dirty updater.");
692 OS << PrintReg(LI->reg) << " updater with gap = " << (ReadI - WriteI)
693 << ", last start = " << LastStart
695 for (LiveInterval::const_iterator I = LI->begin(); I != WriteI; ++I)
698 for (unsigned I = 0, E = Spills.size(); I != E; ++I)
699 OS << ' ' << Spills[I];
701 for (LiveInterval::const_iterator I = ReadI, E = LI->end(); I != E; ++I)
706 void LiveRangeUpdater::dump() const
711 // Determine if A and B should be coalesced.
712 static inline bool coalescable(const LiveRange &A, const LiveRange &B) {
713 assert(A.start <= B.start && "Unordered live ranges.");
714 if (A.end == B.start)
715 return A.valno == B.valno;
718 assert(A.valno == B.valno && "Cannot overlap different values");
722 void LiveRangeUpdater::add(LiveRange Seg) {
723 assert(LI && "Cannot add to a null destination");
725 // Flush the state if Start moves backwards.
726 if (!LastStart.isValid() || LastStart > Seg.start) {
729 // This brings us to an uninitialized state. Reinitialize.
730 assert(Spills.empty() && "Leftover spilled segments");
731 WriteI = ReadI = LI->begin();
734 // Remember start for next time.
735 LastStart = Seg.start;
737 // Advance ReadI until it ends after Seg.start.
738 LiveInterval::iterator E = LI->end();
739 if (ReadI != E && ReadI->end <= Seg.start) {
740 // First try to close the gap between WriteI and ReadI with spills.
743 // Then advance ReadI.
745 ReadI = WriteI = LI->find(Seg.start);
747 while (ReadI != E && ReadI->end <= Seg.start)
748 *WriteI++ = *ReadI++;
751 assert(ReadI == E || ReadI->end > Seg.start);
753 // Check if the ReadI segment begins early.
754 if (ReadI != E && ReadI->start <= Seg.start) {
755 assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
756 // Bail if Seg is completely contained in ReadI.
757 if (ReadI->end >= Seg.end)
759 // Coalesce into Seg.
760 Seg.start = ReadI->start;
764 // Coalesce as much as possible from ReadI into Seg.
765 while (ReadI != E && coalescable(Seg, *ReadI)) {
766 Seg.end = std::max(Seg.end, ReadI->end);
770 // Try coalescing Spills.back() into Seg.
771 if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
772 Seg.start = Spills.back().start;
773 Seg.end = std::max(Spills.back().end, Seg.end);
777 // Try coalescing Seg into WriteI[-1].
778 if (WriteI != LI->begin() && coalescable(WriteI[-1], Seg)) {
779 WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
783 // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
784 if (WriteI != ReadI) {
789 // Finally, append to LI or Spills.
791 LI->ranges.push_back(Seg);
792 WriteI = ReadI = LI->end();
794 Spills.push_back(Seg);
797 // Merge as many spilled segments as possible into the gap between WriteI
798 // and ReadI. Advance WriteI to reflect the inserted instructions.
799 void LiveRangeUpdater::mergeSpills() {
800 // Perform a backwards merge of Spills and [SpillI;WriteI).
801 size_t GapSize = ReadI - WriteI;
802 size_t NumMoved = std::min(Spills.size(), GapSize);
803 LiveInterval::iterator Src = WriteI;
804 LiveInterval::iterator Dst = Src + NumMoved;
805 LiveInterval::iterator SpillSrc = Spills.end();
806 LiveInterval::iterator B = LI->begin();
808 // This is the new WriteI position after merging spills.
811 // Now merge Src and Spills backwards.
813 if (Src != B && Src[-1].start > SpillSrc[-1].start)
816 *--Dst = *--SpillSrc;
818 assert(NumMoved == size_t(Spills.end() - SpillSrc));
819 Spills.erase(SpillSrc, Spills.end());
822 void LiveRangeUpdater::flush() {
825 // Clear the dirty state.
826 LastStart = SlotIndex();
828 assert(LI && "Cannot add to a null destination");
831 if (Spills.empty()) {
832 LI->ranges.erase(WriteI, ReadI);
837 // Resize the WriteI - ReadI gap to match Spills.
838 size_t GapSize = ReadI - WriteI;
839 if (GapSize < Spills.size()) {
840 // The gap is too small. Make some room.
841 size_t WritePos = WriteI - LI->begin();
842 LI->ranges.insert(ReadI, Spills.size() - GapSize, LiveRange());
843 // This also invalidated ReadI, but it is recomputed below.
844 WriteI = LI->begin() + WritePos;
846 // Shrink the gap if necessary.
847 LI->ranges.erase(WriteI + Spills.size(), ReadI);
849 ReadI = WriteI + Spills.size();
854 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
855 // Create initial equivalence classes.
857 EqClass.grow(LI->getNumValNums());
859 const VNInfo *used = 0, *unused = 0;
861 // Determine connections.
862 for (LiveInterval::const_vni_iterator I = LI->vni_begin(), E = LI->vni_end();
864 const VNInfo *VNI = *I;
865 // Group all unused values into one class.
866 if (VNI->isUnused()) {
868 EqClass.join(unused->id, VNI->id);
873 if (VNI->isPHIDef()) {
874 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
875 assert(MBB && "Phi-def has no defining MBB");
876 // Connect to values live out of predecessors.
877 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
878 PE = MBB->pred_end(); PI != PE; ++PI)
879 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
880 EqClass.join(VNI->id, PVNI->id);
882 // Normal value defined by an instruction. Check for two-addr redef.
883 // FIXME: This could be coincidental. Should we really check for a tied
884 // operand constraint?
885 // Note that VNI->def may be a use slot for an early clobber def.
886 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
887 EqClass.join(VNI->id, UVNI->id);
891 // Lump all the unused values in with the last used value.
893 EqClass.join(used->id, unused->id);
896 return EqClass.getNumClasses();
899 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
900 MachineRegisterInfo &MRI) {
901 assert(LIV[0] && "LIV[0] must be set");
902 LiveInterval &LI = *LIV[0];
904 // Rewrite instructions.
905 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
906 RE = MRI.reg_end(); RI != RE;) {
907 MachineOperand &MO = RI.getOperand();
908 MachineInstr *MI = MO.getParent();
910 // DBG_VALUE instructions don't have slot indexes, so get the index of the
911 // instruction before them.
912 // Normally, DBG_VALUE instructions are removed before this function is
913 // called, but it is not a requirement.
915 if (MI->isDebugValue())
916 Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
918 Idx = LIS.getInstructionIndex(MI);
919 LiveRangeQuery LRQ(LI, Idx);
920 const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
921 // In the case of an <undef> use that isn't tied to any def, VNI will be
922 // NULL. If the use is tied to a def, VNI will be the defined value.
925 MO.setReg(LIV[getEqClass(VNI)]->reg);
928 // Move runs to new intervals.
929 LiveInterval::iterator J = LI.begin(), E = LI.end();
930 while (J != E && EqClass[J->valno->id] == 0)
932 for (LiveInterval::iterator I = J; I != E; ++I) {
933 if (unsigned eq = EqClass[I->valno->id]) {
934 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
935 "New intervals should be empty");
936 LIV[eq]->ranges.push_back(*I);
940 LI.ranges.erase(J, E);
942 // Transfer VNInfos to their new owners and renumber them.
943 unsigned j = 0, e = LI.getNumValNums();
944 while (j != e && EqClass[j] == 0)
946 for (unsigned i = j; i != e; ++i) {
947 VNInfo *VNI = LI.getValNumInfo(i);
948 if (unsigned eq = EqClass[i]) {
949 VNI->id = LIV[eq]->getNumValNums();
950 LIV[eq]->valnos.push_back(VNI);
953 LI.valnos[j++] = VNI;