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 "llvm/CodeGen/LiveIntervalAnalysis.h"
23 #include "llvm/CodeGen/MachineRegisterInfo.h"
24 #include "llvm/ADT/DenseMap.h"
25 #include "llvm/ADT/SmallSet.h"
26 #include "llvm/ADT/STLExtras.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/Target/TargetRegisterInfo.h"
33 // An example for liveAt():
35 // this = [1,4), liveAt(0) will return false. The instruction defining this
36 // spans slots [0,3]. The interval belongs to an spilled definition of the
37 // variable it represents. This is because slot 1 is used (def slot) and spans
38 // up to slot 3 (store slot).
40 bool LiveInterval::liveAt(SlotIndex I) const {
41 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
43 if (r == ranges.begin())
47 return r->contains(I);
50 /// killedAt - Return true if a live range ends at index. Note that the kill
51 /// point is not contained in the half-open live range. It is usually the
52 /// getDefIndex() slot following its last use.
53 bool LiveInterval::killedAt(SlotIndex I) const {
54 Ranges::const_iterator r = std::lower_bound(ranges.begin(), ranges.end(), I);
56 // Now r points to the first interval with start >= I, or ranges.end().
57 if (r == ranges.begin())
61 // Now r points to the last interval with end <= I.
62 // r->end is the kill point.
66 /// killedInRange - Return true if the interval has kills in [Start,End).
67 bool LiveInterval::killedInRange(SlotIndex Start, SlotIndex End) const {
68 Ranges::const_iterator r =
69 std::lower_bound(ranges.begin(), ranges.end(), End);
71 // Now r points to the first interval with start >= End, or ranges.end().
72 if (r == ranges.begin())
76 // Now r points to the last interval with end <= End.
77 // r->end is the kill point.
78 return r->end >= Start && r->end < End;
81 // overlaps - Return true if the intersection of the two live intervals is
84 // An example for overlaps():
88 // 8: C = A + B ;; last use of A
90 // The live intervals should look like:
96 // A->overlaps(C) should return false since we want to be able to join
99 bool LiveInterval::overlapsFrom(const LiveInterval& other,
100 const_iterator StartPos) const {
101 assert(!empty() && "empty interval");
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 != ranges.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.ranges.begin()) --j;
124 if (j == je) return false;
127 if (i->start > j->start) {
132 if (i->end > j->start)
140 /// overlaps - Return true if the live interval overlaps a range specified
142 bool LiveInterval::overlaps(SlotIndex Start, SlotIndex End) const {
143 assert(Start < End && "Invalid range");
144 const_iterator I = std::lower_bound(begin(), end(), End);
145 return I != begin() && (--I)->end > Start;
149 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
150 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
151 /// it can be nuked later.
152 void LiveInterval::markValNoForDeletion(VNInfo *ValNo) {
153 if (ValNo->id == getNumValNums()-1) {
156 } while (!valnos.empty() && valnos.back()->isUnused());
158 ValNo->setIsUnused(true);
162 /// RenumberValues - Renumber all values in order of appearance and delete the
163 /// remaining unused values.
164 void LiveInterval::RenumberValues(LiveIntervals &lis) {
165 SmallPtrSet<VNInfo*, 8> Seen;
166 bool seenPHIDef = false;
168 for (const_iterator I = begin(), E = end(); I != E; ++I) {
169 VNInfo *VNI = I->valno;
170 if (!Seen.insert(VNI))
172 assert(!VNI->isUnused() && "Unused valno used by live range");
173 VNI->id = (unsigned)valnos.size();
174 valnos.push_back(VNI);
175 VNI->setHasPHIKill(false);
180 // Recompute phi kill flags.
183 for (const_vni_iterator I = vni_begin(), E = vni_end(); I != E; ++I) {
185 if (!VNI->isPHIDef())
187 const MachineBasicBlock *PHIBB = lis.getMBBFromIndex(VNI->def);
188 assert(PHIBB && "No basic block for phi-def");
189 for (MachineBasicBlock::const_pred_iterator PI = PHIBB->pred_begin(),
190 PE = PHIBB->pred_end(); PI != PE; ++PI) {
191 VNInfo *KVNI = getVNInfoAt(lis.getMBBEndIdx(*PI).getPrevSlot());
193 KVNI->setHasPHIKill(true);
198 /// extendIntervalEndTo - This method is used when we want to extend the range
199 /// specified by I to end at the specified endpoint. To do this, we should
200 /// merge and eliminate all ranges that this will overlap with. The iterator is
202 void LiveInterval::extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd) {
203 assert(I != ranges.end() && "Not a valid interval!");
204 VNInfo *ValNo = I->valno;
206 // Search for the first interval that we can't merge with.
207 Ranges::iterator MergeTo = llvm::next(I);
208 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
209 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
212 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
213 I->end = std::max(NewEnd, prior(MergeTo)->end);
215 // Erase any dead ranges.
216 ranges.erase(llvm::next(I), MergeTo);
218 // If the newly formed range now touches the range after it and if they have
219 // the same value number, merge the two ranges into one range.
220 Ranges::iterator Next = llvm::next(I);
221 if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) {
228 /// extendIntervalStartTo - This method is used when we want to extend the range
229 /// specified by I to start at the specified endpoint. To do this, we should
230 /// merge and eliminate all ranges that this will overlap with.
231 LiveInterval::Ranges::iterator
232 LiveInterval::extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStart) {
233 assert(I != ranges.end() && "Not a valid interval!");
234 VNInfo *ValNo = I->valno;
236 // Search for the first interval that we can't merge with.
237 Ranges::iterator MergeTo = I;
239 if (MergeTo == ranges.begin()) {
241 ranges.erase(MergeTo, I);
244 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
246 } while (NewStart <= MergeTo->start);
248 // If we start in the middle of another interval, just delete a range and
249 // extend that interval.
250 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
251 MergeTo->end = I->end;
253 // Otherwise, extend the interval right after.
255 MergeTo->start = NewStart;
256 MergeTo->end = I->end;
259 ranges.erase(llvm::next(MergeTo), llvm::next(I));
263 LiveInterval::iterator
264 LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
265 SlotIndex Start = LR.start, End = LR.end;
266 iterator it = std::upper_bound(From, ranges.end(), Start);
268 // If the inserted interval starts in the middle or right at the end of
269 // another interval, just extend that interval to contain the range of LR.
270 if (it != ranges.begin()) {
271 iterator B = prior(it);
272 if (LR.valno == B->valno) {
273 if (B->start <= Start && B->end >= Start) {
274 extendIntervalEndTo(B, End);
278 // Check to make sure that we are not overlapping two live ranges with
279 // different valno's.
280 assert(B->end <= Start &&
281 "Cannot overlap two LiveRanges with differing ValID's"
282 " (did you def the same reg twice in a MachineInstr?)");
286 // Otherwise, if this range ends in the middle of, or right next to, another
287 // interval, merge it into that interval.
288 if (it != ranges.end()) {
289 if (LR.valno == it->valno) {
290 if (it->start <= End) {
291 it = extendIntervalStartTo(it, Start);
293 // If LR is a complete superset of an interval, we may need to grow its
296 extendIntervalEndTo(it, End);
300 // Check to make sure that we are not overlapping two live ranges with
301 // different valno's.
302 assert(it->start >= End &&
303 "Cannot overlap two LiveRanges with differing ValID's");
307 // Otherwise, this is just a new range that doesn't interact with anything.
309 return ranges.insert(it, LR);
312 /// isInOneLiveRange - Return true if the range specified is entirely in
313 /// a single LiveRange of the live interval.
314 bool LiveInterval::isInOneLiveRange(SlotIndex Start, SlotIndex End) {
315 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
316 if (I == ranges.begin())
319 return I->containsRange(Start, End);
323 /// removeRange - Remove the specified range from this interval. Note that
324 /// the range must be in a single LiveRange in its entirety.
325 void LiveInterval::removeRange(SlotIndex Start, SlotIndex End,
326 bool RemoveDeadValNo) {
327 // Find the LiveRange containing this span.
328 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
329 assert(I != ranges.begin() && "Range is not in interval!");
331 assert(I->containsRange(Start, End) && "Range is not entirely in interval!");
333 // If the span we are removing is at the start of the LiveRange, adjust it.
334 VNInfo *ValNo = I->valno;
335 if (I->start == Start) {
337 if (RemoveDeadValNo) {
338 // Check if val# is dead.
340 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
341 if (II != I && II->valno == ValNo) {
346 // Now that ValNo is dead, remove it.
347 markValNoForDeletion(ValNo);
351 ranges.erase(I); // Removed the whole LiveRange.
357 // Otherwise if the span we are removing is at the end of the LiveRange,
358 // adjust the other way.
364 // Otherwise, we are splitting the LiveRange into two pieces.
365 SlotIndex OldEnd = I->end;
366 I->end = Start; // Trim the old interval.
368 // Insert the new one.
369 ranges.insert(llvm::next(I), LiveRange(End, OldEnd, ValNo));
372 /// removeValNo - Remove all the ranges defined by the specified value#.
373 /// Also remove the value# from value# list.
374 void LiveInterval::removeValNo(VNInfo *ValNo) {
376 Ranges::iterator I = ranges.end();
377 Ranges::iterator E = ranges.begin();
380 if (I->valno == ValNo)
383 // Now that ValNo is dead, remove it.
384 markValNoForDeletion(ValNo);
387 /// getLiveRangeContaining - Return the live range that contains the
388 /// specified index, or null if there is none.
389 LiveInterval::const_iterator
390 LiveInterval::FindLiveRangeContaining(SlotIndex Idx) const {
391 const_iterator It = std::upper_bound(begin(), end(), Idx);
392 if (It != ranges.begin()) {
394 if (It->contains(Idx))
401 LiveInterval::iterator
402 LiveInterval::FindLiveRangeContaining(SlotIndex Idx) {
403 iterator It = std::upper_bound(begin(), end(), Idx);
406 if (It->contains(Idx))
413 /// findDefinedVNInfo - Find the VNInfo defined by the specified
414 /// index (register interval).
415 VNInfo *LiveInterval::findDefinedVNInfoForRegInt(SlotIndex Idx) const {
416 for (LiveInterval::const_vni_iterator i = vni_begin(), e = vni_end();
418 if ((*i)->def == Idx)
425 /// join - Join two live intervals (this, and other) together. This applies
426 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
427 /// the intervals are not joinable, this aborts.
428 void LiveInterval::join(LiveInterval &Other,
429 const int *LHSValNoAssignments,
430 const int *RHSValNoAssignments,
431 SmallVector<VNInfo*, 16> &NewVNInfo,
432 MachineRegisterInfo *MRI) {
433 // Determine if any of our live range values are mapped. This is uncommon, so
434 // we want to avoid the interval scan if not.
435 bool MustMapCurValNos = false;
436 unsigned NumVals = getNumValNums();
437 unsigned NumNewVals = NewVNInfo.size();
438 for (unsigned i = 0; i != NumVals; ++i) {
439 unsigned LHSValID = LHSValNoAssignments[i];
441 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i)))
442 MustMapCurValNos = true;
445 // If we have to apply a mapping to our base interval assignment, rewrite it
447 if (MustMapCurValNos) {
448 // Map the first live range.
449 iterator OutIt = begin();
450 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
452 for (iterator I = OutIt, E = end(); I != E; ++I) {
453 OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]];
455 // If this live range has the same value # as its immediate predecessor,
456 // and if they are neighbors, remove one LiveRange. This happens when we
457 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
458 if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) {
459 (OutIt-1)->end = OutIt->end;
462 OutIt->start = I->start;
466 // Didn't merge, on to the next one.
471 // If we merge some live ranges, chop off the end.
472 ranges.erase(OutIt, end());
475 // Remember assignements because val# ids are changing.
476 SmallVector<unsigned, 16> OtherAssignments;
477 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
478 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]);
480 // Update val# info. Renumber them and make sure they all belong to this
481 // LiveInterval now. Also remove dead val#'s.
482 unsigned NumValNos = 0;
483 for (unsigned i = 0; i < NumNewVals; ++i) {
484 VNInfo *VNI = NewVNInfo[i];
486 if (NumValNos >= NumVals)
487 valnos.push_back(VNI);
489 valnos[NumValNos] = VNI;
490 VNI->id = NumValNos++; // Renumber val#.
493 if (NumNewVals < NumVals)
494 valnos.resize(NumNewVals); // shrinkify
496 // Okay, now insert the RHS live ranges into the LHS.
497 iterator InsertPos = begin();
498 unsigned RangeNo = 0;
499 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) {
500 // Map the valno in the other live range to the current live range.
501 I->valno = NewVNInfo[OtherAssignments[RangeNo]];
502 assert(I->valno && "Adding a dead range?");
503 InsertPos = addRangeFrom(*I, InsertPos);
506 ComputeJoinedWeight(Other);
509 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
510 /// interval as the specified value number. The LiveRanges in RHS are
511 /// allowed to overlap with LiveRanges in the current interval, but only if
512 /// the overlapping LiveRanges have the specified value number.
513 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
515 // TODO: Make this more efficient.
516 iterator InsertPos = begin();
517 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
518 // Map the valno in the other live range to the current live range.
520 Tmp.valno = LHSValNo;
521 InsertPos = addRangeFrom(Tmp, InsertPos);
526 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
527 /// in RHS into this live interval as the specified value number.
528 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
529 /// current interval, it will replace the value numbers of the overlaped
530 /// live ranges with the specified value number.
531 void LiveInterval::MergeValueInAsValue(
532 const LiveInterval &RHS,
533 const VNInfo *RHSValNo, VNInfo *LHSValNo) {
534 SmallVector<VNInfo*, 4> ReplacedValNos;
535 iterator IP = begin();
536 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
537 assert(I->valno == RHS.getValNumInfo(I->valno->id) && "Bad VNInfo");
538 if (I->valno != RHSValNo)
540 SlotIndex Start = I->start, End = I->end;
541 IP = std::upper_bound(IP, end(), Start);
542 // If the start of this range overlaps with an existing liverange, trim it.
543 if (IP != begin() && IP[-1].end > Start) {
544 if (IP[-1].valno != LHSValNo) {
545 ReplacedValNos.push_back(IP[-1].valno);
546 IP[-1].valno = LHSValNo; // Update val#.
549 // Trimmed away the whole range?
550 if (Start >= End) continue;
552 // If the end of this range overlaps with an existing liverange, trim it.
553 if (IP != end() && End > IP->start) {
554 if (IP->valno != LHSValNo) {
555 ReplacedValNos.push_back(IP->valno);
556 IP->valno = LHSValNo; // Update val#.
559 // If this trimmed away the whole range, ignore it.
560 if (Start == End) continue;
563 // Map the valno in the other live range to the current live range.
564 IP = addRangeFrom(LiveRange(Start, End, LHSValNo), IP);
568 SmallSet<VNInfo*, 4> Seen;
569 for (unsigned i = 0, e = ReplacedValNos.size(); i != e; ++i) {
570 VNInfo *V1 = ReplacedValNos[i];
571 if (Seen.insert(V1)) {
573 for (const_iterator I = begin(), E = end(); I != E; ++I)
574 if (I->valno == V1) {
579 // Now that V1 is dead, remove it.
580 markValNoForDeletion(V1);
588 /// MergeValueNumberInto - This method is called when two value nubmers
589 /// are found to be equivalent. This eliminates V1, replacing all
590 /// LiveRanges with the V1 value number with the V2 value number. This can
591 /// cause merging of V1/V2 values numbers and compaction of the value space.
592 VNInfo* LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
593 assert(V1 != V2 && "Identical value#'s are always equivalent!");
595 // This code actually merges the (numerically) larger value number into the
596 // smaller value number, which is likely to allow us to compactify the value
597 // space. The only thing we have to be careful of is to preserve the
598 // instruction that defines the result value.
600 // Make sure V2 is smaller than V1.
601 if (V1->id < V2->id) {
606 // Merge V1 live ranges into V2.
607 for (iterator I = begin(); I != end(); ) {
609 if (LR->valno != V1) continue; // Not a V1 LiveRange.
611 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
614 iterator Prev = LR-1;
615 if (Prev->valno == V2 && Prev->end == LR->start) {
618 // Erase this live-range.
625 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
626 // Ensure that it is a V2 live-range.
629 // If we can merge it into later V2 live ranges, do so now. We ignore any
630 // following V1 live ranges, as they will be merged in subsequent iterations
633 if (I->start == LR->end && I->valno == V2) {
641 // Now that V1 is dead, remove it.
642 markValNoForDeletion(V1);
647 void LiveInterval::Copy(const LiveInterval &RHS,
648 MachineRegisterInfo *MRI,
649 VNInfo::Allocator &VNInfoAllocator) {
652 std::pair<unsigned, unsigned> Hint = MRI->getRegAllocationHint(RHS.reg);
653 MRI->setRegAllocationHint(reg, Hint.first, Hint.second);
656 for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) {
657 const VNInfo *VNI = RHS.getValNumInfo(i);
658 createValueCopy(VNI, VNInfoAllocator);
660 for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) {
661 const LiveRange &LR = RHS.ranges[i];
662 addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id)));
666 unsigned LiveInterval::getSize() const {
668 for (const_iterator I = begin(), E = end(); I != E; ++I)
669 Sum += I->start.distance(I->end);
673 /// ComputeJoinedWeight - Set the weight of a live interval Joined
674 /// after Other has been merged into it.
675 void LiveInterval::ComputeJoinedWeight(const LiveInterval &Other) {
676 // If either of these intervals was spilled, the weight is the
677 // weight of the non-spilled interval. This can only happen with
678 // iterative coalescers.
680 if (Other.weight != HUGE_VALF) {
681 weight += Other.weight;
683 else if (weight == HUGE_VALF &&
684 !TargetRegisterInfo::isPhysicalRegister(reg)) {
685 // Remove this assert if you have an iterative coalescer
686 assert(0 && "Joining to spilled interval");
687 weight = Other.weight;
690 // Otherwise the weight stays the same
691 // Remove this assert if you have an iterative coalescer
692 assert(0 && "Joining from spilled interval");
696 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange &LR) {
697 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")";
700 void LiveRange::dump() const {
701 dbgs() << *this << "\n";
704 void LiveInterval::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const {
706 OS << "SS#" << getStackSlotIndex();
707 else if (TRI && TargetRegisterInfo::isPhysicalRegister(reg))
708 OS << TRI->getName(reg);
718 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
719 E = ranges.end(); I != E; ++I) {
721 assert(I->valno == getValNumInfo(I->valno->id) && "Bad VNInfo");
725 // Print value number info.
726 if (getNumValNums()) {
729 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
731 const VNInfo *vni = *i;
734 if (vni->isUnused()) {
737 if (!vni->isDefAccurate() && !vni->isPHIDef())
741 if (vni->hasPHIKill())
743 if (vni->hasRedefByEC())
750 void LiveInterval::dump() const {
751 dbgs() << *this << "\n";
755 void LiveRange::print(raw_ostream &os) const {