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 LiveInterval::iterator LiveInterval::find(SlotIndex Pos) {
34 // This algorithm is basically std::upper_bound.
35 // Unfortunately, std::upper_bound cannot be used with mixed types until we
36 // adopt C++0x. Many libraries can do it, but not all.
37 if (empty() || Pos >= endIndex())
40 size_t Len = ranges.size();
42 size_t Mid = Len >> 1;
46 I += Mid + 1, Len -= Mid + 1;
51 VNInfo *LiveInterval::createDeadDef(SlotIndex Def,
52 VNInfo::Allocator &VNInfoAllocator) {
53 assert(!Def.isDead() && "Cannot define a value at the dead slot");
54 iterator I = find(Def);
56 VNInfo *VNI = getNextValue(Def, VNInfoAllocator);
57 ranges.push_back(LiveRange(Def, Def.getDeadSlot(), VNI));
60 if (SlotIndex::isSameInstr(Def, I->start)) {
61 assert(I->start == Def && "Cannot insert def, already live");
62 assert(I->valno->def == Def && "Inconsistent existing value def");
65 assert(SlotIndex::isEarlierInstr(Def, I->start) && "Already live at def");
66 VNInfo *VNI = getNextValue(Def, VNInfoAllocator);
67 ranges.insert(I, LiveRange(Def, Def.getDeadSlot(), VNI));
71 /// killedInRange - Return true if the interval has kills in [Start,End).
72 bool LiveInterval::killedInRange(SlotIndex Start, SlotIndex End) const {
73 Ranges::const_iterator r =
74 std::lower_bound(ranges.begin(), ranges.end(), End);
76 // Now r points to the first interval with start >= End, or ranges.end().
77 if (r == ranges.begin())
81 // Now r points to the last interval with end <= End.
82 // r->end is the kill point.
83 return r->end >= Start && r->end < End;
86 // overlaps - Return true if the intersection of the two live intervals is
89 // An example for overlaps():
93 // 8: C = A + B ;; last use of A
95 // The live intervals should look like:
101 // A->overlaps(C) should return false since we want to be able to join
104 bool LiveInterval::overlapsFrom(const LiveInterval& other,
105 const_iterator StartPos) const {
106 assert(!empty() && "empty interval");
107 const_iterator i = begin();
108 const_iterator ie = end();
109 const_iterator j = StartPos;
110 const_iterator je = other.end();
112 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
113 StartPos != other.end() && "Bogus start position hint!");
115 if (i->start < j->start) {
116 i = std::upper_bound(i, ie, j->start);
117 if (i != ranges.begin()) --i;
118 } else if (j->start < i->start) {
120 if (StartPos != other.end() && StartPos->start <= i->start) {
121 assert(StartPos < other.end() && i < end());
122 j = std::upper_bound(j, je, i->start);
123 if (j != other.ranges.begin()) --j;
129 if (j == je) return false;
132 if (i->start > j->start) {
137 if (i->end > j->start)
145 /// overlaps - Return true if the live interval overlaps a range specified
147 bool LiveInterval::overlaps(SlotIndex Start, SlotIndex End) const {
148 assert(Start < End && "Invalid range");
149 const_iterator I = std::lower_bound(begin(), end(), End);
150 return I != begin() && (--I)->end > Start;
154 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
155 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
156 /// it can be nuked later.
157 void LiveInterval::markValNoForDeletion(VNInfo *ValNo) {
158 if (ValNo->id == getNumValNums()-1) {
161 } while (!valnos.empty() && valnos.back()->isUnused());
163 ValNo->setIsUnused(true);
167 /// RenumberValues - Renumber all values in order of appearance and delete the
168 /// remaining unused values.
169 void LiveInterval::RenumberValues(LiveIntervals &lis) {
170 SmallPtrSet<VNInfo*, 8> Seen;
172 for (const_iterator I = begin(), E = end(); I != E; ++I) {
173 VNInfo *VNI = I->valno;
174 if (!Seen.insert(VNI))
176 assert(!VNI->isUnused() && "Unused valno used by live range");
177 VNI->id = (unsigned)valnos.size();
178 valnos.push_back(VNI);
182 /// extendIntervalEndTo - This method is used when we want to extend the range
183 /// specified by I to end at the specified endpoint. To do this, we should
184 /// merge and eliminate all ranges that this will overlap with. The iterator is
186 void LiveInterval::extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd) {
187 assert(I != ranges.end() && "Not a valid interval!");
188 VNInfo *ValNo = I->valno;
190 // Search for the first interval that we can't merge with.
191 Ranges::iterator MergeTo = llvm::next(I);
192 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
193 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
196 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
197 I->end = std::max(NewEnd, prior(MergeTo)->end);
199 // Erase any dead ranges.
200 ranges.erase(llvm::next(I), MergeTo);
202 // If the newly formed range now touches the range after it and if they have
203 // the same value number, merge the two ranges into one range.
204 Ranges::iterator Next = llvm::next(I);
205 if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) {
212 /// extendIntervalStartTo - This method is used when we want to extend the range
213 /// specified by I to start at the specified endpoint. To do this, we should
214 /// merge and eliminate all ranges that this will overlap with.
215 LiveInterval::Ranges::iterator
216 LiveInterval::extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStart) {
217 assert(I != ranges.end() && "Not a valid interval!");
218 VNInfo *ValNo = I->valno;
220 // Search for the first interval that we can't merge with.
221 Ranges::iterator MergeTo = I;
223 if (MergeTo == ranges.begin()) {
225 ranges.erase(MergeTo, I);
228 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
230 } while (NewStart <= MergeTo->start);
232 // If we start in the middle of another interval, just delete a range and
233 // extend that interval.
234 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
235 MergeTo->end = I->end;
237 // Otherwise, extend the interval right after.
239 MergeTo->start = NewStart;
240 MergeTo->end = I->end;
243 ranges.erase(llvm::next(MergeTo), llvm::next(I));
247 LiveInterval::iterator
248 LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
249 SlotIndex Start = LR.start, End = LR.end;
250 iterator it = std::upper_bound(From, ranges.end(), Start);
252 // If the inserted interval starts in the middle or right at the end of
253 // another interval, just extend that interval to contain the range of LR.
254 if (it != ranges.begin()) {
255 iterator B = prior(it);
256 if (LR.valno == B->valno) {
257 if (B->start <= Start && B->end >= Start) {
258 extendIntervalEndTo(B, End);
262 // Check to make sure that we are not overlapping two live ranges with
263 // different valno's.
264 assert(B->end <= Start &&
265 "Cannot overlap two LiveRanges with differing ValID's"
266 " (did you def the same reg twice in a MachineInstr?)");
270 // Otherwise, if this range ends in the middle of, or right next to, another
271 // interval, merge it into that interval.
272 if (it != ranges.end()) {
273 if (LR.valno == it->valno) {
274 if (it->start <= End) {
275 it = extendIntervalStartTo(it, Start);
277 // If LR is a complete superset of an interval, we may need to grow its
280 extendIntervalEndTo(it, End);
284 // Check to make sure that we are not overlapping two live ranges with
285 // different valno's.
286 assert(it->start >= End &&
287 "Cannot overlap two LiveRanges with differing ValID's");
291 // Otherwise, this is just a new range that doesn't interact with anything.
293 return ranges.insert(it, LR);
296 /// extendInBlock - If this interval is live before Kill in the basic
297 /// block that starts at StartIdx, extend it to be live up to Kill and return
298 /// the value. If there is no live range before Kill, return NULL.
299 VNInfo *LiveInterval::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
302 iterator I = std::upper_bound(begin(), end(), Kill.getPrevSlot());
306 if (I->end <= StartIdx)
309 extendIntervalEndTo(I, Kill);
313 /// removeRange - Remove the specified range from this interval. Note that
314 /// the range must be in a single LiveRange in its entirety.
315 void LiveInterval::removeRange(SlotIndex Start, SlotIndex End,
316 bool RemoveDeadValNo) {
317 // Find the LiveRange containing this span.
318 Ranges::iterator I = find(Start);
319 assert(I != ranges.end() && "Range is not in interval!");
320 assert(I->containsRange(Start, End) && "Range is not entirely in interval!");
322 // If the span we are removing is at the start of the LiveRange, adjust it.
323 VNInfo *ValNo = I->valno;
324 if (I->start == Start) {
326 if (RemoveDeadValNo) {
327 // Check if val# is dead.
329 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
330 if (II != I && II->valno == ValNo) {
335 // Now that ValNo is dead, remove it.
336 markValNoForDeletion(ValNo);
340 ranges.erase(I); // Removed the whole LiveRange.
346 // Otherwise if the span we are removing is at the end of the LiveRange,
347 // adjust the other way.
353 // Otherwise, we are splitting the LiveRange into two pieces.
354 SlotIndex OldEnd = I->end;
355 I->end = Start; // Trim the old interval.
357 // Insert the new one.
358 ranges.insert(llvm::next(I), LiveRange(End, OldEnd, ValNo));
361 /// removeValNo - Remove all the ranges defined by the specified value#.
362 /// Also remove the value# from value# list.
363 void LiveInterval::removeValNo(VNInfo *ValNo) {
365 Ranges::iterator I = ranges.end();
366 Ranges::iterator E = ranges.begin();
369 if (I->valno == ValNo)
372 // Now that ValNo is dead, remove it.
373 markValNoForDeletion(ValNo);
376 /// join - Join two live intervals (this, and other) together. This applies
377 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
378 /// the intervals are not joinable, this aborts.
379 void LiveInterval::join(LiveInterval &Other,
380 const int *LHSValNoAssignments,
381 const int *RHSValNoAssignments,
382 SmallVector<VNInfo*, 16> &NewVNInfo,
383 MachineRegisterInfo *MRI) {
384 // Determine if any of our live range values are mapped. This is uncommon, so
385 // we want to avoid the interval scan if not.
386 bool MustMapCurValNos = false;
387 unsigned NumVals = getNumValNums();
388 unsigned NumNewVals = NewVNInfo.size();
389 for (unsigned i = 0; i != NumVals; ++i) {
390 unsigned LHSValID = LHSValNoAssignments[i];
392 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
393 MustMapCurValNos = true;
398 // If we have to apply a mapping to our base interval assignment, rewrite it
400 if (MustMapCurValNos) {
401 // Map the first live range.
403 iterator OutIt = begin();
404 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
405 for (iterator I = next(OutIt), E = end(); I != E; ++I) {
406 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
407 assert(nextValNo != 0 && "Huh?");
409 // If this live range has the same value # as its immediate predecessor,
410 // and if they are neighbors, remove one LiveRange. This happens when we
411 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
412 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
415 // Didn't merge. Move OutIt to the next interval,
417 OutIt->valno = nextValNo;
419 OutIt->start = I->start;
424 // If we merge some live ranges, chop off the end.
426 ranges.erase(OutIt, end());
429 // Remember assignements because val# ids are changing.
430 SmallVector<unsigned, 16> OtherAssignments;
431 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
432 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]);
434 // Update val# info. Renumber them and make sure they all belong to this
435 // LiveInterval now. Also remove dead val#'s.
436 unsigned NumValNos = 0;
437 for (unsigned i = 0; i < NumNewVals; ++i) {
438 VNInfo *VNI = NewVNInfo[i];
440 if (NumValNos >= NumVals)
441 valnos.push_back(VNI);
443 valnos[NumValNos] = VNI;
444 VNI->id = NumValNos++; // Renumber val#.
447 if (NumNewVals < NumVals)
448 valnos.resize(NumNewVals); // shrinkify
450 // Okay, now insert the RHS live ranges into the LHS.
451 iterator InsertPos = begin();
452 unsigned RangeNo = 0;
453 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) {
454 // Map the valno in the other live range to the current live range.
455 I->valno = NewVNInfo[OtherAssignments[RangeNo]];
456 assert(I->valno && "Adding a dead range?");
457 InsertPos = addRangeFrom(*I, InsertPos);
461 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
462 /// interval as the specified value number. The LiveRanges in RHS are
463 /// allowed to overlap with LiveRanges in the current interval, but only if
464 /// the overlapping LiveRanges have the specified value number.
465 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
467 // TODO: Make this more efficient.
468 iterator InsertPos = begin();
469 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
470 // Map the valno in the other live range to the current live range.
472 Tmp.valno = LHSValNo;
473 InsertPos = addRangeFrom(Tmp, InsertPos);
478 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
479 /// in RHS into this live interval as the specified value number.
480 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
481 /// current interval, it will replace the value numbers of the overlaped
482 /// live ranges with the specified value number.
483 void LiveInterval::MergeValueInAsValue(
484 const LiveInterval &RHS,
485 const VNInfo *RHSValNo, VNInfo *LHSValNo) {
486 // TODO: Make this more efficient.
487 iterator InsertPos = begin();
488 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
489 if (I->valno != RHSValNo)
491 // Map the valno in the other live range to the current live range.
493 Tmp.valno = LHSValNo;
494 InsertPos = addRangeFrom(Tmp, InsertPos);
499 /// MergeValueNumberInto - This method is called when two value nubmers
500 /// are found to be equivalent. This eliminates V1, replacing all
501 /// LiveRanges with the V1 value number with the V2 value number. This can
502 /// cause merging of V1/V2 values numbers and compaction of the value space.
503 VNInfo* LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
504 assert(V1 != V2 && "Identical value#'s are always equivalent!");
506 // This code actually merges the (numerically) larger value number into the
507 // smaller value number, which is likely to allow us to compactify the value
508 // space. The only thing we have to be careful of is to preserve the
509 // instruction that defines the result value.
511 // Make sure V2 is smaller than V1.
512 if (V1->id < V2->id) {
517 // Merge V1 live ranges into V2.
518 for (iterator I = begin(); I != end(); ) {
520 if (LR->valno != V1) continue; // Not a V1 LiveRange.
522 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
525 iterator Prev = LR-1;
526 if (Prev->valno == V2 && Prev->end == LR->start) {
529 // Erase this live-range.
536 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
537 // Ensure that it is a V2 live-range.
540 // If we can merge it into later V2 live ranges, do so now. We ignore any
541 // following V1 live ranges, as they will be merged in subsequent iterations
544 if (I->start == LR->end && I->valno == V2) {
552 // Merge the relevant flags.
555 // Now that V1 is dead, remove it.
556 markValNoForDeletion(V1);
561 void LiveInterval::Copy(const LiveInterval &RHS,
562 MachineRegisterInfo *MRI,
563 VNInfo::Allocator &VNInfoAllocator) {
566 std::pair<unsigned, unsigned> Hint = MRI->getRegAllocationHint(RHS.reg);
567 MRI->setRegAllocationHint(reg, Hint.first, Hint.second);
570 for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) {
571 const VNInfo *VNI = RHS.getValNumInfo(i);
572 createValueCopy(VNI, VNInfoAllocator);
574 for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) {
575 const LiveRange &LR = RHS.ranges[i];
576 addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id)));
580 unsigned LiveInterval::getSize() const {
582 for (const_iterator I = begin(), E = end(); I != E; ++I)
583 Sum += I->start.distance(I->end);
587 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange &LR) {
588 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")";
591 void LiveRange::dump() const {
592 dbgs() << *this << "\n";
595 void LiveInterval::print(raw_ostream &OS) const {
599 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
600 E = ranges.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()) {
621 if (vni->hasPHIKill())
628 void LiveInterval::dump() const {
629 dbgs() << *this << "\n";
633 void LiveRange::print(raw_ostream &os) const {
637 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
638 // Create initial equivalence classes.
640 EqClass.grow(LI->getNumValNums());
642 const VNInfo *used = 0, *unused = 0;
644 // Determine connections.
645 for (LiveInterval::const_vni_iterator I = LI->vni_begin(), E = LI->vni_end();
647 const VNInfo *VNI = *I;
648 // Group all unused values into one class.
649 if (VNI->isUnused()) {
651 EqClass.join(unused->id, VNI->id);
656 if (VNI->isPHIDef()) {
657 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
658 assert(MBB && "Phi-def has no defining MBB");
659 // Connect to values live out of predecessors.
660 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
661 PE = MBB->pred_end(); PI != PE; ++PI)
662 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
663 EqClass.join(VNI->id, PVNI->id);
665 // Normal value defined by an instruction. Check for two-addr redef.
666 // FIXME: This could be coincidental. Should we really check for a tied
667 // operand constraint?
668 // Note that VNI->def may be a use slot for an early clobber def.
669 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
670 EqClass.join(VNI->id, UVNI->id);
674 // Lump all the unused values in with the last used value.
676 EqClass.join(used->id, unused->id);
679 return EqClass.getNumClasses();
682 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
683 MachineRegisterInfo &MRI) {
684 assert(LIV[0] && "LIV[0] must be set");
685 LiveInterval &LI = *LIV[0];
687 // Rewrite instructions.
688 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
689 RE = MRI.reg_end(); RI != RE;) {
690 MachineOperand &MO = RI.getOperand();
691 MachineInstr *MI = MO.getParent();
693 if (MO.isUse() && MO.isUndef())
695 // DBG_VALUE instructions should have been eliminated earlier.
696 SlotIndex Idx = LIS.getInstructionIndex(MI);
697 Idx = Idx.getRegSlot(MO.isUse());
698 const VNInfo *VNI = LI.getVNInfoAt(Idx);
699 // FIXME: We should be able to assert(VNI) here, but the coalescer leaves
700 // dangling defs around.
703 MO.setReg(LIV[getEqClass(VNI)]->reg);
706 // Move runs to new intervals.
707 LiveInterval::iterator J = LI.begin(), E = LI.end();
708 while (J != E && EqClass[J->valno->id] == 0)
710 for (LiveInterval::iterator I = J; I != E; ++I) {
711 if (unsigned eq = EqClass[I->valno->id]) {
712 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
713 "New intervals should be empty");
714 LIV[eq]->ranges.push_back(*I);
718 LI.ranges.erase(J, E);
720 // Transfer VNInfos to their new owners and renumber them.
721 unsigned j = 0, e = LI.getNumValNums();
722 while (j != e && EqClass[j] == 0)
724 for (unsigned i = j; i != e; ++i) {
725 VNInfo *VNI = LI.getValNumInfo(i);
726 if (unsigned eq = EqClass[i]) {
727 VNI->id = LIV[eq]->getNumValNums();
728 LIV[eq]->valnos.push_back(VNI);
731 LI.valnos[j++] = VNI;