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' abd 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/ADT/SmallSet.h"
23 #include "llvm/ADT/STLExtras.h"
24 #include "llvm/Support/Streams.h"
25 #include "llvm/Target/TargetRegisterInfo.h"
30 // An example for liveAt():
32 // this = [1,4), liveAt(0) will return false. The instruction defining this
33 // spans slots [0,3]. The interval belongs to an spilled definition of the
34 // variable it represents. This is because slot 1 is used (def slot) and spans
35 // up to slot 3 (store slot).
37 bool LiveInterval::liveAt(unsigned I) const {
38 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
40 if (r == ranges.begin())
44 return r->contains(I);
47 // liveBeforeAndAt - Check if the interval is live at the index and the index
48 // just before it. If index is liveAt, check if it starts a new live range.
49 // If it does, then check if the previous live range ends at index-1.
50 bool LiveInterval::liveBeforeAndAt(unsigned I) const {
51 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
53 if (r == ranges.begin())
61 // I is the start of a live range. Check if the previous live range ends
63 if (r == ranges.begin())
68 // overlaps - Return true if the intersection of the two live intervals is
71 // An example for overlaps():
75 // 8: C = A + B ;; last use of A
77 // The live intervals should look like:
83 // A->overlaps(C) should return false since we want to be able to join
86 bool LiveInterval::overlapsFrom(const LiveInterval& other,
87 const_iterator StartPos) const {
88 const_iterator i = begin();
89 const_iterator ie = end();
90 const_iterator j = StartPos;
91 const_iterator je = other.end();
93 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
94 StartPos != other.end() && "Bogus start position hint!");
96 if (i->start < j->start) {
97 i = std::upper_bound(i, ie, j->start);
98 if (i != ranges.begin()) --i;
99 } else if (j->start < i->start) {
101 if (StartPos != other.end() && StartPos->start <= i->start) {
102 assert(StartPos < other.end() && i < end());
103 j = std::upper_bound(j, je, i->start);
104 if (j != other.ranges.begin()) --j;
110 if (j == je) return false;
113 if (i->start > j->start) {
118 if (i->end > j->start)
126 /// extendIntervalEndTo - This method is used when we want to extend the range
127 /// specified by I to end at the specified endpoint. To do this, we should
128 /// merge and eliminate all ranges that this will overlap with. The iterator is
130 void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) {
131 assert(I != ranges.end() && "Not a valid interval!");
132 VNInfo *ValNo = I->valno;
133 unsigned OldEnd = I->end;
135 // Search for the first interval that we can't merge with.
136 Ranges::iterator MergeTo = next(I);
137 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
138 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
141 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
142 I->end = std::max(NewEnd, prior(MergeTo)->end);
144 // Erase any dead ranges.
145 ranges.erase(next(I), MergeTo);
148 removeKills(ValNo, OldEnd, I->end-1);
150 // If the newly formed range now touches the range after it and if they have
151 // the same value number, merge the two ranges into one range.
152 Ranges::iterator Next = next(I);
153 if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) {
160 /// extendIntervalStartTo - This method is used when we want to extend the range
161 /// specified by I to start at the specified endpoint. To do this, we should
162 /// merge and eliminate all ranges that this will overlap with.
163 LiveInterval::Ranges::iterator
164 LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) {
165 assert(I != ranges.end() && "Not a valid interval!");
166 VNInfo *ValNo = I->valno;
168 // Search for the first interval that we can't merge with.
169 Ranges::iterator MergeTo = I;
171 if (MergeTo == ranges.begin()) {
173 ranges.erase(MergeTo, I);
176 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
178 } while (NewStart <= MergeTo->start);
180 // If we start in the middle of another interval, just delete a range and
181 // extend that interval.
182 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
183 MergeTo->end = I->end;
185 // Otherwise, extend the interval right after.
187 MergeTo->start = NewStart;
188 MergeTo->end = I->end;
191 ranges.erase(next(MergeTo), next(I));
195 LiveInterval::iterator
196 LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
197 unsigned Start = LR.start, End = LR.end;
198 iterator it = std::upper_bound(From, ranges.end(), Start);
200 // If the inserted interval starts in the middle or right at the end of
201 // another interval, just extend that interval to contain the range of LR.
202 if (it != ranges.begin()) {
203 iterator B = prior(it);
204 if (LR.valno == B->valno) {
205 if (B->start <= Start && B->end >= Start) {
206 extendIntervalEndTo(B, End);
210 // Check to make sure that we are not overlapping two live ranges with
211 // different valno's.
212 assert(B->end <= Start &&
213 "Cannot overlap two LiveRanges with differing ValID's"
214 " (did you def the same reg twice in a MachineInstr?)");
218 // Otherwise, if this range ends in the middle of, or right next to, another
219 // interval, merge it into that interval.
220 if (it != ranges.end())
221 if (LR.valno == it->valno) {
222 if (it->start <= End) {
223 it = extendIntervalStartTo(it, Start);
225 // If LR is a complete superset of an interval, we may need to grow its
228 extendIntervalEndTo(it, End);
229 else if (End < it->end)
230 // Overlapping intervals, there might have been a kill here.
231 removeKill(it->valno, End);
235 // Check to make sure that we are not overlapping two live ranges with
236 // different valno's.
237 assert(it->start >= End &&
238 "Cannot overlap two LiveRanges with differing ValID's");
241 // Otherwise, this is just a new range that doesn't interact with anything.
243 return ranges.insert(it, LR);
247 /// removeRange - Remove the specified range from this interval. Note that
248 /// the range must already be in this interval in its entirety.
249 void LiveInterval::removeRange(unsigned Start, unsigned End,
250 bool RemoveDeadValNo) {
251 // Find the LiveRange containing this span.
252 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
253 assert(I != ranges.begin() && "Range is not in interval!");
255 assert(I->contains(Start) && I->contains(End-1) &&
256 "Range is not entirely in interval!");
258 // If the span we are removing is at the start of the LiveRange, adjust it.
259 VNInfo *ValNo = I->valno;
260 if (I->start == Start) {
262 removeKills(I->valno, Start, End);
263 if (RemoveDeadValNo) {
264 // Check if val# is dead.
266 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
267 if (II != I && II->valno == ValNo) {
272 // Now that ValNo is dead, remove it. If it is the largest value
273 // number, just nuke it (and any other deleted values neighboring it),
274 // otherwise mark it as ~1U so it can be nuked later.
275 if (ValNo->id == getNumValNums()-1) {
277 VNInfo *VNI = valnos.back();
280 } while (!valnos.empty() && valnos.back()->def == ~1U);
287 ranges.erase(I); // Removed the whole LiveRange.
293 // Otherwise if the span we are removing is at the end of the LiveRange,
294 // adjust the other way.
296 removeKills(ValNo, Start, End);
301 // Otherwise, we are splitting the LiveRange into two pieces.
302 unsigned OldEnd = I->end;
303 I->end = Start; // Trim the old interval.
305 // Insert the new one.
306 ranges.insert(next(I), LiveRange(End, OldEnd, ValNo));
309 /// removeValNo - Remove all the ranges defined by the specified value#.
310 /// Also remove the value# from value# list.
311 void LiveInterval::removeValNo(VNInfo *ValNo) {
313 Ranges::iterator I = ranges.end();
314 Ranges::iterator E = ranges.begin();
317 if (I->valno == ValNo)
320 // Now that ValNo is dead, remove it. If it is the largest value
321 // number, just nuke it (and any other deleted values neighboring it),
322 // otherwise mark it as ~1U so it can be nuked later.
323 if (ValNo->id == getNumValNums()-1) {
325 VNInfo *VNI = valnos.back();
328 } while (!valnos.empty() && valnos.back()->def == ~1U);
334 /// getLiveRangeContaining - Return the live range that contains the
335 /// specified index, or null if there is none.
336 LiveInterval::const_iterator
337 LiveInterval::FindLiveRangeContaining(unsigned Idx) const {
338 const_iterator It = std::upper_bound(begin(), end(), Idx);
339 if (It != ranges.begin()) {
341 if (It->contains(Idx))
348 LiveInterval::iterator
349 LiveInterval::FindLiveRangeContaining(unsigned Idx) {
350 iterator It = std::upper_bound(begin(), end(), Idx);
353 if (It->contains(Idx))
360 /// join - Join two live intervals (this, and other) together. This applies
361 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
362 /// the intervals are not joinable, this aborts.
363 void LiveInterval::join(LiveInterval &Other, const int *LHSValNoAssignments,
364 const int *RHSValNoAssignments,
365 SmallVector<VNInfo*, 16> &NewVNInfo) {
366 // Determine if any of our live range values are mapped. This is uncommon, so
367 // we want to avoid the interval scan if not.
368 bool MustMapCurValNos = false;
369 unsigned NumVals = getNumValNums();
370 unsigned NumNewVals = NewVNInfo.size();
371 for (unsigned i = 0; i != NumVals; ++i) {
372 unsigned LHSValID = LHSValNoAssignments[i];
374 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i)))
375 MustMapCurValNos = true;
378 // If we have to apply a mapping to our base interval assignment, rewrite it
380 if (MustMapCurValNos) {
381 // Map the first live range.
382 iterator OutIt = begin();
383 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
385 for (iterator I = OutIt, E = end(); I != E; ++I) {
386 OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]];
388 // If this live range has the same value # as its immediate predecessor,
389 // and if they are neighbors, remove one LiveRange. This happens when we
390 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
391 if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) {
392 (OutIt-1)->end = OutIt->end;
395 OutIt->start = I->start;
399 // Didn't merge, on to the next one.
404 // If we merge some live ranges, chop off the end.
405 ranges.erase(OutIt, end());
408 // Remember assignements because val# ids are changing.
409 SmallVector<unsigned, 16> OtherAssignments;
410 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
411 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]);
413 // Update val# info. Renumber them and make sure they all belong to this
414 // LiveInterval now. Also remove dead val#'s.
415 unsigned NumValNos = 0;
416 for (unsigned i = 0; i < NumNewVals; ++i) {
417 VNInfo *VNI = NewVNInfo[i];
420 valnos.push_back(VNI);
422 valnos[NumValNos] = VNI;
423 VNI->id = NumValNos++; // Renumber val#.
426 if (NumNewVals < NumVals)
427 valnos.resize(NumNewVals); // shrinkify
429 // Okay, now insert the RHS live ranges into the LHS.
430 iterator InsertPos = begin();
431 unsigned RangeNo = 0;
432 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) {
433 // Map the valno in the other live range to the current live range.
434 I->valno = NewVNInfo[OtherAssignments[RangeNo]];
435 assert(I->valno && "Adding a dead range?");
436 InsertPos = addRangeFrom(*I, InsertPos);
439 weight += Other.weight;
440 if (Other.preference && !preference)
441 preference = Other.preference;
444 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
445 /// interval as the specified value number. The LiveRanges in RHS are
446 /// allowed to overlap with LiveRanges in the current interval, but only if
447 /// the overlapping LiveRanges have the specified value number.
448 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
450 // TODO: Make this more efficient.
451 iterator InsertPos = begin();
452 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
453 // Map the valno in the other live range to the current live range.
455 Tmp.valno = LHSValNo;
456 InsertPos = addRangeFrom(Tmp, InsertPos);
461 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
462 /// in RHS into this live interval as the specified value number.
463 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
464 /// current interval, it will replace the value numbers of the overlaped
465 /// live ranges with the specified value number.
466 void LiveInterval::MergeValueInAsValue(const LiveInterval &RHS,
467 const VNInfo *RHSValNo, VNInfo *LHSValNo) {
468 SmallVector<VNInfo*, 4> ReplacedValNos;
469 iterator IP = begin();
470 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
471 if (I->valno != RHSValNo)
473 unsigned Start = I->start, End = I->end;
474 IP = std::upper_bound(IP, end(), Start);
475 // If the start of this range overlaps with an existing liverange, trim it.
476 if (IP != begin() && IP[-1].end > Start) {
477 if (IP[-1].valno != LHSValNo) {
478 ReplacedValNos.push_back(IP[-1].valno);
479 IP[-1].valno = LHSValNo; // Update val#.
482 // Trimmed away the whole range?
483 if (Start >= End) continue;
485 // If the end of this range overlaps with an existing liverange, trim it.
486 if (IP != end() && End > IP->start) {
487 if (IP->valno != LHSValNo) {
488 ReplacedValNos.push_back(IP->valno);
489 IP->valno = LHSValNo; // Update val#.
492 // If this trimmed away the whole range, ignore it.
493 if (Start == End) continue;
496 // Map the valno in the other live range to the current live range.
497 IP = addRangeFrom(LiveRange(Start, End, LHSValNo), IP);
501 SmallSet<VNInfo*, 4> Seen;
502 for (unsigned i = 0, e = ReplacedValNos.size(); i != e; ++i) {
503 VNInfo *V1 = ReplacedValNos[i];
504 if (Seen.insert(V1)) {
506 for (const_iterator I = begin(), E = end(); I != E; ++I)
507 if (I->valno == V1) {
512 // Now that V1 is dead, remove it. If it is the largest value number,
513 // just nuke it (and any other deleted values neighboring it), otherwise
514 // mark it as ~1U so it can be nuked later.
515 if (V1->id == getNumValNums()-1) {
517 VNInfo *VNI = valnos.back();
520 } while (!valnos.empty() && valnos.back()->def == ~1U);
530 /// MergeInClobberRanges - For any live ranges that are not defined in the
531 /// current interval, but are defined in the Clobbers interval, mark them
532 /// used with an unknown definition value.
533 void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers,
534 BumpPtrAllocator &VNInfoAllocator) {
535 if (Clobbers.begin() == Clobbers.end()) return;
537 // Find a value # to use for the clobber ranges. If there is already a value#
538 // for unknown values, use it.
539 // FIXME: Use a single sentinal number for these!
540 VNInfo *ClobberValNo = getNextValue(~0U, 0, VNInfoAllocator);
542 iterator IP = begin();
543 for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) {
544 unsigned Start = I->start, End = I->end;
545 IP = std::upper_bound(IP, end(), Start);
547 // If the start of this range overlaps with an existing liverange, trim it.
548 if (IP != begin() && IP[-1].end > Start) {
550 // Trimmed away the whole range?
551 if (Start >= End) continue;
553 // If the end of this range overlaps with an existing liverange, trim it.
554 if (IP != end() && End > IP->start) {
556 // If this trimmed away the whole range, ignore it.
557 if (Start == End) continue;
560 // Insert the clobber interval.
561 IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP);
565 /// MergeValueNumberInto - This method is called when two value nubmers
566 /// are found to be equivalent. This eliminates V1, replacing all
567 /// LiveRanges with the V1 value number with the V2 value number. This can
568 /// cause merging of V1/V2 values numbers and compaction of the value space.
569 void LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
570 assert(V1 != V2 && "Identical value#'s are always equivalent!");
572 // This code actually merges the (numerically) larger value number into the
573 // smaller value number, which is likely to allow us to compactify the value
574 // space. The only thing we have to be careful of is to preserve the
575 // instruction that defines the result value.
577 // Make sure V2 is smaller than V1.
578 if (V1->id < V2->id) {
579 copyValNumInfo(V1, V2);
583 // Merge V1 live ranges into V2.
584 for (iterator I = begin(); I != end(); ) {
586 if (LR->valno != V1) continue; // Not a V1 LiveRange.
588 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
591 iterator Prev = LR-1;
592 if (Prev->valno == V2 && Prev->end == LR->start) {
595 // Erase this live-range.
602 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
603 // Ensure that it is a V2 live-range.
606 // If we can merge it into later V2 live ranges, do so now. We ignore any
607 // following V1 live ranges, as they will be merged in subsequent iterations
610 if (I->start == LR->end && I->valno == V2) {
618 // Now that V1 is dead, remove it. If it is the largest value number, just
619 // nuke it (and any other deleted values neighboring it), otherwise mark it as
620 // ~1U so it can be nuked later.
621 if (V1->id == getNumValNums()-1) {
623 VNInfo *VNI = valnos.back();
626 } while (valnos.back()->def == ~1U);
632 void LiveInterval::Copy(const LiveInterval &RHS,
633 BumpPtrAllocator &VNInfoAllocator) {
636 preference = RHS.preference;
638 for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) {
639 const VNInfo *VNI = RHS.getValNumInfo(i);
640 VNInfo *NewVNI = getNextValue(~0U, 0, VNInfoAllocator);
641 copyValNumInfo(NewVNI, VNI);
643 for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) {
644 const LiveRange &LR = RHS.ranges[i];
645 addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id)));
649 unsigned LiveInterval::getSize() const {
651 for (const_iterator I = begin(), E = end(); I != E; ++I)
652 Sum += I->end - I->start;
656 std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
657 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")";
660 void LiveRange::dump() const {
661 cerr << *this << "\n";
664 void LiveInterval::print(std::ostream &OS,
665 const TargetRegisterInfo *TRI) const {
666 if (TRI && TargetRegisterInfo::isPhysicalRegister(reg))
667 OS << TRI->getName(reg);
677 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
678 E = ranges.end(); I != E; ++I)
682 // Print value number info.
683 if (getNumValNums()) {
686 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
688 const VNInfo *vni = *i;
691 if (vni->def == ~1U) {
698 unsigned ee = vni->kills.size();
699 if (ee || vni->hasPHIKill) {
701 for (unsigned j = 0; j != ee; ++j) {
706 if (vni->hasPHIKill) {
718 void LiveInterval::dump() const {
719 cerr << *this << "\n";
723 void LiveRange::print(std::ostream &os) const {