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 // overlaps - Return true if the intersection of the two live intervals is
50 // An example for overlaps():
54 // 8: C = A + B ;; last use of A
56 // The live intervals should look like:
62 // A->overlaps(C) should return false since we want to be able to join
65 bool LiveInterval::overlapsFrom(const LiveInterval& other,
66 const_iterator StartPos) const {
67 const_iterator i = begin();
68 const_iterator ie = end();
69 const_iterator j = StartPos;
70 const_iterator je = other.end();
72 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
73 StartPos != other.end() && "Bogus start position hint!");
75 if (i->start < j->start) {
76 i = std::upper_bound(i, ie, j->start);
77 if (i != ranges.begin()) --i;
78 } else if (j->start < i->start) {
80 if (StartPos != other.end() && StartPos->start <= i->start) {
81 assert(StartPos < other.end() && i < end());
82 j = std::upper_bound(j, je, i->start);
83 if (j != other.ranges.begin()) --j;
89 if (j == je) return false;
92 if (i->start > j->start) {
97 if (i->end > j->start)
105 /// extendIntervalEndTo - This method is used when we want to extend the range
106 /// specified by I to end at the specified endpoint. To do this, we should
107 /// merge and eliminate all ranges that this will overlap with. The iterator is
109 void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) {
110 assert(I != ranges.end() && "Not a valid interval!");
111 VNInfo *ValNo = I->valno;
112 unsigned OldEnd = I->end;
114 // Search for the first interval that we can't merge with.
115 Ranges::iterator MergeTo = next(I);
116 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
117 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
120 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
121 I->end = std::max(NewEnd, prior(MergeTo)->end);
123 // Erase any dead ranges.
124 ranges.erase(next(I), MergeTo);
127 removeKills(ValNo, OldEnd, I->end-1);
129 // If the newly formed range now touches the range after it and if they have
130 // the same value number, merge the two ranges into one range.
131 Ranges::iterator Next = next(I);
132 if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) {
139 /// extendIntervalStartTo - This method is used when we want to extend the range
140 /// specified by I to start at the specified endpoint. To do this, we should
141 /// merge and eliminate all ranges that this will overlap with.
142 LiveInterval::Ranges::iterator
143 LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) {
144 assert(I != ranges.end() && "Not a valid interval!");
145 VNInfo *ValNo = I->valno;
147 // Search for the first interval that we can't merge with.
148 Ranges::iterator MergeTo = I;
150 if (MergeTo == ranges.begin()) {
152 ranges.erase(MergeTo, I);
155 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
157 } while (NewStart <= MergeTo->start);
159 // If we start in the middle of another interval, just delete a range and
160 // extend that interval.
161 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
162 MergeTo->end = I->end;
164 // Otherwise, extend the interval right after.
166 MergeTo->start = NewStart;
167 MergeTo->end = I->end;
170 ranges.erase(next(MergeTo), next(I));
174 LiveInterval::iterator
175 LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
176 unsigned Start = LR.start, End = LR.end;
177 iterator it = std::upper_bound(From, ranges.end(), Start);
179 // If the inserted interval starts in the middle or right at the end of
180 // another interval, just extend that interval to contain the range of LR.
181 if (it != ranges.begin()) {
182 iterator B = prior(it);
183 if (LR.valno == B->valno) {
184 if (B->start <= Start && B->end >= Start) {
185 extendIntervalEndTo(B, End);
189 // Check to make sure that we are not overlapping two live ranges with
190 // different valno's.
191 assert(B->end <= Start &&
192 "Cannot overlap two LiveRanges with differing ValID's"
193 " (did you def the same reg twice in a MachineInstr?)");
197 // Otherwise, if this range ends in the middle of, or right next to, another
198 // interval, merge it into that interval.
199 if (it != ranges.end())
200 if (LR.valno == it->valno) {
201 if (it->start <= End) {
202 it = extendIntervalStartTo(it, Start);
204 // If LR is a complete superset of an interval, we may need to grow its
207 extendIntervalEndTo(it, End);
208 else if (End < it->end)
209 // Overlapping intervals, there might have been a kill here.
210 removeKill(it->valno, End);
214 // Check to make sure that we are not overlapping two live ranges with
215 // different valno's.
216 assert(it->start >= End &&
217 "Cannot overlap two LiveRanges with differing ValID's");
220 // Otherwise, this is just a new range that doesn't interact with anything.
222 return ranges.insert(it, LR);
226 /// removeRange - Remove the specified range from this interval. Note that
227 /// the range must already be in this interval in its entirety.
228 void LiveInterval::removeRange(unsigned Start, unsigned End,
229 bool RemoveDeadValNo) {
230 // Find the LiveRange containing this span.
231 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
232 assert(I != ranges.begin() && "Range is not in interval!");
234 assert(I->contains(Start) && I->contains(End-1) &&
235 "Range is not entirely in interval!");
237 // If the span we are removing is at the start of the LiveRange, adjust it.
238 VNInfo *ValNo = I->valno;
239 if (I->start == Start) {
241 removeKills(I->valno, Start, End);
242 if (RemoveDeadValNo) {
243 // Check if val# is dead.
245 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
246 if (II != I && II->valno == ValNo) {
251 // Now that ValNo is dead, remove it. If it is the largest value
252 // number, just nuke it (and any other deleted values neighboring it),
253 // otherwise mark it as ~1U so it can be nuked later.
254 if (ValNo->id == getNumValNums()-1) {
256 VNInfo *VNI = valnos.back();
259 } while (!valnos.empty() && valnos.back()->def == ~1U);
266 ranges.erase(I); // Removed the whole LiveRange.
272 // Otherwise if the span we are removing is at the end of the LiveRange,
273 // adjust the other way.
275 removeKills(ValNo, Start, End);
280 // Otherwise, we are splitting the LiveRange into two pieces.
281 unsigned OldEnd = I->end;
282 I->end = Start; // Trim the old interval.
284 // Insert the new one.
285 ranges.insert(next(I), LiveRange(End, OldEnd, ValNo));
288 /// removeValNo - Remove all the ranges defined by the specified value#.
289 /// Also remove the value# from value# list.
290 void LiveInterval::removeValNo(VNInfo *ValNo) {
292 Ranges::iterator I = ranges.end();
293 Ranges::iterator E = ranges.begin();
296 if (I->valno == ValNo)
299 // Now that ValNo is dead, remove it. If it is the largest value
300 // number, just nuke it (and any other deleted values neighboring it),
301 // otherwise mark it as ~1U so it can be nuked later.
302 if (ValNo->id == getNumValNums()-1) {
304 VNInfo *VNI = valnos.back();
307 } while (!valnos.empty() && valnos.back()->def == ~1U);
313 /// getLiveRangeContaining - Return the live range that contains the
314 /// specified index, or null if there is none.
315 LiveInterval::const_iterator
316 LiveInterval::FindLiveRangeContaining(unsigned Idx) const {
317 const_iterator It = std::upper_bound(begin(), end(), Idx);
318 if (It != ranges.begin()) {
320 if (It->contains(Idx))
327 LiveInterval::iterator
328 LiveInterval::FindLiveRangeContaining(unsigned Idx) {
329 iterator It = std::upper_bound(begin(), end(), Idx);
332 if (It->contains(Idx))
339 /// join - Join two live intervals (this, and other) together. This applies
340 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
341 /// the intervals are not joinable, this aborts.
342 void LiveInterval::join(LiveInterval &Other, const int *LHSValNoAssignments,
343 const int *RHSValNoAssignments,
344 SmallVector<VNInfo*, 16> &NewVNInfo) {
345 // Determine if any of our live range values are mapped. This is uncommon, so
346 // we want to avoid the interval scan if not.
347 bool MustMapCurValNos = false;
348 unsigned NumVals = getNumValNums();
349 unsigned NumNewVals = NewVNInfo.size();
350 for (unsigned i = 0; i != NumVals; ++i) {
351 unsigned LHSValID = LHSValNoAssignments[i];
353 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i)))
354 MustMapCurValNos = true;
357 // If we have to apply a mapping to our base interval assignment, rewrite it
359 if (MustMapCurValNos) {
360 // Map the first live range.
361 iterator OutIt = begin();
362 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
364 for (iterator I = OutIt, E = end(); I != E; ++I) {
365 OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]];
367 // If this live range has the same value # as its immediate predecessor,
368 // and if they are neighbors, remove one LiveRange. This happens when we
369 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
370 if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) {
371 (OutIt-1)->end = OutIt->end;
374 OutIt->start = I->start;
378 // Didn't merge, on to the next one.
383 // If we merge some live ranges, chop off the end.
384 ranges.erase(OutIt, end());
387 // Remember assignements because val# ids are changing.
388 SmallVector<unsigned, 16> OtherAssignments;
389 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
390 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]);
392 // Update val# info. Renumber them and make sure they all belong to this
393 // LiveInterval now. Also remove dead val#'s.
394 unsigned NumValNos = 0;
395 for (unsigned i = 0; i < NumNewVals; ++i) {
396 VNInfo *VNI = NewVNInfo[i];
399 valnos.push_back(VNI);
401 valnos[NumValNos] = VNI;
402 VNI->id = NumValNos++; // Renumber val#.
405 if (NumNewVals < NumVals)
406 valnos.resize(NumNewVals); // shrinkify
408 // Okay, now insert the RHS live ranges into the LHS.
409 iterator InsertPos = begin();
410 unsigned RangeNo = 0;
411 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) {
412 // Map the valno in the other live range to the current live range.
413 I->valno = NewVNInfo[OtherAssignments[RangeNo]];
414 assert(I->valno && "Adding a dead range?");
415 InsertPos = addRangeFrom(*I, InsertPos);
418 weight += Other.weight;
419 if (Other.preference && !preference)
420 preference = Other.preference;
423 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
424 /// interval as the specified value number. The LiveRanges in RHS are
425 /// allowed to overlap with LiveRanges in the current interval, but only if
426 /// the overlapping LiveRanges have the specified value number.
427 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
429 // TODO: Make this more efficient.
430 iterator InsertPos = begin();
431 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
432 // Map the valno in the other live range to the current live range.
434 Tmp.valno = LHSValNo;
435 InsertPos = addRangeFrom(Tmp, InsertPos);
440 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
441 /// in RHS into this live interval as the specified value number.
442 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
443 /// current interval, it will replace the value numbers of the overlaped
444 /// live ranges with the specified value number.
445 void LiveInterval::MergeValueInAsValue(const LiveInterval &RHS,
446 const VNInfo *RHSValNo, VNInfo *LHSValNo) {
447 SmallVector<VNInfo*, 4> ReplacedValNos;
448 iterator IP = begin();
449 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
450 if (I->valno != RHSValNo)
452 unsigned Start = I->start, End = I->end;
453 IP = std::upper_bound(IP, end(), Start);
454 // If the start of this range overlaps with an existing liverange, trim it.
455 if (IP != begin() && IP[-1].end > Start) {
456 if (IP[-1].valno != LHSValNo) {
457 ReplacedValNos.push_back(IP[-1].valno);
458 IP[-1].valno = LHSValNo; // Update val#.
461 // Trimmed away the whole range?
462 if (Start >= End) continue;
464 // If the end of this range overlaps with an existing liverange, trim it.
465 if (IP != end() && End > IP->start) {
466 if (IP->valno != LHSValNo) {
467 ReplacedValNos.push_back(IP->valno);
468 IP->valno = LHSValNo; // Update val#.
471 // If this trimmed away the whole range, ignore it.
472 if (Start == End) continue;
475 // Map the valno in the other live range to the current live range.
476 IP = addRangeFrom(LiveRange(Start, End, LHSValNo), IP);
480 SmallSet<VNInfo*, 4> Seen;
481 for (unsigned i = 0, e = ReplacedValNos.size(); i != e; ++i) {
482 VNInfo *V1 = ReplacedValNos[i];
483 if (Seen.insert(V1)) {
485 for (const_iterator I = begin(), E = end(); I != E; ++I)
486 if (I->valno == V1) {
491 // Now that V1 is dead, remove it. If it is the largest value number,
492 // just nuke it (and any other deleted values neighboring it), otherwise
493 // mark it as ~1U so it can be nuked later.
494 if (V1->id == getNumValNums()-1) {
496 VNInfo *VNI = valnos.back();
499 } while (!valnos.empty() && valnos.back()->def == ~1U);
509 /// MergeInClobberRanges - For any live ranges that are not defined in the
510 /// current interval, but are defined in the Clobbers interval, mark them
511 /// used with an unknown definition value.
512 void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers,
513 BumpPtrAllocator &VNInfoAllocator) {
514 if (Clobbers.begin() == Clobbers.end()) return;
516 // Find a value # to use for the clobber ranges. If there is already a value#
517 // for unknown values, use it.
518 // FIXME: Use a single sentinal number for these!
519 VNInfo *ClobberValNo = getNextValue(~0U, 0, VNInfoAllocator);
521 iterator IP = begin();
522 for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) {
523 unsigned Start = I->start, End = I->end;
524 IP = std::upper_bound(IP, end(), Start);
526 // If the start of this range overlaps with an existing liverange, trim it.
527 if (IP != begin() && IP[-1].end > Start) {
529 // Trimmed away the whole range?
530 if (Start >= End) continue;
532 // If the end of this range overlaps with an existing liverange, trim it.
533 if (IP != end() && End > IP->start) {
535 // If this trimmed away the whole range, ignore it.
536 if (Start == End) continue;
539 // Insert the clobber interval.
540 IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP);
544 /// MergeValueNumberInto - This method is called when two value nubmers
545 /// are found to be equivalent. This eliminates V1, replacing all
546 /// LiveRanges with the V1 value number with the V2 value number. This can
547 /// cause merging of V1/V2 values numbers and compaction of the value space.
548 void LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
549 assert(V1 != V2 && "Identical value#'s are always equivalent!");
551 // This code actually merges the (numerically) larger value number into the
552 // smaller value number, which is likely to allow us to compactify the value
553 // space. The only thing we have to be careful of is to preserve the
554 // instruction that defines the result value.
556 // Make sure V2 is smaller than V1.
557 if (V1->id < V2->id) {
558 copyValNumInfo(V1, V2);
562 // Merge V1 live ranges into V2.
563 for (iterator I = begin(); I != end(); ) {
565 if (LR->valno != V1) continue; // Not a V1 LiveRange.
567 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
570 iterator Prev = LR-1;
571 if (Prev->valno == V2 && Prev->end == LR->start) {
574 // Erase this live-range.
581 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
582 // Ensure that it is a V2 live-range.
585 // If we can merge it into later V2 live ranges, do so now. We ignore any
586 // following V1 live ranges, as they will be merged in subsequent iterations
589 if (I->start == LR->end && I->valno == V2) {
597 // Now that V1 is dead, remove it. If it is the largest value number, just
598 // nuke it (and any other deleted values neighboring it), otherwise mark it as
599 // ~1U so it can be nuked later.
600 if (V1->id == getNumValNums()-1) {
602 VNInfo *VNI = valnos.back();
605 } while (valnos.back()->def == ~1U);
611 void LiveInterval::Copy(const LiveInterval &RHS,
612 BumpPtrAllocator &VNInfoAllocator) {
615 preference = RHS.preference;
617 for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) {
618 const VNInfo *VNI = RHS.getValNumInfo(i);
619 VNInfo *NewVNI = getNextValue(~0U, 0, VNInfoAllocator);
620 copyValNumInfo(NewVNI, VNI);
622 for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) {
623 const LiveRange &LR = RHS.ranges[i];
624 addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id)));
628 unsigned LiveInterval::getSize() const {
630 for (const_iterator I = begin(), E = end(); I != E; ++I)
631 Sum += I->end - I->start;
635 std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
636 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")";
639 void LiveRange::dump() const {
640 cerr << *this << "\n";
643 void LiveInterval::print(std::ostream &OS,
644 const TargetRegisterInfo *TRI) const {
645 if (TRI && TargetRegisterInfo::isPhysicalRegister(reg))
646 OS << TRI->getName(reg);
656 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
657 E = ranges.end(); I != E; ++I)
661 // Print value number info.
662 if (getNumValNums()) {
665 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
667 const VNInfo *vni = *i;
670 if (vni->def == ~1U) {
677 unsigned ee = vni->kills.size();
678 if (ee || vni->hasPHIKill) {
680 for (unsigned j = 0; j != ee; ++j) {
685 if (vni->hasPHIKill) {
697 void LiveInterval::dump() const {
698 cerr << *this << "\n";
702 void LiveRange::print(std::ostream &os) const {