1 //===-- LiveInterval.cpp - Live Interval Representation -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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/MRegisterInfo.h"
31 // An example for liveAt():
33 // this = [1,4), liveAt(0) will return false. The instruction defining this
34 // spans slots [0,3]. The interval belongs to an spilled definition of the
35 // variable it represents. This is because slot 1 is used (def slot) and spans
36 // up to slot 3 (store slot).
38 bool LiveInterval::liveAt(unsigned I) const {
39 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
41 if (r == ranges.begin())
45 return r->contains(I);
48 // overlaps - Return true if the intersection of the two live intervals is
51 // An example for overlaps():
55 // 8: C = A + B ;; last use of A
57 // The live intervals should look like:
63 // A->overlaps(C) should return false since we want to be able to join
66 bool LiveInterval::overlapsFrom(const LiveInterval& other,
67 const_iterator StartPos) const {
68 const_iterator i = begin();
69 const_iterator ie = end();
70 const_iterator j = StartPos;
71 const_iterator je = other.end();
73 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
74 StartPos != other.end() && "Bogus start position hint!");
76 if (i->start < j->start) {
77 i = std::upper_bound(i, ie, j->start);
78 if (i != ranges.begin()) --i;
79 } else if (j->start < i->start) {
81 if (StartPos != other.end() && StartPos->start <= i->start) {
82 assert(StartPos < other.end() && i < end());
83 j = std::upper_bound(j, je, i->start);
84 if (j != other.ranges.begin()) --j;
90 if (j == je) return false;
93 if (i->start > j->start) {
98 if (i->end > j->start)
106 /// extendIntervalEndTo - This method is used when we want to extend the range
107 /// specified by I to end at the specified endpoint. To do this, we should
108 /// merge and eliminate all ranges that this will overlap with. The iterator is
110 void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) {
111 assert(I != ranges.end() && "Not a valid interval!");
112 VNInfo *ValNo = I->valno;
113 unsigned OldEnd = I->end;
115 // Search for the first interval that we can't merge with.
116 Ranges::iterator MergeTo = next(I);
117 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
118 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
121 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
122 I->end = std::max(NewEnd, prior(MergeTo)->end);
124 // Erase any dead ranges.
125 ranges.erase(next(I), MergeTo);
128 removeKills(ValNo, OldEnd, I->end-1);
130 // If the newly formed range now touches the range after it and if they have
131 // the same value number, merge the two ranges into one range.
132 Ranges::iterator Next = next(I);
133 if (Next != ranges.end() && Next->start <= I->end && Next->valno == ValNo) {
140 /// extendIntervalStartTo - This method is used when we want to extend the range
141 /// specified by I to start at the specified endpoint. To do this, we should
142 /// merge and eliminate all ranges that this will overlap with.
143 LiveInterval::Ranges::iterator
144 LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) {
145 assert(I != ranges.end() && "Not a valid interval!");
146 VNInfo *ValNo = I->valno;
148 // Search for the first interval that we can't merge with.
149 Ranges::iterator MergeTo = I;
151 if (MergeTo == ranges.begin()) {
153 ranges.erase(MergeTo, I);
156 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
158 } while (NewStart <= MergeTo->start);
160 // If we start in the middle of another interval, just delete a range and
161 // extend that interval.
162 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
163 MergeTo->end = I->end;
165 // Otherwise, extend the interval right after.
167 MergeTo->start = NewStart;
168 MergeTo->end = I->end;
171 ranges.erase(next(MergeTo), next(I));
175 LiveInterval::iterator
176 LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
177 unsigned Start = LR.start, End = LR.end;
178 iterator it = std::upper_bound(From, ranges.end(), Start);
180 // If the inserted interval starts in the middle or right at the end of
181 // another interval, just extend that interval to contain the range of LR.
182 if (it != ranges.begin()) {
183 iterator B = prior(it);
184 if (LR.valno == B->valno) {
185 if (B->start <= Start && B->end >= Start) {
186 extendIntervalEndTo(B, End);
190 // Check to make sure that we are not overlapping two live ranges with
191 // different valno's.
192 assert(B->end <= Start &&
193 "Cannot overlap two LiveRanges with differing ValID's"
194 " (did you def the same reg twice in a MachineInstr?)");
198 // Otherwise, if this range ends in the middle of, or right next to, another
199 // interval, merge it into that interval.
200 if (it != ranges.end())
201 if (LR.valno == it->valno) {
202 if (it->start <= End) {
203 it = extendIntervalStartTo(it, Start);
205 // If LR is a complete superset of an interval, we may need to grow its
208 extendIntervalEndTo(it, End);
212 // Check to make sure that we are not overlapping two live ranges with
213 // different valno's.
214 assert(it->start >= End &&
215 "Cannot overlap two LiveRanges with differing ValID's");
218 // Otherwise, this is just a new range that doesn't interact with anything.
220 return ranges.insert(it, LR);
224 /// removeRange - Remove the specified range from this interval. Note that
225 /// the range must already be in this interval in its entirety.
226 void LiveInterval::removeRange(unsigned Start, unsigned End) {
227 // Find the LiveRange containing this span.
228 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
229 assert(I != ranges.begin() && "Range is not in interval!");
231 assert(I->contains(Start) && I->contains(End-1) &&
232 "Range is not entirely in interval!");
234 // If the span we are removing is at the start of the LiveRange, adjust it.
235 if (I->start == Start) {
237 removeKills(I->valno, Start, End);
238 ranges.erase(I); // Removed the whole LiveRange.
244 // Otherwise if the span we are removing is at the end of the LiveRange,
245 // adjust the other way.
247 removeKills(I->valno, Start, End);
252 // Otherwise, we are splitting the LiveRange into two pieces.
253 unsigned OldEnd = I->end;
254 I->end = Start; // Trim the old interval.
256 // Insert the new one.
257 ranges.insert(next(I), LiveRange(End, OldEnd, I->valno));
260 /// getLiveRangeContaining - Return the live range that contains the
261 /// specified index, or null if there is none.
262 LiveInterval::const_iterator
263 LiveInterval::FindLiveRangeContaining(unsigned Idx) const {
264 const_iterator It = std::upper_bound(begin(), end(), Idx);
265 if (It != ranges.begin()) {
267 if (It->contains(Idx))
274 LiveInterval::iterator
275 LiveInterval::FindLiveRangeContaining(unsigned Idx) {
276 iterator It = std::upper_bound(begin(), end(), Idx);
279 if (It->contains(Idx))
286 /// join - Join two live intervals (this, and other) together. This applies
287 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
288 /// the intervals are not joinable, this aborts.
289 void LiveInterval::join(LiveInterval &Other, const int *LHSValNoAssignments,
290 const int *RHSValNoAssignments,
291 SmallVector<VNInfo*, 16> &NewVNInfo) {
292 // Determine if any of our live range values are mapped. This is uncommon, so
293 // we want to avoid the interval scan if not.
294 bool MustMapCurValNos = false;
295 unsigned NumVals = getNumValNums();
296 unsigned NumNewVals = NewVNInfo.size();
297 for (unsigned i = 0; i != NumVals; ++i) {
298 unsigned LHSValID = LHSValNoAssignments[i];
300 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i)))
301 MustMapCurValNos = true;
304 // If we have to apply a mapping to our base interval assignment, rewrite it
306 if (MustMapCurValNos) {
307 // Map the first live range.
308 iterator OutIt = begin();
309 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
311 for (iterator I = OutIt, E = end(); I != E; ++I) {
312 OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]];
314 // If this live range has the same value # as its immediate predecessor,
315 // and if they are neighbors, remove one LiveRange. This happens when we
316 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
317 if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) {
318 (OutIt-1)->end = OutIt->end;
321 OutIt->start = I->start;
325 // Didn't merge, on to the next one.
330 // If we merge some live ranges, chop off the end.
331 ranges.erase(OutIt, end());
334 // Remember assignements because val# ids are changing.
335 SmallVector<unsigned, 16> OtherAssignments;
336 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
337 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]);
339 // Update val# info. Renumber them and make sure they all belong to this
340 // LiveInterval now. Also remove dead val#'s.
341 unsigned NumValNos = 0;
342 for (unsigned i = 0; i < NumNewVals; ++i) {
343 VNInfo *VNI = NewVNInfo[i];
346 valnos.push_back(VNI);
348 valnos[NumValNos] = VNI;
349 VNI->id = NumValNos++; // Renumber val#.
352 if (NumNewVals < NumVals)
353 valnos.resize(NumNewVals); // shrinkify
355 // Okay, now insert the RHS live ranges into the LHS.
356 iterator InsertPos = begin();
357 unsigned RangeNo = 0;
358 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) {
359 // Map the valno in the other live range to the current live range.
360 I->valno = NewVNInfo[OtherAssignments[RangeNo]];
361 assert(I->valno && "Adding a dead range?");
362 InsertPos = addRangeFrom(*I, InsertPos);
365 weight += Other.weight;
366 if (Other.preference && !preference)
367 preference = Other.preference;
370 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
371 /// interval as the specified value number. The LiveRanges in RHS are
372 /// allowed to overlap with LiveRanges in the current interval, but only if
373 /// the overlapping LiveRanges have the specified value number.
374 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
376 // TODO: Make this more efficient.
377 iterator InsertPos = begin();
378 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
379 // Map the valno in the other live range to the current live range.
381 Tmp.valno = LHSValNo;
382 InsertPos = addRangeFrom(Tmp, InsertPos);
387 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
388 /// in RHS into this live interval as the specified value number.
389 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
390 /// current interval, it will replace the value numbers of the overlaped
391 /// live ranges with the specified value number.
392 void LiveInterval::MergeValueInAsValue(const LiveInterval &RHS,
393 const VNInfo *RHSValNo, VNInfo *LHSValNo) {
394 SmallVector<VNInfo*, 4> ReplacedValNos;
395 iterator IP = begin();
396 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
397 if (I->valno != RHSValNo)
399 unsigned Start = I->start, End = I->end;
400 IP = std::upper_bound(IP, end(), Start);
401 // If the start of this range overlaps with an existing liverange, trim it.
402 if (IP != begin() && IP[-1].end > Start) {
403 if (IP->valno != LHSValNo) {
404 ReplacedValNos.push_back(IP->valno);
405 IP->valno = LHSValNo; // Update val#.
408 // Trimmed away the whole range?
409 if (Start >= End) continue;
411 // If the end of this range overlaps with an existing liverange, trim it.
412 if (IP != end() && End > IP->start) {
413 if (IP->valno != LHSValNo) {
414 ReplacedValNos.push_back(IP->valno);
415 IP->valno = LHSValNo; // Update val#.
418 // If this trimmed away the whole range, ignore it.
419 if (Start == End) continue;
422 // Map the valno in the other live range to the current live range.
423 IP = addRangeFrom(LiveRange(Start, End, LHSValNo), IP);
427 SmallSet<VNInfo*, 4> Seen;
428 for (unsigned i = 0, e = ReplacedValNos.size(); i != e; ++i) {
429 VNInfo *V1 = ReplacedValNos[i];
430 if (Seen.insert(V1)) {
432 for (const_iterator I = begin(), E = end(); I != E; ++I)
433 if (I->valno == V1) {
438 // Now that V1 is dead, remove it. If it is the largest value number,
439 // just nuke it (and any other deleted values neighboring it), otherwise
440 // mark it as ~1U so it can be nuked later.
441 if (V1->id == getNumValNums()-1) {
443 VNInfo *VNI = valnos.back();
446 } while (valnos.back()->def == ~1U);
456 /// MergeInClobberRanges - For any live ranges that are not defined in the
457 /// current interval, but are defined in the Clobbers interval, mark them
458 /// used with an unknown definition value.
459 void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers,
460 BumpPtrAllocator &VNInfoAllocator) {
461 if (Clobbers.begin() == Clobbers.end()) return;
463 // Find a value # to use for the clobber ranges. If there is already a value#
464 // for unknown values, use it.
465 // FIXME: Use a single sentinal number for these!
466 VNInfo *ClobberValNo = getNextValue(~0U, 0, VNInfoAllocator);
468 iterator IP = begin();
469 for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) {
470 unsigned Start = I->start, End = I->end;
471 IP = std::upper_bound(IP, end(), Start);
473 // If the start of this range overlaps with an existing liverange, trim it.
474 if (IP != begin() && IP[-1].end > Start) {
476 // Trimmed away the whole range?
477 if (Start >= End) continue;
479 // If the end of this range overlaps with an existing liverange, trim it.
480 if (IP != end() && End > IP->start) {
482 // If this trimmed away the whole range, ignore it.
483 if (Start == End) continue;
486 // Insert the clobber interval.
487 IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP);
491 /// MergeValueNumberInto - This method is called when two value nubmers
492 /// are found to be equivalent. This eliminates V1, replacing all
493 /// LiveRanges with the V1 value number with the V2 value number. This can
494 /// cause merging of V1/V2 values numbers and compaction of the value space.
495 void LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
496 assert(V1 != V2 && "Identical value#'s are always equivalent!");
498 // This code actually merges the (numerically) larger value number into the
499 // smaller value number, which is likely to allow us to compactify the value
500 // space. The only thing we have to be careful of is to preserve the
501 // instruction that defines the result value.
503 // Make sure V2 is smaller than V1.
504 if (V1->id < V2->id) {
505 copyValNumInfo(V1, V2);
509 // Merge V1 live ranges into V2.
510 for (iterator I = begin(); I != end(); ) {
512 if (LR->valno != V1) continue; // Not a V1 LiveRange.
514 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
517 iterator Prev = LR-1;
518 if (Prev->valno == V2 && Prev->end == LR->start) {
521 // Erase this live-range.
528 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
529 // Ensure that it is a V2 live-range.
532 // If we can merge it into later V2 live ranges, do so now. We ignore any
533 // following V1 live ranges, as they will be merged in subsequent iterations
536 if (I->start == LR->end && I->valno == V2) {
544 // Now that V1 is dead, remove it. If it is the largest value number, just
545 // nuke it (and any other deleted values neighboring it), otherwise mark it as
546 // ~1U so it can be nuked later.
547 if (V1->id == getNumValNums()-1) {
549 VNInfo *VNI = valnos.back();
552 } while (valnos.back()->def == ~1U);
558 void LiveInterval::Copy(const LiveInterval &RHS,
559 BumpPtrAllocator &VNInfoAllocator) {
562 preference = RHS.preference;
564 for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) {
565 const VNInfo *VNI = RHS.getValNumInfo(i);
566 VNInfo *NewVNI = getNextValue(~0U, 0, VNInfoAllocator);
567 copyValNumInfo(NewVNI, VNI);
569 for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) {
570 const LiveRange &LR = RHS.ranges[i];
571 addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id)));
575 unsigned LiveInterval::getSize() const {
577 for (const_iterator I = begin(), E = end(); I != E; ++I)
578 Sum += I->end - I->start;
582 std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
583 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")";
586 void LiveRange::dump() const {
587 cerr << *this << "\n";
590 void LiveInterval::print(std::ostream &OS, const MRegisterInfo *MRI) const {
591 if (MRI && MRegisterInfo::isPhysicalRegister(reg))
592 OS << MRI->getName(reg);
602 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
603 E = ranges.end(); I != E; ++I)
607 // Print value number info.
608 if (getNumValNums()) {
611 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
613 const VNInfo *vni = *i;
616 if (vni->def == ~1U) {
623 unsigned ee = vni->kills.size();
626 for (unsigned j = 0; j != ee; ++j) {
638 void LiveInterval::dump() const {
639 cerr << *this << "\n";
643 void LiveRange::print(std::ostream &os) const {