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/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);
209 else if (End < it->end)
210 // Overlapping intervals, there might have been a kill here.
211 removeKill(it->valno, End);
215 // Check to make sure that we are not overlapping two live ranges with
216 // different valno's.
217 assert(it->start >= End &&
218 "Cannot overlap two LiveRanges with differing ValID's");
221 // Otherwise, this is just a new range that doesn't interact with anything.
223 return ranges.insert(it, LR);
227 /// removeRange - Remove the specified range from this interval. Note that
228 /// the range must already be in this interval in its entirety.
229 void LiveInterval::removeRange(unsigned Start, unsigned End) {
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 if (I->start == Start) {
240 removeKills(I->valno, Start, End);
241 ranges.erase(I); // Removed the whole LiveRange.
247 // Otherwise if the span we are removing is at the end of the LiveRange,
248 // adjust the other way.
250 removeKills(I->valno, Start, End);
255 // Otherwise, we are splitting the LiveRange into two pieces.
256 unsigned OldEnd = I->end;
257 I->end = Start; // Trim the old interval.
259 // Insert the new one.
260 ranges.insert(next(I), LiveRange(End, OldEnd, I->valno));
263 /// getLiveRangeContaining - Return the live range that contains the
264 /// specified index, or null if there is none.
265 LiveInterval::const_iterator
266 LiveInterval::FindLiveRangeContaining(unsigned Idx) const {
267 const_iterator It = std::upper_bound(begin(), end(), Idx);
268 if (It != ranges.begin()) {
270 if (It->contains(Idx))
277 LiveInterval::iterator
278 LiveInterval::FindLiveRangeContaining(unsigned Idx) {
279 iterator It = std::upper_bound(begin(), end(), Idx);
282 if (It->contains(Idx))
289 /// join - Join two live intervals (this, and other) together. This applies
290 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
291 /// the intervals are not joinable, this aborts.
292 void LiveInterval::join(LiveInterval &Other, const int *LHSValNoAssignments,
293 const int *RHSValNoAssignments,
294 SmallVector<VNInfo*, 16> &NewVNInfo) {
295 // Determine if any of our live range values are mapped. This is uncommon, so
296 // we want to avoid the interval scan if not.
297 bool MustMapCurValNos = false;
298 unsigned NumVals = getNumValNums();
299 unsigned NumNewVals = NewVNInfo.size();
300 for (unsigned i = 0; i != NumVals; ++i) {
301 unsigned LHSValID = LHSValNoAssignments[i];
303 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i)))
304 MustMapCurValNos = true;
307 // If we have to apply a mapping to our base interval assignment, rewrite it
309 if (MustMapCurValNos) {
310 // Map the first live range.
311 iterator OutIt = begin();
312 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
314 for (iterator I = OutIt, E = end(); I != E; ++I) {
315 OutIt->valno = NewVNInfo[LHSValNoAssignments[I->valno->id]];
317 // If this live range has the same value # as its immediate predecessor,
318 // and if they are neighbors, remove one LiveRange. This happens when we
319 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
320 if (OutIt->valno == (OutIt-1)->valno && (OutIt-1)->end == OutIt->start) {
321 (OutIt-1)->end = OutIt->end;
324 OutIt->start = I->start;
328 // Didn't merge, on to the next one.
333 // If we merge some live ranges, chop off the end.
334 ranges.erase(OutIt, end());
337 // Remember assignements because val# ids are changing.
338 SmallVector<unsigned, 16> OtherAssignments;
339 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
340 OtherAssignments.push_back(RHSValNoAssignments[I->valno->id]);
342 // Update val# info. Renumber them and make sure they all belong to this
343 // LiveInterval now. Also remove dead val#'s.
344 unsigned NumValNos = 0;
345 for (unsigned i = 0; i < NumNewVals; ++i) {
346 VNInfo *VNI = NewVNInfo[i];
349 valnos.push_back(VNI);
351 valnos[NumValNos] = VNI;
352 VNI->id = NumValNos++; // Renumber val#.
355 if (NumNewVals < NumVals)
356 valnos.resize(NumNewVals); // shrinkify
358 // Okay, now insert the RHS live ranges into the LHS.
359 iterator InsertPos = begin();
360 unsigned RangeNo = 0;
361 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I, ++RangeNo) {
362 // Map the valno in the other live range to the current live range.
363 I->valno = NewVNInfo[OtherAssignments[RangeNo]];
364 assert(I->valno && "Adding a dead range?");
365 InsertPos = addRangeFrom(*I, InsertPos);
368 weight += Other.weight;
369 if (Other.preference && !preference)
370 preference = Other.preference;
373 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
374 /// interval as the specified value number. The LiveRanges in RHS are
375 /// allowed to overlap with LiveRanges in the current interval, but only if
376 /// the overlapping LiveRanges have the specified value number.
377 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
379 // TODO: Make this more efficient.
380 iterator InsertPos = begin();
381 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
382 // Map the valno in the other live range to the current live range.
384 Tmp.valno = LHSValNo;
385 InsertPos = addRangeFrom(Tmp, InsertPos);
390 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
391 /// in RHS into this live interval as the specified value number.
392 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
393 /// current interval, it will replace the value numbers of the overlaped
394 /// live ranges with the specified value number.
395 void LiveInterval::MergeValueInAsValue(const LiveInterval &RHS,
396 const VNInfo *RHSValNo, VNInfo *LHSValNo) {
397 SmallVector<VNInfo*, 4> ReplacedValNos;
398 iterator IP = begin();
399 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
400 if (I->valno != RHSValNo)
402 unsigned Start = I->start, End = I->end;
403 IP = std::upper_bound(IP, end(), Start);
404 // If the start of this range overlaps with an existing liverange, trim it.
405 if (IP != begin() && IP[-1].end > Start) {
406 if (IP->valno != LHSValNo) {
407 ReplacedValNos.push_back(IP->valno);
408 IP->valno = LHSValNo; // Update val#.
411 // Trimmed away the whole range?
412 if (Start >= End) continue;
414 // If the end of this range overlaps with an existing liverange, trim it.
415 if (IP != end() && End > IP->start) {
416 if (IP->valno != LHSValNo) {
417 ReplacedValNos.push_back(IP->valno);
418 IP->valno = LHSValNo; // Update val#.
421 // If this trimmed away the whole range, ignore it.
422 if (Start == End) continue;
425 // Map the valno in the other live range to the current live range.
426 IP = addRangeFrom(LiveRange(Start, End, LHSValNo), IP);
430 SmallSet<VNInfo*, 4> Seen;
431 for (unsigned i = 0, e = ReplacedValNos.size(); i != e; ++i) {
432 VNInfo *V1 = ReplacedValNos[i];
433 if (Seen.insert(V1)) {
435 for (const_iterator I = begin(), E = end(); I != E; ++I)
436 if (I->valno == V1) {
441 // Now that V1 is dead, remove it. If it is the largest value number,
442 // just nuke it (and any other deleted values neighboring it), otherwise
443 // mark it as ~1U so it can be nuked later.
444 if (V1->id == getNumValNums()-1) {
446 VNInfo *VNI = valnos.back();
449 } while (valnos.back()->def == ~1U);
459 /// MergeInClobberRanges - For any live ranges that are not defined in the
460 /// current interval, but are defined in the Clobbers interval, mark them
461 /// used with an unknown definition value.
462 void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers,
463 BumpPtrAllocator &VNInfoAllocator) {
464 if (Clobbers.begin() == Clobbers.end()) return;
466 // Find a value # to use for the clobber ranges. If there is already a value#
467 // for unknown values, use it.
468 // FIXME: Use a single sentinal number for these!
469 VNInfo *ClobberValNo = getNextValue(~0U, 0, VNInfoAllocator);
471 iterator IP = begin();
472 for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) {
473 unsigned Start = I->start, End = I->end;
474 IP = std::upper_bound(IP, end(), Start);
476 // If the start of this range overlaps with an existing liverange, trim it.
477 if (IP != begin() && IP[-1].end > Start) {
479 // Trimmed away the whole range?
480 if (Start >= End) continue;
482 // If the end of this range overlaps with an existing liverange, trim it.
483 if (IP != end() && End > IP->start) {
485 // If this trimmed away the whole range, ignore it.
486 if (Start == End) continue;
489 // Insert the clobber interval.
490 IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP);
494 /// MergeValueNumberInto - This method is called when two value nubmers
495 /// are found to be equivalent. This eliminates V1, replacing all
496 /// LiveRanges with the V1 value number with the V2 value number. This can
497 /// cause merging of V1/V2 values numbers and compaction of the value space.
498 void LiveInterval::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
499 assert(V1 != V2 && "Identical value#'s are always equivalent!");
501 // This code actually merges the (numerically) larger value number into the
502 // smaller value number, which is likely to allow us to compactify the value
503 // space. The only thing we have to be careful of is to preserve the
504 // instruction that defines the result value.
506 // Make sure V2 is smaller than V1.
507 if (V1->id < V2->id) {
508 copyValNumInfo(V1, V2);
512 // Merge V1 live ranges into V2.
513 for (iterator I = begin(); I != end(); ) {
515 if (LR->valno != V1) continue; // Not a V1 LiveRange.
517 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
520 iterator Prev = LR-1;
521 if (Prev->valno == V2 && Prev->end == LR->start) {
524 // Erase this live-range.
531 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
532 // Ensure that it is a V2 live-range.
535 // If we can merge it into later V2 live ranges, do so now. We ignore any
536 // following V1 live ranges, as they will be merged in subsequent iterations
539 if (I->start == LR->end && I->valno == V2) {
547 // Now that V1 is dead, remove it. If it is the largest value number, just
548 // nuke it (and any other deleted values neighboring it), otherwise mark it as
549 // ~1U so it can be nuked later.
550 if (V1->id == getNumValNums()-1) {
552 VNInfo *VNI = valnos.back();
555 } while (valnos.back()->def == ~1U);
561 void LiveInterval::Copy(const LiveInterval &RHS,
562 BumpPtrAllocator &VNInfoAllocator) {
565 preference = RHS.preference;
567 for (unsigned i = 0, e = RHS.getNumValNums(); i != e; ++i) {
568 const VNInfo *VNI = RHS.getValNumInfo(i);
569 VNInfo *NewVNI = getNextValue(~0U, 0, VNInfoAllocator);
570 copyValNumInfo(NewVNI, VNI);
572 for (unsigned i = 0, e = RHS.ranges.size(); i != e; ++i) {
573 const LiveRange &LR = RHS.ranges[i];
574 addRange(LiveRange(LR.start, LR.end, getValNumInfo(LR.valno->id)));
578 unsigned LiveInterval::getSize() const {
580 for (const_iterator I = begin(), E = end(); I != E; ++I)
581 Sum += I->end - I->start;
585 std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
586 return os << '[' << LR.start << ',' << LR.end << ':' << LR.valno->id << ")";
589 void LiveRange::dump() const {
590 cerr << *this << "\n";
593 void LiveInterval::print(std::ostream &OS, const MRegisterInfo *MRI) const {
594 if (MRI && MRegisterInfo::isPhysicalRegister(reg))
595 OS << MRI->getName(reg);
605 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
606 E = ranges.end(); I != E; ++I)
610 // Print value number info.
611 if (getNumValNums()) {
614 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
616 const VNInfo *vni = *i;
619 if (vni->def == ~1U) {
626 unsigned ee = vni->kills.size();
629 for (unsigned j = 0; j != ee; ++j) {
643 void LiveInterval::dump() const {
644 cerr << *this << "\n";
648 void LiveRange::print(std::ostream &os) const {