1 //===-- LiveInterval.cpp - Live Interval Representation -------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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 range 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 ranges can have holes,
15 // i.e. a range might look like [1,20), [50,65), [1000,1001). Each
16 // individual segment is represented as an instance of LiveRange::Segment,
17 // and the whole range is represented as an instance of LiveRange.
18 //
19 //===----------------------------------------------------------------------===//
20
21 #include "llvm/CodeGen/LiveInterval.h"
22 #include "RegisterCoalescer.h"
23 #include "llvm/ADT/DenseMap.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/ADT/SmallSet.h"
26 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
27 #include "llvm/CodeGen/MachineRegisterInfo.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/Format.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include "llvm/Target/TargetRegisterInfo.h"
32 #include <algorithm>
33 using namespace llvm;
34
35 namespace {
36 //===----------------------------------------------------------------------===//
37 // Implementation of various methods necessary for calculation of live ranges.
38 // The implementation of the methods abstracts from the concrete type of the
39 // segment collection.
40 //
41 // Implementation of the class follows the Template design pattern. The base
42 // class contains generic algorithms that call collection-specific methods,
43 // which are provided in concrete subclasses. In order to avoid virtual calls
44 // these methods are provided by means of C++ template instantiation.
45 // The base class calls the methods of the subclass through method impl(),
46 // which casts 'this' pointer to the type of the subclass.
47 //
48 //===----------------------------------------------------------------------===//
49
50 template <typename ImplT, typename IteratorT, typename CollectionT>
51 class CalcLiveRangeUtilBase {
52 protected:
53 LiveRange *LR;
54
55 protected:
CalcLiveRangeUtilBase(LiveRange * LR)56 CalcLiveRangeUtilBase(LiveRange *LR) : LR(LR) {}
57
58 public:
59 typedef LiveRange::Segment Segment;
60 typedef IteratorT iterator;
61
createDeadDef(SlotIndex Def,VNInfo::Allocator & VNInfoAllocator)62 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator) {
63 assert(!Def.isDead() && "Cannot define a value at the dead slot");
64
65 iterator I = impl().find(Def);
66 if (I == segments().end()) {
67 VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
68 impl().insertAtEnd(Segment(Def, Def.getDeadSlot(), VNI));
69 return VNI;
70 }
71
72 Segment *S = segmentAt(I);
73 if (SlotIndex::isSameInstr(Def, S->start)) {
74 assert(S->valno->def == S->start && "Inconsistent existing value def");
75
76 // It is possible to have both normal and early-clobber defs of the same
77 // register on an instruction. It doesn't make a lot of sense, but it is
78 // possible to specify in inline assembly.
79 //
80 // Just convert everything to early-clobber.
81 Def = std::min(Def, S->start);
82 if (Def != S->start)
83 S->start = S->valno->def = Def;
84 return S->valno;
85 }
86 assert(SlotIndex::isEarlierInstr(Def, S->start) && "Already live at def");
87 VNInfo *VNI = LR->getNextValue(Def, VNInfoAllocator);
88 segments().insert(I, Segment(Def, Def.getDeadSlot(), VNI));
89 return VNI;
90 }
91
extendInBlock(SlotIndex StartIdx,SlotIndex Use)92 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Use) {
93 if (segments().empty())
94 return nullptr;
95 iterator I =
96 impl().findInsertPos(Segment(Use.getPrevSlot(), Use, nullptr));
97 if (I == segments().begin())
98 return nullptr;
99 --I;
100 if (I->end <= StartIdx)
101 return nullptr;
102 if (I->end < Use)
103 extendSegmentEndTo(I, Use);
104 return I->valno;
105 }
106
107 /// This method is used when we want to extend the segment specified
108 /// by I to end at the specified endpoint. To do this, we should
109 /// merge and eliminate all segments that this will overlap
110 /// with. The iterator is not invalidated.
extendSegmentEndTo(iterator I,SlotIndex NewEnd)111 void extendSegmentEndTo(iterator I, SlotIndex NewEnd) {
112 assert(I != segments().end() && "Not a valid segment!");
113 Segment *S = segmentAt(I);
114 VNInfo *ValNo = I->valno;
115
116 // Search for the first segment that we can't merge with.
117 iterator MergeTo = std::next(I);
118 for (; MergeTo != segments().end() && NewEnd >= MergeTo->end; ++MergeTo)
119 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
120
121 // If NewEnd was in the middle of a segment, make sure to get its endpoint.
122 S->end = std::max(NewEnd, std::prev(MergeTo)->end);
123
124 // If the newly formed segment now touches the segment after it and if they
125 // have the same value number, merge the two segments into one segment.
126 if (MergeTo != segments().end() && MergeTo->start <= I->end &&
127 MergeTo->valno == ValNo) {
128 S->end = MergeTo->end;
129 ++MergeTo;
130 }
131
132 // Erase any dead segments.
133 segments().erase(std::next(I), MergeTo);
134 }
135
136 /// This method is used when we want to extend the segment specified
137 /// by I to start at the specified endpoint. To do this, we should
138 /// merge and eliminate all segments that this will overlap with.
extendSegmentStartTo(iterator I,SlotIndex NewStart)139 iterator extendSegmentStartTo(iterator I, SlotIndex NewStart) {
140 assert(I != segments().end() && "Not a valid segment!");
141 Segment *S = segmentAt(I);
142 VNInfo *ValNo = I->valno;
143
144 // Search for the first segment that we can't merge with.
145 iterator MergeTo = I;
146 do {
147 if (MergeTo == segments().begin()) {
148 S->start = NewStart;
149 segments().erase(MergeTo, I);
150 return I;
151 }
152 assert(MergeTo->valno == ValNo && "Cannot merge with differing values!");
153 --MergeTo;
154 } while (NewStart <= MergeTo->start);
155
156 // If we start in the middle of another segment, just delete a range and
157 // extend that segment.
158 if (MergeTo->end >= NewStart && MergeTo->valno == ValNo) {
159 segmentAt(MergeTo)->end = S->end;
160 } else {
161 // Otherwise, extend the segment right after.
162 ++MergeTo;
163 Segment *MergeToSeg = segmentAt(MergeTo);
164 MergeToSeg->start = NewStart;
165 MergeToSeg->end = S->end;
166 }
167
168 segments().erase(std::next(MergeTo), std::next(I));
169 return MergeTo;
170 }
171
addSegment(Segment S)172 iterator addSegment(Segment S) {
173 SlotIndex Start = S.start, End = S.end;
174 iterator I = impl().findInsertPos(S);
175
176 // If the inserted segment starts in the middle or right at the end of
177 // another segment, just extend that segment to contain the segment of S.
178 if (I != segments().begin()) {
179 iterator B = std::prev(I);
180 if (S.valno == B->valno) {
181 if (B->start <= Start && B->end >= Start) {
182 extendSegmentEndTo(B, End);
183 return B;
184 }
185 } else {
186 // Check to make sure that we are not overlapping two live segments with
187 // different valno's.
188 assert(B->end <= Start &&
189 "Cannot overlap two segments with differing ValID's"
190 " (did you def the same reg twice in a MachineInstr?)");
191 }
192 }
193
194 // Otherwise, if this segment ends in the middle of, or right next
195 // to, another segment, merge it into that segment.
196 if (I != segments().end()) {
197 if (S.valno == I->valno) {
198 if (I->start <= End) {
199 I = extendSegmentStartTo(I, Start);
200
201 // If S is a complete superset of a segment, we may need to grow its
202 // endpoint as well.
203 if (End > I->end)
204 extendSegmentEndTo(I, End);
205 return I;
206 }
207 } else {
208 // Check to make sure that we are not overlapping two live segments with
209 // different valno's.
210 assert(I->start >= End &&
211 "Cannot overlap two segments with differing ValID's");
212 }
213 }
214
215 // Otherwise, this is just a new segment that doesn't interact with
216 // anything.
217 // Insert it.
218 return segments().insert(I, S);
219 }
220
221 private:
impl()222 ImplT &impl() { return *static_cast<ImplT *>(this); }
223
segments()224 CollectionT &segments() { return impl().segmentsColl(); }
225
segmentAt(iterator I)226 Segment *segmentAt(iterator I) { return const_cast<Segment *>(&(*I)); }
227 };
228
229 //===----------------------------------------------------------------------===//
230 // Instantiation of the methods for calculation of live ranges
231 // based on a segment vector.
232 //===----------------------------------------------------------------------===//
233
234 class CalcLiveRangeUtilVector;
235 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilVector, LiveRange::iterator,
236 LiveRange::Segments> CalcLiveRangeUtilVectorBase;
237
238 class CalcLiveRangeUtilVector : public CalcLiveRangeUtilVectorBase {
239 public:
CalcLiveRangeUtilVector(LiveRange * LR)240 CalcLiveRangeUtilVector(LiveRange *LR) : CalcLiveRangeUtilVectorBase(LR) {}
241
242 private:
243 friend CalcLiveRangeUtilVectorBase;
244
segmentsColl()245 LiveRange::Segments &segmentsColl() { return LR->segments; }
246
insertAtEnd(const Segment & S)247 void insertAtEnd(const Segment &S) { LR->segments.push_back(S); }
248
find(SlotIndex Pos)249 iterator find(SlotIndex Pos) { return LR->find(Pos); }
250
findInsertPos(Segment S)251 iterator findInsertPos(Segment S) {
252 return std::upper_bound(LR->begin(), LR->end(), S.start);
253 }
254 };
255
256 //===----------------------------------------------------------------------===//
257 // Instantiation of the methods for calculation of live ranges
258 // based on a segment set.
259 //===----------------------------------------------------------------------===//
260
261 class CalcLiveRangeUtilSet;
262 typedef CalcLiveRangeUtilBase<CalcLiveRangeUtilSet,
263 LiveRange::SegmentSet::iterator,
264 LiveRange::SegmentSet> CalcLiveRangeUtilSetBase;
265
266 class CalcLiveRangeUtilSet : public CalcLiveRangeUtilSetBase {
267 public:
CalcLiveRangeUtilSet(LiveRange * LR)268 CalcLiveRangeUtilSet(LiveRange *LR) : CalcLiveRangeUtilSetBase(LR) {}
269
270 private:
271 friend CalcLiveRangeUtilSetBase;
272
segmentsColl()273 LiveRange::SegmentSet &segmentsColl() { return *LR->segmentSet; }
274
insertAtEnd(const Segment & S)275 void insertAtEnd(const Segment &S) {
276 LR->segmentSet->insert(LR->segmentSet->end(), S);
277 }
278
find(SlotIndex Pos)279 iterator find(SlotIndex Pos) {
280 iterator I =
281 LR->segmentSet->upper_bound(Segment(Pos, Pos.getNextSlot(), nullptr));
282 if (I == LR->segmentSet->begin())
283 return I;
284 iterator PrevI = std::prev(I);
285 if (Pos < (*PrevI).end)
286 return PrevI;
287 return I;
288 }
289
findInsertPos(Segment S)290 iterator findInsertPos(Segment S) {
291 iterator I = LR->segmentSet->upper_bound(S);
292 if (I != LR->segmentSet->end() && !(S.start < *I))
293 ++I;
294 return I;
295 }
296 };
297 } // namespace
298
299 //===----------------------------------------------------------------------===//
300 // LiveRange methods
301 //===----------------------------------------------------------------------===//
302
find(SlotIndex Pos)303 LiveRange::iterator LiveRange::find(SlotIndex Pos) {
304 // This algorithm is basically std::upper_bound.
305 // Unfortunately, std::upper_bound cannot be used with mixed types until we
306 // adopt C++0x. Many libraries can do it, but not all.
307 if (empty() || Pos >= endIndex())
308 return end();
309 iterator I = begin();
310 size_t Len = size();
311 do {
312 size_t Mid = Len >> 1;
313 if (Pos < I[Mid].end)
314 Len = Mid;
315 else
316 I += Mid + 1, Len -= Mid + 1;
317 } while (Len);
318 return I;
319 }
320
createDeadDef(SlotIndex Def,VNInfo::Allocator & VNInfoAllocator)321 VNInfo *LiveRange::createDeadDef(SlotIndex Def,
322 VNInfo::Allocator &VNInfoAllocator) {
323 // Use the segment set, if it is available.
324 if (segmentSet != nullptr)
325 return CalcLiveRangeUtilSet(this).createDeadDef(Def, VNInfoAllocator);
326 // Otherwise use the segment vector.
327 return CalcLiveRangeUtilVector(this).createDeadDef(Def, VNInfoAllocator);
328 }
329
330 // overlaps - Return true if the intersection of the two live ranges is
331 // not empty.
332 //
333 // An example for overlaps():
334 //
335 // 0: A = ...
336 // 4: B = ...
337 // 8: C = A + B ;; last use of A
338 //
339 // The live ranges should look like:
340 //
341 // A = [3, 11)
342 // B = [7, x)
343 // C = [11, y)
344 //
345 // A->overlaps(C) should return false since we want to be able to join
346 // A and C.
347 //
overlapsFrom(const LiveRange & other,const_iterator StartPos) const348 bool LiveRange::overlapsFrom(const LiveRange& other,
349 const_iterator StartPos) const {
350 assert(!empty() && "empty range");
351 const_iterator i = begin();
352 const_iterator ie = end();
353 const_iterator j = StartPos;
354 const_iterator je = other.end();
355
356 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
357 StartPos != other.end() && "Bogus start position hint!");
358
359 if (i->start < j->start) {
360 i = std::upper_bound(i, ie, j->start);
361 if (i != begin()) --i;
362 } else if (j->start < i->start) {
363 ++StartPos;
364 if (StartPos != other.end() && StartPos->start <= i->start) {
365 assert(StartPos < other.end() && i < end());
366 j = std::upper_bound(j, je, i->start);
367 if (j != other.begin()) --j;
368 }
369 } else {
370 return true;
371 }
372
373 if (j == je) return false;
374
375 while (i != ie) {
376 if (i->start > j->start) {
377 std::swap(i, j);
378 std::swap(ie, je);
379 }
380
381 if (i->end > j->start)
382 return true;
383 ++i;
384 }
385
386 return false;
387 }
388
overlaps(const LiveRange & Other,const CoalescerPair & CP,const SlotIndexes & Indexes) const389 bool LiveRange::overlaps(const LiveRange &Other, const CoalescerPair &CP,
390 const SlotIndexes &Indexes) const {
391 assert(!empty() && "empty range");
392 if (Other.empty())
393 return false;
394
395 // Use binary searches to find initial positions.
396 const_iterator I = find(Other.beginIndex());
397 const_iterator IE = end();
398 if (I == IE)
399 return false;
400 const_iterator J = Other.find(I->start);
401 const_iterator JE = Other.end();
402 if (J == JE)
403 return false;
404
405 for (;;) {
406 // J has just been advanced to satisfy:
407 assert(J->end >= I->start);
408 // Check for an overlap.
409 if (J->start < I->end) {
410 // I and J are overlapping. Find the later start.
411 SlotIndex Def = std::max(I->start, J->start);
412 // Allow the overlap if Def is a coalescable copy.
413 if (Def.isBlock() ||
414 !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
415 return true;
416 }
417 // Advance the iterator that ends first to check for more overlaps.
418 if (J->end > I->end) {
419 std::swap(I, J);
420 std::swap(IE, JE);
421 }
422 // Advance J until J->end >= I->start.
423 do
424 if (++J == JE)
425 return false;
426 while (J->end < I->start);
427 }
428 }
429
430 /// overlaps - Return true if the live range overlaps an interval specified
431 /// by [Start, End).
overlaps(SlotIndex Start,SlotIndex End) const432 bool LiveRange::overlaps(SlotIndex Start, SlotIndex End) const {
433 assert(Start < End && "Invalid range");
434 const_iterator I = std::lower_bound(begin(), end(), End);
435 return I != begin() && (--I)->end > Start;
436 }
437
covers(const LiveRange & Other) const438 bool LiveRange::covers(const LiveRange &Other) const {
439 if (empty())
440 return Other.empty();
441
442 const_iterator I = begin();
443 for (const Segment &O : Other.segments) {
444 I = advanceTo(I, O.start);
445 if (I == end() || I->start > O.start)
446 return false;
447
448 // Check adjacent live segments and see if we can get behind O.end.
449 while (I->end < O.end) {
450 const_iterator Last = I;
451 // Get next segment and abort if it was not adjacent.
452 ++I;
453 if (I == end() || Last->end != I->start)
454 return false;
455 }
456 }
457 return true;
458 }
459
460 /// ValNo is dead, remove it. If it is the largest value number, just nuke it
461 /// (and any other deleted values neighboring it), otherwise mark it as ~1U so
462 /// it can be nuked later.
markValNoForDeletion(VNInfo * ValNo)463 void LiveRange::markValNoForDeletion(VNInfo *ValNo) {
464 if (ValNo->id == getNumValNums()-1) {
465 do {
466 valnos.pop_back();
467 } while (!valnos.empty() && valnos.back()->isUnused());
468 } else {
469 ValNo->markUnused();
470 }
471 }
472
473 /// RenumberValues - Renumber all values in order of appearance and delete the
474 /// remaining unused values.
RenumberValues()475 void LiveRange::RenumberValues() {
476 SmallPtrSet<VNInfo*, 8> Seen;
477 valnos.clear();
478 for (const Segment &S : segments) {
479 VNInfo *VNI = S.valno;
480 if (!Seen.insert(VNI).second)
481 continue;
482 assert(!VNI->isUnused() && "Unused valno used by live segment");
483 VNI->id = (unsigned)valnos.size();
484 valnos.push_back(VNI);
485 }
486 }
487
addSegmentToSet(Segment S)488 void LiveRange::addSegmentToSet(Segment S) {
489 CalcLiveRangeUtilSet(this).addSegment(S);
490 }
491
addSegment(Segment S)492 LiveRange::iterator LiveRange::addSegment(Segment S) {
493 // Use the segment set, if it is available.
494 if (segmentSet != nullptr) {
495 addSegmentToSet(S);
496 return end();
497 }
498 // Otherwise use the segment vector.
499 return CalcLiveRangeUtilVector(this).addSegment(S);
500 }
501
append(const Segment S)502 void LiveRange::append(const Segment S) {
503 // Check that the segment belongs to the back of the list.
504 assert(segments.empty() || segments.back().end <= S.start);
505 segments.push_back(S);
506 }
507
508 /// extendInBlock - If this range is live before Kill in the basic
509 /// block that starts at StartIdx, extend it to be live up to Kill and return
510 /// the value. If there is no live range before Kill, return NULL.
extendInBlock(SlotIndex StartIdx,SlotIndex Kill)511 VNInfo *LiveRange::extendInBlock(SlotIndex StartIdx, SlotIndex Kill) {
512 // Use the segment set, if it is available.
513 if (segmentSet != nullptr)
514 return CalcLiveRangeUtilSet(this).extendInBlock(StartIdx, Kill);
515 // Otherwise use the segment vector.
516 return CalcLiveRangeUtilVector(this).extendInBlock(StartIdx, Kill);
517 }
518
519 /// Remove the specified segment from this range. Note that the segment must
520 /// be in a single Segment in its entirety.
removeSegment(SlotIndex Start,SlotIndex End,bool RemoveDeadValNo)521 void LiveRange::removeSegment(SlotIndex Start, SlotIndex End,
522 bool RemoveDeadValNo) {
523 // Find the Segment containing this span.
524 iterator I = find(Start);
525 assert(I != end() && "Segment is not in range!");
526 assert(I->containsInterval(Start, End)
527 && "Segment is not entirely in range!");
528
529 // If the span we are removing is at the start of the Segment, adjust it.
530 VNInfo *ValNo = I->valno;
531 if (I->start == Start) {
532 if (I->end == End) {
533 if (RemoveDeadValNo) {
534 // Check if val# is dead.
535 bool isDead = true;
536 for (const_iterator II = begin(), EE = end(); II != EE; ++II)
537 if (II != I && II->valno == ValNo) {
538 isDead = false;
539 break;
540 }
541 if (isDead) {
542 // Now that ValNo is dead, remove it.
543 markValNoForDeletion(ValNo);
544 }
545 }
546
547 segments.erase(I); // Removed the whole Segment.
548 } else
549 I->start = End;
550 return;
551 }
552
553 // Otherwise if the span we are removing is at the end of the Segment,
554 // adjust the other way.
555 if (I->end == End) {
556 I->end = Start;
557 return;
558 }
559
560 // Otherwise, we are splitting the Segment into two pieces.
561 SlotIndex OldEnd = I->end;
562 I->end = Start; // Trim the old segment.
563
564 // Insert the new one.
565 segments.insert(std::next(I), Segment(End, OldEnd, ValNo));
566 }
567
568 /// removeValNo - Remove all the segments defined by the specified value#.
569 /// Also remove the value# from value# list.
removeValNo(VNInfo * ValNo)570 void LiveRange::removeValNo(VNInfo *ValNo) {
571 if (empty()) return;
572 segments.erase(std::remove_if(begin(), end(), [ValNo](const Segment &S) {
573 return S.valno == ValNo;
574 }), end());
575 // Now that ValNo is dead, remove it.
576 markValNoForDeletion(ValNo);
577 }
578
join(LiveRange & Other,const int * LHSValNoAssignments,const int * RHSValNoAssignments,SmallVectorImpl<VNInfo * > & NewVNInfo)579 void LiveRange::join(LiveRange &Other,
580 const int *LHSValNoAssignments,
581 const int *RHSValNoAssignments,
582 SmallVectorImpl<VNInfo *> &NewVNInfo) {
583 verify();
584
585 // Determine if any of our values are mapped. This is uncommon, so we want
586 // to avoid the range scan if not.
587 bool MustMapCurValNos = false;
588 unsigned NumVals = getNumValNums();
589 unsigned NumNewVals = NewVNInfo.size();
590 for (unsigned i = 0; i != NumVals; ++i) {
591 unsigned LHSValID = LHSValNoAssignments[i];
592 if (i != LHSValID ||
593 (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
594 MustMapCurValNos = true;
595 break;
596 }
597 }
598
599 // If we have to apply a mapping to our base range assignment, rewrite it now.
600 if (MustMapCurValNos && !empty()) {
601 // Map the first live range.
602
603 iterator OutIt = begin();
604 OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
605 for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
606 VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
607 assert(nextValNo && "Huh?");
608
609 // If this live range has the same value # as its immediate predecessor,
610 // and if they are neighbors, remove one Segment. This happens when we
611 // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
612 if (OutIt->valno == nextValNo && OutIt->end == I->start) {
613 OutIt->end = I->end;
614 } else {
615 // Didn't merge. Move OutIt to the next segment,
616 ++OutIt;
617 OutIt->valno = nextValNo;
618 if (OutIt != I) {
619 OutIt->start = I->start;
620 OutIt->end = I->end;
621 }
622 }
623 }
624 // If we merge some segments, chop off the end.
625 ++OutIt;
626 segments.erase(OutIt, end());
627 }
628
629 // Rewrite Other values before changing the VNInfo ids.
630 // This can leave Other in an invalid state because we're not coalescing
631 // touching segments that now have identical values. That's OK since Other is
632 // not supposed to be valid after calling join();
633 for (Segment &S : Other.segments)
634 S.valno = NewVNInfo[RHSValNoAssignments[S.valno->id]];
635
636 // Update val# info. Renumber them and make sure they all belong to this
637 // LiveRange now. Also remove dead val#'s.
638 unsigned NumValNos = 0;
639 for (unsigned i = 0; i < NumNewVals; ++i) {
640 VNInfo *VNI = NewVNInfo[i];
641 if (VNI) {
642 if (NumValNos >= NumVals)
643 valnos.push_back(VNI);
644 else
645 valnos[NumValNos] = VNI;
646 VNI->id = NumValNos++; // Renumber val#.
647 }
648 }
649 if (NumNewVals < NumVals)
650 valnos.resize(NumNewVals); // shrinkify
651
652 // Okay, now insert the RHS live segments into the LHS.
653 LiveRangeUpdater Updater(this);
654 for (Segment &S : Other.segments)
655 Updater.add(S);
656 }
657
658 /// Merge all of the segments in RHS into this live range as the specified
659 /// value number. The segments in RHS are allowed to overlap with segments in
660 /// the current range, but only if the overlapping segments have the
661 /// specified value number.
MergeSegmentsInAsValue(const LiveRange & RHS,VNInfo * LHSValNo)662 void LiveRange::MergeSegmentsInAsValue(const LiveRange &RHS,
663 VNInfo *LHSValNo) {
664 LiveRangeUpdater Updater(this);
665 for (const Segment &S : RHS.segments)
666 Updater.add(S.start, S.end, LHSValNo);
667 }
668
669 /// MergeValueInAsValue - Merge all of the live segments of a specific val#
670 /// in RHS into this live range as the specified value number.
671 /// The segments in RHS are allowed to overlap with segments in the
672 /// current range, it will replace the value numbers of the overlaped
673 /// segments with the specified value number.
MergeValueInAsValue(const LiveRange & RHS,const VNInfo * RHSValNo,VNInfo * LHSValNo)674 void LiveRange::MergeValueInAsValue(const LiveRange &RHS,
675 const VNInfo *RHSValNo,
676 VNInfo *LHSValNo) {
677 LiveRangeUpdater Updater(this);
678 for (const Segment &S : RHS.segments)
679 if (S.valno == RHSValNo)
680 Updater.add(S.start, S.end, LHSValNo);
681 }
682
683 /// MergeValueNumberInto - This method is called when two value nubmers
684 /// are found to be equivalent. This eliminates V1, replacing all
685 /// segments with the V1 value number with the V2 value number. This can
686 /// cause merging of V1/V2 values numbers and compaction of the value space.
MergeValueNumberInto(VNInfo * V1,VNInfo * V2)687 VNInfo *LiveRange::MergeValueNumberInto(VNInfo *V1, VNInfo *V2) {
688 assert(V1 != V2 && "Identical value#'s are always equivalent!");
689
690 // This code actually merges the (numerically) larger value number into the
691 // smaller value number, which is likely to allow us to compactify the value
692 // space. The only thing we have to be careful of is to preserve the
693 // instruction that defines the result value.
694
695 // Make sure V2 is smaller than V1.
696 if (V1->id < V2->id) {
697 V1->copyFrom(*V2);
698 std::swap(V1, V2);
699 }
700
701 // Merge V1 segments into V2.
702 for (iterator I = begin(); I != end(); ) {
703 iterator S = I++;
704 if (S->valno != V1) continue; // Not a V1 Segment.
705
706 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
707 // range, extend it.
708 if (S != begin()) {
709 iterator Prev = S-1;
710 if (Prev->valno == V2 && Prev->end == S->start) {
711 Prev->end = S->end;
712
713 // Erase this live-range.
714 segments.erase(S);
715 I = Prev+1;
716 S = Prev;
717 }
718 }
719
720 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
721 // Ensure that it is a V2 live-range.
722 S->valno = V2;
723
724 // If we can merge it into later V2 segments, do so now. We ignore any
725 // following V1 segments, as they will be merged in subsequent iterations
726 // of the loop.
727 if (I != end()) {
728 if (I->start == S->end && I->valno == V2) {
729 S->end = I->end;
730 segments.erase(I);
731 I = S+1;
732 }
733 }
734 }
735
736 // Now that V1 is dead, remove it.
737 markValNoForDeletion(V1);
738
739 return V2;
740 }
741
flushSegmentSet()742 void LiveRange::flushSegmentSet() {
743 assert(segmentSet != nullptr && "segment set must have been created");
744 assert(
745 segments.empty() &&
746 "segment set can be used only initially before switching to the array");
747 segments.append(segmentSet->begin(), segmentSet->end());
748 segmentSet = nullptr;
749 verify();
750 }
751
freeSubRange(SubRange * S)752 void LiveInterval::freeSubRange(SubRange *S) {
753 S->~SubRange();
754 // Memory was allocated with BumpPtr allocator and is not freed here.
755 }
756
removeEmptySubRanges()757 void LiveInterval::removeEmptySubRanges() {
758 SubRange **NextPtr = &SubRanges;
759 SubRange *I = *NextPtr;
760 while (I != nullptr) {
761 if (!I->empty()) {
762 NextPtr = &I->Next;
763 I = *NextPtr;
764 continue;
765 }
766 // Skip empty subranges until we find the first nonempty one.
767 do {
768 SubRange *Next = I->Next;
769 freeSubRange(I);
770 I = Next;
771 } while (I != nullptr && I->empty());
772 *NextPtr = I;
773 }
774 }
775
clearSubRanges()776 void LiveInterval::clearSubRanges() {
777 for (SubRange *I = SubRanges, *Next; I != nullptr; I = Next) {
778 Next = I->Next;
779 freeSubRange(I);
780 }
781 SubRanges = nullptr;
782 }
783
784 /// Helper function for constructMainRangeFromSubranges(): Search the CFG
785 /// backwards until we find a place covered by a LiveRange segment that actually
786 /// has a valno set.
searchForVNI(const SlotIndexes & Indexes,LiveRange & LR,const MachineBasicBlock * MBB,SmallPtrSetImpl<const MachineBasicBlock * > & Visited)787 static VNInfo *searchForVNI(const SlotIndexes &Indexes, LiveRange &LR,
788 const MachineBasicBlock *MBB,
789 SmallPtrSetImpl<const MachineBasicBlock*> &Visited) {
790 // We start the search at the end of MBB.
791 SlotIndex EndIdx = Indexes.getMBBEndIdx(MBB);
792 // In our use case we can't live the area covered by the live segments without
793 // finding an actual VNI def.
794 LiveRange::iterator I = LR.find(EndIdx.getPrevSlot());
795 assert(I != LR.end());
796 LiveRange::Segment &S = *I;
797 if (S.valno != nullptr)
798 return S.valno;
799
800 VNInfo *VNI = nullptr;
801 // Continue at predecessors (we could even go to idom with domtree available).
802 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
803 // Avoid going in circles.
804 if (!Visited.insert(Pred).second)
805 continue;
806
807 VNI = searchForVNI(Indexes, LR, Pred, Visited);
808 if (VNI != nullptr) {
809 S.valno = VNI;
810 break;
811 }
812 }
813
814 return VNI;
815 }
816
determineMissingVNIs(const SlotIndexes & Indexes,LiveInterval & LI)817 static void determineMissingVNIs(const SlotIndexes &Indexes, LiveInterval &LI) {
818 SmallPtrSet<const MachineBasicBlock*, 5> Visited;
819
820 LiveRange::iterator OutIt;
821 VNInfo *PrevValNo = nullptr;
822 for (LiveRange::iterator I = LI.begin(), E = LI.end(); I != E; ++I) {
823 LiveRange::Segment &S = *I;
824 // Determine final VNI if necessary.
825 if (S.valno == nullptr) {
826 // This can only happen at the begin of a basic block.
827 assert(S.start.isBlock() && "valno should only be missing at block begin");
828
829 Visited.clear();
830 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(S.start);
831 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
832 VNInfo *VNI = searchForVNI(Indexes, LI, Pred, Visited);
833 if (VNI != nullptr) {
834 S.valno = VNI;
835 break;
836 }
837 }
838 assert(S.valno != nullptr && "could not determine valno");
839 }
840 // Merge with previous segment if it has the same VNI.
841 if (PrevValNo == S.valno && OutIt->end == S.start) {
842 OutIt->end = S.end;
843 } else {
844 // Didn't merge. Move OutIt to next segment.
845 if (PrevValNo == nullptr)
846 OutIt = LI.begin();
847 else
848 ++OutIt;
849
850 if (OutIt != I)
851 *OutIt = *I;
852 PrevValNo = S.valno;
853 }
854 }
855 // If we merged some segments chop off the end.
856 ++OutIt;
857 LI.segments.erase(OutIt, LI.end());
858 }
859
constructMainRangeFromSubranges(const SlotIndexes & Indexes,VNInfo::Allocator & VNIAllocator)860 void LiveInterval::constructMainRangeFromSubranges(
861 const SlotIndexes &Indexes, VNInfo::Allocator &VNIAllocator) {
862 // The basic observations on which this algorithm is based:
863 // - Each Def/ValNo in a subrange must have a corresponding def on the main
864 // range, but not further defs/valnos are necessary.
865 // - If any of the subranges is live at a point the main liverange has to be
866 // live too, conversily if no subrange is live the main range mustn't be
867 // live either.
868 // We do this by scannig through all the subranges simultaneously creating new
869 // segments in the main range as segments start/ends come up in the subranges.
870 assert(hasSubRanges() && "expected subranges to be present");
871 assert(segments.empty() && valnos.empty() && "expected empty main range");
872
873 // Collect subrange, iterator pairs for the walk and determine first and last
874 // SlotIndex involved.
875 SmallVector<std::pair<const SubRange*, const_iterator>, 4> SRs;
876 SlotIndex First;
877 SlotIndex Last;
878 for (const SubRange &SR : subranges()) {
879 if (SR.empty())
880 continue;
881 SRs.push_back(std::make_pair(&SR, SR.begin()));
882 if (!First.isValid() || SR.segments.front().start < First)
883 First = SR.segments.front().start;
884 if (!Last.isValid() || SR.segments.back().end > Last)
885 Last = SR.segments.back().end;
886 }
887
888 // Walk over all subranges simultaneously.
889 Segment CurrentSegment;
890 bool ConstructingSegment = false;
891 bool NeedVNIFixup = false;
892 unsigned ActiveMask = 0;
893 SlotIndex Pos = First;
894 while (true) {
895 SlotIndex NextPos = Last;
896 enum {
897 NOTHING,
898 BEGIN_SEGMENT,
899 END_SEGMENT,
900 } Event = NOTHING;
901 // Which subregister lanes are affected by the current event.
902 unsigned EventMask = 0;
903 // Whether a BEGIN_SEGMENT is also a valno definition point.
904 bool IsDef = false;
905 // Find the next begin or end of a subrange segment. Combine masks if we
906 // have multiple begins/ends at the same position. Ends take precedence over
907 // Begins.
908 for (auto &SRP : SRs) {
909 const SubRange &SR = *SRP.first;
910 const_iterator &I = SRP.second;
911 // Advance iterator of subrange to a segment involving Pos; the earlier
912 // segments are already merged at this point.
913 while (I != SR.end() &&
914 (I->end < Pos ||
915 (I->end == Pos && (ActiveMask & SR.LaneMask) == 0)))
916 ++I;
917 if (I == SR.end())
918 continue;
919 if ((ActiveMask & SR.LaneMask) == 0 &&
920 Pos <= I->start && I->start <= NextPos) {
921 // Merge multiple begins at the same position.
922 if (I->start == NextPos && Event == BEGIN_SEGMENT) {
923 EventMask |= SR.LaneMask;
924 IsDef |= I->valno->def == I->start;
925 } else if (I->start < NextPos || Event != END_SEGMENT) {
926 Event = BEGIN_SEGMENT;
927 NextPos = I->start;
928 EventMask = SR.LaneMask;
929 IsDef = I->valno->def == I->start;
930 }
931 }
932 if ((ActiveMask & SR.LaneMask) != 0 &&
933 Pos <= I->end && I->end <= NextPos) {
934 // Merge multiple ends at the same position.
935 if (I->end == NextPos && Event == END_SEGMENT)
936 EventMask |= SR.LaneMask;
937 else {
938 Event = END_SEGMENT;
939 NextPos = I->end;
940 EventMask = SR.LaneMask;
941 }
942 }
943 }
944
945 // Advance scan position.
946 Pos = NextPos;
947 if (Event == BEGIN_SEGMENT) {
948 if (ConstructingSegment && IsDef) {
949 // Finish previous segment because we have to start a new one.
950 CurrentSegment.end = Pos;
951 append(CurrentSegment);
952 ConstructingSegment = false;
953 }
954
955 // Start a new segment if necessary.
956 if (!ConstructingSegment) {
957 // Determine value number for the segment.
958 VNInfo *VNI;
959 if (IsDef) {
960 VNI = getNextValue(Pos, VNIAllocator);
961 } else {
962 // We have to reuse an existing value number, if we are lucky
963 // then we already passed one of the predecessor blocks and determined
964 // its value number (with blocks in reverse postorder this would be
965 // always true but we have no such guarantee).
966 assert(Pos.isBlock());
967 const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Pos);
968 // See if any of the predecessor blocks has a lower number and a VNI
969 for (const MachineBasicBlock *Pred : MBB->predecessors()) {
970 SlotIndex PredEnd = Indexes.getMBBEndIdx(Pred);
971 VNI = getVNInfoBefore(PredEnd);
972 if (VNI != nullptr)
973 break;
974 }
975 // Def will come later: We have to do an extra fixup pass.
976 if (VNI == nullptr)
977 NeedVNIFixup = true;
978 }
979
980 // In rare cases we can produce adjacent segments with the same value
981 // number (if they come from different subranges, but happen to have
982 // the same defining instruction). VNIFixup will fix those cases.
983 if (!empty() && segments.back().end == Pos &&
984 segments.back().valno == VNI)
985 NeedVNIFixup = true;
986 CurrentSegment.start = Pos;
987 CurrentSegment.valno = VNI;
988 ConstructingSegment = true;
989 }
990 ActiveMask |= EventMask;
991 } else if (Event == END_SEGMENT) {
992 assert(ConstructingSegment);
993 // Finish segment if no lane is active anymore.
994 ActiveMask &= ~EventMask;
995 if (ActiveMask == 0) {
996 CurrentSegment.end = Pos;
997 append(CurrentSegment);
998 ConstructingSegment = false;
999 }
1000 } else {
1001 // We reached the end of the last subranges and can stop.
1002 assert(Event == NOTHING);
1003 break;
1004 }
1005 }
1006
1007 // We might not be able to assign new valnos for all segments if the basic
1008 // block containing the definition comes after a segment using the valno.
1009 // Do a fixup pass for this uncommon case.
1010 if (NeedVNIFixup)
1011 determineMissingVNIs(Indexes, *this);
1012
1013 assert(ActiveMask == 0 && !ConstructingSegment && "all segments ended");
1014 verify();
1015 }
1016
getSize() const1017 unsigned LiveInterval::getSize() const {
1018 unsigned Sum = 0;
1019 for (const Segment &S : segments)
1020 Sum += S.start.distance(S.end);
1021 return Sum;
1022 }
1023
operator <<(raw_ostream & os,const LiveRange::Segment & S)1024 raw_ostream& llvm::operator<<(raw_ostream& os, const LiveRange::Segment &S) {
1025 return os << '[' << S.start << ',' << S.end << ':' << S.valno->id << ")";
1026 }
1027
1028 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const1029 void LiveRange::Segment::dump() const {
1030 dbgs() << *this << "\n";
1031 }
1032 #endif
1033
print(raw_ostream & OS) const1034 void LiveRange::print(raw_ostream &OS) const {
1035 if (empty())
1036 OS << "EMPTY";
1037 else {
1038 for (const Segment &S : segments) {
1039 OS << S;
1040 assert(S.valno == getValNumInfo(S.valno->id) && "Bad VNInfo");
1041 }
1042 }
1043
1044 // Print value number info.
1045 if (getNumValNums()) {
1046 OS << " ";
1047 unsigned vnum = 0;
1048 for (const_vni_iterator i = vni_begin(), e = vni_end(); i != e;
1049 ++i, ++vnum) {
1050 const VNInfo *vni = *i;
1051 if (vnum) OS << " ";
1052 OS << vnum << "@";
1053 if (vni->isUnused()) {
1054 OS << "x";
1055 } else {
1056 OS << vni->def;
1057 if (vni->isPHIDef())
1058 OS << "-phi";
1059 }
1060 }
1061 }
1062 }
1063
print(raw_ostream & OS) const1064 void LiveInterval::print(raw_ostream &OS) const {
1065 OS << PrintReg(reg) << ' ';
1066 super::print(OS);
1067 // Print subranges
1068 for (const SubRange &SR : subranges()) {
1069 OS << format(" L%04X ", SR.LaneMask) << SR;
1070 }
1071 }
1072
1073 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const1074 void LiveRange::dump() const {
1075 dbgs() << *this << "\n";
1076 }
1077
dump() const1078 void LiveInterval::dump() const {
1079 dbgs() << *this << "\n";
1080 }
1081 #endif
1082
1083 #ifndef NDEBUG
verify() const1084 void LiveRange::verify() const {
1085 for (const_iterator I = begin(), E = end(); I != E; ++I) {
1086 assert(I->start.isValid());
1087 assert(I->end.isValid());
1088 assert(I->start < I->end);
1089 assert(I->valno != nullptr);
1090 assert(I->valno->id < valnos.size());
1091 assert(I->valno == valnos[I->valno->id]);
1092 if (std::next(I) != E) {
1093 assert(I->end <= std::next(I)->start);
1094 if (I->end == std::next(I)->start)
1095 assert(I->valno != std::next(I)->valno);
1096 }
1097 }
1098 }
1099
verify(const MachineRegisterInfo * MRI) const1100 void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
1101 super::verify();
1102
1103 // Make sure SubRanges are fine and LaneMasks are disjunct.
1104 unsigned Mask = 0;
1105 unsigned MaxMask = MRI != nullptr ? MRI->getMaxLaneMaskForVReg(reg) : ~0u;
1106 for (const SubRange &SR : subranges()) {
1107 // Subrange lanemask should be disjunct to any previous subrange masks.
1108 assert((Mask & SR.LaneMask) == 0);
1109 Mask |= SR.LaneMask;
1110
1111 // subrange mask should not contained in maximum lane mask for the vreg.
1112 assert((Mask & ~MaxMask) == 0);
1113
1114 SR.verify();
1115 // Main liverange should cover subrange.
1116 assert(covers(SR));
1117 }
1118 }
1119 #endif
1120
1121
1122 //===----------------------------------------------------------------------===//
1123 // LiveRangeUpdater class
1124 //===----------------------------------------------------------------------===//
1125 //
1126 // The LiveRangeUpdater class always maintains these invariants:
1127 //
1128 // - When LastStart is invalid, Spills is empty and the iterators are invalid.
1129 // This is the initial state, and the state created by flush().
1130 // In this state, isDirty() returns false.
1131 //
1132 // Otherwise, segments are kept in three separate areas:
1133 //
1134 // 1. [begin; WriteI) at the front of LR.
1135 // 2. [ReadI; end) at the back of LR.
1136 // 3. Spills.
1137 //
1138 // - LR.begin() <= WriteI <= ReadI <= LR.end().
1139 // - Segments in all three areas are fully ordered and coalesced.
1140 // - Segments in area 1 precede and can't coalesce with segments in area 2.
1141 // - Segments in Spills precede and can't coalesce with segments in area 2.
1142 // - No coalescing is possible between segments in Spills and segments in area
1143 // 1, and there are no overlapping segments.
1144 //
1145 // The segments in Spills are not ordered with respect to the segments in area
1146 // 1. They need to be merged.
1147 //
1148 // When they exist, Spills.back().start <= LastStart,
1149 // and WriteI[-1].start <= LastStart.
1150
print(raw_ostream & OS) const1151 void LiveRangeUpdater::print(raw_ostream &OS) const {
1152 if (!isDirty()) {
1153 if (LR)
1154 OS << "Clean updater: " << *LR << '\n';
1155 else
1156 OS << "Null updater.\n";
1157 return;
1158 }
1159 assert(LR && "Can't have null LR in dirty updater.");
1160 OS << " updater with gap = " << (ReadI - WriteI)
1161 << ", last start = " << LastStart
1162 << ":\n Area 1:";
1163 for (const auto &S : make_range(LR->begin(), WriteI))
1164 OS << ' ' << S;
1165 OS << "\n Spills:";
1166 for (unsigned I = 0, E = Spills.size(); I != E; ++I)
1167 OS << ' ' << Spills[I];
1168 OS << "\n Area 2:";
1169 for (const auto &S : make_range(ReadI, LR->end()))
1170 OS << ' ' << S;
1171 OS << '\n';
1172 }
1173
dump() const1174 void LiveRangeUpdater::dump() const
1175 {
1176 print(errs());
1177 }
1178
1179 // Determine if A and B should be coalesced.
coalescable(const LiveRange::Segment & A,const LiveRange::Segment & B)1180 static inline bool coalescable(const LiveRange::Segment &A,
1181 const LiveRange::Segment &B) {
1182 assert(A.start <= B.start && "Unordered live segments.");
1183 if (A.end == B.start)
1184 return A.valno == B.valno;
1185 if (A.end < B.start)
1186 return false;
1187 assert(A.valno == B.valno && "Cannot overlap different values");
1188 return true;
1189 }
1190
add(LiveRange::Segment Seg)1191 void LiveRangeUpdater::add(LiveRange::Segment Seg) {
1192 assert(LR && "Cannot add to a null destination");
1193
1194 // Fall back to the regular add method if the live range
1195 // is using the segment set instead of the segment vector.
1196 if (LR->segmentSet != nullptr) {
1197 LR->addSegmentToSet(Seg);
1198 return;
1199 }
1200
1201 // Flush the state if Start moves backwards.
1202 if (!LastStart.isValid() || LastStart > Seg.start) {
1203 if (isDirty())
1204 flush();
1205 // This brings us to an uninitialized state. Reinitialize.
1206 assert(Spills.empty() && "Leftover spilled segments");
1207 WriteI = ReadI = LR->begin();
1208 }
1209
1210 // Remember start for next time.
1211 LastStart = Seg.start;
1212
1213 // Advance ReadI until it ends after Seg.start.
1214 LiveRange::iterator E = LR->end();
1215 if (ReadI != E && ReadI->end <= Seg.start) {
1216 // First try to close the gap between WriteI and ReadI with spills.
1217 if (ReadI != WriteI)
1218 mergeSpills();
1219 // Then advance ReadI.
1220 if (ReadI == WriteI)
1221 ReadI = WriteI = LR->find(Seg.start);
1222 else
1223 while (ReadI != E && ReadI->end <= Seg.start)
1224 *WriteI++ = *ReadI++;
1225 }
1226
1227 assert(ReadI == E || ReadI->end > Seg.start);
1228
1229 // Check if the ReadI segment begins early.
1230 if (ReadI != E && ReadI->start <= Seg.start) {
1231 assert(ReadI->valno == Seg.valno && "Cannot overlap different values");
1232 // Bail if Seg is completely contained in ReadI.
1233 if (ReadI->end >= Seg.end)
1234 return;
1235 // Coalesce into Seg.
1236 Seg.start = ReadI->start;
1237 ++ReadI;
1238 }
1239
1240 // Coalesce as much as possible from ReadI into Seg.
1241 while (ReadI != E && coalescable(Seg, *ReadI)) {
1242 Seg.end = std::max(Seg.end, ReadI->end);
1243 ++ReadI;
1244 }
1245
1246 // Try coalescing Spills.back() into Seg.
1247 if (!Spills.empty() && coalescable(Spills.back(), Seg)) {
1248 Seg.start = Spills.back().start;
1249 Seg.end = std::max(Spills.back().end, Seg.end);
1250 Spills.pop_back();
1251 }
1252
1253 // Try coalescing Seg into WriteI[-1].
1254 if (WriteI != LR->begin() && coalescable(WriteI[-1], Seg)) {
1255 WriteI[-1].end = std::max(WriteI[-1].end, Seg.end);
1256 return;
1257 }
1258
1259 // Seg doesn't coalesce with anything, and needs to be inserted somewhere.
1260 if (WriteI != ReadI) {
1261 *WriteI++ = Seg;
1262 return;
1263 }
1264
1265 // Finally, append to LR or Spills.
1266 if (WriteI == E) {
1267 LR->segments.push_back(Seg);
1268 WriteI = ReadI = LR->end();
1269 } else
1270 Spills.push_back(Seg);
1271 }
1272
1273 // Merge as many spilled segments as possible into the gap between WriteI
1274 // and ReadI. Advance WriteI to reflect the inserted instructions.
mergeSpills()1275 void LiveRangeUpdater::mergeSpills() {
1276 // Perform a backwards merge of Spills and [SpillI;WriteI).
1277 size_t GapSize = ReadI - WriteI;
1278 size_t NumMoved = std::min(Spills.size(), GapSize);
1279 LiveRange::iterator Src = WriteI;
1280 LiveRange::iterator Dst = Src + NumMoved;
1281 LiveRange::iterator SpillSrc = Spills.end();
1282 LiveRange::iterator B = LR->begin();
1283
1284 // This is the new WriteI position after merging spills.
1285 WriteI = Dst;
1286
1287 // Now merge Src and Spills backwards.
1288 while (Src != Dst) {
1289 if (Src != B && Src[-1].start > SpillSrc[-1].start)
1290 *--Dst = *--Src;
1291 else
1292 *--Dst = *--SpillSrc;
1293 }
1294 assert(NumMoved == size_t(Spills.end() - SpillSrc));
1295 Spills.erase(SpillSrc, Spills.end());
1296 }
1297
flush()1298 void LiveRangeUpdater::flush() {
1299 if (!isDirty())
1300 return;
1301 // Clear the dirty state.
1302 LastStart = SlotIndex();
1303
1304 assert(LR && "Cannot add to a null destination");
1305
1306 // Nothing to merge?
1307 if (Spills.empty()) {
1308 LR->segments.erase(WriteI, ReadI);
1309 LR->verify();
1310 return;
1311 }
1312
1313 // Resize the WriteI - ReadI gap to match Spills.
1314 size_t GapSize = ReadI - WriteI;
1315 if (GapSize < Spills.size()) {
1316 // The gap is too small. Make some room.
1317 size_t WritePos = WriteI - LR->begin();
1318 LR->segments.insert(ReadI, Spills.size() - GapSize, LiveRange::Segment());
1319 // This also invalidated ReadI, but it is recomputed below.
1320 WriteI = LR->begin() + WritePos;
1321 } else {
1322 // Shrink the gap if necessary.
1323 LR->segments.erase(WriteI + Spills.size(), ReadI);
1324 }
1325 ReadI = WriteI + Spills.size();
1326 mergeSpills();
1327 LR->verify();
1328 }
1329
Classify(const LiveInterval * LI)1330 unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
1331 // Create initial equivalence classes.
1332 EqClass.clear();
1333 EqClass.grow(LI->getNumValNums());
1334
1335 const VNInfo *used = nullptr, *unused = nullptr;
1336
1337 // Determine connections.
1338 for (const VNInfo *VNI : LI->valnos) {
1339 // Group all unused values into one class.
1340 if (VNI->isUnused()) {
1341 if (unused)
1342 EqClass.join(unused->id, VNI->id);
1343 unused = VNI;
1344 continue;
1345 }
1346 used = VNI;
1347 if (VNI->isPHIDef()) {
1348 const MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def);
1349 assert(MBB && "Phi-def has no defining MBB");
1350 // Connect to values live out of predecessors.
1351 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
1352 PE = MBB->pred_end(); PI != PE; ++PI)
1353 if (const VNInfo *PVNI = LI->getVNInfoBefore(LIS.getMBBEndIdx(*PI)))
1354 EqClass.join(VNI->id, PVNI->id);
1355 } else {
1356 // Normal value defined by an instruction. Check for two-addr redef.
1357 // FIXME: This could be coincidental. Should we really check for a tied
1358 // operand constraint?
1359 // Note that VNI->def may be a use slot for an early clobber def.
1360 if (const VNInfo *UVNI = LI->getVNInfoBefore(VNI->def))
1361 EqClass.join(VNI->id, UVNI->id);
1362 }
1363 }
1364
1365 // Lump all the unused values in with the last used value.
1366 if (used && unused)
1367 EqClass.join(used->id, unused->id);
1368
1369 EqClass.compress();
1370 return EqClass.getNumClasses();
1371 }
1372
Distribute(LiveInterval * LIV[],MachineRegisterInfo & MRI)1373 void ConnectedVNInfoEqClasses::Distribute(LiveInterval *LIV[],
1374 MachineRegisterInfo &MRI) {
1375 assert(LIV[0] && "LIV[0] must be set");
1376 LiveInterval &LI = *LIV[0];
1377
1378 // Rewrite instructions.
1379 for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
1380 RE = MRI.reg_end(); RI != RE;) {
1381 MachineOperand &MO = *RI;
1382 MachineInstr *MI = RI->getParent();
1383 ++RI;
1384 // DBG_VALUE instructions don't have slot indexes, so get the index of the
1385 // instruction before them.
1386 // Normally, DBG_VALUE instructions are removed before this function is
1387 // called, but it is not a requirement.
1388 SlotIndex Idx;
1389 if (MI->isDebugValue())
1390 Idx = LIS.getSlotIndexes()->getIndexBefore(MI);
1391 else
1392 Idx = LIS.getInstructionIndex(MI);
1393 LiveQueryResult LRQ = LI.Query(Idx);
1394 const VNInfo *VNI = MO.readsReg() ? LRQ.valueIn() : LRQ.valueDefined();
1395 // In the case of an <undef> use that isn't tied to any def, VNI will be
1396 // NULL. If the use is tied to a def, VNI will be the defined value.
1397 if (!VNI)
1398 continue;
1399 MO.setReg(LIV[getEqClass(VNI)]->reg);
1400 }
1401
1402 // Move runs to new intervals.
1403 LiveInterval::iterator J = LI.begin(), E = LI.end();
1404 while (J != E && EqClass[J->valno->id] == 0)
1405 ++J;
1406 for (LiveInterval::iterator I = J; I != E; ++I) {
1407 if (unsigned eq = EqClass[I->valno->id]) {
1408 assert((LIV[eq]->empty() || LIV[eq]->expiredAt(I->start)) &&
1409 "New intervals should be empty");
1410 LIV[eq]->segments.push_back(*I);
1411 } else
1412 *J++ = *I;
1413 }
1414 // TODO: do not cheat anymore by simply cleaning all subranges
1415 LI.clearSubRanges();
1416 LI.segments.erase(J, E);
1417
1418 // Transfer VNInfos to their new owners and renumber them.
1419 unsigned j = 0, e = LI.getNumValNums();
1420 while (j != e && EqClass[j] == 0)
1421 ++j;
1422 for (unsigned i = j; i != e; ++i) {
1423 VNInfo *VNI = LI.getValNumInfo(i);
1424 if (unsigned eq = EqClass[i]) {
1425 VNI->id = LIV[eq]->getNumValNums();
1426 LIV[eq]->valnos.push_back(VNI);
1427 } else {
1428 VNI->id = j;
1429 LI.valnos[j++] = VNI;
1430 }
1431 }
1432 LI.valnos.resize(j);
1433 }
1434