1 //===-- llvm/CodeGen/LiveInterval.h - Interval representation ---*- C++ -*-===//
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 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.
19 //===----------------------------------------------------------------------===//
21 #ifndef LLVM_CODEGEN_LIVEINTERVAL_H
22 #define LLVM_CODEGEN_LIVEINTERVAL_H
24 #include "llvm/ADT/IntEqClasses.h"
25 #include "llvm/CodeGen/SlotIndexes.h"
26 #include "llvm/Support/AlignOf.h"
27 #include "llvm/Support/Allocator.h"
35 class MachineRegisterInfo;
36 class TargetRegisterInfo;
38 template <typename T, unsigned Small> class SmallPtrSet;
40 /// VNInfo - Value Number Information.
41 /// This class holds information about a machine level values, including
42 /// definition and use points.
46 typedef BumpPtrAllocator Allocator;
48 /// The ID number of this value.
51 /// The index of the defining instruction.
54 /// VNInfo constructor.
55 VNInfo(unsigned i, SlotIndex d)
59 /// VNInfo construtor, copies values from orig, except for the value number.
60 VNInfo(unsigned i, const VNInfo &orig)
61 : id(i), def(orig.def)
64 /// Copy from the parameter into this VNInfo.
65 void copyFrom(VNInfo &src) {
69 /// Returns true if this value is defined by a PHI instruction (or was,
70 /// PHI instructions may have been eliminated).
71 /// PHI-defs begin at a block boundary, all other defs begin at register or
73 bool isPHIDef() const { return def.isBlock(); }
75 /// Returns true if this value is unused.
76 bool isUnused() const { return !def.isValid(); }
78 /// Mark this value as unused.
79 void markUnused() { def = SlotIndex(); }
82 /// Result of a LiveRange query. This class hides the implementation details
83 /// of live ranges, and it should be used as the primary interface for
84 /// examining live ranges around instructions.
85 class LiveQueryResult {
86 VNInfo *const EarlyVal;
87 VNInfo *const LateVal;
88 const SlotIndex EndPoint;
92 LiveQueryResult(VNInfo *EarlyVal, VNInfo *LateVal, SlotIndex EndPoint,
94 : EarlyVal(EarlyVal), LateVal(LateVal), EndPoint(EndPoint), Kill(Kill)
97 /// Return the value that is live-in to the instruction. This is the value
98 /// that will be read by the instruction's use operands. Return NULL if no
100 VNInfo *valueIn() const {
104 /// Return true if the live-in value is killed by this instruction. This
105 /// means that either the live range ends at the instruction, or it changes
107 bool isKill() const {
111 /// Return true if this instruction has a dead def.
112 bool isDeadDef() const {
113 return EndPoint.isDead();
116 /// Return the value leaving the instruction, if any. This can be a
117 /// live-through value, or a live def. A dead def returns NULL.
118 VNInfo *valueOut() const {
119 return isDeadDef() ? nullptr : LateVal;
122 /// Return the value defined by this instruction, if any. This includes
123 /// dead defs, it is the value created by the instruction's def operands.
124 VNInfo *valueDefined() const {
125 return EarlyVal == LateVal ? nullptr : LateVal;
128 /// Return the end point of the last live range segment to interact with
129 /// the instruction, if any.
131 /// The end point is an invalid SlotIndex only if the live range doesn't
132 /// intersect the instruction at all.
134 /// The end point may be at or past the end of the instruction's basic
135 /// block. That means the value was live out of the block.
136 SlotIndex endPoint() const {
141 /// This class represents the liveness of a register, stack slot, etc.
142 /// It manages an ordered list of Segment objects.
143 /// The Segments are organized in a static single assignment form: At places
144 /// where a new value is defined or different values reach a CFG join a new
145 /// segment with a new value number is used.
149 /// This represents a simple continuous liveness interval for a value.
150 /// The start point is inclusive, the end point exclusive. These intervals
151 /// are rendered as [start,end).
153 SlotIndex start; // Start point of the interval (inclusive)
154 SlotIndex end; // End point of the interval (exclusive)
155 VNInfo *valno; // identifier for the value contained in this segment.
157 Segment() : valno(nullptr) {}
159 Segment(SlotIndex S, SlotIndex E, VNInfo *V)
160 : start(S), end(E), valno(V) {
161 assert(S < E && "Cannot create empty or backwards segment");
164 /// Return true if the index is covered by this segment.
165 bool contains(SlotIndex I) const {
166 return start <= I && I < end;
169 /// Return true if the given interval, [S, E), is covered by this segment.
170 bool containsInterval(SlotIndex S, SlotIndex E) const {
171 assert((S < E) && "Backwards interval?");
172 return (start <= S && S < end) && (start < E && E <= end);
175 bool operator<(const Segment &Other) const {
176 return std::tie(start, end) < std::tie(Other.start, Other.end);
178 bool operator==(const Segment &Other) const {
179 return start == Other.start && end == Other.end;
185 typedef SmallVector<Segment,4> Segments;
186 typedef SmallVector<VNInfo*,4> VNInfoList;
188 Segments segments; // the liveness segments
189 VNInfoList valnos; // value#'s
191 typedef Segments::iterator iterator;
192 iterator begin() { return segments.begin(); }
193 iterator end() { return segments.end(); }
195 typedef Segments::const_iterator const_iterator;
196 const_iterator begin() const { return segments.begin(); }
197 const_iterator end() const { return segments.end(); }
199 typedef VNInfoList::iterator vni_iterator;
200 vni_iterator vni_begin() { return valnos.begin(); }
201 vni_iterator vni_end() { return valnos.end(); }
203 typedef VNInfoList::const_iterator const_vni_iterator;
204 const_vni_iterator vni_begin() const { return valnos.begin(); }
205 const_vni_iterator vni_end() const { return valnos.end(); }
207 /// advanceTo - Advance the specified iterator to point to the Segment
208 /// containing the specified position, or end() if the position is past the
209 /// end of the range. If no Segment contains this position, but the
210 /// position is in a hole, this method returns an iterator pointing to the
211 /// Segment immediately after the hole.
212 iterator advanceTo(iterator I, SlotIndex Pos) {
214 if (Pos >= endIndex())
216 while (I->end <= Pos) ++I;
220 /// find - Return an iterator pointing to the first segment that ends after
221 /// Pos, or end(). This is the same as advanceTo(begin(), Pos), but faster
222 /// when searching large ranges.
224 /// If Pos is contained in a Segment, that segment is returned.
225 /// If Pos is in a hole, the following Segment is returned.
226 /// If Pos is beyond endIndex, end() is returned.
227 iterator find(SlotIndex Pos);
229 const_iterator find(SlotIndex Pos) const {
230 return const_cast<LiveRange*>(this)->find(Pos);
238 size_t size() const {
239 return segments.size();
242 bool hasAtLeastOneValue() const { return !valnos.empty(); }
244 bool containsOneValue() const { return valnos.size() == 1; }
246 unsigned getNumValNums() const { return (unsigned)valnos.size(); }
248 /// getValNumInfo - Returns pointer to the specified val#.
250 inline VNInfo *getValNumInfo(unsigned ValNo) {
251 return valnos[ValNo];
253 inline const VNInfo *getValNumInfo(unsigned ValNo) const {
254 return valnos[ValNo];
257 /// containsValue - Returns true if VNI belongs to this range.
258 bool containsValue(const VNInfo *VNI) const {
259 return VNI && VNI->id < getNumValNums() && VNI == getValNumInfo(VNI->id);
262 /// getNextValue - Create a new value number and return it. MIIdx specifies
263 /// the instruction that defines the value number.
264 VNInfo *getNextValue(SlotIndex def, VNInfo::Allocator &VNInfoAllocator) {
266 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), def);
267 valnos.push_back(VNI);
271 /// createDeadDef - Make sure the range has a value defined at Def.
272 /// If one already exists, return it. Otherwise allocate a new value and
273 /// add liveness for a dead def.
274 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator);
276 /// Create a copy of the given value. The new value will be identical except
277 /// for the Value number.
278 VNInfo *createValueCopy(const VNInfo *orig,
279 VNInfo::Allocator &VNInfoAllocator) {
281 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), *orig);
282 valnos.push_back(VNI);
286 /// RenumberValues - Renumber all values in order of appearance and remove
288 void RenumberValues();
290 /// MergeValueNumberInto - This method is called when two value numbers
291 /// are found to be equivalent. This eliminates V1, replacing all
292 /// segments with the V1 value number with the V2 value number. This can
293 /// cause merging of V1/V2 values numbers and compaction of the value space.
294 VNInfo* MergeValueNumberInto(VNInfo *V1, VNInfo *V2);
296 /// Merge all of the live segments of a specific val# in RHS into this live
297 /// range as the specified value number. The segments in RHS are allowed
298 /// to overlap with segments in the current range, it will replace the
299 /// value numbers of the overlaped live segments with the specified value
301 void MergeSegmentsInAsValue(const LiveRange &RHS, VNInfo *LHSValNo);
303 /// MergeValueInAsValue - Merge all of the segments of a specific val#
304 /// in RHS into this live range as the specified value number.
305 /// The segments in RHS are allowed to overlap with segments in the
306 /// current range, but only if the overlapping segments have the
307 /// specified value number.
308 void MergeValueInAsValue(const LiveRange &RHS,
309 const VNInfo *RHSValNo, VNInfo *LHSValNo);
311 bool empty() const { return segments.empty(); }
313 /// beginIndex - Return the lowest numbered slot covered.
314 SlotIndex beginIndex() const {
315 assert(!empty() && "Call to beginIndex() on empty range.");
316 return segments.front().start;
319 /// endNumber - return the maximum point of the range of the whole,
321 SlotIndex endIndex() const {
322 assert(!empty() && "Call to endIndex() on empty range.");
323 return segments.back().end;
326 bool expiredAt(SlotIndex index) const {
327 return index >= endIndex();
330 bool liveAt(SlotIndex index) const {
331 const_iterator r = find(index);
332 return r != end() && r->start <= index;
335 /// Return the segment that contains the specified index, or null if there
337 const Segment *getSegmentContaining(SlotIndex Idx) const {
338 const_iterator I = FindSegmentContaining(Idx);
339 return I == end() ? nullptr : &*I;
342 /// Return the live segment that contains the specified index, or null if
344 Segment *getSegmentContaining(SlotIndex Idx) {
345 iterator I = FindSegmentContaining(Idx);
346 return I == end() ? nullptr : &*I;
349 /// getVNInfoAt - Return the VNInfo that is live at Idx, or NULL.
350 VNInfo *getVNInfoAt(SlotIndex Idx) const {
351 const_iterator I = FindSegmentContaining(Idx);
352 return I == end() ? nullptr : I->valno;
355 /// getVNInfoBefore - Return the VNInfo that is live up to but not
356 /// necessarilly including Idx, or NULL. Use this to find the reaching def
357 /// used by an instruction at this SlotIndex position.
358 VNInfo *getVNInfoBefore(SlotIndex Idx) const {
359 const_iterator I = FindSegmentContaining(Idx.getPrevSlot());
360 return I == end() ? nullptr : I->valno;
363 /// Return an iterator to the segment that contains the specified index, or
364 /// end() if there is none.
365 iterator FindSegmentContaining(SlotIndex Idx) {
366 iterator I = find(Idx);
367 return I != end() && I->start <= Idx ? I : end();
370 const_iterator FindSegmentContaining(SlotIndex Idx) const {
371 const_iterator I = find(Idx);
372 return I != end() && I->start <= Idx ? I : end();
375 /// overlaps - Return true if the intersection of the two live ranges is
377 bool overlaps(const LiveRange &other) const {
380 return overlapsFrom(other, other.begin());
383 /// overlaps - Return true if the two ranges have overlapping segments
384 /// that are not coalescable according to CP.
386 /// Overlapping segments where one range is defined by a coalescable
387 /// copy are allowed.
388 bool overlaps(const LiveRange &Other, const CoalescerPair &CP,
389 const SlotIndexes&) const;
391 /// overlaps - Return true if the live range overlaps an interval specified
393 bool overlaps(SlotIndex Start, SlotIndex End) const;
395 /// overlapsFrom - Return true if the intersection of the two live ranges
396 /// is not empty. The specified iterator is a hint that we can begin
397 /// scanning the Other range starting at I.
398 bool overlapsFrom(const LiveRange &Other, const_iterator I) const;
400 /// Add the specified Segment to this range, merging segments as
401 /// appropriate. This returns an iterator to the inserted segment (which
402 /// may have grown since it was inserted).
403 iterator addSegment(Segment S) {
404 return addSegmentFrom(S, segments.begin());
407 /// extendInBlock - If this range is live before Kill in the basic block
408 /// that starts at StartIdx, extend it to be live up to Kill, and return
409 /// the value. If there is no segment before Kill, return NULL.
410 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Kill);
412 /// join - Join two live ranges (this, and other) together. This applies
413 /// mappings to the value numbers in the LHS/RHS ranges as specified. If
414 /// the ranges are not joinable, this aborts.
415 void join(LiveRange &Other,
416 const int *ValNoAssignments,
417 const int *RHSValNoAssignments,
418 SmallVectorImpl<VNInfo *> &NewVNInfo);
420 /// True iff this segment is a single segment that lies between the
421 /// specified boundaries, exclusively. Vregs live across a backedge are not
422 /// considered local. The boundaries are expected to lie within an extended
423 /// basic block, so vregs that are not live out should contain no holes.
424 bool isLocal(SlotIndex Start, SlotIndex End) const {
425 return beginIndex() > Start.getBaseIndex() &&
426 endIndex() < End.getBoundaryIndex();
429 /// Remove the specified segment from this range. Note that the segment
430 /// must be a single Segment in its entirety.
431 void removeSegment(SlotIndex Start, SlotIndex End,
432 bool RemoveDeadValNo = false);
434 void removeSegment(Segment S, bool RemoveDeadValNo = false) {
435 removeSegment(S.start, S.end, RemoveDeadValNo);
438 /// Query Liveness at Idx.
439 /// The sub-instruction slot of Idx doesn't matter, only the instruction
440 /// it refers to is considered.
441 LiveQueryResult Query(SlotIndex Idx) const {
442 // Find the segment that enters the instruction.
443 const_iterator I = find(Idx.getBaseIndex());
444 const_iterator E = end();
446 return LiveQueryResult(nullptr, nullptr, SlotIndex(), false);
448 // Is this an instruction live-in segment?
449 // If Idx is the start index of a basic block, include live-in segments
450 // that start at Idx.getBaseIndex().
451 VNInfo *EarlyVal = nullptr;
452 VNInfo *LateVal = nullptr;
455 if (I->start <= Idx.getBaseIndex()) {
458 // Move to the potentially live-out segment.
459 if (SlotIndex::isSameInstr(Idx, I->end)) {
462 return LiveQueryResult(EarlyVal, LateVal, EndPoint, Kill);
464 // Special case: A PHIDef value can have its def in the middle of a
465 // segment if the value happens to be live out of the layout
467 // Such a value is not live-in.
468 if (EarlyVal->def == Idx.getBaseIndex())
471 // I now points to the segment that may be live-through, or defined by
472 // this instr. Ignore segments starting after the current instr.
473 if (!SlotIndex::isEarlierInstr(Idx, I->start)) {
477 return LiveQueryResult(EarlyVal, LateVal, EndPoint, Kill);
480 /// removeValNo - Remove all the segments defined by the specified value#.
481 /// Also remove the value# from value# list.
482 void removeValNo(VNInfo *ValNo);
484 /// Returns true if the live range is zero length, i.e. no live segments
485 /// span instructions. It doesn't pay to spill such a range.
486 bool isZeroLength(SlotIndexes *Indexes) const {
487 for (const_iterator i = begin(), e = end(); i != e; ++i)
488 if (Indexes->getNextNonNullIndex(i->start).getBaseIndex() <
489 i->end.getBaseIndex())
494 bool operator<(const LiveRange& other) const {
495 const SlotIndex &thisIndex = beginIndex();
496 const SlotIndex &otherIndex = other.beginIndex();
497 return thisIndex < otherIndex;
500 void print(raw_ostream &OS) const;
503 /// \brief Walk the range and assert if any invariants fail to hold.
505 /// Note that this is a no-op when asserts are disabled.
507 void verify() const {}
514 iterator addSegmentFrom(Segment S, iterator From);
515 void extendSegmentEndTo(iterator I, SlotIndex NewEnd);
516 iterator extendSegmentStartTo(iterator I, SlotIndex NewStr);
517 void markValNoForDeletion(VNInfo *V);
521 inline raw_ostream &operator<<(raw_ostream &OS, const LiveRange &LR) {
526 /// LiveInterval - This class represents the liveness of a register,
528 class LiveInterval : public LiveRange {
530 typedef LiveRange super;
532 const unsigned reg; // the register or stack slot of this interval.
533 float weight; // weight of this interval
535 LiveInterval(unsigned Reg, float Weight)
536 : reg(Reg), weight(Weight) {}
538 /// getSize - Returns the sum of sizes of all the LiveRange's.
540 unsigned getSize() const;
542 /// isSpillable - Can this interval be spilled?
543 bool isSpillable() const {
544 return weight != llvm::huge_valf;
547 /// markNotSpillable - Mark interval as not spillable
548 void markNotSpillable() {
549 weight = llvm::huge_valf;
552 bool operator<(const LiveInterval& other) const {
553 const SlotIndex &thisIndex = beginIndex();
554 const SlotIndex &otherIndex = other.beginIndex();
555 return std::tie(thisIndex, reg) < std::tie(otherIndex, other.reg);
558 void print(raw_ostream &OS) const;
562 LiveInterval& operator=(const LiveInterval& rhs) LLVM_DELETED_FUNCTION;
566 inline raw_ostream &operator<<(raw_ostream &OS, const LiveInterval &LI) {
571 raw_ostream &operator<<(raw_ostream &OS, const LiveRange::Segment &S);
573 inline bool operator<(SlotIndex V, const LiveRange::Segment &S) {
577 inline bool operator<(const LiveRange::Segment &S, SlotIndex V) {
581 /// Helper class for performant LiveRange bulk updates.
583 /// Calling LiveRange::addSegment() repeatedly can be expensive on large
584 /// live ranges because segments after the insertion point may need to be
585 /// shifted. The LiveRangeUpdater class can defer the shifting when adding
586 /// many segments in order.
588 /// The LiveRange will be in an invalid state until flush() is called.
589 class LiveRangeUpdater {
592 LiveRange::iterator WriteI;
593 LiveRange::iterator ReadI;
594 SmallVector<LiveRange::Segment, 16> Spills;
598 /// Create a LiveRangeUpdater for adding segments to LR.
599 /// LR will temporarily be in an invalid state until flush() is called.
600 LiveRangeUpdater(LiveRange *lr = nullptr) : LR(lr) {}
602 ~LiveRangeUpdater() { flush(); }
604 /// Add a segment to LR and coalesce when possible, just like
605 /// LR.addSegment(). Segments should be added in increasing start order for
606 /// best performance.
607 void add(LiveRange::Segment);
609 void add(SlotIndex Start, SlotIndex End, VNInfo *VNI) {
610 add(LiveRange::Segment(Start, End, VNI));
613 /// Return true if the LR is currently in an invalid state, and flush()
614 /// needs to be called.
615 bool isDirty() const { return LastStart.isValid(); }
617 /// Flush the updater state to LR so it is valid and contains all added
621 /// Select a different destination live range.
622 void setDest(LiveRange *lr) {
623 if (LR != lr && isDirty())
628 /// Get the current destination live range.
629 LiveRange *getDest() const { return LR; }
632 void print(raw_ostream&) const;
635 inline raw_ostream &operator<<(raw_ostream &OS, const LiveRangeUpdater &X) {
640 /// ConnectedVNInfoEqClasses - Helper class that can divide VNInfos in a
641 /// LiveInterval into equivalence clases of connected components. A
642 /// LiveInterval that has multiple connected components can be broken into
643 /// multiple LiveIntervals.
645 /// Given a LiveInterval that may have multiple connected components, run:
647 /// unsigned numComps = ConEQ.Classify(LI);
648 /// if (numComps > 1) {
649 /// // allocate numComps-1 new LiveIntervals into LIS[1..]
650 /// ConEQ.Distribute(LIS);
653 class ConnectedVNInfoEqClasses {
655 IntEqClasses EqClass;
657 // Note that values a and b are connected.
658 void Connect(unsigned a, unsigned b);
663 explicit ConnectedVNInfoEqClasses(LiveIntervals &lis) : LIS(lis) {}
665 /// Classify - Classify the values in LI into connected components.
666 /// Return the number of connected components.
667 unsigned Classify(const LiveInterval *LI);
669 /// getEqClass - Classify creates equivalence classes numbered 0..N. Return
670 /// the equivalence class assigned the VNI.
671 unsigned getEqClass(const VNInfo *VNI) const { return EqClass[VNI->id]; }
673 /// Distribute - Distribute values in LIV[0] into a separate LiveInterval
674 /// for each connected component. LIV must have a LiveInterval for each
675 /// connected component. The LiveIntervals in Liv[1..] must be empty.
676 /// Instructions using LIV[0] are rewritten.
677 void Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI);