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 /// This class represents the liveness of a register, stack slot, etc.
83 /// It manages an ordered list of Segment objects.
84 /// The Segments are organized in a static single assignment form: At places
85 /// where a new value is defined or different values reach a CFG join a new
86 /// segment with a new value number is used.
90 /// This represents a simple continuous liveness interval for a value.
91 /// The start point is inclusive, the end point exclusive. These intervals
92 /// are rendered as [start,end).
94 SlotIndex start; // Start point of the interval (inclusive)
95 SlotIndex end; // End point of the interval (exclusive)
96 VNInfo *valno; // identifier for the value contained in this segment.
98 Segment() : valno(0) {}
100 Segment(SlotIndex S, SlotIndex E, VNInfo *V)
101 : start(S), end(E), valno(V) {
102 assert(S < E && "Cannot create empty or backwards segment");
105 /// Return true if the index is covered by this segment.
106 bool contains(SlotIndex I) const {
107 return start <= I && I < end;
110 /// Return true if the given interval, [S, E), is covered by this segment.
111 bool containsInterval(SlotIndex S, SlotIndex E) const {
112 assert((S < E) && "Backwards interval?");
113 return (start <= S && S < end) && (start < E && E <= end);
116 bool operator<(const Segment &Other) const {
117 return start < Other.start || (start == Other.start && end < Other.end);
119 bool operator==(const Segment &Other) const {
120 return start == Other.start && end == Other.end;
126 typedef SmallVector<Segment,4> Segments;
127 typedef SmallVector<VNInfo*,4> VNInfoList;
129 Segments segments; // the liveness segments
130 VNInfoList valnos; // value#'s
132 typedef Segments::iterator iterator;
133 iterator begin() { return segments.begin(); }
134 iterator end() { return segments.end(); }
136 typedef Segments::const_iterator const_iterator;
137 const_iterator begin() const { return segments.begin(); }
138 const_iterator end() const { return segments.end(); }
140 typedef VNInfoList::iterator vni_iterator;
141 vni_iterator vni_begin() { return valnos.begin(); }
142 vni_iterator vni_end() { return valnos.end(); }
144 typedef VNInfoList::const_iterator const_vni_iterator;
145 const_vni_iterator vni_begin() const { return valnos.begin(); }
146 const_vni_iterator vni_end() const { return valnos.end(); }
148 /// advanceTo - Advance the specified iterator to point to the Segment
149 /// containing the specified position, or end() if the position is past the
150 /// end of the range. If no Segment contains this position, but the
151 /// position is in a hole, this method returns an iterator pointing to the
152 /// Segment immediately after the hole.
153 iterator advanceTo(iterator I, SlotIndex Pos) {
155 if (Pos >= endIndex())
157 while (I->end <= Pos) ++I;
161 /// find - Return an iterator pointing to the first segment that ends after
162 /// Pos, or end(). This is the same as advanceTo(begin(), Pos), but faster
163 /// when searching large ranges.
165 /// If Pos is contained in a Segment, that segment is returned.
166 /// If Pos is in a hole, the following Segment is returned.
167 /// If Pos is beyond endIndex, end() is returned.
168 iterator find(SlotIndex Pos);
170 const_iterator find(SlotIndex Pos) const {
171 return const_cast<LiveRange*>(this)->find(Pos);
179 size_t size() const {
180 return segments.size();
183 bool hasAtLeastOneValue() const { return !valnos.empty(); }
185 bool containsOneValue() const { return valnos.size() == 1; }
187 unsigned getNumValNums() const { return (unsigned)valnos.size(); }
189 /// getValNumInfo - Returns pointer to the specified val#.
191 inline VNInfo *getValNumInfo(unsigned ValNo) {
192 return valnos[ValNo];
194 inline const VNInfo *getValNumInfo(unsigned ValNo) const {
195 return valnos[ValNo];
198 /// containsValue - Returns true if VNI belongs to this range.
199 bool containsValue(const VNInfo *VNI) const {
200 return VNI && VNI->id < getNumValNums() && VNI == getValNumInfo(VNI->id);
203 /// getNextValue - Create a new value number and return it. MIIdx specifies
204 /// the instruction that defines the value number.
205 VNInfo *getNextValue(SlotIndex def, VNInfo::Allocator &VNInfoAllocator) {
207 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), def);
208 valnos.push_back(VNI);
212 /// createDeadDef - Make sure the range has a value defined at Def.
213 /// If one already exists, return it. Otherwise allocate a new value and
214 /// add liveness for a dead def.
215 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator);
217 /// Create a copy of the given value. The new value will be identical except
218 /// for the Value number.
219 VNInfo *createValueCopy(const VNInfo *orig,
220 VNInfo::Allocator &VNInfoAllocator) {
222 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), *orig);
223 valnos.push_back(VNI);
227 /// RenumberValues - Renumber all values in order of appearance and remove
229 void RenumberValues();
231 /// MergeValueNumberInto - This method is called when two value numbers
232 /// are found to be equivalent. This eliminates V1, replacing all
233 /// segments with the V1 value number with the V2 value number. This can
234 /// cause merging of V1/V2 values numbers and compaction of the value space.
235 VNInfo* MergeValueNumberInto(VNInfo *V1, VNInfo *V2);
237 /// Merge all of the live segments of a specific val# in RHS into this live
238 /// range as the specified value number. The segments in RHS are allowed
239 /// to overlap with segments in the current range, it will replace the
240 /// value numbers of the overlaped live segments with the specified value
242 void MergeSegmentsInAsValue(const LiveRange &RHS, VNInfo *LHSValNo);
244 /// MergeValueInAsValue - Merge all of the segments of a specific val#
245 /// in RHS into this live range as the specified value number.
246 /// The segments in RHS are allowed to overlap with segments in the
247 /// current range, but only if the overlapping segments have the
248 /// specified value number.
249 void MergeValueInAsValue(const LiveRange &RHS,
250 const VNInfo *RHSValNo, VNInfo *LHSValNo);
252 bool empty() const { return segments.empty(); }
254 /// beginIndex - Return the lowest numbered slot covered.
255 SlotIndex beginIndex() const {
256 assert(!empty() && "Call to beginIndex() on empty range.");
257 return segments.front().start;
260 /// endNumber - return the maximum point of the range of the whole,
262 SlotIndex endIndex() const {
263 assert(!empty() && "Call to endIndex() on empty range.");
264 return segments.back().end;
267 bool expiredAt(SlotIndex index) const {
268 return index >= endIndex();
271 bool liveAt(SlotIndex index) const {
272 const_iterator r = find(index);
273 return r != end() && r->start <= index;
276 /// Return the segment that contains the specified index, or null if there
278 const Segment *getSegmentContaining(SlotIndex Idx) const {
279 const_iterator I = FindSegmentContaining(Idx);
280 return I == end() ? 0 : &*I;
283 /// Return the live segment that contains the specified index, or null if
285 Segment *getSegmentContaining(SlotIndex Idx) {
286 iterator I = FindSegmentContaining(Idx);
287 return I == end() ? 0 : &*I;
290 /// getVNInfoAt - Return the VNInfo that is live at Idx, or NULL.
291 VNInfo *getVNInfoAt(SlotIndex Idx) const {
292 const_iterator I = FindSegmentContaining(Idx);
293 return I == end() ? 0 : I->valno;
296 /// getVNInfoBefore - Return the VNInfo that is live up to but not
297 /// necessarilly including Idx, or NULL. Use this to find the reaching def
298 /// used by an instruction at this SlotIndex position.
299 VNInfo *getVNInfoBefore(SlotIndex Idx) const {
300 const_iterator I = FindSegmentContaining(Idx.getPrevSlot());
301 return I == end() ? 0 : I->valno;
304 /// Return an iterator to the segment that contains the specified index, or
305 /// end() if there is none.
306 iterator FindSegmentContaining(SlotIndex Idx) {
307 iterator I = find(Idx);
308 return I != end() && I->start <= Idx ? I : end();
311 const_iterator FindSegmentContaining(SlotIndex Idx) const {
312 const_iterator I = find(Idx);
313 return I != end() && I->start <= Idx ? I : end();
316 /// overlaps - Return true if the intersection of the two live ranges is
318 bool overlaps(const LiveRange &other) const {
321 return overlapsFrom(other, other.begin());
324 /// overlaps - Return true if the two ranges have overlapping segments
325 /// that are not coalescable according to CP.
327 /// Overlapping segments where one range is defined by a coalescable
328 /// copy are allowed.
329 bool overlaps(const LiveRange &Other, const CoalescerPair &CP,
330 const SlotIndexes&) const;
332 /// overlaps - Return true if the live range overlaps an interval specified
334 bool overlaps(SlotIndex Start, SlotIndex End) const;
336 /// overlapsFrom - Return true if the intersection of the two live ranges
337 /// is not empty. The specified iterator is a hint that we can begin
338 /// scanning the Other range starting at I.
339 bool overlapsFrom(const LiveRange &Other, const_iterator I) const;
341 /// Add the specified Segment to this range, merging segments as
342 /// appropriate. This returns an iterator to the inserted segment (which
343 /// may have grown since it was inserted).
344 iterator addSegment(Segment S) {
345 return addSegmentFrom(S, segments.begin());
348 /// extendInBlock - If this range is live before Kill in the basic block
349 /// that starts at StartIdx, extend it to be live up to Kill, and return
350 /// the value. If there is no segment before Kill, return NULL.
351 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Kill);
353 /// join - Join two live ranges (this, and other) together. This applies
354 /// mappings to the value numbers in the LHS/RHS ranges as specified. If
355 /// the ranges are not joinable, this aborts.
356 void join(LiveRange &Other,
357 const int *ValNoAssignments,
358 const int *RHSValNoAssignments,
359 SmallVectorImpl<VNInfo *> &NewVNInfo);
361 /// True iff this segment is a single segment that lies between the
362 /// specified boundaries, exclusively. Vregs live across a backedge are not
363 /// considered local. The boundaries are expected to lie within an extended
364 /// basic block, so vregs that are not live out should contain no holes.
365 bool isLocal(SlotIndex Start, SlotIndex End) const {
366 return beginIndex() > Start.getBaseIndex() &&
367 endIndex() < End.getBoundaryIndex();
370 /// Remove the specified segment from this range. Note that the segment
371 /// must be a single Segment in its entirety.
372 void removeSegment(SlotIndex Start, SlotIndex End,
373 bool RemoveDeadValNo = false);
375 void removeSegment(Segment S, bool RemoveDeadValNo = false) {
376 removeSegment(S.start, S.end, RemoveDeadValNo);
379 /// removeValNo - Remove all the segments defined by the specified value#.
380 /// Also remove the value# from value# list.
381 void removeValNo(VNInfo *ValNo);
383 /// Returns true if the live range is zero length, i.e. no live segments
384 /// span instructions. It doesn't pay to spill such a range.
385 bool isZeroLength(SlotIndexes *Indexes) const {
386 for (const_iterator i = begin(), e = end(); i != e; ++i)
387 if (Indexes->getNextNonNullIndex(i->start).getBaseIndex() <
388 i->end.getBaseIndex())
393 bool operator<(const LiveRange& other) const {
394 const SlotIndex &thisIndex = beginIndex();
395 const SlotIndex &otherIndex = other.beginIndex();
396 return thisIndex < otherIndex;
399 void print(raw_ostream &OS) const;
402 /// \brief Walk the range and assert if any invariants fail to hold.
404 /// Note that this is a no-op when asserts are disabled.
406 void verify() const {}
413 iterator addSegmentFrom(Segment S, iterator From);
414 void extendSegmentEndTo(iterator I, SlotIndex NewEnd);
415 iterator extendSegmentStartTo(iterator I, SlotIndex NewStr);
416 void markValNoForDeletion(VNInfo *V);
420 inline raw_ostream &operator<<(raw_ostream &OS, const LiveRange &LR) {
425 /// LiveInterval - This class represents the liveness of a register,
427 class LiveInterval : public LiveRange {
429 const unsigned reg; // the register or stack slot of this interval.
430 float weight; // weight of this interval
432 LiveInterval(unsigned Reg, float Weight)
433 : reg(Reg), weight(Weight) {}
435 /// getSize - Returns the sum of sizes of all the LiveRange's.
437 unsigned getSize() const;
439 /// isSpillable - Can this interval be spilled?
440 bool isSpillable() const {
441 return weight != HUGE_VALF;
444 /// markNotSpillable - Mark interval as not spillable
445 void markNotSpillable() {
449 bool operator<(const LiveInterval& other) const {
450 const SlotIndex &thisIndex = beginIndex();
451 const SlotIndex &otherIndex = other.beginIndex();
452 return thisIndex < otherIndex ||
453 (thisIndex == otherIndex && reg < other.reg);
457 LiveInterval& operator=(const LiveInterval& rhs) LLVM_DELETED_FUNCTION;
461 inline raw_ostream &operator<<(raw_ostream &OS, const LiveInterval &LI) {
466 raw_ostream &operator<<(raw_ostream &OS, const LiveRange::Segment &S);
468 inline bool operator<(SlotIndex V, const LiveRange::Segment &S) {
472 inline bool operator<(const LiveRange::Segment &S, SlotIndex V) {
476 /// Helper class for performant LiveRange bulk updates.
478 /// Calling LiveRange::addSegment() repeatedly can be expensive on large
479 /// live ranges because segments after the insertion point may need to be
480 /// shifted. The LiveRangeUpdater class can defer the shifting when adding
481 /// many segments in order.
483 /// The LiveRange will be in an invalid state until flush() is called.
484 class LiveRangeUpdater {
487 LiveRange::iterator WriteI;
488 LiveRange::iterator ReadI;
489 SmallVector<LiveRange::Segment, 16> Spills;
493 /// Create a LiveRangeUpdater for adding segments to LR.
494 /// LR will temporarily be in an invalid state until flush() is called.
495 LiveRangeUpdater(LiveRange *lr = 0) : LR(lr) {}
497 ~LiveRangeUpdater() { flush(); }
499 /// Add a segment to LR and coalesce when possible, just like
500 /// LR.addSegment(). Segments should be added in increasing start order for
501 /// best performance.
502 void add(LiveRange::Segment);
504 void add(SlotIndex Start, SlotIndex End, VNInfo *VNI) {
505 add(LiveRange::Segment(Start, End, VNI));
508 /// Return true if the LR is currently in an invalid state, and flush()
509 /// needs to be called.
510 bool isDirty() const { return LastStart.isValid(); }
512 /// Flush the updater state to LR so it is valid and contains all added
516 /// Select a different destination live range.
517 void setDest(LiveRange *lr) {
518 if (LR != lr && isDirty())
523 /// Get the current destination live range.
524 LiveRange *getDest() const { return LR; }
527 void print(raw_ostream&) const;
530 inline raw_ostream &operator<<(raw_ostream &OS, const LiveRangeUpdater &X) {
535 /// LiveRangeQuery - Query information about a live range around a given
536 /// instruction. This class hides the implementation details of live ranges,
537 /// and it should be used as the primary interface for examining live ranges
538 /// around instructions.
540 class LiveRangeQuery {
546 void init(const LiveRange &LR, SlotIndex Idx) {
550 /// Create a LiveRangeQuery for the given live range and instruction index.
551 /// The sub-instruction slot of Idx doesn't matter, only the instruction it
552 /// refers to is considered.
553 LiveRangeQuery(const LiveRange &LR, SlotIndex Idx)
554 : EarlyVal(0), LateVal(0), Kill(false) {
555 // Find the segment that enters the instruction.
556 LiveRange::const_iterator I = LR.find(Idx.getBaseIndex());
557 LiveRange::const_iterator E = LR.end();
560 // Is this an instruction live-in segment?
561 // If Idx is the start index of a basic block, include live-in segments
562 // that start at Idx.getBaseIndex().
563 if (I->start <= Idx.getBaseIndex()) {
566 // Move to the potentially live-out segment.
567 if (SlotIndex::isSameInstr(Idx, I->end)) {
572 // Special case: A PHIDef value can have its def in the middle of a
573 // segment if the value happens to be live out of the layout
575 // Such a value is not live-in.
576 if (EarlyVal->def == Idx.getBaseIndex())
579 // I now points to the segment that may be live-through, or defined by
580 // this instr. Ignore segments starting after the current instr.
581 if (SlotIndex::isEarlierInstr(Idx, I->start))
587 /// Return the value that is live-in to the instruction. This is the value
588 /// that will be read by the instruction's use operands. Return NULL if no
589 /// value is live-in.
590 VNInfo *valueIn() const {
594 /// Return true if the live-in value is killed by this instruction. This
595 /// means that either the live range ends at the instruction, or it changes
597 bool isKill() const {
601 /// Return true if this instruction has a dead def.
602 bool isDeadDef() const {
603 return EndPoint.isDead();
606 /// Return the value leaving the instruction, if any. This can be a
607 /// live-through value, or a live def. A dead def returns NULL.
608 VNInfo *valueOut() const {
609 return isDeadDef() ? 0 : LateVal;
612 /// Return the value defined by this instruction, if any. This includes
613 /// dead defs, it is the value created by the instruction's def operands.
614 VNInfo *valueDefined() const {
615 return EarlyVal == LateVal ? 0 : LateVal;
618 /// Return the end point of the last live range segment to interact with
619 /// the instruction, if any.
621 /// The end point is an invalid SlotIndex only if the live range doesn't
622 /// intersect the instruction at all.
624 /// The end point may be at or past the end of the instruction's basic
625 /// block. That means the value was live out of the block.
626 SlotIndex endPoint() const {
631 /// ConnectedVNInfoEqClasses - Helper class that can divide VNInfos in a
632 /// LiveInterval into equivalence clases of connected components. A
633 /// LiveInterval that has multiple connected components can be broken into
634 /// multiple LiveIntervals.
636 /// Given a LiveInterval that may have multiple connected components, run:
638 /// unsigned numComps = ConEQ.Classify(LI);
639 /// if (numComps > 1) {
640 /// // allocate numComps-1 new LiveIntervals into LIS[1..]
641 /// ConEQ.Distribute(LIS);
644 class ConnectedVNInfoEqClasses {
646 IntEqClasses EqClass;
648 // Note that values a and b are connected.
649 void Connect(unsigned a, unsigned b);
654 explicit ConnectedVNInfoEqClasses(LiveIntervals &lis) : LIS(lis) {}
656 /// Classify - Classify the values in LI into connected components.
657 /// Return the number of connected components.
658 unsigned Classify(const LiveInterval *LI);
660 /// getEqClass - Classify creates equivalence classes numbered 0..N. Return
661 /// the equivalence class assigned the VNI.
662 unsigned getEqClass(const VNInfo *VNI) const { return EqClass[VNI->id]; }
664 /// Distribute - Distribute values in LIV[0] into a separate LiveInterval
665 /// for each connected component. LIV must have a LiveInterval for each
666 /// connected component. The LiveIntervals in Liv[1..] must be empty.
667 /// Instructions using LIV[0] are rewritten.
668 void Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI);