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 interval 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 intervals can have holes,
15 // i.e. an interval might look like [1,20), [50,65), [1000,1001). Each
16 // individual range is represented as an instance of LiveRange, and the whole
17 // interval is represented as an instance of LiveInterval.
19 //===----------------------------------------------------------------------===//
21 #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;
39 /// VNInfo - Value Number Information.
40 /// This class holds information about a machine level values, including
41 /// definition and use points.
45 typedef BumpPtrAllocator Allocator;
47 /// The ID number of this value.
50 /// The index of the defining instruction.
53 /// VNInfo constructor.
54 VNInfo(unsigned i, SlotIndex d)
58 /// VNInfo construtor, copies values from orig, except for the value number.
59 VNInfo(unsigned i, const VNInfo &orig)
60 : id(i), def(orig.def)
63 /// Copy from the parameter into this VNInfo.
64 void copyFrom(VNInfo &src) {
68 /// Returns true if this value is defined by a PHI instruction (or was,
69 /// PHI instrucions may have been eliminated).
70 /// PHI-defs begin at a block boundary, all other defs begin at register or
72 bool isPHIDef() const { return def.isBlock(); }
74 /// Returns true if this value is unused.
75 bool isUnused() const { return !def.isValid(); }
77 /// Mark this value as unused.
78 void markUnused() { def = SlotIndex(); }
81 /// LiveRange structure - This represents a simple register range in the
82 /// program, with an inclusive start point and an exclusive end point.
83 /// These ranges are rendered as [start,end).
85 SlotIndex start; // Start point of the interval (inclusive)
86 SlotIndex end; // End point of the interval (exclusive)
87 VNInfo *valno; // identifier for the value contained in this interval.
89 LiveRange() : valno(0) {}
91 LiveRange(SlotIndex S, SlotIndex E, VNInfo *V)
92 : start(S), end(E), valno(V) {
93 assert(S < E && "Cannot create empty or backwards range");
96 /// contains - Return true if the index is covered by this range.
98 bool contains(SlotIndex I) const {
99 return start <= I && I < end;
102 /// containsRange - Return true if the given range, [S, E), is covered by
104 bool containsRange(SlotIndex S, SlotIndex E) const {
105 assert((S < E) && "Backwards interval?");
106 return (start <= S && S < end) && (start < E && E <= end);
109 bool operator<(const LiveRange &LR) const {
110 return start < LR.start || (start == LR.start && end < LR.end);
112 bool operator==(const LiveRange &LR) const {
113 return start == LR.start && end == LR.end;
117 void print(raw_ostream &os) const;
120 template <> struct isPodLike<LiveRange> { static const bool value = true; };
122 raw_ostream& operator<<(raw_ostream& os, const LiveRange &LR);
125 inline bool operator<(SlotIndex V, const LiveRange &LR) {
129 inline bool operator<(const LiveRange &LR, SlotIndex V) {
133 /// LiveInterval - This class represents some number of live ranges for a
134 /// register or value. This class also contains a bit of register allocator
139 typedef SmallVector<LiveRange,4> Ranges;
140 typedef SmallVector<VNInfo*,4> VNInfoList;
142 const unsigned reg; // the register or stack slot of this interval.
143 float weight; // weight of this interval
144 Ranges ranges; // the ranges in which this register is live
145 VNInfoList valnos; // value#'s
147 LiveInterval(unsigned Reg, float Weight)
148 : reg(Reg), weight(Weight) {}
150 typedef Ranges::iterator iterator;
151 iterator begin() { return ranges.begin(); }
152 iterator end() { return ranges.end(); }
154 typedef Ranges::const_iterator const_iterator;
155 const_iterator begin() const { return ranges.begin(); }
156 const_iterator end() const { return ranges.end(); }
158 typedef VNInfoList::iterator vni_iterator;
159 vni_iterator vni_begin() { return valnos.begin(); }
160 vni_iterator vni_end() { return valnos.end(); }
162 typedef VNInfoList::const_iterator const_vni_iterator;
163 const_vni_iterator vni_begin() const { return valnos.begin(); }
164 const_vni_iterator vni_end() const { return valnos.end(); }
166 /// advanceTo - Advance the specified iterator to point to the LiveRange
167 /// containing the specified position, or end() if the position is past the
168 /// end of the interval. If no LiveRange contains this position, but the
169 /// position is in a hole, this method returns an iterator pointing to the
170 /// LiveRange immediately after the hole.
171 iterator advanceTo(iterator I, SlotIndex Pos) {
173 if (Pos >= endIndex())
175 while (I->end <= Pos) ++I;
179 /// find - Return an iterator pointing to the first range that ends after
180 /// Pos, or end(). This is the same as advanceTo(begin(), Pos), but faster
181 /// when searching large intervals.
183 /// If Pos is contained in a LiveRange, that range is returned.
184 /// If Pos is in a hole, the following LiveRange is returned.
185 /// If Pos is beyond endIndex, end() is returned.
186 iterator find(SlotIndex Pos);
188 const_iterator find(SlotIndex Pos) const {
189 return const_cast<LiveInterval*>(this)->find(Pos);
197 bool hasAtLeastOneValue() const { return !valnos.empty(); }
199 bool containsOneValue() const { return valnos.size() == 1; }
201 unsigned getNumValNums() const { return (unsigned)valnos.size(); }
203 /// getValNumInfo - Returns pointer to the specified val#.
205 inline VNInfo *getValNumInfo(unsigned ValNo) {
206 return valnos[ValNo];
208 inline const VNInfo *getValNumInfo(unsigned ValNo) const {
209 return valnos[ValNo];
212 /// containsValue - Returns true if VNI belongs to this interval.
213 bool containsValue(const VNInfo *VNI) const {
214 return VNI && VNI->id < getNumValNums() && VNI == getValNumInfo(VNI->id);
217 /// getNextValue - Create a new value number and return it. MIIdx specifies
218 /// the instruction that defines the value number.
219 VNInfo *getNextValue(SlotIndex def, VNInfo::Allocator &VNInfoAllocator) {
221 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), def);
222 valnos.push_back(VNI);
226 /// createDeadDef - Make sure the interval has a value defined at Def.
227 /// If one already exists, return it. Otherwise allocate a new value and
228 /// add liveness for a dead def.
229 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator);
231 /// Create a copy of the given value. The new value will be identical except
232 /// for the Value number.
233 VNInfo *createValueCopy(const VNInfo *orig,
234 VNInfo::Allocator &VNInfoAllocator) {
236 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), *orig);
237 valnos.push_back(VNI);
241 /// RenumberValues - Renumber all values in order of appearance and remove
243 void RenumberValues();
245 /// MergeValueNumberInto - This method is called when two value numbers
246 /// are found to be equivalent. This eliminates V1, replacing all
247 /// LiveRanges with the V1 value number with the V2 value number. This can
248 /// cause merging of V1/V2 values numbers and compaction of the value space.
249 VNInfo* MergeValueNumberInto(VNInfo *V1, VNInfo *V2);
251 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
252 /// in RHS into this live interval as the specified value number.
253 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
254 /// current interval, it will replace the value numbers of the overlaped
255 /// live ranges with the specified value number.
256 void MergeRangesInAsValue(const LiveInterval &RHS, VNInfo *LHSValNo);
258 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
259 /// in RHS into this live interval as the specified value number.
260 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
261 /// current interval, but only if the overlapping LiveRanges have the
262 /// specified value number.
263 void MergeValueInAsValue(const LiveInterval &RHS,
264 const VNInfo *RHSValNo, VNInfo *LHSValNo);
266 bool empty() const { return ranges.empty(); }
268 /// beginIndex - Return the lowest numbered slot covered by interval.
269 SlotIndex beginIndex() const {
270 assert(!empty() && "Call to beginIndex() on empty interval.");
271 return ranges.front().start;
274 /// endNumber - return the maximum point of the interval of the whole,
276 SlotIndex endIndex() const {
277 assert(!empty() && "Call to endIndex() on empty interval.");
278 return ranges.back().end;
281 bool expiredAt(SlotIndex index) const {
282 return index >= endIndex();
285 bool liveAt(SlotIndex index) const {
286 const_iterator r = find(index);
287 return r != end() && r->start <= index;
290 /// getLiveRangeContaining - Return the live range that contains the
291 /// specified index, or null if there is none.
292 const LiveRange *getLiveRangeContaining(SlotIndex Idx) const {
293 const_iterator I = FindLiveRangeContaining(Idx);
294 return I == end() ? 0 : &*I;
297 /// getLiveRangeContaining - Return the live range that contains the
298 /// specified index, or null if there is none.
299 LiveRange *getLiveRangeContaining(SlotIndex Idx) {
300 iterator I = FindLiveRangeContaining(Idx);
301 return I == end() ? 0 : &*I;
304 /// getVNInfoAt - Return the VNInfo that is live at Idx, or NULL.
305 VNInfo *getVNInfoAt(SlotIndex Idx) const {
306 const_iterator I = FindLiveRangeContaining(Idx);
307 return I == end() ? 0 : I->valno;
310 /// getVNInfoBefore - Return the VNInfo that is live up to but not
311 /// necessarilly including Idx, or NULL. Use this to find the reaching def
312 /// used by an instruction at this SlotIndex position.
313 VNInfo *getVNInfoBefore(SlotIndex Idx) const {
314 const_iterator I = FindLiveRangeContaining(Idx.getPrevSlot());
315 return I == end() ? 0 : I->valno;
318 /// FindLiveRangeContaining - Return an iterator to the live range that
319 /// contains the specified index, or end() if there is none.
320 iterator FindLiveRangeContaining(SlotIndex Idx) {
321 iterator I = find(Idx);
322 return I != end() && I->start <= Idx ? I : end();
325 const_iterator FindLiveRangeContaining(SlotIndex Idx) const {
326 const_iterator I = find(Idx);
327 return I != end() && I->start <= Idx ? I : end();
330 /// overlaps - Return true if the intersection of the two live intervals is
332 bool overlaps(const LiveInterval& other) const {
335 return overlapsFrom(other, other.begin());
338 /// overlaps - Return true if the two intervals have overlapping segments
339 /// that are not coalescable according to CP.
341 /// Overlapping segments where one interval is defined by a coalescable
342 /// copy are allowed.
343 bool overlaps(const LiveInterval &Other, const CoalescerPair &CP,
344 const SlotIndexes&) const;
346 /// overlaps - Return true if the live interval overlaps a range specified
348 bool overlaps(SlotIndex Start, SlotIndex End) const;
350 /// overlapsFrom - Return true if the intersection of the two live intervals
351 /// is not empty. The specified iterator is a hint that we can begin
352 /// scanning the Other interval starting at I.
353 bool overlapsFrom(const LiveInterval& other, const_iterator I) const;
355 /// addRange - Add the specified LiveRange to this interval, merging
356 /// intervals as appropriate. This returns an iterator to the inserted live
357 /// range (which may have grown since it was inserted.
358 iterator addRange(LiveRange LR) {
359 return addRangeFrom(LR, ranges.begin());
362 /// extendInBlock - If this interval is live before Kill in the basic block
363 /// that starts at StartIdx, extend it to be live up to Kill, and return
364 /// the value. If there is no live range before Kill, return NULL.
365 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Kill);
367 /// join - Join two live intervals (this, and other) together. This applies
368 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
369 /// the intervals are not joinable, this aborts.
370 void join(LiveInterval &Other,
371 const int *ValNoAssignments,
372 const int *RHSValNoAssignments,
373 SmallVectorImpl<VNInfo *> &NewVNInfo);
375 /// True iff this live range is a single segment that lies between the
376 /// specified boundaries, exclusively. Vregs live across a backedge are not
377 /// considered local. The boundaries are expected to lie within an extended
378 /// basic block, so vregs that are not live out should contain no holes.
379 bool isLocal(SlotIndex Start, SlotIndex End) const {
380 return beginIndex() > Start.getBaseIndex() &&
381 endIndex() < End.getBoundaryIndex();
384 /// removeRange - Remove the specified range from this interval. Note that
385 /// the range must be a single LiveRange in its entirety.
386 void removeRange(SlotIndex Start, SlotIndex End,
387 bool RemoveDeadValNo = false);
389 void removeRange(LiveRange LR, bool RemoveDeadValNo = false) {
390 removeRange(LR.start, LR.end, RemoveDeadValNo);
393 /// removeValNo - Remove all the ranges defined by the specified value#.
394 /// Also remove the value# from value# list.
395 void removeValNo(VNInfo *ValNo);
397 /// getSize - Returns the sum of sizes of all the LiveRange's.
399 unsigned getSize() const;
401 /// Returns true if the live interval is zero length, i.e. no live ranges
402 /// span instructions. It doesn't pay to spill such an interval.
403 bool isZeroLength(SlotIndexes *Indexes) const {
404 for (const_iterator i = begin(), e = end(); i != e; ++i)
405 if (Indexes->getNextNonNullIndex(i->start).getBaseIndex() <
406 i->end.getBaseIndex())
411 /// isSpillable - Can this interval be spilled?
412 bool isSpillable() const {
413 return weight != HUGE_VALF;
416 /// markNotSpillable - Mark interval as not spillable
417 void markNotSpillable() {
421 bool operator<(const LiveInterval& other) const {
422 const SlotIndex &thisIndex = beginIndex();
423 const SlotIndex &otherIndex = other.beginIndex();
424 return (thisIndex < otherIndex ||
425 (thisIndex == otherIndex && reg < other.reg));
428 void print(raw_ostream &OS) const;
431 /// \brief Walk the interval and assert if any invariants fail to hold.
433 /// Note that this is a no-op when asserts are disabled.
435 void verify() const {}
442 Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From);
443 void extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd);
444 Ranges::iterator extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStr);
445 void markValNoForDeletion(VNInfo *V);
447 LiveInterval& operator=(const LiveInterval& rhs) LLVM_DELETED_FUNCTION;
451 inline raw_ostream &operator<<(raw_ostream &OS, const LiveInterval &LI) {
456 /// Helper class for performant LiveInterval bulk updates.
458 /// Calling LiveInterval::addRange() repeatedly can be expensive on large
459 /// live ranges because segments after the insertion point may need to be
460 /// shifted. The LiveRangeUpdater class can defer the shifting when adding
461 /// many segments in order.
463 /// The LiveInterval will be in an invalid state until flush() is called.
464 class LiveRangeUpdater {
467 LiveInterval::iterator WriteI;
468 LiveInterval::iterator ReadI;
469 SmallVector<LiveRange, 16> Spills;
473 /// Create a LiveRangeUpdater for adding segments to LI.
474 /// LI will temporarily be in an invalid state until flush() is called.
475 LiveRangeUpdater(LiveInterval *li = 0) : LI(li) {}
477 ~LiveRangeUpdater() { flush(); }
479 /// Add a segment to LI and coalesce when possible, just like LI.addRange().
480 /// Segments should be added in increasing start order for best performance.
483 void add(SlotIndex Start, SlotIndex End, VNInfo *VNI) {
484 add(LiveRange(Start, End, VNI));
487 /// Return true if the LI is currently in an invalid state, and flush()
488 /// needs to be called.
489 bool isDirty() const { return LastStart.isValid(); }
491 /// Flush the updater state to LI so it is valid and contains all added
495 /// Select a different destination live range.
496 void setDest(LiveInterval *li) {
497 if (LI != li && isDirty())
502 /// Get the current destination live range.
503 LiveInterval *getDest() const { return LI; }
506 void print(raw_ostream&) const;
509 inline raw_ostream &operator<<(raw_ostream &OS, const LiveRangeUpdater &X) {
514 /// LiveRangeQuery - Query information about a live range around a given
515 /// instruction. This class hides the implementation details of live ranges,
516 /// and it should be used as the primary interface for examining live ranges
517 /// around instructions.
519 class LiveRangeQuery {
526 /// Create a LiveRangeQuery for the given live range and instruction index.
527 /// The sub-instruction slot of Idx doesn't matter, only the instruction it
528 /// refers to is considered.
529 LiveRangeQuery(const LiveInterval &LI, SlotIndex Idx)
530 : EarlyVal(0), LateVal(0), Kill(false) {
531 // Find the segment that enters the instruction.
532 LiveInterval::const_iterator I = LI.find(Idx.getBaseIndex());
533 LiveInterval::const_iterator E = LI.end();
536 // Is this an instruction live-in segment?
537 // If Idx is the start index of a basic block, include live-in segments
538 // that start at Idx.getBaseIndex().
539 if (I->start <= Idx.getBaseIndex()) {
542 // Move to the potentially live-out segment.
543 if (SlotIndex::isSameInstr(Idx, I->end)) {
548 // Special case: A PHIDef value can have its def in the middle of a
549 // segment if the value happens to be live out of the layout
551 // Such a value is not live-in.
552 if (EarlyVal->def == Idx.getBaseIndex())
555 // I now points to the segment that may be live-through, or defined by
556 // this instr. Ignore segments starting after the current instr.
557 if (SlotIndex::isEarlierInstr(Idx, I->start))
563 /// Return the value that is live-in to the instruction. This is the value
564 /// that will be read by the instruction's use operands. Return NULL if no
565 /// value is live-in.
566 VNInfo *valueIn() const {
570 /// Return true if the live-in value is killed by this instruction. This
571 /// means that either the live range ends at the instruction, or it changes
573 bool isKill() const {
577 /// Return true if this instruction has a dead def.
578 bool isDeadDef() const {
579 return EndPoint.isDead();
582 /// Return the value leaving the instruction, if any. This can be a
583 /// live-through value, or a live def. A dead def returns NULL.
584 VNInfo *valueOut() const {
585 return isDeadDef() ? 0 : LateVal;
588 /// Return the value defined by this instruction, if any. This includes
589 /// dead defs, it is the value created by the instruction's def operands.
590 VNInfo *valueDefined() const {
591 return EarlyVal == LateVal ? 0 : LateVal;
594 /// Return the end point of the last live range segment to interact with
595 /// the instruction, if any.
597 /// The end point is an invalid SlotIndex only if the live range doesn't
598 /// intersect the instruction at all.
600 /// The end point may be at or past the end of the instruction's basic
601 /// block. That means the value was live out of the block.
602 SlotIndex endPoint() const {
607 /// ConnectedVNInfoEqClasses - Helper class that can divide VNInfos in a
608 /// LiveInterval into equivalence clases of connected components. A
609 /// LiveInterval that has multiple connected components can be broken into
610 /// multiple LiveIntervals.
612 /// Given a LiveInterval that may have multiple connected components, run:
614 /// unsigned numComps = ConEQ.Classify(LI);
615 /// if (numComps > 1) {
616 /// // allocate numComps-1 new LiveIntervals into LIS[1..]
617 /// ConEQ.Distribute(LIS);
620 class ConnectedVNInfoEqClasses {
622 IntEqClasses EqClass;
624 // Note that values a and b are connected.
625 void Connect(unsigned a, unsigned b);
630 explicit ConnectedVNInfoEqClasses(LiveIntervals &lis) : LIS(lis) {}
632 /// Classify - Classify the values in LI into connected components.
633 /// Return the number of connected components.
634 unsigned Classify(const LiveInterval *LI);
636 /// getEqClass - Classify creates equivalence classes numbered 0..N. Return
637 /// the equivalence class assigned the VNI.
638 unsigned getEqClass(const VNInfo *VNI) const { return EqClass[VNI->id]; }
640 /// Distribute - Distribute values in LIV[0] into a separate LiveInterval
641 /// for each connected component. LIV must have a LiveInterval for each
642 /// connected component. The LiveIntervals in Liv[1..] must be empty.
643 /// Instructions using LIV[0] are rewritten.
644 void Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI);