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
158 LiveInterval(unsigned Reg, float Weight)
159 : reg(Reg), weight(Weight) {}
161 typedef Ranges::iterator iterator;
162 iterator begin() { return ranges.begin(); }
163 iterator end() { return ranges.end(); }
165 typedef Ranges::const_iterator const_iterator;
166 const_iterator begin() const { return ranges.begin(); }
167 const_iterator end() const { return ranges.end(); }
169 typedef VNInfoList::iterator vni_iterator;
170 vni_iterator vni_begin() { return valnos.begin(); }
171 vni_iterator vni_end() { return valnos.end(); }
173 typedef VNInfoList::const_iterator const_vni_iterator;
174 const_vni_iterator vni_begin() const { return valnos.begin(); }
175 const_vni_iterator vni_end() const { return valnos.end(); }
177 /// advanceTo - Advance the specified iterator to point to the LiveRange
178 /// containing the specified position, or end() if the position is past the
179 /// end of the interval. If no LiveRange contains this position, but the
180 /// position is in a hole, this method returns an iterator pointing to the
181 /// LiveRange immediately after the hole.
182 iterator advanceTo(iterator I, SlotIndex Pos) {
184 if (Pos >= endIndex())
186 while (I->end <= Pos) ++I;
190 /// find - Return an iterator pointing to the first range that ends after
191 /// Pos, or end(). This is the same as advanceTo(begin(), Pos), but faster
192 /// when searching large intervals.
194 /// If Pos is contained in a LiveRange, that range is returned.
195 /// If Pos is in a hole, the following LiveRange is returned.
196 /// If Pos is beyond endIndex, end() is returned.
197 iterator find(SlotIndex Pos);
199 const_iterator find(SlotIndex Pos) const {
200 return const_cast<LiveInterval*>(this)->find(Pos);
208 bool hasAtLeastOneValue() const { return !valnos.empty(); }
210 bool containsOneValue() const { return valnos.size() == 1; }
212 unsigned getNumValNums() const { return (unsigned)valnos.size(); }
214 /// getValNumInfo - Returns pointer to the specified val#.
216 inline VNInfo *getValNumInfo(unsigned ValNo) {
217 return valnos[ValNo];
219 inline const VNInfo *getValNumInfo(unsigned ValNo) const {
220 return valnos[ValNo];
223 /// containsValue - Returns true if VNI belongs to this interval.
224 bool containsValue(const VNInfo *VNI) const {
225 return VNI && VNI->id < getNumValNums() && VNI == getValNumInfo(VNI->id);
228 /// getNextValue - Create a new value number and return it. MIIdx specifies
229 /// the instruction that defines the value number.
230 VNInfo *getNextValue(SlotIndex def, VNInfo::Allocator &VNInfoAllocator) {
232 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), def);
233 valnos.push_back(VNI);
237 /// createDeadDef - Make sure the interval has a value defined at Def.
238 /// If one already exists, return it. Otherwise allocate a new value and
239 /// add liveness for a dead def.
240 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator);
242 /// Create a copy of the given value. The new value will be identical except
243 /// for the Value number.
244 VNInfo *createValueCopy(const VNInfo *orig,
245 VNInfo::Allocator &VNInfoAllocator) {
247 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), *orig);
248 valnos.push_back(VNI);
252 /// RenumberValues - Renumber all values in order of appearance and remove
254 void RenumberValues(LiveIntervals &lis);
256 /// MergeValueNumberInto - This method is called when two value nubmers
257 /// are found to be equivalent. This eliminates V1, replacing all
258 /// LiveRanges with the V1 value number with the V2 value number. This can
259 /// cause merging of V1/V2 values numbers and compaction of the value space.
260 VNInfo* MergeValueNumberInto(VNInfo *V1, VNInfo *V2);
262 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
263 /// in RHS into this live interval as the specified value number.
264 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
265 /// current interval, it will replace the value numbers of the overlaped
266 /// live ranges with the specified value number.
267 void MergeRangesInAsValue(const LiveInterval &RHS, VNInfo *LHSValNo);
269 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
270 /// in RHS into this live interval as the specified value number.
271 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
272 /// current interval, but only if the overlapping LiveRanges have the
273 /// specified value number.
274 void MergeValueInAsValue(const LiveInterval &RHS,
275 const VNInfo *RHSValNo, VNInfo *LHSValNo);
277 bool empty() const { return ranges.empty(); }
279 /// beginIndex - Return the lowest numbered slot covered by interval.
280 SlotIndex beginIndex() const {
281 assert(!empty() && "Call to beginIndex() on empty interval.");
282 return ranges.front().start;
285 /// endNumber - return the maximum point of the interval of the whole,
287 SlotIndex endIndex() const {
288 assert(!empty() && "Call to endIndex() on empty interval.");
289 return ranges.back().end;
292 bool expiredAt(SlotIndex index) const {
293 return index >= endIndex();
296 bool liveAt(SlotIndex index) const {
297 const_iterator r = find(index);
298 return r != end() && r->start <= index;
301 /// killedAt - Return true if a live range ends at index. Note that the kill
302 /// point is not contained in the half-open live range. It is usually the
303 /// getDefIndex() slot following its last use.
304 bool killedAt(SlotIndex index) const {
305 const_iterator r = find(index.getRegSlot(true));
306 return r != end() && r->end == index;
309 /// getLiveRangeContaining - Return the live range that contains the
310 /// specified index, or null if there is none.
311 const LiveRange *getLiveRangeContaining(SlotIndex Idx) const {
312 const_iterator I = FindLiveRangeContaining(Idx);
313 return I == end() ? 0 : &*I;
316 /// getLiveRangeContaining - Return the live range that contains the
317 /// specified index, or null if there is none.
318 LiveRange *getLiveRangeContaining(SlotIndex Idx) {
319 iterator I = FindLiveRangeContaining(Idx);
320 return I == end() ? 0 : &*I;
323 /// getVNInfoAt - Return the VNInfo that is live at Idx, or NULL.
324 VNInfo *getVNInfoAt(SlotIndex Idx) const {
325 const_iterator I = FindLiveRangeContaining(Idx);
326 return I == end() ? 0 : I->valno;
329 /// getVNInfoBefore - Return the VNInfo that is live up to but not
330 /// necessarilly including Idx, or NULL. Use this to find the reaching def
331 /// used by an instruction at this SlotIndex position.
332 VNInfo *getVNInfoBefore(SlotIndex Idx) const {
333 const_iterator I = FindLiveRangeContaining(Idx.getPrevSlot());
334 return I == end() ? 0 : I->valno;
337 /// FindLiveRangeContaining - Return an iterator to the live range that
338 /// contains the specified index, or end() if there is none.
339 iterator FindLiveRangeContaining(SlotIndex Idx) {
340 iterator I = find(Idx);
341 return I != end() && I->start <= Idx ? I : end();
344 const_iterator FindLiveRangeContaining(SlotIndex Idx) const {
345 const_iterator I = find(Idx);
346 return I != end() && I->start <= Idx ? I : end();
349 /// overlaps - Return true if the intersection of the two live intervals is
351 bool overlaps(const LiveInterval& other) const {
354 return overlapsFrom(other, other.begin());
357 /// overlaps - Return true if the two intervals have overlapping segments
358 /// that are not coalescable according to CP.
360 /// Overlapping segments where one interval is defined by a coalescable
361 /// copy are allowed.
362 bool overlaps(const LiveInterval &Other, const CoalescerPair &CP,
363 const SlotIndexes&) const;
365 /// overlaps - Return true if the live interval overlaps a range specified
367 bool overlaps(SlotIndex Start, SlotIndex End) const;
369 /// overlapsFrom - Return true if the intersection of the two live intervals
370 /// is not empty. The specified iterator is a hint that we can begin
371 /// scanning the Other interval starting at I.
372 bool overlapsFrom(const LiveInterval& other, const_iterator I) const;
374 /// addRange - Add the specified LiveRange to this interval, merging
375 /// intervals as appropriate. This returns an iterator to the inserted live
376 /// range (which may have grown since it was inserted.
377 iterator addRange(LiveRange LR) {
378 return addRangeFrom(LR, ranges.begin());
381 /// extendInBlock - If this interval is live before Kill in the basic block
382 /// that starts at StartIdx, extend it to be live up to Kill, and return
383 /// the value. If there is no live range before Kill, return NULL.
384 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Kill);
386 /// join - Join two live intervals (this, and other) together. This applies
387 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
388 /// the intervals are not joinable, this aborts.
389 void join(LiveInterval &Other,
390 const int *ValNoAssignments,
391 const int *RHSValNoAssignments,
392 SmallVector<VNInfo*, 16> &NewVNInfo,
393 MachineRegisterInfo *MRI);
395 /// isInOneLiveRange - Return true if the range specified is entirely in the
396 /// a single LiveRange of the live interval.
397 bool isInOneLiveRange(SlotIndex Start, SlotIndex End) const {
398 const_iterator r = find(Start);
399 return r != end() && r->containsRange(Start, End);
402 /// True iff this live range is a single segment that lies between the
403 /// specified boundaries, exclusively. Vregs live across a backedge are not
404 /// considered local. The boundaries are expected to lie within an extended
405 /// basic block, so vregs that are not live out should contain no holes.
406 bool isLocal(SlotIndex Start, SlotIndex End) const {
407 return beginIndex() > Start.getBaseIndex() &&
408 endIndex() < End.getBoundaryIndex();
411 /// removeRange - Remove the specified range from this interval. Note that
412 /// the range must be a single LiveRange in its entirety.
413 void removeRange(SlotIndex Start, SlotIndex End,
414 bool RemoveDeadValNo = false);
416 void removeRange(LiveRange LR, bool RemoveDeadValNo = false) {
417 removeRange(LR.start, LR.end, RemoveDeadValNo);
420 /// removeValNo - Remove all the ranges defined by the specified value#.
421 /// Also remove the value# from value# list.
422 void removeValNo(VNInfo *ValNo);
424 /// getSize - Returns the sum of sizes of all the LiveRange's.
426 unsigned getSize() const;
428 /// Returns true if the live interval is zero length, i.e. no live ranges
429 /// span instructions. It doesn't pay to spill such an interval.
430 bool isZeroLength(SlotIndexes *Indexes) const {
431 for (const_iterator i = begin(), e = end(); i != e; ++i)
432 if (Indexes->getNextNonNullIndex(i->start).getBaseIndex() <
433 i->end.getBaseIndex())
438 /// isSpillable - Can this interval be spilled?
439 bool isSpillable() const {
440 return weight != HUGE_VALF;
443 /// markNotSpillable - Mark interval as not spillable
444 void markNotSpillable() {
448 bool operator<(const LiveInterval& other) const {
449 const SlotIndex &thisIndex = beginIndex();
450 const SlotIndex &otherIndex = other.beginIndex();
451 return (thisIndex < otherIndex ||
452 (thisIndex == otherIndex && reg < other.reg));
455 void print(raw_ostream &OS) const;
458 /// \brief Walk the interval and assert if any invariants fail to hold.
460 /// Note that this is a no-op when asserts are disabled.
462 void verify() const {}
469 Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From);
470 void extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd);
471 Ranges::iterator extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStr);
472 void markValNoForDeletion(VNInfo *V);
474 LiveInterval& operator=(const LiveInterval& rhs) LLVM_DELETED_FUNCTION;
478 inline raw_ostream &operator<<(raw_ostream &OS, const LiveInterval &LI) {
483 /// Helper class for performant LiveInterval bulk updates.
485 /// Calling LiveInterval::addRange() repeatedly can be expensive on large
486 /// live ranges because segments after the insertion point may need to be
487 /// shifted. The LiveRangeUpdater class can defer the shifting when adding
488 /// many segments in order.
490 /// The LiveInterval will be in an invalid state until flush() is called.
491 class LiveRangeUpdater {
494 LiveInterval::iterator WriteI;
495 LiveInterval::iterator ReadI;
496 SmallVector<LiveRange, 16> Spills;
500 /// Create a LiveRangeUpdater for adding segments to LI.
501 /// LI will temporarily be in an invalid state until flush() is called.
502 LiveRangeUpdater(LiveInterval *li = 0) : LI(li) {}
504 ~LiveRangeUpdater() { flush(); }
506 /// Add a segment to LI and coalesce when possible, just like LI.addRange().
507 /// Segments should be added in increasing start order for best performance.
510 void add(SlotIndex Start, SlotIndex End, VNInfo *VNI) {
511 add(LiveRange(Start, End, VNI));
514 /// Return true if the LI is currently in an invalid state, and flush()
515 /// needs to be called.
516 bool isDirty() const { return LastStart.isValid(); }
518 /// Flush the updater state to LI so it is valid and contains all added
522 /// Select a different destination live range.
523 void setDest(LiveInterval *li) {
524 if (LI != li && isDirty())
529 /// Get the current destination live range.
530 LiveInterval *getDest() const { return LI; }
533 void print(raw_ostream&) const;
536 inline raw_ostream &operator<<(raw_ostream &OS, const LiveRangeUpdater &X) {
541 /// LiveRangeQuery - Query information about a live range around a given
542 /// instruction. This class hides the implementation details of live ranges,
543 /// and it should be used as the primary interface for examining live ranges
544 /// around instructions.
546 class LiveRangeQuery {
553 /// Create a LiveRangeQuery for the given live range and instruction index.
554 /// The sub-instruction slot of Idx doesn't matter, only the instruction it
555 /// refers to is considered.
556 LiveRangeQuery(const LiveInterval &LI, SlotIndex Idx)
557 : EarlyVal(0), LateVal(0), Kill(false) {
558 // Find the segment that enters the instruction.
559 LiveInterval::const_iterator I = LI.find(Idx.getBaseIndex());
560 LiveInterval::const_iterator E = LI.end();
563 // Is this an instruction live-in segment?
564 // If Idx is the start index of a basic block, include live-in segments
565 // that start at Idx.getBaseIndex().
566 if (I->start <= Idx.getBaseIndex()) {
569 // Move to the potentially live-out segment.
570 if (SlotIndex::isSameInstr(Idx, I->end)) {
575 // Special case: A PHIDef value can have its def in the middle of a
576 // segment if the value happens to be live out of the layout
578 // Such a value is not live-in.
579 if (EarlyVal->def == Idx.getBaseIndex())
582 // I now points to the segment that may be live-through, or defined by
583 // this instr. Ignore segments starting after the current instr.
584 if (SlotIndex::isEarlierInstr(Idx, I->start))
590 /// Return the value that is live-in to the instruction. This is the value
591 /// that will be read by the instruction's use operands. Return NULL if no
592 /// value is live-in.
593 VNInfo *valueIn() const {
597 /// Return true if the live-in value is killed by this instruction. This
598 /// means that either the live range ends at the instruction, or it changes
600 bool isKill() const {
604 /// Return true if this instruction has a dead def.
605 bool isDeadDef() const {
606 return EndPoint.isDead();
609 /// Return the value leaving the instruction, if any. This can be a
610 /// live-through value, or a live def. A dead def returns NULL.
611 VNInfo *valueOut() const {
612 return isDeadDef() ? 0 : LateVal;
615 /// Return the value defined by this instruction, if any. This includes
616 /// dead defs, it is the value created by the instruction's def operands.
617 VNInfo *valueDefined() const {
618 return EarlyVal == LateVal ? 0 : LateVal;
621 /// Return the end point of the last live range segment to interact with
622 /// the instruction, if any.
624 /// The end point is an invalid SlotIndex only if the live range doesn't
625 /// intersect the instruction at all.
627 /// The end point may be at or past the end of the instruction's basic
628 /// block. That means the value was live out of the block.
629 SlotIndex endPoint() const {
634 /// ConnectedVNInfoEqClasses - Helper class that can divide VNInfos in a
635 /// LiveInterval into equivalence clases of connected components. A
636 /// LiveInterval that has multiple connected components can be broken into
637 /// multiple LiveIntervals.
639 /// Given a LiveInterval that may have multiple connected components, run:
641 /// unsigned numComps = ConEQ.Classify(LI);
642 /// if (numComps > 1) {
643 /// // allocate numComps-1 new LiveIntervals into LIS[1..]
644 /// ConEQ.Distribute(LIS);
647 class ConnectedVNInfoEqClasses {
649 IntEqClasses EqClass;
651 // Note that values a and b are connected.
652 void Connect(unsigned a, unsigned b);
657 explicit ConnectedVNInfoEqClasses(LiveIntervals &lis) : LIS(lis) {}
659 /// Classify - Classify the values in LI into connected components.
660 /// Return the number of connected components.
661 unsigned Classify(const LiveInterval *LI);
663 /// getEqClass - Classify creates equivalence classes numbered 0..N. Return
664 /// the equivalence class assigned the VNI.
665 unsigned getEqClass(const VNInfo *VNI) const { return EqClass[VNI->id]; }
667 /// Distribute - Distribute values in LIV[0] into a separate LiveInterval
668 /// for each connected component. LIV must have a LiveInterval for each
669 /// connected component. The LiveIntervals in Liv[1..] must be empty.
670 /// Instructions using LIV[0] are rewritten.
671 void Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI);