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/Support/Allocator.h"
26 #include "llvm/Support/AlignOf.h"
27 #include "llvm/CodeGen/SlotIndexes.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(SlotIndex S, SlotIndex E, VNInfo *V)
90 : start(S), end(E), valno(V) {
92 assert(S < E && "Cannot create empty or backwards range");
95 /// contains - Return true if the index is covered by this range.
97 bool contains(SlotIndex I) const {
98 return start <= I && I < end;
101 /// containsRange - Return true if the given range, [S, E), is covered by
103 bool containsRange(SlotIndex S, SlotIndex E) const {
104 assert((S < E) && "Backwards interval?");
105 return (start <= S && S < end) && (start < E && E <= end);
108 bool operator<(const LiveRange &LR) const {
109 return start < LR.start || (start == LR.start && end < LR.end);
111 bool operator==(const LiveRange &LR) const {
112 return start == LR.start && end == LR.end;
116 void print(raw_ostream &os) const;
119 LiveRange(); // DO NOT IMPLEMENT
122 template <> struct isPodLike<LiveRange> { static const bool value = true; };
124 raw_ostream& operator<<(raw_ostream& os, const LiveRange &LR);
127 inline bool operator<(SlotIndex V, const LiveRange &LR) {
131 inline bool operator<(const LiveRange &LR, SlotIndex V) {
135 /// LiveInterval - This class represents some number of live ranges for a
136 /// register or value. This class also contains a bit of register allocator
141 typedef SmallVector<LiveRange,4> Ranges;
142 typedef SmallVector<VNInfo*,4> VNInfoList;
144 const unsigned reg; // the register or stack slot of this interval.
145 float weight; // weight of this interval
146 Ranges ranges; // the ranges in which this register is live
147 VNInfoList valnos; // value#'s
160 LiveInterval(unsigned Reg, float Weight)
161 : reg(Reg), weight(Weight) {}
163 typedef Ranges::iterator iterator;
164 iterator begin() { return ranges.begin(); }
165 iterator end() { return ranges.end(); }
167 typedef Ranges::const_iterator const_iterator;
168 const_iterator begin() const { return ranges.begin(); }
169 const_iterator end() const { return ranges.end(); }
171 typedef VNInfoList::iterator vni_iterator;
172 vni_iterator vni_begin() { return valnos.begin(); }
173 vni_iterator vni_end() { return valnos.end(); }
175 typedef VNInfoList::const_iterator const_vni_iterator;
176 const_vni_iterator vni_begin() const { return valnos.begin(); }
177 const_vni_iterator vni_end() const { return valnos.end(); }
179 /// advanceTo - Advance the specified iterator to point to the LiveRange
180 /// containing the specified position, or end() if the position is past the
181 /// end of the interval. If no LiveRange contains this position, but the
182 /// position is in a hole, this method returns an iterator pointing to the
183 /// LiveRange immediately after the hole.
184 iterator advanceTo(iterator I, SlotIndex Pos) {
186 if (Pos >= endIndex())
188 while (I->end <= Pos) ++I;
192 /// find - Return an iterator pointing to the first range that ends after
193 /// Pos, or end(). This is the same as advanceTo(begin(), Pos), but faster
194 /// when searching large intervals.
196 /// If Pos is contained in a LiveRange, that range is returned.
197 /// If Pos is in a hole, the following LiveRange is returned.
198 /// If Pos is beyond endIndex, end() is returned.
199 iterator find(SlotIndex Pos);
201 const_iterator find(SlotIndex Pos) const {
202 return const_cast<LiveInterval*>(this)->find(Pos);
210 bool hasAtLeastOneValue() const { return !valnos.empty(); }
212 bool containsOneValue() const { return valnos.size() == 1; }
214 unsigned getNumValNums() const { return (unsigned)valnos.size(); }
216 /// getValNumInfo - Returns pointer to the specified val#.
218 inline VNInfo *getValNumInfo(unsigned ValNo) {
219 return valnos[ValNo];
221 inline const VNInfo *getValNumInfo(unsigned ValNo) const {
222 return valnos[ValNo];
225 /// containsValue - Returns true if VNI belongs to this interval.
226 bool containsValue(const VNInfo *VNI) const {
227 return VNI && VNI->id < getNumValNums() && VNI == getValNumInfo(VNI->id);
230 /// getNextValue - Create a new value number and return it. MIIdx specifies
231 /// the instruction that defines the value number.
232 VNInfo *getNextValue(SlotIndex def, VNInfo::Allocator &VNInfoAllocator) {
234 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), def);
235 valnos.push_back(VNI);
239 /// createDeadDef - Make sure the interval has a value defined at Def.
240 /// If one already exists, return it. Otherwise allocate a new value and
241 /// add liveness for a dead def.
242 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator);
244 /// Create a copy of the given value. The new value will be identical except
245 /// for the Value number.
246 VNInfo *createValueCopy(const VNInfo *orig,
247 VNInfo::Allocator &VNInfoAllocator) {
249 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), *orig);
250 valnos.push_back(VNI);
254 /// RenumberValues - Renumber all values in order of appearance and remove
256 void RenumberValues(LiveIntervals &lis);
258 /// MergeValueNumberInto - This method is called when two value nubmers
259 /// are found to be equivalent. This eliminates V1, replacing all
260 /// LiveRanges with the V1 value number with the V2 value number. This can
261 /// cause merging of V1/V2 values numbers and compaction of the value space.
262 VNInfo* MergeValueNumberInto(VNInfo *V1, VNInfo *V2);
264 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
265 /// in RHS into this live interval as the specified value number.
266 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
267 /// current interval, it will replace the value numbers of the overlaped
268 /// live ranges with the specified value number.
269 void MergeRangesInAsValue(const LiveInterval &RHS, VNInfo *LHSValNo);
271 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
272 /// in RHS into this live interval as the specified value number.
273 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
274 /// current interval, but only if the overlapping LiveRanges have the
275 /// specified value number.
276 void MergeValueInAsValue(const LiveInterval &RHS,
277 const VNInfo *RHSValNo, VNInfo *LHSValNo);
279 /// Copy - Copy the specified live interval. This copies all the fields
280 /// except for the register of the interval.
281 void Copy(const LiveInterval &RHS, MachineRegisterInfo *MRI,
282 VNInfo::Allocator &VNInfoAllocator);
284 bool empty() const { return ranges.empty(); }
286 /// beginIndex - Return the lowest numbered slot covered by interval.
287 SlotIndex beginIndex() const {
288 assert(!empty() && "Call to beginIndex() on empty interval.");
289 return ranges.front().start;
292 /// endNumber - return the maximum point of the interval of the whole,
294 SlotIndex endIndex() const {
295 assert(!empty() && "Call to endIndex() on empty interval.");
296 return ranges.back().end;
299 bool expiredAt(SlotIndex index) const {
300 return index >= endIndex();
303 bool liveAt(SlotIndex index) const {
304 const_iterator r = find(index);
305 return r != end() && r->start <= index;
308 /// killedAt - Return true if a live range ends at index. Note that the kill
309 /// point is not contained in the half-open live range. It is usually the
310 /// getDefIndex() slot following its last use.
311 bool killedAt(SlotIndex index) const {
312 const_iterator r = find(index.getRegSlot(true));
313 return r != end() && r->end == index;
316 /// killedInRange - Return true if the interval has kills in [Start,End).
317 /// Note that the kill point is considered the end of a live range, so it is
318 /// not contained in the live range. If a live range ends at End, it won't
319 /// be counted as a kill by this method.
320 bool killedInRange(SlotIndex Start, SlotIndex End) const;
322 /// getLiveRangeContaining - Return the live range that contains the
323 /// specified index, or null if there is none.
324 const LiveRange *getLiveRangeContaining(SlotIndex Idx) const {
325 const_iterator I = FindLiveRangeContaining(Idx);
326 return I == end() ? 0 : &*I;
329 /// getLiveRangeContaining - Return the live range that contains the
330 /// specified index, or null if there is none.
331 LiveRange *getLiveRangeContaining(SlotIndex Idx) {
332 iterator I = FindLiveRangeContaining(Idx);
333 return I == end() ? 0 : &*I;
336 /// getVNInfoAt - Return the VNInfo that is live at Idx, or NULL.
337 VNInfo *getVNInfoAt(SlotIndex Idx) const {
338 const_iterator I = FindLiveRangeContaining(Idx);
339 return I == end() ? 0 : I->valno;
342 /// getVNInfoBefore - Return the VNInfo that is live up to but not
343 /// necessarilly including Idx, or NULL. Use this to find the reaching def
344 /// used by an instruction at this SlotIndex position.
345 VNInfo *getVNInfoBefore(SlotIndex Idx) const {
346 const_iterator I = FindLiveRangeContaining(Idx.getPrevSlot());
347 return I == end() ? 0 : I->valno;
350 /// FindLiveRangeContaining - Return an iterator to the live range that
351 /// contains the specified index, or end() if there is none.
352 iterator FindLiveRangeContaining(SlotIndex Idx) {
353 iterator I = find(Idx);
354 return I != end() && I->start <= Idx ? I : end();
357 const_iterator FindLiveRangeContaining(SlotIndex Idx) const {
358 const_iterator I = find(Idx);
359 return I != end() && I->start <= Idx ? I : end();
362 /// overlaps - Return true if the intersection of the two live intervals is
364 bool overlaps(const LiveInterval& other) const {
367 return overlapsFrom(other, other.begin());
370 /// overlaps - Return true if the two intervals have overlapping segments
371 /// that are not coalescable according to CP.
373 /// Overlapping segments where one interval is defined by a coalescable
374 /// copy are allowed.
375 bool overlaps(const LiveInterval &Other, const CoalescerPair &CP,
376 const SlotIndexes&) const;
378 /// overlaps - Return true if the live interval overlaps a range specified
380 bool overlaps(SlotIndex Start, SlotIndex End) const;
382 /// overlapsFrom - Return true if the intersection of the two live intervals
383 /// is not empty. The specified iterator is a hint that we can begin
384 /// scanning the Other interval starting at I.
385 bool overlapsFrom(const LiveInterval& other, const_iterator I) const;
387 /// addRange - Add the specified LiveRange to this interval, merging
388 /// intervals as appropriate. This returns an iterator to the inserted live
389 /// range (which may have grown since it was inserted.
390 void addRange(LiveRange LR) {
391 addRangeFrom(LR, ranges.begin());
394 /// extendInBlock - If this interval is live before Kill in the basic block
395 /// that starts at StartIdx, extend it to be live up to Kill, and return
396 /// the value. If there is no live range before Kill, return NULL.
397 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Kill);
399 /// join - Join two live intervals (this, and other) together. This applies
400 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
401 /// the intervals are not joinable, this aborts.
402 void join(LiveInterval &Other,
403 const int *ValNoAssignments,
404 const int *RHSValNoAssignments,
405 SmallVector<VNInfo*, 16> &NewVNInfo,
406 MachineRegisterInfo *MRI);
408 /// isInOneLiveRange - Return true if the range specified is entirely in the
409 /// a single LiveRange of the live interval.
410 bool isInOneLiveRange(SlotIndex Start, SlotIndex End) const {
411 const_iterator r = find(Start);
412 return r != end() && r->containsRange(Start, End);
415 /// removeRange - Remove the specified range from this interval. Note that
416 /// the range must be a single LiveRange in its entirety.
417 void removeRange(SlotIndex Start, SlotIndex End,
418 bool RemoveDeadValNo = false);
420 void removeRange(LiveRange LR, bool RemoveDeadValNo = false) {
421 removeRange(LR.start, LR.end, RemoveDeadValNo);
424 /// removeValNo - Remove all the ranges defined by the specified value#.
425 /// Also remove the value# from value# list.
426 void removeValNo(VNInfo *ValNo);
428 /// getSize - Returns the sum of sizes of all the LiveRange's.
430 unsigned getSize() const;
432 /// Returns true if the live interval is zero length, i.e. no live ranges
433 /// span instructions. It doesn't pay to spill such an interval.
434 bool isZeroLength(SlotIndexes *Indexes) const {
435 for (const_iterator i = begin(), e = end(); i != e; ++i)
436 if (Indexes->getNextNonNullIndex(i->start).getBaseIndex() <
437 i->end.getBaseIndex())
442 /// isSpillable - Can this interval be spilled?
443 bool isSpillable() const {
444 return weight != HUGE_VALF;
447 /// markNotSpillable - Mark interval as not spillable
448 void markNotSpillable() {
452 bool operator<(const LiveInterval& other) const {
453 const SlotIndex &thisIndex = beginIndex();
454 const SlotIndex &otherIndex = other.beginIndex();
455 return (thisIndex < otherIndex ||
456 (thisIndex == otherIndex && reg < other.reg));
459 void print(raw_ostream &OS) const;
462 /// \brief Walk the interval and assert if any invariants fail to hold.
464 /// Note that this is a no-op when asserts are disabled.
466 void verify() const {}
473 Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From);
474 void extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd);
475 Ranges::iterator extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStr);
476 void markValNoForDeletion(VNInfo *V);
477 void mergeIntervalRanges(const LiveInterval &RHS,
478 VNInfo *LHSValNo = 0,
479 const VNInfo *RHSValNo = 0);
481 LiveInterval& operator=(const LiveInterval& rhs); // DO NOT IMPLEMENT
485 inline raw_ostream &operator<<(raw_ostream &OS, const LiveInterval &LI) {
490 /// LiveRangeQuery - Query information about a live range around a given
491 /// instruction. This class hides the implementation details of live ranges,
492 /// and it should be used as the primary interface for examining live ranges
493 /// around instructions.
495 class LiveRangeQuery {
502 /// Create a LiveRangeQuery for the given live range and instruction index.
503 /// The sub-instruction slot of Idx doesn't matter, only the instruction it
504 /// refers to is considered.
505 LiveRangeQuery(const LiveInterval &LI, SlotIndex Idx)
506 : EarlyVal(0), LateVal(0), Kill(false) {
507 // Find the segment that enters the instruction.
508 LiveInterval::const_iterator I = LI.find(Idx.getBaseIndex());
509 LiveInterval::const_iterator E = LI.end();
512 // Is this an instruction live-in segment?
513 if (SlotIndex::isEarlierInstr(I->start, Idx)) {
516 // Move to the potentially live-out segment.
517 if (SlotIndex::isSameInstr(Idx, I->end)) {
523 // I now points to the segment that may be live-through, or defined by
524 // this instr. Ignore segments starting after the current instr.
525 if (SlotIndex::isEarlierInstr(Idx, I->start))
531 /// Return the value that is live-in to the instruction. This is the value
532 /// that will be read by the instruction's use operands. Return NULL if no
533 /// value is live-in.
534 VNInfo *valueIn() const {
538 /// Return true if the live-in value is killed by this instruction. This
539 /// means that either the live range ends at the instruction, or it changes
541 bool isKill() const {
545 /// Return true if this instruction has a dead def.
546 bool isDeadDef() const {
547 return EndPoint.isDead();
550 /// Return the value leaving the instruction, if any. This can be a
551 /// live-through value, or a live def. A dead def returns NULL.
552 VNInfo *valueOut() const {
553 return isDeadDef() ? 0 : LateVal;
556 /// Return the value defined by this instruction, if any. This includes
557 /// dead defs, it is the value created by the instruction's def operands.
558 VNInfo *valueDefined() const {
559 return EarlyVal == LateVal ? 0 : LateVal;
562 /// Return the end point of the last live range segment to interact with
563 /// the instruction, if any.
565 /// The end point is an invalid SlotIndex only if the live range doesn't
566 /// intersect the instruction at all.
568 /// The end point may be at or past the end of the instruction's basic
569 /// block. That means the value was live out of the block.
570 SlotIndex endPoint() const {
575 /// ConnectedVNInfoEqClasses - Helper class that can divide VNInfos in a
576 /// LiveInterval into equivalence clases of connected components. A
577 /// LiveInterval that has multiple connected components can be broken into
578 /// multiple LiveIntervals.
580 /// Given a LiveInterval that may have multiple connected components, run:
582 /// unsigned numComps = ConEQ.Classify(LI);
583 /// if (numComps > 1) {
584 /// // allocate numComps-1 new LiveIntervals into LIS[1..]
585 /// ConEQ.Distribute(LIS);
588 class ConnectedVNInfoEqClasses {
590 IntEqClasses EqClass;
592 // Note that values a and b are connected.
593 void Connect(unsigned a, unsigned b);
598 explicit ConnectedVNInfoEqClasses(LiveIntervals &lis) : LIS(lis) {}
600 /// Classify - Classify the values in LI into connected components.
601 /// Return the number of connected components.
602 unsigned Classify(const LiveInterval *LI);
604 /// getEqClass - Classify creates equivalence classes numbered 0..N. Return
605 /// the equivalence class assigned the VNI.
606 unsigned getEqClass(const VNInfo *VNI) const { return EqClass[VNI->id]; }
608 /// Distribute - Distribute values in LIV[0] into a separate LiveInterval
609 /// for each connected component. LIV must have a LiveInterval for each
610 /// connected component. The LiveIntervals in Liv[1..] must be empty.
611 /// Instructions using LIV[0] are rewritten.
612 void Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI);