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"
34 class MachineRegisterInfo;
35 class TargetRegisterInfo;
38 /// VNInfo - Value Number Information.
39 /// This class holds information about a machine level values, including
40 /// definition and use points.
44 typedef BumpPtrAllocator Allocator;
46 /// The ID number of this value.
49 /// The index of the defining instruction.
52 /// VNInfo constructor.
53 VNInfo(unsigned i, SlotIndex d)
57 /// VNInfo construtor, copies values from orig, except for the value number.
58 VNInfo(unsigned i, const VNInfo &orig)
59 : id(i), def(orig.def)
62 /// Copy from the parameter into this VNInfo.
63 void copyFrom(VNInfo &src) {
67 /// Returns true if this value is defined by a PHI instruction (or was,
68 /// PHI instrucions may have been eliminated).
69 /// PHI-defs begin at a block boundary, all other defs begin at register or
71 bool isPHIDef() const { return def.isBlock(); }
73 /// Returns true if this value is unused.
74 bool isUnused() const { return !def.isValid(); }
76 /// Mark this value as unused.
77 void markUnused() { def = SlotIndex(); }
80 /// LiveRange structure - This represents a simple register range in the
81 /// program, with an inclusive start point and an exclusive end point.
82 /// These ranges are rendered as [start,end).
84 SlotIndex start; // Start point of the interval (inclusive)
85 SlotIndex end; // End point of the interval (exclusive)
86 VNInfo *valno; // identifier for the value contained in this interval.
88 LiveRange(SlotIndex S, SlotIndex E, VNInfo *V)
89 : start(S), end(E), valno(V) {
91 assert(S < E && "Cannot create empty or backwards range");
94 /// contains - Return true if the index is covered by this range.
96 bool contains(SlotIndex I) const {
97 return start <= I && I < end;
100 /// containsRange - Return true if the given range, [S, E), is covered by
102 bool containsRange(SlotIndex S, SlotIndex E) const {
103 assert((S < E) && "Backwards interval?");
104 return (start <= S && S < end) && (start < E && E <= end);
107 bool operator<(const LiveRange &LR) const {
108 return start < LR.start || (start == LR.start && end < LR.end);
110 bool operator==(const LiveRange &LR) const {
111 return start == LR.start && end == LR.end;
115 void print(raw_ostream &os) const;
118 LiveRange(); // DO NOT IMPLEMENT
121 template <> struct isPodLike<LiveRange> { static const bool value = true; };
123 raw_ostream& operator<<(raw_ostream& os, const LiveRange &LR);
126 inline bool operator<(SlotIndex V, const LiveRange &LR) {
130 inline bool operator<(const LiveRange &LR, SlotIndex V) {
134 /// LiveInterval - This class represents some number of live ranges for a
135 /// register or value. This class also contains a bit of register allocator
140 typedef SmallVector<LiveRange,4> Ranges;
141 typedef SmallVector<VNInfo*,4> VNInfoList;
143 const unsigned reg; // the register or stack slot of this interval.
144 float weight; // weight of this interval
145 Ranges ranges; // the ranges in which this register is live
146 VNInfoList valnos; // value#'s
159 LiveInterval(unsigned Reg, float Weight)
160 : reg(Reg), weight(Weight) {}
162 typedef Ranges::iterator iterator;
163 iterator begin() { return ranges.begin(); }
164 iterator end() { return ranges.end(); }
166 typedef Ranges::const_iterator const_iterator;
167 const_iterator begin() const { return ranges.begin(); }
168 const_iterator end() const { return ranges.end(); }
170 typedef VNInfoList::iterator vni_iterator;
171 vni_iterator vni_begin() { return valnos.begin(); }
172 vni_iterator vni_end() { return valnos.end(); }
174 typedef VNInfoList::const_iterator const_vni_iterator;
175 const_vni_iterator vni_begin() const { return valnos.begin(); }
176 const_vni_iterator vni_end() const { return valnos.end(); }
178 /// advanceTo - Advance the specified iterator to point to the LiveRange
179 /// containing the specified position, or end() if the position is past the
180 /// end of the interval. If no LiveRange contains this position, but the
181 /// position is in a hole, this method returns an iterator pointing to the
182 /// LiveRange immediately after the hole.
183 iterator advanceTo(iterator I, SlotIndex Pos) {
185 if (Pos >= endIndex())
187 while (I->end <= Pos) ++I;
191 /// find - Return an iterator pointing to the first range that ends after
192 /// Pos, or end(). This is the same as advanceTo(begin(), Pos), but faster
193 /// when searching large intervals.
195 /// If Pos is contained in a LiveRange, that range is returned.
196 /// If Pos is in a hole, the following LiveRange is returned.
197 /// If Pos is beyond endIndex, end() is returned.
198 iterator find(SlotIndex Pos);
200 const_iterator find(SlotIndex Pos) const {
201 return const_cast<LiveInterval*>(this)->find(Pos);
209 bool hasAtLeastOneValue() const { return !valnos.empty(); }
211 bool containsOneValue() const { return valnos.size() == 1; }
213 unsigned getNumValNums() const { return (unsigned)valnos.size(); }
215 /// getValNumInfo - Returns pointer to the specified val#.
217 inline VNInfo *getValNumInfo(unsigned ValNo) {
218 return valnos[ValNo];
220 inline const VNInfo *getValNumInfo(unsigned ValNo) const {
221 return valnos[ValNo];
224 /// containsValue - Returns true if VNI belongs to this interval.
225 bool containsValue(const VNInfo *VNI) const {
226 return VNI && VNI->id < getNumValNums() && VNI == getValNumInfo(VNI->id);
229 /// getNextValue - Create a new value number and return it. MIIdx specifies
230 /// the instruction that defines the value number.
231 VNInfo *getNextValue(SlotIndex def, VNInfo::Allocator &VNInfoAllocator) {
233 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), def);
234 valnos.push_back(VNI);
238 /// createDeadDef - Make sure the interval has a value defined at Def.
239 /// If one already exists, return it. Otherwise allocate a new value and
240 /// add liveness for a dead def.
241 VNInfo *createDeadDef(SlotIndex Def, VNInfo::Allocator &VNInfoAllocator);
243 /// Create a copy of the given value. The new value will be identical except
244 /// for the Value number.
245 VNInfo *createValueCopy(const VNInfo *orig,
246 VNInfo::Allocator &VNInfoAllocator) {
248 new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), *orig);
249 valnos.push_back(VNI);
253 /// RenumberValues - Renumber all values in order of appearance and remove
255 void RenumberValues(LiveIntervals &lis);
257 /// MergeValueNumberInto - This method is called when two value nubmers
258 /// are found to be equivalent. This eliminates V1, replacing all
259 /// LiveRanges with the V1 value number with the V2 value number. This can
260 /// cause merging of V1/V2 values numbers and compaction of the value space.
261 VNInfo* MergeValueNumberInto(VNInfo *V1, VNInfo *V2);
263 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
264 /// in RHS into this live interval as the specified value number.
265 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
266 /// current interval, it will replace the value numbers of the overlaped
267 /// live ranges with the specified value number.
268 void MergeRangesInAsValue(const LiveInterval &RHS, VNInfo *LHSValNo);
270 /// MergeValueInAsValue - Merge all of the live ranges of a specific val#
271 /// in RHS into this live interval as the specified value number.
272 /// The LiveRanges in RHS are allowed to overlap with LiveRanges in the
273 /// current interval, but only if the overlapping LiveRanges have the
274 /// specified value number.
275 void MergeValueInAsValue(const LiveInterval &RHS,
276 const VNInfo *RHSValNo, VNInfo *LHSValNo);
278 /// Copy - Copy the specified live interval. This copies all the fields
279 /// except for the register of the interval.
280 void Copy(const LiveInterval &RHS, MachineRegisterInfo *MRI,
281 VNInfo::Allocator &VNInfoAllocator);
283 bool empty() const { return ranges.empty(); }
285 /// beginIndex - Return the lowest numbered slot covered by interval.
286 SlotIndex beginIndex() const {
287 assert(!empty() && "Call to beginIndex() on empty interval.");
288 return ranges.front().start;
291 /// endNumber - return the maximum point of the interval of the whole,
293 SlotIndex endIndex() const {
294 assert(!empty() && "Call to endIndex() on empty interval.");
295 return ranges.back().end;
298 bool expiredAt(SlotIndex index) const {
299 return index >= endIndex();
302 bool liveAt(SlotIndex index) const {
303 const_iterator r = find(index);
304 return r != end() && r->start <= index;
307 /// killedAt - Return true if a live range ends at index. Note that the kill
308 /// point is not contained in the half-open live range. It is usually the
309 /// getDefIndex() slot following its last use.
310 bool killedAt(SlotIndex index) const {
311 const_iterator r = find(index.getRegSlot(true));
312 return r != end() && r->end == index;
315 /// killedInRange - Return true if the interval has kills in [Start,End).
316 /// Note that the kill point is considered the end of a live range, so it is
317 /// not contained in the live range. If a live range ends at End, it won't
318 /// be counted as a kill by this method.
319 bool killedInRange(SlotIndex Start, SlotIndex End) const;
321 /// getLiveRangeContaining - Return the live range that contains the
322 /// specified index, or null if there is none.
323 const LiveRange *getLiveRangeContaining(SlotIndex Idx) const {
324 const_iterator I = FindLiveRangeContaining(Idx);
325 return I == end() ? 0 : &*I;
328 /// getLiveRangeContaining - Return the live range that contains the
329 /// specified index, or null if there is none.
330 LiveRange *getLiveRangeContaining(SlotIndex Idx) {
331 iterator I = FindLiveRangeContaining(Idx);
332 return I == end() ? 0 : &*I;
335 /// getVNInfoAt - Return the VNInfo that is live at Idx, or NULL.
336 VNInfo *getVNInfoAt(SlotIndex Idx) const {
337 const_iterator I = FindLiveRangeContaining(Idx);
338 return I == end() ? 0 : I->valno;
341 /// getVNInfoBefore - Return the VNInfo that is live up to but not
342 /// necessarilly including Idx, or NULL. Use this to find the reaching def
343 /// used by an instruction at this SlotIndex position.
344 VNInfo *getVNInfoBefore(SlotIndex Idx) const {
345 const_iterator I = FindLiveRangeContaining(Idx.getPrevSlot());
346 return I == end() ? 0 : I->valno;
349 /// FindLiveRangeContaining - Return an iterator to the live range that
350 /// contains the specified index, or end() if there is none.
351 iterator FindLiveRangeContaining(SlotIndex Idx) {
352 iterator I = find(Idx);
353 return I != end() && I->start <= Idx ? I : end();
356 const_iterator FindLiveRangeContaining(SlotIndex Idx) const {
357 const_iterator I = find(Idx);
358 return I != end() && I->start <= Idx ? I : end();
361 /// overlaps - Return true if the intersection of the two live intervals is
363 bool overlaps(const LiveInterval& other) const {
366 return overlapsFrom(other, other.begin());
369 /// overlaps - Return true if the live interval overlaps a range specified
371 bool overlaps(SlotIndex Start, SlotIndex End) const;
373 /// overlapsFrom - Return true if the intersection of the two live intervals
374 /// is not empty. The specified iterator is a hint that we can begin
375 /// scanning the Other interval starting at I.
376 bool overlapsFrom(const LiveInterval& other, const_iterator I) const;
378 /// addRange - Add the specified LiveRange to this interval, merging
379 /// intervals as appropriate. This returns an iterator to the inserted live
380 /// range (which may have grown since it was inserted.
381 void addRange(LiveRange LR) {
382 addRangeFrom(LR, ranges.begin());
385 /// extendInBlock - If this interval is live before Kill in the basic block
386 /// that starts at StartIdx, extend it to be live up to Kill, and return
387 /// the value. If there is no live range before Kill, return NULL.
388 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Kill);
390 /// join - Join two live intervals (this, and other) together. This applies
391 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
392 /// the intervals are not joinable, this aborts.
393 void join(LiveInterval &Other,
394 const int *ValNoAssignments,
395 const int *RHSValNoAssignments,
396 SmallVector<VNInfo*, 16> &NewVNInfo,
397 MachineRegisterInfo *MRI);
399 /// isInOneLiveRange - Return true if the range specified is entirely in the
400 /// a single LiveRange of the live interval.
401 bool isInOneLiveRange(SlotIndex Start, SlotIndex End) const {
402 const_iterator r = find(Start);
403 return r != end() && r->containsRange(Start, End);
406 /// removeRange - Remove the specified range from this interval. Note that
407 /// the range must be a single LiveRange in its entirety.
408 void removeRange(SlotIndex Start, SlotIndex End,
409 bool RemoveDeadValNo = false);
411 void removeRange(LiveRange LR, bool RemoveDeadValNo = false) {
412 removeRange(LR.start, LR.end, RemoveDeadValNo);
415 /// removeValNo - Remove all the ranges defined by the specified value#.
416 /// Also remove the value# from value# list.
417 void removeValNo(VNInfo *ValNo);
419 /// getSize - Returns the sum of sizes of all the LiveRange's.
421 unsigned getSize() const;
423 /// Returns true if the live interval is zero length, i.e. no live ranges
424 /// span instructions. It doesn't pay to spill such an interval.
425 bool isZeroLength(SlotIndexes *Indexes) const {
426 for (const_iterator i = begin(), e = end(); i != e; ++i)
427 if (Indexes->getNextNonNullIndex(i->start).getBaseIndex() <
428 i->end.getBaseIndex())
433 /// isSpillable - Can this interval be spilled?
434 bool isSpillable() const {
435 return weight != HUGE_VALF;
438 /// markNotSpillable - Mark interval as not spillable
439 void markNotSpillable() {
443 bool operator<(const LiveInterval& other) const {
444 const SlotIndex &thisIndex = beginIndex();
445 const SlotIndex &otherIndex = other.beginIndex();
446 return (thisIndex < otherIndex ||
447 (thisIndex == otherIndex && reg < other.reg));
450 void print(raw_ostream &OS) const;
453 /// \brief Walk the interval and assert if any invariants fail to hold.
455 /// Note that this is a no-op when asserts are disabled.
457 void verify() const {}
464 Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From);
465 void extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd);
466 Ranges::iterator extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStr);
467 void markValNoForDeletion(VNInfo *V);
468 void mergeIntervalRanges(const LiveInterval &RHS,
469 VNInfo *LHSValNo = 0,
470 const VNInfo *RHSValNo = 0);
472 LiveInterval& operator=(const LiveInterval& rhs); // DO NOT IMPLEMENT
476 inline raw_ostream &operator<<(raw_ostream &OS, const LiveInterval &LI) {
481 /// LiveRangeQuery - Query information about a live range around a given
482 /// instruction. This class hides the implementation details of live ranges,
483 /// and it should be used as the primary interface for examining live ranges
484 /// around instructions.
486 class LiveRangeQuery {
493 /// Create a LiveRangeQuery for the given live range and instruction index.
494 /// The sub-instruction slot of Idx doesn't matter, only the instruction it
495 /// refers to is considered.
496 LiveRangeQuery(const LiveInterval &LI, SlotIndex Idx)
497 : EarlyVal(0), LateVal(0), Kill(false) {
498 // Find the segment that enters the instruction.
499 LiveInterval::const_iterator I = LI.find(Idx.getBaseIndex());
500 LiveInterval::const_iterator E = LI.end();
503 // Is this an instruction live-in segment?
504 if (SlotIndex::isEarlierInstr(I->start, Idx)) {
507 // Move to the potentially live-out segment.
508 if (SlotIndex::isSameInstr(Idx, I->end)) {
514 // I now points to the segment that may be live-through, or defined by
515 // this instr. Ignore segments starting after the current instr.
516 if (SlotIndex::isEarlierInstr(Idx, I->start))
522 /// Return the value that is live-in to the instruction. This is the value
523 /// that will be read by the instruction's use operands. Return NULL if no
524 /// value is live-in.
525 VNInfo *valueIn() const {
529 /// Return true if the live-in value is killed by this instruction. This
530 /// means that either the live range ends at the instruction, or it changes
532 bool isKill() const {
536 /// Return true if this instruction has a dead def.
537 bool isDeadDef() const {
538 return EndPoint.isDead();
541 /// Return the value leaving the instruction, if any. This can be a
542 /// live-through value, or a live def. A dead def returns NULL.
543 VNInfo *valueOut() const {
544 return isDeadDef() ? 0 : LateVal;
547 /// Return the value defined by this instruction, if any. This includes
548 /// dead defs, it is the value created by the instruction's def operands.
549 VNInfo *valueDefined() const {
550 return EarlyVal == LateVal ? 0 : LateVal;
553 /// Return the end point of the last live range segment to interact with
554 /// the instruction, if any.
556 /// The end point is an invalid SlotIndex only if the live range doesn't
557 /// intersect the instruction at all.
559 /// The end point may be at or past the end of the instruction's basic
560 /// block. That means the value was live out of the block.
561 SlotIndex endPoint() const {
566 /// ConnectedVNInfoEqClasses - Helper class that can divide VNInfos in a
567 /// LiveInterval into equivalence clases of connected components. A
568 /// LiveInterval that has multiple connected components can be broken into
569 /// multiple LiveIntervals.
571 /// Given a LiveInterval that may have multiple connected components, run:
573 /// unsigned numComps = ConEQ.Classify(LI);
574 /// if (numComps > 1) {
575 /// // allocate numComps-1 new LiveIntervals into LIS[1..]
576 /// ConEQ.Distribute(LIS);
579 class ConnectedVNInfoEqClasses {
581 IntEqClasses EqClass;
583 // Note that values a and b are connected.
584 void Connect(unsigned a, unsigned b);
589 explicit ConnectedVNInfoEqClasses(LiveIntervals &lis) : LIS(lis) {}
591 /// Classify - Classify the values in LI into connected components.
592 /// Return the number of connected components.
593 unsigned Classify(const LiveInterval *LI);
595 /// getEqClass - Classify creates equivalence classes numbered 0..N. Return
596 /// the equivalence class assigned the VNI.
597 unsigned getEqClass(const VNInfo *VNI) const { return EqClass[VNI->id]; }
599 /// Distribute - Distribute values in LIV[0] into a separate LiveInterval
600 /// for each connected component. LIV must have a LiveInterval for each
601 /// connected component. The LiveIntervals in Liv[1..] must be empty.
602 /// Instructions using LIV[0] are rewritten.
603 void Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI);