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 bool empty() const { return ranges.empty(); }
281 /// beginIndex - Return the lowest numbered slot covered by interval.
282 SlotIndex beginIndex() const {
283 assert(!empty() && "Call to beginIndex() on empty interval.");
284 return ranges.front().start;
287 /// endNumber - return the maximum point of the interval of the whole,
289 SlotIndex endIndex() const {
290 assert(!empty() && "Call to endIndex() on empty interval.");
291 return ranges.back().end;
294 bool expiredAt(SlotIndex index) const {
295 return index >= endIndex();
298 bool liveAt(SlotIndex index) const {
299 const_iterator r = find(index);
300 return r != end() && r->start <= index;
303 /// killedAt - Return true if a live range ends at index. Note that the kill
304 /// point is not contained in the half-open live range. It is usually the
305 /// getDefIndex() slot following its last use.
306 bool killedAt(SlotIndex index) const {
307 const_iterator r = find(index.getRegSlot(true));
308 return r != end() && r->end == index;
311 /// getLiveRangeContaining - Return the live range that contains the
312 /// specified index, or null if there is none.
313 const LiveRange *getLiveRangeContaining(SlotIndex Idx) const {
314 const_iterator I = FindLiveRangeContaining(Idx);
315 return I == end() ? 0 : &*I;
318 /// getLiveRangeContaining - Return the live range that contains the
319 /// specified index, or null if there is none.
320 LiveRange *getLiveRangeContaining(SlotIndex Idx) {
321 iterator I = FindLiveRangeContaining(Idx);
322 return I == end() ? 0 : &*I;
325 /// getVNInfoAt - Return the VNInfo that is live at Idx, or NULL.
326 VNInfo *getVNInfoAt(SlotIndex Idx) const {
327 const_iterator I = FindLiveRangeContaining(Idx);
328 return I == end() ? 0 : I->valno;
331 /// getVNInfoBefore - Return the VNInfo that is live up to but not
332 /// necessarilly including Idx, or NULL. Use this to find the reaching def
333 /// used by an instruction at this SlotIndex position.
334 VNInfo *getVNInfoBefore(SlotIndex Idx) const {
335 const_iterator I = FindLiveRangeContaining(Idx.getPrevSlot());
336 return I == end() ? 0 : I->valno;
339 /// FindLiveRangeContaining - Return an iterator to the live range that
340 /// contains the specified index, or end() if there is none.
341 iterator FindLiveRangeContaining(SlotIndex Idx) {
342 iterator I = find(Idx);
343 return I != end() && I->start <= Idx ? I : end();
346 const_iterator FindLiveRangeContaining(SlotIndex Idx) const {
347 const_iterator I = find(Idx);
348 return I != end() && I->start <= Idx ? I : end();
351 /// overlaps - Return true if the intersection of the two live intervals is
353 bool overlaps(const LiveInterval& other) const {
356 return overlapsFrom(other, other.begin());
359 /// overlaps - Return true if the two intervals have overlapping segments
360 /// that are not coalescable according to CP.
362 /// Overlapping segments where one interval is defined by a coalescable
363 /// copy are allowed.
364 bool overlaps(const LiveInterval &Other, const CoalescerPair &CP,
365 const SlotIndexes&) const;
367 /// overlaps - Return true if the live interval overlaps a range specified
369 bool overlaps(SlotIndex Start, SlotIndex End) const;
371 /// overlapsFrom - Return true if the intersection of the two live intervals
372 /// is not empty. The specified iterator is a hint that we can begin
373 /// scanning the Other interval starting at I.
374 bool overlapsFrom(const LiveInterval& other, const_iterator I) const;
376 /// addRange - Add the specified LiveRange to this interval, merging
377 /// intervals as appropriate. This returns an iterator to the inserted live
378 /// range (which may have grown since it was inserted.
379 void addRange(LiveRange LR) {
380 addRangeFrom(LR, ranges.begin());
383 /// extendInBlock - If this interval is live before Kill in the basic block
384 /// that starts at StartIdx, extend it to be live up to Kill, and return
385 /// the value. If there is no live range before Kill, return NULL.
386 VNInfo *extendInBlock(SlotIndex StartIdx, SlotIndex Kill);
388 /// join - Join two live intervals (this, and other) together. This applies
389 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
390 /// the intervals are not joinable, this aborts.
391 void join(LiveInterval &Other,
392 const int *ValNoAssignments,
393 const int *RHSValNoAssignments,
394 SmallVector<VNInfo*, 16> &NewVNInfo,
395 MachineRegisterInfo *MRI);
397 /// isInOneLiveRange - Return true if the range specified is entirely in the
398 /// a single LiveRange of the live interval.
399 bool isInOneLiveRange(SlotIndex Start, SlotIndex End) const {
400 const_iterator r = find(Start);
401 return r != end() && r->containsRange(Start, End);
404 /// removeRange - Remove the specified range from this interval. Note that
405 /// the range must be a single LiveRange in its entirety.
406 void removeRange(SlotIndex Start, SlotIndex End,
407 bool RemoveDeadValNo = false);
409 void removeRange(LiveRange LR, bool RemoveDeadValNo = false) {
410 removeRange(LR.start, LR.end, RemoveDeadValNo);
413 /// removeValNo - Remove all the ranges defined by the specified value#.
414 /// Also remove the value# from value# list.
415 void removeValNo(VNInfo *ValNo);
417 /// getSize - Returns the sum of sizes of all the LiveRange's.
419 unsigned getSize() const;
421 /// Returns true if the live interval is zero length, i.e. no live ranges
422 /// span instructions. It doesn't pay to spill such an interval.
423 bool isZeroLength(SlotIndexes *Indexes) const {
424 for (const_iterator i = begin(), e = end(); i != e; ++i)
425 if (Indexes->getNextNonNullIndex(i->start).getBaseIndex() <
426 i->end.getBaseIndex())
431 /// isSpillable - Can this interval be spilled?
432 bool isSpillable() const {
433 return weight != HUGE_VALF;
436 /// markNotSpillable - Mark interval as not spillable
437 void markNotSpillable() {
441 bool operator<(const LiveInterval& other) const {
442 const SlotIndex &thisIndex = beginIndex();
443 const SlotIndex &otherIndex = other.beginIndex();
444 return (thisIndex < otherIndex ||
445 (thisIndex == otherIndex && reg < other.reg));
448 void print(raw_ostream &OS) const;
451 /// \brief Walk the interval and assert if any invariants fail to hold.
453 /// Note that this is a no-op when asserts are disabled.
455 void verify() const {}
462 Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From);
463 void extendIntervalEndTo(Ranges::iterator I, SlotIndex NewEnd);
464 Ranges::iterator extendIntervalStartTo(Ranges::iterator I, SlotIndex NewStr);
465 void markValNoForDeletion(VNInfo *V);
466 void mergeIntervalRanges(const LiveInterval &RHS,
467 VNInfo *LHSValNo = 0,
468 const VNInfo *RHSValNo = 0);
470 LiveInterval& operator=(const LiveInterval& rhs); // DO NOT IMPLEMENT
474 inline raw_ostream &operator<<(raw_ostream &OS, const LiveInterval &LI) {
479 /// LiveRangeQuery - Query information about a live range around a given
480 /// instruction. This class hides the implementation details of live ranges,
481 /// and it should be used as the primary interface for examining live ranges
482 /// around instructions.
484 class LiveRangeQuery {
491 /// Create a LiveRangeQuery for the given live range and instruction index.
492 /// The sub-instruction slot of Idx doesn't matter, only the instruction it
493 /// refers to is considered.
494 LiveRangeQuery(const LiveInterval &LI, SlotIndex Idx)
495 : EarlyVal(0), LateVal(0), Kill(false) {
496 // Find the segment that enters the instruction.
497 LiveInterval::const_iterator I = LI.find(Idx.getBaseIndex());
498 LiveInterval::const_iterator E = LI.end();
501 // Is this an instruction live-in segment?
502 if (SlotIndex::isEarlierInstr(I->start, Idx)) {
505 // Move to the potentially live-out segment.
506 if (SlotIndex::isSameInstr(Idx, I->end)) {
512 // I now points to the segment that may be live-through, or defined by
513 // this instr. Ignore segments starting after the current instr.
514 if (SlotIndex::isEarlierInstr(Idx, I->start))
520 /// Return the value that is live-in to the instruction. This is the value
521 /// that will be read by the instruction's use operands. Return NULL if no
522 /// value is live-in.
523 VNInfo *valueIn() const {
527 /// Return true if the live-in value is killed by this instruction. This
528 /// means that either the live range ends at the instruction, or it changes
530 bool isKill() const {
534 /// Return true if this instruction has a dead def.
535 bool isDeadDef() const {
536 return EndPoint.isDead();
539 /// Return the value leaving the instruction, if any. This can be a
540 /// live-through value, or a live def. A dead def returns NULL.
541 VNInfo *valueOut() const {
542 return isDeadDef() ? 0 : LateVal;
545 /// Return the value defined by this instruction, if any. This includes
546 /// dead defs, it is the value created by the instruction's def operands.
547 VNInfo *valueDefined() const {
548 return EarlyVal == LateVal ? 0 : LateVal;
551 /// Return the end point of the last live range segment to interact with
552 /// the instruction, if any.
554 /// The end point is an invalid SlotIndex only if the live range doesn't
555 /// intersect the instruction at all.
557 /// The end point may be at or past the end of the instruction's basic
558 /// block. That means the value was live out of the block.
559 SlotIndex endPoint() const {
564 /// ConnectedVNInfoEqClasses - Helper class that can divide VNInfos in a
565 /// LiveInterval into equivalence clases of connected components. A
566 /// LiveInterval that has multiple connected components can be broken into
567 /// multiple LiveIntervals.
569 /// Given a LiveInterval that may have multiple connected components, run:
571 /// unsigned numComps = ConEQ.Classify(LI);
572 /// if (numComps > 1) {
573 /// // allocate numComps-1 new LiveIntervals into LIS[1..]
574 /// ConEQ.Distribute(LIS);
577 class ConnectedVNInfoEqClasses {
579 IntEqClasses EqClass;
581 // Note that values a and b are connected.
582 void Connect(unsigned a, unsigned b);
587 explicit ConnectedVNInfoEqClasses(LiveIntervals &lis) : LIS(lis) {}
589 /// Classify - Classify the values in LI into connected components.
590 /// Return the number of connected components.
591 unsigned Classify(const LiveInterval *LI);
593 /// getEqClass - Classify creates equivalence classes numbered 0..N. Return
594 /// the equivalence class assigned the VNI.
595 unsigned getEqClass(const VNInfo *VNI) const { return EqClass[VNI->id]; }
597 /// Distribute - Distribute values in LIV[0] into a separate LiveInterval
598 /// for each connected component. LIV must have a LiveInterval for each
599 /// connected component. The LiveIntervals in Liv[1..] must be empty.
600 /// Instructions using LIV[0] are rewritten.
601 void Distribute(LiveInterval *LIV[], MachineRegisterInfo &MRI);