1 //===-- LiveInterval.cpp - Live Interval Representation -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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' abd 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 #include "llvm/CodeGen/LiveInterval.h"
22 #include "llvm/ADT/STLExtras.h"
23 #include "llvm/Support/Streams.h"
24 #include "llvm/Target/MRegisterInfo.h"
30 // An example for liveAt():
32 // this = [1,4), liveAt(0) will return false. The instruction defining this
33 // spans slots [0,3]. The interval belongs to an spilled definition of the
34 // variable it represents. This is because slot 1 is used (def slot) and spans
35 // up to slot 3 (store slot).
37 bool LiveInterval::liveAt(unsigned I) const {
38 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
40 if (r == ranges.begin())
44 return r->contains(I);
47 // overlaps - Return true if the intersection of the two live intervals is
50 // An example for overlaps():
54 // 8: C = A + B ;; last use of A
56 // The live intervals should look like:
62 // A->overlaps(C) should return false since we want to be able to join
65 bool LiveInterval::overlapsFrom(const LiveInterval& other,
66 const_iterator StartPos) const {
67 const_iterator i = begin();
68 const_iterator ie = end();
69 const_iterator j = StartPos;
70 const_iterator je = other.end();
72 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
73 StartPos != other.end() && "Bogus start position hint!");
75 if (i->start < j->start) {
76 i = std::upper_bound(i, ie, j->start);
77 if (i != ranges.begin()) --i;
78 } else if (j->start < i->start) {
80 if (StartPos != other.end() && StartPos->start <= i->start) {
81 assert(StartPos < other.end() && i < end());
82 j = std::upper_bound(j, je, i->start);
83 if (j != other.ranges.begin()) --j;
89 if (j == je) return false;
92 if (i->start > j->start) {
97 if (i->end > j->start)
105 /// extendIntervalEndTo - This method is used when we want to extend the range
106 /// specified by I to end at the specified endpoint. To do this, we should
107 /// merge and eliminate all ranges that this will overlap with. The iterator is
109 void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) {
110 assert(I != ranges.end() && "Not a valid interval!");
111 unsigned ValId = I->ValId;
113 // Search for the first interval that we can't merge with.
114 Ranges::iterator MergeTo = next(I);
115 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
116 assert(MergeTo->ValId == ValId && "Cannot merge with differing values!");
119 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
120 I->end = std::max(NewEnd, prior(MergeTo)->end);
122 // Erase any dead ranges.
123 ranges.erase(next(I), MergeTo);
125 // If the newly formed range now touches the range after it and if they have
126 // the same value number, merge the two ranges into one range.
127 Ranges::iterator Next = next(I);
128 if (Next != ranges.end() && Next->start <= I->end && Next->ValId == ValId) {
135 /// extendIntervalStartTo - This method is used when we want to extend the range
136 /// specified by I to start at the specified endpoint. To do this, we should
137 /// merge and eliminate all ranges that this will overlap with.
138 LiveInterval::Ranges::iterator
139 LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) {
140 assert(I != ranges.end() && "Not a valid interval!");
141 unsigned ValId = I->ValId;
143 // Search for the first interval that we can't merge with.
144 Ranges::iterator MergeTo = I;
146 if (MergeTo == ranges.begin()) {
148 ranges.erase(MergeTo, I);
151 assert(MergeTo->ValId == ValId && "Cannot merge with differing values!");
153 } while (NewStart <= MergeTo->start);
155 // If we start in the middle of another interval, just delete a range and
156 // extend that interval.
157 if (MergeTo->end >= NewStart && MergeTo->ValId == ValId) {
158 MergeTo->end = I->end;
160 // Otherwise, extend the interval right after.
162 MergeTo->start = NewStart;
163 MergeTo->end = I->end;
166 ranges.erase(next(MergeTo), next(I));
170 LiveInterval::iterator
171 LiveInterval::addRangeFrom(LiveRange LR, iterator From) {
172 unsigned Start = LR.start, End = LR.end;
173 iterator it = std::upper_bound(From, ranges.end(), Start);
175 // If the inserted interval starts in the middle or right at the end of
176 // another interval, just extend that interval to contain the range of LR.
177 if (it != ranges.begin()) {
178 iterator B = prior(it);
179 if (LR.ValId == B->ValId) {
180 if (B->start <= Start && B->end >= Start) {
181 extendIntervalEndTo(B, End);
185 // Check to make sure that we are not overlapping two live ranges with
186 // different ValId's.
187 assert(B->end <= Start &&
188 "Cannot overlap two LiveRanges with differing ValID's"
189 " (did you def the same reg twice in a MachineInstr?)");
193 // Otherwise, if this range ends in the middle of, or right next to, another
194 // interval, merge it into that interval.
195 if (it != ranges.end())
196 if (LR.ValId == it->ValId) {
197 if (it->start <= End) {
198 it = extendIntervalStartTo(it, Start);
200 // If LR is a complete superset of an interval, we may need to grow its
203 extendIntervalEndTo(it, End);
207 // Check to make sure that we are not overlapping two live ranges with
208 // different ValId's.
209 assert(it->start >= End &&
210 "Cannot overlap two LiveRanges with differing ValID's");
213 // Otherwise, this is just a new range that doesn't interact with anything.
215 return ranges.insert(it, LR);
219 /// removeRange - Remove the specified range from this interval. Note that
220 /// the range must already be in this interval in its entirety.
221 void LiveInterval::removeRange(unsigned Start, unsigned End) {
222 // Find the LiveRange containing this span.
223 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
224 assert(I != ranges.begin() && "Range is not in interval!");
226 assert(I->contains(Start) && I->contains(End-1) &&
227 "Range is not entirely in interval!");
229 // If the span we are removing is at the start of the LiveRange, adjust it.
230 if (I->start == Start) {
232 ranges.erase(I); // Removed the whole LiveRange.
238 // Otherwise if the span we are removing is at the end of the LiveRange,
239 // adjust the other way.
245 // Otherwise, we are splitting the LiveRange into two pieces.
246 unsigned OldEnd = I->end;
247 I->end = Start; // Trim the old interval.
249 // Insert the new one.
250 ranges.insert(next(I), LiveRange(End, OldEnd, I->ValId));
253 /// getLiveRangeContaining - Return the live range that contains the
254 /// specified index, or null if there is none.
255 LiveInterval::const_iterator
256 LiveInterval::FindLiveRangeContaining(unsigned Idx) const {
257 const_iterator It = std::upper_bound(begin(), end(), Idx);
258 if (It != ranges.begin()) {
260 if (It->contains(Idx))
267 LiveInterval::iterator
268 LiveInterval::FindLiveRangeContaining(unsigned Idx) {
269 iterator It = std::upper_bound(begin(), end(), Idx);
272 if (It->contains(Idx))
279 /// join - Join two live intervals (this, and other) together. This applies
280 /// mappings to the value numbers in the LHS/RHS intervals as specified. If
281 /// the intervals are not joinable, this aborts.
282 void LiveInterval::join(LiveInterval &Other, int *LHSValNoAssignments,
283 int *RHSValNoAssignments,
284 SmallVector<std::pair<unsigned,
285 unsigned>, 16> &NewValueNumberInfo) {
287 // Try to do the least amount of work possible. In particular, if there are
288 // more liverange chunks in the other set than there are in the 'this' set,
289 // swap sets to merge the fewest chunks in possible.
291 // Also, if one range is a physreg and one is a vreg, we always merge from the
292 // vreg into the physreg, which leaves the vreg intervals pristine.
293 if ((Other.ranges.size() > ranges.size() &&
294 MRegisterInfo::isVirtualRegister(reg)) ||
295 MRegisterInfo::isPhysicalRegister(Other.reg)) {
297 std::swap(LHSValNoAssignments, RHSValNoAssignments);
300 // Determine if any of our live range values are mapped. This is uncommon, so
301 // we want to avoid the interval scan if not.
302 bool MustMapCurValNos = false;
303 for (unsigned i = 0, e = getNumValNums(); i != e; ++i) {
304 if (ValueNumberInfo[i].first == ~2U) continue; // tombstone value #
305 if (i != (unsigned)LHSValNoAssignments[i]) {
306 MustMapCurValNos = true;
311 // If we have to apply a mapping to our base interval assignment, rewrite it
313 if (MustMapCurValNos) {
314 // Map the first live range.
315 iterator OutIt = begin();
316 OutIt->ValId = LHSValNoAssignments[OutIt->ValId];
318 for (iterator I = OutIt, E = end(); I != E; ++I) {
319 OutIt->ValId = LHSValNoAssignments[I->ValId];
321 // If this live range has the same value # as its immediate predecessor,
322 // and if they are neighbors, remove one LiveRange. This happens when we
323 // have [0,3:0)[4,7:1) and map 0/1 onto the same value #.
324 if (OutIt->ValId == (OutIt-1)->ValId && (OutIt-1)->end == OutIt->start) {
325 (OutIt-1)->end = OutIt->end;
328 OutIt->start = I->start;
332 // Didn't merge, on to the next one.
337 // If we merge some live ranges, chop off the end.
338 ranges.erase(OutIt, end());
341 // Okay, now insert the RHS live ranges into the LHS.
342 iterator InsertPos = begin();
343 for (iterator I = Other.begin(), E = Other.end(); I != E; ++I) {
344 // Map the ValId in the other live range to the current live range.
345 I->ValId = RHSValNoAssignments[I->ValId];
346 InsertPos = addRangeFrom(*I, InsertPos);
349 ValueNumberInfo.clear();
350 ValueNumberInfo.append(NewValueNumberInfo.begin(), NewValueNumberInfo.end());
351 weight += Other.weight;
352 if (Other.preference && !preference)
353 preference = Other.preference;
356 /// MergeRangesInAsValue - Merge all of the intervals in RHS into this live
357 /// interval as the specified value number. The LiveRanges in RHS are
358 /// allowed to overlap with LiveRanges in the current interval, but only if
359 /// the overlapping LiveRanges have the specified value number.
360 void LiveInterval::MergeRangesInAsValue(const LiveInterval &RHS,
362 // TODO: Make this more efficient.
363 iterator InsertPos = begin();
364 for (const_iterator I = RHS.begin(), E = RHS.end(); I != E; ++I) {
365 // Map the ValId in the other live range to the current live range.
367 Tmp.ValId = LHSValNo;
368 InsertPos = addRangeFrom(Tmp, InsertPos);
373 /// MergeInClobberRanges - For any live ranges that are not defined in the
374 /// current interval, but are defined in the Clobbers interval, mark them
375 /// used with an unknown definition value.
376 void LiveInterval::MergeInClobberRanges(const LiveInterval &Clobbers) {
377 if (Clobbers.begin() == Clobbers.end()) return;
379 // Find a value # to use for the clobber ranges. If there is already a value#
380 // for unknown values, use it.
381 // FIXME: Use a single sentinal number for these!
382 unsigned ClobberValNo = getNextValue(~0U, 0);
384 iterator IP = begin();
385 for (const_iterator I = Clobbers.begin(), E = Clobbers.end(); I != E; ++I) {
386 unsigned Start = I->start, End = I->end;
387 IP = std::upper_bound(IP, end(), Start);
389 // If the start of this range overlaps with an existing liverange, trim it.
390 if (IP != begin() && IP[-1].end > Start) {
392 // Trimmed away the whole range?
393 if (Start >= End) continue;
395 // If the end of this range overlaps with an existing liverange, trim it.
396 if (IP != end() && End > IP->start) {
398 // If this trimmed away the whole range, ignore it.
399 if (Start == End) continue;
402 // Insert the clobber interval.
403 IP = addRangeFrom(LiveRange(Start, End, ClobberValNo), IP);
407 /// MergeValueNumberInto - This method is called when two value nubmers
408 /// are found to be equivalent. This eliminates V1, replacing all
409 /// LiveRanges with the V1 value number with the V2 value number. This can
410 /// cause merging of V1/V2 values numbers and compaction of the value space.
411 void LiveInterval::MergeValueNumberInto(unsigned V1, unsigned V2) {
412 assert(V1 != V2 && "Identical value#'s are always equivalent!");
414 // This code actually merges the (numerically) larger value number into the
415 // smaller value number, which is likely to allow us to compactify the value
416 // space. The only thing we have to be careful of is to preserve the
417 // instruction that defines the result value.
419 // Make sure V2 is smaller than V1.
421 setValueNumberInfo(V1, getValNumInfo(V2));
425 // Merge V1 live ranges into V2.
426 for (iterator I = begin(); I != end(); ) {
428 if (LR->ValId != V1) continue; // Not a V1 LiveRange.
430 // Okay, we found a V1 live range. If it had a previous, touching, V2 live
433 iterator Prev = LR-1;
434 if (Prev->ValId == V2 && Prev->end == LR->start) {
437 // Erase this live-range.
444 // Okay, now we have a V1 or V2 live range that is maximally merged forward.
445 // Ensure that it is a V2 live-range.
448 // If we can merge it into later V2 live ranges, do so now. We ignore any
449 // following V1 live ranges, as they will be merged in subsequent iterations
452 if (I->start == LR->end && I->ValId == V2) {
460 // Now that V1 is dead, remove it. If it is the largest value number, just
461 // nuke it (and any other deleted values neighboring it), otherwise mark it as
462 // ~1U so it can be nuked later.
463 if (V1 == getNumValNums()-1) {
465 ValueNumberInfo.pop_back();
466 } while (ValueNumberInfo.back().first == ~1U);
468 ValueNumberInfo[V1].first = ~1U;
472 unsigned LiveInterval::getSize() const {
474 for (const_iterator I = begin(), E = end(); I != E; ++I)
475 Sum += I->end - I->start;
479 std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
480 return os << '[' << LR.start << ',' << LR.end << ':' << LR.ValId << ")";
483 void LiveRange::dump() const {
484 cerr << *this << "\n";
487 void LiveInterval::print(std::ostream &OS, const MRegisterInfo *MRI) const {
488 if (MRI && MRegisterInfo::isPhysicalRegister(reg))
489 OS << MRI->getName(reg);
499 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
500 E = ranges.end(); I != E; ++I)
504 // Print value number info.
505 if (getNumValNums()) {
507 for (unsigned i = 0; i != getNumValNums(); ++i) {
510 if (ValueNumberInfo[i].first == ~0U) {
513 OS << ValueNumberInfo[i].first;
519 void LiveInterval::dump() const {
520 cerr << *this << "\n";
524 void LiveRange::print(std::ostream &os) const {