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/Target/MRegisterInfo.h"
29 // An example for liveAt():
31 // this = [1,4), liveAt(0) will return false. The instruction defining this
32 // spans slots [0,3]. The interval belongs to an spilled definition of the
33 // variable it represents. This is because slot 1 is used (def slot) and spans
34 // up to slot 3 (store slot).
36 bool LiveInterval::liveAt(unsigned I) const {
37 Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
39 if (r == ranges.begin())
43 return r->contains(I);
46 // overlaps - Return true if the intersection of the two live intervals is
49 // An example for overlaps():
53 // 8: C = A + B ;; last use of A
55 // The live intervals should look like:
61 // A->overlaps(C) should return false since we want to be able to join
64 bool LiveInterval::overlapsFrom(const LiveInterval& other,
65 const_iterator StartPos) const {
66 const_iterator i = begin();
67 const_iterator ie = end();
68 const_iterator j = StartPos;
69 const_iterator je = other.end();
71 assert((StartPos->start <= i->start || StartPos == other.begin()) &&
72 StartPos != other.end() && "Bogus start position hint!");
74 if (i->start < j->start) {
75 i = std::upper_bound(i, ie, j->start);
76 if (i != ranges.begin()) --i;
77 } else if (j->start < i->start) {
79 if (StartPos != other.end() && StartPos->start <= i->start) {
80 assert(StartPos < other.end() && i < end());
81 j = std::upper_bound(j, je, i->start);
82 if (j != other.ranges.begin()) --j;
88 if (j == je) return false;
91 if (i->start > j->start) {
96 if (i->end > j->start)
104 /// NontrivialOverlap - Check to see if the two live ranges specified by i and j
105 /// overlap. If so, check to see if they have value numbers that are not
106 /// iIdx/jIdx respectively. If both conditions are true, return true.
107 static inline bool NontrivialOverlap(LiveInterval::Ranges::const_iterator i,
108 LiveInterval::Ranges::const_iterator j,
109 unsigned iIdx, unsigned jIdx) {
110 if (i->start == j->start) {
111 // If this is not the allowed value merge, we cannot join.
112 if (i->ValId != iIdx || j->ValId != jIdx)
114 } else if (i->start < j->start) {
115 if (i->end > j->start && i->ValId != iIdx || j->ValId != jIdx) {
119 if (j->end > i->start &&
120 i->ValId != iIdx || j->ValId != jIdx)
127 /// joinable - Two intervals are joinable if the either don't overlap at all
128 /// or if the destination of the copy is a single assignment value, and it
129 /// only overlaps with one value in the source interval.
130 bool LiveInterval::joinable(const LiveInterval &other, unsigned CopyIdx) const {
131 const LiveRange *SourceLR = other.getLiveRangeContaining(CopyIdx-1);
132 const LiveRange *DestLR = getLiveRangeContaining(CopyIdx);
133 assert(SourceLR && DestLR && "Not joining due to a copy?");
134 unsigned OtherValIdx = SourceLR->ValId;
135 unsigned ThisValIdx = DestLR->ValId;
137 Ranges::const_iterator i = ranges.begin();
138 Ranges::const_iterator ie = ranges.end();
139 Ranges::const_iterator j = other.ranges.begin();
140 Ranges::const_iterator je = other.ranges.end();
142 if (i->start < j->start) {
143 i = std::upper_bound(i, ie, j->start);
144 if (i != ranges.begin()) --i;
145 } else if (j->start < i->start) {
146 j = std::upper_bound(j, je, i->start);
147 if (j != other.ranges.begin()) --j;
150 while (i != ie && j != je) {
151 if (NontrivialOverlap(i, j, ThisValIdx, OtherValIdx))
164 /// extendIntervalEndTo - This method is used when we want to extend the range
165 /// specified by I to end at the specified endpoint. To do this, we should
166 /// merge and eliminate all ranges that this will overlap with. The iterator is
168 void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) {
169 assert(I != ranges.end() && "Not a valid interval!");
170 unsigned ValId = I->ValId;
172 // Search for the first interval that we can't merge with.
173 Ranges::iterator MergeTo = next(I);
174 for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo) {
175 assert(MergeTo->ValId == ValId && "Cannot merge with differing values!");
178 // If NewEnd was in the middle of an interval, make sure to get its endpoint.
179 I->end = std::max(NewEnd, prior(MergeTo)->end);
181 // Erase any dead ranges
182 ranges.erase(next(I), MergeTo);
186 /// extendIntervalStartTo - This method is used when we want to extend the range
187 /// specified by I to start at the specified endpoint. To do this, we should
188 /// merge and eliminate all ranges that this will overlap with.
189 LiveInterval::Ranges::iterator
190 LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) {
191 assert(I != ranges.end() && "Not a valid interval!");
192 unsigned ValId = I->ValId;
194 // Search for the first interval that we can't merge with.
195 Ranges::iterator MergeTo = I;
197 if (MergeTo == ranges.begin()) {
199 ranges.erase(MergeTo, I);
202 assert(MergeTo->ValId == ValId && "Cannot merge with differing values!");
204 } while (NewStart <= MergeTo->start);
206 // If we start in the middle of another interval, just delete a range and
207 // extend that interval.
208 if (MergeTo->end >= NewStart && MergeTo->ValId == ValId) {
209 MergeTo->end = I->end;
211 // Otherwise, extend the interval right after.
213 MergeTo->start = NewStart;
214 MergeTo->end = I->end;
217 ranges.erase(next(MergeTo), next(I));
221 LiveInterval::Ranges::iterator
222 LiveInterval::addRangeFrom(LiveRange LR, Ranges::iterator From) {
223 unsigned Start = LR.start, End = LR.end;
224 Ranges::iterator it = std::upper_bound(From, ranges.end(), Start);
226 // If the inserted interval starts in the middle or right at the end of
227 // another interval, just extend that interval to contain the range of LR.
228 if (it != ranges.begin()) {
229 Ranges::iterator B = prior(it);
230 if (LR.ValId == B->ValId) {
231 if (B->start <= Start && B->end >= Start) {
232 extendIntervalEndTo(B, End);
236 // Check to make sure that we are not overlapping two live ranges with
237 // different ValId's.
238 assert(B->end <= Start &&
239 "Cannot overlap two LiveRanges with differing ValID's"
240 " (did you def the same reg twice in a MachineInstr?)");
244 // Otherwise, if this range ends in the middle of, or right next to, another
245 // interval, merge it into that interval.
246 if (it != ranges.end())
247 if (LR.ValId == it->ValId) {
248 if (it->start <= End) {
249 it = extendIntervalStartTo(it, Start);
251 // If LR is a complete superset of an interval, we may need to grow its
254 extendIntervalEndTo(it, End);
258 // Check to make sure that we are not overlapping two live ranges with
259 // different ValId's.
260 assert(it->start >= End &&
261 "Cannot overlap two LiveRanges with differing ValID's");
264 // Otherwise, this is just a new range that doesn't interact with anything.
266 return ranges.insert(it, LR);
270 /// removeRange - Remove the specified range from this interval. Note that
271 /// the range must already be in this interval in its entirety.
272 void LiveInterval::removeRange(unsigned Start, unsigned End) {
273 // Find the LiveRange containing this span.
274 Ranges::iterator I = std::upper_bound(ranges.begin(), ranges.end(), Start);
275 assert(I != ranges.begin() && "Range is not in interval!");
277 assert(I->contains(Start) && I->contains(End-1) &&
278 "Range is not entirely in interval!");
280 // If the span we are removing is at the start of the LiveRange, adjust it.
281 if (I->start == Start) {
283 ranges.erase(I); // Removed the whole LiveRange.
289 // Otherwise if the span we are removing is at the end of the LiveRange,
290 // adjust the other way.
296 // Otherwise, we are splitting the LiveRange into two pieces.
297 unsigned OldEnd = I->end;
298 I->end = Start; // Trim the old interval.
300 // Insert the new one.
301 ranges.insert(next(I), LiveRange(End, OldEnd, I->ValId));
304 /// getLiveRangeContaining - Return the live range that contains the
305 /// specified index, or null if there is none.
306 const LiveRange *LiveInterval::getLiveRangeContaining(unsigned Idx) const {
307 Ranges::const_iterator It = std::upper_bound(ranges.begin(),ranges.end(),Idx);
308 if (It != ranges.begin()) {
309 const LiveRange &LR = *prior(It);
310 if (LR.contains(Idx))
319 /// join - Join two live intervals (this, and other) together. This operation
320 /// is the result of a copy instruction in the source program, that occurs at
321 /// index 'CopyIdx' that copies from 'Other' to 'this'.
322 void LiveInterval::join(LiveInterval &Other, unsigned CopyIdx) {
323 const LiveRange *SourceLR = Other.getLiveRangeContaining(CopyIdx-1);
324 const LiveRange *DestLR = getLiveRangeContaining(CopyIdx);
325 assert(SourceLR && DestLR && "Not joining due to a copy?");
326 unsigned MergedSrcValIdx = SourceLR->ValId;
327 unsigned MergedDstValIdx = DestLR->ValId;
329 // Try to do the least amount of work possible. In particular, if there are
330 // more liverange chunks in the other set than there are in the 'this' set,
331 // swap sets to merge the fewest chunks in possible.
332 if (Other.ranges.size() > ranges.size()) {
333 std::swap(MergedSrcValIdx, MergedDstValIdx);
334 std::swap(ranges, Other.ranges);
335 std::swap(NumValues, Other.NumValues);
338 // Join the ranges of other into the ranges of this interval.
339 Ranges::iterator InsertPos = ranges.begin();
340 std::map<unsigned, unsigned> Dst2SrcIdxMap;
341 for (Ranges::iterator I = Other.ranges.begin(),
342 E = Other.ranges.end(); I != E; ++I) {
343 // Map the ValId in the other live range to the current live range.
344 if (I->ValId == MergedSrcValIdx)
345 I->ValId = MergedDstValIdx;
347 unsigned &NV = Dst2SrcIdxMap[I->ValId];
348 if (NV == 0) NV = getNextValue();
352 InsertPos = addRangeFrom(*I, InsertPos);
355 weight += Other.weight;
358 std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
359 return os << '[' << LR.start << ',' << LR.end << ':' << LR.ValId << ")";
362 void LiveRange::dump() const {
363 std::cerr << *this << "\n";
366 void LiveInterval::print(std::ostream &OS, const MRegisterInfo *MRI) const {
367 if (MRI && MRegisterInfo::isPhysicalRegister(reg))
368 OS << MRI->getName(reg);
378 for (LiveInterval::Ranges::const_iterator I = ranges.begin(),
379 E = ranges.end(); I != E; ++I)
384 void LiveInterval::dump() const {
385 std::cerr << *this << "\n";