LiveIntervalAnalysis.cpp revision a2f6a408dc6616713b2e63425cf8cf7792c66c80 
1//===-- LiveIntervals.cpp - Live Interval Analysis ------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
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.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the LiveInterval analysis pass which is used
11// by the Linear Scan Register allocator. This pass linearizes the
12// basic blocks of the function in DFS order and uses the
13// LiveVariables pass to conservatively compute live intervals for
14// each virtual and physical register.
15//
16//===----------------------------------------------------------------------===//
17
18#define DEBUG_TYPE "liveintervals"
19#include "llvm/Analysis/LoopInfo.h"
20#include "llvm/CodeGen/LiveVariables.h"
21#include "llvm/CodeGen/MachineFrameInfo.h"
22#include "llvm/CodeGen/MachineInstr.h"
23#include "llvm/CodeGen/Passes.h"
24#include "llvm/CodeGen/SSARegMap.h"
25#include "llvm/Target/MRegisterInfo.h"
26#include "llvm/Target/TargetInstrInfo.h"
27#include "llvm/Target/TargetMachine.h"
28#include "llvm/Support/CFG.h"
29#include "Support/CommandLine.h"
30#include "Support/Debug.h"
31#include "Support/Statistic.h"
32#include "Support/STLExtras.h"
33#include "LiveIntervals.h"
34#include <cmath>
35#include <iostream>
36#include <limits>
37
38using namespace llvm;
39
40namespace {
41    RegisterAnalysis<LiveIntervals> X("liveintervals",
42                                      "Live Interval Analysis");
43
44    Statistic<> numIntervals
45    ("liveintervals", "Number of original intervals");
46
47    Statistic<> numIntervalsAfter
48    ("liveintervals", "Number of intervals after coalescing");
49
50    Statistic<> numJoins
51    ("liveintervals", "Number of interval joins performed");
52
53    Statistic<> numPeep
54    ("liveintervals", "Number of identity moves eliminated after coalescing");
55
56    Statistic<> numFolded
57    ("liveintervals", "Number of loads/stores folded into instructions");
58
59    cl::opt<bool>
60    join("join-liveintervals",
61         cl::desc("Join compatible live intervals"),
62         cl::init(true));
63};
64
65void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const
66{
67    AU.addPreserved<LiveVariables>();
68    AU.addRequired<LiveVariables>();
69    AU.addPreservedID(PHIEliminationID);
70    AU.addRequiredID(PHIEliminationID);
71    AU.addRequiredID(TwoAddressInstructionPassID);
72    AU.addRequired<LoopInfo>();
73    MachineFunctionPass::getAnalysisUsage(AU);
74}
75
76void LiveIntervals::releaseMemory()
77{
78    mbbi2mbbMap_.clear();
79    mi2iMap_.clear();
80    i2miMap_.clear();
81    r2iMap_.clear();
82    r2rMap_.clear();
83    intervals_.clear();
84}
85
86
87/// runOnMachineFunction - Register allocate the whole function
88///
89bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
90    mf_ = &fn;
91    tm_ = &fn.getTarget();
92    mri_ = tm_->getRegisterInfo();
93    lv_ = &getAnalysis<LiveVariables>();
94
95    // number MachineInstrs
96    unsigned miIndex = 0;
97    for (MachineFunction::iterator mbb = mf_->begin(), mbbEnd = mf_->end();
98         mbb != mbbEnd; ++mbb) {
99        const std::pair<MachineBasicBlock*, unsigned>& entry =
100            lv_->getMachineBasicBlockInfo(mbb);
101        bool inserted = mbbi2mbbMap_.insert(std::make_pair(entry.second,
102                                                           entry.first)).second;
103        assert(inserted && "multiple index -> MachineBasicBlock");
104
105        for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
106             mi != miEnd; ++mi) {
107            inserted = mi2iMap_.insert(std::make_pair(mi, miIndex)).second;
108            assert(inserted && "multiple MachineInstr -> index mappings");
109            i2miMap_.push_back(mi);
110            miIndex += InstrSlots::NUM;
111        }
112    }
113
114    computeIntervals();
115
116    numIntervals += intervals_.size();
117
118    // join intervals if requested
119    if (join) joinIntervals();
120
121    numIntervalsAfter += intervals_.size();
122
123    // perform a final pass over the instructions and compute spill
124    // weights, coalesce virtual registers and remove identity moves
125    const LoopInfo& loopInfo = getAnalysis<LoopInfo>();
126    const TargetInstrInfo& tii = tm_->getInstrInfo();
127
128    for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
129         mbbi != mbbe; ++mbbi) {
130        MachineBasicBlock* mbb = mbbi;
131        unsigned loopDepth = loopInfo.getLoopDepth(mbb->getBasicBlock());
132
133        for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
134             mii != mie; ) {
135            for (unsigned i = 0; i < mii->getNumOperands(); ++i) {
136                const MachineOperand& mop = mii->getOperand(i);
137                if (mop.isRegister()) {
138                    // replace register with representative register
139                    unsigned reg = rep(mop.getReg());
140                    mii->SetMachineOperandReg(i, reg);
141
142                    if (MRegisterInfo::isVirtualRegister(reg)) {
143                        Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
144                        assert(r2iit != r2iMap_.end());
145                        r2iit->second->weight += pow(10.0F, loopDepth);
146                    }
147                }
148            }
149
150            // if the move is now an identity move delete it
151            unsigned srcReg, dstReg;
152            if (tii.isMoveInstr(*mii, srcReg, dstReg) && srcReg == dstReg) {
153                // remove index -> MachineInstr and
154                // MachineInstr -> index mappings
155                Mi2IndexMap::iterator mi2i = mi2iMap_.find(mii);
156                if (mi2i != mi2iMap_.end()) {
157                    i2miMap_[mi2i->second/InstrSlots::NUM] = 0;
158                    mi2iMap_.erase(mi2i);
159                }
160                mii = mbbi->erase(mii);
161                ++numPeep;
162            }
163            else
164                ++mii;
165        }
166    }
167
168    intervals_.sort(StartPointComp());
169    DEBUG(std::cerr << "********** INTERVALS **********\n");
170    DEBUG(std::copy(intervals_.begin(), intervals_.end(),
171                    std::ostream_iterator<Interval>(std::cerr, "\n")));
172    DEBUG(std::cerr << "********** MACHINEINSTRS **********\n");
173    DEBUG(
174        for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
175             mbbi != mbbe; ++mbbi) {
176            std::cerr << mbbi->getBasicBlock()->getName() << ":\n";
177            for (MachineBasicBlock::iterator mii = mbbi->begin(),
178                     mie = mbbi->end(); mii != mie; ++mii) {
179                std::cerr << getInstructionIndex(mii) << '\t';
180                mii->print(std::cerr, *tm_);
181            }
182        });
183
184    return true;
185}
186
187void LiveIntervals::updateSpilledInterval(Interval& li, int slot)
188{
189    assert(li.weight != std::numeric_limits<float>::infinity() &&
190           "attempt to spill already spilled interval!");
191    Interval::Ranges oldRanges;
192    swap(oldRanges, li.ranges);
193
194    DEBUG(std::cerr << "\t\t\t\tupdating interval: " << li);
195
196    for (Interval::Ranges::iterator i = oldRanges.begin(), e = oldRanges.end();
197         i != e; ++i) {
198        unsigned index = getBaseIndex(i->first);
199        unsigned end = getBaseIndex(i->second-1) + InstrSlots::NUM;
200        for (; index < end; index += InstrSlots::NUM) {
201            // skip deleted instructions
202            while (!getInstructionFromIndex(index)) index += InstrSlots::NUM;
203            MachineBasicBlock::iterator mi = getInstructionFromIndex(index);
204
205            for (unsigned i = 0; i < mi->getNumOperands(); ++i) {
206                MachineOperand& mop = mi->getOperand(i);
207                if (mop.isRegister() && mop.getReg() == li.reg) {
208                    // This is tricky. We need to add information in
209                    // the interval about the spill code so we have to
210                    // use our extra load/store slots.
211                    //
212                    // If we have a use we are going to have a load so
213                    // we start the interval from the load slot
214                    // onwards. Otherwise we start from the def slot.
215                    unsigned start = (mop.isUse() ?
216                                      getLoadIndex(index) :
217                                      getDefIndex(index));
218                    // If we have a def we are going to have a store
219                    // right after it so we end the interval after the
220                    // use of the next instruction. Otherwise we end
221                    // after the use of this instruction.
222                    unsigned end = 1 + (mop.isDef() ?
223                                        getUseIndex(index+InstrSlots::NUM) :
224                                        getUseIndex(index));
225                    li.addRange(start, end);
226                }
227            }
228        }
229    }
230    // the new spill weight is now infinity as it cannot be spilled again
231    li.weight = std::numeric_limits<float>::infinity();
232    DEBUG(std::cerr << '\n');
233    DEBUG(std::cerr << "\t\t\t\tupdated interval: " << li << '\n');
234}
235
236void LiveIntervals::printRegName(unsigned reg) const
237{
238    if (MRegisterInfo::isPhysicalRegister(reg))
239        std::cerr << mri_->getName(reg);
240    else
241        std::cerr << "%reg" << reg;
242}
243
244void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
245                                             MachineBasicBlock::iterator mi,
246                                             unsigned reg)
247{
248    DEBUG(std::cerr << "\t\tregister: "; printRegName(reg));
249    LiveVariables::VarInfo& vi = lv_->getVarInfo(reg);
250
251    Interval* interval = 0;
252    Reg2IntervalMap::iterator r2iit = r2iMap_.lower_bound(reg);
253    if (r2iit == r2iMap_.end() || r2iit->first != reg) {
254        // add new interval
255        intervals_.push_back(Interval(reg));
256        // update interval index for this register
257        r2iMap_.insert(r2iit, std::make_pair(reg, --intervals_.end()));
258        interval = &intervals_.back();
259
260        // iterate over all of the blocks that the variable is
261        // completely live in, adding them to the live
262        // interval. obviously we only need to do this once.
263        for (unsigned i = 0, e = vi.AliveBlocks.size(); i != e; ++i) {
264            if (vi.AliveBlocks[i]) {
265                MachineBasicBlock* mbb = lv_->getIndexMachineBasicBlock(i);
266                if (!mbb->empty()) {
267                    interval->addRange(
268                        getInstructionIndex(&mbb->front()),
269                        getInstructionIndex(&mbb->back()) + InstrSlots::NUM);
270                }
271            }
272        }
273    }
274    else {
275        interval = &*r2iit->second;
276    }
277
278    unsigned baseIndex = getInstructionIndex(mi);
279
280    bool killedInDefiningBasicBlock = false;
281    for (int i = 0, e = vi.Kills.size(); i != e; ++i) {
282        MachineBasicBlock* killerBlock = vi.Kills[i].first;
283        MachineInstr* killerInstr = vi.Kills[i].second;
284        unsigned start = (mbb == killerBlock ?
285                          getDefIndex(baseIndex) :
286                          getInstructionIndex(&killerBlock->front()));
287        unsigned end = (killerInstr == mi ?
288                         // dead
289                        start + 1 :
290                        // killed
291                        getUseIndex(getInstructionIndex(killerInstr))+1);
292        // we do not want to add invalid ranges. these can happen when
293        // a variable has its latest use and is redefined later on in
294        // the same basic block (common with variables introduced by
295        // PHI elimination)
296        if (start < end) {
297            killedInDefiningBasicBlock |= mbb == killerBlock;
298            interval->addRange(start, end);
299        }
300    }
301
302    if (!killedInDefiningBasicBlock) {
303        unsigned end = getInstructionIndex(&mbb->back()) + InstrSlots::NUM;
304        interval->addRange(getDefIndex(baseIndex), end);
305    }
306    DEBUG(std::cerr << '\n');
307}
308
309void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock* mbb,
310                                              MachineBasicBlock::iterator mi,
311                                              unsigned reg)
312{
313    DEBUG(std::cerr << "\t\tregister: "; printRegName(reg));
314    typedef LiveVariables::killed_iterator KillIter;
315
316    MachineBasicBlock::iterator e = mbb->end();
317    unsigned baseIndex = getInstructionIndex(mi);
318    unsigned start = getDefIndex(baseIndex);
319    unsigned end = start;
320
321    // a variable can be dead by the instruction defining it
322    for (KillIter ki = lv_->dead_begin(mi), ke = lv_->dead_end(mi);
323         ki != ke; ++ki) {
324        if (reg == ki->second) {
325            DEBUG(std::cerr << " dead");
326            end = getDefIndex(start) + 1;
327            goto exit;
328        }
329    }
330
331    // a variable can only be killed by subsequent instructions
332    do {
333        ++mi;
334        baseIndex += InstrSlots::NUM;
335        for (KillIter ki = lv_->killed_begin(mi), ke = lv_->killed_end(mi);
336             ki != ke; ++ki) {
337            if (reg == ki->second) {
338                DEBUG(std::cerr << " killed");
339                end = getUseIndex(baseIndex) + 1;
340                goto exit;
341            }
342        }
343    } while (mi != e);
344
345exit:
346    assert(start < end && "did not find end of interval?");
347
348    Reg2IntervalMap::iterator r2iit = r2iMap_.lower_bound(reg);
349    if (r2iit != r2iMap_.end() && r2iit->first == reg) {
350        r2iit->second->addRange(start, end);
351    }
352    else {
353        intervals_.push_back(Interval(reg));
354        // update interval index for this register
355        r2iMap_.insert(r2iit, std::make_pair(reg, --intervals_.end()));
356        intervals_.back().addRange(start, end);
357    }
358    DEBUG(std::cerr << '\n');
359}
360
361void LiveIntervals::handleRegisterDef(MachineBasicBlock* mbb,
362                                      MachineBasicBlock::iterator mi,
363                                      unsigned reg)
364{
365    if (MRegisterInfo::isPhysicalRegister(reg)) {
366        if (lv_->getAllocatablePhysicalRegisters()[reg]) {
367            handlePhysicalRegisterDef(mbb, mi, reg);
368            for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
369                handlePhysicalRegisterDef(mbb, mi, *as);
370        }
371    }
372    else {
373        handleVirtualRegisterDef(mbb, mi, reg);
374    }
375}
376
377unsigned LiveIntervals::getInstructionIndex(MachineInstr* instr) const
378{
379    Mi2IndexMap::const_iterator it = mi2iMap_.find(instr);
380    return (it == mi2iMap_.end() ?
381            std::numeric_limits<unsigned>::max() :
382            it->second);
383}
384
385MachineInstr* LiveIntervals::getInstructionFromIndex(unsigned index) const
386{
387    index /= InstrSlots::NUM; // convert index to vector index
388    assert(index < i2miMap_.size() &&
389           "index does not correspond to an instruction");
390    return i2miMap_[index];
391}
392
393/// computeIntervals - computes the live intervals for virtual
394/// registers. for some ordering of the machine instructions [1,N] a
395/// live interval is an interval [i, j) where 1 <= i <= j < N for
396/// which a variable is live
397void LiveIntervals::computeIntervals()
398{
399    DEBUG(std::cerr << "********** COMPUTING LIVE INTERVALS **********\n");
400    DEBUG(std::cerr << "********** Function: "
401          << mf_->getFunction()->getName() << '\n');
402
403    for (MbbIndex2MbbMap::iterator
404             it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
405         it != itEnd; ++it) {
406        MachineBasicBlock* mbb = it->second;
407        DEBUG(std::cerr << mbb->getBasicBlock()->getName() << ":\n");
408
409        for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
410             mi != miEnd; ++mi) {
411            const TargetInstrDescriptor& tid =
412                tm_->getInstrInfo().get(mi->getOpcode());
413            DEBUG(std::cerr << getInstructionIndex(mi) << "\t";
414                  mi->print(std::cerr, *tm_));
415
416            // handle implicit defs
417            for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
418                handleRegisterDef(mbb, mi, *id);
419
420            // handle explicit defs
421            for (int i = mi->getNumOperands() - 1; i >= 0; --i) {
422                MachineOperand& mop = mi->getOperand(i);
423                // handle register defs - build intervals
424                if (mop.isRegister() && mop.isDef())
425                    handleRegisterDef(mbb, mi, mop.getReg());
426            }
427        }
428    }
429}
430
431unsigned LiveIntervals::rep(unsigned reg)
432{
433    Reg2RegMap::iterator it = r2rMap_.find(reg);
434    if (it != r2rMap_.end())
435        return it->second = rep(it->second);
436    return reg;
437}
438
439void LiveIntervals::joinIntervals()
440{
441    DEBUG(std::cerr << "********** JOINING INTERVALS ***********\n");
442
443    const TargetInstrInfo& tii = tm_->getInstrInfo();
444
445    for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
446         mbbi != mbbe; ++mbbi) {
447        MachineBasicBlock* mbb = mbbi;
448        DEBUG(std::cerr << mbb->getBasicBlock()->getName() << ":\n");
449
450        for (MachineBasicBlock::iterator mi = mbb->begin(), mie = mbb->end();
451             mi != mie; ++mi) {
452            const TargetInstrDescriptor& tid =
453                tm_->getInstrInfo().get(mi->getOpcode());
454            DEBUG(std::cerr << getInstructionIndex(mi) << '\t';
455                  mi->print(std::cerr, *tm_););
456
457            // we only join virtual registers with allocatable
458            // physical registers since we do not have liveness information
459            // on not allocatable physical registers
460            unsigned regA, regB;
461            if (tii.isMoveInstr(*mi, regA, regB) &&
462                (MRegisterInfo::isVirtualRegister(regA) ||
463                 lv_->getAllocatablePhysicalRegisters()[regA]) &&
464                (MRegisterInfo::isVirtualRegister(regB) ||
465                 lv_->getAllocatablePhysicalRegisters()[regB])) {
466
467                // get representative registers
468                regA = rep(regA);
469                regB = rep(regB);
470
471                // if they are already joined we continue
472                if (regA == regB)
473                    continue;
474
475                Reg2IntervalMap::iterator r2iA = r2iMap_.find(regA);
476                assert(r2iA != r2iMap_.end());
477                Reg2IntervalMap::iterator r2iB = r2iMap_.find(regB);
478                assert(r2iB != r2iMap_.end());
479
480                Intervals::iterator intA = r2iA->second;
481                Intervals::iterator intB = r2iB->second;
482
483                // both A and B are virtual registers
484                if (MRegisterInfo::isVirtualRegister(intA->reg) &&
485                    MRegisterInfo::isVirtualRegister(intB->reg)) {
486
487                    const TargetRegisterClass *rcA, *rcB;
488                    rcA = mf_->getSSARegMap()->getRegClass(intA->reg);
489                    rcB = mf_->getSSARegMap()->getRegClass(intB->reg);
490                    assert(rcA == rcB && "registers must be of the same class");
491
492                    // if their intervals do not overlap we join them
493                    if (!intB->overlaps(*intA)) {
494                        intA->join(*intB);
495                        r2iB->second = r2iA->second;
496                        r2rMap_.insert(std::make_pair(intB->reg, intA->reg));
497                        intervals_.erase(intB);
498                    }
499                }
500                else if (MRegisterInfo::isPhysicalRegister(intA->reg) ^
501                         MRegisterInfo::isPhysicalRegister(intB->reg)) {
502                    if (MRegisterInfo::isPhysicalRegister(intB->reg)) {
503                        std::swap(regA, regB);
504                        std::swap(intA, intB);
505                        std::swap(r2iA, r2iB);
506                    }
507
508                    assert(MRegisterInfo::isPhysicalRegister(intA->reg) &&
509                           MRegisterInfo::isVirtualRegister(intB->reg) &&
510                           "A must be physical and B must be virtual");
511
512                    if (!intA->overlaps(*intB) &&
513                         !overlapsAliases(*intA, *intB)) {
514                        intA->join(*intB);
515                        r2iB->second = r2iA->second;
516                        r2rMap_.insert(std::make_pair(intB->reg, intA->reg));
517                        intervals_.erase(intB);
518                    }
519                }
520            }
521        }
522    }
523}
524
525bool LiveIntervals::overlapsAliases(const Interval& lhs,
526                                    const Interval& rhs) const
527{
528    assert(MRegisterInfo::isPhysicalRegister(lhs.reg) &&
529           "first interval must describe a physical register");
530
531    for (const unsigned* as = mri_->getAliasSet(lhs.reg); *as; ++as) {
532        Reg2IntervalMap::const_iterator r2i = r2iMap_.find(*as);
533        assert(r2i != r2iMap_.end() && "alias does not have interval?");
534        if (rhs.overlaps(*r2i->second))
535            return true;
536    }
537
538    return false;
539}
540
541LiveIntervals::Interval::Interval(unsigned r)
542    : reg(r),
543      weight((MRegisterInfo::isPhysicalRegister(r) ?
544              std::numeric_limits<float>::infinity() : 0.0F))
545{
546
547}
548
549bool LiveIntervals::Interval::spilled() const
550{
551    return (weight == std::numeric_limits<float>::infinity() &&
552            MRegisterInfo::isVirtualRegister(reg));
553}
554
555// An example for liveAt():
556//
557// this = [1,4), liveAt(0) will return false. The instruction defining
558// this spans slots [0,3]. The interval belongs to an spilled
559// definition of the variable it represents. This is because slot 1 is
560// used (def slot) and spans up to slot 3 (store slot).
561//
562bool LiveIntervals::Interval::liveAt(unsigned index) const
563{
564    Range dummy(index, index+1);
565    Ranges::const_iterator r = std::upper_bound(ranges.begin(),
566                                                ranges.end(),
567                                                dummy);
568    if (r == ranges.begin())
569        return false;
570
571    --r;
572    return index >= r->first && index < r->second;
573}
574
575// An example for overlaps():
576//
577// 0: A = ...
578// 4: B = ...
579// 8: C = A + B ;; last use of A
580//
581// The live intervals should look like:
582//
583// A = [3, 11)
584// B = [7, x)
585// C = [11, y)
586//
587// A->overlaps(C) should return false since we want to be able to join
588// A and C.
589bool LiveIntervals::Interval::overlaps(const Interval& other) const
590{
591    Ranges::const_iterator i = ranges.begin();
592    Ranges::const_iterator ie = ranges.end();
593    Ranges::const_iterator j = other.ranges.begin();
594    Ranges::const_iterator je = other.ranges.end();
595    if (i->first < j->first) {
596        i = std::upper_bound(i, ie, *j);
597        if (i != ranges.begin()) --i;
598    }
599    else if (j->first < i->first) {
600        j = std::upper_bound(j, je, *i);
601        if (j != other.ranges.begin()) --j;
602    }
603
604    while (i != ie && j != je) {
605        if (i->first == j->first) {
606            return true;
607        }
608        else {
609            if (i->first > j->first) {
610                swap(i, j);
611                swap(ie, je);
612            }
613            assert(i->first < j->first);
614
615            if (i->second > j->first) {
616                return true;
617            }
618            else {
619                ++i;
620            }
621        }
622    }
623
624    return false;
625}
626
627void LiveIntervals::Interval::addRange(unsigned start, unsigned end)
628{
629    assert(start < end && "Invalid range to add!");
630    DEBUG(std::cerr << " +[" << start << ',' << end << ")");
631    //assert(start < end && "invalid range?");
632    Range range = std::make_pair(start, end);
633    Ranges::iterator it =
634        ranges.insert(std::upper_bound(ranges.begin(), ranges.end(), range),
635                      range);
636
637    it = mergeRangesForward(it);
638    it = mergeRangesBackward(it);
639}
640
641void LiveIntervals::Interval::join(const LiveIntervals::Interval& other)
642{
643    DEBUG(std::cerr << "\t\tjoining " << *this << " with " << other << '\n');
644    Ranges::iterator cur = ranges.begin();
645
646    for (Ranges::const_iterator i = other.ranges.begin(),
647             e = other.ranges.end(); i != e; ++i) {
648        cur = ranges.insert(std::upper_bound(cur, ranges.end(), *i), *i);
649        cur = mergeRangesForward(cur);
650        cur = mergeRangesBackward(cur);
651    }
652    weight += other.weight;
653    ++numJoins;
654}
655
656LiveIntervals::Interval::Ranges::iterator
657LiveIntervals::Interval::mergeRangesForward(Ranges::iterator it)
658{
659    Ranges::iterator n;
660    while ((n = next(it)) != ranges.end()) {
661        if (n->first > it->second)
662            break;
663        it->second = std::max(it->second, n->second);
664        n = ranges.erase(n);
665    }
666    return it;
667}
668
669LiveIntervals::Interval::Ranges::iterator
670LiveIntervals::Interval::mergeRangesBackward(Ranges::iterator it)
671{
672    while (it != ranges.begin()) {
673        Ranges::iterator p = prior(it);
674        if (it->first > p->second)
675            break;
676
677        it->first = std::min(it->first, p->first);
678        it->second = std::max(it->second, p->second);
679        it = ranges.erase(p);
680    }
681
682    return it;
683}
684
685std::ostream& llvm::operator<<(std::ostream& os,
686                               const LiveIntervals::Interval& li)
687{
688    os << "%reg" << li.reg << ',' << li.weight << " = ";
689    if (li.empty())
690        return os << "EMPTY";
691    for (LiveIntervals::Interval::Ranges::const_iterator
692             i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
693        os << "[" << i->first << "," << i->second << ")";
694    }
695    return os;
696}
697