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      1 //===------ RegAllocPBQP.cpp ---- PBQP Register Allocator -------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file contains a Partitioned Boolean Quadratic Programming (PBQP) based
     11 // register allocator for LLVM. This allocator works by constructing a PBQP
     12 // problem representing the register allocation problem under consideration,
     13 // solving this using a PBQP solver, and mapping the solution back to a
     14 // register assignment. If any variables are selected for spilling then spill
     15 // code is inserted and the process repeated.
     16 //
     17 // The PBQP solver (pbqp.c) provided for this allocator uses a heuristic tuned
     18 // for register allocation. For more information on PBQP for register
     19 // allocation, see the following papers:
     20 //
     21 //   (1) Hames, L. and Scholz, B. 2006. Nearly optimal register allocation with
     22 //   PBQP. In Proceedings of the 7th Joint Modular Languages Conference
     23 //   (JMLC'06). LNCS, vol. 4228. Springer, New York, NY, USA. 346-361.
     24 //
     25 //   (2) Scholz, B., Eckstein, E. 2002. Register allocation for irregular
     26 //   architectures. In Proceedings of the Joint Conference on Languages,
     27 //   Compilers and Tools for Embedded Systems (LCTES'02), ACM Press, New York,
     28 //   NY, USA, 139-148.
     29 //
     30 //===----------------------------------------------------------------------===//
     31 
     32 #include "llvm/CodeGen/RegAllocPBQP.h"
     33 #include "RegisterCoalescer.h"
     34 #include "Spiller.h"
     35 #include "llvm/Analysis/AliasAnalysis.h"
     36 #include "llvm/CodeGen/CalcSpillWeights.h"
     37 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
     38 #include "llvm/CodeGen/LiveRangeEdit.h"
     39 #include "llvm/CodeGen/LiveStackAnalysis.h"
     40 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
     41 #include "llvm/CodeGen/MachineDominators.h"
     42 #include "llvm/CodeGen/MachineFunctionPass.h"
     43 #include "llvm/CodeGen/MachineLoopInfo.h"
     44 #include "llvm/CodeGen/MachineRegisterInfo.h"
     45 #include "llvm/CodeGen/RegAllocRegistry.h"
     46 #include "llvm/CodeGen/VirtRegMap.h"
     47 #include "llvm/IR/Module.h"
     48 #include "llvm/Support/Debug.h"
     49 #include "llvm/Support/FileSystem.h"
     50 #include "llvm/Support/raw_ostream.h"
     51 #include "llvm/Target/TargetInstrInfo.h"
     52 #include "llvm/Target/TargetMachine.h"
     53 #include <limits>
     54 #include <memory>
     55 #include <set>
     56 #include <sstream>
     57 #include <vector>
     58 
     59 using namespace llvm;
     60 
     61 #define DEBUG_TYPE "regalloc"
     62 
     63 static RegisterRegAlloc
     64 registerPBQPRepAlloc("pbqp", "PBQP register allocator",
     65                        createDefaultPBQPRegisterAllocator);
     66 
     67 static cl::opt<bool>
     68 pbqpCoalescing("pbqp-coalescing",
     69                 cl::desc("Attempt coalescing during PBQP register allocation."),
     70                 cl::init(false), cl::Hidden);
     71 
     72 #ifndef NDEBUG
     73 static cl::opt<bool>
     74 pbqpDumpGraphs("pbqp-dump-graphs",
     75                cl::desc("Dump graphs for each function/round in the compilation unit."),
     76                cl::init(false), cl::Hidden);
     77 #endif
     78 
     79 namespace {
     80 
     81 ///
     82 /// PBQP based allocators solve the register allocation problem by mapping
     83 /// register allocation problems to Partitioned Boolean Quadratic
     84 /// Programming problems.
     85 class RegAllocPBQP : public MachineFunctionPass {
     86 public:
     87 
     88   static char ID;
     89 
     90   /// Construct a PBQP register allocator.
     91   RegAllocPBQP(std::unique_ptr<PBQPBuilder> &b, char *cPassID=nullptr)
     92       : MachineFunctionPass(ID), builder(b.release()), customPassID(cPassID) {
     93     initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
     94     initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
     95     initializeLiveStacksPass(*PassRegistry::getPassRegistry());
     96     initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
     97   }
     98 
     99   /// Return the pass name.
    100   const char* getPassName() const override {
    101     return "PBQP Register Allocator";
    102   }
    103 
    104   /// PBQP analysis usage.
    105   void getAnalysisUsage(AnalysisUsage &au) const override;
    106 
    107   /// Perform register allocation
    108   bool runOnMachineFunction(MachineFunction &MF) override;
    109 
    110 private:
    111 
    112   typedef std::map<const LiveInterval*, unsigned> LI2NodeMap;
    113   typedef std::vector<const LiveInterval*> Node2LIMap;
    114   typedef std::vector<unsigned> AllowedSet;
    115   typedef std::vector<AllowedSet> AllowedSetMap;
    116   typedef std::pair<unsigned, unsigned> RegPair;
    117   typedef std::map<RegPair, PBQP::PBQPNum> CoalesceMap;
    118   typedef std::set<unsigned> RegSet;
    119 
    120   std::unique_ptr<PBQPBuilder> builder;
    121 
    122   char *customPassID;
    123 
    124   MachineFunction *mf;
    125   const TargetMachine *tm;
    126   const TargetRegisterInfo *tri;
    127   const TargetInstrInfo *tii;
    128   MachineRegisterInfo *mri;
    129   const MachineBlockFrequencyInfo *mbfi;
    130 
    131   std::unique_ptr<Spiller> spiller;
    132   LiveIntervals *lis;
    133   LiveStacks *lss;
    134   VirtRegMap *vrm;
    135 
    136   RegSet vregsToAlloc, emptyIntervalVRegs;
    137 
    138   /// \brief Finds the initial set of vreg intervals to allocate.
    139   void findVRegIntervalsToAlloc();
    140 
    141   /// \brief Given a solved PBQP problem maps this solution back to a register
    142   /// assignment.
    143   bool mapPBQPToRegAlloc(const PBQPRAProblem &problem,
    144                          const PBQP::Solution &solution);
    145 
    146   /// \brief Postprocessing before final spilling. Sets basic block "live in"
    147   /// variables.
    148   void finalizeAlloc() const;
    149 
    150 };
    151 
    152 char RegAllocPBQP::ID = 0;
    153 
    154 } // End anonymous namespace.
    155 
    156 unsigned PBQPRAProblem::getVRegForNode(PBQPRAGraph::NodeId node) const {
    157   Node2VReg::const_iterator vregItr = node2VReg.find(node);
    158   assert(vregItr != node2VReg.end() && "No vreg for node.");
    159   return vregItr->second;
    160 }
    161 
    162 PBQPRAGraph::NodeId PBQPRAProblem::getNodeForVReg(unsigned vreg) const {
    163   VReg2Node::const_iterator nodeItr = vreg2Node.find(vreg);
    164   assert(nodeItr != vreg2Node.end() && "No node for vreg.");
    165   return nodeItr->second;
    166 
    167 }
    168 
    169 const PBQPRAProblem::AllowedSet&
    170   PBQPRAProblem::getAllowedSet(unsigned vreg) const {
    171   AllowedSetMap::const_iterator allowedSetItr = allowedSets.find(vreg);
    172   assert(allowedSetItr != allowedSets.end() && "No pregs for vreg.");
    173   const AllowedSet &allowedSet = allowedSetItr->second;
    174   return allowedSet;
    175 }
    176 
    177 unsigned PBQPRAProblem::getPRegForOption(unsigned vreg, unsigned option) const {
    178   assert(isPRegOption(vreg, option) && "Not a preg option.");
    179 
    180   const AllowedSet& allowedSet = getAllowedSet(vreg);
    181   assert(option <= allowedSet.size() && "Option outside allowed set.");
    182   return allowedSet[option - 1];
    183 }
    184 
    185 PBQPRAProblem *PBQPBuilder::build(MachineFunction *mf, const LiveIntervals *lis,
    186                                   const MachineBlockFrequencyInfo *mbfi,
    187                                   const RegSet &vregs) {
    188 
    189   LiveIntervals *LIS = const_cast<LiveIntervals*>(lis);
    190   MachineRegisterInfo *mri = &mf->getRegInfo();
    191   const TargetRegisterInfo *tri = mf->getTarget().getRegisterInfo();
    192 
    193   std::unique_ptr<PBQPRAProblem> p(new PBQPRAProblem());
    194   PBQPRAGraph &g = p->getGraph();
    195   RegSet pregs;
    196 
    197   // Collect the set of preg intervals, record that they're used in the MF.
    198   for (unsigned Reg = 1, e = tri->getNumRegs(); Reg != e; ++Reg) {
    199     if (mri->def_empty(Reg))
    200       continue;
    201     pregs.insert(Reg);
    202     mri->setPhysRegUsed(Reg);
    203   }
    204 
    205   // Iterate over vregs.
    206   for (RegSet::const_iterator vregItr = vregs.begin(), vregEnd = vregs.end();
    207        vregItr != vregEnd; ++vregItr) {
    208     unsigned vreg = *vregItr;
    209     const TargetRegisterClass *trc = mri->getRegClass(vreg);
    210     LiveInterval *vregLI = &LIS->getInterval(vreg);
    211 
    212     // Record any overlaps with regmask operands.
    213     BitVector regMaskOverlaps;
    214     LIS->checkRegMaskInterference(*vregLI, regMaskOverlaps);
    215 
    216     // Compute an initial allowed set for the current vreg.
    217     typedef std::vector<unsigned> VRAllowed;
    218     VRAllowed vrAllowed;
    219     ArrayRef<MCPhysReg> rawOrder = trc->getRawAllocationOrder(*mf);
    220     for (unsigned i = 0; i != rawOrder.size(); ++i) {
    221       unsigned preg = rawOrder[i];
    222       if (mri->isReserved(preg))
    223         continue;
    224 
    225       // vregLI crosses a regmask operand that clobbers preg.
    226       if (!regMaskOverlaps.empty() && !regMaskOverlaps.test(preg))
    227         continue;
    228 
    229       // vregLI overlaps fixed regunit interference.
    230       bool Interference = false;
    231       for (MCRegUnitIterator Units(preg, tri); Units.isValid(); ++Units) {
    232         if (vregLI->overlaps(LIS->getRegUnit(*Units))) {
    233           Interference = true;
    234           break;
    235         }
    236       }
    237       if (Interference)
    238         continue;
    239 
    240       // preg is usable for this virtual register.
    241       vrAllowed.push_back(preg);
    242     }
    243 
    244     PBQP::Vector nodeCosts(vrAllowed.size() + 1, 0);
    245 
    246     PBQP::PBQPNum spillCost = (vregLI->weight != 0.0) ?
    247         vregLI->weight : std::numeric_limits<PBQP::PBQPNum>::min();
    248 
    249     addSpillCosts(nodeCosts, spillCost);
    250 
    251     // Construct the node.
    252     PBQPRAGraph::NodeId nId = g.addNode(std::move(nodeCosts));
    253 
    254     // Record the mapping and allowed set in the problem.
    255     p->recordVReg(vreg, nId, vrAllowed.begin(), vrAllowed.end());
    256 
    257   }
    258 
    259   for (RegSet::const_iterator vr1Itr = vregs.begin(), vrEnd = vregs.end();
    260          vr1Itr != vrEnd; ++vr1Itr) {
    261     unsigned vr1 = *vr1Itr;
    262     const LiveInterval &l1 = lis->getInterval(vr1);
    263     const PBQPRAProblem::AllowedSet &vr1Allowed = p->getAllowedSet(vr1);
    264 
    265     for (RegSet::const_iterator vr2Itr = std::next(vr1Itr); vr2Itr != vrEnd;
    266          ++vr2Itr) {
    267       unsigned vr2 = *vr2Itr;
    268       const LiveInterval &l2 = lis->getInterval(vr2);
    269       const PBQPRAProblem::AllowedSet &vr2Allowed = p->getAllowedSet(vr2);
    270 
    271       assert(!l2.empty() && "Empty interval in vreg set?");
    272       if (l1.overlaps(l2)) {
    273         PBQP::Matrix edgeCosts(vr1Allowed.size()+1, vr2Allowed.size()+1, 0);
    274         addInterferenceCosts(edgeCosts, vr1Allowed, vr2Allowed, tri);
    275 
    276         g.addEdge(p->getNodeForVReg(vr1), p->getNodeForVReg(vr2),
    277                   std::move(edgeCosts));
    278       }
    279     }
    280   }
    281 
    282   return p.release();
    283 }
    284 
    285 void PBQPBuilder::addSpillCosts(PBQP::Vector &costVec,
    286                                 PBQP::PBQPNum spillCost) {
    287   costVec[0] = spillCost;
    288 }
    289 
    290 void PBQPBuilder::addInterferenceCosts(
    291                                     PBQP::Matrix &costMat,
    292                                     const PBQPRAProblem::AllowedSet &vr1Allowed,
    293                                     const PBQPRAProblem::AllowedSet &vr2Allowed,
    294                                     const TargetRegisterInfo *tri) {
    295   assert(costMat.getRows() == vr1Allowed.size() + 1 && "Matrix height mismatch.");
    296   assert(costMat.getCols() == vr2Allowed.size() + 1 && "Matrix width mismatch.");
    297 
    298   for (unsigned i = 0; i != vr1Allowed.size(); ++i) {
    299     unsigned preg1 = vr1Allowed[i];
    300 
    301     for (unsigned j = 0; j != vr2Allowed.size(); ++j) {
    302       unsigned preg2 = vr2Allowed[j];
    303 
    304       if (tri->regsOverlap(preg1, preg2)) {
    305         costMat[i + 1][j + 1] = std::numeric_limits<PBQP::PBQPNum>::infinity();
    306       }
    307     }
    308   }
    309 }
    310 
    311 PBQPRAProblem *PBQPBuilderWithCoalescing::build(MachineFunction *mf,
    312                                                 const LiveIntervals *lis,
    313                                                 const MachineBlockFrequencyInfo *mbfi,
    314                                                 const RegSet &vregs) {
    315 
    316   std::unique_ptr<PBQPRAProblem> p(PBQPBuilder::build(mf, lis, mbfi, vregs));
    317   PBQPRAGraph &g = p->getGraph();
    318 
    319   const TargetMachine &tm = mf->getTarget();
    320   CoalescerPair cp(*tm.getRegisterInfo());
    321 
    322   // Scan the machine function and add a coalescing cost whenever CoalescerPair
    323   // gives the Ok.
    324   for (const auto &mbb : *mf) {
    325     for (const auto &mi : mbb) {
    326       if (!cp.setRegisters(&mi)) {
    327         continue; // Not coalescable.
    328       }
    329 
    330       if (cp.getSrcReg() == cp.getDstReg()) {
    331         continue; // Already coalesced.
    332       }
    333 
    334       unsigned dst = cp.getDstReg(),
    335                src = cp.getSrcReg();
    336 
    337       const float copyFactor = 0.5; // Cost of copy relative to load. Current
    338       // value plucked randomly out of the air.
    339 
    340       PBQP::PBQPNum cBenefit =
    341         copyFactor * LiveIntervals::getSpillWeight(false, true, mbfi, &mi);
    342 
    343       if (cp.isPhys()) {
    344         if (!mf->getRegInfo().isAllocatable(dst)) {
    345           continue;
    346         }
    347 
    348         const PBQPRAProblem::AllowedSet &allowed = p->getAllowedSet(src);
    349         unsigned pregOpt = 0;
    350         while (pregOpt < allowed.size() && allowed[pregOpt] != dst) {
    351           ++pregOpt;
    352         }
    353         if (pregOpt < allowed.size()) {
    354           ++pregOpt; // +1 to account for spill option.
    355           PBQPRAGraph::NodeId node = p->getNodeForVReg(src);
    356           llvm::dbgs() << "Reading node costs for node " << node << "\n";
    357           llvm::dbgs() << "Source node: " << &g.getNodeCosts(node) << "\n";
    358           PBQP::Vector newCosts(g.getNodeCosts(node));
    359           addPhysRegCoalesce(newCosts, pregOpt, cBenefit);
    360           g.setNodeCosts(node, newCosts);
    361         }
    362       } else {
    363         const PBQPRAProblem::AllowedSet *allowed1 = &p->getAllowedSet(dst);
    364         const PBQPRAProblem::AllowedSet *allowed2 = &p->getAllowedSet(src);
    365         PBQPRAGraph::NodeId node1 = p->getNodeForVReg(dst);
    366         PBQPRAGraph::NodeId node2 = p->getNodeForVReg(src);
    367         PBQPRAGraph::EdgeId edge = g.findEdge(node1, node2);
    368         if (edge == g.invalidEdgeId()) {
    369           PBQP::Matrix costs(allowed1->size() + 1, allowed2->size() + 1, 0);
    370           addVirtRegCoalesce(costs, *allowed1, *allowed2, cBenefit);
    371           g.addEdge(node1, node2, costs);
    372         } else {
    373           if (g.getEdgeNode1Id(edge) == node2) {
    374             std::swap(node1, node2);
    375             std::swap(allowed1, allowed2);
    376           }
    377           PBQP::Matrix costs(g.getEdgeCosts(edge));
    378           addVirtRegCoalesce(costs, *allowed1, *allowed2, cBenefit);
    379           g.setEdgeCosts(edge, costs);
    380         }
    381       }
    382     }
    383   }
    384 
    385   return p.release();
    386 }
    387 
    388 void PBQPBuilderWithCoalescing::addPhysRegCoalesce(PBQP::Vector &costVec,
    389                                                    unsigned pregOption,
    390                                                    PBQP::PBQPNum benefit) {
    391   costVec[pregOption] += -benefit;
    392 }
    393 
    394 void PBQPBuilderWithCoalescing::addVirtRegCoalesce(
    395                                     PBQP::Matrix &costMat,
    396                                     const PBQPRAProblem::AllowedSet &vr1Allowed,
    397                                     const PBQPRAProblem::AllowedSet &vr2Allowed,
    398                                     PBQP::PBQPNum benefit) {
    399 
    400   assert(costMat.getRows() == vr1Allowed.size() + 1 && "Size mismatch.");
    401   assert(costMat.getCols() == vr2Allowed.size() + 1 && "Size mismatch.");
    402 
    403   for (unsigned i = 0; i != vr1Allowed.size(); ++i) {
    404     unsigned preg1 = vr1Allowed[i];
    405     for (unsigned j = 0; j != vr2Allowed.size(); ++j) {
    406       unsigned preg2 = vr2Allowed[j];
    407 
    408       if (preg1 == preg2) {
    409         costMat[i + 1][j + 1] += -benefit;
    410       }
    411     }
    412   }
    413 }
    414 
    415 
    416 void RegAllocPBQP::getAnalysisUsage(AnalysisUsage &au) const {
    417   au.setPreservesCFG();
    418   au.addRequired<AliasAnalysis>();
    419   au.addPreserved<AliasAnalysis>();
    420   au.addRequired<SlotIndexes>();
    421   au.addPreserved<SlotIndexes>();
    422   au.addRequired<LiveIntervals>();
    423   au.addPreserved<LiveIntervals>();
    424   //au.addRequiredID(SplitCriticalEdgesID);
    425   if (customPassID)
    426     au.addRequiredID(*customPassID);
    427   au.addRequired<LiveStacks>();
    428   au.addPreserved<LiveStacks>();
    429   au.addRequired<MachineBlockFrequencyInfo>();
    430   au.addPreserved<MachineBlockFrequencyInfo>();
    431   au.addRequired<MachineLoopInfo>();
    432   au.addPreserved<MachineLoopInfo>();
    433   au.addRequired<MachineDominatorTree>();
    434   au.addPreserved<MachineDominatorTree>();
    435   au.addRequired<VirtRegMap>();
    436   au.addPreserved<VirtRegMap>();
    437   MachineFunctionPass::getAnalysisUsage(au);
    438 }
    439 
    440 void RegAllocPBQP::findVRegIntervalsToAlloc() {
    441 
    442   // Iterate over all live ranges.
    443   for (unsigned i = 0, e = mri->getNumVirtRegs(); i != e; ++i) {
    444     unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
    445     if (mri->reg_nodbg_empty(Reg))
    446       continue;
    447     LiveInterval *li = &lis->getInterval(Reg);
    448 
    449     // If this live interval is non-empty we will use pbqp to allocate it.
    450     // Empty intervals we allocate in a simple post-processing stage in
    451     // finalizeAlloc.
    452     if (!li->empty()) {
    453       vregsToAlloc.insert(li->reg);
    454     } else {
    455       emptyIntervalVRegs.insert(li->reg);
    456     }
    457   }
    458 }
    459 
    460 bool RegAllocPBQP::mapPBQPToRegAlloc(const PBQPRAProblem &problem,
    461                                      const PBQP::Solution &solution) {
    462   // Set to true if we have any spills
    463   bool anotherRoundNeeded = false;
    464 
    465   // Clear the existing allocation.
    466   vrm->clearAllVirt();
    467 
    468   const PBQPRAGraph &g = problem.getGraph();
    469   // Iterate over the nodes mapping the PBQP solution to a register
    470   // assignment.
    471   for (auto NId : g.nodeIds()) {
    472     unsigned vreg = problem.getVRegForNode(NId);
    473     unsigned alloc = solution.getSelection(NId);
    474 
    475     if (problem.isPRegOption(vreg, alloc)) {
    476       unsigned preg = problem.getPRegForOption(vreg, alloc);
    477       DEBUG(dbgs() << "VREG " << PrintReg(vreg, tri) << " -> "
    478             << tri->getName(preg) << "\n");
    479       assert(preg != 0 && "Invalid preg selected.");
    480       vrm->assignVirt2Phys(vreg, preg);
    481     } else if (problem.isSpillOption(vreg, alloc)) {
    482       vregsToAlloc.erase(vreg);
    483       SmallVector<unsigned, 8> newSpills;
    484       LiveRangeEdit LRE(&lis->getInterval(vreg), newSpills, *mf, *lis, vrm);
    485       spiller->spill(LRE);
    486 
    487       DEBUG(dbgs() << "VREG " << PrintReg(vreg, tri) << " -> SPILLED (Cost: "
    488                    << LRE.getParent().weight << ", New vregs: ");
    489 
    490       // Copy any newly inserted live intervals into the list of regs to
    491       // allocate.
    492       for (LiveRangeEdit::iterator itr = LRE.begin(), end = LRE.end();
    493            itr != end; ++itr) {
    494         LiveInterval &li = lis->getInterval(*itr);
    495         assert(!li.empty() && "Empty spill range.");
    496         DEBUG(dbgs() << PrintReg(li.reg, tri) << " ");
    497         vregsToAlloc.insert(li.reg);
    498       }
    499 
    500       DEBUG(dbgs() << ")\n");
    501 
    502       // We need another round if spill intervals were added.
    503       anotherRoundNeeded |= !LRE.empty();
    504     } else {
    505       llvm_unreachable("Unknown allocation option.");
    506     }
    507   }
    508 
    509   return !anotherRoundNeeded;
    510 }
    511 
    512 
    513 void RegAllocPBQP::finalizeAlloc() const {
    514   // First allocate registers for the empty intervals.
    515   for (RegSet::const_iterator
    516          itr = emptyIntervalVRegs.begin(), end = emptyIntervalVRegs.end();
    517          itr != end; ++itr) {
    518     LiveInterval *li = &lis->getInterval(*itr);
    519 
    520     unsigned physReg = mri->getSimpleHint(li->reg);
    521 
    522     if (physReg == 0) {
    523       const TargetRegisterClass *liRC = mri->getRegClass(li->reg);
    524       physReg = liRC->getRawAllocationOrder(*mf).front();
    525     }
    526 
    527     vrm->assignVirt2Phys(li->reg, physReg);
    528   }
    529 }
    530 
    531 bool RegAllocPBQP::runOnMachineFunction(MachineFunction &MF) {
    532 
    533   mf = &MF;
    534   tm = &mf->getTarget();
    535   tri = tm->getRegisterInfo();
    536   tii = tm->getInstrInfo();
    537   mri = &mf->getRegInfo();
    538 
    539   lis = &getAnalysis<LiveIntervals>();
    540   lss = &getAnalysis<LiveStacks>();
    541   mbfi = &getAnalysis<MachineBlockFrequencyInfo>();
    542 
    543   calculateSpillWeightsAndHints(*lis, MF, getAnalysis<MachineLoopInfo>(),
    544                                 *mbfi);
    545 
    546   vrm = &getAnalysis<VirtRegMap>();
    547   spiller.reset(createInlineSpiller(*this, MF, *vrm));
    548 
    549   mri->freezeReservedRegs(MF);
    550 
    551   DEBUG(dbgs() << "PBQP Register Allocating for " << mf->getName() << "\n");
    552 
    553   // Allocator main loop:
    554   //
    555   // * Map current regalloc problem to a PBQP problem
    556   // * Solve the PBQP problem
    557   // * Map the solution back to a register allocation
    558   // * Spill if necessary
    559   //
    560   // This process is continued till no more spills are generated.
    561 
    562   // Find the vreg intervals in need of allocation.
    563   findVRegIntervalsToAlloc();
    564 
    565 #ifndef NDEBUG
    566   const Function* func = mf->getFunction();
    567   std::string fqn =
    568     func->getParent()->getModuleIdentifier() + "." +
    569     func->getName().str();
    570 #endif
    571 
    572   // If there are non-empty intervals allocate them using pbqp.
    573   if (!vregsToAlloc.empty()) {
    574 
    575     bool pbqpAllocComplete = false;
    576     unsigned round = 0;
    577 
    578     while (!pbqpAllocComplete) {
    579       DEBUG(dbgs() << "  PBQP Regalloc round " << round << ":\n");
    580 
    581       std::unique_ptr<PBQPRAProblem> problem(
    582           builder->build(mf, lis, mbfi, vregsToAlloc));
    583 
    584 #ifndef NDEBUG
    585       if (pbqpDumpGraphs) {
    586         std::ostringstream rs;
    587         rs << round;
    588         std::string graphFileName(fqn + "." + rs.str() + ".pbqpgraph");
    589         std::string tmp;
    590         raw_fd_ostream os(graphFileName.c_str(), tmp, sys::fs::F_Text);
    591         DEBUG(dbgs() << "Dumping graph for round " << round << " to \""
    592               << graphFileName << "\"\n");
    593         problem->getGraph().dump(os);
    594       }
    595 #endif
    596 
    597       PBQP::Solution solution =
    598         PBQP::RegAlloc::solve(problem->getGraph());
    599 
    600       pbqpAllocComplete = mapPBQPToRegAlloc(*problem, solution);
    601 
    602       ++round;
    603     }
    604   }
    605 
    606   // Finalise allocation, allocate empty ranges.
    607   finalizeAlloc();
    608   vregsToAlloc.clear();
    609   emptyIntervalVRegs.clear();
    610 
    611   DEBUG(dbgs() << "Post alloc VirtRegMap:\n" << *vrm << "\n");
    612 
    613   return true;
    614 }
    615 
    616 FunctionPass *
    617 llvm::createPBQPRegisterAllocator(std::unique_ptr<PBQPBuilder> &builder,
    618                                   char *customPassID) {
    619   return new RegAllocPBQP(builder, customPassID);
    620 }
    621 
    622 FunctionPass* llvm::createDefaultPBQPRegisterAllocator() {
    623   std::unique_ptr<PBQPBuilder> Builder;
    624   if (pbqpCoalescing)
    625     Builder.reset(new PBQPBuilderWithCoalescing());
    626   else
    627     Builder.reset(new PBQPBuilder());
    628   return createPBQPRegisterAllocator(Builder);
    629 }
    630 
    631 #undef DEBUG_TYPE
    632