1 //===-- RegAllocGreedy.cpp - greedy register allocator --------------------===//
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 defines the RAGreedy function pass for register allocation in
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "regalloc"
16 #include "AllocationOrder.h"
17 #include "LiveIntervalUnion.h"
18 #include "LiveRangeEdit.h"
19 #include "RegAllocBase.h"
21 #include "SpillPlacement.h"
23 #include "VirtRegMap.h"
24 #include "VirtRegRewriter.h"
25 #include "llvm/Analysis/AliasAnalysis.h"
26 #include "llvm/Function.h"
27 #include "llvm/PassAnalysisSupport.h"
28 #include "llvm/CodeGen/CalcSpillWeights.h"
29 #include "llvm/CodeGen/EdgeBundles.h"
30 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
31 #include "llvm/CodeGen/LiveStackAnalysis.h"
32 #include "llvm/CodeGen/MachineDominators.h"
33 #include "llvm/CodeGen/MachineFunctionPass.h"
34 #include "llvm/CodeGen/MachineLoopInfo.h"
35 #include "llvm/CodeGen/MachineLoopRanges.h"
36 #include "llvm/CodeGen/MachineRegisterInfo.h"
37 #include "llvm/CodeGen/Passes.h"
38 #include "llvm/CodeGen/RegAllocRegistry.h"
39 #include "llvm/CodeGen/RegisterCoalescer.h"
40 #include "llvm/Target/TargetOptions.h"
41 #include "llvm/Support/Debug.h"
42 #include "llvm/Support/ErrorHandling.h"
43 #include "llvm/Support/raw_ostream.h"
44 #include "llvm/Support/Timer.h"
48 static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator",
49 createGreedyRegisterAllocator);
52 class RAGreedy : public MachineFunctionPass, public RegAllocBase {
55 BitVector ReservedRegs;
60 MachineDominatorTree *DomTree;
61 MachineLoopInfo *Loops;
62 MachineLoopRanges *LoopRanges;
64 SpillPlacement *SpillPlacer;
67 std::auto_ptr<Spiller> SpillerInstance;
68 std::auto_ptr<SplitAnalysis> SA;
72 /// All basic blocks where the current register is live.
73 SmallVector<SpillPlacement::BlockConstraint, 8> SpillConstraints;
75 /// Additional information about basic blocks where the current variable is
76 /// live. Such a block will look like one of these templates:
78 /// 1. | o---x | Internal to block. Variable is only live in this block.
79 /// 2. |---x | Live-in, kill.
80 /// 3. | o---| Def, live-out.
81 /// 4. |---x o---| Live-in, kill, def, live-out.
82 /// 5. |---o---o---| Live-through with uses or defs.
83 /// 6. |-----------| Live-through without uses. Transparent.
86 const MachineBasicBlock *MBB;
87 SlotIndex FirstUse; ///< First instr using current reg.
88 SlotIndex LastUse; ///< Last instr using current reg.
89 SlotIndex Kill; ///< Interval end point inside block.
90 SlotIndex Def; ///< Interval start point inside block.
91 bool Uses; ///< Current reg has uses or defs in block.
92 bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above).
93 bool LiveIn; ///< Current reg is live in.
94 bool LiveOut; ///< Current reg is live out.
96 // Per-interference pattern scratch data.
97 bool OverlapEntry; ///< Interference overlaps entering interval.
98 bool OverlapExit; ///< Interference overlaps exiting interval.
101 /// Basic blocks where var is live. This array is parallel to
102 /// SpillConstraints.
103 SmallVector<BlockInfo, 8> LiveBlocks;
108 /// Return the pass name.
109 virtual const char* getPassName() const {
110 return "Greedy Register Allocator";
113 /// RAGreedy analysis usage.
114 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
116 virtual void releaseMemory();
118 virtual Spiller &spiller() { return *SpillerInstance; }
120 virtual float getPriority(LiveInterval *LI);
122 virtual unsigned selectOrSplit(LiveInterval &VirtReg,
123 SmallVectorImpl<LiveInterval*> &SplitVRegs);
125 /// Perform register allocation.
126 virtual bool runOnMachineFunction(MachineFunction &mf);
131 bool checkUncachedInterference(LiveInterval&, unsigned);
132 LiveInterval *getSingleInterference(LiveInterval&, unsigned);
133 bool reassignVReg(LiveInterval &InterferingVReg, unsigned OldPhysReg);
134 bool reassignInterferences(LiveInterval &VirtReg, unsigned PhysReg);
135 unsigned findInterferenceFreeReg(MachineLoopRange*,
136 LiveInterval&, AllocationOrder&);
137 float calcInterferenceWeight(LiveInterval&, unsigned);
138 void calcLiveBlockInfo(LiveInterval&);
139 float calcInterferenceInfo(LiveInterval&, unsigned);
140 float calcGlobalSplitCost(const BitVector&);
142 unsigned tryReassign(LiveInterval&, AllocationOrder&);
143 unsigned tryRegionSplit(LiveInterval&, AllocationOrder&,
144 SmallVectorImpl<LiveInterval*>&);
145 unsigned trySplit(LiveInterval&, AllocationOrder&,
146 SmallVectorImpl<LiveInterval*>&);
147 unsigned trySpillInterferences(LiveInterval&, AllocationOrder&,
148 SmallVectorImpl<LiveInterval*>&);
150 } // end anonymous namespace
152 char RAGreedy::ID = 0;
154 FunctionPass* llvm::createGreedyRegisterAllocator() {
155 return new RAGreedy();
158 RAGreedy::RAGreedy(): MachineFunctionPass(ID) {
159 initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
160 initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
161 initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
162 initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
163 initializeRegisterCoalescerAnalysisGroup(*PassRegistry::getPassRegistry());
164 initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
165 initializeLiveStacksPass(*PassRegistry::getPassRegistry());
166 initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry());
167 initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
168 initializeMachineLoopRangesPass(*PassRegistry::getPassRegistry());
169 initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
170 initializeEdgeBundlesPass(*PassRegistry::getPassRegistry());
171 initializeSpillPlacementPass(*PassRegistry::getPassRegistry());
174 void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
175 AU.setPreservesCFG();
176 AU.addRequired<AliasAnalysis>();
177 AU.addPreserved<AliasAnalysis>();
178 AU.addRequired<LiveIntervals>();
179 AU.addRequired<SlotIndexes>();
180 AU.addPreserved<SlotIndexes>();
182 AU.addRequiredID(StrongPHIEliminationID);
183 AU.addRequiredTransitive<RegisterCoalescer>();
184 AU.addRequired<CalculateSpillWeights>();
185 AU.addRequired<LiveStacks>();
186 AU.addPreserved<LiveStacks>();
187 AU.addRequired<MachineDominatorTree>();
188 AU.addPreserved<MachineDominatorTree>();
189 AU.addRequired<MachineLoopInfo>();
190 AU.addPreserved<MachineLoopInfo>();
191 AU.addRequired<MachineLoopRanges>();
192 AU.addPreserved<MachineLoopRanges>();
193 AU.addRequired<VirtRegMap>();
194 AU.addPreserved<VirtRegMap>();
195 AU.addRequired<EdgeBundles>();
196 AU.addRequired<SpillPlacement>();
197 MachineFunctionPass::getAnalysisUsage(AU);
200 void RAGreedy::releaseMemory() {
201 SpillerInstance.reset(0);
202 RegAllocBase::releaseMemory();
205 float RAGreedy::getPriority(LiveInterval *LI) {
206 float Priority = LI->weight;
208 // Prioritize hinted registers so they are allocated first.
209 std::pair<unsigned, unsigned> Hint;
210 if (Hint.first || Hint.second) {
211 // The hint can be target specific, a virtual register, or a physreg.
214 // Prefer physreg hints above anything else.
215 if (Hint.first == 0 && TargetRegisterInfo::isPhysicalRegister(Hint.second))
222 //===----------------------------------------------------------------------===//
223 // Register Reassignment
224 //===----------------------------------------------------------------------===//
226 // Check interference without using the cache.
227 bool RAGreedy::checkUncachedInterference(LiveInterval &VirtReg,
229 for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
230 LiveIntervalUnion::Query subQ(&VirtReg, &PhysReg2LiveUnion[*AliasI]);
231 if (subQ.checkInterference())
237 /// getSingleInterference - Return the single interfering virtual register
238 /// assigned to PhysReg. Return 0 if more than one virtual register is
240 LiveInterval *RAGreedy::getSingleInterference(LiveInterval &VirtReg,
242 // Check physreg and aliases.
243 LiveInterval *Interference = 0;
244 for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
245 LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
246 if (Q.checkInterference()) {
249 Q.collectInterferingVRegs(1);
250 if (!Q.seenAllInterferences())
252 Interference = Q.interferingVRegs().front();
258 // Attempt to reassign this virtual register to a different physical register.
260 // FIXME: we are not yet caching these "second-level" interferences discovered
261 // in the sub-queries. These interferences can change with each call to
262 // selectOrSplit. However, we could implement a "may-interfere" cache that
263 // could be conservatively dirtied when we reassign or split.
265 // FIXME: This may result in a lot of alias queries. We could summarize alias
266 // live intervals in their parent register's live union, but it's messy.
267 bool RAGreedy::reassignVReg(LiveInterval &InterferingVReg,
268 unsigned WantedPhysReg) {
269 assert(TargetRegisterInfo::isVirtualRegister(InterferingVReg.reg) &&
270 "Can only reassign virtual registers");
271 assert(TRI->regsOverlap(WantedPhysReg, VRM->getPhys(InterferingVReg.reg)) &&
272 "inconsistent phys reg assigment");
274 AllocationOrder Order(InterferingVReg.reg, *VRM, ReservedRegs);
275 while (unsigned PhysReg = Order.next()) {
276 // Don't reassign to a WantedPhysReg alias.
277 if (TRI->regsOverlap(PhysReg, WantedPhysReg))
280 if (checkUncachedInterference(InterferingVReg, PhysReg))
283 // Reassign the interfering virtual reg to this physical reg.
284 unsigned OldAssign = VRM->getPhys(InterferingVReg.reg);
285 DEBUG(dbgs() << "reassigning: " << InterferingVReg << " from " <<
286 TRI->getName(OldAssign) << " to " << TRI->getName(PhysReg) << '\n');
287 PhysReg2LiveUnion[OldAssign].extract(InterferingVReg);
288 VRM->clearVirt(InterferingVReg.reg);
289 VRM->assignVirt2Phys(InterferingVReg.reg, PhysReg);
290 PhysReg2LiveUnion[PhysReg].unify(InterferingVReg);
297 /// reassignInterferences - Reassign all interferences to different physical
298 /// registers such that Virtreg can be assigned to PhysReg.
299 /// Currently this only works with a single interference.
300 /// @param VirtReg Currently unassigned virtual register.
301 /// @param PhysReg Physical register to be cleared.
302 /// @return True on success, false if nothing was changed.
303 bool RAGreedy::reassignInterferences(LiveInterval &VirtReg, unsigned PhysReg) {
304 LiveInterval *InterferingVReg = getSingleInterference(VirtReg, PhysReg);
305 if (!InterferingVReg)
307 if (TargetRegisterInfo::isPhysicalRegister(InterferingVReg->reg))
309 return reassignVReg(*InterferingVReg, PhysReg);
312 /// tryReassign - Try to reassign interferences to different physregs.
313 /// @param VirtReg Currently unassigned virtual register.
314 /// @param Order Physregs to try.
315 /// @return Physreg to assign VirtReg, or 0.
316 unsigned RAGreedy::tryReassign(LiveInterval &VirtReg, AllocationOrder &Order) {
317 NamedRegionTimer T("Reassign", TimerGroupName, TimePassesIsEnabled);
319 while (unsigned PhysReg = Order.next())
320 if (reassignInterferences(VirtReg, PhysReg))
326 //===----------------------------------------------------------------------===//
328 //===----------------------------------------------------------------------===//
330 /// findInterferenceFreeReg - Find a physical register in Order where Loop has
331 /// no interferences with VirtReg.
332 unsigned RAGreedy::findInterferenceFreeReg(MachineLoopRange *Loop,
333 LiveInterval &VirtReg,
334 AllocationOrder &Order) {
336 while (unsigned PhysReg = Order.next()) {
337 bool interference = false;
338 for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
339 if (query(VirtReg, *AI).checkLoopInterference(Loop)) {
351 /// trySplit - Try to split VirtReg or one of its interferences, making it
353 /// @return Physreg when VirtReg may be assigned and/or new SplitVRegs.
354 unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
355 SmallVectorImpl<LiveInterval*>&SplitVRegs) {
356 // Don't attempt splitting on local intervals for now.
357 if (LIS->intervalIsInOneMBB(VirtReg))
360 NamedRegionTimer T("Splitter", TimerGroupName, TimePassesIsEnabled);
361 SA->analyze(&VirtReg);
363 // Get the set of loops that have VirtReg uses and are splittable.
364 SplitAnalysis::LoopPtrSet SplitLoopSet;
365 SA->getSplitLoops(SplitLoopSet);
367 // Order loops by descending area.
368 SmallVector<MachineLoopRange*, 8> SplitLoops;
369 for (SplitAnalysis::LoopPtrSet::const_iterator I = SplitLoopSet.begin(),
370 E = SplitLoopSet.end(); I != E; ++I)
371 SplitLoops.push_back(LoopRanges->getLoopRange(*I));
372 array_pod_sort(SplitLoops.begin(), SplitLoops.end(),
373 MachineLoopRange::byAreaDesc);
375 // Find the first loop that is interference-free for some register in the
377 MachineLoopRange *Loop = 0;
378 for (unsigned i = 0, e = SplitLoops.size(); i != e; ++i) {
379 DEBUG(dbgs() << " Checking " << *SplitLoops[i]);
380 if (unsigned PhysReg = findInterferenceFreeReg(SplitLoops[i],
383 Loop = SplitLoops[i];
384 DEBUG(dbgs() << ": Use %" << TRI->getName(PhysReg) << '\n');
387 DEBUG(dbgs() << ": Interference.\n");
392 DEBUG(dbgs() << " All candidate loops have interference.\n");
396 // Execute the split around Loop.
397 SmallVector<LiveInterval*, 4> SpillRegs;
398 LiveRangeEdit LREdit(VirtReg, SplitVRegs, SpillRegs);
399 SplitEditor(*SA, *LIS, *VRM, *DomTree, LREdit)
400 .splitAroundLoop(Loop->getLoop());
403 MF->verify(this, "After splitting live range around loop");
405 // We have new split regs, don't assign anything.
410 //===----------------------------------------------------------------------===//
412 //===----------------------------------------------------------------------===//
414 /// calcLiveBlockInfo - Fill the LiveBlocks array with information about blocks
415 /// where VirtReg is live.
416 /// The SpillConstraints array is minimally initialized with MBB->getNumber().
417 void RAGreedy::calcLiveBlockInfo(LiveInterval &VirtReg) {
419 SpillConstraints.clear();
421 assert(!VirtReg.empty() && "Cannot allocate an empty interval");
422 LiveInterval::const_iterator LVI = VirtReg.begin();
423 LiveInterval::const_iterator LVE = VirtReg.end();
425 SmallVectorImpl<SlotIndex>::const_iterator UseI, UseE;
426 UseI = SA->UseSlots.begin();
427 UseE = SA->UseSlots.end();
429 // Loop over basic blocks where VirtReg is live.
430 MachineFunction::const_iterator MFI = Indexes->getMBBFromIndex(LVI->start);
432 // Block constraints depend on the interference pattern.
433 // Just allocate them here, don't compute anything.
434 SpillPlacement::BlockConstraint BC;
435 BC.Number = MFI->getNumber();
436 SpillConstraints.push_back(BC);
440 SlotIndex Start, Stop;
441 tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
443 // LVI is the first live segment overlapping MBB.
444 BI.LiveIn = LVI->start <= Start;
448 // Find the first and last uses in the block.
449 BI.Uses = SA->hasUses(MFI);
450 if (BI.Uses && UseI != UseE) {
452 assert(BI.FirstUse >= Start);
454 while (UseI != UseE && *UseI < Stop);
455 BI.LastUse = UseI[-1];
456 assert(BI.LastUse < Stop);
459 // Look for gaps in the live range.
462 while (LVI->end < Stop) {
463 SlotIndex LastStop = LVI->end;
464 if (++LVI == LVE || LVI->start >= Stop) {
469 if (LastStop < LVI->start) {
476 // Don't set LiveThrough when the block has a gap.
477 BI.LiveThrough = !hasGap && BI.LiveIn && BI.LiveOut;
478 LiveBlocks.push_back(BI);
480 // LVI is now at LVE or LVI->end >= Stop.
484 // Live segment ends exactly at Stop. Move to the next segment.
485 if (LVI->end == Stop && ++LVI == LVE)
488 // Pick the next basic block.
489 if (LVI->start < Stop)
492 MFI = Indexes->getMBBFromIndex(LVI->start);
496 /// calcInterferenceInfo - Compute per-block outgoing and ingoing constraints
497 /// when considering interference from PhysReg. Also compute an optimistic local
498 /// cost of this interference pattern.
500 /// The final cost of a split is the local cost + global cost of preferences
501 /// broken by SpillPlacement.
503 float RAGreedy::calcInterferenceInfo(LiveInterval &VirtReg, unsigned PhysReg) {
504 // Reset interference dependent info.
505 for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
506 BlockInfo &BI = LiveBlocks[i];
507 SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
508 BC.Entry = (BI.Uses && BI.LiveIn) ?
509 SpillPlacement::PrefReg : SpillPlacement::DontCare;
510 BC.Exit = (BI.Uses && BI.LiveOut) ?
511 SpillPlacement::PrefReg : SpillPlacement::DontCare;
512 BI.OverlapEntry = BI.OverlapExit = false;
515 // Add interference info from each PhysReg alias.
516 for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
517 if (!query(VirtReg, *AI).checkInterference())
519 DEBUG(PhysReg2LiveUnion[*AI].print(dbgs(), TRI));
520 LiveIntervalUnion::SegmentIter IntI =
521 PhysReg2LiveUnion[*AI].find(VirtReg.beginIndex());
525 for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
526 BlockInfo &BI = LiveBlocks[i];
527 SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
528 SlotIndex Start, Stop;
529 tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
531 // Skip interference-free blocks.
532 if (IntI.start() >= Stop)
535 // Handle transparent blocks with interference separately.
536 // Transparent blocks never incur any fixed cost.
537 if (BI.LiveThrough && !BI.Uses) {
538 // Check if interference is live-in - force spill.
539 if (BC.Entry != SpillPlacement::MustSpill) {
540 BC.Entry = SpillPlacement::PrefSpill;
541 IntI.advanceTo(Start);
542 if (IntI.valid() && IntI.start() <= Start)
543 BC.Entry = SpillPlacement::MustSpill;
546 // Check if interference is live-out - force spill.
547 if (BC.Exit != SpillPlacement::MustSpill) {
548 BC.Exit = SpillPlacement::PrefSpill;
549 IntI.advanceTo(Stop);
550 if (IntI.valid() && IntI.start() < Stop)
551 BC.Exit = SpillPlacement::MustSpill;
554 // Nothing more to do for this transparent block.
560 // Now we only have blocks with uses left.
561 // Check if the interference overlaps the uses.
562 assert(BI.Uses && "Non-transparent block without any uses");
564 // Check interference on entry.
565 if (BI.LiveIn && BC.Entry != SpillPlacement::MustSpill) {
566 IntI.advanceTo(Start);
570 // Interference is live-in - force spill.
571 if (IntI.start() <= Start)
572 BC.Entry = SpillPlacement::MustSpill;
573 // Not live in, but before the first use.
574 else if (IntI.start() < BI.FirstUse)
575 BC.Entry = SpillPlacement::PrefSpill;
578 // Does interference overlap the uses in the entry segment
580 if (BI.LiveIn && !BI.OverlapEntry) {
581 IntI.advanceTo(BI.FirstUse);
584 // A live-through interval has no kill.
585 // Check [FirstUse;LastUse) instead.
586 if (IntI.start() < (BI.LiveThrough ? BI.LastUse : BI.Kill))
587 BI.OverlapEntry = true;
590 // Does interference overlap the uses in the exit segment [Def;LastUse)?
591 if (BI.LiveOut && !BI.LiveThrough && !BI.OverlapExit) {
592 IntI.advanceTo(BI.Def);
595 if (IntI.start() < BI.LastUse)
596 BI.OverlapExit = true;
599 // Check interference on exit.
600 if (BI.LiveOut && BC.Exit != SpillPlacement::MustSpill) {
601 // Check interference between LastUse and Stop.
602 if (BC.Exit != SpillPlacement::PrefSpill) {
603 IntI.advanceTo(BI.LastUse);
606 if (IntI.start() < Stop)
607 BC.Exit = SpillPlacement::PrefSpill;
609 // Is the interference live-out?
610 IntI.advanceTo(Stop);
613 if (IntI.start() < Stop)
614 BC.Exit = SpillPlacement::MustSpill;
619 // Accumulate a local cost of this interference pattern.
621 for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
622 BlockInfo &BI = LiveBlocks[i];
625 SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
626 unsigned Inserts = 0;
628 // Do we need spill code for the entry segment?
630 Inserts += BI.OverlapEntry || BC.Entry != SpillPlacement::PrefReg;
632 // For the exit segment?
634 Inserts += BI.OverlapExit || BC.Exit != SpillPlacement::PrefReg;
636 // The local cost of spill code in this block is the block frequency times
637 // the number of spill instructions inserted.
639 LocalCost += Inserts * SpillPlacer->getBlockFrequency(BI.MBB);
641 DEBUG(dbgs() << "Local cost of " << PrintReg(PhysReg, TRI) << " = "
642 << LocalCost << '\n');
646 /// calcGlobalSplitCost - Return the global split cost of following the split
647 /// pattern in LiveBundles. This cost should be added to the local cost of the
648 /// interference pattern in SpillConstraints.
650 float RAGreedy::calcGlobalSplitCost(const BitVector &LiveBundles) {
651 float GlobalCost = 0;
652 for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
653 SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
654 unsigned Inserts = 0;
655 // Broken entry preference?
656 Inserts += LiveBundles[Bundles->getBundle(BC.Number, 0)] !=
657 (BC.Entry == SpillPlacement::PrefReg);
658 // Broken exit preference?
659 Inserts += LiveBundles[Bundles->getBundle(BC.Number, 1)] !=
660 (BC.Exit == SpillPlacement::PrefReg);
662 GlobalCost += Inserts * SpillPlacer->getBlockFrequency(LiveBlocks[i].MBB);
664 DEBUG(dbgs() << "Global cost = " << GlobalCost << '\n');
668 unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
669 SmallVectorImpl<LiveInterval*> &NewVRegs) {
670 calcLiveBlockInfo(VirtReg);
671 BitVector LiveBundles, BestBundles;
673 unsigned BestReg = 0;
675 while (unsigned PhysReg = Order.next()) {
676 float Cost = calcInterferenceInfo(VirtReg, PhysReg);
677 if (BestReg && Cost >= BestCost)
679 if (!SpillPlacer->placeSpills(SpillConstraints, LiveBundles))
680 Cost += calcGlobalSplitCost(LiveBundles);
681 if (!BestReg || Cost < BestCost) {
684 BestBundles.swap(LiveBundles);
687 // FIXME: Actually execute the split.
691 //===----------------------------------------------------------------------===//
693 //===----------------------------------------------------------------------===//
695 /// calcInterferenceWeight - Calculate the combined spill weight of
696 /// interferences when assigning VirtReg to PhysReg.
697 float RAGreedy::calcInterferenceWeight(LiveInterval &VirtReg, unsigned PhysReg){
699 for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
700 LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
701 Q.collectInterferingVRegs();
702 if (Q.seenUnspillableVReg())
704 for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i)
705 Sum += Q.interferingVRegs()[i]->weight;
710 /// trySpillInterferences - Try to spill interfering registers instead of the
711 /// current one. Only do it if the accumulated spill weight is smaller than the
712 /// current spill weight.
713 unsigned RAGreedy::trySpillInterferences(LiveInterval &VirtReg,
714 AllocationOrder &Order,
715 SmallVectorImpl<LiveInterval*> &NewVRegs) {
716 NamedRegionTimer T("Spill Interference", TimerGroupName, TimePassesIsEnabled);
717 unsigned BestPhys = 0;
718 float BestWeight = 0;
721 while (unsigned PhysReg = Order.next()) {
722 float Weight = calcInterferenceWeight(VirtReg, PhysReg);
723 if (Weight == HUGE_VALF || Weight >= VirtReg.weight)
725 if (!BestPhys || Weight < BestWeight)
726 BestPhys = PhysReg, BestWeight = Weight;
729 // No candidates found.
733 // Collect all interfering registers.
734 SmallVector<LiveInterval*, 8> Spills;
735 for (const unsigned *AI = TRI->getOverlaps(BestPhys); *AI; ++AI) {
736 LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
737 Spills.append(Q.interferingVRegs().begin(), Q.interferingVRegs().end());
738 for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
739 LiveInterval *VReg = Q.interferingVRegs()[i];
740 PhysReg2LiveUnion[*AI].extract(*VReg);
741 VRM->clearVirt(VReg->reg);
746 DEBUG(dbgs() << "spilling " << Spills.size() << " interferences with weight "
747 << BestWeight << '\n');
748 for (unsigned i = 0, e = Spills.size(); i != e; ++i)
749 spiller().spill(Spills[i], NewVRegs, Spills);
754 //===----------------------------------------------------------------------===//
756 //===----------------------------------------------------------------------===//
758 unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg,
759 SmallVectorImpl<LiveInterval*> &SplitVRegs) {
760 // First try assigning a free register.
761 AllocationOrder Order(VirtReg.reg, *VRM, ReservedRegs);
762 while (unsigned PhysReg = Order.next()) {
763 if (!checkPhysRegInterference(VirtReg, PhysReg))
767 // Try to reassign interferences.
768 if (unsigned PhysReg = tryReassign(VirtReg, Order))
771 // Try splitting VirtReg or interferences.
772 unsigned PhysReg = trySplit(VirtReg, Order, SplitVRegs);
773 if (PhysReg || !SplitVRegs.empty())
776 // Try to spill another interfering reg with less spill weight.
777 PhysReg = trySpillInterferences(VirtReg, Order, SplitVRegs);
781 // Finally spill VirtReg itself.
782 NamedRegionTimer T("Spiller", TimerGroupName, TimePassesIsEnabled);
783 SmallVector<LiveInterval*, 1> pendingSpills;
784 spiller().spill(&VirtReg, SplitVRegs, pendingSpills);
786 // The live virtual register requesting allocation was spilled, so tell
787 // the caller not to allocate anything during this round.
791 bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
792 DEBUG(dbgs() << "********** GREEDY REGISTER ALLOCATION **********\n"
793 << "********** Function: "
794 << ((Value*)mf.getFunction())->getName() << '\n');
798 MF->verify(this, "Before greedy register allocator");
800 RegAllocBase::init(getAnalysis<VirtRegMap>(), getAnalysis<LiveIntervals>());
801 Indexes = &getAnalysis<SlotIndexes>();
802 DomTree = &getAnalysis<MachineDominatorTree>();
803 ReservedRegs = TRI->getReservedRegs(*MF);
804 SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM));
805 Loops = &getAnalysis<MachineLoopInfo>();
806 LoopRanges = &getAnalysis<MachineLoopRanges>();
807 Bundles = &getAnalysis<EdgeBundles>();
808 SpillPlacer = &getAnalysis<SpillPlacement>();
810 SA.reset(new SplitAnalysis(*MF, *LIS, *Loops));
817 NamedRegionTimer T("Rewriter", TimerGroupName, TimePassesIsEnabled);
818 std::auto_ptr<VirtRegRewriter> rewriter(createVirtRegRewriter());
819 rewriter->runOnMachineFunction(*MF, *VRM, LIS);
822 // The pass output is in VirtRegMap. Release all the transient data.