1 //===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===//
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 contains the SplitAnalysis class as well as mutator functions for
11 // live range splitting.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "splitter"
17 #include "VirtRegMap.h"
18 #include "llvm/CodeGen/CalcSpillWeights.h"
19 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
20 #include "llvm/CodeGen/MachineDominators.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/CodeGen/MachineLoopInfo.h"
23 #include "llvm/CodeGen/MachineRegisterInfo.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/Support/raw_ostream.h"
27 #include "llvm/Target/TargetInstrInfo.h"
28 #include "llvm/Target/TargetMachine.h"
33 AllowSplit("spiller-splits-edges",
34 cl::desc("Allow critical edge splitting during spilling"));
36 //===----------------------------------------------------------------------===//
38 //===----------------------------------------------------------------------===//
40 SplitAnalysis::SplitAnalysis(const MachineFunction &mf,
41 const LiveIntervals &lis,
42 const MachineLoopInfo &mli)
46 tii_(*mf.getTarget().getInstrInfo()),
49 void SplitAnalysis::clear() {
56 bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) {
57 MachineBasicBlock *T, *F;
58 SmallVector<MachineOperand, 4> Cond;
59 return !tii_.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond);
62 /// analyzeUses - Count instructions, basic blocks, and loops using curli.
63 void SplitAnalysis::analyzeUses() {
64 const MachineRegisterInfo &MRI = mf_.getRegInfo();
65 for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(curli_->reg);
66 MachineInstr *MI = I.skipInstruction();) {
67 if (MI->isDebugValue() || !usingInstrs_.insert(MI))
69 MachineBasicBlock *MBB = MI->getParent();
70 if (usingBlocks_[MBB]++)
72 if (MachineLoop *Loop = loops_.getLoopFor(MBB))
75 DEBUG(dbgs() << " counted "
76 << usingInstrs_.size() << " instrs, "
77 << usingBlocks_.size() << " blocks, "
78 << usingLoops_.size() << " loops.\n");
81 /// removeUse - Update statistics by noting that MI no longer uses curli.
82 void SplitAnalysis::removeUse(const MachineInstr *MI) {
83 if (!usingInstrs_.erase(MI))
86 // Decrement MBB count.
87 const MachineBasicBlock *MBB = MI->getParent();
88 BlockCountMap::iterator bi = usingBlocks_.find(MBB);
89 assert(bi != usingBlocks_.end() && "MBB missing");
90 assert(bi->second && "0 count in map");
93 // No more uses in MBB.
94 usingBlocks_.erase(bi);
96 // Decrement loop count.
97 MachineLoop *Loop = loops_.getLoopFor(MBB);
100 LoopCountMap::iterator li = usingLoops_.find(Loop);
101 assert(li != usingLoops_.end() && "Loop missing");
102 assert(li->second && "0 count in map");
105 // No more blocks in Loop.
106 usingLoops_.erase(li);
109 // Get three sets of basic blocks surrounding a loop: Blocks inside the loop,
110 // predecessor blocks, and exit blocks.
111 void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) {
114 // Blocks in the loop.
115 Blocks.Loop.insert(Loop->block_begin(), Loop->block_end());
117 // Predecessor blocks.
118 const MachineBasicBlock *Header = Loop->getHeader();
119 for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(),
120 E = Header->pred_end(); I != E; ++I)
121 if (!Blocks.Loop.count(*I))
122 Blocks.Preds.insert(*I);
125 for (MachineLoop::block_iterator I = Loop->block_begin(),
126 E = Loop->block_end(); I != E; ++I) {
127 const MachineBasicBlock *MBB = *I;
128 for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
129 SE = MBB->succ_end(); SI != SE; ++SI)
130 if (!Blocks.Loop.count(*SI))
131 Blocks.Exits.insert(*SI);
135 /// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
136 /// and around the Loop.
137 SplitAnalysis::LoopPeripheralUse SplitAnalysis::
138 analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) {
139 LoopPeripheralUse use = ContainedInLoop;
140 for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
142 const MachineBasicBlock *MBB = I->first;
143 // Is this a peripheral block?
144 if (use < MultiPeripheral &&
145 (Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) {
146 if (I->second > 1) use = MultiPeripheral;
147 else use = SinglePeripheral;
150 // Is it a loop block?
151 if (Blocks.Loop.count(MBB))
153 // It must be an unrelated block.
159 /// getCriticalExits - It may be necessary to partially break critical edges
160 /// leaving the loop if an exit block has phi uses of curli. Collect the exit
161 /// blocks that need special treatment into CriticalExits.
162 void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
163 BlockPtrSet &CriticalExits) {
164 CriticalExits.clear();
166 // A critical exit block contains a phi def of curli, and has a predecessor
167 // that is not in the loop nor a loop predecessor.
168 // For such an exit block, the edges carrying the new variable must be moved
169 // to a new pre-exit block.
170 for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end();
172 const MachineBasicBlock *Succ = *I;
173 SlotIndex SuccIdx = lis_.getMBBStartIdx(Succ);
174 VNInfo *SuccVNI = curli_->getVNInfoAt(SuccIdx);
175 // This exit may not have curli live in at all. No need to split.
178 // If this is not a PHI def, it is either using a value from before the
179 // loop, or a value defined inside the loop. Both are safe.
180 if (!SuccVNI->isPHIDef() || SuccVNI->def.getBaseIndex() != SuccIdx)
182 // This exit block does have a PHI. Does it also have a predecessor that is
183 // not a loop block or loop predecessor?
184 for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
185 PE = Succ->pred_end(); PI != PE; ++PI) {
186 const MachineBasicBlock *Pred = *PI;
187 if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred))
189 // This is a critical exit block, and we need to split the exit edge.
190 CriticalExits.insert(Succ);
196 /// canSplitCriticalExits - Return true if it is possible to insert new exit
197 /// blocks before the blocks in CriticalExits.
199 SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
200 BlockPtrSet &CriticalExits) {
201 // If we don't allow critical edge splitting, require no critical exits.
203 return CriticalExits.empty();
205 for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end();
207 const MachineBasicBlock *Succ = *I;
208 // We want to insert a new pre-exit MBB before Succ, and change all the
209 // in-loop blocks to branch to the pre-exit instead of Succ.
210 // Check that all the in-loop predecessors can be changed.
211 for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
212 PE = Succ->pred_end(); PI != PE; ++PI) {
213 const MachineBasicBlock *Pred = *PI;
214 // The external predecessors won't be altered.
215 if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred))
217 if (!canAnalyzeBranch(Pred))
221 // If Succ's layout predecessor falls through, that too must be analyzable.
222 // We need to insert the pre-exit block in the gap.
223 MachineFunction::const_iterator MFI = Succ;
224 if (MFI == mf_.begin())
226 if (!canAnalyzeBranch(--MFI))
229 // No problems found.
233 void SplitAnalysis::analyze(const LiveInterval *li) {
239 const MachineLoop *SplitAnalysis::getBestSplitLoop() {
240 assert(curli_ && "Call analyze() before getBestSplitLoop");
241 if (usingLoops_.empty())
244 LoopPtrSet Loops, SecondLoops;
246 BlockPtrSet CriticalExits;
248 // Find first-class and second class candidate loops.
249 // We prefer to split around loops where curli is used outside the periphery.
250 for (LoopCountMap::const_iterator I = usingLoops_.begin(),
251 E = usingLoops_.end(); I != E; ++I) {
252 const MachineLoop *Loop = I->first;
253 getLoopBlocks(Loop, Blocks);
255 // FIXME: We need an SSA updater to properly handle multiple exit blocks.
256 if (Blocks.Exits.size() > 1) {
257 DEBUG(dbgs() << " multiple exits from " << *Loop);
262 switch(analyzeLoopPeripheralUse(Blocks)) {
266 case MultiPeripheral:
269 case ContainedInLoop:
270 DEBUG(dbgs() << " contained in " << *Loop);
272 case SinglePeripheral:
273 DEBUG(dbgs() << " single peripheral use in " << *Loop);
276 // Will it be possible to split around this loop?
277 getCriticalExits(Blocks, CriticalExits);
278 DEBUG(dbgs() << " " << CriticalExits.size() << " critical exits from "
280 if (!canSplitCriticalExits(Blocks, CriticalExits))
282 // This is a possible split.
287 DEBUG(dbgs() << " getBestSplitLoop found " << Loops.size() << " + "
288 << SecondLoops.size() << " candidate loops.\n");
290 // If there are no first class loops available, look at second class loops.
297 // Pick the earliest loop.
298 // FIXME: Are there other heuristics to consider?
299 const MachineLoop *Best = 0;
301 for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E;
303 SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader());
304 if (!Best || Idx < BestIdx)
305 Best = *I, BestIdx = Idx;
307 DEBUG(dbgs() << " getBestSplitLoop found " << *Best);
311 /// getMultiUseBlocks - if curli has more than one use in a basic block, it
312 /// may be an advantage to split curli for the duration of the block.
313 bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) {
314 // If curli is local to one block, there is no point to splitting it.
315 if (usingBlocks_.size() <= 1)
317 // Add blocks with multiple uses.
318 for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
325 // It doesn't pay to split a 2-instr block if it redefines curli.
326 VNInfo *VN1 = curli_->getVNInfoAt(lis_.getMBBStartIdx(I->first));
328 curli_->getVNInfoAt(lis_.getMBBEndIdx(I->first).getPrevIndex());
329 // live-in and live-out with a different value.
330 if (VN1 && VN2 && VN1 != VN2)
334 Blocks.insert(I->first);
336 return !Blocks.empty();
339 //===----------------------------------------------------------------------===//
341 //===----------------------------------------------------------------------===//
343 // defValue - Introduce a li_ def for ParentVNI that could be later than
345 VNInfo *LiveIntervalMap::defValue(const VNInfo *ParentVNI, SlotIndex Idx) {
346 assert(ParentVNI && "Mapping NULL value");
347 assert(Idx.isValid() && "Invalid SlotIndex");
348 assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
350 // Is this a simple 1-1 mapping? Not likely.
351 if (Idx == ParentVNI->def)
352 return mapValue(ParentVNI, Idx);
354 // This is a complex def. Mark with a NULL in valueMap.
356 valueMap_.insert(ValueMap::value_type(ParentVNI, 0)).first->second;
358 assert(OldVNI == 0 && "Simple/Complex values mixed");
360 // Should we insert a minimal snippet of VNI LiveRange, or can we count on
361 // callers to do that? We need it for lookups of complex values.
362 VNInfo *VNI = li_.getNextValue(Idx, 0, true, lis_.getVNInfoAllocator());
366 // mapValue - Find the mapped value for ParentVNI at Idx.
367 // Potentially create phi-def values.
368 VNInfo *LiveIntervalMap::mapValue(const VNInfo *ParentVNI, SlotIndex Idx) {
369 assert(ParentVNI && "Mapping NULL value");
370 assert(Idx.isValid() && "Invalid SlotIndex");
371 assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
373 // Use insert for lookup, so we can add missing values with a second lookup.
374 std::pair<ValueMap::iterator,bool> InsP =
375 valueMap_.insert(ValueMap::value_type(ParentVNI, 0));
377 // This was an unknown value. Create a simple mapping.
379 return InsP.first->second = li_.createValueCopy(ParentVNI,
380 lis_.getVNInfoAllocator());
381 // This was a simple mapped value.
382 if (InsP.first->second)
383 return InsP.first->second;
385 // This is a complex mapped value. There may be multiple defs, and we may need
386 // to create phi-defs.
387 MachineBasicBlock *IdxMBB = lis_.getMBBFromIndex(Idx);
388 assert(IdxMBB && "No MBB at Idx");
390 // Is there a def in the same MBB we can extend?
391 if (VNInfo *VNI = extendTo(IdxMBB, Idx))
394 // Now for the fun part. We know that ParentVNI potentially has multiple defs,
395 // and we may need to create even more phi-defs to preserve VNInfo SSA form.
396 // Perform a depth-first search for predecessor blocks where we know the
397 // dominating VNInfo. Insert phi-def VNInfos along the path back to IdxMBB.
399 // Track MBBs where we have created or learned the dominating value.
400 // This may change during the DFS as we create new phi-defs.
401 typedef DenseMap<MachineBasicBlock*, VNInfo*> MBBValueMap;
402 MBBValueMap DomValue;
404 for (idf_iterator<MachineBasicBlock*>
405 IDFI = idf_begin(IdxMBB),
406 IDFE = idf_end(IdxMBB); IDFI != IDFE;) {
407 MachineBasicBlock *MBB = *IDFI;
408 SlotIndex End = lis_.getMBBEndIdx(MBB);
410 // We are operating on the restricted CFG where ParentVNI is live.
411 if (parentli_.getVNInfoAt(End.getPrevSlot()) != ParentVNI) {
416 // Do we have a dominating value in this block?
417 VNInfo *VNI = extendTo(MBB, End);
423 // Yes, VNI dominates MBB. Track the path back to IdxMBB, creating phi-defs
424 // as needed along the way.
425 for (unsigned PI = IDFI.getPathLength()-1; PI != 0; --PI) {
426 // Start from MBB's immediate successor.
427 MachineBasicBlock *Succ = IDFI.getPath(PI-1);
428 std::pair<MBBValueMap::iterator, bool> InsP =
429 DomValue.insert(MBBValueMap::value_type(Succ, VNI));
430 SlotIndex Start = lis_.getMBBStartIdx(Succ);
432 // This is the first time we backtrack to Succ. Verify dominance.
433 if (Succ->pred_size() == 1 || dt_.dominates(MBB, Succ))
435 } else if (InsP.first->second == VNI ||
436 InsP.first->second->def == Start) {
437 // We have previously backtracked VNI to Succ, or Succ already has a
438 // phi-def. No need to backtrack further.
441 // VNI does not dominate Succ, we need a new phi-def.
442 VNI = li_.getNextValue(Start, 0, true, lis_.getVNInfoAllocator());
443 VNI->setIsPHIDef(true);
444 InsP.first->second = VNI;
448 // No need to search the children, we found a dominating value.
449 // MBB is either the found dominating value, or the last phi-def we created.
450 // Either way, the children of MBB would be shadowed, so don't search them.
451 IDFI.skipChildren(MBB);
454 // The search should at least find a dominating value for IdxMBB.
455 assert(!DomValue.empty() && "Couldn't find a reaching definition");
457 // Since we went through the trouble of a full DFS visiting all reaching defs,
458 // the values in DomValue are now accurate. No more phi-defs are needed for
459 // these blocks, so we can color the live ranges.
460 // This makes the next mapValue call much faster.
462 for (MBBValueMap::iterator I = DomValue.begin(), E = DomValue.end(); I != E;
464 MachineBasicBlock *MBB = I->first;
465 VNInfo *VNI = I->second;
466 SlotIndex Start = lis_.getMBBStartIdx(MBB);
468 // Don't add full liveness to IdxMBB, stop at Idx.
470 li_.addRange(LiveRange(Start, Idx, VNI));
473 li_.addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
476 assert(IdxVNI && "Didn't find value for Idx");
480 // extendTo - Find the last li_ value defined in MBB at or before Idx. The
481 // parentli_ is assumed to be live at Idx. Extend the live range to Idx.
482 // Return the found VNInfo, or NULL.
483 VNInfo *LiveIntervalMap::extendTo(MachineBasicBlock *MBB, SlotIndex Idx) {
484 LiveInterval::iterator I = std::upper_bound(li_.begin(), li_.end(), Idx);
485 if (I == li_.begin())
488 if (I->start < lis_.getMBBStartIdx(MBB))
495 // addSimpleRange - Add a simple range from parentli_ to li_.
496 // ParentVNI must be live in the [Start;End) interval.
497 void LiveIntervalMap::addSimpleRange(SlotIndex Start, SlotIndex End,
498 const VNInfo *ParentVNI) {
499 VNInfo *VNI = mapValue(ParentVNI, Start);
500 // A simple mappoing is easy.
501 if (VNI->def == ParentVNI->def) {
502 li_.addRange(LiveRange(Start, End, VNI));
506 // ParentVNI is a complex value. We must map per MBB.
507 MachineFunction::iterator MBB = lis_.getMBBFromIndex(Start);
508 MachineFunction::iterator MBBE = lis_.getMBBFromIndex(End);
511 li_.addRange(LiveRange(Start, End, VNI));
516 li_.addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
518 // Run sequence of full blocks.
519 for (++MBB; MBB != MBBE; ++MBB) {
520 Start = lis_.getMBBStartIdx(MBB);
521 li_.addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB),
522 mapValue(ParentVNI, Start)));
526 Start = lis_.getMBBStartIdx(MBB);
528 li_.addRange(LiveRange(Start, End, mapValue(ParentVNI, Start)));
531 /// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
532 /// All needed values whose def is not inside [Start;End) must be defined
533 /// beforehand so mapValue will work.
534 void LiveIntervalMap::addRange(SlotIndex Start, SlotIndex End) {
535 LiveInterval::const_iterator B = parentli_.begin(), E = parentli_.end();
536 LiveInterval::const_iterator I = std::lower_bound(B, E, Start);
538 // Check if --I begins before Start and overlaps.
542 addSimpleRange(Start, std::min(End, I->end), I->valno);
546 // The remaining ranges begin after Start.
547 for (;I != E && I->start < End; ++I)
548 addSimpleRange(I->start, std::min(End, I->end), I->valno);
551 //===----------------------------------------------------------------------===//
553 //===----------------------------------------------------------------------===//
555 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
556 SplitEditor::SplitEditor(SplitAnalysis &sa, LiveIntervals &lis, VirtRegMap &vrm,
557 SmallVectorImpl<LiveInterval*> &intervals)
558 : sa_(sa), lis_(lis), vrm_(vrm),
559 mri_(vrm.getMachineFunction().getRegInfo()),
560 tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()),
561 curli_(sa_.getCurLI()),
562 dupli_(0), openli_(0),
563 intervals_(intervals),
564 firstInterval(intervals_.size())
566 assert(curli_ && "SplitEditor created from empty SplitAnalysis");
568 // Make sure curli_ is assigned a stack slot, so all our intervals get the
569 // same slot as curli_.
570 if (vrm_.getStackSlot(curli_->reg) == VirtRegMap::NO_STACK_SLOT)
571 vrm_.assignVirt2StackSlot(curli_->reg);
575 LiveInterval *SplitEditor::createInterval() {
576 unsigned curli = sa_.getCurLI()->reg;
577 unsigned Reg = mri_.createVirtualRegister(mri_.getRegClass(curli));
578 LiveInterval &Intv = lis_.getOrCreateInterval(Reg);
580 vrm_.assignVirt2StackSlot(Reg, vrm_.getStackSlot(curli));
584 LiveInterval *SplitEditor::getDupLI() {
586 // Create an interval for dupli that is a copy of curli.
587 dupli_ = createInterval();
588 dupli_->Copy(*curli_, &mri_, lis_.getVNInfoAllocator());
593 VNInfo *SplitEditor::mapValue(const VNInfo *curliVNI) {
594 VNInfo *&VNI = valueMap_[curliVNI];
596 VNI = openli_->createValueCopy(curliVNI, lis_.getVNInfoAllocator());
600 /// Insert a COPY instruction curli -> li. Allocate a new value from li
601 /// defined by the COPY. Note that rewrite() will deal with the curli
602 /// register, so this function can be used to copy from any interval - openli,
604 VNInfo *SplitEditor::insertCopy(LiveInterval &LI,
605 MachineBasicBlock &MBB,
606 MachineBasicBlock::iterator I) {
607 MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY),
608 LI.reg).addReg(curli_->reg);
609 SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
610 return LI.getNextValue(DefIdx, MI, true, lis_.getVNInfoAllocator());
613 /// Create a new virtual register and live interval.
614 void SplitEditor::openIntv() {
615 assert(!openli_ && "Previous LI not closed before openIntv");
616 openli_ = createInterval();
617 intervals_.push_back(openli_);
618 liveThrough_ = false;
621 /// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
622 /// not live before Idx, a COPY is not inserted.
623 void SplitEditor::enterIntvBefore(SlotIndex Idx) {
624 assert(openli_ && "openIntv not called before enterIntvBefore");
626 // Copy from curli_ if it is live.
627 if (VNInfo *CurVNI = curli_->getVNInfoAt(Idx.getUseIndex())) {
628 MachineInstr *MI = lis_.getInstructionFromIndex(Idx);
629 assert(MI && "enterIntvBefore called with invalid index");
630 VNInfo *VNI = insertCopy(*openli_, *MI->getParent(), MI);
631 openli_->addRange(LiveRange(VNI->def, Idx.getDefIndex(), VNI));
633 // Make sure CurVNI is properly mapped.
634 VNInfo *&mapVNI = valueMap_[CurVNI];
635 // We dont have SSA update yet, so only one entry per value is allowed.
636 assert(!mapVNI && "enterIntvBefore called more than once for the same value");
639 DEBUG(dbgs() << " enterIntvBefore " << Idx << ": " << *openli_ << '\n');
642 /// enterIntvAtEnd - Enter openli at the end of MBB.
643 /// PhiMBB is a successor inside openli where a PHI value is created.
644 /// Currently, all entries must share the same PhiMBB.
645 void SplitEditor::enterIntvAtEnd(MachineBasicBlock &A, MachineBasicBlock &B) {
646 assert(openli_ && "openIntv not called before enterIntvAtEnd");
648 SlotIndex EndA = lis_.getMBBEndIdx(&A);
649 VNInfo *CurVNIA = curli_->getVNInfoAt(EndA.getPrevIndex());
651 DEBUG(dbgs() << " enterIntvAtEnd, curli not live out of BB#"
652 << A.getNumber() << ".\n");
656 // Add a phi kill value and live range out of A.
657 VNInfo *VNIA = insertCopy(*openli_, A, A.getFirstTerminator());
658 openli_->addRange(LiveRange(VNIA->def, EndA, VNIA));
660 // FIXME: If this is the only entry edge, we don't need the extra PHI value.
661 // FIXME: If there are multiple entry blocks (so not a loop), we need proper
664 // Now look at the start of B.
665 SlotIndex StartB = lis_.getMBBStartIdx(&B);
666 SlotIndex EndB = lis_.getMBBEndIdx(&B);
667 const LiveRange *CurB = curli_->getLiveRangeContaining(StartB);
669 DEBUG(dbgs() << " enterIntvAtEnd: curli not live in to BB#"
670 << B.getNumber() << ".\n");
674 VNInfo *VNIB = openli_->getVNInfoAt(StartB);
676 // Create a phi value.
677 VNIB = openli_->getNextValue(SlotIndex(StartB, true), 0, false,
678 lis_.getVNInfoAllocator());
679 VNIB->setIsPHIDef(true);
680 VNInfo *&mapVNI = valueMap_[CurB->valno];
682 // Multiple copies - must create PHI value.
685 // This is the first copy of dupLR. Mark the mapping.
691 DEBUG(dbgs() << " enterIntvAtEnd: " << *openli_ << '\n');
694 /// useIntv - indicate that all instructions in MBB should use openli.
695 void SplitEditor::useIntv(const MachineBasicBlock &MBB) {
696 useIntv(lis_.getMBBStartIdx(&MBB), lis_.getMBBEndIdx(&MBB));
699 void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) {
700 assert(openli_ && "openIntv not called before useIntv");
702 // Map the curli values from the interval into openli_
703 LiveInterval::const_iterator B = curli_->begin(), E = curli_->end();
704 LiveInterval::const_iterator I = std::lower_bound(B, E, Start);
708 // I begins before Start, but overlaps.
710 openli_->addRange(LiveRange(Start, std::min(End, I->end),
711 mapValue(I->valno)));
715 // The remaining ranges begin after Start.
716 for (;I != E && I->start < End; ++I)
717 openli_->addRange(LiveRange(I->start, std::min(End, I->end),
718 mapValue(I->valno)));
719 DEBUG(dbgs() << " use [" << Start << ';' << End << "): " << *openli_
723 /// leaveIntvAfter - Leave openli after the instruction at Idx.
724 void SplitEditor::leaveIntvAfter(SlotIndex Idx) {
725 assert(openli_ && "openIntv not called before leaveIntvAfter");
727 const LiveRange *CurLR = curli_->getLiveRangeContaining(Idx.getDefIndex());
728 if (!CurLR || CurLR->end <= Idx.getBoundaryIndex()) {
729 DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": not live\n");
733 // Was this value of curli live through openli?
734 if (!openli_->liveAt(CurLR->valno->def)) {
735 DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": using external value\n");
740 // We are going to insert a back copy, so we must have a dupli_.
741 LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Idx.getDefIndex());
742 assert(DupLR && "dupli not live into black, but curli is?");
744 // Insert the COPY instruction.
745 MachineBasicBlock::iterator I = lis_.getInstructionFromIndex(Idx);
746 MachineInstr *MI = BuildMI(*I->getParent(), llvm::next(I), I->getDebugLoc(),
747 tii_.get(TargetOpcode::COPY), dupli_->reg)
748 .addReg(openli_->reg);
749 SlotIndex CopyIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
750 openli_->addRange(LiveRange(Idx.getDefIndex(), CopyIdx,
751 mapValue(CurLR->valno)));
752 DupLR->valno->def = CopyIdx;
753 DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": " << *openli_ << '\n');
756 /// leaveIntvAtTop - Leave the interval at the top of MBB.
757 /// Currently, only one value can leave the interval.
758 void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
759 assert(openli_ && "openIntv not called before leaveIntvAtTop");
761 SlotIndex Start = lis_.getMBBStartIdx(&MBB);
762 const LiveRange *CurLR = curli_->getLiveRangeContaining(Start);
764 // Is curli even live-in to MBB?
766 DEBUG(dbgs() << " leaveIntvAtTop at " << Start << ": not live\n");
770 // Is curli defined by PHI at the beginning of MBB?
771 bool isPHIDef = CurLR->valno->isPHIDef() &&
772 CurLR->valno->def.getBaseIndex() == Start;
774 // If MBB is using a value of curli that was defined outside the openli range,
775 // we don't want to copy it back here.
776 if (!isPHIDef && !openli_->liveAt(CurLR->valno->def)) {
777 DEBUG(dbgs() << " leaveIntvAtTop at " << Start
778 << ": using external value\n");
783 // We are going to insert a back copy, so we must have a dupli_.
784 LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Start);
785 assert(DupLR && "dupli not live into black, but curli is?");
787 // Insert the COPY instruction.
788 MachineInstr *MI = BuildMI(MBB, MBB.begin(), DebugLoc(),
789 tii_.get(TargetOpcode::COPY), dupli_->reg)
790 .addReg(openli_->reg);
791 SlotIndex Idx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
793 // Adjust dupli and openli values.
795 // dupli was already a PHI on entry to MBB. Simply insert an openli PHI,
796 // and shift the dupli def down to the COPY.
797 VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
798 lis_.getVNInfoAllocator());
799 VNI->setIsPHIDef(true);
800 openli_->addRange(LiveRange(VNI->def, Idx, VNI));
802 dupli_->removeRange(Start, Idx);
803 DupLR->valno->def = Idx;
804 DupLR->valno->setIsPHIDef(false);
806 // The dupli value was defined somewhere inside the openli range.
807 DEBUG(dbgs() << " leaveIntvAtTop source value defined at "
808 << DupLR->valno->def << "\n");
809 // FIXME: We may not need a PHI here if all predecessors have the same
811 VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false,
812 lis_.getVNInfoAllocator());
813 VNI->setIsPHIDef(true);
814 openli_->addRange(LiveRange(VNI->def, Idx, VNI));
816 // FIXME: What if DupLR->valno is used by multiple exits? SSA Update.
818 // closeIntv is going to remove the superfluous live ranges.
819 DupLR->valno->def = Idx;
820 DupLR->valno->setIsPHIDef(false);
823 DEBUG(dbgs() << " leaveIntvAtTop at " << Idx << ": " << *openli_ << '\n');
826 /// closeIntv - Indicate that we are done editing the currently open
827 /// LiveInterval, and ranges can be trimmed.
828 void SplitEditor::closeIntv() {
829 assert(openli_ && "openIntv not called before closeIntv");
831 DEBUG(dbgs() << " closeIntv cleaning up\n");
832 DEBUG(dbgs() << " open " << *openli_ << '\n');
835 DEBUG(dbgs() << " value live through region, leaving dupli as is.\n");
837 // live out with copies inserted, or killed by region. Either way we need to
838 // remove the overlapping region from dupli.
840 for (LiveInterval::iterator I = openli_->begin(), E = openli_->end();
842 dupli_->removeRange(I->start, I->end);
844 // FIXME: A block branching to the entry block may also branch elsewhere
845 // curli is live. We need both openli and curli to be live in that case.
846 DEBUG(dbgs() << " dup2 " << *dupli_ << '\n');
852 /// rewrite - after all the new live ranges have been created, rewrite
853 /// instructions using curli to use the new intervals.
854 void SplitEditor::rewrite() {
855 assert(!openli_ && "Previous LI not closed before rewrite");
856 const LiveInterval *curli = sa_.getCurLI();
857 for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(curli->reg),
858 RE = mri_.reg_end(); RI != RE;) {
859 MachineOperand &MO = RI.getOperand();
860 MachineInstr *MI = MO.getParent();
862 if (MI->isDebugValue()) {
863 DEBUG(dbgs() << "Zapping " << *MI);
864 // FIXME: We can do much better with debug values.
868 SlotIndex Idx = lis_.getInstructionIndex(MI);
869 Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex();
870 LiveInterval *LI = dupli_;
871 for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
872 LiveInterval *testli = intervals_[i];
873 if (testli->liveAt(Idx)) {
881 DEBUG(dbgs() << " rewrite " << Idx << '\t' << *MI);
885 // dupli_ goes in last, after rewriting.
887 if (dupli_->empty()) {
888 DEBUG(dbgs() << " dupli became empty?\n");
889 lis_.removeInterval(dupli_->reg);
892 dupli_->RenumberValues(lis_);
893 intervals_.push_back(dupli_);
897 // Calculate spill weight and allocation hints for new intervals.
898 VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_);
899 for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) {
900 LiveInterval &li = *intervals_[i];
901 vrai.CalculateRegClass(li.reg);
902 vrai.CalculateWeightAndHint(li);
903 DEBUG(dbgs() << " new interval " << mri_.getRegClass(li.reg)->getName()
904 << ":" << li << '\n');
909 //===----------------------------------------------------------------------===//
911 //===----------------------------------------------------------------------===//
913 bool SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
914 SplitAnalysis::LoopBlocks Blocks;
915 sa_.getLoopBlocks(Loop, Blocks);
917 // Break critical edges as needed.
918 SplitAnalysis::BlockPtrSet CriticalExits;
919 sa_.getCriticalExits(Blocks, CriticalExits);
920 assert(CriticalExits.empty() && "Cannot break critical exits yet");
922 // Create new live interval for the loop.
925 // Insert copies in the predecessors.
926 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(),
927 E = Blocks.Preds.end(); I != E; ++I) {
928 MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
929 enterIntvAtEnd(MBB, *Loop->getHeader());
932 // Switch all loop blocks.
933 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(),
934 E = Blocks.Loop.end(); I != E; ++I)
937 // Insert back copies in the exit blocks.
938 for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(),
939 E = Blocks.Exits.end(); I != E; ++I) {
940 MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
951 //===----------------------------------------------------------------------===//
952 // Single Block Splitting
953 //===----------------------------------------------------------------------===//
955 /// splitSingleBlocks - Split curli into a separate live interval inside each
956 /// basic block in Blocks. Return true if curli has been completely replaced,
957 /// false if curli is still intact, and needs to be spilled or split further.
958 bool SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) {
959 DEBUG(dbgs() << " splitSingleBlocks for " << Blocks.size() << " blocks.\n");
960 // Determine the first and last instruction using curli in each block.
961 typedef std::pair<SlotIndex,SlotIndex> IndexPair;
962 typedef DenseMap<const MachineBasicBlock*,IndexPair> IndexPairMap;
963 IndexPairMap MBBRange;
964 for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(),
965 E = sa_.usingInstrs_.end(); I != E; ++I) {
966 const MachineBasicBlock *MBB = (*I)->getParent();
967 if (!Blocks.count(MBB))
969 SlotIndex Idx = lis_.getInstructionIndex(*I);
970 DEBUG(dbgs() << " BB#" << MBB->getNumber() << '\t' << Idx << '\t' << **I);
971 IndexPair &IP = MBBRange[MBB];
972 if (!IP.first.isValid() || Idx < IP.first)
974 if (!IP.second.isValid() || Idx > IP.second)
978 // Create a new interval for each block.
979 for (SplitAnalysis::BlockPtrSet::const_iterator I = Blocks.begin(),
980 E = Blocks.end(); I != E; ++I) {
981 IndexPair &IP = MBBRange[*I];
982 DEBUG(dbgs() << " splitting for BB#" << (*I)->getNumber() << ": ["
983 << IP.first << ';' << IP.second << ")\n");
984 assert(IP.first.isValid() && IP.second.isValid());
987 enterIntvBefore(IP.first);
988 useIntv(IP.first.getBaseIndex(), IP.second.getBoundaryIndex());
989 leaveIntvAfter(IP.second);
997 //===----------------------------------------------------------------------===//
998 // Sub Block Splitting
999 //===----------------------------------------------------------------------===//
1001 /// getBlockForInsideSplit - If curli is contained inside a single basic block,
1002 /// and it wou pay to subdivide the interval inside that block, return it.
1003 /// Otherwise return NULL. The returned block can be passed to
1004 /// SplitEditor::splitInsideBlock.
1005 const MachineBasicBlock *SplitAnalysis::getBlockForInsideSplit() {
1006 // The interval must be exclusive to one block.
1007 if (usingBlocks_.size() != 1)
1009 // Don't to this for less than 4 instructions. We want to be sure that
1010 // splitting actually reduces the instruction count per interval.
1011 if (usingInstrs_.size() < 4)
1013 return usingBlocks_.begin()->first;
1016 /// splitInsideBlock - Split curli into multiple intervals inside MBB. Return
1017 /// true if curli has been completely replaced, false if curli is still
1018 /// intact, and needs to be spilled or split further.
1019 bool SplitEditor::splitInsideBlock(const MachineBasicBlock *MBB) {
1020 SmallVector<SlotIndex, 32> Uses;
1021 Uses.reserve(sa_.usingInstrs_.size());
1022 for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(),
1023 E = sa_.usingInstrs_.end(); I != E; ++I)
1024 if ((*I)->getParent() == MBB)
1025 Uses.push_back(lis_.getInstructionIndex(*I));
1026 DEBUG(dbgs() << " splitInsideBlock BB#" << MBB->getNumber() << " for "
1027 << Uses.size() << " instructions.\n");
1028 assert(Uses.size() >= 3 && "Need at least 3 instructions");
1029 array_pod_sort(Uses.begin(), Uses.end());
1031 // Simple algorithm: Find the largest gap between uses as determined by slot
1032 // indices. Create new intervals for instructions before the gap and after the
1034 unsigned bestPos = 0;
1036 DEBUG(dbgs() << " dist (" << Uses[0]);
1037 for (unsigned i = 1, e = Uses.size(); i != e; ++i) {
1038 int g = Uses[i-1].distance(Uses[i]);
1039 DEBUG(dbgs() << ") -" << g << "- (" << Uses[i]);
1041 bestPos = i, bestGap = g;
1043 DEBUG(dbgs() << "), best: -" << bestGap << "-\n");
1045 // bestPos points to the first use after the best gap.
1046 assert(bestPos > 0 && "Invalid gap");
1048 // FIXME: Don't create intervals for low densities.
1050 // First interval before the gap. Don't create single-instr intervals.
1053 enterIntvBefore(Uses.front());
1054 useIntv(Uses.front().getBaseIndex(), Uses[bestPos-1].getBoundaryIndex());
1055 leaveIntvAfter(Uses[bestPos-1]);
1059 // Second interval after the gap.
1060 if (bestPos < Uses.size()-1) {
1062 enterIntvBefore(Uses[bestPos]);
1063 useIntv(Uses[bestPos].getBaseIndex(), Uses.back().getBoundaryIndex());
1064 leaveIntvAfter(Uses.back());