1 //===-- LiveIntervalAnalysis.cpp - Live Interval Analysis -----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the 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.
16 //===----------------------------------------------------------------------===//
18 #define DEBUG_TYPE "liveintervals"
19 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
20 #include "VirtRegMap.h"
21 #include "llvm/Value.h"
22 #include "llvm/Analysis/LoopInfo.h"
23 #include "llvm/CodeGen/LiveVariables.h"
24 #include "llvm/CodeGen/MachineFrameInfo.h"
25 #include "llvm/CodeGen/MachineInstr.h"
26 #include "llvm/CodeGen/Passes.h"
27 #include "llvm/CodeGen/SSARegMap.h"
28 #include "llvm/Target/MRegisterInfo.h"
29 #include "llvm/Target/TargetInstrInfo.h"
30 #include "llvm/Target/TargetMachine.h"
31 #include "llvm/Support/CommandLine.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/ADT/Statistic.h"
34 #include "llvm/ADT/STLExtras.h"
39 STATISTIC(numIntervals, "Number of original intervals");
40 STATISTIC(numIntervalsAfter, "Number of intervals after coalescing");
41 STATISTIC(numJoins , "Number of interval joins performed");
42 STATISTIC(numPeep , "Number of identity moves eliminated after coalescing");
43 STATISTIC(numFolded , "Number of loads/stores folded into instructions");
44 STATISTIC(numAborts , "Number of times interval joining aborted");
47 RegisterPass<LiveIntervals> X("liveintervals", "Live Interval Analysis");
50 EnableJoining("join-liveintervals",
51 cl::desc("Coallesce copies (default=true)"),
55 EnableReMat("enable-rematerialization",
56 cl::desc("Perform trivial re-materialization"),
60 void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
61 AU.addRequired<LiveVariables>();
62 AU.addPreservedID(PHIEliminationID);
63 AU.addRequiredID(PHIEliminationID);
64 AU.addRequiredID(TwoAddressInstructionPassID);
65 AU.addRequired<LoopInfo>();
66 MachineFunctionPass::getAnalysisUsage(AU);
69 void LiveIntervals::releaseMemory() {
78 static bool isZeroLengthInterval(LiveInterval *li) {
79 for (LiveInterval::Ranges::const_iterator
80 i = li->ranges.begin(), e = li->ranges.end(); i != e; ++i)
81 if (i->end - i->start > LiveIntervals::InstrSlots::NUM)
87 /// runOnMachineFunction - Register allocate the whole function
89 bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
91 tm_ = &fn.getTarget();
92 mri_ = tm_->getRegisterInfo();
93 tii_ = tm_->getInstrInfo();
94 lv_ = &getAnalysis<LiveVariables>();
95 allocatableRegs_ = mri_->getAllocatableSet(fn);
96 r2rMap_.grow(mf_->getSSARegMap()->getLastVirtReg());
98 // Number MachineInstrs and MachineBasicBlocks.
99 // Initialize MBB indexes to a sentinal.
100 MBB2IdxMap.resize(mf_->getNumBlockIDs(), ~0U);
102 unsigned MIIndex = 0;
103 for (MachineFunction::iterator MBB = mf_->begin(), E = mf_->end();
105 // Set the MBB2IdxMap entry for this MBB.
106 MBB2IdxMap[MBB->getNumber()] = MIIndex;
108 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
110 bool inserted = mi2iMap_.insert(std::make_pair(I, MIIndex)).second;
111 assert(inserted && "multiple MachineInstr -> index mappings");
112 i2miMap_.push_back(I);
113 MIIndex += InstrSlots::NUM;
119 numIntervals += getNumIntervals();
121 DOUT << "********** INTERVALS **********\n";
122 for (iterator I = begin(), E = end(); I != E; ++I) {
123 I->second.print(DOUT, mri_);
127 // Join (coallesce) intervals if requested.
128 if (EnableJoining) joinIntervals();
130 numIntervalsAfter += getNumIntervals();
133 // perform a final pass over the instructions and compute spill
134 // weights, coalesce virtual registers and remove identity moves.
135 const LoopInfo &loopInfo = getAnalysis<LoopInfo>();
137 for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
138 mbbi != mbbe; ++mbbi) {
139 MachineBasicBlock* mbb = mbbi;
140 unsigned loopDepth = loopInfo.getLoopDepth(mbb->getBasicBlock());
142 for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
144 // if the move will be an identity move delete it
145 unsigned srcReg, dstReg, RegRep;
146 if (tii_->isMoveInstr(*mii, srcReg, dstReg) &&
147 (RegRep = rep(srcReg)) == rep(dstReg)) {
148 // remove from def list
149 LiveInterval &RegInt = getOrCreateInterval(RegRep);
150 MachineOperand *MO = mii->findRegisterDefOperand(dstReg);
151 // If def of this move instruction is dead, remove its live range from
152 // the dstination register's live interval.
154 unsigned MoveIdx = getDefIndex(getInstructionIndex(mii));
155 LiveInterval::iterator MLR = RegInt.FindLiveRangeContaining(MoveIdx);
156 RegInt.removeRange(MLR->start, MoveIdx+1);
158 removeInterval(RegRep);
160 RemoveMachineInstrFromMaps(mii);
161 mii = mbbi->erase(mii);
164 for (unsigned i = 0, e = mii->getNumOperands(); i != e; ++i) {
165 const MachineOperand &mop = mii->getOperand(i);
166 if (mop.isRegister() && mop.getReg() &&
167 MRegisterInfo::isVirtualRegister(mop.getReg())) {
168 // replace register with representative register
169 unsigned reg = rep(mop.getReg());
170 mii->getOperand(i).setReg(reg);
172 // If the definition instruction is re-materializable, its spill
174 LiveInterval &RegInt = getInterval(reg);
177 (mop.isUse() + mop.isDef()) * pow(10.0F, (int)loopDepth);
186 for (iterator I = begin(), E = end(); I != E; ++I) {
187 LiveInterval &LI = I->second;
188 if (MRegisterInfo::isVirtualRegister(LI.reg)) {
189 // If the live interval length is essentially zero, i.e. in every live
190 // range the use follows def immediately, it doesn't make sense to spill
191 // it and hope it will be easier to allocate for this li.
192 if (isZeroLengthInterval(&LI))
193 LI.weight = HUGE_VALF;
195 // Divide the weight of the interval by its size. This encourages
196 // spilling of intervals that are large and have few uses, and
197 // discourages spilling of small intervals with many uses.
199 for (LiveInterval::iterator II = LI.begin(), E = LI.end(); II != E;++II)
200 Size += II->end - II->start;
210 /// print - Implement the dump method.
211 void LiveIntervals::print(std::ostream &O, const Module* ) const {
212 O << "********** INTERVALS **********\n";
213 for (const_iterator I = begin(), E = end(); I != E; ++I) {
214 I->second.print(DOUT, mri_);
218 O << "********** MACHINEINSTRS **********\n";
219 for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
220 mbbi != mbbe; ++mbbi) {
221 O << ((Value*)mbbi->getBasicBlock())->getName() << ":\n";
222 for (MachineBasicBlock::iterator mii = mbbi->begin(),
223 mie = mbbi->end(); mii != mie; ++mii) {
224 O << getInstructionIndex(mii) << '\t' << *mii;
229 /// CreateNewLiveInterval - Create a new live interval with the given live
230 /// ranges. The new live interval will have an infinite spill weight.
232 LiveIntervals::CreateNewLiveInterval(const LiveInterval *LI,
233 const std::vector<LiveRange> &LRs) {
234 const TargetRegisterClass *RC = mf_->getSSARegMap()->getRegClass(LI->reg);
236 // Create a new virtual register for the spill interval.
237 unsigned NewVReg = mf_->getSSARegMap()->createVirtualRegister(RC);
239 // Replace the old virtual registers in the machine operands with the shiny
241 for (std::vector<LiveRange>::const_iterator
242 I = LRs.begin(), E = LRs.end(); I != E; ++I) {
243 unsigned Index = getBaseIndex(I->start);
244 unsigned End = getBaseIndex(I->end - 1) + InstrSlots::NUM;
246 for (; Index != End; Index += InstrSlots::NUM) {
247 // Skip deleted instructions
248 while (Index != End && !getInstructionFromIndex(Index))
249 Index += InstrSlots::NUM;
251 if (Index == End) break;
253 MachineInstr *MI = getInstructionFromIndex(Index);
255 for (unsigned J = 0, e = MI->getNumOperands(); J != e; ++J) {
256 MachineOperand &MOp = MI->getOperand(J);
257 if (MOp.isRegister() && rep(MOp.getReg()) == LI->reg)
263 LiveInterval &NewLI = getOrCreateInterval(NewVReg);
265 // The spill weight is now infinity as it cannot be spilled again
266 NewLI.weight = float(HUGE_VAL);
268 for (std::vector<LiveRange>::const_iterator
269 I = LRs.begin(), E = LRs.end(); I != E; ++I) {
270 DOUT << " Adding live range " << *I << " to new interval\n";
274 DOUT << "Created new live interval " << NewLI << "\n";
278 std::vector<LiveInterval*> LiveIntervals::
279 addIntervalsForSpills(const LiveInterval &li, VirtRegMap &vrm, int slot) {
280 // since this is called after the analysis is done we don't know if
281 // LiveVariables is available
282 lv_ = getAnalysisToUpdate<LiveVariables>();
284 std::vector<LiveInterval*> added;
286 assert(li.weight != HUGE_VALF &&
287 "attempt to spill already spilled interval!");
289 DOUT << "\t\t\t\tadding intervals for spills for interval: ";
290 li.print(DOUT, mri_);
293 const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(li.reg);
295 for (LiveInterval::Ranges::const_iterator
296 i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
297 unsigned index = getBaseIndex(i->start);
298 unsigned end = getBaseIndex(i->end-1) + InstrSlots::NUM;
299 for (; index != end; index += InstrSlots::NUM) {
300 // skip deleted instructions
301 while (index != end && !getInstructionFromIndex(index))
302 index += InstrSlots::NUM;
303 if (index == end) break;
305 MachineInstr *MI = getInstructionFromIndex(index);
308 for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
309 MachineOperand& mop = MI->getOperand(i);
310 if (mop.isRegister() && mop.getReg() == li.reg) {
311 MachineInstr *fmi = li.remat ? NULL
312 : mri_->foldMemoryOperand(MI, i, slot);
314 // Attempt to fold the memory reference into the instruction. If we
315 // can do this, we don't need to insert spill code.
317 lv_->instructionChanged(MI, fmi);
318 MachineBasicBlock &MBB = *MI->getParent();
319 vrm.virtFolded(li.reg, MI, i, fmi);
321 i2miMap_[index/InstrSlots::NUM] = fmi;
322 mi2iMap_[fmi] = index;
323 MI = MBB.insert(MBB.erase(MI), fmi);
325 // Folding the load/store can completely change the instruction in
326 // unpredictable ways, rescan it from the beginning.
327 goto RestartInstruction;
329 // Create a new virtual register for the spill interval.
330 unsigned NewVReg = mf_->getSSARegMap()->createVirtualRegister(rc);
332 // Scan all of the operands of this instruction rewriting operands
333 // to use NewVReg instead of li.reg as appropriate. We do this for
336 // 1. If the instr reads the same spilled vreg multiple times, we
337 // want to reuse the NewVReg.
338 // 2. If the instr is a two-addr instruction, we are required to
339 // keep the src/dst regs pinned.
341 // Keep track of whether we replace a use and/or def so that we can
342 // create the spill interval with the appropriate range.
345 bool HasUse = mop.isUse();
346 bool HasDef = mop.isDef();
347 for (unsigned j = i+1, e = MI->getNumOperands(); j != e; ++j) {
348 if (MI->getOperand(j).isReg() &&
349 MI->getOperand(j).getReg() == li.reg) {
350 MI->getOperand(j).setReg(NewVReg);
351 HasUse |= MI->getOperand(j).isUse();
352 HasDef |= MI->getOperand(j).isDef();
356 // create a new register for this spill
359 vrm.setVirtIsReMaterialized(NewVReg, li.remat);
360 vrm.assignVirt2StackSlot(NewVReg, slot);
361 LiveInterval &nI = getOrCreateInterval(NewVReg);
365 // the spill weight is now infinity as it
366 // cannot be spilled again
367 nI.weight = HUGE_VALF;
370 LiveRange LR(getLoadIndex(index), getUseIndex(index),
371 nI.getNextValue(~0U, 0));
376 LiveRange LR(getDefIndex(index), getStoreIndex(index),
377 nI.getNextValue(~0U, 0));
382 added.push_back(&nI);
384 // update live variables if it is available
386 lv_->addVirtualRegisterKilled(NewVReg, MI);
388 DOUT << "\t\t\t\tadded new interval: ";
389 nI.print(DOUT, mri_);
400 void LiveIntervals::printRegName(unsigned reg) const {
401 if (MRegisterInfo::isPhysicalRegister(reg))
402 cerr << mri_->getName(reg);
404 cerr << "%reg" << reg;
407 /// isReDefinedByTwoAddr - Returns true if the Reg re-definition is due to
408 /// two addr elimination.
409 static bool isReDefinedByTwoAddr(MachineInstr *MI, unsigned Reg,
410 const TargetInstrInfo *TII) {
411 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
412 MachineOperand &MO1 = MI->getOperand(i);
413 if (MO1.isRegister() && MO1.isDef() && MO1.getReg() == Reg) {
414 for (unsigned j = i+1; j < e; ++j) {
415 MachineOperand &MO2 = MI->getOperand(j);
416 if (MO2.isRegister() && MO2.isUse() && MO2.getReg() == Reg &&
417 MI->getInstrDescriptor()->
418 getOperandConstraint(j, TOI::TIED_TO) == (int)i)
426 void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
427 MachineBasicBlock::iterator mi,
429 LiveInterval &interval) {
430 DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg));
431 LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
433 // Virtual registers may be defined multiple times (due to phi
434 // elimination and 2-addr elimination). Much of what we do only has to be
435 // done once for the vreg. We use an empty interval to detect the first
436 // time we see a vreg.
437 if (interval.empty()) {
438 // Remember if the definition can be rematerialized.
440 vi.DefInst && tii_->isReMaterializable(vi.DefInst->getOpcode()))
441 interval.remat = vi.DefInst;
443 // Get the Idx of the defining instructions.
444 unsigned defIndex = getDefIndex(MIIdx);
447 unsigned SrcReg, DstReg;
448 if (!tii_->isMoveInstr(*mi, SrcReg, DstReg))
449 ValNum = interval.getNextValue(~0U, 0);
451 ValNum = interval.getNextValue(defIndex, SrcReg);
453 assert(ValNum == 0 && "First value in interval is not 0?");
454 ValNum = 0; // Clue in the optimizer.
456 // Loop over all of the blocks that the vreg is defined in. There are
457 // two cases we have to handle here. The most common case is a vreg
458 // whose lifetime is contained within a basic block. In this case there
459 // will be a single kill, in MBB, which comes after the definition.
460 if (vi.Kills.size() == 1 && vi.Kills[0]->getParent() == mbb) {
461 // FIXME: what about dead vars?
463 if (vi.Kills[0] != mi)
464 killIdx = getUseIndex(getInstructionIndex(vi.Kills[0]))+1;
466 killIdx = defIndex+1;
468 // If the kill happens after the definition, we have an intra-block
470 if (killIdx > defIndex) {
471 assert(vi.AliveBlocks.none() &&
472 "Shouldn't be alive across any blocks!");
473 LiveRange LR(defIndex, killIdx, ValNum);
474 interval.addRange(LR);
475 DOUT << " +" << LR << "\n";
480 // The other case we handle is when a virtual register lives to the end
481 // of the defining block, potentially live across some blocks, then is
482 // live into some number of blocks, but gets killed. Start by adding a
483 // range that goes from this definition to the end of the defining block.
484 LiveRange NewLR(defIndex,
485 getInstructionIndex(&mbb->back()) + InstrSlots::NUM,
487 DOUT << " +" << NewLR;
488 interval.addRange(NewLR);
490 // Iterate over all of the blocks that the variable is completely
491 // live in, adding [insrtIndex(begin), instrIndex(end)+4) to the
493 for (unsigned i = 0, e = vi.AliveBlocks.size(); i != e; ++i) {
494 if (vi.AliveBlocks[i]) {
495 MachineBasicBlock *MBB = mf_->getBlockNumbered(i);
497 LiveRange LR(getMBBStartIdx(i),
498 getInstructionIndex(&MBB->back()) + InstrSlots::NUM,
500 interval.addRange(LR);
506 // Finally, this virtual register is live from the start of any killing
507 // block to the 'use' slot of the killing instruction.
508 for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) {
509 MachineInstr *Kill = vi.Kills[i];
510 LiveRange LR(getMBBStartIdx(Kill->getParent()),
511 getUseIndex(getInstructionIndex(Kill))+1,
513 interval.addRange(LR);
518 // Can't safely assume definition is rematierializable anymore.
519 interval.remat = NULL;
521 // If this is the second time we see a virtual register definition, it
522 // must be due to phi elimination or two addr elimination. If this is
523 // the result of two address elimination, then the vreg is one of the
524 // def-and-use register operand.
525 if (isReDefinedByTwoAddr(mi, interval.reg, tii_)) {
526 // If this is a two-address definition, then we have already processed
527 // the live range. The only problem is that we didn't realize there
528 // are actually two values in the live interval. Because of this we
529 // need to take the LiveRegion that defines this register and split it
531 unsigned DefIndex = getDefIndex(getInstructionIndex(vi.DefInst));
532 unsigned RedefIndex = getDefIndex(MIIdx);
534 // Delete the initial value, which should be short and continuous,
535 // because the 2-addr copy must be in the same MBB as the redef.
536 interval.removeRange(DefIndex, RedefIndex);
538 // Two-address vregs should always only be redefined once. This means
539 // that at this point, there should be exactly one value number in it.
540 assert(interval.containsOneValue() && "Unexpected 2-addr liveint!");
542 // The new value number (#1) is defined by the instruction we claimed
544 unsigned ValNo = interval.getNextValue(0, 0);
545 interval.setValueNumberInfo(1, interval.getValNumInfo(0));
547 // Value#0 is now defined by the 2-addr instruction.
548 interval.setValueNumberInfo(0, std::make_pair(~0U, 0U));
550 // Add the new live interval which replaces the range for the input copy.
551 LiveRange LR(DefIndex, RedefIndex, ValNo);
552 DOUT << " replace range with " << LR;
553 interval.addRange(LR);
555 // If this redefinition is dead, we need to add a dummy unit live
556 // range covering the def slot.
557 if (lv_->RegisterDefIsDead(mi, interval.reg))
558 interval.addRange(LiveRange(RedefIndex, RedefIndex+1, 0));
561 interval.print(DOUT, mri_);
564 // Otherwise, this must be because of phi elimination. If this is the
565 // first redefinition of the vreg that we have seen, go back and change
566 // the live range in the PHI block to be a different value number.
567 if (interval.containsOneValue()) {
568 assert(vi.Kills.size() == 1 &&
569 "PHI elimination vreg should have one kill, the PHI itself!");
571 // Remove the old range that we now know has an incorrect number.
572 MachineInstr *Killer = vi.Kills[0];
573 unsigned Start = getMBBStartIdx(Killer->getParent());
574 unsigned End = getUseIndex(getInstructionIndex(Killer))+1;
575 DOUT << " Removing [" << Start << "," << End << "] from: ";
576 interval.print(DOUT, mri_); DOUT << "\n";
577 interval.removeRange(Start, End);
578 DOUT << " RESULT: "; interval.print(DOUT, mri_);
580 // Replace the interval with one of a NEW value number. Note that this
581 // value number isn't actually defined by an instruction, weird huh? :)
582 LiveRange LR(Start, End, interval.getNextValue(~0U, 0));
583 DOUT << " replace range with " << LR;
584 interval.addRange(LR);
585 DOUT << " RESULT: "; interval.print(DOUT, mri_);
588 // In the case of PHI elimination, each variable definition is only
589 // live until the end of the block. We've already taken care of the
590 // rest of the live range.
591 unsigned defIndex = getDefIndex(MIIdx);
594 unsigned SrcReg, DstReg;
595 if (!tii_->isMoveInstr(*mi, SrcReg, DstReg))
596 ValNum = interval.getNextValue(~0U, 0);
598 ValNum = interval.getNextValue(defIndex, SrcReg);
600 LiveRange LR(defIndex,
601 getInstructionIndex(&mbb->back()) + InstrSlots::NUM, ValNum);
602 interval.addRange(LR);
610 void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
611 MachineBasicBlock::iterator mi,
613 LiveInterval &interval,
615 // A physical register cannot be live across basic block, so its
616 // lifetime must end somewhere in its defining basic block.
617 DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg));
619 unsigned baseIndex = MIIdx;
620 unsigned start = getDefIndex(baseIndex);
621 unsigned end = start;
623 // If it is not used after definition, it is considered dead at
624 // the instruction defining it. Hence its interval is:
625 // [defSlot(def), defSlot(def)+1)
626 if (lv_->RegisterDefIsDead(mi, interval.reg)) {
628 end = getDefIndex(start) + 1;
632 // If it is not dead on definition, it must be killed by a
633 // subsequent instruction. Hence its interval is:
634 // [defSlot(def), useSlot(kill)+1)
635 while (++mi != MBB->end()) {
636 baseIndex += InstrSlots::NUM;
637 if (lv_->KillsRegister(mi, interval.reg)) {
639 end = getUseIndex(baseIndex) + 1;
641 } else if (lv_->ModifiesRegister(mi, interval.reg)) {
642 // Another instruction redefines the register before it is ever read.
643 // Then the register is essentially dead at the instruction that defines
644 // it. Hence its interval is:
645 // [defSlot(def), defSlot(def)+1)
647 end = getDefIndex(start) + 1;
652 // The only case we should have a dead physreg here without a killing or
653 // instruction where we know it's dead is if it is live-in to the function
655 assert(!SrcReg && "physreg was not killed in defining block!");
656 end = getDefIndex(start) + 1; // It's dead.
659 assert(start < end && "did not find end of interval?");
661 LiveRange LR(start, end, interval.getNextValue(SrcReg != 0 ? start : ~0U,
663 interval.addRange(LR);
664 DOUT << " +" << LR << '\n';
667 void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB,
668 MachineBasicBlock::iterator MI,
671 if (MRegisterInfo::isVirtualRegister(reg))
672 handleVirtualRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg));
673 else if (allocatableRegs_[reg]) {
674 unsigned SrcReg, DstReg;
675 if (!tii_->isMoveInstr(*MI, SrcReg, DstReg))
677 handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg), SrcReg);
678 for (const unsigned* AS = mri_->getAliasSet(reg); *AS; ++AS)
679 handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(*AS), 0);
683 void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
685 LiveInterval &interval) {
686 DOUT << "\t\tlivein register: "; DEBUG(printRegName(interval.reg));
688 // Look for kills, if it reaches a def before it's killed, then it shouldn't
689 // be considered a livein.
690 MachineBasicBlock::iterator mi = MBB->begin();
691 unsigned baseIndex = MIIdx;
692 unsigned start = baseIndex;
693 unsigned end = start;
694 while (mi != MBB->end()) {
695 if (lv_->KillsRegister(mi, interval.reg)) {
697 end = getUseIndex(baseIndex) + 1;
699 } else if (lv_->ModifiesRegister(mi, interval.reg)) {
700 // Another instruction redefines the register before it is ever read.
701 // Then the register is essentially dead at the instruction that defines
702 // it. Hence its interval is:
703 // [defSlot(def), defSlot(def)+1)
705 end = getDefIndex(start) + 1;
709 baseIndex += InstrSlots::NUM;
714 assert(start < end && "did not find end of interval?");
716 LiveRange LR(start, end, interval.getNextValue(~0U, 0));
717 DOUT << " +" << LR << '\n';
718 interval.addRange(LR);
721 /// computeIntervals - computes the live intervals for virtual
722 /// registers. for some ordering of the machine instructions [1,N] a
723 /// live interval is an interval [i, j) where 1 <= i <= j < N for
724 /// which a variable is live
725 void LiveIntervals::computeIntervals() {
726 DOUT << "********** COMPUTING LIVE INTERVALS **********\n"
727 << "********** Function: "
728 << ((Value*)mf_->getFunction())->getName() << '\n';
729 // Track the index of the current machine instr.
730 unsigned MIIndex = 0;
731 for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end();
733 MachineBasicBlock *MBB = MBBI;
734 DOUT << ((Value*)MBB->getBasicBlock())->getName() << ":\n";
736 MachineBasicBlock::iterator MI = MBB->begin(), miEnd = MBB->end();
738 if (MBB->livein_begin() != MBB->livein_end()) {
739 // Create intervals for live-ins to this BB first.
740 for (MachineBasicBlock::const_livein_iterator LI = MBB->livein_begin(),
741 LE = MBB->livein_end(); LI != LE; ++LI) {
742 handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI));
743 for (const unsigned* AS = mri_->getAliasSet(*LI); *AS; ++AS)
744 handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS));
748 for (; MI != miEnd; ++MI) {
749 DOUT << MIIndex << "\t" << *MI;
752 for (int i = MI->getNumOperands() - 1; i >= 0; --i) {
753 MachineOperand &MO = MI->getOperand(i);
754 // handle register defs - build intervals
755 if (MO.isRegister() && MO.getReg() && MO.isDef())
756 handleRegisterDef(MBB, MI, MIIndex, MO.getReg());
759 MIIndex += InstrSlots::NUM;
764 /// AdjustCopiesBackFrom - We found a non-trivially-coallescable copy with IntA
765 /// being the source and IntB being the dest, thus this defines a value number
766 /// in IntB. If the source value number (in IntA) is defined by a copy from B,
767 /// see if we can merge these two pieces of B into a single value number,
768 /// eliminating a copy. For example:
772 /// B1 = A3 <- this copy
774 /// In this case, B0 can be extended to where the B1 copy lives, allowing the B1
775 /// value number to be replaced with B0 (which simplifies the B liveinterval).
777 /// This returns true if an interval was modified.
779 bool LiveIntervals::AdjustCopiesBackFrom(LiveInterval &IntA, LiveInterval &IntB,
780 MachineInstr *CopyMI) {
781 unsigned CopyIdx = getDefIndex(getInstructionIndex(CopyMI));
783 // BValNo is a value number in B that is defined by a copy from A. 'B3' in
784 // the example above.
785 LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);
786 unsigned BValNo = BLR->ValId;
788 // Get the location that B is defined at. Two options: either this value has
789 // an unknown definition point or it is defined at CopyIdx. If unknown, we
791 unsigned BValNoDefIdx = IntB.getInstForValNum(BValNo);
792 if (BValNoDefIdx == ~0U) return false;
793 assert(BValNoDefIdx == CopyIdx &&
794 "Copy doesn't define the value?");
796 // AValNo is the value number in A that defines the copy, A0 in the example.
797 LiveInterval::iterator AValLR = IntA.FindLiveRangeContaining(CopyIdx-1);
798 unsigned AValNo = AValLR->ValId;
800 // If AValNo is defined as a copy from IntB, we can potentially process this.
802 // Get the instruction that defines this value number.
803 unsigned SrcReg = IntA.getSrcRegForValNum(AValNo);
804 if (!SrcReg) return false; // Not defined by a copy.
806 // If the value number is not defined by a copy instruction, ignore it.
808 // If the source register comes from an interval other than IntB, we can't
810 if (rep(SrcReg) != IntB.reg) return false;
812 // Get the LiveRange in IntB that this value number starts with.
813 unsigned AValNoInstIdx = IntA.getInstForValNum(AValNo);
814 LiveInterval::iterator ValLR = IntB.FindLiveRangeContaining(AValNoInstIdx-1);
816 // Make sure that the end of the live range is inside the same block as
818 MachineInstr *ValLREndInst = getInstructionFromIndex(ValLR->end-1);
820 ValLREndInst->getParent() != CopyMI->getParent()) return false;
822 // Okay, we now know that ValLR ends in the same block that the CopyMI
823 // live-range starts. If there are no intervening live ranges between them in
824 // IntB, we can merge them.
825 if (ValLR+1 != BLR) return false;
827 DOUT << "\nExtending: "; IntB.print(DOUT, mri_);
829 // We are about to delete CopyMI, so need to remove it as the 'instruction
830 // that defines this value #'.
831 IntB.setValueNumberInfo(BValNo, std::make_pair(~0U, 0));
833 // Okay, we can merge them. We need to insert a new liverange:
834 // [ValLR.end, BLR.begin) of either value number, then we merge the
835 // two value numbers.
836 unsigned FillerStart = ValLR->end, FillerEnd = BLR->start;
837 IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo));
839 // If the IntB live range is assigned to a physical register, and if that
840 // physreg has aliases,
841 if (MRegisterInfo::isPhysicalRegister(IntB.reg)) {
842 for (const unsigned *AS = mri_->getAliasSet(IntB.reg); *AS; ++AS) {
843 LiveInterval &AliasLI = getInterval(*AS);
844 AliasLI.addRange(LiveRange(FillerStart, FillerEnd,
845 AliasLI.getNextValue(~0U, 0)));
849 // Okay, merge "B1" into the same value number as "B0".
850 if (BValNo != ValLR->ValId)
851 IntB.MergeValueNumberInto(BValNo, ValLR->ValId);
852 DOUT << " result = "; IntB.print(DOUT, mri_);
855 // If the source instruction was killing the source register before the
856 // merge, unset the isKill marker given the live range has been extended.
857 int UIdx = ValLREndInst->findRegisterUseOperand(IntB.reg, true);
859 ValLREndInst->getOperand(UIdx).unsetIsKill();
861 // Finally, delete the copy instruction.
862 RemoveMachineInstrFromMaps(CopyMI);
863 CopyMI->eraseFromParent();
868 /// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
869 /// which are the src/dst of the copy instruction CopyMI. This returns true
870 /// if the copy was successfully coallesced away, or if it is never possible
871 /// to coallesce these this copy, due to register constraints. It returns
872 /// false if it is not currently possible to coallesce this interval, but
873 /// it may be possible if other things get coallesced.
874 bool LiveIntervals::JoinCopy(MachineInstr *CopyMI,
875 unsigned SrcReg, unsigned DstReg) {
876 DOUT << getInstructionIndex(CopyMI) << '\t' << *CopyMI;
878 // Get representative registers.
879 unsigned repSrcReg = rep(SrcReg);
880 unsigned repDstReg = rep(DstReg);
882 // If they are already joined we continue.
883 if (repSrcReg == repDstReg) {
884 DOUT << "\tCopy already coallesced.\n";
885 return true; // Not coallescable.
888 // If they are both physical registers, we cannot join them.
889 if (MRegisterInfo::isPhysicalRegister(repSrcReg) &&
890 MRegisterInfo::isPhysicalRegister(repDstReg)) {
891 DOUT << "\tCan not coallesce physregs.\n";
892 return true; // Not coallescable.
895 // We only join virtual registers with allocatable physical registers.
896 if (MRegisterInfo::isPhysicalRegister(repSrcReg) &&
897 !allocatableRegs_[repSrcReg]) {
898 DOUT << "\tSrc reg is unallocatable physreg.\n";
899 return true; // Not coallescable.
901 if (MRegisterInfo::isPhysicalRegister(repDstReg) &&
902 !allocatableRegs_[repDstReg]) {
903 DOUT << "\tDst reg is unallocatable physreg.\n";
904 return true; // Not coallescable.
907 // If they are not of the same register class, we cannot join them.
908 if (differingRegisterClasses(repSrcReg, repDstReg)) {
909 DOUT << "\tSrc/Dest are different register classes.\n";
910 return true; // Not coallescable.
913 LiveInterval &SrcInt = getInterval(repSrcReg);
914 LiveInterval &DestInt = getInterval(repDstReg);
915 assert(SrcInt.reg == repSrcReg && DestInt.reg == repDstReg &&
916 "Register mapping is horribly broken!");
918 DOUT << "\t\tInspecting "; SrcInt.print(DOUT, mri_);
919 DOUT << " and "; DestInt.print(DOUT, mri_);
922 // Check if it is necessary to propagate "isDead" property before intervals
924 MachineOperand *mopd = CopyMI->findRegisterDefOperand(DstReg);
925 bool isDead = mopd->isDead();
926 bool isShorten = false;
927 unsigned SrcStart = 0, RemoveStart = 0;
928 unsigned SrcEnd = 0, RemoveEnd = 0;
930 unsigned CopyIdx = getInstructionIndex(CopyMI);
931 LiveInterval::iterator SrcLR =
932 SrcInt.FindLiveRangeContaining(getUseIndex(CopyIdx));
933 RemoveStart = SrcStart = SrcLR->start;
934 RemoveEnd = SrcEnd = SrcLR->end;
935 // The instruction which defines the src is only truly dead if there are
936 // no intermediate uses and there isn't a use beyond the copy.
937 // FIXME: find the last use, mark is kill and shorten the live range.
938 if (SrcEnd > getDefIndex(CopyIdx)) {
942 MachineInstr *LastUse= lastRegisterUse(repSrcReg, SrcStart, CopyIdx, MOU);
944 // Shorten the liveinterval to the end of last use.
948 RemoveStart = getDefIndex(getInstructionIndex(LastUse));
950 } else if (RemoveStart > 0)
951 // A dead def should have a single cycle interval.
956 // We need to be careful about coalescing a source physical register with a
957 // virtual register. Once the coalescing is done, it cannot be broken and
958 // these are not spillable! If the destination interval uses are far away,
959 // think twice about coalescing them!
960 if (!mopd->isDead() && MRegisterInfo::isPhysicalRegister(repSrcReg)) {
961 // Small function. No need to worry!
962 unsigned Threshold = allocatableRegs_.count() * 2;
963 if (r2iMap_.size() <= Threshold)
966 LiveVariables::VarInfo& dvi = lv_->getVarInfo(repDstReg);
967 // Is the value used in the current BB or any immediate successroe BB?
968 MachineBasicBlock *CopyBB = CopyMI->getParent();
969 if (dvi.UsedBlocks[CopyBB->getNumber()])
971 for (MachineBasicBlock::succ_iterator SI = CopyBB->succ_begin(),
972 SE = CopyBB->succ_end(); SI != SE; ++SI) {
973 MachineBasicBlock *SuccMBB = *SI;
974 if (dvi.UsedBlocks[SuccMBB->getNumber()])
978 // Ok, no use in this BB and no use in immediate successor BB's. Be really
980 // It's only used in one BB, forget about it!
981 if (dvi.UsedBlocks.count() < 2) {
986 // Determine whether to allow coalescing based on how far the closest
988 unsigned CopyIdx = getInstructionIndex(CopyMI);
989 unsigned MinDist = i2miMap_.size() * InstrSlots::NUM;
990 int UseBBNum = dvi.UsedBlocks.find_first();
991 while (UseBBNum != -1) {
992 MachineBasicBlock *UseBB = mf_->getBlockNumbered(UseBBNum);
993 unsigned UseIdx = getMBBStartIdx(UseBB);
994 if (UseIdx > CopyIdx) {
995 MinDist = std::min(MinDist, UseIdx - CopyIdx);
996 if (MinDist <= Threshold)
999 UseBBNum = dvi.UsedBlocks.find_next(UseBBNum);
1001 if (MinDist > Threshold) {
1009 // Okay, attempt to join these two intervals. On failure, this returns false.
1010 // Otherwise, if one of the intervals being joined is a physreg, this method
1011 // always canonicalizes DestInt to be it. The output "SrcInt" will not have
1012 // been modified, so we can use this information below to update aliases.
1013 if (JoinIntervals(DestInt, SrcInt)) {
1015 // Result of the copy is dead. Propagate this property.
1016 if (SrcStart == 0) {
1017 assert(MRegisterInfo::isPhysicalRegister(repSrcReg) &&
1018 "Live-in must be a physical register!");
1019 // Live-in to the function but dead. Remove it from entry live-in set.
1020 // JoinIntervals may end up swapping the two intervals.
1021 mf_->begin()->removeLiveIn(repSrcReg);
1023 MachineInstr *SrcMI = getInstructionFromIndex(SrcStart);
1025 MachineOperand *mops = SrcMI->findRegisterDefOperand(SrcReg);
1027 // FIXME: mops == NULL means SrcMI defines a subregister?
1033 if (isShorten || isDead) {
1034 // Shorten the live interval.
1035 LiveInterval &LiveInInt = (repSrcReg == DestInt.reg) ? DestInt : SrcInt;
1036 LiveInInt.removeRange(RemoveStart, RemoveEnd);
1039 // Coallescing failed.
1041 // If we can eliminate the copy without merging the live ranges, do so now.
1042 if (AdjustCopiesBackFrom(SrcInt, DestInt, CopyMI))
1045 // Otherwise, we are unable to join the intervals.
1046 DOUT << "Interference!\n";
1050 bool Swapped = repSrcReg == DestInt.reg;
1052 std::swap(repSrcReg, repDstReg);
1053 assert(MRegisterInfo::isVirtualRegister(repSrcReg) &&
1054 "LiveInterval::join didn't work right!");
1056 // If we're about to merge live ranges into a physical register live range,
1057 // we have to update any aliased register's live ranges to indicate that they
1058 // have clobbered values for this range.
1059 if (MRegisterInfo::isPhysicalRegister(repDstReg)) {
1060 for (const unsigned *AS = mri_->getAliasSet(repDstReg); *AS; ++AS)
1061 getInterval(*AS).MergeInClobberRanges(SrcInt);
1063 // Merge UsedBlocks info if the destination is a virtual register.
1064 LiveVariables::VarInfo& dVI = lv_->getVarInfo(repDstReg);
1065 LiveVariables::VarInfo& sVI = lv_->getVarInfo(repSrcReg);
1066 dVI.UsedBlocks |= sVI.UsedBlocks;
1069 DOUT << "\n\t\tJoined. Result = "; DestInt.print(DOUT, mri_);
1072 // Remember these liveintervals have been joined.
1073 JoinedLIs.set(repSrcReg - MRegisterInfo::FirstVirtualRegister);
1074 if (MRegisterInfo::isVirtualRegister(repDstReg))
1075 JoinedLIs.set(repDstReg - MRegisterInfo::FirstVirtualRegister);
1077 // If the intervals were swapped by Join, swap them back so that the register
1078 // mapping (in the r2i map) is correct.
1079 if (Swapped) SrcInt.swap(DestInt);
1080 removeInterval(repSrcReg);
1081 r2rMap_[repSrcReg] = repDstReg;
1083 // Finally, delete the copy instruction.
1084 RemoveMachineInstrFromMaps(CopyMI);
1085 CopyMI->eraseFromParent();
1091 /// ComputeUltimateVN - Assuming we are going to join two live intervals,
1092 /// compute what the resultant value numbers for each value in the input two
1093 /// ranges will be. This is complicated by copies between the two which can
1094 /// and will commonly cause multiple value numbers to be merged into one.
1096 /// VN is the value number that we're trying to resolve. InstDefiningValue
1097 /// keeps track of the new InstDefiningValue assignment for the result
1098 /// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
1099 /// whether a value in this or other is a copy from the opposite set.
1100 /// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
1101 /// already been assigned.
1103 /// ThisFromOther[x] - If x is defined as a copy from the other interval, this
1104 /// contains the value number the copy is from.
1106 static unsigned ComputeUltimateVN(unsigned VN,
1107 SmallVector<std::pair<unsigned,
1108 unsigned>, 16> &ValueNumberInfo,
1109 SmallVector<int, 16> &ThisFromOther,
1110 SmallVector<int, 16> &OtherFromThis,
1111 SmallVector<int, 16> &ThisValNoAssignments,
1112 SmallVector<int, 16> &OtherValNoAssignments,
1113 LiveInterval &ThisLI, LiveInterval &OtherLI) {
1114 // If the VN has already been computed, just return it.
1115 if (ThisValNoAssignments[VN] >= 0)
1116 return ThisValNoAssignments[VN];
1117 // assert(ThisValNoAssignments[VN] != -2 && "Cyclic case?");
1119 // If this val is not a copy from the other val, then it must be a new value
1120 // number in the destination.
1121 int OtherValNo = ThisFromOther[VN];
1122 if (OtherValNo == -1) {
1123 ValueNumberInfo.push_back(ThisLI.getValNumInfo(VN));
1124 return ThisValNoAssignments[VN] = ValueNumberInfo.size()-1;
1127 // Otherwise, this *is* a copy from the RHS. If the other side has already
1128 // been computed, return it.
1129 if (OtherValNoAssignments[OtherValNo] >= 0)
1130 return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo];
1132 // Mark this value number as currently being computed, then ask what the
1133 // ultimate value # of the other value is.
1134 ThisValNoAssignments[VN] = -2;
1135 unsigned UltimateVN =
1136 ComputeUltimateVN(OtherValNo, ValueNumberInfo,
1137 OtherFromThis, ThisFromOther,
1138 OtherValNoAssignments, ThisValNoAssignments,
1140 return ThisValNoAssignments[VN] = UltimateVN;
1143 static bool InVector(unsigned Val, const SmallVector<unsigned, 8> &V) {
1144 return std::find(V.begin(), V.end(), Val) != V.end();
1147 /// SimpleJoin - Attempt to joint the specified interval into this one. The
1148 /// caller of this method must guarantee that the RHS only contains a single
1149 /// value number and that the RHS is not defined by a copy from this
1150 /// interval. This returns false if the intervals are not joinable, or it
1151 /// joins them and returns true.
1152 bool LiveIntervals::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS) {
1153 assert(RHS.containsOneValue());
1155 // Some number (potentially more than one) value numbers in the current
1156 // interval may be defined as copies from the RHS. Scan the overlapping
1157 // portions of the LHS and RHS, keeping track of this and looking for
1158 // overlapping live ranges that are NOT defined as copies. If these exist, we
1159 // cannot coallesce.
1161 LiveInterval::iterator LHSIt = LHS.begin(), LHSEnd = LHS.end();
1162 LiveInterval::iterator RHSIt = RHS.begin(), RHSEnd = RHS.end();
1164 if (LHSIt->start < RHSIt->start) {
1165 LHSIt = std::upper_bound(LHSIt, LHSEnd, RHSIt->start);
1166 if (LHSIt != LHS.begin()) --LHSIt;
1167 } else if (RHSIt->start < LHSIt->start) {
1168 RHSIt = std::upper_bound(RHSIt, RHSEnd, LHSIt->start);
1169 if (RHSIt != RHS.begin()) --RHSIt;
1172 SmallVector<unsigned, 8> EliminatedLHSVals;
1175 // Determine if these live intervals overlap.
1176 bool Overlaps = false;
1177 if (LHSIt->start <= RHSIt->start)
1178 Overlaps = LHSIt->end > RHSIt->start;
1180 Overlaps = RHSIt->end > LHSIt->start;
1182 // If the live intervals overlap, there are two interesting cases: if the
1183 // LHS interval is defined by a copy from the RHS, it's ok and we record
1184 // that the LHS value # is the same as the RHS. If it's not, then we cannot
1185 // coallesce these live ranges and we bail out.
1187 // If we haven't already recorded that this value # is safe, check it.
1188 if (!InVector(LHSIt->ValId, EliminatedLHSVals)) {
1189 // Copy from the RHS?
1190 unsigned SrcReg = LHS.getSrcRegForValNum(LHSIt->ValId);
1191 if (rep(SrcReg) != RHS.reg)
1192 return false; // Nope, bail out.
1194 EliminatedLHSVals.push_back(LHSIt->ValId);
1197 // We know this entire LHS live range is okay, so skip it now.
1198 if (++LHSIt == LHSEnd) break;
1202 if (LHSIt->end < RHSIt->end) {
1203 if (++LHSIt == LHSEnd) break;
1205 // One interesting case to check here. It's possible that we have
1206 // something like "X3 = Y" which defines a new value number in the LHS,
1207 // and is the last use of this liverange of the RHS. In this case, we
1208 // want to notice this copy (so that it gets coallesced away) even though
1209 // the live ranges don't actually overlap.
1210 if (LHSIt->start == RHSIt->end) {
1211 if (InVector(LHSIt->ValId, EliminatedLHSVals)) {
1212 // We already know that this value number is going to be merged in
1213 // if coallescing succeeds. Just skip the liverange.
1214 if (++LHSIt == LHSEnd) break;
1216 // Otherwise, if this is a copy from the RHS, mark it as being merged
1218 if (rep(LHS.getSrcRegForValNum(LHSIt->ValId)) == RHS.reg) {
1219 EliminatedLHSVals.push_back(LHSIt->ValId);
1221 // We know this entire LHS live range is okay, so skip it now.
1222 if (++LHSIt == LHSEnd) break;
1227 if (++RHSIt == RHSEnd) break;
1231 // If we got here, we know that the coallescing will be successful and that
1232 // the value numbers in EliminatedLHSVals will all be merged together. Since
1233 // the most common case is that EliminatedLHSVals has a single number, we
1234 // optimize for it: if there is more than one value, we merge them all into
1235 // the lowest numbered one, then handle the interval as if we were merging
1236 // with one value number.
1238 if (EliminatedLHSVals.size() > 1) {
1239 // Loop through all the equal value numbers merging them into the smallest
1241 unsigned Smallest = EliminatedLHSVals[0];
1242 for (unsigned i = 1, e = EliminatedLHSVals.size(); i != e; ++i) {
1243 if (EliminatedLHSVals[i] < Smallest) {
1244 // Merge the current notion of the smallest into the smaller one.
1245 LHS.MergeValueNumberInto(Smallest, EliminatedLHSVals[i]);
1246 Smallest = EliminatedLHSVals[i];
1248 // Merge into the smallest.
1249 LHS.MergeValueNumberInto(EliminatedLHSVals[i], Smallest);
1252 LHSValNo = Smallest;
1254 assert(!EliminatedLHSVals.empty() && "No copies from the RHS?");
1255 LHSValNo = EliminatedLHSVals[0];
1258 // Okay, now that there is a single LHS value number that we're merging the
1259 // RHS into, update the value number info for the LHS to indicate that the
1260 // value number is defined where the RHS value number was.
1261 LHS.setValueNumberInfo(LHSValNo, RHS.getValNumInfo(0));
1263 // Okay, the final step is to loop over the RHS live intervals, adding them to
1265 LHS.MergeRangesInAsValue(RHS, LHSValNo);
1266 LHS.weight += RHS.weight;
1271 /// JoinIntervals - Attempt to join these two intervals. On failure, this
1272 /// returns false. Otherwise, if one of the intervals being joined is a
1273 /// physreg, this method always canonicalizes LHS to be it. The output
1274 /// "RHS" will not have been modified, so we can use this information
1275 /// below to update aliases.
1276 bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
1277 // Compute the final value assignment, assuming that the live ranges can be
1279 SmallVector<int, 16> LHSValNoAssignments;
1280 SmallVector<int, 16> RHSValNoAssignments;
1281 SmallVector<std::pair<unsigned,unsigned>, 16> ValueNumberInfo;
1283 // Compute ultimate value numbers for the LHS and RHS values.
1284 if (RHS.containsOneValue()) {
1285 // Copies from a liveinterval with a single value are simple to handle and
1286 // very common, handle the special case here. This is important, because
1287 // often RHS is small and LHS is large (e.g. a physreg).
1289 // Find out if the RHS is defined as a copy from some value in the LHS.
1291 std::pair<unsigned,unsigned> RHSValNoInfo;
1292 unsigned RHSSrcReg = RHS.getSrcRegForValNum(0);
1293 if ((RHSSrcReg == 0 || rep(RHSSrcReg) != LHS.reg)) {
1294 // If RHS is not defined as a copy from the LHS, we can use simpler and
1295 // faster checks to see if the live ranges are coallescable. This joiner
1296 // can't swap the LHS/RHS intervals though.
1297 if (!MRegisterInfo::isPhysicalRegister(RHS.reg)) {
1298 return SimpleJoin(LHS, RHS);
1300 RHSValNoInfo = RHS.getValNumInfo(0);
1303 // It was defined as a copy from the LHS, find out what value # it is.
1304 unsigned ValInst = RHS.getInstForValNum(0);
1305 RHSValID = LHS.getLiveRangeContaining(ValInst-1)->ValId;
1306 RHSValNoInfo = LHS.getValNumInfo(RHSValID);
1309 LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
1310 RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
1311 ValueNumberInfo.resize(LHS.getNumValNums());
1313 // Okay, *all* of the values in LHS that are defined as a copy from RHS
1314 // should now get updated.
1315 for (unsigned VN = 0, e = LHS.getNumValNums(); VN != e; ++VN) {
1316 if (unsigned LHSSrcReg = LHS.getSrcRegForValNum(VN)) {
1317 if (rep(LHSSrcReg) != RHS.reg) {
1318 // If this is not a copy from the RHS, its value number will be
1319 // unmodified by the coallescing.
1320 ValueNumberInfo[VN] = LHS.getValNumInfo(VN);
1321 LHSValNoAssignments[VN] = VN;
1322 } else if (RHSValID == -1) {
1323 // Otherwise, it is a copy from the RHS, and we don't already have a
1324 // value# for it. Keep the current value number, but remember it.
1325 LHSValNoAssignments[VN] = RHSValID = VN;
1326 ValueNumberInfo[VN] = RHSValNoInfo;
1328 // Otherwise, use the specified value #.
1329 LHSValNoAssignments[VN] = RHSValID;
1330 if (VN != (unsigned)RHSValID)
1331 ValueNumberInfo[VN].first = ~1U;
1333 ValueNumberInfo[VN] = RHSValNoInfo;
1336 ValueNumberInfo[VN] = LHS.getValNumInfo(VN);
1337 LHSValNoAssignments[VN] = VN;
1341 assert(RHSValID != -1 && "Didn't find value #?");
1342 RHSValNoAssignments[0] = RHSValID;
1345 // Loop over the value numbers of the LHS, seeing if any are defined from
1347 SmallVector<int, 16> LHSValsDefinedFromRHS;
1348 LHSValsDefinedFromRHS.resize(LHS.getNumValNums(), -1);
1349 for (unsigned VN = 0, e = LHS.getNumValNums(); VN != e; ++VN) {
1350 unsigned ValSrcReg = LHS.getSrcRegForValNum(VN);
1351 if (ValSrcReg == 0) // Src not defined by a copy?
1354 // DstReg is known to be a register in the LHS interval. If the src is
1355 // from the RHS interval, we can use its value #.
1356 if (rep(ValSrcReg) != RHS.reg)
1359 // Figure out the value # from the RHS.
1360 unsigned ValInst = LHS.getInstForValNum(VN);
1361 LHSValsDefinedFromRHS[VN] = RHS.getLiveRangeContaining(ValInst-1)->ValId;
1364 // Loop over the value numbers of the RHS, seeing if any are defined from
1366 SmallVector<int, 16> RHSValsDefinedFromLHS;
1367 RHSValsDefinedFromLHS.resize(RHS.getNumValNums(), -1);
1368 for (unsigned VN = 0, e = RHS.getNumValNums(); VN != e; ++VN) {
1369 unsigned ValSrcReg = RHS.getSrcRegForValNum(VN);
1370 if (ValSrcReg == 0) // Src not defined by a copy?
1373 // DstReg is known to be a register in the RHS interval. If the src is
1374 // from the LHS interval, we can use its value #.
1375 if (rep(ValSrcReg) != LHS.reg)
1378 // Figure out the value # from the LHS.
1379 unsigned ValInst = RHS.getInstForValNum(VN);
1380 RHSValsDefinedFromLHS[VN] = LHS.getLiveRangeContaining(ValInst-1)->ValId;
1383 LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
1384 RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
1385 ValueNumberInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
1387 for (unsigned VN = 0, e = LHS.getNumValNums(); VN != e; ++VN) {
1388 if (LHSValNoAssignments[VN] >= 0 || LHS.getInstForValNum(VN) == ~2U)
1390 ComputeUltimateVN(VN, ValueNumberInfo,
1391 LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
1392 LHSValNoAssignments, RHSValNoAssignments, LHS, RHS);
1394 for (unsigned VN = 0, e = RHS.getNumValNums(); VN != e; ++VN) {
1395 if (RHSValNoAssignments[VN] >= 0 || RHS.getInstForValNum(VN) == ~2U)
1397 // If this value number isn't a copy from the LHS, it's a new number.
1398 if (RHSValsDefinedFromLHS[VN] == -1) {
1399 ValueNumberInfo.push_back(RHS.getValNumInfo(VN));
1400 RHSValNoAssignments[VN] = ValueNumberInfo.size()-1;
1404 ComputeUltimateVN(VN, ValueNumberInfo,
1405 RHSValsDefinedFromLHS, LHSValsDefinedFromRHS,
1406 RHSValNoAssignments, LHSValNoAssignments, RHS, LHS);
1410 // Armed with the mappings of LHS/RHS values to ultimate values, walk the
1411 // interval lists to see if these intervals are coallescable.
1412 LiveInterval::const_iterator I = LHS.begin();
1413 LiveInterval::const_iterator IE = LHS.end();
1414 LiveInterval::const_iterator J = RHS.begin();
1415 LiveInterval::const_iterator JE = RHS.end();
1417 // Skip ahead until the first place of potential sharing.
1418 if (I->start < J->start) {
1419 I = std::upper_bound(I, IE, J->start);
1420 if (I != LHS.begin()) --I;
1421 } else if (J->start < I->start) {
1422 J = std::upper_bound(J, JE, I->start);
1423 if (J != RHS.begin()) --J;
1427 // Determine if these two live ranges overlap.
1429 if (I->start < J->start) {
1430 Overlaps = I->end > J->start;
1432 Overlaps = J->end > I->start;
1435 // If so, check value # info to determine if they are really different.
1437 // If the live range overlap will map to the same value number in the
1438 // result liverange, we can still coallesce them. If not, we can't.
1439 if (LHSValNoAssignments[I->ValId] != RHSValNoAssignments[J->ValId])
1443 if (I->end < J->end) {
1452 // If we get here, we know that we can coallesce the live ranges. Ask the
1453 // intervals to coallesce themselves now.
1454 LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0],
1461 // DepthMBBCompare - Comparison predicate that sort first based on the loop
1462 // depth of the basic block (the unsigned), and then on the MBB number.
1463 struct DepthMBBCompare {
1464 typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair;
1465 bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const {
1466 if (LHS.first > RHS.first) return true; // Deeper loops first
1467 return LHS.first == RHS.first &&
1468 LHS.second->getNumber() < RHS.second->getNumber();
1474 void LiveIntervals::CopyCoallesceInMBB(MachineBasicBlock *MBB,
1475 std::vector<CopyRec> &TryAgain) {
1476 DOUT << ((Value*)MBB->getBasicBlock())->getName() << ":\n";
1478 for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
1480 MachineInstr *Inst = MII++;
1482 // If this isn't a copy, we can't join intervals.
1483 unsigned SrcReg, DstReg;
1484 if (!tii_->isMoveInstr(*Inst, SrcReg, DstReg)) continue;
1486 if (!JoinCopy(Inst, SrcReg, DstReg))
1487 TryAgain.push_back(getCopyRec(Inst, SrcReg, DstReg));
1492 void LiveIntervals::joinIntervals() {
1493 DOUT << "********** JOINING INTERVALS ***********\n";
1495 JoinedLIs.resize(getNumIntervals());
1498 std::vector<CopyRec> TryAgainList;
1499 const LoopInfo &LI = getAnalysis<LoopInfo>();
1500 if (LI.begin() == LI.end()) {
1501 // If there are no loops in the function, join intervals in function order.
1502 for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
1504 CopyCoallesceInMBB(I, TryAgainList);
1506 // Otherwise, join intervals in inner loops before other intervals.
1507 // Unfortunately we can't just iterate over loop hierarchy here because
1508 // there may be more MBB's than BB's. Collect MBB's for sorting.
1509 std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs;
1510 for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
1512 MBBs.push_back(std::make_pair(LI.getLoopDepth(I->getBasicBlock()), I));
1514 // Sort by loop depth.
1515 std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare());
1517 // Finally, join intervals in loop nest order.
1518 for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
1519 CopyCoallesceInMBB(MBBs[i].second, TryAgainList);
1522 // Joining intervals can allow other intervals to be joined. Iteratively join
1523 // until we make no progress.
1524 bool ProgressMade = true;
1525 while (ProgressMade) {
1526 ProgressMade = false;
1528 for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) {
1529 CopyRec &TheCopy = TryAgainList[i];
1531 JoinCopy(TheCopy.MI, TheCopy.SrcReg, TheCopy.DstReg)) {
1532 TheCopy.MI = 0; // Mark this one as done.
1533 ProgressMade = true;
1538 // Some live range has been lengthened due to colaescing, eliminate the
1539 // unnecessary kills.
1540 int RegNum = JoinedLIs.find_first();
1541 while (RegNum != -1) {
1542 unsigned Reg = RegNum + MRegisterInfo::FirstVirtualRegister;
1543 unsigned repReg = rep(Reg);
1544 LiveInterval &LI = getInterval(repReg);
1545 LiveVariables::VarInfo& svi = lv_->getVarInfo(Reg);
1546 for (unsigned i = 0, e = svi.Kills.size(); i != e; ++i) {
1547 MachineInstr *Kill = svi.Kills[i];
1548 // Suppose vr1 = op vr2, x
1549 // and vr1 and vr2 are coalesced. vr2 should still be marked kill
1550 // unless it is a two-address operand.
1551 if (isRemoved(Kill) || hasRegisterDef(Kill, repReg))
1553 if (LI.liveAt(getInstructionIndex(Kill) + InstrSlots::NUM))
1554 unsetRegisterKill(Kill, repReg);
1556 RegNum = JoinedLIs.find_next(RegNum);
1559 DOUT << "*** Register mapping ***\n";
1560 for (int i = 0, e = r2rMap_.size(); i != e; ++i)
1562 DOUT << " reg " << i << " -> ";
1563 DEBUG(printRegName(r2rMap_[i]));
1568 /// Return true if the two specified registers belong to different register
1569 /// classes. The registers may be either phys or virt regs.
1570 bool LiveIntervals::differingRegisterClasses(unsigned RegA,
1571 unsigned RegB) const {
1573 // Get the register classes for the first reg.
1574 if (MRegisterInfo::isPhysicalRegister(RegA)) {
1575 assert(MRegisterInfo::isVirtualRegister(RegB) &&
1576 "Shouldn't consider two physregs!");
1577 return !mf_->getSSARegMap()->getRegClass(RegB)->contains(RegA);
1580 // Compare against the regclass for the second reg.
1581 const TargetRegisterClass *RegClass = mf_->getSSARegMap()->getRegClass(RegA);
1582 if (MRegisterInfo::isVirtualRegister(RegB))
1583 return RegClass != mf_->getSSARegMap()->getRegClass(RegB);
1585 return !RegClass->contains(RegB);
1588 /// lastRegisterUse - Returns the last use of the specific register between
1589 /// cycles Start and End. It also returns the use operand by reference. It
1590 /// returns NULL if there are no uses.
1592 LiveIntervals::lastRegisterUse(unsigned Reg, unsigned Start, unsigned End,
1593 MachineOperand *&MOU) {
1594 int e = (End-1) / InstrSlots::NUM * InstrSlots::NUM;
1597 // Skip deleted instructions
1598 MachineInstr *MI = getInstructionFromIndex(e);
1599 while ((e - InstrSlots::NUM) >= s && !MI) {
1600 e -= InstrSlots::NUM;
1601 MI = getInstructionFromIndex(e);
1603 if (e < s || MI == NULL)
1606 for (unsigned i = 0, NumOps = MI->getNumOperands(); i != NumOps; ++i) {
1607 MachineOperand &MO = MI->getOperand(i);
1608 if (MO.isReg() && MO.isUse() && MO.getReg() &&
1609 mri_->regsOverlap(rep(MO.getReg()), Reg)) {
1615 e -= InstrSlots::NUM;
1621 /// unsetRegisterKill - Unset IsKill property of all uses of specific register
1622 /// of the specific instruction.
1623 void LiveIntervals::unsetRegisterKill(MachineInstr *MI, unsigned Reg) {
1624 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1625 MachineOperand &MO = MI->getOperand(i);
1626 if (MO.isReg() && MO.isUse() && MO.isKill() && MO.getReg() &&
1627 mri_->regsOverlap(rep(MO.getReg()), Reg))
1632 /// hasRegisterDef - True if the instruction defines the specific register.
1634 bool LiveIntervals::hasRegisterDef(MachineInstr *MI, unsigned Reg) {
1635 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1636 MachineOperand &MO = MI->getOperand(i);
1637 if (MO.isReg() && MO.isDef() &&
1638 mri_->regsOverlap(rep(MO.getReg()), Reg))
1644 LiveInterval LiveIntervals::createInterval(unsigned reg) {
1645 float Weight = MRegisterInfo::isPhysicalRegister(reg) ?
1647 return LiveInterval(reg, Weight);