| //===-- LiveIntervalAnalysis.cpp - Live Interval Analysis -----------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the LiveInterval analysis pass which is used |
| // by the Linear Scan Register allocator. This pass linearizes the |
| // basic blocks of the function in DFS order and uses the |
| // LiveVariables pass to conservatively compute live intervals for |
| // each virtual and physical register. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "liveintervals" |
| #include "llvm/CodeGen/LiveIntervalAnalysis.h" |
| #include "VirtRegMap.h" |
| #include "llvm/Value.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/CodeGen/CalcSpillWeights.h" |
| #include "llvm/CodeGen/LiveVariables.h" |
| #include "llvm/CodeGen/MachineFrameInfo.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/MachineLoopInfo.h" |
| #include "llvm/CodeGen/MachineMemOperand.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/CodeGen/ProcessImplicitDefs.h" |
| #include "llvm/Target/TargetRegisterInfo.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Target/TargetOptions.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include <algorithm> |
| #include <limits> |
| #include <cmath> |
| using namespace llvm; |
| |
| // Hidden options for help debugging. |
| static cl::opt<bool> DisableReMat("disable-rematerialization", |
| cl::init(false), cl::Hidden); |
| |
| STATISTIC(numIntervals , "Number of original intervals"); |
| |
| char LiveIntervals::ID = 0; |
| INITIALIZE_PASS_BEGIN(LiveIntervals, "liveintervals", |
| "Live Interval Analysis", false, false) |
| INITIALIZE_PASS_DEPENDENCY(LiveVariables) |
| INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) |
| INITIALIZE_PASS_DEPENDENCY(PHIElimination) |
| INITIALIZE_PASS_DEPENDENCY(TwoAddressInstructionPass) |
| INITIALIZE_PASS_DEPENDENCY(ProcessImplicitDefs) |
| INITIALIZE_PASS_DEPENDENCY(SlotIndexes) |
| INITIALIZE_AG_DEPENDENCY(AliasAnalysis) |
| INITIALIZE_PASS_END(LiveIntervals, "liveintervals", |
| "Live Interval Analysis", false, false) |
| |
| void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesCFG(); |
| AU.addRequired<AliasAnalysis>(); |
| AU.addPreserved<AliasAnalysis>(); |
| AU.addRequired<LiveVariables>(); |
| AU.addPreserved<LiveVariables>(); |
| AU.addRequired<MachineLoopInfo>(); |
| AU.addPreserved<MachineLoopInfo>(); |
| AU.addPreservedID(MachineDominatorsID); |
| |
| if (!StrongPHIElim) { |
| AU.addPreservedID(PHIEliminationID); |
| AU.addRequiredID(PHIEliminationID); |
| } |
| |
| AU.addRequiredID(TwoAddressInstructionPassID); |
| AU.addPreserved<ProcessImplicitDefs>(); |
| AU.addRequired<ProcessImplicitDefs>(); |
| AU.addPreserved<SlotIndexes>(); |
| AU.addRequiredTransitive<SlotIndexes>(); |
| MachineFunctionPass::getAnalysisUsage(AU); |
| } |
| |
| void LiveIntervals::releaseMemory() { |
| // Free the live intervals themselves. |
| for (DenseMap<unsigned, LiveInterval*>::iterator I = r2iMap_.begin(), |
| E = r2iMap_.end(); I != E; ++I) |
| delete I->second; |
| |
| r2iMap_.clear(); |
| |
| // Release VNInfo memory regions, VNInfo objects don't need to be dtor'd. |
| VNInfoAllocator.Reset(); |
| while (!CloneMIs.empty()) { |
| MachineInstr *MI = CloneMIs.back(); |
| CloneMIs.pop_back(); |
| mf_->DeleteMachineInstr(MI); |
| } |
| } |
| |
| /// runOnMachineFunction - Register allocate the whole function |
| /// |
| bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) { |
| mf_ = &fn; |
| mri_ = &mf_->getRegInfo(); |
| tm_ = &fn.getTarget(); |
| tri_ = tm_->getRegisterInfo(); |
| tii_ = tm_->getInstrInfo(); |
| aa_ = &getAnalysis<AliasAnalysis>(); |
| lv_ = &getAnalysis<LiveVariables>(); |
| indexes_ = &getAnalysis<SlotIndexes>(); |
| allocatableRegs_ = tri_->getAllocatableSet(fn); |
| |
| computeIntervals(); |
| |
| numIntervals += getNumIntervals(); |
| |
| DEBUG(dump()); |
| return true; |
| } |
| |
| /// print - Implement the dump method. |
| void LiveIntervals::print(raw_ostream &OS, const Module* ) const { |
| OS << "********** INTERVALS **********\n"; |
| for (const_iterator I = begin(), E = end(); I != E; ++I) { |
| I->second->print(OS, tri_); |
| OS << "\n"; |
| } |
| |
| printInstrs(OS); |
| } |
| |
| void LiveIntervals::printInstrs(raw_ostream &OS) const { |
| OS << "********** MACHINEINSTRS **********\n"; |
| mf_->print(OS, indexes_); |
| } |
| |
| void LiveIntervals::dumpInstrs() const { |
| printInstrs(dbgs()); |
| } |
| |
| static |
| bool MultipleDefsBySameMI(const MachineInstr &MI, unsigned MOIdx) { |
| unsigned Reg = MI.getOperand(MOIdx).getReg(); |
| for (unsigned i = MOIdx+1, e = MI.getNumOperands(); i < e; ++i) { |
| const MachineOperand &MO = MI.getOperand(i); |
| if (!MO.isReg()) |
| continue; |
| if (MO.getReg() == Reg && MO.isDef()) { |
| assert(MI.getOperand(MOIdx).getSubReg() != MO.getSubReg() && |
| MI.getOperand(MOIdx).getSubReg() && |
| (MO.getSubReg() || MO.isImplicit())); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /// isPartialRedef - Return true if the specified def at the specific index is |
| /// partially re-defining the specified live interval. A common case of this is |
| /// a definition of the sub-register. |
| bool LiveIntervals::isPartialRedef(SlotIndex MIIdx, MachineOperand &MO, |
| LiveInterval &interval) { |
| if (!MO.getSubReg() || MO.isEarlyClobber()) |
| return false; |
| |
| SlotIndex RedefIndex = MIIdx.getRegSlot(); |
| const LiveRange *OldLR = |
| interval.getLiveRangeContaining(RedefIndex.getRegSlot(true)); |
| MachineInstr *DefMI = getInstructionFromIndex(OldLR->valno->def); |
| if (DefMI != 0) { |
| return DefMI->findRegisterDefOperandIdx(interval.reg) != -1; |
| } |
| return false; |
| } |
| |
| void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb, |
| MachineBasicBlock::iterator mi, |
| SlotIndex MIIdx, |
| MachineOperand& MO, |
| unsigned MOIdx, |
| LiveInterval &interval) { |
| DEBUG(dbgs() << "\t\tregister: " << PrintReg(interval.reg, tri_)); |
| |
| // Virtual registers may be defined multiple times (due to phi |
| // elimination and 2-addr elimination). Much of what we do only has to be |
| // done once for the vreg. We use an empty interval to detect the first |
| // time we see a vreg. |
| LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg); |
| if (interval.empty()) { |
| // Get the Idx of the defining instructions. |
| SlotIndex defIndex = MIIdx.getRegSlot(MO.isEarlyClobber()); |
| |
| // Make sure the first definition is not a partial redefinition. Add an |
| // <imp-def> of the full register. |
| // FIXME: LiveIntervals shouldn't modify the code like this. Whoever |
| // created the machine instruction should annotate it with <undef> flags |
| // as needed. Then we can simply assert here. The REG_SEQUENCE lowering |
| // is the main suspect. |
| if (MO.getSubReg()) { |
| mi->addRegisterDefined(interval.reg); |
| // Mark all defs of interval.reg on this instruction as reading <undef>. |
| for (unsigned i = MOIdx, e = mi->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO2 = mi->getOperand(i); |
| if (MO2.isReg() && MO2.getReg() == interval.reg && MO2.getSubReg()) |
| MO2.setIsUndef(); |
| } |
| } |
| |
| MachineInstr *CopyMI = NULL; |
| if (mi->isCopyLike()) { |
| CopyMI = mi; |
| } |
| |
| VNInfo *ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator); |
| assert(ValNo->id == 0 && "First value in interval is not 0?"); |
| |
| // Loop over all of the blocks that the vreg is defined in. There are |
| // two cases we have to handle here. The most common case is a vreg |
| // whose lifetime is contained within a basic block. In this case there |
| // will be a single kill, in MBB, which comes after the definition. |
| if (vi.Kills.size() == 1 && vi.Kills[0]->getParent() == mbb) { |
| // FIXME: what about dead vars? |
| SlotIndex killIdx; |
| if (vi.Kills[0] != mi) |
| killIdx = getInstructionIndex(vi.Kills[0]).getRegSlot(); |
| else |
| killIdx = defIndex.getDeadSlot(); |
| |
| // If the kill happens after the definition, we have an intra-block |
| // live range. |
| if (killIdx > defIndex) { |
| assert(vi.AliveBlocks.empty() && |
| "Shouldn't be alive across any blocks!"); |
| LiveRange LR(defIndex, killIdx, ValNo); |
| interval.addRange(LR); |
| DEBUG(dbgs() << " +" << LR << "\n"); |
| return; |
| } |
| } |
| |
| // The other case we handle is when a virtual register lives to the end |
| // of the defining block, potentially live across some blocks, then is |
| // live into some number of blocks, but gets killed. Start by adding a |
| // range that goes from this definition to the end of the defining block. |
| LiveRange NewLR(defIndex, getMBBEndIdx(mbb), ValNo); |
| DEBUG(dbgs() << " +" << NewLR); |
| interval.addRange(NewLR); |
| |
| bool PHIJoin = lv_->isPHIJoin(interval.reg); |
| |
| if (PHIJoin) { |
| // A phi join register is killed at the end of the MBB and revived as a new |
| // valno in the killing blocks. |
| assert(vi.AliveBlocks.empty() && "Phi join can't pass through blocks"); |
| DEBUG(dbgs() << " phi-join"); |
| ValNo->setHasPHIKill(true); |
| } else { |
| // Iterate over all of the blocks that the variable is completely |
| // live in, adding [insrtIndex(begin), instrIndex(end)+4) to the |
| // live interval. |
| for (SparseBitVector<>::iterator I = vi.AliveBlocks.begin(), |
| E = vi.AliveBlocks.end(); I != E; ++I) { |
| MachineBasicBlock *aliveBlock = mf_->getBlockNumbered(*I); |
| LiveRange LR(getMBBStartIdx(aliveBlock), getMBBEndIdx(aliveBlock), ValNo); |
| interval.addRange(LR); |
| DEBUG(dbgs() << " +" << LR); |
| } |
| } |
| |
| // Finally, this virtual register is live from the start of any killing |
| // block to the 'use' slot of the killing instruction. |
| for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) { |
| MachineInstr *Kill = vi.Kills[i]; |
| SlotIndex Start = getMBBStartIdx(Kill->getParent()); |
| SlotIndex killIdx = getInstructionIndex(Kill).getRegSlot(); |
| |
| // Create interval with one of a NEW value number. Note that this value |
| // number isn't actually defined by an instruction, weird huh? :) |
| if (PHIJoin) { |
| assert(getInstructionFromIndex(Start) == 0 && |
| "PHI def index points at actual instruction."); |
| ValNo = interval.getNextValue(Start, 0, VNInfoAllocator); |
| ValNo->setIsPHIDef(true); |
| } |
| LiveRange LR(Start, killIdx, ValNo); |
| interval.addRange(LR); |
| DEBUG(dbgs() << " +" << LR); |
| } |
| |
| } else { |
| if (MultipleDefsBySameMI(*mi, MOIdx)) |
| // Multiple defs of the same virtual register by the same instruction. |
| // e.g. %reg1031:5<def>, %reg1031:6<def> = VLD1q16 %reg1024<kill>, ... |
| // This is likely due to elimination of REG_SEQUENCE instructions. Return |
| // here since there is nothing to do. |
| return; |
| |
| // If this is the second time we see a virtual register definition, it |
| // must be due to phi elimination or two addr elimination. If this is |
| // the result of two address elimination, then the vreg is one of the |
| // def-and-use register operand. |
| |
| // It may also be partial redef like this: |
| // 80 %reg1041:6<def> = VSHRNv4i16 %reg1034<kill>, 12, pred:14, pred:%reg0 |
| // 120 %reg1041:5<def> = VSHRNv4i16 %reg1039<kill>, 12, pred:14, pred:%reg0 |
| bool PartReDef = isPartialRedef(MIIdx, MO, interval); |
| if (PartReDef || mi->isRegTiedToUseOperand(MOIdx)) { |
| // If this is a two-address definition, then we have already processed |
| // the live range. The only problem is that we didn't realize there |
| // are actually two values in the live interval. Because of this we |
| // need to take the LiveRegion that defines this register and split it |
| // into two values. |
| SlotIndex RedefIndex = MIIdx.getRegSlot(MO.isEarlyClobber()); |
| |
| const LiveRange *OldLR = |
| interval.getLiveRangeContaining(RedefIndex.getRegSlot(true)); |
| VNInfo *OldValNo = OldLR->valno; |
| SlotIndex DefIndex = OldValNo->def.getRegSlot(); |
| |
| // Delete the previous value, which should be short and continuous, |
| // because the 2-addr copy must be in the same MBB as the redef. |
| interval.removeRange(DefIndex, RedefIndex); |
| |
| // The new value number (#1) is defined by the instruction we claimed |
| // defined value #0. |
| VNInfo *ValNo = interval.createValueCopy(OldValNo, VNInfoAllocator); |
| |
| // Value#0 is now defined by the 2-addr instruction. |
| OldValNo->def = RedefIndex; |
| OldValNo->setCopy(0); |
| |
| // A re-def may be a copy. e.g. %reg1030:6<def> = VMOVD %reg1026, ... |
| if (PartReDef && mi->isCopyLike()) |
| OldValNo->setCopy(&*mi); |
| |
| // Add the new live interval which replaces the range for the input copy. |
| LiveRange LR(DefIndex, RedefIndex, ValNo); |
| DEBUG(dbgs() << " replace range with " << LR); |
| interval.addRange(LR); |
| |
| // If this redefinition is dead, we need to add a dummy unit live |
| // range covering the def slot. |
| if (MO.isDead()) |
| interval.addRange(LiveRange(RedefIndex, RedefIndex.getDeadSlot(), |
| OldValNo)); |
| |
| DEBUG({ |
| dbgs() << " RESULT: "; |
| interval.print(dbgs(), tri_); |
| }); |
| } else if (lv_->isPHIJoin(interval.reg)) { |
| // In the case of PHI elimination, each variable definition is only |
| // live until the end of the block. We've already taken care of the |
| // rest of the live range. |
| |
| SlotIndex defIndex = MIIdx.getRegSlot(); |
| if (MO.isEarlyClobber()) |
| defIndex = MIIdx.getRegSlot(true); |
| |
| VNInfo *ValNo; |
| MachineInstr *CopyMI = NULL; |
| if (mi->isCopyLike()) |
| CopyMI = mi; |
| ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator); |
| |
| SlotIndex killIndex = getMBBEndIdx(mbb); |
| LiveRange LR(defIndex, killIndex, ValNo); |
| interval.addRange(LR); |
| ValNo->setHasPHIKill(true); |
| DEBUG(dbgs() << " phi-join +" << LR); |
| } else { |
| llvm_unreachable("Multiply defined register"); |
| } |
| } |
| |
| DEBUG(dbgs() << '\n'); |
| } |
| |
| void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB, |
| MachineBasicBlock::iterator mi, |
| SlotIndex MIIdx, |
| MachineOperand& MO, |
| LiveInterval &interval, |
| MachineInstr *CopyMI) { |
| // A physical register cannot be live across basic block, so its |
| // lifetime must end somewhere in its defining basic block. |
| DEBUG(dbgs() << "\t\tregister: " << PrintReg(interval.reg, tri_)); |
| |
| SlotIndex baseIndex = MIIdx; |
| SlotIndex start = baseIndex.getRegSlot(MO.isEarlyClobber()); |
| SlotIndex end = start; |
| |
| // If it is not used after definition, it is considered dead at |
| // the instruction defining it. Hence its interval is: |
| // [defSlot(def), defSlot(def)+1) |
| // For earlyclobbers, the defSlot was pushed back one; the extra |
| // advance below compensates. |
| if (MO.isDead()) { |
| DEBUG(dbgs() << " dead"); |
| end = start.getDeadSlot(); |
| goto exit; |
| } |
| |
| // If it is not dead on definition, it must be killed by a |
| // subsequent instruction. Hence its interval is: |
| // [defSlot(def), useSlot(kill)+1) |
| baseIndex = baseIndex.getNextIndex(); |
| while (++mi != MBB->end()) { |
| |
| if (mi->isDebugValue()) |
| continue; |
| if (getInstructionFromIndex(baseIndex) == 0) |
| baseIndex = indexes_->getNextNonNullIndex(baseIndex); |
| |
| if (mi->killsRegister(interval.reg, tri_)) { |
| DEBUG(dbgs() << " killed"); |
| end = baseIndex.getRegSlot(); |
| goto exit; |
| } else { |
| int DefIdx = mi->findRegisterDefOperandIdx(interval.reg,false,false,tri_); |
| if (DefIdx != -1) { |
| if (mi->isRegTiedToUseOperand(DefIdx)) { |
| // Two-address instruction. |
| end = baseIndex.getRegSlot(); |
| } else { |
| // Another instruction redefines the register before it is ever read. |
| // Then the register is essentially dead at the instruction that |
| // defines it. Hence its interval is: |
| // [defSlot(def), defSlot(def)+1) |
| DEBUG(dbgs() << " dead"); |
| end = start.getDeadSlot(); |
| } |
| goto exit; |
| } |
| } |
| |
| baseIndex = baseIndex.getNextIndex(); |
| } |
| |
| // The only case we should have a dead physreg here without a killing or |
| // instruction where we know it's dead is if it is live-in to the function |
| // and never used. Another possible case is the implicit use of the |
| // physical register has been deleted by two-address pass. |
| end = start.getDeadSlot(); |
| |
| exit: |
| assert(start < end && "did not find end of interval?"); |
| |
| // Already exists? Extend old live interval. |
| VNInfo *ValNo = interval.getVNInfoAt(start); |
| bool Extend = ValNo != 0; |
| if (!Extend) |
| ValNo = interval.getNextValue(start, CopyMI, VNInfoAllocator); |
| if (Extend && MO.isEarlyClobber()) |
| ValNo->setHasRedefByEC(true); |
| LiveRange LR(start, end, ValNo); |
| interval.addRange(LR); |
| DEBUG(dbgs() << " +" << LR << '\n'); |
| } |
| |
| void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB, |
| MachineBasicBlock::iterator MI, |
| SlotIndex MIIdx, |
| MachineOperand& MO, |
| unsigned MOIdx) { |
| if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) |
| handleVirtualRegisterDef(MBB, MI, MIIdx, MO, MOIdx, |
| getOrCreateInterval(MO.getReg())); |
| else { |
| MachineInstr *CopyMI = NULL; |
| if (MI->isCopyLike()) |
| CopyMI = MI; |
| handlePhysicalRegisterDef(MBB, MI, MIIdx, MO, |
| getOrCreateInterval(MO.getReg()), CopyMI); |
| } |
| } |
| |
| void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB, |
| SlotIndex MIIdx, |
| LiveInterval &interval, bool isAlias) { |
| DEBUG(dbgs() << "\t\tlivein register: " << PrintReg(interval.reg, tri_)); |
| |
| // Look for kills, if it reaches a def before it's killed, then it shouldn't |
| // be considered a livein. |
| MachineBasicBlock::iterator mi = MBB->begin(); |
| MachineBasicBlock::iterator E = MBB->end(); |
| // Skip over DBG_VALUE at the start of the MBB. |
| if (mi != E && mi->isDebugValue()) { |
| while (++mi != E && mi->isDebugValue()) |
| ; |
| if (mi == E) |
| // MBB is empty except for DBG_VALUE's. |
| return; |
| } |
| |
| SlotIndex baseIndex = MIIdx; |
| SlotIndex start = baseIndex; |
| if (getInstructionFromIndex(baseIndex) == 0) |
| baseIndex = indexes_->getNextNonNullIndex(baseIndex); |
| |
| SlotIndex end = baseIndex; |
| bool SeenDefUse = false; |
| |
| while (mi != E) { |
| if (mi->killsRegister(interval.reg, tri_)) { |
| DEBUG(dbgs() << " killed"); |
| end = baseIndex.getRegSlot(); |
| SeenDefUse = true; |
| break; |
| } else if (mi->definesRegister(interval.reg, tri_)) { |
| // Another instruction redefines the register before it is ever read. |
| // Then the register is essentially dead at the instruction that defines |
| // it. Hence its interval is: |
| // [defSlot(def), defSlot(def)+1) |
| DEBUG(dbgs() << " dead"); |
| end = start.getDeadSlot(); |
| SeenDefUse = true; |
| break; |
| } |
| |
| while (++mi != E && mi->isDebugValue()) |
| // Skip over DBG_VALUE. |
| ; |
| if (mi != E) |
| baseIndex = indexes_->getNextNonNullIndex(baseIndex); |
| } |
| |
| // Live-in register might not be used at all. |
| if (!SeenDefUse) { |
| if (isAlias) { |
| DEBUG(dbgs() << " dead"); |
| end = MIIdx.getDeadSlot(); |
| } else { |
| DEBUG(dbgs() << " live through"); |
| end = getMBBEndIdx(MBB); |
| } |
| } |
| |
| SlotIndex defIdx = getMBBStartIdx(MBB); |
| assert(getInstructionFromIndex(defIdx) == 0 && |
| "PHI def index points at actual instruction."); |
| VNInfo *vni = |
| interval.getNextValue(defIdx, 0, VNInfoAllocator); |
| vni->setIsPHIDef(true); |
| LiveRange LR(start, end, vni); |
| |
| interval.addRange(LR); |
| DEBUG(dbgs() << " +" << LR << '\n'); |
| } |
| |
| /// computeIntervals - computes the live intervals for virtual |
| /// registers. for some ordering of the machine instructions [1,N] a |
| /// live interval is an interval [i, j) where 1 <= i <= j < N for |
| /// which a variable is live |
| void LiveIntervals::computeIntervals() { |
| DEBUG(dbgs() << "********** COMPUTING LIVE INTERVALS **********\n" |
| << "********** Function: " |
| << ((Value*)mf_->getFunction())->getName() << '\n'); |
| |
| SmallVector<unsigned, 8> UndefUses; |
| for (MachineFunction::iterator MBBI = mf_->begin(), E = mf_->end(); |
| MBBI != E; ++MBBI) { |
| MachineBasicBlock *MBB = MBBI; |
| if (MBB->empty()) |
| continue; |
| |
| // Track the index of the current machine instr. |
| SlotIndex MIIndex = getMBBStartIdx(MBB); |
| DEBUG(dbgs() << "BB#" << MBB->getNumber() |
| << ":\t\t# derived from " << MBB->getName() << "\n"); |
| |
| // Create intervals for live-ins to this BB first. |
| for (MachineBasicBlock::livein_iterator LI = MBB->livein_begin(), |
| LE = MBB->livein_end(); LI != LE; ++LI) { |
| handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI)); |
| // Multiple live-ins can alias the same register. |
| for (const unsigned* AS = tri_->getSubRegisters(*LI); *AS; ++AS) |
| if (!hasInterval(*AS)) |
| handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS), |
| true); |
| } |
| |
| // Skip over empty initial indices. |
| if (getInstructionFromIndex(MIIndex) == 0) |
| MIIndex = indexes_->getNextNonNullIndex(MIIndex); |
| |
| for (MachineBasicBlock::iterator MI = MBB->begin(), miEnd = MBB->end(); |
| MI != miEnd; ++MI) { |
| DEBUG(dbgs() << MIIndex << "\t" << *MI); |
| if (MI->isDebugValue()) |
| continue; |
| |
| // Handle defs. |
| for (int i = MI->getNumOperands() - 1; i >= 0; --i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg() || !MO.getReg()) |
| continue; |
| |
| // handle register defs - build intervals |
| if (MO.isDef()) |
| handleRegisterDef(MBB, MI, MIIndex, MO, i); |
| else if (MO.isUndef()) |
| UndefUses.push_back(MO.getReg()); |
| } |
| |
| // Move to the next instr slot. |
| MIIndex = indexes_->getNextNonNullIndex(MIIndex); |
| } |
| } |
| |
| // Create empty intervals for registers defined by implicit_def's (except |
| // for those implicit_def that define values which are liveout of their |
| // blocks. |
| for (unsigned i = 0, e = UndefUses.size(); i != e; ++i) { |
| unsigned UndefReg = UndefUses[i]; |
| (void)getOrCreateInterval(UndefReg); |
| } |
| } |
| |
| LiveInterval* LiveIntervals::createInterval(unsigned reg) { |
| float Weight = TargetRegisterInfo::isPhysicalRegister(reg) ? HUGE_VALF : 0.0F; |
| return new LiveInterval(reg, Weight); |
| } |
| |
| /// dupInterval - Duplicate a live interval. The caller is responsible for |
| /// managing the allocated memory. |
| LiveInterval* LiveIntervals::dupInterval(LiveInterval *li) { |
| LiveInterval *NewLI = createInterval(li->reg); |
| NewLI->Copy(*li, mri_, getVNInfoAllocator()); |
| return NewLI; |
| } |
| |
| /// shrinkToUses - After removing some uses of a register, shrink its live |
| /// range to just the remaining uses. This method does not compute reaching |
| /// defs for new uses, and it doesn't remove dead defs. |
| bool LiveIntervals::shrinkToUses(LiveInterval *li, |
| SmallVectorImpl<MachineInstr*> *dead) { |
| DEBUG(dbgs() << "Shrink: " << *li << '\n'); |
| assert(TargetRegisterInfo::isVirtualRegister(li->reg) |
| && "Can't only shrink physical registers"); |
| // Find all the values used, including PHI kills. |
| SmallVector<std::pair<SlotIndex, VNInfo*>, 16> WorkList; |
| |
| // Blocks that have already been added to WorkList as live-out. |
| SmallPtrSet<MachineBasicBlock*, 16> LiveOut; |
| |
| // Visit all instructions reading li->reg. |
| for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(li->reg); |
| MachineInstr *UseMI = I.skipInstruction();) { |
| if (UseMI->isDebugValue() || !UseMI->readsVirtualRegister(li->reg)) |
| continue; |
| SlotIndex Idx = getInstructionIndex(UseMI).getRegSlot(); |
| // Note: This intentionally picks up the wrong VNI in case of an EC redef. |
| // See below. |
| VNInfo *VNI = li->getVNInfoBefore(Idx); |
| if (!VNI) { |
| // This shouldn't happen: readsVirtualRegister returns true, but there is |
| // no live value. It is likely caused by a target getting <undef> flags |
| // wrong. |
| DEBUG(dbgs() << Idx << '\t' << *UseMI |
| << "Warning: Instr claims to read non-existent value in " |
| << *li << '\n'); |
| continue; |
| } |
| // Special case: An early-clobber tied operand reads and writes the |
| // register one slot early. The getVNInfoBefore call above would have |
| // picked up the value defined by UseMI. Adjust the kill slot and value. |
| if (SlotIndex::isSameInstr(VNI->def, Idx)) { |
| Idx = VNI->def; |
| VNI = li->getVNInfoBefore(Idx); |
| assert(VNI && "Early-clobber tied value not available"); |
| } |
| WorkList.push_back(std::make_pair(Idx, VNI)); |
| } |
| |
| // Create a new live interval with only minimal live segments per def. |
| LiveInterval NewLI(li->reg, 0); |
| for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end(); |
| I != E; ++I) { |
| VNInfo *VNI = *I; |
| if (VNI->isUnused()) |
| continue; |
| NewLI.addRange(LiveRange(VNI->def, VNI->def.getDeadSlot(), VNI)); |
| } |
| |
| // Keep track of the PHIs that are in use. |
| SmallPtrSet<VNInfo*, 8> UsedPHIs; |
| |
| // Extend intervals to reach all uses in WorkList. |
| while (!WorkList.empty()) { |
| SlotIndex Idx = WorkList.back().first; |
| VNInfo *VNI = WorkList.back().second; |
| WorkList.pop_back(); |
| const MachineBasicBlock *MBB = getMBBFromIndex(Idx.getPrevSlot()); |
| SlotIndex BlockStart = getMBBStartIdx(MBB); |
| |
| // Extend the live range for VNI to be live at Idx. |
| if (VNInfo *ExtVNI = NewLI.extendInBlock(BlockStart, Idx)) { |
| (void)ExtVNI; |
| assert(ExtVNI == VNI && "Unexpected existing value number"); |
| // Is this a PHIDef we haven't seen before? |
| if (!VNI->isPHIDef() || VNI->def != BlockStart || !UsedPHIs.insert(VNI)) |
| continue; |
| // The PHI is live, make sure the predecessors are live-out. |
| for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), |
| PE = MBB->pred_end(); PI != PE; ++PI) { |
| if (!LiveOut.insert(*PI)) |
| continue; |
| SlotIndex Stop = getMBBEndIdx(*PI); |
| // A predecessor is not required to have a live-out value for a PHI. |
| if (VNInfo *PVNI = li->getVNInfoBefore(Stop)) |
| WorkList.push_back(std::make_pair(Stop, PVNI)); |
| } |
| continue; |
| } |
| |
| // VNI is live-in to MBB. |
| DEBUG(dbgs() << " live-in at " << BlockStart << '\n'); |
| NewLI.addRange(LiveRange(BlockStart, Idx, VNI)); |
| |
| // Make sure VNI is live-out from the predecessors. |
| for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), |
| PE = MBB->pred_end(); PI != PE; ++PI) { |
| if (!LiveOut.insert(*PI)) |
| continue; |
| SlotIndex Stop = getMBBEndIdx(*PI); |
| assert(li->getVNInfoBefore(Stop) == VNI && |
| "Wrong value out of predecessor"); |
| WorkList.push_back(std::make_pair(Stop, VNI)); |
| } |
| } |
| |
| // Handle dead values. |
| bool CanSeparate = false; |
| for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end(); |
| I != E; ++I) { |
| VNInfo *VNI = *I; |
| if (VNI->isUnused()) |
| continue; |
| LiveInterval::iterator LII = NewLI.FindLiveRangeContaining(VNI->def); |
| assert(LII != NewLI.end() && "Missing live range for PHI"); |
| if (LII->end != VNI->def.getDeadSlot()) |
| continue; |
| if (VNI->isPHIDef()) { |
| // This is a dead PHI. Remove it. |
| VNI->setIsUnused(true); |
| NewLI.removeRange(*LII); |
| DEBUG(dbgs() << "Dead PHI at " << VNI->def << " may separate interval\n"); |
| CanSeparate = true; |
| } else { |
| // This is a dead def. Make sure the instruction knows. |
| MachineInstr *MI = getInstructionFromIndex(VNI->def); |
| assert(MI && "No instruction defining live value"); |
| MI->addRegisterDead(li->reg, tri_); |
| if (dead && MI->allDefsAreDead()) { |
| DEBUG(dbgs() << "All defs dead: " << VNI->def << '\t' << *MI); |
| dead->push_back(MI); |
| } |
| } |
| } |
| |
| // Move the trimmed ranges back. |
| li->ranges.swap(NewLI.ranges); |
| DEBUG(dbgs() << "Shrunk: " << *li << '\n'); |
| return CanSeparate; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Register allocator hooks. |
| // |
| |
| MachineBasicBlock::iterator |
| LiveIntervals::getLastSplitPoint(const LiveInterval &li, |
| MachineBasicBlock *mbb) const { |
| const MachineBasicBlock *lpad = mbb->getLandingPadSuccessor(); |
| |
| // If li is not live into a landing pad, we can insert spill code before the |
| // first terminator. |
| if (!lpad || !isLiveInToMBB(li, lpad)) |
| return mbb->getFirstTerminator(); |
| |
| // When there is a landing pad, spill code must go before the call instruction |
| // that can throw. |
| MachineBasicBlock::iterator I = mbb->end(), B = mbb->begin(); |
| while (I != B) { |
| --I; |
| if (I->getDesc().isCall()) |
| return I; |
| } |
| // The block contains no calls that can throw, so use the first terminator. |
| return mbb->getFirstTerminator(); |
| } |
| |
| void LiveIntervals::addKillFlags() { |
| for (iterator I = begin(), E = end(); I != E; ++I) { |
| unsigned Reg = I->first; |
| if (TargetRegisterInfo::isPhysicalRegister(Reg)) |
| continue; |
| if (mri_->reg_nodbg_empty(Reg)) |
| continue; |
| LiveInterval *LI = I->second; |
| |
| // Every instruction that kills Reg corresponds to a live range end point. |
| for (LiveInterval::iterator RI = LI->begin(), RE = LI->end(); RI != RE; |
| ++RI) { |
| // A block index indicates an MBB edge. |
| if (RI->end.isBlock()) |
| continue; |
| MachineInstr *MI = getInstructionFromIndex(RI->end); |
| if (!MI) |
| continue; |
| MI->addRegisterKilled(Reg, NULL); |
| } |
| } |
| } |
| |
| /// getReMatImplicitUse - If the remat definition MI has one (for now, we only |
| /// allow one) virtual register operand, then its uses are implicitly using |
| /// the register. Returns the virtual register. |
| unsigned LiveIntervals::getReMatImplicitUse(const LiveInterval &li, |
| MachineInstr *MI) const { |
| unsigned RegOp = 0; |
| for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg() || !MO.isUse()) |
| continue; |
| unsigned Reg = MO.getReg(); |
| if (Reg == 0 || Reg == li.reg) |
| continue; |
| |
| if (TargetRegisterInfo::isPhysicalRegister(Reg) && |
| !allocatableRegs_[Reg]) |
| continue; |
| // FIXME: For now, only remat MI with at most one register operand. |
| assert(!RegOp && |
| "Can't rematerialize instruction with multiple register operand!"); |
| RegOp = MO.getReg(); |
| #ifndef NDEBUG |
| break; |
| #endif |
| } |
| return RegOp; |
| } |
| |
| /// isValNoAvailableAt - Return true if the val# of the specified interval |
| /// which reaches the given instruction also reaches the specified use index. |
| bool LiveIntervals::isValNoAvailableAt(const LiveInterval &li, MachineInstr *MI, |
| SlotIndex UseIdx) const { |
| VNInfo *UValNo = li.getVNInfoAt(UseIdx); |
| return UValNo && UValNo == li.getVNInfoAt(getInstructionIndex(MI)); |
| } |
| |
| /// isReMaterializable - Returns true if the definition MI of the specified |
| /// val# of the specified interval is re-materializable. |
| bool |
| LiveIntervals::isReMaterializable(const LiveInterval &li, |
| const VNInfo *ValNo, MachineInstr *MI, |
| const SmallVectorImpl<LiveInterval*> *SpillIs, |
| bool &isLoad) { |
| if (DisableReMat) |
| return false; |
| |
| if (!tii_->isTriviallyReMaterializable(MI, aa_)) |
| return false; |
| |
| // Target-specific code can mark an instruction as being rematerializable |
| // if it has one virtual reg use, though it had better be something like |
| // a PIC base register which is likely to be live everywhere. |
| unsigned ImpUse = getReMatImplicitUse(li, MI); |
| if (ImpUse) { |
| const LiveInterval &ImpLi = getInterval(ImpUse); |
| for (MachineRegisterInfo::use_nodbg_iterator |
| ri = mri_->use_nodbg_begin(li.reg), re = mri_->use_nodbg_end(); |
| ri != re; ++ri) { |
| MachineInstr *UseMI = &*ri; |
| SlotIndex UseIdx = getInstructionIndex(UseMI); |
| if (li.getVNInfoAt(UseIdx) != ValNo) |
| continue; |
| if (!isValNoAvailableAt(ImpLi, MI, UseIdx)) |
| return false; |
| } |
| |
| // If a register operand of the re-materialized instruction is going to |
| // be spilled next, then it's not legal to re-materialize this instruction. |
| if (SpillIs) |
| for (unsigned i = 0, e = SpillIs->size(); i != e; ++i) |
| if (ImpUse == (*SpillIs)[i]->reg) |
| return false; |
| } |
| return true; |
| } |
| |
| /// isReMaterializable - Returns true if every definition of MI of every |
| /// val# of the specified interval is re-materializable. |
| bool |
| LiveIntervals::isReMaterializable(const LiveInterval &li, |
| const SmallVectorImpl<LiveInterval*> *SpillIs, |
| bool &isLoad) { |
| isLoad = false; |
| for (LiveInterval::const_vni_iterator i = li.vni_begin(), e = li.vni_end(); |
| i != e; ++i) { |
| const VNInfo *VNI = *i; |
| if (VNI->isUnused()) |
| continue; // Dead val#. |
| // Is the def for the val# rematerializable? |
| MachineInstr *ReMatDefMI = getInstructionFromIndex(VNI->def); |
| if (!ReMatDefMI) |
| return false; |
| bool DefIsLoad = false; |
| if (!ReMatDefMI || |
| !isReMaterializable(li, VNI, ReMatDefMI, SpillIs, DefIsLoad)) |
| return false; |
| isLoad |= DefIsLoad; |
| } |
| return true; |
| } |
| |
| bool LiveIntervals::intervalIsInOneMBB(const LiveInterval &li) const { |
| LiveInterval::Ranges::const_iterator itr = li.ranges.begin(); |
| |
| MachineBasicBlock *mbb = indexes_->getMBBCoveringRange(itr->start, itr->end); |
| |
| if (mbb == 0) |
| return false; |
| |
| for (++itr; itr != li.ranges.end(); ++itr) { |
| MachineBasicBlock *mbb2 = |
| indexes_->getMBBCoveringRange(itr->start, itr->end); |
| |
| if (mbb2 != mbb) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| float |
| LiveIntervals::getSpillWeight(bool isDef, bool isUse, unsigned loopDepth) { |
| // Limit the loop depth ridiculousness. |
| if (loopDepth > 200) |
| loopDepth = 200; |
| |
| // The loop depth is used to roughly estimate the number of times the |
| // instruction is executed. Something like 10^d is simple, but will quickly |
| // overflow a float. This expression behaves like 10^d for small d, but is |
| // more tempered for large d. At d=200 we get 6.7e33 which leaves a bit of |
| // headroom before overflow. |
| // By the way, powf() might be unavailable here. For consistency, |
| // We may take pow(double,double). |
| float lc = std::pow(1 + (100.0 / (loopDepth + 10)), (double)loopDepth); |
| |
| return (isDef + isUse) * lc; |
| } |
| |
| LiveRange LiveIntervals::addLiveRangeToEndOfBlock(unsigned reg, |
| MachineInstr* startInst) { |
| LiveInterval& Interval = getOrCreateInterval(reg); |
| VNInfo* VN = Interval.getNextValue( |
| SlotIndex(getInstructionIndex(startInst).getRegSlot()), |
| startInst, getVNInfoAllocator()); |
| VN->setHasPHIKill(true); |
| LiveRange LR( |
| SlotIndex(getInstructionIndex(startInst).getRegSlot()), |
| getMBBEndIdx(startInst->getParent()), VN); |
| Interval.addRange(LR); |
| |
| return LR; |
| } |
| |