| //===----- AggressiveAntiDepBreaker.cpp - Anti-dep breaker ----------------===// |
| // |
| // 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 AggressiveAntiDepBreaker class, which |
| // implements register anti-dependence breaking during post-RA |
| // scheduling. It attempts to break all anti-dependencies within a |
| // block. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "post-RA-sched" |
| #include "AggressiveAntiDepBreaker.h" |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/MachineFrameInfo.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/RegisterClassInfo.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Target/TargetRegisterInfo.h" |
| using namespace llvm; |
| |
| // If DebugDiv > 0 then only break antidep with (ID % DebugDiv) == DebugMod |
| static cl::opt<int> |
| DebugDiv("agg-antidep-debugdiv", |
| cl::desc("Debug control for aggressive anti-dep breaker"), |
| cl::init(0), cl::Hidden); |
| static cl::opt<int> |
| DebugMod("agg-antidep-debugmod", |
| cl::desc("Debug control for aggressive anti-dep breaker"), |
| cl::init(0), cl::Hidden); |
| |
| AggressiveAntiDepState::AggressiveAntiDepState(const unsigned TargetRegs, |
| MachineBasicBlock *BB) : |
| NumTargetRegs(TargetRegs), GroupNodes(TargetRegs, 0), |
| GroupNodeIndices(TargetRegs, 0), |
| KillIndices(TargetRegs, 0), |
| DefIndices(TargetRegs, 0) |
| { |
| const unsigned BBSize = BB->size(); |
| for (unsigned i = 0; i < NumTargetRegs; ++i) { |
| // Initialize all registers to be in their own group. Initially we |
| // assign the register to the same-indexed GroupNode. |
| GroupNodeIndices[i] = i; |
| // Initialize the indices to indicate that no registers are live. |
| KillIndices[i] = ~0u; |
| DefIndices[i] = BBSize; |
| } |
| } |
| |
| unsigned AggressiveAntiDepState::GetGroup(unsigned Reg) { |
| unsigned Node = GroupNodeIndices[Reg]; |
| while (GroupNodes[Node] != Node) |
| Node = GroupNodes[Node]; |
| |
| return Node; |
| } |
| |
| void AggressiveAntiDepState::GetGroupRegs( |
| unsigned Group, |
| std::vector<unsigned> &Regs, |
| std::multimap<unsigned, AggressiveAntiDepState::RegisterReference> *RegRefs) |
| { |
| for (unsigned Reg = 0; Reg != NumTargetRegs; ++Reg) { |
| if ((GetGroup(Reg) == Group) && (RegRefs->count(Reg) > 0)) |
| Regs.push_back(Reg); |
| } |
| } |
| |
| unsigned AggressiveAntiDepState::UnionGroups(unsigned Reg1, unsigned Reg2) |
| { |
| assert(GroupNodes[0] == 0 && "GroupNode 0 not parent!"); |
| assert(GroupNodeIndices[0] == 0 && "Reg 0 not in Group 0!"); |
| |
| // find group for each register |
| unsigned Group1 = GetGroup(Reg1); |
| unsigned Group2 = GetGroup(Reg2); |
| |
| // if either group is 0, then that must become the parent |
| unsigned Parent = (Group1 == 0) ? Group1 : Group2; |
| unsigned Other = (Parent == Group1) ? Group2 : Group1; |
| GroupNodes.at(Other) = Parent; |
| return Parent; |
| } |
| |
| unsigned AggressiveAntiDepState::LeaveGroup(unsigned Reg) |
| { |
| // Create a new GroupNode for Reg. Reg's existing GroupNode must |
| // stay as is because there could be other GroupNodes referring to |
| // it. |
| unsigned idx = GroupNodes.size(); |
| GroupNodes.push_back(idx); |
| GroupNodeIndices[Reg] = idx; |
| return idx; |
| } |
| |
| bool AggressiveAntiDepState::IsLive(unsigned Reg) |
| { |
| // KillIndex must be defined and DefIndex not defined for a register |
| // to be live. |
| return((KillIndices[Reg] != ~0u) && (DefIndices[Reg] == ~0u)); |
| } |
| |
| |
| |
| AggressiveAntiDepBreaker:: |
| AggressiveAntiDepBreaker(MachineFunction& MFi, |
| const RegisterClassInfo &RCI, |
| TargetSubtargetInfo::RegClassVector& CriticalPathRCs) : |
| AntiDepBreaker(), MF(MFi), |
| MRI(MF.getRegInfo()), |
| TII(MF.getTarget().getInstrInfo()), |
| TRI(MF.getTarget().getRegisterInfo()), |
| RegClassInfo(RCI), |
| State(NULL) { |
| /* Collect a bitset of all registers that are only broken if they |
| are on the critical path. */ |
| for (unsigned i = 0, e = CriticalPathRCs.size(); i < e; ++i) { |
| BitVector CPSet = TRI->getAllocatableSet(MF, CriticalPathRCs[i]); |
| if (CriticalPathSet.none()) |
| CriticalPathSet = CPSet; |
| else |
| CriticalPathSet |= CPSet; |
| } |
| |
| DEBUG(dbgs() << "AntiDep Critical-Path Registers:"); |
| DEBUG(for (int r = CriticalPathSet.find_first(); r != -1; |
| r = CriticalPathSet.find_next(r)) |
| dbgs() << " " << TRI->getName(r)); |
| DEBUG(dbgs() << '\n'); |
| } |
| |
| AggressiveAntiDepBreaker::~AggressiveAntiDepBreaker() { |
| delete State; |
| } |
| |
| void AggressiveAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { |
| assert(State == NULL); |
| State = new AggressiveAntiDepState(TRI->getNumRegs(), BB); |
| |
| bool IsReturnBlock = (!BB->empty() && BB->back().isReturn()); |
| std::vector<unsigned> &KillIndices = State->GetKillIndices(); |
| std::vector<unsigned> &DefIndices = State->GetDefIndices(); |
| |
| // Examine the live-in regs of all successors. |
| for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), |
| SE = BB->succ_end(); SI != SE; ++SI) |
| for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(), |
| E = (*SI)->livein_end(); I != E; ++I) { |
| for (MCRegAliasIterator AI(*I, TRI, true); AI.isValid(); ++AI) { |
| unsigned Reg = *AI; |
| State->UnionGroups(Reg, 0); |
| KillIndices[Reg] = BB->size(); |
| DefIndices[Reg] = ~0u; |
| } |
| } |
| |
| // Mark live-out callee-saved registers. In a return block this is |
| // all callee-saved registers. In non-return this is any |
| // callee-saved register that is not saved in the prolog. |
| const MachineFrameInfo *MFI = MF.getFrameInfo(); |
| BitVector Pristine = MFI->getPristineRegs(BB); |
| for (const uint16_t *I = TRI->getCalleeSavedRegs(&MF); *I; ++I) { |
| unsigned Reg = *I; |
| if (!IsReturnBlock && !Pristine.test(Reg)) continue; |
| for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) { |
| unsigned AliasReg = *AI; |
| State->UnionGroups(AliasReg, 0); |
| KillIndices[AliasReg] = BB->size(); |
| DefIndices[AliasReg] = ~0u; |
| } |
| } |
| } |
| |
| void AggressiveAntiDepBreaker::FinishBlock() { |
| delete State; |
| State = NULL; |
| } |
| |
| void AggressiveAntiDepBreaker::Observe(MachineInstr *MI, unsigned Count, |
| unsigned InsertPosIndex) { |
| assert(Count < InsertPosIndex && "Instruction index out of expected range!"); |
| |
| std::set<unsigned> PassthruRegs; |
| GetPassthruRegs(MI, PassthruRegs); |
| PrescanInstruction(MI, Count, PassthruRegs); |
| ScanInstruction(MI, Count); |
| |
| DEBUG(dbgs() << "Observe: "); |
| DEBUG(MI->dump()); |
| DEBUG(dbgs() << "\tRegs:"); |
| |
| std::vector<unsigned> &DefIndices = State->GetDefIndices(); |
| for (unsigned Reg = 0; Reg != TRI->getNumRegs(); ++Reg) { |
| // If Reg is current live, then mark that it can't be renamed as |
| // we don't know the extent of its live-range anymore (now that it |
| // has been scheduled). If it is not live but was defined in the |
| // previous schedule region, then set its def index to the most |
| // conservative location (i.e. the beginning of the previous |
| // schedule region). |
| if (State->IsLive(Reg)) { |
| DEBUG(if (State->GetGroup(Reg) != 0) |
| dbgs() << " " << TRI->getName(Reg) << "=g" << |
| State->GetGroup(Reg) << "->g0(region live-out)"); |
| State->UnionGroups(Reg, 0); |
| } else if ((DefIndices[Reg] < InsertPosIndex) |
| && (DefIndices[Reg] >= Count)) { |
| DefIndices[Reg] = Count; |
| } |
| } |
| DEBUG(dbgs() << '\n'); |
| } |
| |
| bool AggressiveAntiDepBreaker::IsImplicitDefUse(MachineInstr *MI, |
| MachineOperand& MO) |
| { |
| if (!MO.isReg() || !MO.isImplicit()) |
| return false; |
| |
| unsigned Reg = MO.getReg(); |
| if (Reg == 0) |
| return false; |
| |
| MachineOperand *Op = NULL; |
| if (MO.isDef()) |
| Op = MI->findRegisterUseOperand(Reg, true); |
| else |
| Op = MI->findRegisterDefOperand(Reg); |
| |
| return((Op != NULL) && Op->isImplicit()); |
| } |
| |
| void AggressiveAntiDepBreaker::GetPassthruRegs(MachineInstr *MI, |
| std::set<unsigned>& PassthruRegs) { |
| for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg()) continue; |
| if ((MO.isDef() && MI->isRegTiedToUseOperand(i)) || |
| IsImplicitDefUse(MI, MO)) { |
| const unsigned Reg = MO.getReg(); |
| PassthruRegs.insert(Reg); |
| for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) |
| PassthruRegs.insert(*SubRegs); |
| } |
| } |
| } |
| |
| /// AntiDepEdges - Return in Edges the anti- and output- dependencies |
| /// in SU that we want to consider for breaking. |
| static void AntiDepEdges(const SUnit *SU, std::vector<const SDep*>& Edges) { |
| SmallSet<unsigned, 4> RegSet; |
| for (SUnit::const_pred_iterator P = SU->Preds.begin(), PE = SU->Preds.end(); |
| P != PE; ++P) { |
| if ((P->getKind() == SDep::Anti) || (P->getKind() == SDep::Output)) { |
| unsigned Reg = P->getReg(); |
| if (RegSet.count(Reg) == 0) { |
| Edges.push_back(&*P); |
| RegSet.insert(Reg); |
| } |
| } |
| } |
| } |
| |
| /// CriticalPathStep - Return the next SUnit after SU on the bottom-up |
| /// critical path. |
| static const SUnit *CriticalPathStep(const SUnit *SU) { |
| const SDep *Next = 0; |
| unsigned NextDepth = 0; |
| // Find the predecessor edge with the greatest depth. |
| if (SU != 0) { |
| for (SUnit::const_pred_iterator P = SU->Preds.begin(), PE = SU->Preds.end(); |
| P != PE; ++P) { |
| const SUnit *PredSU = P->getSUnit(); |
| unsigned PredLatency = P->getLatency(); |
| unsigned PredTotalLatency = PredSU->getDepth() + PredLatency; |
| // In the case of a latency tie, prefer an anti-dependency edge over |
| // other types of edges. |
| if (NextDepth < PredTotalLatency || |
| (NextDepth == PredTotalLatency && P->getKind() == SDep::Anti)) { |
| NextDepth = PredTotalLatency; |
| Next = &*P; |
| } |
| } |
| } |
| |
| return (Next) ? Next->getSUnit() : 0; |
| } |
| |
| void AggressiveAntiDepBreaker::HandleLastUse(unsigned Reg, unsigned KillIdx, |
| const char *tag, |
| const char *header, |
| const char *footer) { |
| std::vector<unsigned> &KillIndices = State->GetKillIndices(); |
| std::vector<unsigned> &DefIndices = State->GetDefIndices(); |
| std::multimap<unsigned, AggressiveAntiDepState::RegisterReference>& |
| RegRefs = State->GetRegRefs(); |
| |
| if (!State->IsLive(Reg)) { |
| KillIndices[Reg] = KillIdx; |
| DefIndices[Reg] = ~0u; |
| RegRefs.erase(Reg); |
| State->LeaveGroup(Reg); |
| DEBUG(if (header != NULL) { |
| dbgs() << header << TRI->getName(Reg); header = NULL; }); |
| DEBUG(dbgs() << "->g" << State->GetGroup(Reg) << tag); |
| } |
| // Repeat for subregisters. |
| for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) { |
| unsigned SubregReg = *SubRegs; |
| if (!State->IsLive(SubregReg)) { |
| KillIndices[SubregReg] = KillIdx; |
| DefIndices[SubregReg] = ~0u; |
| RegRefs.erase(SubregReg); |
| State->LeaveGroup(SubregReg); |
| DEBUG(if (header != NULL) { |
| dbgs() << header << TRI->getName(Reg); header = NULL; }); |
| DEBUG(dbgs() << " " << TRI->getName(SubregReg) << "->g" << |
| State->GetGroup(SubregReg) << tag); |
| } |
| } |
| |
| DEBUG(if ((header == NULL) && (footer != NULL)) dbgs() << footer); |
| } |
| |
| void AggressiveAntiDepBreaker::PrescanInstruction(MachineInstr *MI, |
| unsigned Count, |
| std::set<unsigned>& PassthruRegs) { |
| std::vector<unsigned> &DefIndices = State->GetDefIndices(); |
| std::multimap<unsigned, AggressiveAntiDepState::RegisterReference>& |
| RegRefs = State->GetRegRefs(); |
| |
| // Handle dead defs by simulating a last-use of the register just |
| // after the def. A dead def can occur because the def is truly |
| // dead, or because only a subregister is live at the def. If we |
| // don't do this the dead def will be incorrectly merged into the |
| // previous def. |
| for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg() || !MO.isDef()) continue; |
| unsigned Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| |
| HandleLastUse(Reg, Count + 1, "", "\tDead Def: ", "\n"); |
| } |
| |
| DEBUG(dbgs() << "\tDef Groups:"); |
| for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg() || !MO.isDef()) continue; |
| unsigned Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| |
| DEBUG(dbgs() << " " << TRI->getName(Reg) << "=g" << State->GetGroup(Reg)); |
| |
| // If MI's defs have a special allocation requirement, don't allow |
| // any def registers to be changed. Also assume all registers |
| // defined in a call must not be changed (ABI). |
| if (MI->isCall() || MI->hasExtraDefRegAllocReq() || |
| TII->isPredicated(MI)) { |
| DEBUG(if (State->GetGroup(Reg) != 0) dbgs() << "->g0(alloc-req)"); |
| State->UnionGroups(Reg, 0); |
| } |
| |
| // Any aliased that are live at this point are completely or |
| // partially defined here, so group those aliases with Reg. |
| for (MCRegAliasIterator AI(Reg, TRI, false); AI.isValid(); ++AI) { |
| unsigned AliasReg = *AI; |
| if (State->IsLive(AliasReg)) { |
| State->UnionGroups(Reg, AliasReg); |
| DEBUG(dbgs() << "->g" << State->GetGroup(Reg) << "(via " << |
| TRI->getName(AliasReg) << ")"); |
| } |
| } |
| |
| // Note register reference... |
| const TargetRegisterClass *RC = NULL; |
| if (i < MI->getDesc().getNumOperands()) |
| RC = TII->getRegClass(MI->getDesc(), i, TRI, MF); |
| AggressiveAntiDepState::RegisterReference RR = { &MO, RC }; |
| RegRefs.insert(std::make_pair(Reg, RR)); |
| } |
| |
| DEBUG(dbgs() << '\n'); |
| |
| // Scan the register defs for this instruction and update |
| // live-ranges. |
| for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg() || !MO.isDef()) continue; |
| unsigned Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| // Ignore KILLs and passthru registers for liveness... |
| if (MI->isKill() || (PassthruRegs.count(Reg) != 0)) |
| continue; |
| |
| // Update def for Reg and aliases. |
| for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) |
| DefIndices[*AI] = Count; |
| } |
| } |
| |
| void AggressiveAntiDepBreaker::ScanInstruction(MachineInstr *MI, |
| unsigned Count) { |
| DEBUG(dbgs() << "\tUse Groups:"); |
| std::multimap<unsigned, AggressiveAntiDepState::RegisterReference>& |
| RegRefs = State->GetRegRefs(); |
| |
| // If MI's uses have special allocation requirement, don't allow |
| // any use registers to be changed. Also assume all registers |
| // used in a call must not be changed (ABI). |
| // FIXME: The issue with predicated instruction is more complex. We are being |
| // conservatively here because the kill markers cannot be trusted after |
| // if-conversion: |
| // %R6<def> = LDR %SP, %reg0, 92, pred:14, pred:%reg0; mem:LD4[FixedStack14] |
| // ... |
| // STR %R0, %R6<kill>, %reg0, 0, pred:0, pred:%CPSR; mem:ST4[%395] |
| // %R6<def> = LDR %SP, %reg0, 100, pred:0, pred:%CPSR; mem:LD4[FixedStack12] |
| // STR %R0, %R6<kill>, %reg0, 0, pred:14, pred:%reg0; mem:ST4[%396](align=8) |
| // |
| // The first R6 kill is not really a kill since it's killed by a predicated |
| // instruction which may not be executed. The second R6 def may or may not |
| // re-define R6 so it's not safe to change it since the last R6 use cannot be |
| // changed. |
| bool Special = MI->isCall() || |
| MI->hasExtraSrcRegAllocReq() || |
| TII->isPredicated(MI); |
| |
| // Scan the register uses for this instruction and update |
| // live-ranges, groups and RegRefs. |
| 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) continue; |
| |
| DEBUG(dbgs() << " " << TRI->getName(Reg) << "=g" << |
| State->GetGroup(Reg)); |
| |
| // It wasn't previously live but now it is, this is a kill. Forget |
| // the previous live-range information and start a new live-range |
| // for the register. |
| HandleLastUse(Reg, Count, "(last-use)"); |
| |
| if (Special) { |
| DEBUG(if (State->GetGroup(Reg) != 0) dbgs() << "->g0(alloc-req)"); |
| State->UnionGroups(Reg, 0); |
| } |
| |
| // Note register reference... |
| const TargetRegisterClass *RC = NULL; |
| if (i < MI->getDesc().getNumOperands()) |
| RC = TII->getRegClass(MI->getDesc(), i, TRI, MF); |
| AggressiveAntiDepState::RegisterReference RR = { &MO, RC }; |
| RegRefs.insert(std::make_pair(Reg, RR)); |
| } |
| |
| DEBUG(dbgs() << '\n'); |
| |
| // Form a group of all defs and uses of a KILL instruction to ensure |
| // that all registers are renamed as a group. |
| if (MI->isKill()) { |
| DEBUG(dbgs() << "\tKill Group:"); |
| |
| unsigned FirstReg = 0; |
| for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg()) continue; |
| unsigned Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| |
| if (FirstReg != 0) { |
| DEBUG(dbgs() << "=" << TRI->getName(Reg)); |
| State->UnionGroups(FirstReg, Reg); |
| } else { |
| DEBUG(dbgs() << " " << TRI->getName(Reg)); |
| FirstReg = Reg; |
| } |
| } |
| |
| DEBUG(dbgs() << "->g" << State->GetGroup(FirstReg) << '\n'); |
| } |
| } |
| |
| BitVector AggressiveAntiDepBreaker::GetRenameRegisters(unsigned Reg) { |
| BitVector BV(TRI->getNumRegs(), false); |
| bool first = true; |
| |
| // Check all references that need rewriting for Reg. For each, use |
| // the corresponding register class to narrow the set of registers |
| // that are appropriate for renaming. |
| std::pair<std::multimap<unsigned, |
| AggressiveAntiDepState::RegisterReference>::iterator, |
| std::multimap<unsigned, |
| AggressiveAntiDepState::RegisterReference>::iterator> |
| Range = State->GetRegRefs().equal_range(Reg); |
| for (std::multimap<unsigned, |
| AggressiveAntiDepState::RegisterReference>::iterator Q = Range.first, |
| QE = Range.second; Q != QE; ++Q) { |
| const TargetRegisterClass *RC = Q->second.RC; |
| if (RC == NULL) continue; |
| |
| BitVector RCBV = TRI->getAllocatableSet(MF, RC); |
| if (first) { |
| BV |= RCBV; |
| first = false; |
| } else { |
| BV &= RCBV; |
| } |
| |
| DEBUG(dbgs() << " " << RC->getName()); |
| } |
| |
| return BV; |
| } |
| |
| bool AggressiveAntiDepBreaker::FindSuitableFreeRegisters( |
| unsigned AntiDepGroupIndex, |
| RenameOrderType& RenameOrder, |
| std::map<unsigned, unsigned> &RenameMap) { |
| std::vector<unsigned> &KillIndices = State->GetKillIndices(); |
| std::vector<unsigned> &DefIndices = State->GetDefIndices(); |
| std::multimap<unsigned, AggressiveAntiDepState::RegisterReference>& |
| RegRefs = State->GetRegRefs(); |
| |
| // Collect all referenced registers in the same group as |
| // AntiDepReg. These all need to be renamed together if we are to |
| // break the anti-dependence. |
| std::vector<unsigned> Regs; |
| State->GetGroupRegs(AntiDepGroupIndex, Regs, &RegRefs); |
| assert(Regs.size() > 0 && "Empty register group!"); |
| if (Regs.size() == 0) |
| return false; |
| |
| // Find the "superest" register in the group. At the same time, |
| // collect the BitVector of registers that can be used to rename |
| // each register. |
| DEBUG(dbgs() << "\tRename Candidates for Group g" << AntiDepGroupIndex |
| << ":\n"); |
| std::map<unsigned, BitVector> RenameRegisterMap; |
| unsigned SuperReg = 0; |
| for (unsigned i = 0, e = Regs.size(); i != e; ++i) { |
| unsigned Reg = Regs[i]; |
| if ((SuperReg == 0) || TRI->isSuperRegister(SuperReg, Reg)) |
| SuperReg = Reg; |
| |
| // If Reg has any references, then collect possible rename regs |
| if (RegRefs.count(Reg) > 0) { |
| DEBUG(dbgs() << "\t\t" << TRI->getName(Reg) << ":"); |
| |
| BitVector BV = GetRenameRegisters(Reg); |
| RenameRegisterMap.insert(std::pair<unsigned, BitVector>(Reg, BV)); |
| |
| DEBUG(dbgs() << " ::"); |
| DEBUG(for (int r = BV.find_first(); r != -1; r = BV.find_next(r)) |
| dbgs() << " " << TRI->getName(r)); |
| DEBUG(dbgs() << "\n"); |
| } |
| } |
| |
| // All group registers should be a subreg of SuperReg. |
| for (unsigned i = 0, e = Regs.size(); i != e; ++i) { |
| unsigned Reg = Regs[i]; |
| if (Reg == SuperReg) continue; |
| bool IsSub = TRI->isSubRegister(SuperReg, Reg); |
| assert(IsSub && "Expecting group subregister"); |
| if (!IsSub) |
| return false; |
| } |
| |
| #ifndef NDEBUG |
| // If DebugDiv > 0 then only rename (renamecnt % DebugDiv) == DebugMod |
| if (DebugDiv > 0) { |
| static int renamecnt = 0; |
| if (renamecnt++ % DebugDiv != DebugMod) |
| return false; |
| |
| dbgs() << "*** Performing rename " << TRI->getName(SuperReg) << |
| " for debug ***\n"; |
| } |
| #endif |
| |
| // Check each possible rename register for SuperReg in round-robin |
| // order. If that register is available, and the corresponding |
| // registers are available for the other group subregisters, then we |
| // can use those registers to rename. |
| |
| // FIXME: Using getMinimalPhysRegClass is very conservative. We should |
| // check every use of the register and find the largest register class |
| // that can be used in all of them. |
| const TargetRegisterClass *SuperRC = |
| TRI->getMinimalPhysRegClass(SuperReg, MVT::Other); |
| |
| ArrayRef<MCPhysReg> Order = RegClassInfo.getOrder(SuperRC); |
| if (Order.empty()) { |
| DEBUG(dbgs() << "\tEmpty Super Regclass!!\n"); |
| return false; |
| } |
| |
| DEBUG(dbgs() << "\tFind Registers:"); |
| |
| if (RenameOrder.count(SuperRC) == 0) |
| RenameOrder.insert(RenameOrderType::value_type(SuperRC, Order.size())); |
| |
| unsigned OrigR = RenameOrder[SuperRC]; |
| unsigned EndR = ((OrigR == Order.size()) ? 0 : OrigR); |
| unsigned R = OrigR; |
| do { |
| if (R == 0) R = Order.size(); |
| --R; |
| const unsigned NewSuperReg = Order[R]; |
| // Don't consider non-allocatable registers |
| if (!MRI.isAllocatable(NewSuperReg)) continue; |
| // Don't replace a register with itself. |
| if (NewSuperReg == SuperReg) continue; |
| |
| DEBUG(dbgs() << " [" << TRI->getName(NewSuperReg) << ':'); |
| RenameMap.clear(); |
| |
| // For each referenced group register (which must be a SuperReg or |
| // a subregister of SuperReg), find the corresponding subregister |
| // of NewSuperReg and make sure it is free to be renamed. |
| for (unsigned i = 0, e = Regs.size(); i != e; ++i) { |
| unsigned Reg = Regs[i]; |
| unsigned NewReg = 0; |
| if (Reg == SuperReg) { |
| NewReg = NewSuperReg; |
| } else { |
| unsigned NewSubRegIdx = TRI->getSubRegIndex(SuperReg, Reg); |
| if (NewSubRegIdx != 0) |
| NewReg = TRI->getSubReg(NewSuperReg, NewSubRegIdx); |
| } |
| |
| DEBUG(dbgs() << " " << TRI->getName(NewReg)); |
| |
| // Check if Reg can be renamed to NewReg. |
| BitVector BV = RenameRegisterMap[Reg]; |
| if (!BV.test(NewReg)) { |
| DEBUG(dbgs() << "(no rename)"); |
| goto next_super_reg; |
| } |
| |
| // If NewReg is dead and NewReg's most recent def is not before |
| // Regs's kill, it's safe to replace Reg with NewReg. We |
| // must also check all aliases of NewReg, because we can't define a |
| // register when any sub or super is already live. |
| if (State->IsLive(NewReg) || (KillIndices[Reg] > DefIndices[NewReg])) { |
| DEBUG(dbgs() << "(live)"); |
| goto next_super_reg; |
| } else { |
| bool found = false; |
| for (MCRegAliasIterator AI(NewReg, TRI, false); AI.isValid(); ++AI) { |
| unsigned AliasReg = *AI; |
| if (State->IsLive(AliasReg) || |
| (KillIndices[Reg] > DefIndices[AliasReg])) { |
| DEBUG(dbgs() << "(alias " << TRI->getName(AliasReg) << " live)"); |
| found = true; |
| break; |
| } |
| } |
| if (found) |
| goto next_super_reg; |
| } |
| |
| // Record that 'Reg' can be renamed to 'NewReg'. |
| RenameMap.insert(std::pair<unsigned, unsigned>(Reg, NewReg)); |
| } |
| |
| // If we fall-out here, then every register in the group can be |
| // renamed, as recorded in RenameMap. |
| RenameOrder.erase(SuperRC); |
| RenameOrder.insert(RenameOrderType::value_type(SuperRC, R)); |
| DEBUG(dbgs() << "]\n"); |
| return true; |
| |
| next_super_reg: |
| DEBUG(dbgs() << ']'); |
| } while (R != EndR); |
| |
| DEBUG(dbgs() << '\n'); |
| |
| // No registers are free and available! |
| return false; |
| } |
| |
| /// BreakAntiDependencies - Identifiy anti-dependencies within the |
| /// ScheduleDAG and break them by renaming registers. |
| /// |
| unsigned AggressiveAntiDepBreaker::BreakAntiDependencies( |
| const std::vector<SUnit>& SUnits, |
| MachineBasicBlock::iterator Begin, |
| MachineBasicBlock::iterator End, |
| unsigned InsertPosIndex, |
| DbgValueVector &DbgValues) { |
| |
| std::vector<unsigned> &KillIndices = State->GetKillIndices(); |
| std::vector<unsigned> &DefIndices = State->GetDefIndices(); |
| std::multimap<unsigned, AggressiveAntiDepState::RegisterReference>& |
| RegRefs = State->GetRegRefs(); |
| |
| // The code below assumes that there is at least one instruction, |
| // so just duck out immediately if the block is empty. |
| if (SUnits.empty()) return 0; |
| |
| // For each regclass the next register to use for renaming. |
| RenameOrderType RenameOrder; |
| |
| // ...need a map from MI to SUnit. |
| std::map<MachineInstr *, const SUnit *> MISUnitMap; |
| for (unsigned i = 0, e = SUnits.size(); i != e; ++i) { |
| const SUnit *SU = &SUnits[i]; |
| MISUnitMap.insert(std::pair<MachineInstr *, const SUnit *>(SU->getInstr(), |
| SU)); |
| } |
| |
| // Track progress along the critical path through the SUnit graph as |
| // we walk the instructions. This is needed for regclasses that only |
| // break critical-path anti-dependencies. |
| const SUnit *CriticalPathSU = 0; |
| MachineInstr *CriticalPathMI = 0; |
| if (CriticalPathSet.any()) { |
| for (unsigned i = 0, e = SUnits.size(); i != e; ++i) { |
| const SUnit *SU = &SUnits[i]; |
| if (!CriticalPathSU || |
| ((SU->getDepth() + SU->Latency) > |
| (CriticalPathSU->getDepth() + CriticalPathSU->Latency))) { |
| CriticalPathSU = SU; |
| } |
| } |
| |
| CriticalPathMI = CriticalPathSU->getInstr(); |
| } |
| |
| #ifndef NDEBUG |
| DEBUG(dbgs() << "\n===== Aggressive anti-dependency breaking\n"); |
| DEBUG(dbgs() << "Available regs:"); |
| for (unsigned Reg = 0; Reg < TRI->getNumRegs(); ++Reg) { |
| if (!State->IsLive(Reg)) |
| DEBUG(dbgs() << " " << TRI->getName(Reg)); |
| } |
| DEBUG(dbgs() << '\n'); |
| #endif |
| |
| // Attempt to break anti-dependence edges. Walk the instructions |
| // from the bottom up, tracking information about liveness as we go |
| // to help determine which registers are available. |
| unsigned Broken = 0; |
| unsigned Count = InsertPosIndex - 1; |
| for (MachineBasicBlock::iterator I = End, E = Begin; |
| I != E; --Count) { |
| MachineInstr *MI = --I; |
| |
| if (MI->isDebugValue()) |
| continue; |
| |
| DEBUG(dbgs() << "Anti: "); |
| DEBUG(MI->dump()); |
| |
| std::set<unsigned> PassthruRegs; |
| GetPassthruRegs(MI, PassthruRegs); |
| |
| // Process the defs in MI... |
| PrescanInstruction(MI, Count, PassthruRegs); |
| |
| // The dependence edges that represent anti- and output- |
| // dependencies that are candidates for breaking. |
| std::vector<const SDep *> Edges; |
| const SUnit *PathSU = MISUnitMap[MI]; |
| AntiDepEdges(PathSU, Edges); |
| |
| // If MI is not on the critical path, then we don't rename |
| // registers in the CriticalPathSet. |
| BitVector *ExcludeRegs = NULL; |
| if (MI == CriticalPathMI) { |
| CriticalPathSU = CriticalPathStep(CriticalPathSU); |
| CriticalPathMI = (CriticalPathSU) ? CriticalPathSU->getInstr() : 0; |
| } else { |
| ExcludeRegs = &CriticalPathSet; |
| } |
| |
| // Ignore KILL instructions (they form a group in ScanInstruction |
| // but don't cause any anti-dependence breaking themselves) |
| if (!MI->isKill()) { |
| // Attempt to break each anti-dependency... |
| for (unsigned i = 0, e = Edges.size(); i != e; ++i) { |
| const SDep *Edge = Edges[i]; |
| SUnit *NextSU = Edge->getSUnit(); |
| |
| if ((Edge->getKind() != SDep::Anti) && |
| (Edge->getKind() != SDep::Output)) continue; |
| |
| unsigned AntiDepReg = Edge->getReg(); |
| DEBUG(dbgs() << "\tAntidep reg: " << TRI->getName(AntiDepReg)); |
| assert(AntiDepReg != 0 && "Anti-dependence on reg0?"); |
| |
| if (!MRI.isAllocatable(AntiDepReg)) { |
| // Don't break anti-dependencies on non-allocatable registers. |
| DEBUG(dbgs() << " (non-allocatable)\n"); |
| continue; |
| } else if ((ExcludeRegs != NULL) && ExcludeRegs->test(AntiDepReg)) { |
| // Don't break anti-dependencies for critical path registers |
| // if not on the critical path |
| DEBUG(dbgs() << " (not critical-path)\n"); |
| continue; |
| } else if (PassthruRegs.count(AntiDepReg) != 0) { |
| // If the anti-dep register liveness "passes-thru", then |
| // don't try to change it. It will be changed along with |
| // the use if required to break an earlier antidep. |
| DEBUG(dbgs() << " (passthru)\n"); |
| continue; |
| } else { |
| // No anti-dep breaking for implicit deps |
| MachineOperand *AntiDepOp = MI->findRegisterDefOperand(AntiDepReg); |
| assert(AntiDepOp != NULL && |
| "Can't find index for defined register operand"); |
| if ((AntiDepOp == NULL) || AntiDepOp->isImplicit()) { |
| DEBUG(dbgs() << " (implicit)\n"); |
| continue; |
| } |
| |
| // If the SUnit has other dependencies on the SUnit that |
| // it anti-depends on, don't bother breaking the |
| // anti-dependency since those edges would prevent such |
| // units from being scheduled past each other |
| // regardless. |
| // |
| // Also, if there are dependencies on other SUnits with the |
| // same register as the anti-dependency, don't attempt to |
| // break it. |
| for (SUnit::const_pred_iterator P = PathSU->Preds.begin(), |
| PE = PathSU->Preds.end(); P != PE; ++P) { |
| if (P->getSUnit() == NextSU ? |
| (P->getKind() != SDep::Anti || P->getReg() != AntiDepReg) : |
| (P->getKind() == SDep::Data && P->getReg() == AntiDepReg)) { |
| AntiDepReg = 0; |
| break; |
| } |
| } |
| for (SUnit::const_pred_iterator P = PathSU->Preds.begin(), |
| PE = PathSU->Preds.end(); P != PE; ++P) { |
| if ((P->getSUnit() == NextSU) && (P->getKind() != SDep::Anti) && |
| (P->getKind() != SDep::Output)) { |
| DEBUG(dbgs() << " (real dependency)\n"); |
| AntiDepReg = 0; |
| break; |
| } else if ((P->getSUnit() != NextSU) && |
| (P->getKind() == SDep::Data) && |
| (P->getReg() == AntiDepReg)) { |
| DEBUG(dbgs() << " (other dependency)\n"); |
| AntiDepReg = 0; |
| break; |
| } |
| } |
| |
| if (AntiDepReg == 0) continue; |
| } |
| |
| assert(AntiDepReg != 0); |
| if (AntiDepReg == 0) continue; |
| |
| // Determine AntiDepReg's register group. |
| const unsigned GroupIndex = State->GetGroup(AntiDepReg); |
| if (GroupIndex == 0) { |
| DEBUG(dbgs() << " (zero group)\n"); |
| continue; |
| } |
| |
| DEBUG(dbgs() << '\n'); |
| |
| // Look for a suitable register to use to break the anti-dependence. |
| std::map<unsigned, unsigned> RenameMap; |
| if (FindSuitableFreeRegisters(GroupIndex, RenameOrder, RenameMap)) { |
| DEBUG(dbgs() << "\tBreaking anti-dependence edge on " |
| << TRI->getName(AntiDepReg) << ":"); |
| |
| // Handle each group register... |
| for (std::map<unsigned, unsigned>::iterator |
| S = RenameMap.begin(), E = RenameMap.end(); S != E; ++S) { |
| unsigned CurrReg = S->first; |
| unsigned NewReg = S->second; |
| |
| DEBUG(dbgs() << " " << TRI->getName(CurrReg) << "->" << |
| TRI->getName(NewReg) << "(" << |
| RegRefs.count(CurrReg) << " refs)"); |
| |
| // Update the references to the old register CurrReg to |
| // refer to the new register NewReg. |
| std::pair<std::multimap<unsigned, |
| AggressiveAntiDepState::RegisterReference>::iterator, |
| std::multimap<unsigned, |
| AggressiveAntiDepState::RegisterReference>::iterator> |
| Range = RegRefs.equal_range(CurrReg); |
| for (std::multimap<unsigned, |
| AggressiveAntiDepState::RegisterReference>::iterator |
| Q = Range.first, QE = Range.second; Q != QE; ++Q) { |
| Q->second.Operand->setReg(NewReg); |
| // If the SU for the instruction being updated has debug |
| // information related to the anti-dependency register, make |
| // sure to update that as well. |
| const SUnit *SU = MISUnitMap[Q->second.Operand->getParent()]; |
| if (!SU) continue; |
| for (DbgValueVector::iterator DVI = DbgValues.begin(), |
| DVE = DbgValues.end(); DVI != DVE; ++DVI) |
| if (DVI->second == Q->second.Operand->getParent()) |
| UpdateDbgValue(DVI->first, AntiDepReg, NewReg); |
| } |
| |
| // We just went back in time and modified history; the |
| // liveness information for CurrReg is now inconsistent. Set |
| // the state as if it were dead. |
| State->UnionGroups(NewReg, 0); |
| RegRefs.erase(NewReg); |
| DefIndices[NewReg] = DefIndices[CurrReg]; |
| KillIndices[NewReg] = KillIndices[CurrReg]; |
| |
| State->UnionGroups(CurrReg, 0); |
| RegRefs.erase(CurrReg); |
| DefIndices[CurrReg] = KillIndices[CurrReg]; |
| KillIndices[CurrReg] = ~0u; |
| assert(((KillIndices[CurrReg] == ~0u) != |
| (DefIndices[CurrReg] == ~0u)) && |
| "Kill and Def maps aren't consistent for AntiDepReg!"); |
| } |
| |
| ++Broken; |
| DEBUG(dbgs() << '\n'); |
| } |
| } |
| } |
| |
| ScanInstruction(MI, Count); |
| } |
| |
| return Broken; |
| } |
