| //===- AggressiveAntiDepBreaker.cpp - Anti-dep breaker --------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "AggressiveAntiDepBreaker.h" |
| #include "llvm/ADT/ArrayRef.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/ADT/iterator_range.h" |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/MachineFrameInfo.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/MachineOperand.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/CodeGen/RegisterClassInfo.h" |
| #include "llvm/CodeGen/ScheduleDAG.h" |
| #include "llvm/CodeGen/TargetInstrInfo.h" |
| #include "llvm/CodeGen/TargetRegisterInfo.h" |
| #include "llvm/MC/MCInstrDesc.h" |
| #include "llvm/MC/MCRegisterInfo.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/MachineValueType.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <cassert> |
| #include <utility> |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "post-RA-sched" |
| |
| // 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) |
| : MF(MFi), MRI(MF.getRegInfo()), TII(MF.getSubtarget().getInstrInfo()), |
| TRI(MF.getSubtarget().getRegisterInfo()), RegClassInfo(RCI) { |
| /* 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; |
| } |
| |
| LLVM_DEBUG(dbgs() << "AntiDep Critical-Path Registers:"); |
| LLVM_DEBUG(for (unsigned r |
| : CriticalPathSet.set_bits()) dbgs() |
| << " " << printReg(r, TRI)); |
| LLVM_DEBUG(dbgs() << '\n'); |
| } |
| |
| AggressiveAntiDepBreaker::~AggressiveAntiDepBreaker() { |
| delete State; |
| } |
| |
| void AggressiveAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { |
| assert(!State); |
| State = new AggressiveAntiDepState(TRI->getNumRegs(), BB); |
| |
| bool IsReturnBlock = BB->isReturnBlock(); |
| std::vector<unsigned> &KillIndices = State->GetKillIndices(); |
| std::vector<unsigned> &DefIndices = State->GetDefIndices(); |
| |
| // Examine the live-in regs of all successors. |
| for (MachineBasicBlock *Succ : BB->successors()) |
| for (const auto &LI : Succ->liveins()) { |
| for (MCRegAliasIterator AI(LI.PhysReg, 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(MF); |
| for (const MCPhysReg *I = MF.getRegInfo().getCalleeSavedRegs(); *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 = nullptr; |
| } |
| |
| 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); |
| |
| LLVM_DEBUG(dbgs() << "Observe: "); |
| LLVM_DEBUG(MI.dump()); |
| LLVM_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)) { |
| LLVM_DEBUG(if (State->GetGroup(Reg) != 0) dbgs() |
| << " " << printReg(Reg, TRI) << "=g" << State->GetGroup(Reg) |
| << "->g0(region live-out)"); |
| State->UnionGroups(Reg, 0); |
| } else if ((DefIndices[Reg] < InsertPosIndex) |
| && (DefIndices[Reg] >= Count)) { |
| DefIndices[Reg] = Count; |
| } |
| } |
| LLVM_DEBUG(dbgs() << '\n'); |
| } |
| |
| bool AggressiveAntiDepBreaker::IsImplicitDefUse(MachineInstr &MI, |
| MachineOperand &MO) { |
| if (!MO.isReg() || !MO.isImplicit()) |
| return false; |
| |
| Register Reg = MO.getReg(); |
| if (Reg == 0) |
| return false; |
| |
| MachineOperand *Op = nullptr; |
| if (MO.isDef()) |
| Op = MI.findRegisterUseOperand(Reg, true); |
| else |
| Op = MI.findRegisterDefOperand(Reg); |
| |
| return(Op && 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 Register Reg = MO.getReg(); |
| for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true); |
| 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 (const SDep &Pred : SU->Preds) { |
| if ((Pred.getKind() == SDep::Anti) || (Pred.getKind() == SDep::Output)) { |
| if (RegSet.insert(Pred.getReg()).second) |
| Edges.push_back(&Pred); |
| } |
| } |
| } |
| |
| /// CriticalPathStep - Return the next SUnit after SU on the bottom-up |
| /// critical path. |
| static const SUnit *CriticalPathStep(const SUnit *SU) { |
| const SDep *Next = nullptr; |
| unsigned NextDepth = 0; |
| // Find the predecessor edge with the greatest depth. |
| if (SU) { |
| for (const SDep &Pred : SU->Preds) { |
| const SUnit *PredSU = Pred.getSUnit(); |
| unsigned PredLatency = Pred.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 && Pred.getKind() == SDep::Anti)) { |
| NextDepth = PredTotalLatency; |
| Next = &Pred; |
| } |
| } |
| } |
| |
| return (Next) ? Next->getSUnit() : nullptr; |
| } |
| |
| 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(); |
| |
| // FIXME: We must leave subregisters of live super registers as live, so that |
| // we don't clear out the register tracking information for subregisters of |
| // super registers we're still tracking (and with which we're unioning |
| // subregister definitions). |
| for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) |
| if (TRI->isSuperRegister(Reg, *AI) && State->IsLive(*AI)) { |
| LLVM_DEBUG(if (!header && footer) dbgs() << footer); |
| return; |
| } |
| |
| if (!State->IsLive(Reg)) { |
| KillIndices[Reg] = KillIdx; |
| DefIndices[Reg] = ~0u; |
| RegRefs.erase(Reg); |
| State->LeaveGroup(Reg); |
| LLVM_DEBUG(if (header) { |
| dbgs() << header << printReg(Reg, TRI); |
| header = nullptr; |
| }); |
| LLVM_DEBUG(dbgs() << "->g" << State->GetGroup(Reg) << tag); |
| // Repeat for subregisters. Note that we only do this if the superregister |
| // was not live because otherwise, regardless whether we have an explicit |
| // use of the subregister, the subregister's contents are needed for the |
| // uses of the superregister. |
| 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); |
| LLVM_DEBUG(if (header) { |
| dbgs() << header << printReg(Reg, TRI); |
| header = nullptr; |
| }); |
| LLVM_DEBUG(dbgs() << " " << printReg(SubregReg, TRI) << "->g" |
| << State->GetGroup(SubregReg) << tag); |
| } |
| } |
| } |
| |
| LLVM_DEBUG(if (!header && footer) 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 (const MachineOperand &MO : MI.operands()) { |
| if (!MO.isReg() || !MO.isDef()) continue; |
| Register Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| |
| HandleLastUse(Reg, Count + 1, "", "\tDead Def: ", "\n"); |
| } |
| |
| LLVM_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; |
| Register Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| |
| LLVM_DEBUG(dbgs() << " " << printReg(Reg, TRI) << "=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). Inline assembly may |
| // reference either system calls or the register directly. Skip it until we |
| // can tell user specified registers from compiler-specified. |
| if (MI.isCall() || MI.hasExtraDefRegAllocReq() || TII->isPredicated(MI) || |
| MI.isInlineAsm()) { |
| LLVM_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); |
| LLVM_DEBUG(dbgs() << "->g" << State->GetGroup(Reg) << "(via " |
| << printReg(AliasReg, TRI) << ")"); |
| } |
| } |
| |
| // Note register reference... |
| const TargetRegisterClass *RC = nullptr; |
| 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)); |
| } |
| |
| LLVM_DEBUG(dbgs() << '\n'); |
| |
| // Scan the register defs for this instruction and update |
| // live-ranges. |
| for (const MachineOperand &MO : MI.operands()) { |
| if (!MO.isReg() || !MO.isDef()) continue; |
| Register 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) { |
| // We need to be careful here not to define already-live super registers. |
| // If the super register is already live, then this definition is not |
| // a definition of the whole super register (just a partial insertion |
| // into it). Earlier subregister definitions (which we've not yet visited |
| // because we're iterating bottom-up) need to be linked to the same group |
| // as this definition. |
| if (TRI->isSuperRegister(Reg, *AI) && State->IsLive(*AI)) |
| continue; |
| |
| DefIndices[*AI] = Count; |
| } |
| } |
| } |
| |
| void AggressiveAntiDepBreaker::ScanInstruction(MachineInstr &MI, |
| unsigned Count) { |
| LLVM_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). |
| // Inline Assembly register uses also cannot be safely changed. |
| // 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 = LDR %sp, %reg0, 92, 14, %reg0; mem:LD4[FixedStack14] |
| // ... |
| // STR %r0, killed %r6, %reg0, 0, 0, %cpsr; mem:ST4[%395] |
| // %r6 = LDR %sp, %reg0, 100, 0, %cpsr; mem:LD4[FixedStack12] |
| // STR %r0, killed %r6, %reg0, 0, 14, %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) || MI.isInlineAsm(); |
| |
| // 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; |
| Register Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| |
| LLVM_DEBUG(dbgs() << " " << printReg(Reg, TRI) << "=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) { |
| LLVM_DEBUG(if (State->GetGroup(Reg) != 0) dbgs() << "->g0(alloc-req)"); |
| State->UnionGroups(Reg, 0); |
| } |
| |
| // Note register reference... |
| const TargetRegisterClass *RC = nullptr; |
| 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)); |
| } |
| |
| LLVM_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()) { |
| LLVM_DEBUG(dbgs() << "\tKill Group:"); |
| |
| unsigned FirstReg = 0; |
| for (const MachineOperand &MO : MI.operands()) { |
| if (!MO.isReg()) continue; |
| Register Reg = MO.getReg(); |
| if (Reg == 0) continue; |
| |
| if (FirstReg != 0) { |
| LLVM_DEBUG(dbgs() << "=" << printReg(Reg, TRI)); |
| State->UnionGroups(FirstReg, Reg); |
| } else { |
| LLVM_DEBUG(dbgs() << " " << printReg(Reg, TRI)); |
| FirstReg = Reg; |
| } |
| } |
| |
| LLVM_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. |
| for (const auto &Q : make_range(State->GetRegRefs().equal_range(Reg))) { |
| const TargetRegisterClass *RC = Q.second.RC; |
| if (!RC) continue; |
| |
| BitVector RCBV = TRI->getAllocatableSet(MF, RC); |
| if (first) { |
| BV |= RCBV; |
| first = false; |
| } else { |
| BV &= RCBV; |
| } |
| |
| LLVM_DEBUG(dbgs() << " " << TRI->getRegClassName(RC)); |
| } |
| |
| 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.empty() && "Empty register group!"); |
| if (Regs.empty()) |
| 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. |
| LLVM_DEBUG(dbgs() << "\tRename Candidates for Group g" << AntiDepGroupIndex |
| << ":\n"); |
| std::map<unsigned, BitVector> RenameRegisterMap; |
| unsigned SuperReg = 0; |
| for (unsigned Reg : Regs) { |
| if ((SuperReg == 0) || TRI->isSuperRegister(SuperReg, Reg)) |
| SuperReg = Reg; |
| |
| // If Reg has any references, then collect possible rename regs |
| if (RegRefs.count(Reg) > 0) { |
| LLVM_DEBUG(dbgs() << "\t\t" << printReg(Reg, TRI) << ":"); |
| |
| BitVector &BV = RenameRegisterMap[Reg]; |
| assert(BV.empty()); |
| BV = GetRenameRegisters(Reg); |
| |
| LLVM_DEBUG({ |
| dbgs() << " ::"; |
| for (unsigned r : BV.set_bits()) |
| dbgs() << " " << printReg(r, TRI); |
| dbgs() << "\n"; |
| }); |
| } |
| } |
| |
| // All group registers should be a subreg of SuperReg. |
| for (unsigned Reg : Regs) { |
| if (Reg == SuperReg) continue; |
| bool IsSub = TRI->isSubRegister(SuperReg, Reg); |
| // FIXME: remove this once PR18663 has been properly fixed. For now, |
| // return a conservative answer: |
| // 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 " << printReg(SuperReg, TRI) |
| << " 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()) { |
| LLVM_DEBUG(dbgs() << "\tEmpty Super Regclass!!\n"); |
| return false; |
| } |
| |
| LLVM_DEBUG(dbgs() << "\tFind Registers:"); |
| |
| 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; |
| |
| LLVM_DEBUG(dbgs() << " [" << printReg(NewSuperReg, TRI) << ':'); |
| 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 Reg : Regs) { |
| unsigned NewReg = 0; |
| if (Reg == SuperReg) { |
| NewReg = NewSuperReg; |
| } else { |
| unsigned NewSubRegIdx = TRI->getSubRegIndex(SuperReg, Reg); |
| if (NewSubRegIdx != 0) |
| NewReg = TRI->getSubReg(NewSuperReg, NewSubRegIdx); |
| } |
| |
| LLVM_DEBUG(dbgs() << " " << printReg(NewReg, TRI)); |
| |
| // Check if Reg can be renamed to NewReg. |
| if (!RenameRegisterMap[Reg].test(NewReg)) { |
| LLVM_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])) { |
| LLVM_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])) { |
| LLVM_DEBUG(dbgs() |
| << "(alias " << printReg(AliasReg, TRI) << " live)"); |
| found = true; |
| break; |
| } |
| } |
| if (found) |
| goto next_super_reg; |
| } |
| |
| // We cannot rename 'Reg' to 'NewReg' if one of the uses of 'Reg' also |
| // defines 'NewReg' via an early-clobber operand. |
| for (const auto &Q : make_range(RegRefs.equal_range(Reg))) { |
| MachineInstr *UseMI = Q.second.Operand->getParent(); |
| int Idx = UseMI->findRegisterDefOperandIdx(NewReg, false, true, TRI); |
| if (Idx == -1) |
| continue; |
| |
| if (UseMI->getOperand(Idx).isEarlyClobber()) { |
| LLVM_DEBUG(dbgs() << "(ec)"); |
| goto next_super_reg; |
| } |
| } |
| |
| // Also, we cannot rename 'Reg' to 'NewReg' if the instruction defining |
| // 'Reg' is an early-clobber define and that instruction also uses |
| // 'NewReg'. |
| for (const auto &Q : make_range(RegRefs.equal_range(Reg))) { |
| if (!Q.second.Operand->isDef() || !Q.second.Operand->isEarlyClobber()) |
| continue; |
| |
| MachineInstr *DefMI = Q.second.Operand->getParent(); |
| if (DefMI->readsRegister(NewReg, TRI)) { |
| LLVM_DEBUG(dbgs() << "(ec)"); |
| 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)); |
| LLVM_DEBUG(dbgs() << "]\n"); |
| return true; |
| |
| next_super_reg: |
| LLVM_DEBUG(dbgs() << ']'); |
| } while (R != EndR); |
| |
| LLVM_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 (const SUnit &SU : SUnits) |
| MISUnitMap.insert(std::make_pair(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 = nullptr; |
| MachineInstr *CriticalPathMI = nullptr; |
| if (CriticalPathSet.any()) { |
| for (const SUnit &SU : SUnits) { |
| if (!CriticalPathSU || |
| ((SU.getDepth() + SU.Latency) > |
| (CriticalPathSU->getDepth() + CriticalPathSU->Latency))) { |
| CriticalPathSU = &SU; |
| } |
| } |
| assert(CriticalPathSU && "Failed to find SUnit critical path"); |
| CriticalPathMI = CriticalPathSU->getInstr(); |
| } |
| |
| #ifndef NDEBUG |
| LLVM_DEBUG(dbgs() << "\n===== Aggressive anti-dependency breaking\n"); |
| LLVM_DEBUG(dbgs() << "Available regs:"); |
| for (unsigned Reg = 0; Reg < TRI->getNumRegs(); ++Reg) { |
| if (!State->IsLive(Reg)) |
| LLVM_DEBUG(dbgs() << " " << printReg(Reg, TRI)); |
| } |
| LLVM_DEBUG(dbgs() << '\n'); |
| #endif |
| |
| BitVector RegAliases(TRI->getNumRegs()); |
| |
| // 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.isDebugInstr()) |
| continue; |
| |
| LLVM_DEBUG(dbgs() << "Anti: "); |
| LLVM_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 = nullptr; |
| if (&MI == CriticalPathMI) { |
| CriticalPathSU = CriticalPathStep(CriticalPathSU); |
| CriticalPathMI = (CriticalPathSU) ? CriticalPathSU->getInstr() : nullptr; |
| } else if (CriticalPathSet.any()) { |
| 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 (const SDep *Edge : Edges) { |
| SUnit *NextSU = Edge->getSUnit(); |
| |
| if ((Edge->getKind() != SDep::Anti) && |
| (Edge->getKind() != SDep::Output)) continue; |
| |
| unsigned AntiDepReg = Edge->getReg(); |
| LLVM_DEBUG(dbgs() << "\tAntidep reg: " << printReg(AntiDepReg, TRI)); |
| assert(AntiDepReg != 0 && "Anti-dependence on reg0?"); |
| |
| if (!MRI.isAllocatable(AntiDepReg)) { |
| // Don't break anti-dependencies on non-allocatable registers. |
| LLVM_DEBUG(dbgs() << " (non-allocatable)\n"); |
| continue; |
| } else if (ExcludeRegs && ExcludeRegs->test(AntiDepReg)) { |
| // Don't break anti-dependencies for critical path registers |
| // if not on the critical path |
| LLVM_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. |
| LLVM_DEBUG(dbgs() << " (passthru)\n"); |
| continue; |
| } else { |
| // No anti-dep breaking for implicit deps |
| MachineOperand *AntiDepOp = MI.findRegisterDefOperand(AntiDepReg); |
| assert(AntiDepOp && "Can't find index for defined register operand"); |
| if (!AntiDepOp || AntiDepOp->isImplicit()) { |
| LLVM_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 (const SDep &Pred : PathSU->Preds) { |
| if (Pred.getSUnit() == NextSU ? (Pred.getKind() != SDep::Anti || |
| Pred.getReg() != AntiDepReg) |
| : (Pred.getKind() == SDep::Data && |
| Pred.getReg() == AntiDepReg)) { |
| AntiDepReg = 0; |
| break; |
| } |
| } |
| for (const SDep &Pred : PathSU->Preds) { |
| if ((Pred.getSUnit() == NextSU) && (Pred.getKind() != SDep::Anti) && |
| (Pred.getKind() != SDep::Output)) { |
| LLVM_DEBUG(dbgs() << " (real dependency)\n"); |
| AntiDepReg = 0; |
| break; |
| } else if ((Pred.getSUnit() != NextSU) && |
| (Pred.getKind() == SDep::Data) && |
| (Pred.getReg() == AntiDepReg)) { |
| LLVM_DEBUG(dbgs() << " (other dependency)\n"); |
| AntiDepReg = 0; |
| break; |
| } |
| } |
| |
| if (AntiDepReg == 0) continue; |
| |
| // If the definition of the anti-dependency register does not start |
| // a new live range, bail out. This can happen if the anti-dep |
| // register is a sub-register of another register whose live range |
| // spans over PathSU. In such case, PathSU defines only a part of |
| // the larger register. |
| RegAliases.reset(); |
| for (MCRegAliasIterator AI(AntiDepReg, TRI, true); AI.isValid(); ++AI) |
| RegAliases.set(*AI); |
| for (SDep S : PathSU->Succs) { |
| SDep::Kind K = S.getKind(); |
| if (K != SDep::Data && K != SDep::Output && K != SDep::Anti) |
| continue; |
| unsigned R = S.getReg(); |
| if (!RegAliases[R]) |
| continue; |
| if (R == AntiDepReg || TRI->isSubRegister(AntiDepReg, R)) |
| continue; |
| 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) { |
| LLVM_DEBUG(dbgs() << " (zero group)\n"); |
| continue; |
| } |
| |
| LLVM_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)) { |
| LLVM_DEBUG(dbgs() << "\tBreaking anti-dependence edge on " |
| << printReg(AntiDepReg, TRI) << ":"); |
| |
| // Handle each group register... |
| for (const auto &P : RenameMap) { |
| unsigned CurrReg = P.first; |
| unsigned NewReg = P.second; |
| |
| LLVM_DEBUG(dbgs() << " " << printReg(CurrReg, TRI) << "->" |
| << printReg(NewReg, TRI) << "(" |
| << RegRefs.count(CurrReg) << " refs)"); |
| |
| // Update the references to the old register CurrReg to |
| // refer to the new register NewReg. |
| for (const auto &Q : make_range(RegRefs.equal_range(CurrReg))) { |
| 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; |
| UpdateDbgValues(DbgValues, Q.second.Operand->getParent(), |
| 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; |
| LLVM_DEBUG(dbgs() << '\n'); |
| } |
| } |
| } |
| |
| ScanInstruction(MI, Count); |
| } |
| |
| return Broken; |
| } |
| |
| AntiDepBreaker *llvm::createAggressiveAntiDepBreaker( |
| MachineFunction &MFi, const RegisterClassInfo &RCI, |
| TargetSubtargetInfo::RegClassVector &CriticalPathRCs) { |
| return new AggressiveAntiDepBreaker(MFi, RCI, CriticalPathRCs); |
| } |
