1//=- llvm/CodeGen/DFAPacketizer.cpp - DFA Packetizer for VLIW -*- C++ -*-=====// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// This class implements a deterministic finite automaton (DFA) based 10// packetizing mechanism for VLIW architectures. It provides APIs to 11// determine whether there exists a legal mapping of instructions to 12// functional unit assignments in a packet. The DFA is auto-generated from 13// the target's Schedule.td file. 14// 15// A DFA consists of 3 major elements: states, inputs, and transitions. For 16// the packetizing mechanism, the input is the set of instruction classes for 17// a target. The state models all possible combinations of functional unit 18// consumption for a given set of instructions in a packet. A transition 19// models the addition of an instruction to a packet. In the DFA constructed 20// by this class, if an instruction can be added to a packet, then a valid 21// transition exists from the corresponding state. Invalid transitions 22// indicate that the instruction cannot be added to the current packet. 23// 24//===----------------------------------------------------------------------===// 25 26#include "llvm/CodeGen/DFAPacketizer.h" 27#include "llvm/CodeGen/MachineInstr.h" 28#include "llvm/CodeGen/MachineInstrBundle.h" 29#include "llvm/CodeGen/ScheduleDAGInstrs.h" 30#include "llvm/MC/MCInstrItineraries.h" 31#include "llvm/Target/TargetInstrInfo.h" 32using namespace llvm; 33 34// -------------------------------------------------------------------- 35// Definitions shared between DFAPacketizer.cpp and DFAPacketizerEmitter.cpp 36 37namespace { 38 DFAInput addDFAFuncUnits(DFAInput Inp, unsigned FuncUnits) { 39 return (Inp << DFA_MAX_RESOURCES) | FuncUnits; 40 } 41 42 /// Return the DFAInput for an instruction class input vector. 43 /// This function is used in both DFAPacketizer.cpp and in 44 /// DFAPacketizerEmitter.cpp. 45 DFAInput getDFAInsnInput(const std::vector<unsigned> &InsnClass) { 46 DFAInput InsnInput = 0; 47 assert ((InsnClass.size() <= DFA_MAX_RESTERMS) && 48 "Exceeded maximum number of DFA terms"); 49 for (auto U : InsnClass) 50 InsnInput = addDFAFuncUnits(InsnInput, U); 51 return InsnInput; 52 } 53} 54// -------------------------------------------------------------------- 55 56DFAPacketizer::DFAPacketizer(const InstrItineraryData *I, 57 const DFAStateInput (*SIT)[2], 58 const unsigned *SET): 59 InstrItins(I), CurrentState(0), DFAStateInputTable(SIT), 60 DFAStateEntryTable(SET) { 61 // Make sure DFA types are large enough for the number of terms & resources. 62 assert((DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) <= (8 * sizeof(DFAInput)) 63 && "(DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) too big for DFAInput"); 64 assert((DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) <= (8 * sizeof(DFAStateInput)) 65 && "(DFA_MAX_RESTERMS * DFA_MAX_RESOURCES) too big for DFAStateInput"); 66} 67 68 69// 70// ReadTable - Read the DFA transition table and update CachedTable. 71// 72// Format of the transition tables: 73// DFAStateInputTable[][2] = pairs of <Input, Transition> for all valid 74// transitions 75// DFAStateEntryTable[i] = Index of the first entry in DFAStateInputTable 76// for the ith state 77// 78void DFAPacketizer::ReadTable(unsigned int state) { 79 unsigned ThisState = DFAStateEntryTable[state]; 80 unsigned NextStateInTable = DFAStateEntryTable[state+1]; 81 // Early exit in case CachedTable has already contains this 82 // state's transitions. 83 if (CachedTable.count(UnsignPair(state, 84 DFAStateInputTable[ThisState][0]))) 85 return; 86 87 for (unsigned i = ThisState; i < NextStateInTable; i++) 88 CachedTable[UnsignPair(state, DFAStateInputTable[i][0])] = 89 DFAStateInputTable[i][1]; 90} 91 92// 93// getInsnInput - Return the DFAInput for an instruction class. 94// 95DFAInput DFAPacketizer::getInsnInput(unsigned InsnClass) { 96 // Note: this logic must match that in DFAPacketizerDefs.h for input vectors. 97 DFAInput InsnInput = 0; 98 unsigned i = 0; 99 for (const InstrStage *IS = InstrItins->beginStage(InsnClass), 100 *IE = InstrItins->endStage(InsnClass); IS != IE; ++IS, ++i) { 101 InsnInput = addDFAFuncUnits(InsnInput, IS->getUnits()); 102 assert ((i < DFA_MAX_RESTERMS) && "Exceeded maximum number of DFA inputs"); 103 } 104 return InsnInput; 105} 106 107// getInsnInput - Return the DFAInput for an instruction class input vector. 108DFAInput DFAPacketizer::getInsnInput(const std::vector<unsigned> &InsnClass) { 109 return getDFAInsnInput(InsnClass); 110} 111 112// canReserveResources - Check if the resources occupied by a MCInstrDesc 113// are available in the current state. 114bool DFAPacketizer::canReserveResources(const llvm::MCInstrDesc *MID) { 115 unsigned InsnClass = MID->getSchedClass(); 116 DFAInput InsnInput = getInsnInput(InsnClass); 117 UnsignPair StateTrans = UnsignPair(CurrentState, InsnInput); 118 ReadTable(CurrentState); 119 return (CachedTable.count(StateTrans) != 0); 120} 121 122// reserveResources - Reserve the resources occupied by a MCInstrDesc and 123// change the current state to reflect that change. 124void DFAPacketizer::reserveResources(const llvm::MCInstrDesc *MID) { 125 unsigned InsnClass = MID->getSchedClass(); 126 DFAInput InsnInput = getInsnInput(InsnClass); 127 UnsignPair StateTrans = UnsignPair(CurrentState, InsnInput); 128 ReadTable(CurrentState); 129 assert(CachedTable.count(StateTrans) != 0); 130 CurrentState = CachedTable[StateTrans]; 131} 132 133 134// canReserveResources - Check if the resources occupied by a machine 135// instruction are available in the current state. 136bool DFAPacketizer::canReserveResources(llvm::MachineInstr *MI) { 137 const llvm::MCInstrDesc &MID = MI->getDesc(); 138 return canReserveResources(&MID); 139} 140 141// reserveResources - Reserve the resources occupied by a machine 142// instruction and change the current state to reflect that change. 143void DFAPacketizer::reserveResources(llvm::MachineInstr *MI) { 144 const llvm::MCInstrDesc &MID = MI->getDesc(); 145 reserveResources(&MID); 146} 147 148namespace llvm { 149// DefaultVLIWScheduler - This class extends ScheduleDAGInstrs and overrides 150// Schedule method to build the dependence graph. 151class DefaultVLIWScheduler : public ScheduleDAGInstrs { 152private: 153 AliasAnalysis *AA; 154public: 155 DefaultVLIWScheduler(MachineFunction &MF, MachineLoopInfo &MLI, 156 AliasAnalysis *AA); 157 // Schedule - Actual scheduling work. 158 void schedule() override; 159}; 160} 161 162DefaultVLIWScheduler::DefaultVLIWScheduler(MachineFunction &MF, 163 MachineLoopInfo &MLI, 164 AliasAnalysis *AA) 165 : ScheduleDAGInstrs(MF, &MLI), AA(AA) { 166 CanHandleTerminators = true; 167} 168 169void DefaultVLIWScheduler::schedule() { 170 // Build the scheduling graph. 171 buildSchedGraph(AA); 172} 173 174// VLIWPacketizerList Ctor 175VLIWPacketizerList::VLIWPacketizerList(MachineFunction &MF, 176 MachineLoopInfo &MLI, AliasAnalysis *AA) 177 : MF(MF), AA(AA) { 178 TII = MF.getSubtarget().getInstrInfo(); 179 ResourceTracker = TII->CreateTargetScheduleState(MF.getSubtarget()); 180 VLIWScheduler = new DefaultVLIWScheduler(MF, MLI, AA); 181} 182 183// VLIWPacketizerList Dtor 184VLIWPacketizerList::~VLIWPacketizerList() { 185 if (VLIWScheduler) 186 delete VLIWScheduler; 187 188 if (ResourceTracker) 189 delete ResourceTracker; 190} 191 192// endPacket - End the current packet, bundle packet instructions and reset 193// DFA state. 194void VLIWPacketizerList::endPacket(MachineBasicBlock *MBB, 195 MachineInstr *MI) { 196 if (CurrentPacketMIs.size() > 1) { 197 MachineInstr *MIFirst = CurrentPacketMIs.front(); 198 finalizeBundle(*MBB, MIFirst->getIterator(), MI->getIterator()); 199 } 200 CurrentPacketMIs.clear(); 201 ResourceTracker->clearResources(); 202} 203 204// PacketizeMIs - Bundle machine instructions into packets. 205void VLIWPacketizerList::PacketizeMIs(MachineBasicBlock *MBB, 206 MachineBasicBlock::iterator BeginItr, 207 MachineBasicBlock::iterator EndItr) { 208 assert(VLIWScheduler && "VLIW Scheduler is not initialized!"); 209 VLIWScheduler->startBlock(MBB); 210 VLIWScheduler->enterRegion(MBB, BeginItr, EndItr, 211 std::distance(BeginItr, EndItr)); 212 VLIWScheduler->schedule(); 213 214 // Generate MI -> SU map. 215 MIToSUnit.clear(); 216 for (unsigned i = 0, e = VLIWScheduler->SUnits.size(); i != e; ++i) { 217 SUnit *SU = &VLIWScheduler->SUnits[i]; 218 MIToSUnit[SU->getInstr()] = SU; 219 } 220 221 // The main packetizer loop. 222 for (; BeginItr != EndItr; ++BeginItr) { 223 MachineInstr *MI = BeginItr; 224 225 this->initPacketizerState(); 226 227 // End the current packet if needed. 228 if (this->isSoloInstruction(MI)) { 229 endPacket(MBB, MI); 230 continue; 231 } 232 233 // Ignore pseudo instructions. 234 if (this->ignorePseudoInstruction(MI, MBB)) 235 continue; 236 237 SUnit *SUI = MIToSUnit[MI]; 238 assert(SUI && "Missing SUnit Info!"); 239 240 // Ask DFA if machine resource is available for MI. 241 bool ResourceAvail = ResourceTracker->canReserveResources(MI); 242 if (ResourceAvail && shouldAddToPacket(MI)) { 243 // Dependency check for MI with instructions in CurrentPacketMIs. 244 for (std::vector<MachineInstr*>::iterator VI = CurrentPacketMIs.begin(), 245 VE = CurrentPacketMIs.end(); VI != VE; ++VI) { 246 MachineInstr *MJ = *VI; 247 SUnit *SUJ = MIToSUnit[MJ]; 248 assert(SUJ && "Missing SUnit Info!"); 249 250 // Is it legal to packetize SUI and SUJ together. 251 if (!this->isLegalToPacketizeTogether(SUI, SUJ)) { 252 // Allow packetization if dependency can be pruned. 253 if (!this->isLegalToPruneDependencies(SUI, SUJ)) { 254 // End the packet if dependency cannot be pruned. 255 endPacket(MBB, MI); 256 break; 257 } // !isLegalToPruneDependencies. 258 } // !isLegalToPacketizeTogether. 259 } // For all instructions in CurrentPacketMIs. 260 } else { 261 // End the packet if resource is not available, or if the instruction 262 // shoud not be added to the current packet. 263 endPacket(MBB, MI); 264 } 265 266 // Add MI to the current packet. 267 BeginItr = this->addToPacket(MI); 268 } // For all instructions in BB. 269 270 // End any packet left behind. 271 endPacket(MBB, EndItr); 272 VLIWScheduler->exitRegion(); 273 VLIWScheduler->finishBlock(); 274} 275