1 //===-- HexagonHazardRecognizer.cpp - Hexagon Post RA Hazard Recognizer ---===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines the hazard recognizer for scheduling on Hexagon. 10 // Use a DFA based hazard recognizer. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "HexagonHazardRecognizer.h" 15 #include "llvm/CodeGen/MachineFunction.h" 16 #include "llvm/CodeGen/MachineInstr.h" 17 #include "llvm/CodeGen/MachineOperand.h" 18 #include "llvm/CodeGen/ScheduleDAG.h" 19 #include "llvm/Support/Debug.h" 20 #include "llvm/Support/raw_ostream.h" 21 #include <cassert> 22 23 using namespace llvm; 24 25 #define DEBUG_TYPE "post-RA-sched" 26 27 void HexagonHazardRecognizer::Reset() { 28 LLVM_DEBUG(dbgs() << "Reset hazard recognizer\n"); 29 Resources->clearResources(); 30 PacketNum = 0; 31 UsesDotCur = nullptr; 32 DotCurPNum = -1; 33 UsesLoad = false; 34 PrefVectorStoreNew = nullptr; 35 RegDefs.clear(); 36 } 37 38 ScheduleHazardRecognizer::HazardType 39 HexagonHazardRecognizer::getHazardType(SUnit *SU, int stalls) { 40 MachineInstr *MI = SU->getInstr(); 41 if (!MI || TII->isZeroCost(MI->getOpcode())) 42 return NoHazard; 43 44 if (!Resources->canReserveResources(*MI)) { 45 LLVM_DEBUG(dbgs() << "*** Hazard in cycle " << PacketNum << ", " << *MI); 46 HazardType RetVal = Hazard; 47 if (isNewStore(*MI)) { 48 // The .new store version uses different resources so check if it 49 // causes a hazard. 50 MachineFunction *MF = MI->getParent()->getParent(); 51 MachineInstr *NewMI = 52 MF->CreateMachineInstr(TII->get(TII->getDotNewOp(*MI)), 53 MI->getDebugLoc()); 54 if (Resources->canReserveResources(*NewMI)) 55 RetVal = NoHazard; 56 LLVM_DEBUG(dbgs() << "*** Try .new version? " << (RetVal == NoHazard) 57 << "\n"); 58 MF->deleteMachineInstr(NewMI); 59 } 60 return RetVal; 61 } 62 63 if (SU == UsesDotCur && DotCurPNum != (int)PacketNum) { 64 LLVM_DEBUG(dbgs() << "*** .cur Hazard in cycle " << PacketNum << ", " 65 << *MI); 66 return Hazard; 67 } 68 69 return NoHazard; 70 } 71 72 void HexagonHazardRecognizer::AdvanceCycle() { 73 LLVM_DEBUG(dbgs() << "Advance cycle, clear state\n"); 74 Resources->clearResources(); 75 if (DotCurPNum != -1 && DotCurPNum != (int)PacketNum) { 76 UsesDotCur = nullptr; 77 DotCurPNum = -1; 78 } 79 UsesLoad = false; 80 PrefVectorStoreNew = nullptr; 81 PacketNum++; 82 RegDefs.clear(); 83 } 84 85 /// Handle the cases when we prefer one instruction over another. Case 1 - we 86 /// prefer not to generate multiple loads in the packet to avoid a potential 87 /// bank conflict. Case 2 - if a packet contains a dot cur instruction, then we 88 /// prefer the instruction that can use the dot cur result. However, if the use 89 /// is not scheduled in the same packet, then prefer other instructions in the 90 /// subsequent packet. Case 3 - we prefer a vector store that can be converted 91 /// to a .new store. The packetizer will not generate the .new store if the 92 /// store doesn't have resources to fit in the packet (but the .new store may 93 /// have resources). We attempt to schedule the store as soon as possible to 94 /// help packetize the two instructions together. 95 bool HexagonHazardRecognizer::ShouldPreferAnother(SUnit *SU) { 96 if (PrefVectorStoreNew != nullptr && PrefVectorStoreNew != SU) 97 return true; 98 if (UsesLoad && SU->isInstr() && SU->getInstr()->mayLoad()) 99 return true; 100 return UsesDotCur && ((SU == UsesDotCur) ^ (DotCurPNum == (int)PacketNum)); 101 } 102 103 /// Return true if the instruction would be converted to a new value store when 104 /// packetized. 105 bool HexagonHazardRecognizer::isNewStore(MachineInstr &MI) { 106 if (!TII->mayBeNewStore(MI)) 107 return false; 108 MachineOperand &MO = MI.getOperand(MI.getNumOperands() - 1); 109 return MO.isReg() && RegDefs.contains(MO.getReg()); 110 } 111 112 void HexagonHazardRecognizer::EmitInstruction(SUnit *SU) { 113 MachineInstr *MI = SU->getInstr(); 114 if (!MI) 115 return; 116 117 // Keep the set of definitions for each packet, which is used to determine 118 // if a .new can be used. 119 for (const MachineOperand &MO : MI->operands()) 120 if (MO.isReg() && MO.isDef() && !MO.isImplicit()) 121 RegDefs.insert(MO.getReg()); 122 123 if (TII->isZeroCost(MI->getOpcode())) 124 return; 125 126 if (!Resources->canReserveResources(*MI) || isNewStore(*MI)) { 127 // It must be a .new store since other instructions must be able to be 128 // reserved at this point. 129 assert(TII->mayBeNewStore(*MI) && "Expecting .new store"); 130 MachineFunction *MF = MI->getParent()->getParent(); 131 MachineInstr *NewMI = 132 MF->CreateMachineInstr(TII->get(TII->getDotNewOp(*MI)), 133 MI->getDebugLoc()); 134 if (Resources->canReserveResources(*NewMI)) 135 Resources->reserveResources(*NewMI); 136 else 137 Resources->reserveResources(*MI); 138 MF->deleteMachineInstr(NewMI); 139 } else 140 Resources->reserveResources(*MI); 141 LLVM_DEBUG(dbgs() << " Add instruction " << *MI); 142 143 // When scheduling a dot cur instruction, check if there is an instruction 144 // that can use the dot cur in the same packet. If so, we'll attempt to 145 // schedule it before other instructions. We only do this if the load has a 146 // single zero-latency use. 147 if (TII->mayBeCurLoad(*MI)) 148 for (auto &S : SU->Succs) 149 if (S.isAssignedRegDep() && S.getLatency() == 0 && 150 S.getSUnit()->NumPredsLeft == 1) { 151 UsesDotCur = S.getSUnit(); 152 DotCurPNum = PacketNum; 153 break; 154 } 155 if (SU == UsesDotCur) { 156 UsesDotCur = nullptr; 157 DotCurPNum = -1; 158 } 159 160 UsesLoad = MI->mayLoad(); 161 162 if (TII->isHVXVec(*MI) && !MI->mayLoad() && !MI->mayStore()) 163 for (auto &S : SU->Succs) 164 if (S.isAssignedRegDep() && S.getLatency() == 0 && 165 TII->mayBeNewStore(*S.getSUnit()->getInstr()) && 166 Resources->canReserveResources(*S.getSUnit()->getInstr())) { 167 PrefVectorStoreNew = S.getSUnit(); 168 break; 169 } 170 } 171