1 //===- SIInsertHardClauses.cpp - Insert Hard Clauses ----------------------===// 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 /// \file 10 /// Insert s_clause instructions to form hard clauses. 11 /// 12 /// Clausing load instructions can give cache coherency benefits. Before gfx10, 13 /// the hardware automatically detected "soft clauses", which were sequences of 14 /// memory instructions of the same type. In gfx10 this detection was removed, 15 /// and the s_clause instruction was introduced to explicitly mark "hard 16 /// clauses". 17 /// 18 /// It's the scheduler's job to form the clauses by putting similar memory 19 /// instructions next to each other. Our job is just to insert an s_clause 20 /// instruction to mark the start of each clause. 21 /// 22 /// Note that hard clauses are very similar to, but logically distinct from, the 23 /// groups of instructions that have to be restartable when XNACK is enabled. 24 /// The rules are slightly different in each case. For example an s_nop 25 /// instruction breaks a restartable group, but can appear in the middle of a 26 /// hard clause. (Before gfx10 there wasn't a distinction, and both were called 27 /// "soft clauses" or just "clauses".) 28 /// 29 /// The SIFormMemoryClauses pass and GCNHazardRecognizer deal with restartable 30 /// groups, not hard clauses. 31 // 32 //===----------------------------------------------------------------------===// 33 34 #include "AMDGPU.h" 35 #include "GCNSubtarget.h" 36 #include "MCTargetDesc/AMDGPUMCTargetDesc.h" 37 #include "llvm/ADT/SmallVector.h" 38 #include "llvm/CodeGen/MachineFunctionPass.h" 39 40 using namespace llvm; 41 42 #define DEBUG_TYPE "si-insert-hard-clauses" 43 44 namespace { 45 46 enum HardClauseType { 47 // For GFX10: 48 49 // Texture, buffer, global or scratch memory instructions. 50 HARDCLAUSE_VMEM, 51 // Flat (not global or scratch) memory instructions. 52 HARDCLAUSE_FLAT, 53 54 // For GFX11: 55 56 // Texture memory instructions. 57 HARDCLAUSE_MIMG_LOAD, 58 HARDCLAUSE_MIMG_STORE, 59 HARDCLAUSE_MIMG_ATOMIC, 60 HARDCLAUSE_MIMG_SAMPLE, 61 // Buffer, global or scratch memory instructions. 62 HARDCLAUSE_VMEM_LOAD, 63 HARDCLAUSE_VMEM_STORE, 64 HARDCLAUSE_VMEM_ATOMIC, 65 // Flat (not global or scratch) memory instructions. 66 HARDCLAUSE_FLAT_LOAD, 67 HARDCLAUSE_FLAT_STORE, 68 HARDCLAUSE_FLAT_ATOMIC, 69 // BVH instructions. 70 HARDCLAUSE_BVH, 71 72 // Common: 73 74 // Instructions that access LDS. 75 HARDCLAUSE_LDS, 76 // Scalar memory instructions. 77 HARDCLAUSE_SMEM, 78 // VALU instructions. 79 HARDCLAUSE_VALU, 80 LAST_REAL_HARDCLAUSE_TYPE = HARDCLAUSE_VALU, 81 82 // Internal instructions, which are allowed in the middle of a hard clause, 83 // except for s_waitcnt. 84 HARDCLAUSE_INTERNAL, 85 // Meta instructions that do not result in any ISA like KILL. 86 HARDCLAUSE_IGNORE, 87 // Instructions that are not allowed in a hard clause: SALU, export, branch, 88 // message, GDS, s_waitcnt and anything else not mentioned above. 89 HARDCLAUSE_ILLEGAL, 90 }; 91 92 class SIInsertHardClauses : public MachineFunctionPass { 93 public: 94 static char ID; 95 const GCNSubtarget *ST = nullptr; 96 SIInsertHardClauses()97 SIInsertHardClauses() : MachineFunctionPass(ID) {} 98 getAnalysisUsage(AnalysisUsage & AU) const99 void getAnalysisUsage(AnalysisUsage &AU) const override { 100 AU.setPreservesCFG(); 101 MachineFunctionPass::getAnalysisUsage(AU); 102 } 103 getHardClauseType(const MachineInstr & MI)104 HardClauseType getHardClauseType(const MachineInstr &MI) { 105 if (MI.mayLoad() || (MI.mayStore() && ST->shouldClusterStores())) { 106 if (ST->getGeneration() == AMDGPUSubtarget::GFX10) { 107 if (SIInstrInfo::isVMEM(MI) || SIInstrInfo::isSegmentSpecificFLAT(MI)) { 108 if (ST->hasNSAClauseBug()) { 109 const AMDGPU::MIMGInfo *Info = AMDGPU::getMIMGInfo(MI.getOpcode()); 110 if (Info && Info->MIMGEncoding == AMDGPU::MIMGEncGfx10NSA) 111 return HARDCLAUSE_ILLEGAL; 112 } 113 return HARDCLAUSE_VMEM; 114 } 115 if (SIInstrInfo::isFLAT(MI)) 116 return HARDCLAUSE_FLAT; 117 } else { 118 assert(ST->getGeneration() >= AMDGPUSubtarget::GFX11); 119 if (SIInstrInfo::isMIMG(MI)) { 120 const AMDGPU::MIMGInfo *Info = AMDGPU::getMIMGInfo(MI.getOpcode()); 121 const AMDGPU::MIMGBaseOpcodeInfo *BaseInfo = 122 AMDGPU::getMIMGBaseOpcodeInfo(Info->BaseOpcode); 123 if (BaseInfo->BVH) 124 return HARDCLAUSE_BVH; 125 if (BaseInfo->Sampler) 126 return HARDCLAUSE_MIMG_SAMPLE; 127 return MI.mayLoad() ? MI.mayStore() ? HARDCLAUSE_MIMG_ATOMIC 128 : HARDCLAUSE_MIMG_LOAD 129 : HARDCLAUSE_MIMG_STORE; 130 } 131 if (SIInstrInfo::isVMEM(MI) || SIInstrInfo::isSegmentSpecificFLAT(MI)) { 132 return MI.mayLoad() ? MI.mayStore() ? HARDCLAUSE_VMEM_ATOMIC 133 : HARDCLAUSE_VMEM_LOAD 134 : HARDCLAUSE_VMEM_STORE; 135 } 136 if (SIInstrInfo::isFLAT(MI)) { 137 return MI.mayLoad() ? MI.mayStore() ? HARDCLAUSE_FLAT_ATOMIC 138 : HARDCLAUSE_FLAT_LOAD 139 : HARDCLAUSE_FLAT_STORE; 140 } 141 } 142 // TODO: LDS 143 if (SIInstrInfo::isSMRD(MI)) 144 return HARDCLAUSE_SMEM; 145 } 146 147 // Don't form VALU clauses. It's not clear what benefit they give, if any. 148 149 // In practice s_nop is the only internal instruction we're likely to see. 150 // It's safe to treat the rest as illegal. 151 if (MI.getOpcode() == AMDGPU::S_NOP) 152 return HARDCLAUSE_INTERNAL; 153 if (MI.isMetaInstruction()) 154 return HARDCLAUSE_IGNORE; 155 return HARDCLAUSE_ILLEGAL; 156 } 157 158 // Track information about a clause as we discover it. 159 struct ClauseInfo { 160 // The type of all (non-internal) instructions in the clause. 161 HardClauseType Type = HARDCLAUSE_ILLEGAL; 162 // The first (necessarily non-internal) instruction in the clause. 163 MachineInstr *First = nullptr; 164 // The last non-internal instruction in the clause. 165 MachineInstr *Last = nullptr; 166 // The length of the clause including any internal instructions in the 167 // middle (but not at the end) of the clause. 168 unsigned Length = 0; 169 // Internal instructions at the and of a clause should not be included in 170 // the clause. Count them in TrailingInternalLength until a new memory 171 // instruction is added. 172 unsigned TrailingInternalLength = 0; 173 // The base operands of *Last. 174 SmallVector<const MachineOperand *, 4> BaseOps; 175 }; 176 emitClause(const ClauseInfo & CI,const SIInstrInfo * SII)177 bool emitClause(const ClauseInfo &CI, const SIInstrInfo *SII) { 178 if (CI.First == CI.Last) 179 return false; 180 assert(CI.Length <= ST->maxHardClauseLength() && 181 "Hard clause is too long!"); 182 183 auto &MBB = *CI.First->getParent(); 184 auto ClauseMI = 185 BuildMI(MBB, *CI.First, DebugLoc(), SII->get(AMDGPU::S_CLAUSE)) 186 .addImm(CI.Length - 1); 187 finalizeBundle(MBB, ClauseMI->getIterator(), 188 std::next(CI.Last->getIterator())); 189 return true; 190 } 191 runOnMachineFunction(MachineFunction & MF)192 bool runOnMachineFunction(MachineFunction &MF) override { 193 if (skipFunction(MF.getFunction())) 194 return false; 195 196 ST = &MF.getSubtarget<GCNSubtarget>(); 197 if (!ST->hasHardClauses()) 198 return false; 199 200 const SIInstrInfo *SII = ST->getInstrInfo(); 201 const TargetRegisterInfo *TRI = ST->getRegisterInfo(); 202 203 bool Changed = false; 204 for (auto &MBB : MF) { 205 ClauseInfo CI; 206 for (auto &MI : MBB) { 207 HardClauseType Type = getHardClauseType(MI); 208 209 int64_t Dummy1; 210 bool Dummy2; 211 LocationSize Dummy3 = 0; 212 SmallVector<const MachineOperand *, 4> BaseOps; 213 if (Type <= LAST_REAL_HARDCLAUSE_TYPE) { 214 if (!SII->getMemOperandsWithOffsetWidth(MI, BaseOps, Dummy1, Dummy2, 215 Dummy3, TRI)) { 216 // We failed to get the base operands, so we'll never clause this 217 // instruction with any other, so pretend it's illegal. 218 Type = HARDCLAUSE_ILLEGAL; 219 } 220 } 221 222 if (CI.Length == ST->maxHardClauseLength() || 223 (CI.Length && Type != HARDCLAUSE_INTERNAL && 224 Type != HARDCLAUSE_IGNORE && 225 (Type != CI.Type || 226 // Note that we lie to shouldClusterMemOps about the size of the 227 // cluster. When shouldClusterMemOps is called from the machine 228 // scheduler it limits the size of the cluster to avoid increasing 229 // register pressure too much, but this pass runs after register 230 // allocation so there is no need for that kind of limit. 231 // We also lie about the Offset and OffsetIsScalable parameters, 232 // as they aren't used in the SIInstrInfo implementation. 233 !SII->shouldClusterMemOps(CI.BaseOps, 0, false, BaseOps, 0, false, 234 2, 2)))) { 235 // Finish the current clause. 236 Changed |= emitClause(CI, SII); 237 CI = ClauseInfo(); 238 } 239 240 if (CI.Length) { 241 // Extend the current clause. 242 if (Type != HARDCLAUSE_IGNORE) { 243 if (Type == HARDCLAUSE_INTERNAL) { 244 ++CI.TrailingInternalLength; 245 } else { 246 ++CI.Length; 247 CI.Length += CI.TrailingInternalLength; 248 CI.TrailingInternalLength = 0; 249 CI.Last = &MI; 250 CI.BaseOps = std::move(BaseOps); 251 } 252 } 253 } else if (Type <= LAST_REAL_HARDCLAUSE_TYPE) { 254 // Start a new clause. 255 CI = ClauseInfo{Type, &MI, &MI, 1, 0, std::move(BaseOps)}; 256 } 257 } 258 259 // Finish the last clause in the basic block if any. 260 if (CI.Length) 261 Changed |= emitClause(CI, SII); 262 } 263 264 return Changed; 265 } 266 }; 267 268 } // namespace 269 270 char SIInsertHardClauses::ID = 0; 271 272 char &llvm::SIInsertHardClausesID = SIInsertHardClauses::ID; 273 274 INITIALIZE_PASS(SIInsertHardClauses, DEBUG_TYPE, "SI Insert Hard Clauses", 275 false, false) 276