1 //===-- AArch64Subtarget.cpp - AArch64 Subtarget Information ----*- C++ -*-===// 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 implements the AArch64 specific subclass of TargetSubtarget. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "AArch64Subtarget.h" 14 15 #include "AArch64.h" 16 #include "AArch64CallLowering.h" 17 #include "AArch64InstrInfo.h" 18 #include "AArch64LegalizerInfo.h" 19 #include "AArch64PBQPRegAlloc.h" 20 #include "AArch64RegisterBankInfo.h" 21 #include "AArch64TargetMachine.h" 22 #include "MCTargetDesc/AArch64AddressingModes.h" 23 #include "llvm/CodeGen/GlobalISel/InstructionSelect.h" 24 #include "llvm/CodeGen/MachineScheduler.h" 25 #include "llvm/IR/GlobalValue.h" 26 #include "llvm/Support/TargetParser.h" 27 28 using namespace llvm; 29 30 #define DEBUG_TYPE "aarch64-subtarget" 31 32 #define GET_SUBTARGETINFO_CTOR 33 #define GET_SUBTARGETINFO_TARGET_DESC 34 #include "AArch64GenSubtargetInfo.inc" 35 36 static cl::opt<bool> 37 EnableEarlyIfConvert("aarch64-early-ifcvt", cl::desc("Enable the early if " 38 "converter pass"), cl::init(true), cl::Hidden); 39 40 // If OS supports TBI, use this flag to enable it. 41 static cl::opt<bool> 42 UseAddressTopByteIgnored("aarch64-use-tbi", cl::desc("Assume that top byte of " 43 "an address is ignored"), cl::init(false), cl::Hidden); 44 45 static cl::opt<bool> 46 UseNonLazyBind("aarch64-enable-nonlazybind", 47 cl::desc("Call nonlazybind functions via direct GOT load"), 48 cl::init(false), cl::Hidden); 49 50 AArch64Subtarget & 51 AArch64Subtarget::initializeSubtargetDependencies(StringRef FS, 52 StringRef CPUString) { 53 // Determine default and user-specified characteristics 54 55 if (CPUString.empty()) 56 CPUString = "generic"; 57 58 ParseSubtargetFeatures(CPUString, FS); 59 initializeProperties(); 60 61 return *this; 62 } 63 64 void AArch64Subtarget::initializeProperties() { 65 // Initialize CPU specific properties. We should add a tablegen feature for 66 // this in the future so we can specify it together with the subtarget 67 // features. 68 switch (ARMProcFamily) { 69 case Others: 70 break; 71 case CortexA35: 72 break; 73 case CortexA53: 74 PrefFunctionLogAlignment = 3; 75 break; 76 case CortexA55: 77 break; 78 case CortexA57: 79 MaxInterleaveFactor = 4; 80 PrefFunctionLogAlignment = 4; 81 break; 82 case CortexA65: 83 PrefFunctionLogAlignment = 3; 84 break; 85 case CortexA72: 86 case CortexA73: 87 case CortexA75: 88 case CortexA76: 89 PrefFunctionLogAlignment = 4; 90 break; 91 case AppleA7: 92 case AppleA10: 93 case AppleA11: 94 case AppleA12: 95 case AppleA13: 96 CacheLineSize = 64; 97 PrefetchDistance = 280; 98 MinPrefetchStride = 2048; 99 MaxPrefetchIterationsAhead = 3; 100 break; 101 case ExynosM3: 102 MaxInterleaveFactor = 4; 103 MaxJumpTableSize = 20; 104 PrefFunctionLogAlignment = 5; 105 PrefLoopLogAlignment = 4; 106 break; 107 case Falkor: 108 MaxInterleaveFactor = 4; 109 // FIXME: remove this to enable 64-bit SLP if performance looks good. 110 MinVectorRegisterBitWidth = 128; 111 CacheLineSize = 128; 112 PrefetchDistance = 820; 113 MinPrefetchStride = 2048; 114 MaxPrefetchIterationsAhead = 8; 115 break; 116 case Kryo: 117 MaxInterleaveFactor = 4; 118 VectorInsertExtractBaseCost = 2; 119 CacheLineSize = 128; 120 PrefetchDistance = 740; 121 MinPrefetchStride = 1024; 122 MaxPrefetchIterationsAhead = 11; 123 // FIXME: remove this to enable 64-bit SLP if performance looks good. 124 MinVectorRegisterBitWidth = 128; 125 break; 126 case NeoverseE1: 127 PrefFunctionLogAlignment = 3; 128 break; 129 case NeoverseN1: 130 PrefFunctionLogAlignment = 4; 131 break; 132 case Saphira: 133 MaxInterleaveFactor = 4; 134 // FIXME: remove this to enable 64-bit SLP if performance looks good. 135 MinVectorRegisterBitWidth = 128; 136 break; 137 case ThunderX2T99: 138 CacheLineSize = 64; 139 PrefFunctionLogAlignment = 3; 140 PrefLoopLogAlignment = 2; 141 MaxInterleaveFactor = 4; 142 PrefetchDistance = 128; 143 MinPrefetchStride = 1024; 144 MaxPrefetchIterationsAhead = 4; 145 // FIXME: remove this to enable 64-bit SLP if performance looks good. 146 MinVectorRegisterBitWidth = 128; 147 break; 148 case ThunderX: 149 case ThunderXT88: 150 case ThunderXT81: 151 case ThunderXT83: 152 CacheLineSize = 128; 153 PrefFunctionLogAlignment = 3; 154 PrefLoopLogAlignment = 2; 155 // FIXME: remove this to enable 64-bit SLP if performance looks good. 156 MinVectorRegisterBitWidth = 128; 157 break; 158 case TSV110: 159 CacheLineSize = 64; 160 PrefFunctionLogAlignment = 4; 161 PrefLoopLogAlignment = 2; 162 break; 163 case ThunderX3T110: 164 CacheLineSize = 64; 165 PrefFunctionLogAlignment = 4; 166 PrefLoopLogAlignment = 2; 167 MaxInterleaveFactor = 4; 168 PrefetchDistance = 128; 169 MinPrefetchStride = 1024; 170 MaxPrefetchIterationsAhead = 4; 171 // FIXME: remove this to enable 64-bit SLP if performance looks good. 172 MinVectorRegisterBitWidth = 128; 173 break; 174 } 175 } 176 177 AArch64Subtarget::AArch64Subtarget(const Triple &TT, const std::string &CPU, 178 const std::string &FS, 179 const TargetMachine &TM, bool LittleEndian) 180 : AArch64GenSubtargetInfo(TT, CPU, FS), 181 ReserveXRegister(AArch64::GPR64commonRegClass.getNumRegs()), 182 CustomCallSavedXRegs(AArch64::GPR64commonRegClass.getNumRegs()), 183 IsLittle(LittleEndian), 184 TargetTriple(TT), FrameLowering(), 185 InstrInfo(initializeSubtargetDependencies(FS, CPU)), TSInfo(), 186 TLInfo(TM, *this) { 187 if (AArch64::isX18ReservedByDefault(TT)) 188 ReserveXRegister.set(18); 189 190 CallLoweringInfo.reset(new AArch64CallLowering(*getTargetLowering())); 191 Legalizer.reset(new AArch64LegalizerInfo(*this)); 192 193 auto *RBI = new AArch64RegisterBankInfo(*getRegisterInfo()); 194 195 // FIXME: At this point, we can't rely on Subtarget having RBI. 196 // It's awkward to mix passing RBI and the Subtarget; should we pass 197 // TII/TRI as well? 198 InstSelector.reset(createAArch64InstructionSelector( 199 *static_cast<const AArch64TargetMachine *>(&TM), *this, *RBI)); 200 201 RegBankInfo.reset(RBI); 202 } 203 204 const CallLowering *AArch64Subtarget::getCallLowering() const { 205 return CallLoweringInfo.get(); 206 } 207 208 InstructionSelector *AArch64Subtarget::getInstructionSelector() const { 209 return InstSelector.get(); 210 } 211 212 const LegalizerInfo *AArch64Subtarget::getLegalizerInfo() const { 213 return Legalizer.get(); 214 } 215 216 const RegisterBankInfo *AArch64Subtarget::getRegBankInfo() const { 217 return RegBankInfo.get(); 218 } 219 220 /// Find the target operand flags that describe how a global value should be 221 /// referenced for the current subtarget. 222 unsigned 223 AArch64Subtarget::ClassifyGlobalReference(const GlobalValue *GV, 224 const TargetMachine &TM) const { 225 // MachO large model always goes via a GOT, simply to get a single 8-byte 226 // absolute relocation on all global addresses. 227 if (TM.getCodeModel() == CodeModel::Large && isTargetMachO()) 228 return AArch64II::MO_GOT; 229 230 if (!TM.shouldAssumeDSOLocal(*GV->getParent(), GV)) { 231 if (GV->hasDLLImportStorageClass()) 232 return AArch64II::MO_GOT | AArch64II::MO_DLLIMPORT; 233 if (getTargetTriple().isOSWindows()) 234 return AArch64II::MO_GOT | AArch64II::MO_COFFSTUB; 235 return AArch64II::MO_GOT; 236 } 237 238 // The small code model's direct accesses use ADRP, which cannot 239 // necessarily produce the value 0 (if the code is above 4GB). 240 // Same for the tiny code model, where we have a pc relative LDR. 241 if ((useSmallAddressing() || TM.getCodeModel() == CodeModel::Tiny) && 242 GV->hasExternalWeakLinkage()) 243 return AArch64II::MO_GOT; 244 245 // References to tagged globals are marked with MO_NC | MO_TAGGED to indicate 246 // that their nominal addresses are tagged and outside of the code model. In 247 // AArch64ExpandPseudo::expandMI we emit an additional instruction to set the 248 // tag if necessary based on MO_TAGGED. 249 if (AllowTaggedGlobals && !isa<FunctionType>(GV->getValueType())) 250 return AArch64II::MO_NC | AArch64II::MO_TAGGED; 251 252 return AArch64II::MO_NO_FLAG; 253 } 254 255 unsigned AArch64Subtarget::classifyGlobalFunctionReference( 256 const GlobalValue *GV, const TargetMachine &TM) const { 257 // MachO large model always goes via a GOT, because we don't have the 258 // relocations available to do anything else.. 259 if (TM.getCodeModel() == CodeModel::Large && isTargetMachO() && 260 !GV->hasInternalLinkage()) 261 return AArch64II::MO_GOT; 262 263 // NonLazyBind goes via GOT unless we know it's available locally. 264 auto *F = dyn_cast<Function>(GV); 265 if (UseNonLazyBind && F && F->hasFnAttribute(Attribute::NonLazyBind) && 266 !TM.shouldAssumeDSOLocal(*GV->getParent(), GV)) 267 return AArch64II::MO_GOT; 268 269 // Use ClassifyGlobalReference for setting MO_DLLIMPORT/MO_COFFSTUB. 270 if (getTargetTriple().isOSWindows()) 271 return ClassifyGlobalReference(GV, TM); 272 273 return AArch64II::MO_NO_FLAG; 274 } 275 276 void AArch64Subtarget::overrideSchedPolicy(MachineSchedPolicy &Policy, 277 unsigned NumRegionInstrs) const { 278 // LNT run (at least on Cyclone) showed reasonably significant gains for 279 // bi-directional scheduling. 253.perlbmk. 280 Policy.OnlyTopDown = false; 281 Policy.OnlyBottomUp = false; 282 // Enabling or Disabling the latency heuristic is a close call: It seems to 283 // help nearly no benchmark on out-of-order architectures, on the other hand 284 // it regresses register pressure on a few benchmarking. 285 Policy.DisableLatencyHeuristic = DisableLatencySchedHeuristic; 286 } 287 288 bool AArch64Subtarget::enableEarlyIfConversion() const { 289 return EnableEarlyIfConvert; 290 } 291 292 bool AArch64Subtarget::supportsAddressTopByteIgnored() const { 293 if (!UseAddressTopByteIgnored) 294 return false; 295 296 if (TargetTriple.isiOS()) { 297 unsigned Major, Minor, Micro; 298 TargetTriple.getiOSVersion(Major, Minor, Micro); 299 return Major >= 8; 300 } 301 302 return false; 303 } 304 305 std::unique_ptr<PBQPRAConstraint> 306 AArch64Subtarget::getCustomPBQPConstraints() const { 307 return balanceFPOps() ? std::make_unique<A57ChainingConstraint>() : nullptr; 308 } 309 310 void AArch64Subtarget::mirFileLoaded(MachineFunction &MF) const { 311 // We usually compute max call frame size after ISel. Do the computation now 312 // if the .mir file didn't specify it. Note that this will probably give you 313 // bogus values after PEI has eliminated the callframe setup/destroy pseudo 314 // instructions, specify explicitly if you need it to be correct. 315 MachineFrameInfo &MFI = MF.getFrameInfo(); 316 if (!MFI.isMaxCallFrameSizeComputed()) 317 MFI.computeMaxCallFrameSize(MF); 318 } 319