1 //===-- TargetMachine.cpp - General Target Information ---------------------==// 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 describes the general parts of a Target machine. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/Target/TargetMachine.h" 14 #include "llvm/Analysis/TargetTransformInfo.h" 15 #include "llvm/IR/Function.h" 16 #include "llvm/IR/GlobalAlias.h" 17 #include "llvm/IR/GlobalValue.h" 18 #include "llvm/IR/GlobalVariable.h" 19 #include "llvm/IR/LegacyPassManager.h" 20 #include "llvm/IR/Mangler.h" 21 #include "llvm/MC/MCAsmInfo.h" 22 #include "llvm/MC/MCContext.h" 23 #include "llvm/MC/MCInstrInfo.h" 24 #include "llvm/MC/MCSectionMachO.h" 25 #include "llvm/MC/MCTargetOptions.h" 26 #include "llvm/MC/SectionKind.h" 27 #include "llvm/Target/TargetLoweringObjectFile.h" 28 using namespace llvm; 29 30 //--------------------------------------------------------------------------- 31 // TargetMachine Class 32 // 33 34 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString, 35 const Triple &TT, StringRef CPU, StringRef FS, 36 const TargetOptions &Options) 37 : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), 38 TargetCPU(std::string(CPU)), TargetFS(std::string(FS)), AsmInfo(nullptr), 39 MRI(nullptr), MII(nullptr), STI(nullptr), RequireStructuredCFG(false), 40 O0WantsFastISel(false), DefaultOptions(Options), Options(Options) {} 41 42 TargetMachine::~TargetMachine() = default; 43 44 bool TargetMachine::isPositionIndependent() const { 45 return getRelocationModel() == Reloc::PIC_; 46 } 47 48 /// Reset the target options based on the function's attributes. 49 /// setFunctionAttributes should have made the raw attribute value consistent 50 /// with the command line flag if used. 51 // 52 // FIXME: This function needs to go away for a number of reasons: 53 // a) global state on the TargetMachine is terrible in general, 54 // b) these target options should be passed only on the function 55 // and not on the TargetMachine (via TargetOptions) at all. 56 void TargetMachine::resetTargetOptions(const Function &F) const { 57 #define RESET_OPTION(X, Y) \ 58 do { \ 59 Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \ 60 } while (0) 61 62 RESET_OPTION(UnsafeFPMath, "unsafe-fp-math"); 63 RESET_OPTION(NoInfsFPMath, "no-infs-fp-math"); 64 RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math"); 65 RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math"); 66 } 67 68 /// Returns the code generation relocation model. The choices are static, PIC, 69 /// and dynamic-no-pic. 70 Reloc::Model TargetMachine::getRelocationModel() const { return RM; } 71 72 /// Returns the code model. The choices are small, kernel, medium, large, and 73 /// target default. 74 CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; } 75 76 /// Get the IR-specified TLS model for Var. 77 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) { 78 switch (GV->getThreadLocalMode()) { 79 case GlobalVariable::NotThreadLocal: 80 llvm_unreachable("getSelectedTLSModel for non-TLS variable"); 81 break; 82 case GlobalVariable::GeneralDynamicTLSModel: 83 return TLSModel::GeneralDynamic; 84 case GlobalVariable::LocalDynamicTLSModel: 85 return TLSModel::LocalDynamic; 86 case GlobalVariable::InitialExecTLSModel: 87 return TLSModel::InitialExec; 88 case GlobalVariable::LocalExecTLSModel: 89 return TLSModel::LocalExec; 90 } 91 llvm_unreachable("invalid TLS model"); 92 } 93 94 bool TargetMachine::shouldAssumeDSOLocal(const Module &M, 95 const GlobalValue *GV) const { 96 const Triple &TT = getTargetTriple(); 97 Reloc::Model RM = getRelocationModel(); 98 99 // According to the llvm language reference, we should be able to 100 // just return false in here if we have a GV, as we know it is 101 // dso_preemptable. At this point in time, the various IR producers 102 // have not been transitioned to always produce a dso_local when it 103 // is possible to do so. 104 // In the case of ExternalSymbolSDNode, GV is null and we should just return 105 // false. However, COFF currently relies on this to be true 106 // 107 // As a result we still have some logic in here to improve the quality of the 108 // generated code. 109 // FIXME: Add a module level metadata for whether intrinsics should be assumed 110 // local. 111 if (!GV) 112 return TT.isOSBinFormatCOFF(); 113 114 // If the IR producer requested that this GV be treated as dso local, obey. 115 if (GV->isDSOLocal()) 116 return true; 117 118 // DLLImport explicitly marks the GV as external. 119 if (GV->hasDLLImportStorageClass()) 120 return false; 121 122 // On MinGW, variables that haven't been declared with DLLImport may still 123 // end up automatically imported by the linker. To make this feasible, 124 // don't assume the variables to be DSO local unless we actually know 125 // that for sure. This only has to be done for variables; for functions 126 // the linker can insert thunks for calling functions from another DLL. 127 if (TT.isWindowsGNUEnvironment() && TT.isOSBinFormatCOFF() && 128 GV->isDeclarationForLinker() && isa<GlobalVariable>(GV)) 129 return false; 130 131 // On COFF, don't mark 'extern_weak' symbols as DSO local. If these symbols 132 // remain unresolved in the link, they can be resolved to zero, which is 133 // outside the current DSO. 134 if (TT.isOSBinFormatCOFF() && GV->hasExternalWeakLinkage()) 135 return false; 136 137 // Every other GV is local on COFF. 138 // Make an exception for windows OS in the triple: Some firmware builds use 139 // *-win32-macho triples. This (accidentally?) produced windows relocations 140 // without GOT tables in older clang versions; Keep this behaviour. 141 // Some JIT users use *-win32-elf triples; these shouldn't use GOT tables 142 // either. 143 if (TT.isOSBinFormatCOFF() || TT.isOSWindows()) 144 return true; 145 146 if (TT.isOSBinFormatMachO()) { 147 if (RM == Reloc::Static) 148 return true; 149 return GV->isStrongDefinitionForLinker(); 150 } 151 152 // Due to the AIX linkage model, any global with default visibility is 153 // considered non-local. 154 if (TT.isOSBinFormatXCOFF()) 155 return false; 156 157 assert(TT.isOSBinFormatELF() || TT.isOSBinFormatWasm()); 158 assert(RM != Reloc::DynamicNoPIC); 159 160 bool IsExecutable = 161 RM == Reloc::Static || M.getPIELevel() != PIELevel::Default; 162 if (IsExecutable) { 163 // If the symbol is defined, it cannot be preempted. 164 if (!GV->isDeclarationForLinker()) 165 return true; 166 // FIXME Sanitizers do not call setDSOLocal appropriately. Fix sanitizers 167 // and delete the hack. 168 if (RM == Reloc::Static && !GV->isThreadLocal() && 169 (M.getFunction("asan.module_ctor") || 170 M.getFunction("memprof.module_ctor"))) 171 return true; 172 } else if (TT.isOSBinFormatELF()) { 173 // If dso_local allows AsmPrinter::getSymbolPreferLocal to use a local 174 // alias, set the flag. We cannot set dso_local for other global values, 175 // because otherwise direct accesses to a probably interposable symbol (even 176 // if the codegen assumes not) will be rejected by the linker. 177 if (!GV->canBenefitFromLocalAlias()) 178 return false; 179 return TT.isX86() && M.noSemanticInterposition(); 180 } 181 182 // ELF & wasm support preemption of other symbols. 183 return false; 184 } 185 186 bool TargetMachine::useEmulatedTLS() const { 187 // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls 188 // was specified explicitly; otherwise uses target triple to decide default. 189 if (Options.ExplicitEmulatedTLS) 190 return Options.EmulatedTLS; 191 return getTargetTriple().hasDefaultEmulatedTLS(); 192 } 193 194 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const { 195 bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default; 196 Reloc::Model RM = getRelocationModel(); 197 bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE; 198 bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV); 199 200 TLSModel::Model Model; 201 if (IsSharedLibrary) { 202 if (IsLocal) 203 Model = TLSModel::LocalDynamic; 204 else 205 Model = TLSModel::GeneralDynamic; 206 } else { 207 if (IsLocal) 208 Model = TLSModel::LocalExec; 209 else 210 Model = TLSModel::InitialExec; 211 } 212 213 // If the user specified a more specific model, use that. 214 TLSModel::Model SelectedModel = getSelectedTLSModel(GV); 215 if (SelectedModel > Model) 216 return SelectedModel; 217 218 return Model; 219 } 220 221 /// Returns the optimization level: None, Less, Default, or Aggressive. 222 CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; } 223 224 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; } 225 226 TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) { 227 return TargetTransformInfo(F.getParent()->getDataLayout()); 228 } 229 230 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name, 231 const GlobalValue *GV, Mangler &Mang, 232 bool MayAlwaysUsePrivate) const { 233 if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) { 234 // Simple case: If GV is not private, it is not important to find out if 235 // private labels are legal in this case or not. 236 Mang.getNameWithPrefix(Name, GV, false); 237 return; 238 } 239 const TargetLoweringObjectFile *TLOF = getObjFileLowering(); 240 TLOF->getNameWithPrefix(Name, GV, *this); 241 } 242 243 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const { 244 const TargetLoweringObjectFile *TLOF = getObjFileLowering(); 245 // XCOFF symbols could have special naming convention. 246 if (MCSymbol *TargetSymbol = TLOF->getTargetSymbol(GV, *this)) 247 return TargetSymbol; 248 249 SmallString<128> NameStr; 250 getNameWithPrefix(NameStr, GV, TLOF->getMangler()); 251 return TLOF->getContext().getOrCreateSymbol(NameStr); 252 } 253 254 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() { 255 // Since Analysis can't depend on Target, use a std::function to invert the 256 // dependency. 257 return TargetIRAnalysis( 258 [this](const Function &F) { return this->getTargetTransformInfo(F); }); 259 } 260