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/GlobalValue.h" 17 #include "llvm/IR/GlobalVariable.h" 18 #include "llvm/IR/Mangler.h" 19 #include "llvm/MC/MCAsmInfo.h" 20 #include "llvm/MC/MCContext.h" 21 #include "llvm/MC/MCInstrInfo.h" 22 #include "llvm/MC/MCRegisterInfo.h" 23 #include "llvm/MC/MCSubtargetInfo.h" 24 #include "llvm/Target/TargetLoweringObjectFile.h" 25 using namespace llvm; 26 27 //--------------------------------------------------------------------------- 28 // TargetMachine Class 29 // 30 31 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString, 32 const Triple &TT, StringRef CPU, StringRef FS, 33 const TargetOptions &Options) 34 : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), 35 TargetCPU(std::string(CPU)), TargetFS(std::string(FS)), AsmInfo(nullptr), 36 MRI(nullptr), MII(nullptr), STI(nullptr), RequireStructuredCFG(false), 37 O0WantsFastISel(false), DefaultOptions(Options), Options(Options) {} 38 39 TargetMachine::~TargetMachine() = default; 40 41 bool TargetMachine::isPositionIndependent() const { 42 return getRelocationModel() == Reloc::PIC_; 43 } 44 45 /// Reset the target options based on the function's attributes. 46 /// setFunctionAttributes should have made the raw attribute value consistent 47 /// with the command line flag if used. 48 // 49 // FIXME: This function needs to go away for a number of reasons: 50 // a) global state on the TargetMachine is terrible in general, 51 // b) these target options should be passed only on the function 52 // and not on the TargetMachine (via TargetOptions) at all. 53 void TargetMachine::resetTargetOptions(const Function &F) const { 54 #define RESET_OPTION(X, Y) \ 55 do { \ 56 Options.X = F.getFnAttribute(Y).getValueAsBool(); \ 57 } while (0) 58 59 RESET_OPTION(UnsafeFPMath, "unsafe-fp-math"); 60 RESET_OPTION(NoInfsFPMath, "no-infs-fp-math"); 61 RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math"); 62 RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math"); 63 RESET_OPTION(ApproxFuncFPMath, "approx-func-fp-math"); 64 } 65 66 /// Returns the code generation relocation model. The choices are static, PIC, 67 /// and dynamic-no-pic. 68 Reloc::Model TargetMachine::getRelocationModel() const { return RM; } 69 70 /// Get the IR-specified TLS model for Var. 71 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) { 72 switch (GV->getThreadLocalMode()) { 73 case GlobalVariable::NotThreadLocal: 74 llvm_unreachable("getSelectedTLSModel for non-TLS variable"); 75 break; 76 case GlobalVariable::GeneralDynamicTLSModel: 77 return TLSModel::GeneralDynamic; 78 case GlobalVariable::LocalDynamicTLSModel: 79 return TLSModel::LocalDynamic; 80 case GlobalVariable::InitialExecTLSModel: 81 return TLSModel::InitialExec; 82 case GlobalVariable::LocalExecTLSModel: 83 return TLSModel::LocalExec; 84 } 85 llvm_unreachable("invalid TLS model"); 86 } 87 88 bool TargetMachine::shouldAssumeDSOLocal(const Module &M, 89 const GlobalValue *GV) const { 90 const Triple &TT = getTargetTriple(); 91 Reloc::Model RM = getRelocationModel(); 92 93 // According to the llvm language reference, we should be able to 94 // just return false in here if we have a GV, as we know it is 95 // dso_preemptable. At this point in time, the various IR producers 96 // have not been transitioned to always produce a dso_local when it 97 // is possible to do so. 98 // 99 // As a result we still have some logic in here to improve the quality of the 100 // generated code. 101 if (!GV) 102 return false; 103 104 // If the IR producer requested that this GV be treated as dso local, obey. 105 if (GV->isDSOLocal()) 106 return true; 107 108 if (TT.isOSBinFormatCOFF()) { 109 // DLLImport explicitly marks the GV as external. 110 if (GV->hasDLLImportStorageClass()) 111 return false; 112 113 // On MinGW, variables that haven't been declared with DLLImport may still 114 // end up automatically imported by the linker. To make this feasible, 115 // don't assume the variables to be DSO local unless we actually know 116 // that for sure. This only has to be done for variables; for functions 117 // the linker can insert thunks for calling functions from another DLL. 118 if (TT.isWindowsGNUEnvironment() && GV->isDeclarationForLinker() && 119 isa<GlobalVariable>(GV)) 120 return false; 121 122 // Don't mark 'extern_weak' symbols as DSO local. If these symbols remain 123 // unresolved in the link, they can be resolved to zero, which is outside 124 // the current DSO. 125 if (GV->hasExternalWeakLinkage()) 126 return false; 127 128 // Every other GV is local on COFF. 129 return true; 130 } 131 132 if (TT.isOSBinFormatGOFF()) 133 return true; 134 135 if (TT.isOSBinFormatMachO()) { 136 if (RM == Reloc::Static) 137 return true; 138 return GV->isStrongDefinitionForLinker(); 139 } 140 141 assert(TT.isOSBinFormatELF() || TT.isOSBinFormatWasm() || 142 TT.isOSBinFormatXCOFF()); 143 return false; 144 } 145 146 bool TargetMachine::useEmulatedTLS() const { 147 // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls 148 // was specified explicitly; otherwise uses target triple to decide default. 149 if (Options.ExplicitEmulatedTLS) 150 return Options.EmulatedTLS; 151 return getTargetTriple().hasDefaultEmulatedTLS(); 152 } 153 154 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const { 155 bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default; 156 Reloc::Model RM = getRelocationModel(); 157 bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE; 158 bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV); 159 160 TLSModel::Model Model; 161 if (IsSharedLibrary) { 162 if (IsLocal) 163 Model = TLSModel::LocalDynamic; 164 else 165 Model = TLSModel::GeneralDynamic; 166 } else { 167 if (IsLocal) 168 Model = TLSModel::LocalExec; 169 else 170 Model = TLSModel::InitialExec; 171 } 172 173 // If the user specified a more specific model, use that. 174 TLSModel::Model SelectedModel = getSelectedTLSModel(GV); 175 if (SelectedModel > Model) 176 return SelectedModel; 177 178 return Model; 179 } 180 181 /// Returns the optimization level: None, Less, Default, or Aggressive. 182 CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; } 183 184 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; } 185 186 TargetTransformInfo 187 TargetMachine::getTargetTransformInfo(const Function &F) const { 188 return TargetTransformInfo(F.getParent()->getDataLayout()); 189 } 190 191 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name, 192 const GlobalValue *GV, Mangler &Mang, 193 bool MayAlwaysUsePrivate) const { 194 if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) { 195 // Simple case: If GV is not private, it is not important to find out if 196 // private labels are legal in this case or not. 197 Mang.getNameWithPrefix(Name, GV, false); 198 return; 199 } 200 const TargetLoweringObjectFile *TLOF = getObjFileLowering(); 201 TLOF->getNameWithPrefix(Name, GV, *this); 202 } 203 204 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const { 205 const TargetLoweringObjectFile *TLOF = getObjFileLowering(); 206 // XCOFF symbols could have special naming convention. 207 if (MCSymbol *TargetSymbol = TLOF->getTargetSymbol(GV, *this)) 208 return TargetSymbol; 209 210 SmallString<128> NameStr; 211 getNameWithPrefix(NameStr, GV, TLOF->getMangler()); 212 return TLOF->getContext().getOrCreateSymbol(NameStr); 213 } 214 215 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() const { 216 // Since Analysis can't depend on Target, use a std::function to invert the 217 // dependency. 218 return TargetIRAnalysis( 219 [this](const Function &F) { return this->getTargetTransformInfo(F); }); 220 } 221 222 std::pair<int, int> TargetMachine::parseBinutilsVersion(StringRef Version) { 223 if (Version == "none") 224 return {INT_MAX, INT_MAX}; // Make binutilsIsAtLeast() return true. 225 std::pair<int, int> Ret; 226 if (!Version.consumeInteger(10, Ret.first) && Version.consume_front(".")) 227 Version.consumeInteger(10, Ret.second); 228 return Ret; 229 } 230