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).getValueAsBool(); \ 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 return false; 160 } 161 162 bool TargetMachine::useEmulatedTLS() const { 163 // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls 164 // was specified explicitly; otherwise uses target triple to decide default. 165 if (Options.ExplicitEmulatedTLS) 166 return Options.EmulatedTLS; 167 return getTargetTriple().hasDefaultEmulatedTLS(); 168 } 169 170 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const { 171 bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default; 172 Reloc::Model RM = getRelocationModel(); 173 bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE; 174 bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV); 175 176 TLSModel::Model Model; 177 if (IsSharedLibrary) { 178 if (IsLocal) 179 Model = TLSModel::LocalDynamic; 180 else 181 Model = TLSModel::GeneralDynamic; 182 } else { 183 if (IsLocal) 184 Model = TLSModel::LocalExec; 185 else 186 Model = TLSModel::InitialExec; 187 } 188 189 // If the user specified a more specific model, use that. 190 TLSModel::Model SelectedModel = getSelectedTLSModel(GV); 191 if (SelectedModel > Model) 192 return SelectedModel; 193 194 return Model; 195 } 196 197 /// Returns the optimization level: None, Less, Default, or Aggressive. 198 CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; } 199 200 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; } 201 202 TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) { 203 return TargetTransformInfo(F.getParent()->getDataLayout()); 204 } 205 206 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name, 207 const GlobalValue *GV, Mangler &Mang, 208 bool MayAlwaysUsePrivate) const { 209 if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) { 210 // Simple case: If GV is not private, it is not important to find out if 211 // private labels are legal in this case or not. 212 Mang.getNameWithPrefix(Name, GV, false); 213 return; 214 } 215 const TargetLoweringObjectFile *TLOF = getObjFileLowering(); 216 TLOF->getNameWithPrefix(Name, GV, *this); 217 } 218 219 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const { 220 const TargetLoweringObjectFile *TLOF = getObjFileLowering(); 221 // XCOFF symbols could have special naming convention. 222 if (MCSymbol *TargetSymbol = TLOF->getTargetSymbol(GV, *this)) 223 return TargetSymbol; 224 225 SmallString<128> NameStr; 226 getNameWithPrefix(NameStr, GV, TLOF->getMangler()); 227 return TLOF->getContext().getOrCreateSymbol(NameStr); 228 } 229 230 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() { 231 // Since Analysis can't depend on Target, use a std::function to invert the 232 // dependency. 233 return TargetIRAnalysis( 234 [this](const Function &F) { return this->getTargetTransformInfo(F); }); 235 } 236 237 std::pair<int, int> TargetMachine::parseBinutilsVersion(StringRef Version) { 238 if (Version == "none") 239 return {INT_MAX, INT_MAX}; // Make binutilsIsAtLeast() return true. 240 std::pair<int, int> Ret; 241 if (!Version.consumeInteger(10, Ret.first) && Version.consume_front(".")) 242 Version.consumeInteger(10, Ret.second); 243 return Ret; 244 } 245