1 //===- LTO.cpp ------------------------------------------------------------===// 2 // 3 // The LLVM Linker 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "LTO.h" 11 #include "Config.h" 12 #include "InputFiles.h" 13 #include "Symbols.h" 14 #include "lld/Common/ErrorHandler.h" 15 #include "lld/Common/Strings.h" 16 #include "lld/Common/TargetOptionsCommandFlags.h" 17 #include "llvm/ADT/STLExtras.h" 18 #include "llvm/ADT/SmallString.h" 19 #include "llvm/ADT/StringRef.h" 20 #include "llvm/ADT/Twine.h" 21 #include "llvm/IR/DiagnosticPrinter.h" 22 #include "llvm/LTO/Caching.h" 23 #include "llvm/LTO/Config.h" 24 #include "llvm/LTO/LTO.h" 25 #include "llvm/Object/SymbolicFile.h" 26 #include "llvm/Support/CodeGen.h" 27 #include "llvm/Support/Error.h" 28 #include "llvm/Support/FileSystem.h" 29 #include "llvm/Support/MemoryBuffer.h" 30 #include "llvm/Support/raw_ostream.h" 31 #include <algorithm> 32 #include <cstddef> 33 #include <memory> 34 #include <string> 35 #include <system_error> 36 #include <vector> 37 38 using namespace llvm; 39 using namespace lld; 40 using namespace lld::wasm; 41 42 static std::unique_ptr<lto::LTO> createLTO() { 43 lto::Config C; 44 C.Options = InitTargetOptionsFromCodeGenFlags(); 45 46 // Always emit a section per function/data with LTO. 47 C.Options.FunctionSections = true; 48 C.Options.DataSections = true; 49 50 // Wasm currently only supports ThreadModel::Single 51 C.Options.ThreadModel = ThreadModel::Single; 52 53 C.DisableVerify = Config->DisableVerify; 54 C.DiagHandler = diagnosticHandler; 55 C.OptLevel = Config->LTOO; 56 C.MAttrs = GetMAttrs(); 57 58 if (Config->Relocatable) 59 C.RelocModel = None; 60 else if (Config->Pic) 61 C.RelocModel = Reloc::PIC_; 62 else 63 C.RelocModel = Reloc::Static; 64 65 if (Config->SaveTemps) 66 checkError(C.addSaveTemps(Config->OutputFile.str() + ".", 67 /*UseInputModulePath*/ true)); 68 69 lto::ThinBackend Backend; 70 if (Config->ThinLTOJobs != -1U) 71 Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs); 72 return llvm::make_unique<lto::LTO>(std::move(C), Backend, 73 Config->LTOPartitions); 74 } 75 76 BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {} 77 78 BitcodeCompiler::~BitcodeCompiler() = default; 79 80 static void undefine(Symbol *S) { 81 if (auto F = dyn_cast<DefinedFunction>(S)) 82 replaceSymbol<UndefinedFunction>(F, F->getName(), 0, F->getFile(), 83 F->Signature); 84 else if (isa<DefinedData>(S)) 85 replaceSymbol<UndefinedData>(S, S->getName(), 0, S->getFile()); 86 else 87 llvm_unreachable("unexpected symbol kind"); 88 } 89 90 void BitcodeCompiler::add(BitcodeFile &F) { 91 lto::InputFile &Obj = *F.Obj; 92 unsigned SymNum = 0; 93 ArrayRef<Symbol *> Syms = F.getSymbols(); 94 std::vector<lto::SymbolResolution> Resols(Syms.size()); 95 96 // Provide a resolution to the LTO API for each symbol. 97 for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) { 98 Symbol *Sym = Syms[SymNum]; 99 lto::SymbolResolution &R = Resols[SymNum]; 100 ++SymNum; 101 102 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 103 // reports two symbols for module ASM defined. Without this check, lld 104 // flags an undefined in IR with a definition in ASM as prevailing. 105 // Once IRObjectFile is fixed to report only one symbol this hack can 106 // be removed. 107 R.Prevailing = !ObjSym.isUndefined() && Sym->getFile() == &F; 108 R.VisibleToRegularObj = Config->Relocatable || Sym->IsUsedInRegularObj || 109 (R.Prevailing && Sym->isExported()); 110 if (R.Prevailing) 111 undefine(Sym); 112 } 113 checkError(LTOObj->add(std::move(F.Obj), Resols)); 114 } 115 116 // Merge all the bitcode files we have seen, codegen the result 117 // and return the resulting objects. 118 std::vector<StringRef> BitcodeCompiler::compile() { 119 unsigned MaxTasks = LTOObj->getMaxTasks(); 120 Buf.resize(MaxTasks); 121 Files.resize(MaxTasks); 122 123 // The --thinlto-cache-dir option specifies the path to a directory in which 124 // to cache native object files for ThinLTO incremental builds. If a path was 125 // specified, configure LTO to use it as the cache directory. 126 lto::NativeObjectCache Cache; 127 if (!Config->ThinLTOCacheDir.empty()) 128 Cache = check( 129 lto::localCache(Config->ThinLTOCacheDir, 130 [&](size_t Task, std::unique_ptr<MemoryBuffer> MB) { 131 Files[Task] = std::move(MB); 132 })); 133 134 checkError(LTOObj->run( 135 [&](size_t Task) { 136 return llvm::make_unique<lto::NativeObjectStream>( 137 llvm::make_unique<raw_svector_ostream>(Buf[Task])); 138 }, 139 Cache)); 140 141 if (!Config->ThinLTOCacheDir.empty()) 142 pruneCache(Config->ThinLTOCacheDir, Config->ThinLTOCachePolicy); 143 144 std::vector<StringRef> Ret; 145 for (unsigned I = 0; I != MaxTasks; ++I) { 146 if (Buf[I].empty()) 147 continue; 148 if (Config->SaveTemps) { 149 if (I == 0) 150 saveBuffer(Buf[I], Config->OutputFile + ".lto.o"); 151 else 152 saveBuffer(Buf[I], Config->OutputFile + Twine(I) + ".lto.o"); 153 } 154 Ret.emplace_back(Buf[I].data(), Buf[I].size()); 155 } 156 157 for (std::unique_ptr<MemoryBuffer> &File : Files) 158 if (File) 159 Ret.push_back(File->getBuffer()); 160 161 return Ret; 162 } 163