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 llvm::object; 40 41 using namespace lld; 42 using namespace lld::wasm; 43 44 static std::unique_ptr<lto::LTO> createLTO() { 45 lto::Config C; 46 C.Options = InitTargetOptionsFromCodeGenFlags(); 47 48 // Always emit a section per function/data with LTO. 49 C.Options.FunctionSections = true; 50 C.Options.DataSections = true; 51 52 // Wasm currently only supports ThreadModel::Single 53 C.Options.ThreadModel = ThreadModel::Single; 54 55 C.DisableVerify = Config->DisableVerify; 56 C.DiagHandler = diagnosticHandler; 57 C.OptLevel = Config->LTOO; 58 C.MAttrs = GetMAttrs(); 59 60 if (Config->SaveTemps) 61 checkError(C.addSaveTemps(Config->OutputFile.str() + ".", 62 /*UseInputModulePath*/ true)); 63 64 lto::ThinBackend Backend; 65 if (Config->ThinLTOJobs != -1U) 66 Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs); 67 return llvm::make_unique<lto::LTO>(std::move(C), Backend, 68 Config->LTOPartitions); 69 } 70 71 BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {} 72 73 BitcodeCompiler::~BitcodeCompiler() = default; 74 75 static void undefine(Symbol *S) { 76 if (auto F = dyn_cast<DefinedFunction>(S)) 77 replaceSymbol<UndefinedFunction>(F, F->getName(), 0, F->getFile(), 78 F->FunctionType); 79 else if (isa<DefinedData>(S)) 80 replaceSymbol<UndefinedData>(S, S->getName(), 0, S->getFile()); 81 else 82 llvm_unreachable("unexpected symbol kind"); 83 } 84 85 void BitcodeCompiler::add(BitcodeFile &F) { 86 lto::InputFile &Obj = *F.Obj; 87 unsigned SymNum = 0; 88 ArrayRef<Symbol *> Syms = F.getSymbols(); 89 std::vector<lto::SymbolResolution> Resols(Syms.size()); 90 91 // Provide a resolution to the LTO API for each symbol. 92 for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) { 93 Symbol *Sym = Syms[SymNum]; 94 lto::SymbolResolution &R = Resols[SymNum]; 95 ++SymNum; 96 97 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 98 // reports two symbols for module ASM defined. Without this check, lld 99 // flags an undefined in IR with a definition in ASM as prevailing. 100 // Once IRObjectFile is fixed to report only one symbol this hack can 101 // be removed. 102 R.Prevailing = !ObjSym.isUndefined() && Sym->getFile() == &F; 103 R.VisibleToRegularObj = Config->Relocatable || Sym->IsUsedInRegularObj || 104 (R.Prevailing && Sym->isExported()); 105 if (R.Prevailing) 106 undefine(Sym); 107 } 108 checkError(LTOObj->add(std::move(F.Obj), Resols)); 109 } 110 111 // Merge all the bitcode files we have seen, codegen the result 112 // and return the resulting objects. 113 std::vector<StringRef> BitcodeCompiler::compile() { 114 unsigned MaxTasks = LTOObj->getMaxTasks(); 115 Buf.resize(MaxTasks); 116 Files.resize(MaxTasks); 117 118 // The --thinlto-cache-dir option specifies the path to a directory in which 119 // to cache native object files for ThinLTO incremental builds. If a path was 120 // specified, configure LTO to use it as the cache directory. 121 lto::NativeObjectCache Cache; 122 if (!Config->ThinLTOCacheDir.empty()) 123 Cache = check( 124 lto::localCache(Config->ThinLTOCacheDir, 125 [&](size_t Task, std::unique_ptr<MemoryBuffer> MB) { 126 Files[Task] = std::move(MB); 127 })); 128 129 checkError(LTOObj->run( 130 [&](size_t Task) { 131 return llvm::make_unique<lto::NativeObjectStream>( 132 llvm::make_unique<raw_svector_ostream>(Buf[Task])); 133 }, 134 Cache)); 135 136 if (!Config->ThinLTOCacheDir.empty()) 137 pruneCache(Config->ThinLTOCacheDir, Config->ThinLTOCachePolicy); 138 139 std::vector<StringRef> Ret; 140 for (unsigned I = 0; I != MaxTasks; ++I) { 141 if (Buf[I].empty()) 142 continue; 143 if (Config->SaveTemps) { 144 if (I == 0) 145 saveBuffer(Buf[I], Config->OutputFile + ".lto.o"); 146 else 147 saveBuffer(Buf[I], Config->OutputFile + Twine(I) + ".lto.o"); 148 } 149 Ret.emplace_back(Buf[I].data(), Buf[I].size()); 150 } 151 152 for (std::unique_ptr<MemoryBuffer> &File : Files) 153 if (File) 154 Ret.push_back(File->getBuffer()); 155 156 return Ret; 157 } 158