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