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