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