1 //===- LTO.cpp ------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "LTO.h" 10 #include "Config.h" 11 #include "InputFiles.h" 12 #include "Symbols.h" 13 #include "lld/Common/Args.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/Config.h" 23 #include "llvm/LTO/LTO.h" 24 #include "llvm/Object/SymbolicFile.h" 25 #include "llvm/Support/Caching.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 40 namespace lld { 41 namespace wasm { 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 c.DisableVerify = config->disableVerify; 51 c.DiagHandler = diagnosticHandler; 52 c.OptLevel = config->ltoo; 53 c.MAttrs = getMAttrs(); 54 c.CGOptLevel = args::getCGOptLevel(config->ltoo); 55 c.DebugPassManager = config->ltoDebugPassManager; 56 57 if (config->relocatable) 58 c.RelocModel = None; 59 else if (config->isPic) 60 c.RelocModel = Reloc::PIC_; 61 else 62 c.RelocModel = Reloc::Static; 63 64 if (config->saveTemps) 65 checkError(c.addSaveTemps(config->outputFile.str() + ".", 66 /*UseInputModulePath*/ true)); 67 lto::ThinBackend backend = lto::createInProcessThinBackend( 68 llvm::heavyweight_hardware_concurrency(config->thinLTOJobs)); 69 return std::make_unique<lto::LTO>(std::move(c), backend, 70 config->ltoPartitions); 71 } 72 73 BitcodeCompiler::BitcodeCompiler() : ltoObj(createLTO()) {} 74 75 BitcodeCompiler::~BitcodeCompiler() = default; 76 77 static void undefine(Symbol *s) { 78 if (auto f = dyn_cast<DefinedFunction>(s)) 79 replaceSymbol<UndefinedFunction>(f, f->getName(), None, None, 0, 80 f->getFile(), f->signature); 81 else if (isa<DefinedData>(s)) 82 replaceSymbol<UndefinedData>(s, s->getName(), 0, s->getFile()); 83 else 84 llvm_unreachable("unexpected symbol kind"); 85 } 86 87 void BitcodeCompiler::add(BitcodeFile &f) { 88 lto::InputFile &obj = *f.obj; 89 unsigned symNum = 0; 90 ArrayRef<Symbol *> syms = f.getSymbols(); 91 std::vector<lto::SymbolResolution> resols(syms.size()); 92 93 // Provide a resolution to the LTO API for each symbol. 94 for (const lto::InputFile::Symbol &objSym : obj.symbols()) { 95 Symbol *sym = syms[symNum]; 96 lto::SymbolResolution &r = resols[symNum]; 97 ++symNum; 98 99 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 100 // reports two symbols for module ASM defined. Without this check, lld 101 // flags an undefined in IR with a definition in ASM as prevailing. 102 // Once IRObjectFile is fixed to report only one symbol this hack can 103 // be removed. 104 r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f; 105 r.VisibleToRegularObj = config->relocatable || sym->isUsedInRegularObj || 106 sym->isNoStrip() || 107 (r.Prevailing && sym->isExported()); 108 if (r.Prevailing) 109 undefine(sym); 110 111 // We tell LTO to not apply interprocedural optimization for wrapped 112 // (with --wrap) symbols because otherwise LTO would inline them while 113 // their values are still not final. 114 r.LinkerRedefined = !sym->canInline; 115 } 116 checkError(ltoObj->add(std::move(f.obj), resols)); 117 } 118 119 // Merge all the bitcode files we have seen, codegen the result 120 // and return the resulting objects. 121 std::vector<StringRef> BitcodeCompiler::compile() { 122 unsigned maxTasks = ltoObj->getMaxTasks(); 123 buf.resize(maxTasks); 124 files.resize(maxTasks); 125 126 // The --thinlto-cache-dir option specifies the path to a directory in which 127 // to cache native object files for ThinLTO incremental builds. If a path was 128 // specified, configure LTO to use it as the cache directory. 129 FileCache cache; 130 if (!config->thinLTOCacheDir.empty()) 131 cache = 132 check(localCache("ThinLTO", "Thin", config->thinLTOCacheDir, 133 [&](size_t task, std::unique_ptr<MemoryBuffer> mb) { 134 files[task] = std::move(mb); 135 })); 136 137 checkError(ltoObj->run( 138 [&](size_t task) { 139 return std::make_unique<CachedFileStream>( 140 std::make_unique<raw_svector_ostream>(buf[task])); 141 }, 142 cache)); 143 144 if (!config->thinLTOCacheDir.empty()) 145 pruneCache(config->thinLTOCacheDir, config->thinLTOCachePolicy); 146 147 std::vector<StringRef> ret; 148 for (unsigned i = 0; i != maxTasks; ++i) { 149 if (buf[i].empty()) 150 continue; 151 if (config->saveTemps) { 152 if (i == 0) 153 saveBuffer(buf[i], config->outputFile + ".lto.o"); 154 else 155 saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.o"); 156 } 157 ret.emplace_back(buf[i].data(), buf[i].size()); 158 } 159 160 for (std::unique_ptr<MemoryBuffer> &file : files) 161 if (file) 162 ret.push_back(file->getBuffer()); 163 164 return ret; 165 } 166 167 } // namespace wasm 168 } // namespace lld 169