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