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1 //===- LTO.cpp ------------------------------------------------------------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #include "LTO.h"
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10 #include "Config.h"
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11 #include "InputFiles.h"
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12 #include "Symbols.h"
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13 #include "lld/Common/Args.h"
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14 #include "lld/Common/ErrorHandler.h"
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15 #include "lld/Common/Strings.h"
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16 #include "lld/Common/TargetOptionsCommandFlags.h"
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17 #include "llvm/ADT/STLExtras.h"
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18 #include "llvm/ADT/SmallString.h"
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19 #include "llvm/ADT/StringRef.h"
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20 #include "llvm/ADT/Twine.h"
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21 #include "llvm/IR/DiagnosticPrinter.h"
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22 #include "llvm/LTO/Caching.h"
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23 #include "llvm/LTO/Config.h"
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24 #include "llvm/LTO/LTO.h"
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25 #include "llvm/Object/SymbolicFile.h"
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26 #include "llvm/Support/CodeGen.h"
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27 #include "llvm/Support/Error.h"
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28 #include "llvm/Support/FileSystem.h"
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29 #include "llvm/Support/MemoryBuffer.h"
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30 #include "llvm/Support/raw_ostream.h"
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31 #include <algorithm>
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32 #include <cstddef>
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33 #include <memory>
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34 #include <string>
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35 #include <system_error>
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36 #include <vector>
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37
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38 using namespace llvm;
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39
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40 namespace lld {
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41 namespace wasm {
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42 static std::unique_ptr<lto::LTO> createLTO() {
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43 lto::Config c;
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44 c.Options = initTargetOptionsFromCodeGenFlags();
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45
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46 // Always emit a section per function/data with LTO.
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47 c.Options.FunctionSections = true;
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48 c.Options.DataSections = true;
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49
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50 c.DisableVerify = config->disableVerify;
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51 c.DiagHandler = diagnosticHandler;
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52 c.OptLevel = config->ltoo;
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53 c.MAttrs = getMAttrs();
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54 c.CGOptLevel = args::getCGOptLevel(config->ltoo);
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207
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55 c.UseNewPM = config->ltoNewPassManager;
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56 c.DebugPassManager = config->ltoDebugPassManager;
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150
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57
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58 if (config->relocatable)
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59 c.RelocModel = None;
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60 else if (config->isPic)
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61 c.RelocModel = Reloc::PIC_;
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62 else
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63 c.RelocModel = Reloc::Static;
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64
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65 if (config->saveTemps)
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66 checkError(c.addSaveTemps(config->outputFile.str() + ".",
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67 /*UseInputModulePath*/ true));
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173
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68 lto::ThinBackend backend = lto::createInProcessThinBackend(
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69 llvm::heavyweight_hardware_concurrency(config->thinLTOJobs));
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150
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70 return std::make_unique<lto::LTO>(std::move(c), backend,
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71 config->ltoPartitions);
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72 }
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73
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74 BitcodeCompiler::BitcodeCompiler() : ltoObj(createLTO()) {}
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75
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76 BitcodeCompiler::~BitcodeCompiler() = default;
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77
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78 static void undefine(Symbol *s) {
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79 if (auto f = dyn_cast<DefinedFunction>(s))
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173
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80 replaceSymbol<UndefinedFunction>(f, f->getName(), None, None, 0,
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81 f->getFile(), f->signature);
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150
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82 else if (isa<DefinedData>(s))
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83 replaceSymbol<UndefinedData>(s, s->getName(), 0, s->getFile());
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84 else
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85 llvm_unreachable("unexpected symbol kind");
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86 }
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87
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88 void BitcodeCompiler::add(BitcodeFile &f) {
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89 lto::InputFile &obj = *f.obj;
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90 unsigned symNum = 0;
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91 ArrayRef<Symbol *> syms = f.getSymbols();
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92 std::vector<lto::SymbolResolution> resols(syms.size());
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93
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94 // Provide a resolution to the LTO API for each symbol.
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95 for (const lto::InputFile::Symbol &objSym : obj.symbols()) {
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96 Symbol *sym = syms[symNum];
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97 lto::SymbolResolution &r = resols[symNum];
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98 ++symNum;
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99
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100 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
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101 // reports two symbols for module ASM defined. Without this check, lld
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102 // flags an undefined in IR with a definition in ASM as prevailing.
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103 // Once IRObjectFile is fixed to report only one symbol this hack can
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104 // be removed.
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105 r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f;
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106 r.VisibleToRegularObj = config->relocatable || sym->isUsedInRegularObj ||
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107 sym->isNoStrip() ||
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108 (r.Prevailing && sym->isExported());
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109 if (r.Prevailing)
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110 undefine(sym);
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111
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112 // We tell LTO to not apply interprocedural optimization for wrapped
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113 // (with --wrap) symbols because otherwise LTO would inline them while
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114 // their values are still not final.
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115 r.LinkerRedefined = !sym->canInline;
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116 }
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117 checkError(ltoObj->add(std::move(f.obj), resols));
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118 }
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119
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120 // Merge all the bitcode files we have seen, codegen the result
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121 // and return the resulting objects.
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122 std::vector<StringRef> BitcodeCompiler::compile() {
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123 unsigned maxTasks = ltoObj->getMaxTasks();
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124 buf.resize(maxTasks);
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125 files.resize(maxTasks);
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126
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127 // The --thinlto-cache-dir option specifies the path to a directory in which
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128 // to cache native object files for ThinLTO incremental builds. If a path was
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129 // specified, configure LTO to use it as the cache directory.
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130 lto::NativeObjectCache cache;
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131 if (!config->thinLTOCacheDir.empty())
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132 cache = check(
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133 lto::localCache(config->thinLTOCacheDir,
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134 [&](size_t task, std::unique_ptr<MemoryBuffer> mb) {
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135 files[task] = std::move(mb);
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136 }));
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137
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138 checkError(ltoObj->run(
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139 [&](size_t task) {
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140 return std::make_unique<lto::NativeObjectStream>(
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141 std::make_unique<raw_svector_ostream>(buf[task]));
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142 },
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143 cache));
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144
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145 if (!config->thinLTOCacheDir.empty())
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146 pruneCache(config->thinLTOCacheDir, config->thinLTOCachePolicy);
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147
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148 std::vector<StringRef> ret;
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149 for (unsigned i = 0; i != maxTasks; ++i) {
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150 if (buf[i].empty())
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151 continue;
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152 if (config->saveTemps) {
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153 if (i == 0)
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154 saveBuffer(buf[i], config->outputFile + ".lto.o");
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155 else
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156 saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.o");
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157 }
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158 ret.emplace_back(buf[i].data(), buf[i].size());
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159 }
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160
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161 for (std::unique_ptr<MemoryBuffer> &file : files)
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162 if (file)
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163 ret.push_back(file->getBuffer());
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164
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165 return ret;
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166 }
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167
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168 } // namespace wasm
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169 } // namespace lld
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