1 //===-ThinLTOCodeGenerator.h - LLVM Link Time Optimizer -------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file declares the ThinLTOCodeGenerator class, similar to the 11 // LTOCodeGenerator but for the ThinLTO scheme. It provides an interface for 12 // linker plugin. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #ifndef LLVM_LTO_THINLTOCODEGENERATOR_H 17 #define LLVM_LTO_THINLTOCODEGENERATOR_H 18 19 #include "llvm-c/lto.h" 20 #include "llvm/ADT/StringSet.h" 21 #include "llvm/ADT/Triple.h" 22 #include "llvm/IR/ModuleSummaryIndex.h" 23 #include "llvm/Support/CachePruning.h" 24 #include "llvm/Support/CodeGen.h" 25 #include "llvm/Support/MemoryBuffer.h" 26 #include "llvm/Target/TargetOptions.h" 27 28 #include <string> 29 30 namespace llvm { 31 class StringRef; 32 class LLVMContext; 33 class TargetMachine; 34 35 /// Wrapper around MemoryBufferRef, owning the identifier 36 class ThinLTOBuffer { 37 std::string OwnedIdentifier; 38 StringRef Buffer; 39 40 public: 41 ThinLTOBuffer(StringRef Buffer, StringRef Identifier) 42 : OwnedIdentifier(Identifier), Buffer(Buffer) {} 43 44 MemoryBufferRef getMemBuffer() const { 45 return MemoryBufferRef(Buffer, 46 {OwnedIdentifier.c_str(), OwnedIdentifier.size()}); 47 } 48 StringRef getBuffer() const { return Buffer; } 49 StringRef getBufferIdentifier() const { return OwnedIdentifier; } 50 }; 51 52 /// Helper to gather options relevant to the target machine creation 53 struct TargetMachineBuilder { 54 Triple TheTriple; 55 std::string MCpu; 56 std::string MAttr; 57 TargetOptions Options; 58 Optional<Reloc::Model> RelocModel; 59 CodeGenOpt::Level CGOptLevel = CodeGenOpt::Aggressive; 60 61 std::unique_ptr<TargetMachine> create() const; 62 }; 63 64 /// This class define an interface similar to the LTOCodeGenerator, but adapted 65 /// for ThinLTO processing. 66 /// The ThinLTOCodeGenerator is not intended to be reuse for multiple 67 /// compilation: the model is that the client adds modules to the generator and 68 /// ask to perform the ThinLTO optimizations / codegen, and finally destroys the 69 /// codegenerator. 70 class ThinLTOCodeGenerator { 71 public: 72 /// Add given module to the code generator. 73 void addModule(StringRef Identifier, StringRef Data); 74 75 /** 76 * Adds to a list of all global symbols that must exist in the final generated 77 * code. If a symbol is not listed there, it will be optimized away if it is 78 * inlined into every usage. 79 */ 80 void preserveSymbol(StringRef Name); 81 82 /** 83 * Adds to a list of all global symbols that are cross-referenced between 84 * ThinLTO files. If the ThinLTO CodeGenerator can ensure that every 85 * references from a ThinLTO module to this symbol is optimized away, then 86 * the symbol can be discarded. 87 */ 88 void crossReferenceSymbol(StringRef Name); 89 90 /** 91 * Process all the modules that were added to the code generator in parallel. 92 * 93 * Client can access the resulting object files using getProducedBinaries(), 94 * unless setGeneratedObjectsDirectory() has been called, in which case 95 * results are available through getProducedBinaryFiles(). 96 */ 97 void run(); 98 99 /** 100 * Return the "in memory" binaries produced by the code generator. This is 101 * filled after run() unless setGeneratedObjectsDirectory() has been 102 * called, in which case results are available through 103 * getProducedBinaryFiles(). 104 */ 105 std::vector<std::unique_ptr<MemoryBuffer>> &getProducedBinaries() { 106 return ProducedBinaries; 107 } 108 109 /** 110 * Return the "on-disk" binaries produced by the code generator. This is 111 * filled after run() when setGeneratedObjectsDirectory() has been 112 * called, in which case results are available through getProducedBinaries(). 113 */ 114 std::vector<std::string> &getProducedBinaryFiles() { 115 return ProducedBinaryFiles; 116 } 117 118 /** 119 * \defgroup Options setters 120 * @{ 121 */ 122 123 /** 124 * \defgroup Cache controlling options 125 * 126 * These entry points control the ThinLTO cache. The cache is intended to 127 * support incremental build, and thus needs to be persistent accross build. 128 * The client enabled the cache by supplying a path to an existing directory. 129 * The code generator will use this to store objects files that may be reused 130 * during a subsequent build. 131 * To avoid filling the disk space, a few knobs are provided: 132 * - The pruning interval limit the frequency at which the garbage collector 133 * will try to scan the cache directory to prune it from expired entries. 134 * Setting to -1 disable the pruning (default). 135 * - The pruning expiration time indicates to the garbage collector how old 136 * an entry needs to be to be removed. 137 * - Finally, the garbage collector can be instructed to prune the cache till 138 * the occupied space goes below a threshold. 139 * @{ 140 */ 141 142 struct CachingOptions { 143 std::string Path; // Path to the cache, empty to disable. 144 CachePruningPolicy Policy; 145 }; 146 147 /// Provide a path to a directory where to store the cached files for 148 /// incremental build. 149 void setCacheDir(std::string Path) { CacheOptions.Path = std::move(Path); } 150 151 /// Cache policy: interval (seconds) between two prune of the cache. Set to a 152 /// negative value (default) to disable pruning. A value of 0 will be ignored. 153 void setCachePruningInterval(int Interval) { 154 if (Interval) 155 CacheOptions.Policy.Interval = std::chrono::seconds(Interval); 156 } 157 158 /// Cache policy: expiration (in seconds) for an entry. 159 /// A value of 0 will be ignored. 160 void setCacheEntryExpiration(unsigned Expiration) { 161 if (Expiration) 162 CacheOptions.Policy.Expiration = std::chrono::seconds(Expiration); 163 } 164 165 /** 166 * Sets the maximum cache size that can be persistent across build, in terms 167 * of percentage of the available space on the the disk. Set to 100 to 168 * indicate no limit, 50 to indicate that the cache size will not be left over 169 * half the available space. A value over 100 will be reduced to 100, and a 170 * value of 0 will be ignored. 171 * 172 * 173 * The formula looks like: 174 * AvailableSpace = FreeSpace + ExistingCacheSize 175 * NewCacheSize = AvailableSpace * P/100 176 * 177 */ 178 void setMaxCacheSizeRelativeToAvailableSpace(unsigned Percentage) { 179 if (Percentage) 180 CacheOptions.Policy.MaxSizePercentageOfAvailableSpace = Percentage; 181 } 182 183 /**@}*/ 184 185 /// Set the path to a directory where to save temporaries at various stages of 186 /// the processing. 187 void setSaveTempsDir(std::string Path) { SaveTempsDir = std::move(Path); } 188 189 /// Set the path to a directory where to save generated object files. This 190 /// path can be used by a linker to request on-disk files instead of in-memory 191 /// buffers. When set, results are available through getProducedBinaryFiles() 192 /// instead of getProducedBinaries(). 193 void setGeneratedObjectsDirectory(std::string Path) { 194 SavedObjectsDirectoryPath = std::move(Path); 195 } 196 197 /// CPU to use to initialize the TargetMachine 198 void setCpu(std::string Cpu) { TMBuilder.MCpu = std::move(Cpu); } 199 200 /// Subtarget attributes 201 void setAttr(std::string MAttr) { TMBuilder.MAttr = std::move(MAttr); } 202 203 /// TargetMachine options 204 void setTargetOptions(TargetOptions Options) { 205 TMBuilder.Options = std::move(Options); 206 } 207 208 /// Enable the Freestanding mode: indicate that the optimizer should not 209 /// assume builtins are present on the target. 210 void setFreestanding(bool Enabled) { Freestanding = Enabled; } 211 212 /// CodeModel 213 void setCodePICModel(Optional<Reloc::Model> Model) { 214 TMBuilder.RelocModel = Model; 215 } 216 217 /// CodeGen optimization level 218 void setCodeGenOptLevel(CodeGenOpt::Level CGOptLevel) { 219 TMBuilder.CGOptLevel = CGOptLevel; 220 } 221 222 /// IR optimization level: from 0 to 3. 223 void setOptLevel(unsigned NewOptLevel) { 224 OptLevel = (NewOptLevel > 3) ? 3 : NewOptLevel; 225 } 226 227 /// Disable CodeGen, only run the stages till codegen and stop. The output 228 /// will be bitcode. 229 void disableCodeGen(bool Disable) { DisableCodeGen = Disable; } 230 231 /// Perform CodeGen only: disable all other stages. 232 void setCodeGenOnly(bool CGOnly) { CodeGenOnly = CGOnly; } 233 234 /**@}*/ 235 236 /** 237 * \defgroup Set of APIs to run individual stages in isolation. 238 * @{ 239 */ 240 241 /** 242 * Produce the combined summary index from all the bitcode files: 243 * "thin-link". 244 */ 245 std::unique_ptr<ModuleSummaryIndex> linkCombinedIndex(); 246 247 /** 248 * Perform promotion and renaming of exported internal functions, 249 * and additionally resolve weak and linkonce symbols. 250 * Index is updated to reflect linkage changes from weak resolution. 251 */ 252 void promote(Module &Module, ModuleSummaryIndex &Index); 253 254 /** 255 * Compute and emit the imported files for module at \p ModulePath. 256 */ 257 static void emitImports(StringRef ModulePath, StringRef OutputName, 258 ModuleSummaryIndex &Index); 259 260 /** 261 * Perform cross-module importing for the module identified by 262 * ModuleIdentifier. 263 */ 264 void crossModuleImport(Module &Module, ModuleSummaryIndex &Index); 265 266 /** 267 * Compute the list of summaries needed for importing into module. 268 */ 269 static void gatherImportedSummariesForModule( 270 StringRef ModulePath, ModuleSummaryIndex &Index, 271 std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex); 272 273 /** 274 * Perform internalization. Index is updated to reflect linkage changes. 275 */ 276 void internalize(Module &Module, ModuleSummaryIndex &Index); 277 278 /** 279 * Perform post-importing ThinLTO optimizations. 280 */ 281 void optimize(Module &Module); 282 283 /** 284 * Perform ThinLTO CodeGen. 285 */ 286 std::unique_ptr<MemoryBuffer> codegen(Module &Module); 287 288 /**@}*/ 289 290 private: 291 /// Helper factory to build a TargetMachine 292 TargetMachineBuilder TMBuilder; 293 294 /// Vector holding the in-memory buffer containing the produced binaries, when 295 /// SavedObjectsDirectoryPath isn't set. 296 std::vector<std::unique_ptr<MemoryBuffer>> ProducedBinaries; 297 298 /// Path to generated files in the supplied SavedObjectsDirectoryPath if any. 299 std::vector<std::string> ProducedBinaryFiles; 300 301 /// Vector holding the input buffers containing the bitcode modules to 302 /// process. 303 std::vector<ThinLTOBuffer> Modules; 304 305 /// Set of symbols that need to be preserved outside of the set of bitcode 306 /// files. 307 StringSet<> PreservedSymbols; 308 309 /// Set of symbols that are cross-referenced between bitcode files. 310 StringSet<> CrossReferencedSymbols; 311 312 /// Control the caching behavior. 313 CachingOptions CacheOptions; 314 315 /// Path to a directory to save the temporary bitcode files. 316 std::string SaveTempsDir; 317 318 /// Path to a directory to save the generated object files. 319 std::string SavedObjectsDirectoryPath; 320 321 /// Flag to enable/disable CodeGen. When set to true, the process stops after 322 /// optimizations and a bitcode is produced. 323 bool DisableCodeGen = false; 324 325 /// Flag to indicate that only the CodeGen will be performed, no cross-module 326 /// importing or optimization. 327 bool CodeGenOnly = false; 328 329 /// Flag to indicate that the optimizer should not assume builtins are present 330 /// on the target. 331 bool Freestanding = false; 332 333 /// IR Optimization Level [0-3]. 334 unsigned OptLevel = 3; 335 }; 336 } 337 #endif 338
