1 //===-LTOCodeGenerator.h - LLVM Link Time Optimizer -----------------------===// 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 // This file declares the LTOCodeGenerator class. 10 // 11 // LTO compilation consists of three phases: Pre-IPO, IPO and Post-IPO. 12 // 13 // The Pre-IPO phase compiles source code into bitcode file. The resulting 14 // bitcode files, along with object files and libraries, will be fed to the 15 // linker to through the IPO and Post-IPO phases. By using obj-file extension, 16 // the resulting bitcode file disguises itself as an object file, and therefore 17 // obviates the need of writing a special set of the make-rules only for LTO 18 // compilation. 19 // 20 // The IPO phase perform inter-procedural analyses and optimizations, and 21 // the Post-IPO consists two sub-phases: intra-procedural scalar optimizations 22 // (SOPT), and intra-procedural target-dependent code generator (CG). 23 // 24 // As of this writing, we don't separate IPO and the Post-IPO SOPT. They 25 // are intermingled together, and are driven by a single pass manager (see 26 // PassManagerBuilder::populateLTOPassManager()). 27 // 28 // The "LTOCodeGenerator" is the driver for the IPO and Post-IPO stages. 29 // The "CodeGenerator" here is bit confusing. Don't confuse the "CodeGenerator" 30 // with the machine specific code generator. 31 // 32 //===----------------------------------------------------------------------===// 33 34 #ifndef LLVM_LTO_LEGACY_LTOCODEGENERATOR_H 35 #define LLVM_LTO_LEGACY_LTOCODEGENERATOR_H 36 37 #include "llvm-c/lto.h" 38 #include "llvm/ADT/ArrayRef.h" 39 #include "llvm/ADT/SmallPtrSet.h" 40 #include "llvm/ADT/StringMap.h" 41 #include "llvm/ADT/StringSet.h" 42 #include "llvm/IR/GlobalValue.h" 43 #include "llvm/IR/Module.h" 44 #include "llvm/LTO/Config.h" 45 #include "llvm/LTO/LTO.h" 46 #include "llvm/Support/CommandLine.h" 47 #include "llvm/Support/Error.h" 48 #include "llvm/Support/ToolOutputFile.h" 49 #include "llvm/Target/TargetMachine.h" 50 #include "llvm/Target/TargetOptions.h" 51 #include <string> 52 #include <vector> 53 54 /// Enable global value internalization in LTO. 55 extern llvm::cl::opt<bool> EnableLTOInternalization; 56 57 namespace llvm { 58 template <typename T> class ArrayRef; 59 class LLVMContext; 60 class DiagnosticInfo; 61 class Linker; 62 class Mangler; 63 class MemoryBuffer; 64 class TargetLibraryInfo; 65 class TargetMachine; 66 class raw_ostream; 67 class raw_pwrite_stream; 68 69 //===----------------------------------------------------------------------===// 70 /// C++ class which implements the opaque lto_code_gen_t type. 71 /// 72 struct LTOCodeGenerator { 73 static const char *getVersionString(); 74 75 LTOCodeGenerator(LLVMContext &Context); 76 ~LTOCodeGenerator(); 77 78 /// Merge given module. Return true on success. 79 /// 80 /// Resets \a HasVerifiedInput. 81 bool addModule(struct LTOModule *); 82 83 /// Set the destination module. 84 /// 85 /// Resets \a HasVerifiedInput. 86 void setModule(std::unique_ptr<LTOModule> M); 87 88 void setAsmUndefinedRefs(struct LTOModule *); 89 void setTargetOptions(const TargetOptions &Options); 90 void setDebugInfo(lto_debug_model); 91 void setCodePICModel(Optional<Reloc::Model> Model) { 92 Config.RelocModel = Model; 93 } 94 95 /// Set the file type to be emitted (assembly or object code). 96 /// The default is CGFT_ObjectFile. 97 void setFileType(CodeGenFileType FT) { Config.CGFileType = FT; } 98 99 void setCpu(StringRef MCpu) { Config.CPU = std::string(MCpu); } 100 void setAttrs(std::vector<std::string> MAttrs) { Config.MAttrs = MAttrs; } 101 void setOptLevel(unsigned OptLevel); 102 103 void setShouldInternalize(bool Value) { ShouldInternalize = Value; } 104 void setShouldEmbedUselists(bool Value) { ShouldEmbedUselists = Value; } 105 106 /// Restore linkage of globals 107 /// 108 /// When set, the linkage of globals will be restored prior to code 109 /// generation. That is, a global symbol that had external linkage prior to 110 /// LTO will be emitted with external linkage again; and a local will remain 111 /// local. Note that this option only affects the end result - globals may 112 /// still be internalized in the process of LTO and may be modified and/or 113 /// deleted where legal. 114 /// 115 /// The default behavior will internalize globals (unless on the preserve 116 /// list) and, if parallel code generation is enabled, will externalize 117 /// all locals. 118 void setShouldRestoreGlobalsLinkage(bool Value) { 119 ShouldRestoreGlobalsLinkage = Value; 120 } 121 122 void addMustPreserveSymbol(StringRef Sym) { MustPreserveSymbols.insert(Sym); } 123 124 /// Pass options to the driver and optimization passes. 125 /// 126 /// These options are not necessarily for debugging purpose (the function 127 /// name is misleading). This function should be called before 128 /// LTOCodeGenerator::compilexxx(), and 129 /// LTOCodeGenerator::writeMergedModules(). 130 void setCodeGenDebugOptions(ArrayRef<StringRef> Opts); 131 132 /// Parse the options set in setCodeGenDebugOptions. 133 /// 134 /// Like \a setCodeGenDebugOptions(), this must be called before 135 /// LTOCodeGenerator::compilexxx() and 136 /// LTOCodeGenerator::writeMergedModules(). 137 void parseCodeGenDebugOptions(); 138 139 /// Write the merged module to the file specified by the given path. Return 140 /// true on success. 141 /// 142 /// Calls \a verifyMergedModuleOnce(). 143 bool writeMergedModules(StringRef Path); 144 145 /// Compile the merged module into a *single* output file; the path to output 146 /// file is returned to the caller via argument "name". Return true on 147 /// success. 148 /// 149 /// \note It is up to the linker to remove the intermediate output file. Do 150 /// not try to remove the object file in LTOCodeGenerator's destructor as we 151 /// don't who (LTOCodeGenerator or the output file) will last longer. 152 bool compile_to_file(const char **Name); 153 154 /// As with compile_to_file(), this function compiles the merged module into 155 /// single output file. Instead of returning the output file path to the 156 /// caller (linker), it brings the output to a buffer, and returns the buffer 157 /// to the caller. This function should delete the intermediate file once 158 /// its content is brought to memory. Return NULL if the compilation was not 159 /// successful. 160 std::unique_ptr<MemoryBuffer> compile(); 161 162 /// Optimizes the merged module. Returns true on success. 163 /// 164 /// Calls \a verifyMergedModuleOnce(). 165 bool optimize(); 166 167 /// Compiles the merged optimized module into a single output file. It brings 168 /// the output to a buffer, and returns the buffer to the caller. Return NULL 169 /// if the compilation was not successful. 170 std::unique_ptr<MemoryBuffer> compileOptimized(); 171 172 /// Compile the merged optimized module \p ParallelismLevel output files each 173 /// representing a linkable partition of the module. If out contains more 174 /// than one element, code generation is done in parallel with \p 175 /// ParallelismLevel threads. Output files will be written to the streams 176 /// created using the \p AddStream callback. Returns true on success. 177 /// 178 /// Calls \a verifyMergedModuleOnce(). 179 bool compileOptimized(lto::AddStreamFn AddStream, unsigned ParallelismLevel); 180 181 /// Enable the Freestanding mode: indicate that the optimizer should not 182 /// assume builtins are present on the target. 183 void setFreestanding(bool Enabled) { Config.Freestanding = Enabled; } 184 185 void setDisableVerify(bool Value) { Config.DisableVerify = Value; } 186 187 void setUseNewPM(bool Value) { Config.UseNewPM = Value; } 188 189 void setDiagnosticHandler(lto_diagnostic_handler_t, void *); 190 191 LLVMContext &getContext() { return Context; } 192 193 void resetMergedModule() { MergedModule.reset(); } 194 void DiagnosticHandler(const DiagnosticInfo &DI); 195 196 private: 197 /// Verify the merged module on first call. 198 /// 199 /// Sets \a HasVerifiedInput on first call and doesn't run again on the same 200 /// input. 201 void verifyMergedModuleOnce(); 202 203 bool compileOptimizedToFile(const char **Name); 204 void restoreLinkageForExternals(); 205 void applyScopeRestrictions(); 206 void preserveDiscardableGVs( 207 Module &TheModule, 208 llvm::function_ref<bool(const GlobalValue &)> mustPreserveGV); 209 210 bool determineTarget(); 211 std::unique_ptr<TargetMachine> createTargetMachine(); 212 213 void emitError(const std::string &ErrMsg); 214 void emitWarning(const std::string &ErrMsg); 215 216 void finishOptimizationRemarks(); 217 218 LLVMContext &Context; 219 std::unique_ptr<Module> MergedModule; 220 std::unique_ptr<Linker> TheLinker; 221 std::unique_ptr<TargetMachine> TargetMach; 222 bool EmitDwarfDebugInfo = false; 223 bool ScopeRestrictionsDone = false; 224 bool HasVerifiedInput = false; 225 StringSet<> MustPreserveSymbols; 226 StringSet<> AsmUndefinedRefs; 227 StringMap<GlobalValue::LinkageTypes> ExternalSymbols; 228 std::vector<std::string> CodegenOptions; 229 std::string FeatureStr; 230 std::string NativeObjectPath; 231 const Target *MArch = nullptr; 232 std::string TripleStr; 233 lto_diagnostic_handler_t DiagHandler = nullptr; 234 void *DiagContext = nullptr; 235 bool ShouldInternalize = EnableLTOInternalization; 236 bool ShouldEmbedUselists = false; 237 bool ShouldRestoreGlobalsLinkage = false; 238 std::unique_ptr<ToolOutputFile> DiagnosticOutputFile; 239 std::unique_ptr<ToolOutputFile> StatsFile = nullptr; 240 241 lto::Config Config; 242 }; 243 244 /// A convenience function that calls cl::ParseCommandLineOptions on the given 245 /// set of options. 246 void parseCommandLineOptions(std::vector<std::string> &Options); 247 } 248 #endif 249