1 //===-LTOCodeGenerator.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 LTOCodeGenerator class.
11 //
12 //   LTO compilation consists of three phases: Pre-IPO, IPO and Post-IPO.
13 //
14 //   The Pre-IPO phase compiles source code into bitcode file. The resulting
15 // bitcode files, along with object files and libraries, will be fed to the
16 // linker to through the IPO and Post-IPO phases. By using obj-file extension,
17 // the resulting bitcode file disguises itself as an object file, and therefore
18 // obviates the need of writing a special set of the make-rules only for LTO
19 // compilation.
20 //
21 //   The IPO phase perform inter-procedural analyses and optimizations, and
22 // the Post-IPO consists two sub-phases: intra-procedural scalar optimizations
23 // (SOPT), and intra-procedural target-dependent code generator (CG).
24 //
25 //   As of this writing, we don't separate IPO and the Post-IPO SOPT. They
26 // are intermingled together, and are driven by a single pass manager (see
27 // PassManagerBuilder::populateLTOPassManager()).
28 //
29 //   The "LTOCodeGenerator" is the driver for the IPO and Post-IPO stages.
30 // The "CodeGenerator" here is bit confusing. Don't confuse the "CodeGenerator"
31 // with the machine specific code generator.
32 //
33 //===----------------------------------------------------------------------===//
34 
35 #ifndef LLVM_LTO_LTOCODEGENERATOR_H
36 #define LLVM_LTO_LTOCODEGENERATOR_H
37 
38 #include "llvm-c/lto.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/Target/TargetMachine.h"
45 #include "llvm/Target/TargetOptions.h"
46 #include <string>
47 #include <vector>
48 
49 namespace llvm {
50 template <typename T> class ArrayRef;
51   class LLVMContext;
52   class DiagnosticInfo;
53   class Linker;
54   class Mangler;
55   class MemoryBuffer;
56   class TargetLibraryInfo;
57   class TargetMachine;
58   class raw_ostream;
59   class raw_pwrite_stream;
60 
61 //===----------------------------------------------------------------------===//
62 /// C++ class which implements the opaque lto_code_gen_t type.
63 ///
64 struct LTOCodeGenerator {
65   static const char *getVersionString();
66 
67   LTOCodeGenerator(LLVMContext &Context);
68   ~LTOCodeGenerator();
69 
70   /// Merge given module.  Return true on success.
71   ///
72   /// Resets \a HasVerifiedInput.
73   bool addModule(struct LTOModule *);
74 
75   /// Set the destination module.
76   ///
77   /// Resets \a HasVerifiedInput.
78   void setModule(std::unique_ptr<LTOModule> M);
79 
80   void setTargetOptions(const TargetOptions &Options);
81   void setDebugInfo(lto_debug_model);
setCodePICModelLTOCodeGenerator82   void setCodePICModel(Optional<Reloc::Model> Model) { RelocModel = Model; }
83 
84   /// Set the file type to be emitted (assembly or object code).
85   /// The default is TargetMachine::CGFT_ObjectFile.
setFileTypeLTOCodeGenerator86   void setFileType(TargetMachine::CodeGenFileType FT) { FileType = FT; }
87 
setCpuLTOCodeGenerator88   void setCpu(const char *MCpu) { this->MCpu = MCpu; }
setAttrLTOCodeGenerator89   void setAttr(const char *MAttr) { this->MAttr = MAttr; }
90   void setOptLevel(unsigned OptLevel);
91 
setShouldInternalizeLTOCodeGenerator92   void setShouldInternalize(bool Value) { ShouldInternalize = Value; }
setShouldEmbedUselistsLTOCodeGenerator93   void setShouldEmbedUselists(bool Value) { ShouldEmbedUselists = Value; }
94 
95   /// Restore linkage of globals
96   ///
97   /// When set, the linkage of globals will be restored prior to code
98   /// generation. That is, a global symbol that had external linkage prior to
99   /// LTO will be emitted with external linkage again; and a local will remain
100   /// local. Note that this option only affects the end result - globals may
101   /// still be internalized in the process of LTO and may be modified and/or
102   /// deleted where legal.
103   ///
104   /// The default behavior will internalize globals (unless on the preserve
105   /// list) and, if parallel code generation is enabled, will externalize
106   /// all locals.
setShouldRestoreGlobalsLinkageLTOCodeGenerator107   void setShouldRestoreGlobalsLinkage(bool Value) {
108     ShouldRestoreGlobalsLinkage = Value;
109   }
110 
addMustPreserveSymbolLTOCodeGenerator111   void addMustPreserveSymbol(StringRef Sym) { MustPreserveSymbols[Sym] = 1; }
112 
113   /// Pass options to the driver and optimization passes.
114   ///
115   /// These options are not necessarily for debugging purpose (the function
116   /// name is misleading).  This function should be called before
117   /// LTOCodeGenerator::compilexxx(), and
118   /// LTOCodeGenerator::writeMergedModules().
119   void setCodeGenDebugOptions(const char *Opts);
120 
121   /// Parse the options set in setCodeGenDebugOptions.
122   ///
123   /// Like \a setCodeGenDebugOptions(), this must be called before
124   /// LTOCodeGenerator::compilexxx() and
125   /// LTOCodeGenerator::writeMergedModules().
126   void parseCodeGenDebugOptions();
127 
128   /// Write the merged module to the file specified by the given path.  Return
129   /// true on success.
130   ///
131   /// Calls \a verifyMergedModuleOnce().
132   bool writeMergedModules(const char *Path);
133 
134   /// Compile the merged module into a *single* output file; the path to output
135   /// file is returned to the caller via argument "name". Return true on
136   /// success.
137   ///
138   /// \note It is up to the linker to remove the intermediate output file.  Do
139   /// not try to remove the object file in LTOCodeGenerator's destructor as we
140   /// don't who (LTOCodeGenerator or the output file) will last longer.
141   bool compile_to_file(const char **Name, bool DisableVerify,
142                        bool DisableInline, bool DisableGVNLoadPRE,
143                        bool DisableVectorization);
144 
145   /// As with compile_to_file(), this function compiles the merged module into
146   /// single output file. Instead of returning the output file path to the
147   /// caller (linker), it brings the output to a buffer, and returns the buffer
148   /// to the caller. This function should delete the intermediate file once
149   /// its content is brought to memory. Return NULL if the compilation was not
150   /// successful.
151   std::unique_ptr<MemoryBuffer> compile(bool DisableVerify, bool DisableInline,
152                                         bool DisableGVNLoadPRE,
153                                         bool DisableVectorization);
154 
155   /// Optimizes the merged module.  Returns true on success.
156   ///
157   /// Calls \a verifyMergedModuleOnce().
158   bool optimize(bool DisableVerify, bool DisableInline, bool DisableGVNLoadPRE,
159                 bool DisableVectorization);
160 
161   /// Compiles the merged optimized module into a single output file. It brings
162   /// the output to a buffer, and returns the buffer to the caller. Return NULL
163   /// if the compilation was not successful.
164   std::unique_ptr<MemoryBuffer> compileOptimized();
165 
166   /// Compile the merged optimized module into out.size() output files each
167   /// representing a linkable partition of the module. If out contains more
168   /// than one element, code generation is done in parallel with out.size()
169   /// threads.  Output files will be written to members of out. Returns true on
170   /// success.
171   ///
172   /// Calls \a verifyMergedModuleOnce().
173   bool compileOptimized(ArrayRef<raw_pwrite_stream *> Out);
174 
175   void setDiagnosticHandler(lto_diagnostic_handler_t, void *);
176 
getContextLTOCodeGenerator177   LLVMContext &getContext() { return Context; }
178 
resetMergedModuleLTOCodeGenerator179   void resetMergedModule() { MergedModule.reset(); }
180 
181 private:
182   void initializeLTOPasses();
183 
184   /// Verify the merged module on first call.
185   ///
186   /// Sets \a HasVerifiedInput on first call and doesn't run again on the same
187   /// input.
188   void verifyMergedModuleOnce();
189 
190   bool compileOptimizedToFile(const char **Name);
191   void restoreLinkageForExternals();
192   void applyScopeRestrictions();
193   void preserveDiscardableGVs(
194       Module &TheModule,
195       llvm::function_ref<bool(const GlobalValue &)> mustPreserveGV);
196 
197   bool determineTarget();
198   std::unique_ptr<TargetMachine> createTargetMachine();
199 
200   static void DiagnosticHandler(const DiagnosticInfo &DI, void *Context);
201 
202   void DiagnosticHandler2(const DiagnosticInfo &DI);
203 
204   void emitError(const std::string &ErrMsg);
205   void emitWarning(const std::string &ErrMsg);
206 
207   LLVMContext &Context;
208   std::unique_ptr<Module> MergedModule;
209   std::unique_ptr<Linker> TheLinker;
210   std::unique_ptr<TargetMachine> TargetMach;
211   bool EmitDwarfDebugInfo = false;
212   bool ScopeRestrictionsDone = false;
213   bool HasVerifiedInput = false;
214   Optional<Reloc::Model> RelocModel;
215   StringSet<> MustPreserveSymbols;
216   StringSet<> AsmUndefinedRefs;
217   StringMap<GlobalValue::LinkageTypes> ExternalSymbols;
218   std::vector<std::string> CodegenOptions;
219   std::string FeatureStr;
220   std::string MCpu;
221   std::string MAttr;
222   std::string NativeObjectPath;
223   TargetOptions Options;
224   CodeGenOpt::Level CGOptLevel = CodeGenOpt::Default;
225   const Target *MArch = nullptr;
226   std::string TripleStr;
227   unsigned OptLevel = 2;
228   lto_diagnostic_handler_t DiagHandler = nullptr;
229   void *DiagContext = nullptr;
230   bool ShouldInternalize = true;
231   bool ShouldEmbedUselists = false;
232   bool ShouldRestoreGlobalsLinkage = false;
233   TargetMachine::CodeGenFileType FileType = TargetMachine::CGFT_ObjectFile;
234 };
235 }
236 #endif
237