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_LTOCODEGENERATOR_H
35#define LLVM_LTO_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/Support/CommandLine.h"
45#include "llvm/Support/Error.h"
46#include "llvm/Support/ToolOutputFile.h"
47#include "llvm/Target/TargetMachine.h"
48#include "llvm/Target/TargetOptions.h"
49#include <string>
50#include <vector>
51
52/// Enable global value internalization in LTO.
53extern llvm::cl::opt<bool> EnableLTOInternalization;
54
55namespace llvm {
56template <typename T> class ArrayRef;
57  class LLVMContext;
58  class DiagnosticInfo;
59  class Linker;
60  class Mangler;
61  class MemoryBuffer;
62  class TargetLibraryInfo;
63  class TargetMachine;
64  class raw_ostream;
65  class raw_pwrite_stream;
66
67//===----------------------------------------------------------------------===//
68/// C++ class which implements the opaque lto_code_gen_t type.
69///
70struct LTOCodeGenerator {
71  static const char *getVersionString();
72
73  LTOCodeGenerator(LLVMContext &Context);
74  ~LTOCodeGenerator();
75
76  /// Merge given module.  Return true on success.
77  ///
78  /// Resets \a HasVerifiedInput.
79  bool addModule(struct LTOModule *);
80
81  /// Set the destination module.
82  ///
83  /// Resets \a HasVerifiedInput.
84  void setModule(std::unique_ptr<LTOModule> M);
85
86  void setAsmUndefinedRefs(struct LTOModule *);
87  void setTargetOptions(const TargetOptions &Options);
88  void setDebugInfo(lto_debug_model);
89  void setCodePICModel(Optional<Reloc::Model> Model) { RelocModel = Model; }
90
91  /// Set the file type to be emitted (assembly or object code).
92  /// The default is CGFT_ObjectFile.
93  void setFileType(CodeGenFileType FT) { FileType = FT; }
94
95  void setCpu(StringRef MCpu) { this->MCpu = MCpu; }
96  void setAttr(StringRef MAttr) { this->MAttr = MAttr; }
97  void setOptLevel(unsigned OptLevel);
98
99  void setShouldInternalize(bool Value) { ShouldInternalize = Value; }
100  void setShouldEmbedUselists(bool Value) { ShouldEmbedUselists = Value; }
101
102  /// Restore linkage of globals
103  ///
104  /// When set, the linkage of globals will be restored prior to code
105  /// generation. That is, a global symbol that had external linkage prior to
106  /// LTO will be emitted with external linkage again; and a local will remain
107  /// local. Note that this option only affects the end result - globals may
108  /// still be internalized in the process of LTO and may be modified and/or
109  /// deleted where legal.
110  ///
111  /// The default behavior will internalize globals (unless on the preserve
112  /// list) and, if parallel code generation is enabled, will externalize
113  /// all locals.
114  void setShouldRestoreGlobalsLinkage(bool Value) {
115    ShouldRestoreGlobalsLinkage = Value;
116  }
117
118  void addMustPreserveSymbol(StringRef Sym) { MustPreserveSymbols.insert(Sym); }
119
120  /// Pass options to the driver and optimization passes.
121  ///
122  /// These options are not necessarily for debugging purpose (the function
123  /// name is misleading).  This function should be called before
124  /// LTOCodeGenerator::compilexxx(), and
125  /// LTOCodeGenerator::writeMergedModules().
126  void setCodeGenDebugOptions(ArrayRef<const char *> Opts);
127
128  /// Parse the options set in setCodeGenDebugOptions.
129  ///
130  /// Like \a setCodeGenDebugOptions(), this must be called before
131  /// LTOCodeGenerator::compilexxx() and
132  /// LTOCodeGenerator::writeMergedModules().
133  void parseCodeGenDebugOptions();
134
135  /// Write the merged module to the file specified by the given path.  Return
136  /// true on success.
137  ///
138  /// Calls \a verifyMergedModuleOnce().
139  bool writeMergedModules(StringRef Path);
140
141  /// Compile the merged module into a *single* output file; the path to output
142  /// file is returned to the caller via argument "name". Return true on
143  /// success.
144  ///
145  /// \note It is up to the linker to remove the intermediate output file.  Do
146  /// not try to remove the object file in LTOCodeGenerator's destructor as we
147  /// don't who (LTOCodeGenerator or the output file) will last longer.
148  bool compile_to_file(const char **Name, bool DisableVerify,
149                       bool DisableInline, bool DisableGVNLoadPRE,
150                       bool DisableVectorization);
151
152  /// As with compile_to_file(), this function compiles the merged module into
153  /// single output file. Instead of returning the output file path to the
154  /// caller (linker), it brings the output to a buffer, and returns the buffer
155  /// to the caller. This function should delete the intermediate file once
156  /// its content is brought to memory. Return NULL if the compilation was not
157  /// successful.
158  std::unique_ptr<MemoryBuffer> compile(bool DisableVerify, bool DisableInline,
159                                        bool DisableGVNLoadPRE,
160                                        bool DisableVectorization);
161
162  /// Optimizes the merged module.  Returns true on success.
163  ///
164  /// Calls \a verifyMergedModuleOnce().
165  bool optimize(bool DisableVerify, bool DisableInline, bool DisableGVNLoadPRE,
166                bool DisableVectorization);
167
168  /// Compiles the merged optimized module into a single output file. It brings
169  /// the output to a buffer, and returns the buffer to the caller. Return NULL
170  /// if the compilation was not successful.
171  std::unique_ptr<MemoryBuffer> compileOptimized();
172
173  /// Compile the merged optimized module into out.size() output files each
174  /// representing a linkable partition of the module. If out contains more
175  /// than one element, code generation is done in parallel with out.size()
176  /// threads.  Output files will be written to members of out. Returns true on
177  /// success.
178  ///
179  /// Calls \a verifyMergedModuleOnce().
180  bool compileOptimized(ArrayRef<raw_pwrite_stream *> Out);
181
182  /// Enable the Freestanding mode: indicate that the optimizer should not
183  /// assume builtins are present on the target.
184  void setFreestanding(bool Enabled) { Freestanding = Enabled; }
185
186  void setDiagnosticHandler(lto_diagnostic_handler_t, void *);
187
188  LLVMContext &getContext() { return Context; }
189
190  void resetMergedModule() { MergedModule.reset(); }
191  void DiagnosticHandler(const DiagnosticInfo &DI);
192
193private:
194  void initializeLTOPasses();
195
196  /// Verify the merged module on first call.
197  ///
198  /// Sets \a HasVerifiedInput on first call and doesn't run again on the same
199  /// input.
200  void verifyMergedModuleOnce();
201
202  bool compileOptimizedToFile(const char **Name);
203  void restoreLinkageForExternals();
204  void applyScopeRestrictions();
205  void preserveDiscardableGVs(
206      Module &TheModule,
207      llvm::function_ref<bool(const GlobalValue &)> mustPreserveGV);
208
209  bool determineTarget();
210  std::unique_ptr<TargetMachine> createTargetMachine();
211
212  void emitError(const std::string &ErrMsg);
213  void emitWarning(const std::string &ErrMsg);
214
215  void finishOptimizationRemarks();
216
217  LLVMContext &Context;
218  std::unique_ptr<Module> MergedModule;
219  std::unique_ptr<Linker> TheLinker;
220  std::unique_ptr<TargetMachine> TargetMach;
221  bool EmitDwarfDebugInfo = false;
222  bool ScopeRestrictionsDone = false;
223  bool HasVerifiedInput = false;
224  Optional<Reloc::Model> RelocModel;
225  StringSet<> MustPreserveSymbols;
226  StringSet<> AsmUndefinedRefs;
227  StringMap<GlobalValue::LinkageTypes> ExternalSymbols;
228  std::vector<std::string> CodegenOptions;
229  std::string FeatureStr;
230  std::string MCpu;
231  std::string MAttr;
232  std::string NativeObjectPath;
233  TargetOptions Options;
234  CodeGenOpt::Level CGOptLevel = CodeGenOpt::Default;
235  const Target *MArch = nullptr;
236  std::string TripleStr;
237  unsigned OptLevel = 2;
238  lto_diagnostic_handler_t DiagHandler = nullptr;
239  void *DiagContext = nullptr;
240  bool ShouldInternalize = EnableLTOInternalization;
241  bool ShouldEmbedUselists = false;
242  bool ShouldRestoreGlobalsLinkage = false;
243  CodeGenFileType FileType = CGFT_ObjectFile;
244  std::unique_ptr<ToolOutputFile> DiagnosticOutputFile;
245  bool Freestanding = false;
246  std::unique_ptr<ToolOutputFile> StatsFile = nullptr;
247};
248}
249#endif
250