1 //===-- llvm/FunctionInfo.h - Function Info Index ---------------*- C++ -*-===//
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 /// @file
11 /// FunctionInfo.h This file contains the declarations the classes that hold
12 ///  the function info index and summary.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_IR_FUNCTIONINFO_H
17 #define LLVM_IR_FUNCTIONINFO_H
18 
19 #include "llvm/ADT/SmallString.h"
20 #include "llvm/ADT/StringMap.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/Support/MemoryBuffer.h"
23 #include "llvm/Support/raw_ostream.h"
24 
25 namespace llvm {
26 
27 /// \brief Function summary information to aid decisions and implementation of
28 /// importing.
29 ///
30 /// This is a separate class from FunctionInfo to enable lazy reading of this
31 /// function summary information from the combined index file during imporing.
32 class FunctionSummary {
33 private:
34   /// \brief Path of module containing function IR, used to locate module when
35   /// importing this function.
36   ///
37   /// This is only used during parsing of the combined function index, or when
38   /// parsing the per-module index for creation of the combined function index,
39   /// not during writing of the per-module index which doesn't contain a
40   /// module path string table.
41   StringRef ModulePath;
42 
43   /// \brief Used to flag functions that have local linkage types and need to
44   /// have module identifier appended before placing into the combined
45   /// index, to disambiguate from other functions with the same name.
46   ///
47   /// This is only used in the per-module function index, as it is consumed
48   /// while creating the combined index.
49   bool IsLocalFunction;
50 
51   // The rest of the information is used to help decide whether importing
52   // is likely to be profitable.
53   // Other information will be added as the importing is tuned, such
54   // as hotness (when profile available), and other function characteristics.
55 
56   /// Number of instructions (ignoring debug instructions, e.g.) computed
57   /// during the initial compile step when the function index is first built.
58   unsigned InstCount;
59 
60 public:
61   /// Construct a summary object from summary data expected for all
62   /// summary records.
FunctionSummary(unsigned NumInsts)63   FunctionSummary(unsigned NumInsts) : InstCount(NumInsts) {}
64 
65   /// Set the path to the module containing this function, for use in
66   /// the combined index.
setModulePath(StringRef ModPath)67   void setModulePath(StringRef ModPath) { ModulePath = ModPath; }
68 
69   /// Get the path to the module containing this function.
modulePath()70   StringRef modulePath() const { return ModulePath; }
71 
72   /// Record whether this is a local function in the per-module index.
setLocalFunction(bool IsLocal)73   void setLocalFunction(bool IsLocal) { IsLocalFunction = IsLocal; }
74 
75   /// Check whether this was a local function, for use in creating
76   /// the combined index.
isLocalFunction()77   bool isLocalFunction() const { return IsLocalFunction; }
78 
79   /// Get the instruction count recorded for this function.
instCount()80   unsigned instCount() const { return InstCount; }
81 };
82 
83 /// \brief Class to hold pointer to function summary and information required
84 /// for parsing it.
85 ///
86 /// For the per-module index, this holds the bitcode offset
87 /// of the corresponding function block. For the combined index,
88 /// after parsing of the \a ValueSymbolTable, this initially
89 /// holds the offset of the corresponding function summary bitcode
90 /// record. After parsing the associated summary information from the summary
91 /// block the \a FunctionSummary is populated and stored here.
92 class FunctionInfo {
93 private:
94   /// Function summary information used to help make ThinLTO importing
95   /// decisions.
96   std::unique_ptr<FunctionSummary> Summary;
97 
98   /// \brief The bitcode offset corresponding to either the associated
99   /// function's function body record, or its function summary record,
100   /// depending on whether this is a per-module or combined index.
101   ///
102   /// This bitcode offset is written to or read from the associated
103   /// \a ValueSymbolTable entry for the function.
104   /// For the per-module index this holds the bitcode offset of the
105   /// function's body record  within bitcode module block in its module,
106   /// which is used during lazy function parsing or ThinLTO importing.
107   /// For the combined index this holds the offset of the corresponding
108   /// function summary record, to enable associating the combined index
109   /// VST records with the summary records.
110   uint64_t BitcodeIndex;
111 
112 public:
113   /// Constructor used during parsing of VST entries.
FunctionInfo(uint64_t FuncOffset)114   FunctionInfo(uint64_t FuncOffset)
115       : Summary(nullptr), BitcodeIndex(FuncOffset) {}
116 
117   /// Constructor used for per-module index bitcode writing.
FunctionInfo(uint64_t FuncOffset,std::unique_ptr<FunctionSummary> FuncSummary)118   FunctionInfo(uint64_t FuncOffset,
119                std::unique_ptr<FunctionSummary> FuncSummary)
120       : Summary(std::move(FuncSummary)), BitcodeIndex(FuncOffset) {}
121 
122   /// Record the function summary information parsed out of the function
123   /// summary block during parsing or combined index creation.
setFunctionSummary(std::unique_ptr<FunctionSummary> FuncSummary)124   void setFunctionSummary(std::unique_ptr<FunctionSummary> FuncSummary) {
125     Summary = std::move(FuncSummary);
126   }
127 
128   /// Get the function summary recorded for this function.
functionSummary()129   FunctionSummary *functionSummary() const { return Summary.get(); }
130 
131   /// Get the bitcode index recorded for this function, depending on
132   /// the index type.
bitcodeIndex()133   uint64_t bitcodeIndex() const { return BitcodeIndex; }
134 
135   /// Record the bitcode index for this function, depending on
136   /// the index type.
setBitcodeIndex(uint64_t FuncOffset)137   void setBitcodeIndex(uint64_t FuncOffset) { BitcodeIndex = FuncOffset; }
138 };
139 
140 /// List of function info structures for a particular function name held
141 /// in the FunctionMap. Requires a vector in the case of multiple
142 /// COMDAT functions of the same name.
143 typedef std::vector<std::unique_ptr<FunctionInfo>> FunctionInfoList;
144 
145 /// Map from function name to corresponding function info structures.
146 typedef StringMap<FunctionInfoList> FunctionInfoMapTy;
147 
148 /// Type used for iterating through the function info map.
149 typedef FunctionInfoMapTy::const_iterator const_funcinfo_iterator;
150 typedef FunctionInfoMapTy::iterator funcinfo_iterator;
151 
152 /// String table to hold/own module path strings, which additionally holds the
153 /// module ID assigned to each module during the plugin step. The StringMap
154 /// makes a copy of and owns inserted strings.
155 typedef StringMap<uint64_t> ModulePathStringTableTy;
156 
157 /// Class to hold module path string table and function map,
158 /// and encapsulate methods for operating on them.
159 class FunctionInfoIndex {
160 private:
161   /// Map from function name to list of function information instances
162   /// for functions of that name (may be duplicates in the COMDAT case, e.g.).
163   FunctionInfoMapTy FunctionMap;
164 
165   /// Holds strings for combined index, mapping to the corresponding module ID.
166   ModulePathStringTableTy ModulePathStringTable;
167 
168 public:
169   FunctionInfoIndex() = default;
170 
171   // Disable the copy constructor and assignment operators, so
172   // no unexpected copying/moving occurs.
173   FunctionInfoIndex(const FunctionInfoIndex &) = delete;
174   void operator=(const FunctionInfoIndex &) = delete;
175 
begin()176   funcinfo_iterator begin() { return FunctionMap.begin(); }
begin()177   const_funcinfo_iterator begin() const { return FunctionMap.begin(); }
end()178   funcinfo_iterator end() { return FunctionMap.end(); }
end()179   const_funcinfo_iterator end() const { return FunctionMap.end(); }
180 
181   /// Get the list of function info objects for a given function.
getFunctionInfoList(StringRef FuncName)182   const FunctionInfoList &getFunctionInfoList(StringRef FuncName) {
183     return FunctionMap[FuncName];
184   }
185 
186   /// Get the list of function info objects for a given function.
findFunctionInfoList(StringRef FuncName)187   const const_funcinfo_iterator findFunctionInfoList(StringRef FuncName) const {
188     return FunctionMap.find(FuncName);
189   }
190 
191   /// Add a function info for a function of the given name.
addFunctionInfo(StringRef FuncName,std::unique_ptr<FunctionInfo> Info)192   void addFunctionInfo(StringRef FuncName, std::unique_ptr<FunctionInfo> Info) {
193     FunctionMap[FuncName].push_back(std::move(Info));
194   }
195 
196   /// Iterator to allow writer to walk through table during emission.
197   iterator_range<StringMap<uint64_t>::const_iterator>
modPathStringEntries()198   modPathStringEntries() const {
199     return llvm::make_range(ModulePathStringTable.begin(),
200                             ModulePathStringTable.end());
201   }
202 
203   /// Get the module ID recorded for the given module path.
getModuleId(const StringRef ModPath)204   uint64_t getModuleId(const StringRef ModPath) const {
205     return ModulePathStringTable.lookup(ModPath);
206   }
207 
208   /// Add the given per-module index into this function index/summary,
209   /// assigning it the given module ID. Each module merged in should have
210   /// a unique ID, necessary for consistent renaming of promoted
211   /// static (local) variables.
212   void mergeFrom(std::unique_ptr<FunctionInfoIndex> Other,
213                  uint64_t NextModuleId);
214 
215   /// Convenience method for creating a promoted global name
216   /// for the given value name of a local, and its original module's ID.
getGlobalNameForLocal(StringRef Name,uint64_t ModId)217   static std::string getGlobalNameForLocal(StringRef Name, uint64_t ModId) {
218     SmallString<256> NewName(Name);
219     NewName += ".llvm.";
220     raw_svector_ostream(NewName) << ModId;
221     return NewName.str();
222   }
223 
224   /// Add a new module path, mapped to the given module Id, and return StringRef
225   /// owned by string table map.
addModulePath(StringRef ModPath,uint64_t ModId)226   StringRef addModulePath(StringRef ModPath, uint64_t ModId) {
227     return ModulePathStringTable.insert(std::make_pair(ModPath, ModId))
228         .first->first();
229   }
230 
231   /// Check if the given Module has any functions available for exporting
232   /// in the index. We consider any module present in the ModulePathStringTable
233   /// to have exported functions.
hasExportedFunctions(const Module & M)234   bool hasExportedFunctions(const Module &M) const {
235     return ModulePathStringTable.count(M.getModuleIdentifier());
236   }
237 };
238 
239 } // End llvm namespace
240 
241 #endif
242