LLVM API Documentation
00001 //===-- Reader.h - Interface To Bytecode Reading ----------------*- C++ -*-===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by Reid Spencer and is distributed under the 00006 // University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This header file defines the interface to the Bytecode Reader which is 00011 // responsible for correctly interpreting bytecode files (backwards compatible) 00012 // and materializing a module from the bytecode read. 00013 // 00014 //===----------------------------------------------------------------------===// 00015 00016 #ifndef BYTECODE_PARSER_H 00017 #define BYTECODE_PARSER_H 00018 00019 #include "llvm/Constants.h" 00020 #include "llvm/DerivedTypes.h" 00021 #include "llvm/GlobalValue.h" 00022 #include "llvm/Function.h" 00023 #include "llvm/ModuleProvider.h" 00024 #include "llvm/Bytecode/Analyzer.h" 00025 #include <utility> 00026 #include <map> 00027 00028 namespace llvm { 00029 00030 class BytecodeHandler; ///< Forward declare the handler interface 00031 00032 /// This class defines the interface for parsing a buffer of bytecode. The 00033 /// parser itself takes no action except to call the various functions of 00034 /// the handler interface. The parser's sole responsibility is the correct 00035 /// interpretation of the bytecode buffer. The handler is responsible for 00036 /// instantiating and keeping track of all values. As a convenience, the parser 00037 /// is responsible for materializing types and will pass them through the 00038 /// handler interface as necessary. 00039 /// @see BytecodeHandler 00040 /// @brief Bytecode Reader interface 00041 class BytecodeReader : public ModuleProvider { 00042 00043 /// @name Constructors 00044 /// @{ 00045 public: 00046 /// @brief Default constructor. By default, no handler is used. 00047 BytecodeReader(BytecodeHandler* h = 0) { 00048 decompressedBlock = 0; 00049 Handler = h; 00050 } 00051 00052 ~BytecodeReader() { 00053 freeState(); 00054 if (decompressedBlock) { 00055 ::free(decompressedBlock); 00056 decompressedBlock = 0; 00057 } 00058 } 00059 00060 /// @} 00061 /// @name Types 00062 /// @{ 00063 public: 00064 00065 /// @brief A convenience type for the buffer pointer 00066 typedef const unsigned char* BufPtr; 00067 00068 /// @brief The type used for a vector of potentially abstract types 00069 typedef std::vector<PATypeHolder> TypeListTy; 00070 00071 /// This type provides a vector of Value* via the User class for 00072 /// storage of Values that have been constructed when reading the 00073 /// bytecode. Because of forward referencing, constant replacement 00074 /// can occur so we ensure that our list of Value* is updated 00075 /// properly through those transitions. This ensures that the 00076 /// correct Value* is in our list when it comes time to associate 00077 /// constants with global variables at the end of reading the 00078 /// globals section. 00079 /// @brief A list of values as a User of those Values. 00080 struct ValueList : public User { 00081 ValueList() : User(Type::VoidTy, Value::ValueListVal) {} 00082 00083 // vector compatibility methods 00084 unsigned size() const { return getNumOperands(); } 00085 void push_back(Value *V) { Operands.push_back(Use(V, this)); } 00086 Value *back() const { return Operands.back(); } 00087 void pop_back() { Operands.pop_back(); } 00088 bool empty() const { return Operands.empty(); } 00089 // must override this 00090 virtual void print(std::ostream& os) const { 00091 for ( unsigned i = 0; i < size(); i++ ) { 00092 os << i << " "; 00093 getOperand(i)->print(os); 00094 os << "\n"; 00095 } 00096 } 00097 }; 00098 00099 /// @brief A 2 dimensional table of values 00100 typedef std::vector<ValueList*> ValueTable; 00101 00102 /// This map is needed so that forward references to constants can be looked 00103 /// up by Type and slot number when resolving those references. 00104 /// @brief A mapping of a Type/slot pair to a Constant*. 00105 typedef std::map<std::pair<const Type*,unsigned>, Constant*> ConstantRefsType; 00106 00107 /// For lazy read-in of functions, we need to save the location in the 00108 /// data stream where the function is located. This structure provides that 00109 /// information. Lazy read-in is used mostly by the JIT which only wants to 00110 /// resolve functions as it needs them. 00111 /// @brief Keeps pointers to function contents for later use. 00112 struct LazyFunctionInfo { 00113 const unsigned char *Buf, *EndBuf; 00114 LazyFunctionInfo(const unsigned char *B = 0, const unsigned char *EB = 0) 00115 : Buf(B), EndBuf(EB) {} 00116 }; 00117 00118 /// @brief A mapping of functions to their LazyFunctionInfo for lazy reading. 00119 typedef std::map<Function*, LazyFunctionInfo> LazyFunctionMap; 00120 00121 /// @brief A list of global variables and the slot number that initializes 00122 /// them. 00123 typedef std::vector<std::pair<GlobalVariable*, unsigned> > GlobalInitsList; 00124 00125 /// This type maps a typeslot/valueslot pair to the corresponding Value*. 00126 /// It is used for dealing with forward references as values are read in. 00127 /// @brief A map for dealing with forward references of values. 00128 typedef std::map<std::pair<unsigned,unsigned>,Value*> ForwardReferenceMap; 00129 00130 /// @} 00131 /// @name Methods 00132 /// @{ 00133 public: 00134 /// @brief Main interface to parsing a bytecode buffer. 00135 void ParseBytecode( 00136 const unsigned char *Buf, ///< Beginning of the bytecode buffer 00137 unsigned Length, ///< Length of the bytecode buffer 00138 const std::string &ModuleID ///< An identifier for the module constructed. 00139 ); 00140 00141 /// @brief Parse all function bodies 00142 void ParseAllFunctionBodies(); 00143 00144 /// @brief Parse the next function of specific type 00145 void ParseFunction(Function* Func) ; 00146 00147 /// This method is abstract in the parent ModuleProvider class. Its 00148 /// implementation is identical to the ParseFunction method. 00149 /// @see ParseFunction 00150 /// @brief Make a specific function materialize. 00151 virtual void materializeFunction(Function *F) { 00152 LazyFunctionMap::iterator Fi = LazyFunctionLoadMap.find(F); 00153 if (Fi == LazyFunctionLoadMap.end()) return; 00154 ParseFunction(F); 00155 } 00156 00157 /// This method is abstract in the parent ModuleProvider class. Its 00158 /// implementation is identical to ParseAllFunctionBodies. 00159 /// @see ParseAllFunctionBodies 00160 /// @brief Make the whole module materialize 00161 virtual Module* materializeModule() { 00162 ParseAllFunctionBodies(); 00163 return TheModule; 00164 } 00165 00166 /// This method is provided by the parent ModuleProvde class and overriden 00167 /// here. It simply releases the module from its provided and frees up our 00168 /// state. 00169 /// @brief Release our hold on the generated module 00170 Module* releaseModule() { 00171 // Since we're losing control of this Module, we must hand it back complete 00172 Module *M = ModuleProvider::releaseModule(); 00173 freeState(); 00174 return M; 00175 } 00176 00177 /// @} 00178 /// @name Parsing Units For Subclasses 00179 /// @{ 00180 protected: 00181 /// @brief Parse whole module scope 00182 void ParseModule(); 00183 00184 /// @brief Parse the version information block 00185 void ParseVersionInfo(); 00186 00187 /// @brief Parse the ModuleGlobalInfo block 00188 void ParseModuleGlobalInfo(); 00189 00190 /// @brief Parse a symbol table 00191 void ParseSymbolTable( Function* Func, SymbolTable *ST); 00192 00193 /// @brief Parse functions lazily. 00194 void ParseFunctionLazily(); 00195 00196 /// @brief Parse a function body 00197 void ParseFunctionBody(Function* Func); 00198 00199 /// @brief Parse the type list portion of a compaction table 00200 void ParseCompactionTypes(unsigned NumEntries); 00201 00202 /// @brief Parse a compaction table 00203 void ParseCompactionTable(); 00204 00205 /// @brief Parse global types 00206 void ParseGlobalTypes(); 00207 00208 /// @brief Parse a basic block (for LLVM 1.0 basic block blocks) 00209 BasicBlock* ParseBasicBlock(unsigned BlockNo); 00210 00211 /// @brief parse an instruction list (for post LLVM 1.0 instruction lists 00212 /// with blocks differentiated by terminating instructions. 00213 unsigned ParseInstructionList( 00214 Function* F ///< The function into which BBs will be inserted 00215 ); 00216 00217 /// @brief Parse a single instruction. 00218 void ParseInstruction( 00219 std::vector<unsigned>& Args, ///< The arguments to be filled in 00220 BasicBlock* BB ///< The BB the instruction goes in 00221 ); 00222 00223 /// @brief Parse the whole constant pool 00224 void ParseConstantPool(ValueTable& Values, TypeListTy& Types, 00225 bool isFunction); 00226 00227 /// @brief Parse a single constant value 00228 Constant* ParseConstantValue(unsigned TypeID); 00229 00230 /// @brief Parse a block of types constants 00231 void ParseTypes(TypeListTy &Tab, unsigned NumEntries); 00232 00233 /// @brief Parse a single type constant 00234 const Type *ParseType(); 00235 00236 /// @brief Parse a string constants block 00237 void ParseStringConstants(unsigned NumEntries, ValueTable &Tab); 00238 00239 /// @} 00240 /// @name Data 00241 /// @{ 00242 private: 00243 char* decompressedBlock; ///< Result of decompression 00244 BufPtr MemStart; ///< Start of the memory buffer 00245 BufPtr MemEnd; ///< End of the memory buffer 00246 BufPtr BlockStart; ///< Start of current block being parsed 00247 BufPtr BlockEnd; ///< End of current block being parsed 00248 BufPtr At; ///< Where we're currently parsing at 00249 00250 /// Information about the module, extracted from the bytecode revision number. 00251 /// 00252 unsigned char RevisionNum; // The rev # itself 00253 00254 /// Flags to distinguish LLVM 1.0 & 1.1 bytecode formats (revision #0) 00255 00256 /// Revision #0 had an explicit alignment of data only for the 00257 /// ModuleGlobalInfo block. This was fixed to be like all other blocks in 1.2 00258 bool hasInconsistentModuleGlobalInfo; 00259 00260 /// Revision #0 also explicitly encoded zero values for primitive types like 00261 /// int/sbyte/etc. 00262 bool hasExplicitPrimitiveZeros; 00263 00264 // Flags to control features specific the LLVM 1.2 and before (revision #1) 00265 00266 /// LLVM 1.2 and earlier required that getelementptr structure indices were 00267 /// ubyte constants and that sequential type indices were longs. 00268 bool hasRestrictedGEPTypes; 00269 00270 /// LLVM 1.2 and earlier had class Type deriving from Value and the Type 00271 /// objects were located in the "Type Type" plane of various lists in read 00272 /// by the bytecode reader. In LLVM 1.3 this is no longer the case. Types are 00273 /// completely distinct from Values. Consequently, Types are written in fixed 00274 /// locations in LLVM 1.3. This flag indicates that the older Type derived 00275 /// from Value style of bytecode file is being read. 00276 bool hasTypeDerivedFromValue; 00277 00278 /// LLVM 1.2 and earlier encoded block headers as two uint (8 bytes), one for 00279 /// the size and one for the type. This is a bit wasteful, especially for 00280 /// small files where the 8 bytes per block is a large fraction of the total 00281 /// block size. In LLVM 1.3, the block type and length are encoded into a 00282 /// single uint32 by restricting the number of block types (limit 31) and the 00283 /// maximum size of a block (limit 2^27-1=134,217,727). Note that the module 00284 /// block still uses the 8-byte format so the maximum size of a file can be 00285 /// 2^32-1 bytes long. 00286 bool hasLongBlockHeaders; 00287 00288 /// LLVM 1.2 and earlier wrote type slot numbers as vbr_uint32. In LLVM 1.3 00289 /// this has been reduced to vbr_uint24. It shouldn't make much difference 00290 /// since we haven't run into a module with > 24 million types, but for safety 00291 /// the 24-bit restriction has been enforced in 1.3 to free some bits in 00292 /// various places and to ensure consistency. In particular, global vars are 00293 /// restricted to 24-bits. 00294 bool has32BitTypes; 00295 00296 /// LLVM 1.2 and earlier did not provide a target triple nor a list of 00297 /// libraries on which the bytecode is dependent. LLVM 1.3 provides these 00298 /// features, for use in future versions of LLVM. 00299 bool hasNoDependentLibraries; 00300 00301 /// LLVM 1.3 and earlier caused blocks and other fields to start on 32-bit 00302 /// aligned boundaries. This can lead to as much as 30% bytecode size overhead 00303 /// in various corner cases (lots of long instructions). In LLVM 1.4, 00304 /// alignment of bytecode fields was done away with completely. 00305 bool hasAlignment; 00306 00307 // In version 4 and earlier, the bytecode format did not support the 'undef' 00308 // constant. 00309 bool hasNoUndefValue; 00310 00311 // In version 4 and earlier, the bytecode format did not save space for flags 00312 // in the global info block for functions. 00313 bool hasNoFlagsForFunctions; 00314 00315 // In version 4 and earlier, there was no opcode space reserved for the 00316 // unreachable instruction. 00317 bool hasNoUnreachableInst; 00318 00319 // In version 5, basic blocks have a minimum index of 0 whereas all the 00320 // other primitives have a minimum index of 1 (because 0 is the "null" 00321 // value. In version 5, we made this consistent. 00322 bool hasInconsistentBBSlotNums; 00323 00324 // In version 5, the types SByte and UByte were encoded as vbr_uint so that 00325 // signed values > 63 and unsigned values >127 would be encoded as two 00326 // bytes. In version 5, they are encoded directly in a single byte. 00327 bool hasVBRByteTypes; 00328 00329 // In version 5, modules begin with a "Module Block" which encodes a 4-byte 00330 // integer value 0x01 to identify the module block. This is unnecessary and 00331 // removed in version 5. 00332 bool hasUnnecessaryModuleBlockId; 00333 00334 /// CompactionTypes - If a compaction table is active in the current function, 00335 /// this is the mapping that it contains. We keep track of what resolved type 00336 /// it is as well as what global type entry it is. 00337 std::vector<std::pair<const Type*, unsigned> > CompactionTypes; 00338 00339 /// @brief If a compaction table is active in the current function, 00340 /// this is the mapping that it contains. 00341 std::vector<std::vector<Value*> > CompactionValues; 00342 00343 /// @brief This vector is used to deal with forward references to types in 00344 /// a module. 00345 TypeListTy ModuleTypes; 00346 00347 /// @brief This vector is used to deal with forward references to types in 00348 /// a function. 00349 TypeListTy FunctionTypes; 00350 00351 /// When the ModuleGlobalInfo section is read, we create a Function object 00352 /// for each function in the module. When the function is loaded, after the 00353 /// module global info is read, this Function is populated. Until then, the 00354 /// functions in this vector just hold the function signature. 00355 std::vector<Function*> FunctionSignatureList; 00356 00357 /// @brief This is the table of values belonging to the current function 00358 ValueTable FunctionValues; 00359 00360 /// @brief This is the table of values belonging to the module (global) 00361 ValueTable ModuleValues; 00362 00363 /// @brief This keeps track of function level forward references. 00364 ForwardReferenceMap ForwardReferences; 00365 00366 /// @brief The basic blocks we've parsed, while parsing a function. 00367 std::vector<BasicBlock*> ParsedBasicBlocks; 00368 00369 /// This maintains a mapping between <Type, Slot #>'s and forward references 00370 /// to constants. Such values may be referenced before they are defined, and 00371 /// if so, the temporary object that they represent is held here. @brief 00372 /// Temporary place for forward references to constants. 00373 ConstantRefsType ConstantFwdRefs; 00374 00375 /// Constant values are read in after global variables. Because of this, we 00376 /// must defer setting the initializers on global variables until after module 00377 /// level constants have been read. In the mean time, this list keeps track 00378 /// of what we must do. 00379 GlobalInitsList GlobalInits; 00380 00381 // For lazy reading-in of functions, we need to save away several pieces of 00382 // information about each function: its begin and end pointer in the buffer 00383 // and its FunctionSlot. 00384 LazyFunctionMap LazyFunctionLoadMap; 00385 00386 /// This stores the parser's handler which is used for handling tasks other 00387 /// just than reading bytecode into the IR. If this is non-null, calls on 00388 /// the (polymorphic) BytecodeHandler interface (see llvm/Bytecode/Handler.h) 00389 /// will be made to report the logical structure of the bytecode file. What 00390 /// the handler does with the events it receives is completely orthogonal to 00391 /// the business of parsing the bytecode and building the IR. This is used, 00392 /// for example, by the llvm-abcd tool for analysis of byte code. 00393 /// @brief Handler for parsing events. 00394 BytecodeHandler* Handler; 00395 00396 /// @} 00397 /// @name Implementation Details 00398 /// @{ 00399 private: 00400 /// @brief Determines if this module has a function or not. 00401 bool hasFunctions() { return ! FunctionSignatureList.empty(); } 00402 00403 /// @brief Determines if the type id has an implicit null value. 00404 bool hasImplicitNull(unsigned TyID ); 00405 00406 /// @brief Converts a type slot number to its Type* 00407 const Type *getType(unsigned ID); 00408 00409 /// @brief Converts a pre-sanitized type slot number to its Type* and 00410 /// sanitizes the type id. 00411 inline const Type* getSanitizedType(unsigned& ID ); 00412 00413 /// @brief Read in and get a sanitized type id 00414 inline const Type* readSanitizedType(); 00415 00416 /// @brief Converts a Type* to its type slot number 00417 unsigned getTypeSlot(const Type *Ty); 00418 00419 /// @brief Converts a normal type slot number to a compacted type slot num. 00420 unsigned getCompactionTypeSlot(unsigned type); 00421 00422 /// @brief Gets the global type corresponding to the TypeId 00423 const Type *getGlobalTableType(unsigned TypeId); 00424 00425 /// This is just like getTypeSlot, but when a compaction table is in use, 00426 /// it is ignored. 00427 unsigned getGlobalTableTypeSlot(const Type *Ty); 00428 00429 /// @brief Get a value from its typeid and slot number 00430 Value* getValue(unsigned TypeID, unsigned num, bool Create = true); 00431 00432 /// @brief Get a value from its type and slot number, ignoring compaction 00433 /// tables. 00434 Value *getGlobalTableValue(unsigned TyID, unsigned SlotNo); 00435 00436 /// @brief Get a basic block for current function 00437 BasicBlock *getBasicBlock(unsigned ID); 00438 00439 /// @brief Get a constant value from its typeid and value slot. 00440 Constant* getConstantValue(unsigned typeSlot, unsigned valSlot); 00441 00442 /// @brief Convenience function for getting a constant value when 00443 /// the Type has already been resolved. 00444 Constant* getConstantValue(const Type *Ty, unsigned valSlot) { 00445 return getConstantValue(getTypeSlot(Ty), valSlot); 00446 } 00447 00448 /// @brief Insert a newly created value 00449 unsigned insertValue(Value *V, unsigned Type, ValueTable &Table); 00450 00451 /// @brief Insert the arguments of a function. 00452 void insertArguments(Function* F ); 00453 00454 /// @brief Resolve all references to the placeholder (if any) for the 00455 /// given constant. 00456 void ResolveReferencesToConstant(Constant *C, unsigned Slot); 00457 00458 /// @brief Release our memory. 00459 void freeState() { 00460 freeTable(FunctionValues); 00461 freeTable(ModuleValues); 00462 } 00463 00464 /// @brief Free a table, making sure to free the ValueList in the table. 00465 void freeTable(ValueTable &Tab) { 00466 while (!Tab.empty()) { 00467 delete Tab.back(); 00468 Tab.pop_back(); 00469 } 00470 } 00471 00472 inline void error(std::string errmsg); 00473 00474 BytecodeReader(const BytecodeReader &); // DO NOT IMPLEMENT 00475 void operator=(const BytecodeReader &); // DO NOT IMPLEMENT 00476 00477 /// @} 00478 /// @name Reader Primitives 00479 /// @{ 00480 private: 00481 00482 /// @brief Is there more to parse in the current block? 00483 inline bool moreInBlock(); 00484 00485 /// @brief Have we read past the end of the block 00486 inline void checkPastBlockEnd(const char * block_name); 00487 00488 /// @brief Align to 32 bits 00489 inline void align32(); 00490 00491 /// @brief Read an unsigned integer as 32-bits 00492 inline unsigned read_uint(); 00493 00494 /// @brief Read an unsigned integer with variable bit rate encoding 00495 inline unsigned read_vbr_uint(); 00496 00497 /// @brief Read an unsigned integer of no more than 24-bits with variable 00498 /// bit rate encoding. 00499 inline unsigned read_vbr_uint24(); 00500 00501 /// @brief Read an unsigned 64-bit integer with variable bit rate encoding. 00502 inline uint64_t read_vbr_uint64(); 00503 00504 /// @brief Read a signed 64-bit integer with variable bit rate encoding. 00505 inline int64_t read_vbr_int64(); 00506 00507 /// @brief Read a string 00508 inline std::string read_str(); 00509 00510 /// @brief Read a float value 00511 inline void read_float(float& FloatVal); 00512 00513 /// @brief Read a double value 00514 inline void read_double(double& DoubleVal); 00515 00516 /// @brief Read an arbitrary data chunk of fixed length 00517 inline void read_data(void *Ptr, void *End); 00518 00519 /// @brief Read a bytecode block header 00520 inline void read_block(unsigned &Type, unsigned &Size); 00521 00522 /// @brief Read a type identifier and sanitize it. 00523 inline bool read_typeid(unsigned &TypeId); 00524 00525 /// @brief Recalculate type ID for pre 1.3 bytecode files. 00526 inline bool sanitizeTypeId(unsigned &TypeId ); 00527 /// @} 00528 }; 00529 00530 /// @brief A function for creating a BytecodeAnalzer as a handler 00531 /// for the Bytecode reader. 00532 BytecodeHandler* createBytecodeAnalyzerHandler(BytecodeAnalysis& bca, 00533 std::ostream* output ); 00534 00535 00536 } // End llvm namespace 00537 00538 // vim: sw=2 00539 #endif