path: root/lib/Bytecode/Reader/Reader.h

//===-- Reader.h - Interface To Bytecode Reading ----------------*- C++ -*-===//
// 
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Reid Spencer and is distributed under the 
// University of Illinois Open Source License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
//  This header file defines the interface to the Bytecode Reader which is 
//  responsible for correctly interpreting bytecode files (backwards compatible)
//  and materializing a module from the bytecode read.
//
//===----------------------------------------------------------------------===//

#ifndef BYTECODE_PARSER_H
#define BYTECODE_PARSER_H

#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/GlobalValue.h"
#include "llvm/Function.h"
#include "llvm/ModuleProvider.h"
#include "llvm/Bytecode/Analyzer.h"
#include <utility>
#include <map>

namespace llvm {

class BytecodeHandler; ///< Forward declare the handler interface

/// This class defines the interface for parsing a buffer of bytecode. The
/// parser itself takes no action except to call the various functions of
/// the handler interface. The parser's sole responsibility is the correct
/// interpretation of the bytecode buffer. The handler is responsible for 
/// instantiating and keeping track of all values. As a convenience, the parser 
/// is responsible for materializing types and will pass them through the
/// handler interface as necessary.
/// @see BytecodeHandler
/// @brief Bytecode Reader interface
class BytecodeReader : public ModuleProvider {

/// @name Constructors
/// @{
public:
  /// @brief Default constructor. By default, no handler is used.
  BytecodeReader( 
    BytecodeHandler* h = 0
  ) { 
    Handler = h; 
  }

  ~BytecodeReader() { freeState(); }

/// @}
/// @name Types
/// @{
public:

  /// @brief A convenience type for the buffer pointer
  typedef const unsigned char* BufPtr;

  /// @brief The type used for a vector of potentially abstract types
  typedef std::vector<PATypeHolder> TypeListTy;

  /// This type provides a vector of Value* via the User class for
  /// storage of Values that have been constructed when reading the
  /// bytecode. Because of forward referencing, constant replacement
  /// can occur so we ensure that our list of Value* is updated
  /// properly through those transitions. This ensures that the
  /// correct Value* is in our list when it comes time to associate
  /// constants with global variables at the end of reading the
  /// globals section.
  /// @brief A list of values as a User of those Values.
  struct ValueList : public User {
    ValueList() : User(Type::VoidTy, Value::ValueListVal) {}

    // vector compatibility methods
    unsigned size() const { return getNumOperands(); }
    void push_back(Value *V) { Operands.push_back(Use(V, this)); }
    Value *back() const { return Operands.back(); }
    void pop_back() { Operands.pop_back(); }
    bool empty() const { return Operands.empty(); }
    // must override this 
    virtual void print(std::ostream& os) const {
      for ( unsigned i = 0; i < size(); i++ ) {
        os << i << " ";
        getOperand(i)->print(os);
        os << "\n";
      }
    }
  };

  /// @brief A 2 dimensional table of values
  typedef std::vector<ValueList*> ValueTable;

  /// This map is needed so that forward references to constants can be looked 
  /// up by Type and slot number when resolving those references.
  /// @brief A mapping of a Type/slot pair to a Constant*.
  typedef std::map<std::pair<const Type*,unsigned>, Constant*> ConstantRefsType;

  /// For lazy read-in of functions, we need to save the location in the
  /// data stream where the function is located. This structure provides that
  /// information. Lazy read-in is used mostly by the JIT which only wants to
  /// resolve functions as it needs them. 
  /// @brief Keeps pointers to function contents for later use.
  struct LazyFunctionInfo {
    const unsigned char *Buf, *EndBuf;
    LazyFunctionInfo(const unsigned char *B = 0, const unsigned char *EB = 0)
      : Buf(B), EndBuf(EB) {}
  };

  /// @brief A mapping of functions to their LazyFunctionInfo for lazy reading.
  typedef std::map<Function*, LazyFunctionInfo> LazyFunctionMap;

  /// @brief A list of global variables and the slot number that initializes
  /// them.
  typedef std::vector<std::pair<GlobalVariable*, unsigned> > GlobalInitsList;

  /// This type maps a typeslot/valueslot pair to the corresponding Value*.
  /// It is used for dealing with forward references as values are read in.
  /// @brief A map for dealing with forward references of values.
  typedef std::map<std::pair<unsigned,unsigned>,Value*> ForwardReferenceMap;

/// @}
/// @name Methods
/// @{
public:
  /// @brief Main interface to parsing a bytecode buffer.
  void ParseBytecode(
     const unsigned char *Buf,    ///< Beginning of the bytecode buffer
     unsigned Length,             ///< Length of the bytecode buffer
     const std::string &ModuleID, ///< An identifier for the module constructed.
     bool processFunctions=false  ///< Process all function bodies fully.
  );

  /// @brief Parse all function bodies
  void ParseAllFunctionBodies();

  /// @brief Parse the next function of specific type
  void ParseFunction(Function* Func) ;

  /// This method is abstract in the parent ModuleProvider class. Its
  /// implementation is identical to the ParseFunction method.
  /// @see ParseFunction
  /// @brief Make a specific function materialize.
  virtual void materializeFunction(Function *F) {
    LazyFunctionMap::iterator Fi = LazyFunctionLoadMap.find(F);
    if (Fi == LazyFunctionLoadMap.end()) return;
    ParseFunction(F);
  }

  /// This method is abstract in the parent ModuleProvider class. Its
  /// implementation is identical to ParseAllFunctionBodies. 
  /// @see ParseAllFunctionBodies
  /// @brief Make the whole module materialize
  virtual Module* materializeModule() {
    ParseAllFunctionBodies();
    return TheModule;
  }

  /// This method is provided by the parent ModuleProvde class and overriden
  /// here. It simply releases the module from its provided and frees up our
  /// state.
  /// @brief Release our hold on the generated module
  Module* releaseModule() {
    // Since we're losing control of this Module, we must hand it back complete
    Module *M = ModuleProvider::releaseModule();
    freeState();
    return M;
  }

/// @}
/// @name Parsing Units For Subclasses
/// @{
protected:
  /// @brief Parse whole module scope
  void ParseModule();

  /// @brief Parse the version information block
  void ParseVersionInfo();

  /// @brief Parse the ModuleGlobalInfo block
  void ParseModuleGlobalInfo();

  /// @brief Parse a symbol table
  void ParseSymbolTable( Function* Func, SymbolTable *ST);

  /// @brief Parse functions lazily.
  void ParseFunctionLazily();

  ///  @brief Parse a function body
  void ParseFunctionBody(Function* Func);

  /// @brief Parse the type list portion of a compaction table
  void BytecodeReader::ParseCompactionTypes( unsigned NumEntries );

  /// @brief Parse a compaction table
  void ParseCompactionTable();

  /// @brief Parse global types
  void ParseGlobalTypes();

  /// @brief Parse a basic block (for LLVM 1.0 basic block blocks)
  BasicBlock* ParseBasicBlock(unsigned BlockNo);

  /// @brief parse an instruction list (for post LLVM 1.0 instruction lists
  /// with blocks differentiated by terminating instructions.
  unsigned ParseInstructionList(
    Function* F   ///< The function into which BBs will be inserted
  );
  
  /// @brief Parse a single instruction.
  void ParseInstruction(
    std::vector<unsigned>& Args,   ///< The arguments to be filled in
    BasicBlock* BB             ///< The BB the instruction goes in
  );

  /// @brief Parse the whole constant pool
  void ParseConstantPool(ValueTable& Values, TypeListTy& Types, 
                         bool isFunction);

  /// @brief Parse a single constant value
  Constant* ParseConstantValue(unsigned TypeID);

  /// @brief Parse a block of types constants
  void ParseTypes(TypeListTy &Tab, unsigned NumEntries);

  /// @brief Parse a single type constant
  const Type *ParseType();

  /// @brief Parse a string constants block
  void ParseStringConstants(unsigned NumEntries, ValueTable &Tab);

/// @}
/// @name Data
/// @{
private:
  BufPtr MemStart;     ///< Start of the memory buffer
  BufPtr MemEnd;       ///< End of the memory buffer
  BufPtr BlockStart;   ///< Start of current block being parsed
  BufPtr BlockEnd;     ///< End of current block being parsed
  BufPtr At;           ///< Where we're currently parsing at

  /// Information about the module, extracted from the bytecode revision number.
  unsigned char RevisionNum;        // The rev # itself

  /// Flags to distinguish LLVM 1.0 & 1.1 bytecode formats (revision #0)

  /// Revision #0 had an explicit alignment of data only for the ModuleGlobalInfo
  /// block.  This was fixed to be like all other blocks in 1.2
  bool hasInconsistentModuleGlobalInfo;

  /// Revision #0 also explicitly encoded zero values for primitive types like
  /// int/sbyte/etc.
  bool hasExplicitPrimitiveZeros;

  // Flags to control features specific the LLVM 1.2 and before (revision #1)

  /// LLVM 1.2 and earlier required that getelementptr structure indices were
  /// ubyte constants and that sequential type indices were longs.
  bool hasRestrictedGEPTypes;

  /// LLVM 1.2 and earlier had class Type deriving from Value and the Type
  /// objects were located in the "Type Type" plane of various lists in read
  /// by the bytecode reader. In LLVM 1.3 this is no longer the case. Types are
  /// completely distinct from Values. Consequently, Types are written in fixed
  /// locations in LLVM 1.3. This flag indicates that the older Type derived
  /// from Value style of bytecode file is being read.
  bool hasTypeDerivedFromValue;

  /// LLVM 1.2 and earlier encoded block headers as two uint (8 bytes), one for
  /// the size and one for the type. This is a bit wasteful, especially for small 
  /// files where the 8 bytes per block is a large fraction of the total block 
  /// size. In LLVM 1.3, the block type and length are encoded into a single 
  /// uint32 by restricting the number of block types (limit 31) and the maximum
  /// size of a block (limit 2^27-1=134,217,727). Note that the module block
  /// still uses the 8-byte format so the maximum size of a file can be
  /// 2^32-1 bytes long.
  bool hasLongBlockHeaders;

  /// LLVM 1.2 and earlier wrote floating point values in a platform specific
  /// bit ordering. This was fixed in LLVM 1.3
  bool hasPlatformSpecificFloatingPoint;

  /// LLVM 1.2 and earlier wrote type slot numbers as vbr_uint32. In LLVM 1.3
  /// this has been reduced to vbr_uint24. It shouldn't make much difference 
  /// since we haven't run into a module with > 24 million types, but for safety
  /// the 24-bit restriction has been enforced in 1.3 to free some bits in
  /// various places and to ensure consistency. In particular, global vars are
  /// restricted to 24-bits.
  bool has32BitTypes;

  /// LLVM 1.2 and earlier did not provide a target triple nor a list of 
  /// libraries on which the bytecode is dependent. LLVM 1.3 provides these