Rebased PNaCl localmods in LLVM to 223109

include/llvm/Bitcode/NaCl/NaClBitcodeParser.h

+//===- NaClBitcodeParser.h -----------------------------------*- C++ -*-===//
+//     Low-level bitcode driver to parse PNaCl bitcode files.
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Parses and processes low-level PNaCl bitcode files. Defines class
+// NaClBitcodeParser.
+//
+// The concepts of PNaCl bitcode files are basically the same as for
+// LLVM bitcode files (see http://llvm.org/docs/BitCodeFormat.html for
+// details).
+//
+// The bitstream format is an abstract encoding of structured data,
+// very similar to XML in some ways. Like XML, bitstream files contain
+// tags, and nested structures, and you can parse the file without
+// having to understand the tags. Unlike XML, the bitstream format is
+// a binary encoding, and provides a mechanism for the file to
+// self-describe "abbreviations".  Abbreviations are effectively size
+// optimizations for the content.
+//
+// The bitcode file is conceptually a sequence of "blocks", defining
+// the content. Blocks contain a sequence of records and
+// blocks. Nested content is defined using nested blocks.  A (data)
+// "record" is a tag, and a vector of (unsigned integer) values.
+//
+// Blocks are identified using Block IDs. Each kind of block has a
+// unique block "ID". Records have two elements:
+//
+//   a) A "code" identifying what type of record it is.
+//   b) A vector of "values" defining the contents of the record.
+//
+// The bitstream "reader" (defined in NaClBitstreamReader.h) defines
+// the implementation that converts the low-level bit file into
+// records and blocks. The bit stream is processed by moving a
+// "cursor" over the sequence of bits.
+//
+// The bitstream reader assumes that each block/record is read in by
+// first reading the "entry". The entry defines whether it corresponds
+// to one of the following:
+//
+//    a) At the beginning of a (possibly nested) block
+//    b) At the end of the current block.
+//    c) The input defines an abberviation.
+//    d) The input defines a record.
+//
+// An entry contains two values, a "kind" and an "ID". The kind
+// defines which of the four cases above occurs. The ID provides
+// identifying information on how to further process the input. For
+// case (a), the ID is the identifier associated with the the block
+// being processed. For case (b) and (c) the ID is ignored. For case
+// (d) the ID identifies the abbreviation that should be used to parse
+// the values.
+//
+// The class NaClBitcodeParser defines a bitcode parser that extracts
+// the blocks and records, which are then processed using virtual
+// callbacks. In general, you will want to implement derived classes
+// for each type of block, so that the corresponding data is processed
+// appropriately.
+//
+// The class NaClBitcodeParser parses a bitcode block, and defines a
+// set of callbacks for that block, including:
+//
+//    a) EnterBlock: What to do once we have entered the block.
+//    b) ProcessRecord: What to do with each parsed record.
+//    c) ParseBlock: Parse the (nested) block with the given ID.
+//    d) ExitBlock: What to do once we have finished processing the block.
+//
+// Note that a separate instance of NaClBitcodeParser (or a
+// corresponding derived class) is created for each nested block. Each
+// instance is responsible for only parsing a single block. Method
+// ParseBlock creates new instances to parse nested blocks. Method
+// GetEnclosingParser() can be used to refer to the parser associated
+// with the enclosing block.
+//
+// Currently, the default processing of abbreviations is handled by
+// the PNaCl bitstream reader, rather than by the parser. A hook,
+// ProcessBlockInfo exists if you want to do some processing before the
+// BlockInfo block is exited.
+//
+// If you need to process abbreviations processed by the PNaCl
+// bitstream reader, you must explicitly define a
+// NaClBitcodeParserListener to listen (within the bitstream reader),
+// and make appropriate call backs to the NaClBitcodeParser.
+// The listener is glued to parsers using method SetListener.
+//
+// TODO(kschimpf): Define an intermediate derived class of
+// NaClBitcodeParser that defines callbacks based on the actual
+// structure of PNaCl bitcode files.  That is, it has callbacks for
+// each of the types of blocks (i.e. module, types, global variables,
+// function, symbol tables etc). This derivied class can then be used
+// as the base class for the bitcode reader.
+// ===----------------------------------------------------------------------===//
+
+#ifndef LLVM_BITCODE_NACL_NACLBITCODEPARSER_H
+#define LLVM_BITCODE_NACL_NACLBITCODEPARSER_H
+
+#include "llvm/Bitcode/NaCl/NaClBitstreamReader.h"
+#include "llvm/Support/raw_ostream.h"
+#include <vector>
+
+namespace llvm {
+
+namespace naclbitc {
+  // Special record codes used to model codes for predefined records.
+  // They are very large so that they do not conflict with existing
+  // record codes for user-defined blocks.
+  enum SpecialBlockCodes {
+    BLK_CODE_ENTER = 65535,
+    BLK_CODE_EXIT  = 65534,
+    BLK_CODE_DEFINE_ABBREV = 65533,
+    BLK_CODE_HEADER = 65532
+  };
+
+}
+
+class NaClBitcodeRecord;
+class NaClBitcodeParser;
+class NaClBitcodeParserListener;
+
+// Defines the base class for data extracted from the input bitstream
+// (i.e blocks and records).
+class NaClBitcodeData {
+  void operator=(const NaClBitcodeData&) LLVM_DELETED_FUNCTION;
+
+public:
+  /// Create data element to be read from input cursor.
+  explicit NaClBitcodeData(NaClBitstreamCursor &Cursor)
+      : Cursor(Cursor), StartBit(Cursor.GetCurrentBitNo())
+  {}
+
+  /// Create copy of the given data element.
+  explicit NaClBitcodeData(const NaClBitcodeData &Data)
+      : Cursor(Data.Cursor), StartBit(Data.StartBit)
+  {}
+
+  /// Returns the bitstream reader being used.
+  NaClBitstreamReader &GetReader() const {
+    return *Cursor.getBitStreamReader();
+  }
+
+  /// Returns the cursor position within the bitstream.
+  NaClBitstreamCursor &GetCursor() const {
+    return Cursor;
+  }
+
+  /// Returns the number of bits defined by the data.
+  uint64_t GetNumBits() const {
+    return GetCursor().GetCurrentBitNo() - StartBit;
+  }
+
+  /// Returns the first bit of the stream data.
+  uint64_t GetStartBit() const {
+    return StartBit;
+  }
+
+protected:
+  /// Change the start bit for the data to the new value.
+  void SetStartBit(uint64_t NewValue) {
+    StartBit = NewValue;
+  }
+
+private:
+  // The bitstream cursor defining location within the bitcode file.
+  NaClBitstreamCursor &Cursor;
+
+  // Start bit for the record.
+  uint64_t StartBit;
+};
+
+/// Models the block defined by a (begin) block record, through the
+/// (end) block record.
+class NaClBitcodeBlock : public NaClBitcodeData {
+  NaClBitcodeBlock(const NaClBitcodeBlock &) LLVM_DELETED_FUNCTION;
+  void operator=(const NaClBitcodeBlock &) LLVM_DELETED_FUNCTION;
+
+public:
+  /// Given the found (begin) block record for block BlockID, create
+  /// the corresponding data associated with that block.
+  NaClBitcodeBlock(unsigned BlockID, const NaClBitcodeRecord &Record);
+
+  /// Create block data for block BlockID, using the input cursor.
+  NaClBitcodeBlock(unsigned BlockID, NaClBitstreamCursor &Cursor)
+      : NaClBitcodeData(Cursor),
+        BlockID(BlockID),
+        EnclosingBlock(0)
+  {
+    LocalStartBit = GetStartBit();
+  }
+
+  /// Print the contents out to the given stream.
+  void Print(raw_ostream& os) const;
+
+  /// Returns pointer to the enclosing block.
+  const NaClBitcodeBlock *GetEnclosingBlock() const {
+    return EnclosingBlock;
+  }
+
+  /// Returns the block ID of the block.
+  unsigned GetBlockID() const {
+    return BlockID;
+  }
+
+  /// Returns the number of bits in the block associated with the
+  /// bitcode parser parsing this block, excluding nested blocks.
+  unsigned GetLocalNumBits() const {
+    return GetCursor().GetCurrentBitNo() - LocalStartBit;
+  }
+
+protected:
+  // The block ID associated with this record.
+  unsigned BlockID;
+  // The enclosing block, if defined.
+  const NaClBitcodeBlock *EnclosingBlock;
+  // Start bit for the block, updated to skip nested blocks.
+  uint64_t LocalStartBit;
+
+  // Note: We friend class NaClBitcodeParser, so that it can
+  // update field LocalStartBit.
+  friend class NaClBitcodeParser;
+};
+
+typedef NaClBitcodeRecordVector NaClRecordVector;
+
+class NaClBitcodeRecordData {
+public:
+  // The selector code associated with the record.
+  unsigned Code;
+  // The sequence of values defining the parsed record.
+  NaClRecordVector Values;
+
+  void Print(raw_ostream &strm) const;
+};
+
+inline raw_ostream &operator<<(raw_ostream &Strm,
+                               const NaClBitcodeRecordData &Data) {
+  Data.Print(Strm);
+  return Strm;
+}
+
+/// Simple container class to convert the values of the corresponding
+/// read record to a simpler form, only containing values.
+struct NaClBitcodeValues {
+public:
+  NaClBitcodeValues(const NaClBitcodeRecordData &Record)
+      : Record(Record) {}
+
+  size_t size() const {
+    return Record.Values.size()+1;
+  }
+
+  uint64_t operator[](size_t index) const {
+    return index == 0 ? Record.Code : Record.Values[index-1];
+  }
+
+private:
+  const NaClBitcodeRecordData &Record;
+};
+
+/// Defines the data associated with reading a block record in the
+/// PNaCl bitcode stream.
+class NaClBitcodeRecord : public NaClBitcodeData {
+public:
+  /// Type for vector of values representing a record.
+  typedef NaClRecordVector RecordVector;
+
+  /// Creates a bitcode record, starting at the position defined
+  /// by cursor.
+  explicit NaClBitcodeRecord(const NaClBitcodeBlock &Block)
+      : NaClBitcodeData(Block.GetCursor()),
+        Block(Block)
+  {}
+
+  /// Print the contents out to the given stream.
+  void Print(raw_ostream& os) const;
+
+  /// The block the record appears in.
+  const NaClBitcodeBlock &GetBlock() const {
+    return Block;
+  }
+
+  /// Returns the block ID associated with the record.
+  unsigned GetBlockID() const {
+    return Block.GetBlockID();
+  }
+
+  /// Returns the kind of entry read from the input stream.
+  unsigned GetEntryKind() const {
+    return Entry.Kind;
+  }
+
+  /// Returns the code value (i.e. selector) associated with the
+  /// record.
+  unsigned GetCode() const {
+    return Data.Code;
+  }
+
+  /// Returns the EntryID (e.g. abbreviation if !=
+  /// naclbitc::UNABBREV_RECORD) associated with the record. Note:
+  /// for block-enter, block-exit, and define-abbreviation, EntryID is
+  /// not the corresponding abbreviation.
+  unsigned GetEntryID() const {
+    return Entry.ID;
+  }
+
+  /// Returns the (value) record associated with the read record.
+  const RecordVector &GetValues() const {
+    return Data.Values;
+  }
+
+  /// Allows lower level access to data representing record.
+  const NaClBitcodeRecordData &GetRecordData() const {
+    return Data;
+  }
+
+  /// Returns true if the record was read using an abbreviation.
+  bool UsedAnAbbreviation() const {
+    return GetEntryKind() == NaClBitstreamEntry::Record &&
+        GetEntryID() != naclbitc::UNABBREV_RECORD;
+  }
+
+  /// Returns the abbrevation index used to read the record.
+  /// Returns naclbitc::UNABBREV_RECORD if not applicable.
+  unsigned GetAbbreviationIndex() const {
+    return UsedAnAbbreviation()
+        ? GetEntryID() : static_cast<unsigned>(naclbitc::UNABBREV_RECORD);
+  }
+
+  /// Destructively change the abbreviation ID to the given value.
+  void SetAbbreviationIndex(unsigned Index) {
+    Entry.ID = Index;
+  }
+
+protected:
+  // The block associated with the record.
+  const NaClBitcodeBlock &Block;
+  // The data of the record.
+  NaClBitcodeRecordData Data;
+  // The entry (i.e. value(s) preceding the record that define what
+  // value comes next).
+  NaClBitstreamEntry Entry;
+
+private:
+  // Allows class NaClBitcodeParser to read values into the
+  // record, thereby hiding the details of how to read values.
+  friend class NaClBitcodeParser;
+  friend class NaClBitcodeParserListener;
+
+  /// Read bitstream entry. Defines what construct appears next in the
+  /// bitstream.
+  void ReadEntry() {
+    SetStartBit(GetCursor().GetCurrentBitNo());
+    Entry = GetCursor().
+        advance(NaClBitstreamCursor::AF_DontAutoprocessAbbrevs, 0);
+  }
+
+  /// Reads in a record's values, if the entry defines a record (Must
+  /// be called after ReadEntry).
+  void ReadValues() {
+    Data.Values.clear();
+    Data.Code = GetCursor().readRecord(Entry.ID, Data.Values);
+  }
+
+  NaClBitcodeRecord(const NaClBitcodeRecord &Rcd) LLVM_DELETED_FUNCTION;
+  void operator=(const NaClBitcodeRecord &Rcd) LLVM_DELETED_FUNCTION;
+};
+
+inline raw_ostream &operator<<(raw_ostream &Strm,
+                               const NaClBitcodeRecord &Record) {
+  Record.Print(Strm);
+  return Strm;
+}
+
+/// Defines a listener to handle abbreviations within a bitcode file.
+/// In particular, abbreviations and the BlockInfo block are made more
+/// explicit, and then sent to the parser through virtuals
+/// ProcessAbbreviation and SetBID.
+class NaClBitcodeParserListener : public NaClAbbrevListener {
+  friend class NaClBitcodeParser;
+public:
+  // Constructs a listener for the given parser.  Note: All nested
+  // parsers automatically inherit this listener.
+  NaClBitcodeParserListener(NaClBitcodeParser *Parser)
+      : Parser(Parser), GlobalBlockID(naclbitc::BLOCKINFO_BLOCK_ID) {
+  }
+
+  virtual ~NaClBitcodeParserListener() {}
+
+private:
+  virtual void BeginBlockInfoBlock(unsigned NumWords);
+
+  virtual void SetBID();
+
+  virtual void EndBlockInfoBlock();
+
+  virtual void ProcessAbbreviation(NaClBitCodeAbbrev *Abbrev,
+                                   bool IsLocal);
+
+  /// The block parser currently being listened to.
+  NaClBitcodeParser *Parser;
+
+  /// The block ID to use if a global abbreviation. Note: This field is
+  /// updated by calls to method SetBID.
+  unsigned GlobalBlockID;
+};
+
+/// Parses a block in the PNaCl bitcode stream.
+class NaClBitcodeParser {
+  // Allow listener privledges, so that it can update/call the parser
+  // using a clean API.
+  friend class NaClBitcodeParserListener;
+public:
+
+  // Creates a parser to parse the the block at the given cursor in
+  // the PNaCl bitcode stream. This instance is a "dummy" instance
+  // that starts the parser.
+  explicit NaClBitcodeParser(NaClBitstreamCursor &Cursor)
+      : EnclosingParser(0),
+        Block(ILLEGAL_BLOCK_ID, Cursor),
+        Record(Block),
+        Listener(0),
+        ErrStream(&errs())
+  {}
+
+  virtual ~NaClBitcodeParser();
+
+  /// Reads the (top-level) block associated with the given block
+  /// record at the stream cursor. Returns true if unable to parse.
+  /// Can be called multiple times to parse multiple blocks.
+  bool Parse();
+
+  // Called once the bitstream reader has entered the corresponding
+  // subblock.  Argument NumWords is set to the number of words in the
+  // corresponding subblock.
+  virtual void EnterBlock(unsigned /*NumWords*/) {}
+
+  // Called when the corresponding EndBlock of the block being parsed
+  // is found.
+  virtual void ExitBlock() {}
+
+  // Called after a BlockInfo block is parsed.
+  virtual void ProcessBlockInfo() {}
+
+  // Called after each record (within the block) is read (into field Record).
+  virtual void ProcessRecord() {}
+
+  // Called if a SetBID record is encountered in the BlockInfo block,
+  // and the parser has a listener.
+  virtual void SetBID() {}
+
+  // Called to process an abbreviation if the parser has a listener.
+  virtual void ProcessAbbreviation(unsigned /*BlockID*/,
+                                   NaClBitCodeAbbrev * /*Abbrev*/,
+                                   bool /*IsLocal*/) {}
+
+  // Creates an instance of the NaClBitcodeParser to use to parse the
+  // block with the given block ID, and then call's method
+  // ParseThisBlock() to parse the corresponding block. Note:
+  // Each derived class should define it's own version of this
+  // method, following the pattern below.
+  virtual bool ParseBlock(unsigned BlockID) {
+    // Default implementation just builds a parser that does nothing.
+    NaClBitcodeParser Parser(BlockID, this);
+    return Parser.ParseThisBlock();
+  }
+
+  // Changes the stream to print errors to, and returns the old error stream.
+  // There are two use cases:
+  // 1) To change (from the default errs()) inside the constructor of the
+  //    derived class. In this context, it will be used for all error
+  //    messages for the derived class.
+  // 2) Temporarily modify it for a single error message. In this context,
+  //    the method Error() is overridden in the derived class, and
+  //    calls this method twice. Once before calling base method Error(),
+  //    and followed by a second call to restore the default error stream.
+  raw_ostream &setErrStream(raw_ostream &Stream) {
+    raw_ostream &OldErrStream = *ErrStream;
+    ErrStream = &Stream;
+    return OldErrStream;
+  }
+
+  // Called when error occurs. Message is the error to report. Always
+  // returns true (the error return value of Parse).
+  virtual bool Error(const std::string &Message) {
+    *ErrStream << "Error: " << Message << "\n";
+    return true;
+  }
+
+  // Returns the number of bits in this block, including nested blocks.
+  unsigned GetBlockNumBits() const {
+    return Block.GetNumBits();
+  }
+
+  // Returns the number of bits in this block, excluding nested blocks.
+  unsigned GetBlockLocalNumBits() const {
+    return Block.GetLocalNumBits();
+  }
+
+  /// Returns the block ID associated with the Parser.
+  unsigned GetBlockID() const {
+    return Block.GetBlockID();
+  }
+
+  NaClBitcodeBlock &GetBlock() {
+    return Block;
+  }
+
+  /// Returns the enclosing parser of this block.
+  NaClBitcodeParser *GetEnclosingParser() const {
+    // Note: The top-level parser instance is a dummy instance
+    // and is not considered an enclosing parser.
+    return EnclosingParser->EnclosingParser ? EnclosingParser : 0;
+  }
+
+  // Parses the block using the parser defined by
+  // ParseBlock(unsigned).  Returns true if unable to parse the
+  // block. Note: Should only be called by virtual ParseBlock(unsigned).
+  bool ParseThisBlock() {
+    bool Results;
+    if (Listener) {
+      NaClBitcodeParser *CallingParser = Listener->Parser;
+      Listener->Parser = this;
+      Results = ParseThisBlockInternal();
+      Listener->Parser = CallingParser;
+    } else {
+      Results = ParseThisBlockInternal();
+    }
+    return Results;
+  }
+
+  /// Skips the current block, assuming the parser is at the beginning
+  /// of the block. That is, Record.GetEntryKind() equals
+  /// NaClBitstreamEntry::SubBlock. Returns false if
+  /// successful. Otherwise returns 1.
+  bool SkipBlock() {
+    if (Record.GetEntryKind() != NaClBitstreamEntry::SubBlock)
+      return Error("SkipBlock on non-block record");
+    return Record.GetCursor().SkipBlock();
+  }
+
+protected:
+  // The containing parser.
+  NaClBitcodeParser *EnclosingParser;
+
+  // The block the parser is associated with.
+  NaClBitcodeBlock Block;
+
+  // The current record (within the block) being processed.
+  NaClBitcodeRecord Record;
+
+  // The listener (if any) to use.
+  NaClBitcodeParserListener *Listener;
+
+  // The error stream to use if non-null (uses errs() if null).
+  raw_ostream *ErrStream;
+
+  // Creates a block parser to parse the block associated with the
+  // bitcode entry that defines the beginning of a block. This
+  // instance actually parses the corresponding block.
+  NaClBitcodeParser(unsigned BlockID, NaClBitcodeParser *EnclosingParser)
+      : EnclosingParser(EnclosingParser),
+        Block(BlockID, EnclosingParser->Record),
+        Record(Block),
+        Listener(EnclosingParser->Listener),
+        ErrStream(EnclosingParser->ErrStream)
+  {}
+
+  /// Defines the listener for this block, and all enclosing blocks,
+  /// to be the given listener. Should be set in the constructor.
+  void SetListener(NaClBitcodeParserListener* UseListener) {
+    Listener = UseListener;
+  }
+
+private:
+  // Special constant identifying the top-level instance.
+  static const unsigned ILLEGAL_BLOCK_ID = UINT_MAX;
+
+  // Parses the block. Returns true if unable to parse the
+  // block. Note: Should only be called by virtual ParseThisBlock.
+  bool ParseThisBlockInternal() {
+    bool Results;
+    if (GetBlockID() == naclbitc::BLOCKINFO_BLOCK_ID) {
+      Results = ParseBlockInfoInternal();
+    } else {
+      Results = ParseBlockInternal();
+      ExitBlock();
+    }
+    return Results;
+  }
+
+  // Parses a BlockInfo block, where processing is handled through
+  // a listener in the bitstream reader.
+  bool ParseBlockInfoInternal();
+
+  // Parses the non-BlockInfo block. Returns true if unable to parse the
+  // block.
+  bool ParseBlockInternal();
+
+
+  void operator=(const NaClBitcodeParser &Parser) LLVM_DELETED_FUNCTION;
+  NaClBitcodeParser(const NaClBitcodeParser &Parser) LLVM_DELETED_FUNCTION;
+
+};
+
+}  // namespace llvm
+
+#endif