Rebased PNaCl localmods in LLVM to 223109

include/llvm/Bitcode/NaCl/NaClBitstreamReader.h

+//===- NaClBitstreamReader.h -----------------------------------*- C++ -*-===//
+//     Low-level bitstream reader interface
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This header defines the BitstreamReader class.  This class can be used to
+// read an arbitrary bitstream, regardless of its contents.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_BITCODE_NACL_NACLBITSTREAMREADER_H
+#define LLVM_BITCODE_NACL_NACLBITSTREAMREADER_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Bitcode/NaCl/NaClLLVMBitCodes.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/StreamingMemoryObject.h"
+#include <climits>
+#include <vector>
+
+namespace llvm {
+
+class Deserializer;
+
+/// NaClBitstreamReader - This class is used to read from a NaCl
+/// bitcode wire format stream, maintaining information that is global
+/// to decoding the entire file.  While a file is being read, multiple
+/// cursors can be independently advanced or skipped around within the
+/// file.  These are represented by the NaClBitstreamCursor class.
+class NaClBitstreamReader {
+public:
+  /// BlockInfo - This contains information emitted to BLOCKINFO_BLOCK blocks.
+  /// These describe abbreviations that all blocks of the specified ID inherit.
+  struct BlockInfo {
+    unsigned BlockID;
+    std::vector<NaClBitCodeAbbrev*> Abbrevs;
+  };
+private:
+  std::unique_ptr<MemoryObject> BitcodeBytes;
+
+  std::vector<BlockInfo> BlockInfoRecords;
+
+  /// \brief Holds the offset of the first byte after the header.
+  size_t InitialAddress;
+
+  NaClBitstreamReader(const NaClBitstreamReader&) LLVM_DELETED_FUNCTION;
+  void operator=(const NaClBitstreamReader&) LLVM_DELETED_FUNCTION;
+public:
+  NaClBitstreamReader() : InitialAddress(0) {}
+
+  NaClBitstreamReader(const unsigned char *Start, const unsigned char *End,
+                      size_t MyInitialAddress=0) {
+    InitialAddress = MyInitialAddress;
+    init(Start, End);
+  }
+
+  NaClBitstreamReader(MemoryObject *Bytes, size_t MyInitialAddress=0)
+      : InitialAddress(MyInitialAddress) {
+    BitcodeBytes.reset(Bytes);
+  }
+
+  void init(const unsigned char *Start, const unsigned char *End) {
+    assert(((End-Start) & 3) == 0 &&"Bitcode stream not a multiple of 4 bytes");
+    BitcodeBytes.reset(getNonStreamedMemoryObject(Start, End));
+  }
+
+  MemoryObject &getBitcodeBytes() { return *BitcodeBytes; }
+
+  ~NaClBitstreamReader() {
+    // Free the BlockInfoRecords.
+    while (!BlockInfoRecords.empty()) {
+      BlockInfo &Info = BlockInfoRecords.back();
+      // Free blockinfo abbrev info.
+      for (unsigned i = 0, e = static_cast<unsigned>(Info.Abbrevs.size());
+           i != e; ++i)
+        Info.Abbrevs[i]->dropRef();
+      BlockInfoRecords.pop_back();
+    }
+  }
+
+  /// \brief Returns the initial address (after the header) of the input stream.
+  size_t getInitialAddress() const {
+    return InitialAddress;
+  }
+
+  //===--------------------------------------------------------------------===//
+  // Block Manipulation
+  //===--------------------------------------------------------------------===//
+
+  /// hasBlockInfoRecords - Return true if we've already read and processed the
+  /// block info block for this Bitstream.  We only process it for the first
+  /// cursor that walks over it.
+  bool hasBlockInfoRecords() const { return !BlockInfoRecords.empty(); }
+
+  /// getBlockInfo - If there is block info for the specified ID, return it,
+  /// otherwise return null.
+  const BlockInfo *getBlockInfo(unsigned BlockID) const {
+    // Common case, the most recent entry matches BlockID.
+    if (!BlockInfoRecords.empty() && BlockInfoRecords.back().BlockID == BlockID)
+      return &BlockInfoRecords.back();
+
+    for (unsigned i = 0, e = static_cast<unsigned>(BlockInfoRecords.size());
+         i != e; ++i)
+      if (BlockInfoRecords[i].BlockID == BlockID)
+        return &BlockInfoRecords[i];
+    return 0;
+  }
+
+  BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
+    if (const BlockInfo *BI = getBlockInfo(BlockID))
+      return *const_cast<BlockInfo*>(BI);
+
+    // Otherwise, add a new record.
+    BlockInfoRecords.push_back(BlockInfo());
+    BlockInfoRecords.back().BlockID = BlockID;
+    return BlockInfoRecords.back();
+  }
+};
+
+
+/// NaClBitstreamEntry - When advancing through a bitstream cursor,
+/// each advance can discover a few different kinds of entries:
+///   Error    - Malformed bitcode was found.
+///   EndBlock - We've reached the end of the current block, (or the end of the
+///              file, which is treated like a series of EndBlock records.
+///   SubBlock - This is the start of a new subblock of a specific ID.
+///   Record   - This is a record with a specific AbbrevID.
+///
+struct NaClBitstreamEntry {
+  enum {
+    Error,
+    EndBlock,
+    SubBlock,
+    Record
+  } Kind;
+
+  unsigned ID;
+
+  static NaClBitstreamEntry getError() {
+    NaClBitstreamEntry E; E.Kind = Error; return E;
+  }
+  static NaClBitstreamEntry getEndBlock() {
+    NaClBitstreamEntry E; E.Kind = EndBlock; return E;
+  }
+  static NaClBitstreamEntry getSubBlock(unsigned ID) {
+    NaClBitstreamEntry E; E.Kind = SubBlock; E.ID = ID; return E;
+  }
+  static NaClBitstreamEntry getRecord(unsigned AbbrevID) {
+    NaClBitstreamEntry E; E.Kind = Record; E.ID = AbbrevID; return E;
+  }
+};
+
+/// Models default view of a bitcode record.
+typedef SmallVector<uint64_t, 8> NaClBitcodeRecordVector;
+
+/// Class NaClAbbrevListener is used to allow instances of class
+/// NaClBitcodeParser to listen to record details when processing
+/// abbreviations. The major reason for using a listener is that the
+/// NaCl bitcode reader would require a major rewrite (including the
+/// introduction of more overhead) if we were to lift abbreviations up
+/// to the bitcode reader. That is, not only would we have to lift the
+/// block processing up into the readers (i.e. many blocks in
+/// NaClBitcodeReader and NaClBitcodeParser), but add many new API's
+/// to allow the readers to update internals of the bit stream reader
+/// appropriately.
+class NaClAbbrevListener {
+  NaClAbbrevListener(const NaClAbbrevListener&) LLVM_DELETED_FUNCTION;
+  void operator=(const NaClAbbrevListener&) LLVM_DELETED_FUNCTION;
+public:
+  NaClAbbrevListener() {}
+  virtual ~NaClAbbrevListener() {}
+
+  /// Called to process the read abbreviation.
+  virtual void ProcessAbbreviation(NaClBitCodeAbbrev *Abbrev,
+                                   bool IsLocal) = 0;
+
+  /// Called after entering block. NumWords is the number of words
+  /// in the block.
+  virtual void BeginBlockInfoBlock(unsigned NumWords) = 0;
+
+  /// Called if a naclbitc::BLOCKINFO_CODE_SETBID record is found in
+  /// NaClBitstreamCursor::ReadBlockInfoBlock.
+  virtual void SetBID() = 0;
+
+  /// Called just before an EndBlock record is processed by
+  /// NaClBitstreamCursor::ReadBlockInfoBlock
+  virtual void EndBlockInfoBlock() = 0;
+
+  /// The values of the bitcode record associated with the called
+  /// virtual function.
+  NaClBitcodeRecordVector Values;
+
+  /// Start bit for current record being processed in
+  /// NaClBitstreamCursor::ReadBlockInfoBlock.
+  uint64_t StartBit;
+};
+
+/// NaClBitstreamCursor - This represents a position within a bitcode
+/// file.  There may be multiple independent cursors reading within
+/// one bitstream, each maintaining their own local state.
+///
+/// Unlike iterators, NaClBitstreamCursors are heavy-weight objects
+/// that should not be passed by value.
+class NaClBitstreamCursor {
+  friend class Deserializer;
+  NaClBitstreamReader *BitStream;
+  size_t NextChar;
+
+  // The size of the bitcode. 0 if we don't know it yet.
+  size_t Size;
+
+  /// CurWord/word_t - This is the current data we have pulled from the stream
+  /// but have not returned to the client.  This is specifically and
+  /// intentionally defined to follow the word size of the host machine for
+  /// efficiency.  We use word_t in places that are aware of this to make it
+  /// perfectly explicit what is going on.
+  typedef uint32_t word_t;
+  word_t CurWord;
+
+  /// BitsInCurWord - This is the number of bits in CurWord that are valid. This
+  /// is always from [0...31/63] inclusive (depending on word size).
+  unsigned BitsInCurWord;
+
+  // CurCodeSize - This is the declared size of code values used for the current
+  // block, in bits.
+  NaClBitcodeSelectorAbbrev CurCodeSize;
+
+  /// CurAbbrevs - Abbrevs installed at in this block.
+  std::vector<NaClBitCodeAbbrev*> CurAbbrevs;
+
+  struct Block {
+    NaClBitcodeSelectorAbbrev PrevCodeSize;
+    std::vector<NaClBitCodeAbbrev*> PrevAbbrevs;
+    Block() : PrevCodeSize() {}
+    explicit Block(const NaClBitcodeSelectorAbbrev& PCS)
+        : PrevCodeSize(PCS) {}
+  };
+
+  /// BlockScope - This tracks the codesize of parent blocks.
+  SmallVector<Block, 8> BlockScope;
+
+  NaClBitstreamCursor(const NaClBitstreamCursor &) LLVM_DELETED_FUNCTION;
+  NaClBitstreamCursor &operator=(const NaClBitstreamCursor &) LLVM_DELETED_FUNCTION;
+
+public:
+  NaClBitstreamCursor() {
+    init(nullptr);
+  }
+
+  explicit NaClBitstreamCursor(NaClBitstreamReader &R) { init(&R); }
+
+  void init(NaClBitstreamReader *R) {
+    freeState();
+    BitStream = R;
+    NextChar = (BitStream == nullptr) ? 0 : BitStream->getInitialAddress();
+    Size = 0;
+    BitsInCurWord = 0;
+  }
+
+  ~NaClBitstreamCursor() {
+    freeState();
+  }
+
+  void freeState();
+
+  bool canSkipToPos(size_t pos) const {
+    // pos can be skipped to if it is a valid address or one byte past the end.
+    return pos == 0 || BitStream->getBitcodeBytes().isValidAddress(
+        static_cast<uint64_t>(pos - 1));
+  }
+
+  bool AtEndOfStream() {
+    if (BitsInCurWord != 0)
+      return false;
+    if (Size != 0 && Size == NextChar)
+      return true;
+    fillCurWord();
+    return BitsInCurWord == 0;
+  }
+
+  /// getAbbrevIDWidth - Return the number of bits used to encode an abbrev #.
+  unsigned getAbbrevIDWidth() const { return CurCodeSize.NumBits; }
+
+  /// GetCurrentBitNo - Return the bit # of the bit we are reading.
+  uint64_t GetCurrentBitNo() const {
+    return NextChar*CHAR_BIT - BitsInCurWord;
+  }
+
+  NaClBitstreamReader *getBitStreamReader() {
+    return BitStream;
+  }
+  const NaClBitstreamReader *getBitStreamReader() const {
+    return BitStream;
+  }
+
+  /// Flags that modify the behavior of advance().
+  enum {
+    /// AF_DontPopBlockAtEnd - If this flag is used, the advance() method does
+    /// not automatically pop the block scope when the end of a block is
+    /// reached.
+    AF_DontPopBlockAtEnd = 1,
+
+    /// AF_DontAutoprocessAbbrevs - If this flag is used, abbrev entries are
+    /// returned just like normal records.
+    AF_DontAutoprocessAbbrevs = 2
+  };
+
+  /// advance - Advance the current bitstream, returning the next entry in the
+  /// stream. Use the given abbreviation listener (if provided).
+  NaClBitstreamEntry advance(unsigned Flags, NaClAbbrevListener *Listener) {
+    while (1) {
+      unsigned Code = ReadCode();
+      if (Code == naclbitc::END_BLOCK) {
+        // Pop the end of the block unless Flags tells us not to.
+        if (!(Flags & AF_DontPopBlockAtEnd) && ReadBlockEnd())
+          return NaClBitstreamEntry::getError();
+        return NaClBitstreamEntry::getEndBlock();
+      }
+
+      if (Code == naclbitc::ENTER_SUBBLOCK)
+        return NaClBitstreamEntry::getSubBlock(ReadSubBlockID());
+
+      if (Code == naclbitc::DEFINE_ABBREV &&
+          !(Flags & AF_DontAutoprocessAbbrevs)) {
+        // We read and accumulate abbrev's, the client can't do anything with
+        // them anyway.
+        ReadAbbrevRecord(true, Listener);
+        continue;
+      }
+
+      return NaClBitstreamEntry::getRecord(Code);
+    }
+  }
+
+  /// advanceSkippingSubblocks - This is a convenience function for clients that
+  /// don't expect any subblocks.  This just skips over them automatically.
+  NaClBitstreamEntry advanceSkippingSubblocks(unsigned Flags = 0) {
+    while (1) {
+      // If we found a normal entry, return it.
+      NaClBitstreamEntry Entry = advance(Flags, 0);
+      if (Entry.Kind != NaClBitstreamEntry::SubBlock)
+        return Entry;
+
+      // If we found a sub-block, just skip over it and check the next entry.
+      if (SkipBlock())
+        return NaClBitstreamEntry::getError();
+    }
+  }
+
+  /// JumpToBit - Reset the stream to the specified bit number.
+  void JumpToBit(uint64_t BitNo) {
+    uintptr_t ByteNo = uintptr_t(BitNo/8) & ~(sizeof(word_t)-1);
+    unsigned WordBitNo = unsigned(BitNo & (sizeof(word_t)*8-1));
+    assert(canSkipToPos(ByteNo) && "Invalid location");
+
+    // Move the cursor to the right word.
+    NextChar = ByteNo;
+    BitsInCurWord = 0;
+
+    // Skip over any bits that are already consumed.
+    if (WordBitNo) {
+      if (sizeof(word_t) > 4)
+        Read64(WordBitNo);
+      else
+        Read(WordBitNo);
+    }
+  }
+
+  void fillCurWord() {
+    assert(Size == 0 || NextChar < (unsigned)Size);
+
+    // Read the next word from the stream.
+    uint8_t Array[sizeof(word_t)] = {0};
+
+    uint64_t BytesRead =
+        BitStream->getBitcodeBytes().readBytes(Array, sizeof(Array), NextChar);
+
+    // If we run out of data, stop at the end of the stream.
+    if (BytesRead == 0) {
+      Size = NextChar;
+      return;
+    }
+    assert(BytesRead == sizeof(Array));
+
+    // Handle big-endian byte-swapping if necessary.
+    support::detail::packed_endian_specific_integral<
+      word_t, support::little, support::unaligned> EndianValue;
+    memcpy(&EndianValue, Array, sizeof(Array));
+
+    CurWord = EndianValue;
+    NextChar += sizeof(word_t);
+    BitsInCurWord = sizeof(word_t) * 8;
+  }
+
+  uint32_t Read(unsigned NumBits) {
+    assert(NumBits && NumBits <= 32 &&
+           "Cannot return zero or more than 32 bits!");
+
+    // If the field is fully contained by CurWord, return it quickly.
+    if (BitsInCurWord >= NumBits) {
+      uint32_t R = uint32_t(CurWord) & (~0U >> (32-NumBits));
+
+      // Use a mask to avoid undefined behavior.
+      CurWord >>= (NumBits & 0x1f);
+
+      BitsInCurWord -= NumBits;
+      return R;
+    }
+
+    uint32_t R = BitsInCurWord ? uint32_t(CurWord) : 0;
+    unsigned BitsLeft = NumBits - BitsInCurWord;
+
+    fillCurWord();
+
+    // If we run out of data, stop at the end of the stream.
+    if (BitsLeft > BitsInCurWord)
+      return 0;
+
+    uint32_t R2 = uint32_t(CurWord) & (~0U >> (sizeof(word_t) * 8 - BitsLeft));
+
+    // Use a mask to avoid undefined behavior.
+    CurWord >>= (BitsLeft & 0x1f);
+
+    BitsInCurWord -= BitsLeft;
+
+    R |= uint32_t(R2 << (NumBits - BitsLeft));
+
+    return R;
+  }
+
+  uint64_t Read64(unsigned NumBits) {
+    if (NumBits <= 32) return Read(NumBits);
+
+    uint64_t V = Read(32);
+    return V | (uint64_t)Read(NumBits-32) << 32;
+  }
+
+  uint32_t ReadVBR(unsigned NumBits) {
+    uint32_t Piece = Read(NumBits);
+    if ((Piece & (1U << (NumBits-1))) == 0)
+      return Piece;
+
+    uint32_t Result = 0;
+    unsigned NextBit = 0;
+    while (1) {
+      Result |= (Piece & ((1U << (NumBits-1))-1)) << NextBit;
+
+      if ((Piece & (1U << (NumBits-1))) == 0)
+        return Result;
+
+      NextBit += NumBits-1;
+      Piece = Read(NumBits);
+    }
+  }
+
+  // ReadVBR64 - Read a VBR that may have a value up to 64-bits in size.  The
+  // chunk size of the VBR must still be <= 32 bits though.
+  uint64_t ReadVBR64(unsigned NumBits) {
+    uint32_t Piece = Read(NumBits);
+    if ((Piece & (1U << (NumBits-1))) == 0)
+      return uint64_t(Piece);
+
+    uint64_t Result = 0;
+    unsigned NextBit = 0;
+    while (1) {
+      Result |= uint64_t(Piece & ((1U << (NumBits-1))-1)) << NextBit;
+
+      if ((Piece & (1U << (NumBits-1))) == 0)
+        return Result;
+
+      NextBit += NumBits-1;
+      Piece = Read(NumBits);
+    }
+  }
+
+private:
+  void SkipToFourByteBoundary() {
+    // If word_t is 64-bits and if we've read less than 32 bits, just dump
+    // the bits we have up to the next 32-bit boundary.
+    if (sizeof(word_t) > 4 &&
+        BitsInCurWord >= 32) {
+      CurWord >>= BitsInCurWord-32;
+      BitsInCurWord = 32;
+      return;
+    }
+
+    BitsInCurWord = 0;
+  }
+public:
+
+  unsigned ReadCode() {
+    return CurCodeSize.IsFixed
+        ? Read(CurCodeSize.NumBits)
+        : ReadVBR(CurCodeSize.NumBits);
+  }
+
+  // Block header:
+  //    [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
+
+  /// ReadSubBlockID - Having read the ENTER_SUBBLOCK code, read the BlockID for
+  /// the block.
+  unsigned ReadSubBlockID() {
+    return ReadVBR(naclbitc::BlockIDWidth);
+  }
+
+  /// SkipBlock - Having read the ENTER_SUBBLOCK abbrevid and a BlockID, skip
+  /// over the body of this block.  If the block record is malformed, return
+  /// true.
+  bool SkipBlock() {
+    // Read and ignore the codelen value.  Since we are skipping this block, we
+    // don't care what code widths are used inside of it.
+    ReadVBR(naclbitc::CodeLenWidth);
+    SkipToFourByteBoundary();
+    unsigned NumFourBytes = Read(naclbitc::BlockSizeWidth);
+
+    // Check that the block wasn't partially defined, and that the offset isn't
+    // bogus.
+    size_t SkipTo = GetCurrentBitNo() + NumFourBytes*4*8;
+    if (AtEndOfStream() || !canSkipToPos(SkipTo/8))
+      return true;
+
+    JumpToBit(SkipTo);
+    return false;
+  }
+
+  /// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter
+  /// the block, and return true if the block has an error.
+  bool EnterSubBlock(unsigned BlockID, unsigned *NumWordsP = 0);
+
+  bool ReadBlockEnd() {
+    if (BlockScope.empty()) return true;
+
+    // Block tail:
+    //    [END_BLOCK, <align4bytes>]
+    SkipToFourByteBoundary();
+
+    popBlockScope();
+    return false;
+  }
+
+private:
+
+  void popBlockScope() {
+    CurCodeSize = BlockScope.back().PrevCodeSize;
+
+    // Delete abbrevs from popped scope.
+    for (unsigned i = 0, e = static_cast<unsigned>(CurAbbrevs.size());
+         i != e; ++i)
+      CurAbbrevs[i]->dropRef();
+
+    BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
+    BlockScope.pop_back();
+  }
+
+  //===--------------------------------------------------------------------===//
+  // Record Processing
+  //===--------------------------------------------------------------------===//
+
+private:
+  void skipAbbreviatedField(const NaClBitCodeAbbrevOp &Op);
+
+  // Reads the next Value using the abbreviation Op. Returns true only
+  // if Op is an array (and sets Value to the number of elements in the
+  // array).
+  inline bool readRecordAbbrevField(const NaClBitCodeAbbrevOp &Op,
+                                    uint64_t &Value);
+
+  // Reads and returns the next value using the abbreviation Op,
+  // assuming Op appears after an array abbreviation.
+  inline uint64_t readArrayAbbreviatedField(const NaClBitCodeAbbrevOp &Op);
+
+  // Reads the array abbreviation Op, NumArrayElements times, putting
+  // the read values in Vals.
+  inline void readArrayAbbrev(const NaClBitCodeAbbrevOp &Op,
+                              unsigned NumArrayElements,
+                              SmallVectorImpl<uint64_t> &Vals);
+
+public:
+
+  /// getAbbrev - Return the abbreviation for the specified AbbrevId.
+  const NaClBitCodeAbbrev *getAbbrev(unsigned AbbrevID) const {
+    unsigned AbbrevNo = AbbrevID-naclbitc::FIRST_APPLICATION_ABBREV;
+    assert(AbbrevNo < CurAbbrevs.size() && "Invalid abbrev #!");
+    return CurAbbrevs[AbbrevNo];
+  }
+
+  /// skipRecord - Read the current record and discard it.
+  void skipRecord(unsigned AbbrevID);
+  
+  unsigned readRecord(unsigned AbbrevID, SmallVectorImpl<uint64_t> &Vals);
+
+  //===--------------------------------------------------------------------===//
+  // Abbrev Processing
+  //===--------------------------------------------------------------------===//
+  // IsLocal indicates where the abbreviation occurs. If it is in the
+  // BlockInfo block, IsLocal is false. In all other cases, IsLocal is
+  // true.
+  void ReadAbbrevRecord(bool IsLocal,
+                        NaClAbbrevListener *Listener);
+
+  // Skips over an abbreviation record. Duplicates code of ReadAbbrevRecord,
+  // except that no abbreviation is built.
+  void SkipAbbrevRecord();
+  
+  bool ReadBlockInfoBlock(NaClAbbrevListener *Listener);
+};
+
+} // End llvm namespace
+
+#endif