text: //===- BitCodes.h - Enum values for the bitcode format ----------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This header Bitcode enum values.
  //
  // The enum values defined in this file should be considered permanent.  If
  // new features are added, they should have values added at the end of the
  // respective lists.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_BITCODE_BITCODES_H
  #define LLVM_BITCODE_BITCODES_H
  
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/Support/DataTypes.h"
  #include <cassert>
  
  namespace llvm {
  namespace bitc {
    enum StandardWidths {
      BlockIDWidth = 8,  // We use VBR-8 for block IDs.
      CodeLenWidth = 4,  // Codelen are VBR-4.
      BlockSizeWidth = 32  // BlockSize up to 2^32 32-bit words = 16GB per block.
    };
  
    // The standard abbrev namespace always has a way to exit a block, enter a
    // nested block, define abbrevs, and define an unabbreviated record.
    enum FixedAbbrevIDs {
      END_BLOCK = 0,  // Must be zero to guarantee termination for broken bitcode.
      ENTER_SUBBLOCK = 1,
  
      /// DEFINE_ABBREV - Defines an abbrev for the current block.  It consists
      /// of a vbr5 for # operand infos.  Each operand info is emitted with a
      /// single bit to indicate if it is a literal encoding.  If so, the value is
      /// emitted with a vbr8.  If not, the encoding is emitted as 3 bits followed
      /// by the info value as a vbr5 if needed.
      DEFINE_ABBREV = 2,
  
      // UNABBREV_RECORDs are emitted with a vbr6 for the record code, followed by
      // a vbr6 for the # operands, followed by vbr6's for each operand.
      UNABBREV_RECORD = 3,
  
      // This is not a code, this is a marker for the first abbrev assignment.
      FIRST_APPLICATION_ABBREV = 4
    };
  
    /// StandardBlockIDs - All bitcode files can optionally include a BLOCKINFO
    /// block, which contains metadata about other blocks in the file.
    enum StandardBlockIDs {
      /// BLOCKINFO_BLOCK is used to define metadata about blocks, for example,
      /// standard abbrevs that should be available to all blocks of a specified
      /// ID.
      BLOCKINFO_BLOCK_ID = 0,
  
      // Block IDs 1-7 are reserved for future expansion.
      FIRST_APPLICATION_BLOCKID = 8
    };
  
    /// BlockInfoCodes - The blockinfo block contains metadata about user-defined
    /// blocks.
    enum BlockInfoCodes {
      // DEFINE_ABBREV has magic semantics here, applying to the current SETBID'd
      // block, instead of the BlockInfo block.
      
      BLOCKINFO_CODE_SETBID = 1,       // SETBID: [blockid#]
      BLOCKINFO_CODE_BLOCKNAME = 2,    // BLOCKNAME: [name]
      BLOCKINFO_CODE_SETRECORDNAME = 3 // BLOCKINFO_CODE_SETRECORDNAME: [id, name]
    };
  
  } // End bitc namespace
  
  /// BitCodeAbbrevOp - This describes one or more operands in an abbreviation.
  /// This is actually a union of two different things:
  ///   1. It could be a literal integer value ("the operand is always 17").
  ///   2. It could be an encoding specification ("this operand encoded like so").
  ///
  class BitCodeAbbrevOp {
    uint64_t Val;           // A literal value or data for an encoding.
    bool IsLiteral : 1;     // Indicate whether this is a literal value or not.
    unsigned Enc   : 3;     // The encoding to use.
  public:
    enum Encoding {
      Fixed = 1,  // A fixed width field, Val specifies number of bits.
      VBR   = 2,  // A VBR field where Val specifies the width of each chunk.
      Array = 3,  // A sequence of fields, next field species elt encoding.
      Char6 = 4,  // A 6-bit fixed field which maps to [a-zA-Z0-9._].
      Blob  = 5   // 32-bit aligned array of 8-bit characters.
    };
  
    explicit BitCodeAbbrevOp(uint64_t V) :  Val(V), IsLiteral(true) {}
    explicit BitCodeAbbrevOp(Encoding E, uint64_t Data = 0)
      : Val(Data), IsLiteral(false), Enc(E) {}
  
    bool isLiteral() const { return IsLiteral; }
    bool isEncoding() const { return !IsLiteral; }
  
    // Accessors for literals.
    uint64_t getLiteralValue() const { assert(isLiteral()); return Val; }
  
    // Accessors for encoding info.
    Encoding getEncoding() const { assert(isEncoding()); return (Encoding)Enc; }
    uint64_t getEncodingData() const {
      assert(isEncoding() && hasEncodingData());
      return Val;
    }
  
    bool hasEncodingData() const { return hasEncodingData(getEncoding()); }
    static bool hasEncodingData(Encoding E) {
      switch (E) {
      default: assert(0 && "Unknown encoding");
      case Fixed:
      case VBR:
        return true;
      case Array:
      case Char6:
      case Blob:
        return false;
      }
    }
  
    /// isChar6 - Return true if this character is legal in the Char6 encoding.
    static bool isChar6(char C) {
      if (C >= 'a' && C <= 'z') return true;
      if (C >= 'A' && C <= 'Z') return true;
      if (C >= '0' && C <= '9') return true;
      if (C == '.' || C == '_') return true;
      return false;
    }
    static unsigned EncodeChar6(char C) {
      if (C >= 'a' && C <= 'z') return C-'a';
      if (C >= 'A' && C <= 'Z') return C-'A'+26;
      if (C >= '0' && C <= '9') return C-'0'+26+26;
      if (C == '.') return 62;
      if (C == '_') return 63;
      assert(0 && "Not a value Char6 character!");
      return 0;
    }
  
    static char DecodeChar6(unsigned V) {
      assert((V & ~63) == 0 && "Not a Char6 encoded character!");
      if (V < 26) return V+'a';
      if (V < 26+26) return V-26+'A';
      if (V < 26+26+10) return V-26-26+'0';
      if (V == 62) return '.';
      if (V == 63) return '_';
      assert(0 && "Not a value Char6 character!");
      return ' ';
    }
  
  };
  
  /// BitCodeAbbrev - This class represents an abbreviation record.  An
  /// abbreviation allows a complex record that has redundancy to be stored in a
  /// specialized format instead of the fully-general, fully-vbr, format.
  class BitCodeAbbrev {
    SmallVector<BitCodeAbbrevOp, 8> OperandList;
    unsigned char RefCount; // Number of things using this.
    ~BitCodeAbbrev() {}
  public:
    BitCodeAbbrev() : RefCount(1) {}
  
    void addRef() { ++RefCount; }
    void dropRef() { if (--RefCount == 0) delete this; }
  
    unsigned getNumOperandInfos() const {
      return static_cast<unsigned>(OperandList.size());
    }
    const BitCodeAbbrevOp &getOperandInfo(unsigned N) const {
      return OperandList[N];
    }
  
    void Add(const BitCodeAbbrevOp &OpInfo) {
      OperandList.push_back(OpInfo);
    }
  };
  } // End llvm namespace
  
  #endif
  