BitCodes.h

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//===- 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 {
    BLOCKINFO_CODE_SETBID = 1  // SETBID: [blockid#]
    // DEFINE_ABBREV has magic semantics here, applying to the current SETBID'd
    // block, instead of the BlockInfo block.
    // BLOCKNAME: give string name to block, if desired.
  };
  
} // 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._].
  };
    
  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:
      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