Class NullIndicatorOffset

be/src/runtime/descriptors.h:92–117

Location information for null indicator bit for particular slot. For non-nullable slots, the byte_offset will be 0 and the bit_mask will be 0. This allows us to do the NullIndicatorOffset operations (tuple + byte_offset &/| bit_mask) regardless of whether the slot is nullable or not. This is more efficient than branching to check if the slot is non-nullable. ToIR() generates a constant version of

/// ToIR() generates a constant version of this struct in LLVM IR. If the struct
/// layout is updated, then ToIR() must also be updated.
struct NullIndicatorOffset {
  int byte_offset;
  uint8_t bit_mask;  /// to extract null indicator

  NullIndicatorOffset(int byte_offset = 0, int bit_offset = -1)
    : byte_offset(byte_offset),
      bit_mask(bit_offset == -1 ? 0 : 1 << bit_offset) {
  }

  bool Equals(const NullIndicatorOffset& o) const {
    return this->byte_offset == o.byte_offset && this->bit_mask == o.bit_mask;
  }

  std::string DebugString() const;

  // Generates an LLVM IR constant of this offset. Needs to be updated if the layout of
  // this struct changes.
  llvm::Constant* ToIR(LlvmCodeGen* codegen) const;

  // Generates a packed i64 constant of this offset. This can be used when passing a
  // constant offset to a function which expects it as a packed i64. Needs to be updated
  // if the layout of this struct changes.
  llvm::Constant* ToIRPacked(LlvmCodeGen* codegen) const;

  static const char* LLVM_CLASS_NAME;
};

std::ostream& operator<<(std::ostream& os, const NullIndicatorOffset& null_indicator);