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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

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#ifndef CPU_S390_RELOCINFO_S390_HPP

#define CPU_S390_RELOCINFO_S390_HPP

//----------------------------

//  relocInfo layout

//----------------------------

// This description should be contained in code/relocInfo.hpp

// but was put here to minimize shared code diffs.

// Relocation information for a nmethod is stored in compressed

// form in an array of element type short int (16 bits).

// Each array element constitutes one relocInfo record.

// The layout of one such record is described here.

// +------------+---+---+------------------------------+

// |    type    |  fmt  |      offset/offset_unit      |

// +------------+---+---+------------------------------+

//

// |<-- value_width (16) ----------------------------->|

// |<type_width>|<-- nontype_width (12) -------------->|

//      (4)

// |            |<--+-->|<-- offset_width (10) ------->|

//              /       \

//             /   (2)   \

//            /<--format->\

//            |    width  |

// only for type == data_prefix_tag:

// +------------+---+---+------------------------------+

// |    type    |   |              data                |

// +------------+---+---+------------------------------+

// |     15     |<->|<-- datalen_width (11) ---------->|

//                |

//                +--datalen_tag (1)

// relocType

//   The type field holds a value of relocType (which is

//   an enum of all possible relocation types). Currently,

//   there are 16 distinct relocation types, requiring

//   type_width to be (at least) 4.

// relocFormat

//   The format field holds a value of relocFormat (which is

//   an enum of all possible relocation formats). Currently,

//   there are 4 distinct relocation formats, requiring

//   format_width to be (at least) 2.

// offset

//   Each relocInfo is related to one specific address in the CodeBlob.

//   The address always points to the first byte of the target instruction.

//   It does NOT refer directly to the relocation subfield or embedded constant.

//   offset contains the distance of this relocInfo from the previous one.

//   offset is scaled by offset_unit (the platform-specific instruction

//   alignment requirement) to maximize the encodable distance.

//   To obtain the absolute address in the CodeBlob the relocInfo is

//   related to, you have to iterate over all relocInfos from the

//   beginning, and then use RelocIterator::addr() to get the address.

// relocType == data_prefix_tag

//   These are relocInfo records containing inline data that belongs to

//   the next non-data relocInfo record. Usage of that inline data is

//   specific and private to that relocInfo record.

//   For details refer to code/relocInfo.hpp

  // machine-dependent parts of class relocInfo

 private:

  enum {

    // Instructions are HW (2-byte) aligned on z/Architecture.

    offset_unit        =  2,

    // Encodes Assembler::disp32_operand vs. Assembler::imm64_operand.

    // (Assembler::call32_operand is used on call instructions only.)

    format_width       =  2

  };

 public:

  enum relocFormat {

    no_format           = 0,

    uncompressed_format = 0,  // Relocation is for a regular oop.

    compressed_format   = 1,  // Relocation is for a narrow (compressed) oop or klass.

                              // Similar to relocInfo::narrow_oop_in_const.

    pcrel_addr_format   = 2,  // Relocation is for the target LOCATION of a pc-relative instruction.

    pcrel_data_format   = 3   // Relocation is for the target data of a pc-relative instruction.

  };

  // This platform has no oops in the code that are not also

  // listed in the oop section.

  static bool mustIterateImmediateOopsInCode() { return false; }

  // Store the new target address into an oop_Relocation cell, if any.

  // Return indication if update happened.

  static bool update_oop_pool(address begin, address end, address newTarget, CodeBlob* cb);

#endif // CPU_S390_RELOCINFO_S390_HPP