/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-

 * vim: set ts=8 sts=4 et sw=4 tw=99:

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef frontend_JumpList_h

#define frontend_JumpList_h

#include <stddef.h>

#include "js/TypeDecls.h"

namespace js {

namespace frontend {

// Linked list of jump instructions that need to be patched. The linked list is

// stored in the bytes of the incomplete bytecode that will be patched, so no

// extra memory is needed, and patching the instructions destroys the list.

//

// Example:

//

//     JumpList brList;

//     if (!emitJump(JSOP_IFEQ, &brList))

//         return false;

//     ...

//     JumpTarget label;

//     if (!emitJumpTarget(&label))

//         return false;

//     ...

//     if (!emitJump(JSOP_GOTO, &brList))

//         return false;

//     ...

//     patchJumpsToTarget(brList, label);

//

//                 +-> -1

//                 |

//                 |

//    ifeq ..   <+ +                +-+   ifeq ..

//    ..         |                  |     ..

//  label:       |                  +-> label:

//    jumptarget |                  |     jumptarget

//    ..         |                  |     ..

//    goto .. <+ +                  +-+   goto .. <+

//             |                                   |

//             |                                   |

//             +                                   +

//           brList                              brList

//

//       |                                  ^

//       +------- patchJumpsToTarget -------+

//

// Offset of a jump target instruction, used for patching jump instructions.

struct JumpTarget {

    ptrdiff_t offset;

};

struct JumpList {

    JumpList() {}

    // -1 is used to mark the end of jump lists.

    ptrdiff_t offset = -1;

    // Add a jump instruction to the list.

    void push(jsbytecode* code, ptrdiff_t jumpOffset);

    // Patch all jump instructions in this list to jump to `target`.  This

    // clobbers the list.

    void patchAll(jsbytecode* code, JumpTarget target);

};

} /* namespace frontend */

} /* namespace js */

#endif /* frontend_JumpList_h */