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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* 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 */