js/src/frontend/LabelEmitter.h
author Tooru Fujisawa <arai_a@mac.com>
Wed, 13 Mar 2019 04:29:44 +0000
changeset 521653 123ecc5c9586791c2ebae62c4a4e3cb600274975
parent 513561 731a43e841abcdb19ffc55151cb60c49cd8c0c84
child 530282 39133aa95fce7f894c55ace40c778983c8ca26bf
permissions -rw-r--r--
Bug 1505343 - Part 1: Rename binsource => binast. r=Yoric Differential Revision: https://phabricator.services.mozilla.com/D23097

/* -*- 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_LabelEmitter_h
#define frontend_LabelEmitter_h

#include "mozilla/Attributes.h"  // MOZ_MUST_USE, MOZ_STACK_CLASS
#include "mozilla/Maybe.h"       // Maybe

#include "frontend/BytecodeControlStructures.h"  // LabelControl
#include "frontend/JumpList.h"                   // JumpList

class JSAtom;

namespace js {
namespace frontend {

struct BytecodeEmitter;

// Class for emitting labeled statement.
//
// Usage: (check for the return value is omitted for simplicity)
//
//   `label: expr;`
//     LabelEmitter le(this);
//     le.emitLabel(name_of_label);
//     emit(expr);
//     le.emitEnd();
//
class MOZ_STACK_CLASS LabelEmitter {
  BytecodeEmitter* bce_;

  // The offset of the JSOP_LABEL.
  ptrdiff_t top_ = 0;

  mozilla::Maybe<LabelControl> controlInfo_;

#ifdef DEBUG
  // The state of this emitter.
  //
  // +-------+ emitLabel +-------+ emitEnd +-----+
  // | Start |---------->| Label |-------->| End |
  // +-------+           +-------+         +-----+
  enum class State {
    // The initial state.
    Start,

    // After calling emitLabel.
    Label,

    // After calling emitEnd.
    End
  };
  State state_ = State::Start;
#endif

 public:
  explicit LabelEmitter(BytecodeEmitter* bce) : bce_(bce) {}

  MOZ_MUST_USE bool emitLabel(JSAtom* name);
  MOZ_MUST_USE bool emitEnd();
};

} /* namespace frontend */
} /* namespace js */

#endif /* frontend_LabelEmitter_h */