js/src/frontend/DoWhileEmitter.h
author Tooru Fujisawa <arai_a@mac.com>
Wed, 13 Mar 2019 04:29:44 +0000
changeset 521653 123ecc5c9586791c2ebae62c4a4e3cb600274975
parent 505471 66eb1f485c1a3ea81372758bc92292c9428b17cd
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_DoWhileEmitter_h
#define frontend_DoWhileEmitter_h

#include "mozilla/Attributes.h"
#include "mozilla/Maybe.h"

#include <stdint.h>

#include "frontend/BytecodeControlStructures.h"

namespace js {
namespace frontend {

struct BytecodeEmitter;

// Class for emitting bytecode for do-while loop.
//
// Usage: (check for the return value is omitted for simplicity)
//
//   `do body while (cond);`
//     DoWhileEmitter doWhile(this);
//     doWhile.emitBody(Some(offset_of_do), Some(offset_of_body));
//     emit(body);
//     doWhile.emitCond();
//     emit(cond);
//     doWhile.emitEnd();
//
class MOZ_STACK_CLASS DoWhileEmitter {
  BytecodeEmitter* bce_;

  // The source note index for SRC_DO_WHILE.
  unsigned noteIndex_ = 0;

  mozilla::Maybe<LoopControl> loopInfo_;

#ifdef DEBUG
  // The state of this emitter.
  //
  // +-------+ emitBody +------+ emitCond +------+ emitEnd  +-----+
  // | Start |--------->| Body |--------->| Cond |--------->| End |
  // +-------+          +------+          +------+          +-----+
  enum class State {
    // The initial state.
    Start,

    // After calling emitBody.
    Body,

    // After calling emitCond.
    Cond,

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

 public:
  explicit DoWhileEmitter(BytecodeEmitter* bce);

  // Parameters are the offset in the source code for each character below:
  //
  //   do { ... } while ( x < 20 );
  //   ^  ^
  //   |  |
  //   |  bodyPos
  //   |
  //   doPos
  //
  // Can be Nothing() if not available.
  MOZ_MUST_USE bool emitBody(const mozilla::Maybe<uint32_t>& doPos,
                             const mozilla::Maybe<uint32_t>& bodyPos);
  MOZ_MUST_USE bool emitCond();
  MOZ_MUST_USE bool emitEnd();
};

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

#endif /* frontend_DoWhileEmitter_h */