ForOfEmitter.h - mozsearch

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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_ForOfEmitter_h

#define frontend_ForOfEmitter_h

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

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

#include <stdint.h>  // int32_t

#include "frontend/ForOfLoopControl.h"  // ForOfLoopControl

#include "frontend/IteratorKind.h"      // IteratorKind

#include "frontend/SelfHostedIter.h"    // SelfHostedIter

#include "frontend/TDZCheckCache.h"     // TDZCheckCache

namespace js {

namespace frontend {

struct BytecodeEmitter;

class EmitterScope;

// Class for emitting bytecode for for-of loop.

//

// Usage: (check for the return value is omitted for simplicity)

//

//   `for (init of iterated) body`

//     // headLexicalEmitterScope: lexical scope for init

//     ForOfEmitter forOf(this, headLexicalEmitterScope);

//     forOf.emitIterated();

//     emit(iterated);

//     forOf.emitInitialize(offset_of_for);

//     emit(init);

//     forOf.emitBody();

//     emit(body);

//     forOf.emitEnd(offset_of_iterated);

//

class MOZ_STACK_CLASS ForOfEmitter {

  BytecodeEmitter* bce_;

#ifdef DEBUG

  // The stack depth before emitting IteratorNext code inside loop.

  int32_t loopDepth_ = 0;

#endif

  SelfHostedIter selfHostedIter_;

  IteratorKind iterKind_;

  mozilla::Maybe<ForOfLoopControl> loopInfo_;

  // The lexical scope to be freshened for each iteration.

  // See the comment in `emitBody` for more details.

  const EmitterScope* headLexicalEmitterScope_;

  // Cache for the iterated value.

  // (The cache for the iteration body is inside `loopInfo_`)

  mozilla::Maybe<TDZCheckCache> tdzCacheForIteratedValue_;

#ifdef DEBUG

  // The state of this emitter.

//

  // +-------+ emitIterated +----------+ emitInitialize +------------+

  // | Start |------------->| Iterated |--------------->| Initialize |-+

  // +-------+              +----------+                +------------+ |

  //                                                                   |

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

  //                                |

  //                                | emitBody +------+ emitEnd  +-----+

  //                                +----------| Body |--------->| End |

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

  enum class State {

    // The initial state.

    Start,

    // After calling emitIterated.

    Iterated,

    // After calling emitInitialize.

    Initialize,

    // After calling emitBody.

    Body,

    // After calling emitEnd.

End

};

  State state_ = State::Start;

#endif

 public:

  ForOfEmitter(BytecodeEmitter* bce,

               const EmitterScope* headLexicalEmitterScope,

               SelfHostedIter selfHostedIter, IteratorKind iterKind);

  // The offset in the source code for each character below:

//

  //   for ( var x of obj ) { ... }

  //   ^              ^

  //   |              |

  //   |              iteratedPos

  //   |

  //   forPos

  [[nodiscard]] bool emitIterated();

  [[nodiscard]] bool emitInitialize(uint32_t forPos);

  [[nodiscard]] bool emitBody();

  [[nodiscard]] bool emitEnd(uint32_t iteratedPos);

};

} /* namespace frontend */

} /* namespace js */

#endif /* frontend_ForOfEmitter_h */