ExpressionStatementEmitter.h

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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_ExpressionStatementEmitter_h

#define frontend_ExpressionStatementEmitter_h

#include "mozilla/Attributes.h"

#include <stdint.h>

#include "frontend/ValueUsage.h"

namespace js {

namespace frontend {

struct BytecodeEmitter;

// Class for emitting bytecode for expression statement.

//

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

//

//   `expr;`

//     // IgnoreValue if this is in normal script.

//     // WantValue if this is in eval script.

//     ValueUsage valueUsage = ...;

//

//     ExpressionStatementEmitter ese(this, valueUsage);

//     ese.prepareForExpr(offset_of_expr);

//     emit(expr);

//     ese.emitEnd();

//

class MOZ_STACK_CLASS ExpressionStatementEmitter {

  BytecodeEmitter* bce_;

#ifdef DEBUG

  // The stack depth before emitting expression.

  int32_t depth_;

#endif

  // The usage of the value of the expression.

  ValueUsage valueUsage_;

#ifdef DEBUG

  // The state of this emitter.

//

  // +-------+ prepareForExpr +------+ emitEnd +-----+

  // | Start |--------------->| Expr |-------->| End |

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

  enum class State {

    // The initial state.

    Start,

    // After calling prepareForExpr.

    Expr,

    // After calling emitEnd.

End

};

  State state_ = State::Start;

#endif

 public:

  ExpressionStatementEmitter(BytecodeEmitter* bce, ValueUsage valueUsage);

  // Parameters are the offset in the source code for each character below:

//

  //   expr;

  //   ^

  //   |

  //   beginPos

  [[nodiscard]] bool prepareForExpr(uint32_t beginPos);

  [[nodiscard]] bool emitEnd();

};

}  // namespace frontend

}  // namespace js

#endif /* frontend_ExpressionStatementEmitter_h */