ExpressionStatementEmitter.cpp

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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/. */

#include "frontend/ExpressionStatementEmitter.h"

#include "frontend/BytecodeEmitter.h"

#include "vm/Opcodes.h"

using namespace js;

using namespace js::frontend;

ExpressionStatementEmitter::ExpressionStatementEmitter(BytecodeEmitter* bce,

                                                       ValueUsage valueUsage)

    : bce_(bce), valueUsage_(valueUsage) {}

bool ExpressionStatementEmitter::prepareForExpr(uint32_t beginPos) {

  MOZ_ASSERT(state_ == State::Start);

  if (!bce_->updateSourceCoordNotes(beginPos)) {

    return false;

#ifdef DEBUG

  depth_ = bce_->bytecodeSection().stackDepth();

  state_ = State::Expr;

#endif

  return true;

bool ExpressionStatementEmitter::emitEnd() {

  MOZ_ASSERT(state_ == State::Expr);

  MOZ_ASSERT(bce_->bytecodeSection().stackDepth() == depth_ + 1);

  //                [stack] VAL

  JSOp op = valueUsage_ == ValueUsage::WantValue ? JSOp::SetRval : JSOp::Pop;

  if (!bce_->emit1(op)) {

    //              [stack] # if WantValue

    //              [stack] VAL

    //              [stack] # otherwise

    //              [stack]

    return false;

#ifdef DEBUG

  state_ = State::End;

#endif

  return true;