js/src/frontend/ExpressionStatementEmitter.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "frontend/ExpressionStatementEmitter.h"
   8
   9 #include "frontend/BytecodeEmitter.h"
  10 #include "vm/Opcodes.h"
  11
  12 using namespace js;
  13 using namespace js::frontend;
  14
  15 using mozilla::Maybe;
  16
  17 ExpressionStatementEmitter::ExpressionStatementEmitter(BytecodeEmitter* bce,
  18                                                        ValueUsage valueUsage)
  19     : bce_(bce), valueUsage_(valueUsage) {}
  20
  21 bool ExpressionStatementEmitter::prepareForExpr(uint32_t beginPos) {
  22   MOZ_ASSERT(state_ == State::Start);
  23
  24   if (!bce_->updateSourceCoordNotes(beginPos)) {
  25     return false;
  26   }
  27
  28 #ifdef DEBUG
  29   depth_ = bce_->bytecodeSection().stackDepth();
  30   state_ = State::Expr;
  31 #endif
  32   return true;
  33 }
  34
  35 bool ExpressionStatementEmitter::emitEnd() {
  36   MOZ_ASSERT(state_ == State::Expr);
  37   MOZ_ASSERT(bce_->bytecodeSection().stackDepth() == depth_ + 1);
  38
  39   //                [stack] VAL
  40
  41   JSOp op = valueUsage_ == ValueUsage::WantValue ? JSOp::SetRval : JSOp::Pop;
  42   if (!bce_->emit1(op)) {
  43     //              [stack] # if WantValue
  44     //              [stack] VAL
  45     //              [stack] # otherwise
  46     //              [stack]
  47     return false;
  48   }
  49
  50 #ifdef DEBUG
  51   state_ = State::End;
  52 #endif
  53   return true;
  54 }