js/src/frontend/DefaultEmitter.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/DefaultEmitter.h"
   8
   9 #include "mozilla/Assertions.h"  // MOZ_ASSERT
  10
  11 #include "frontend/BytecodeEmitter.h"  // BytecodeEmitter
  12 #include "vm/Opcodes.h"                // JSOp
  13
  14 using namespace js;
  15 using namespace js::frontend;
  16
  17 using mozilla::Nothing;
  18
  19 DefaultEmitter::DefaultEmitter(BytecodeEmitter* bce) : bce_(bce) {}
  20
  21 bool DefaultEmitter::prepareForDefault() {
  22   MOZ_ASSERT(state_ == State::Start);
  23
  24   //                [stack] VALUE
  25
  26   ifUndefined_.emplace(bce_);
  27   if (!ifUndefined_->emitIf(Nothing())) {
  28     return false;
  29   }
  30
  31   if (!bce_->emit1(JSOp::Dup)) {
  32     //              [stack] VALUE VALUE
  33     return false;
  34   }
  35   if (!bce_->emit1(JSOp::Undefined)) {
  36     //              [stack] VALUE VALUE UNDEFINED
  37     return false;
  38   }
  39   if (!bce_->emit1(JSOp::StrictEq)) {
  40     //              [stack] VALUE EQ?
  41     return false;
  42   }
  43
  44   if (!ifUndefined_->emitThen()) {
  45     //              [stack] VALUE
  46     return false;
  47   }
  48
  49   if (!bce_->emit1(JSOp::Pop)) {
  50     //              [stack]
  51     return false;
  52   }
  53
  54 #ifdef DEBUG
  55   state_ = State::Default;
  56 #endif
  57   return true;
  58 }
  59
  60 bool DefaultEmitter::emitEnd() {
  61   MOZ_ASSERT(state_ == State::Default);
  62
  63   //                [stack] DEFAULTVALUE
  64
  65   if (!ifUndefined_->emitEnd()) {
  66     //              [stack] VALUE/DEFAULTVALUE
  67     return false;
  68   }
  69   ifUndefined_.reset();
  70
  71 #ifdef DEBUG
  72   state_ = State::End;
  73 #endif
  74   return true;
  75 }