tor-browser

ElemOpEmitter.cpp (6520B)

---

/* -*- 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/ElemOpEmitter.h"

#include "frontend/BytecodeEmitter.h"
#include "frontend/SharedContext.h"
#include "vm/Opcodes.h"
#include "vm/ThrowMsgKind.h"  // ThrowMsgKind

using namespace js;
using namespace js::frontend;

ElemOpEmitter::ElemOpEmitter(BytecodeEmitter* bce, Kind kind, ObjKind objKind)
   : bce_(bce), kind_(kind), objKind_(objKind) {}

bool ElemOpEmitter::prepareForObj() {
 MOZ_ASSERT(state_ == State::Start);

#ifdef DEBUG
 state_ = State::Obj;
#endif
 return true;
}

bool ElemOpEmitter::prepareForKey() {
 MOZ_ASSERT(state_ == State::Obj);

 if (isCall()) {
   if (!bce_->emit1(JSOp::Dup)) {
     //            [stack] # if Super
     //            [stack] THIS THIS
     //            [stack] # otherwise
     //            [stack] OBJ OBJ
     return false;
   }
 }

#ifdef DEBUG
 state_ = State::Key;
#endif
 return true;
}

bool ElemOpEmitter::emitGet() {
 MOZ_ASSERT(state_ == State::Key);

 if (isSuper()) {
   if (!bce_->emitSuperBase()) {
     //            [stack] THIS? THIS KEY SUPERBASE
     return false;
   }
 }

 // Inc/dec and compound assignment use the KEY twice, but if it's an object,
 // it must be converted by ToPropertyKey only once, per spec.
 if (isIncDec() || isCompoundAssignment()) {
   if (isSuper()) {
     if (!bce_->emit1(JSOp::Swap)) {
       //          [stack] THIS SUPERBASE KEY
       return false;
     }
     if (!bce_->emit1(JSOp::ToPropertyKey)) {
       //          [stack] THIS SUPERBASE KEY
       return false;
     }
     if (!bce_->emit1(JSOp::Swap)) {
       //          [stack] THIS KEY SUPERBASE
       return false;
     }
     if (!bce_->emitDupAt(2, 3)) {
       //          [stack] THIS KEY SUPERBASE THIS KEY SUPERBASE
       return false;
     }
   } else {
     if (!bce_->emit1(JSOp::ToPropertyKey)) {
       //          [stack] OBJ KEY
       return false;
     }
     if (!bce_->emit1(JSOp::Dup2)) {
       //          [stack] OBJ KEY OBJ KEY
       return false;
     }
   }
 }

 JSOp op;
 if (isSuper()) {
   op = JSOp::GetElemSuper;
 } else {
   op = JSOp::GetElem;
 }
 if (!bce_->emitElemOpBase(op)) {
   //              [stack] # if Get
   //              [stack] ELEM
   //              [stack] # if Call
   //              [stack] THIS ELEM
   //              [stack] # if Inc/Dec/Assignment, with Super
   //              [stack] THIS KEY SUPERBASE ELEM
   //              [stack] # if Inc/Dec/Assignment, other
   //              [stack] OBJ KEY ELEM
   return false;
 }
 if (isCall()) {
   if (!bce_->emit1(JSOp::Swap)) {
     //            [stack] ELEM THIS
     return false;
   }
 }

#ifdef DEBUG
 state_ = State::Get;
#endif
 return true;
}

bool ElemOpEmitter::prepareForRhs() {
 MOZ_ASSERT(isSimpleAssignment() || isPropInit() || isCompoundAssignment());
 MOZ_ASSERT_IF(isSimpleAssignment() || isPropInit(), state_ == State::Key);
 MOZ_ASSERT_IF(isCompoundAssignment(), state_ == State::Get);

 if (isSimpleAssignment() || isPropInit()) {
   // For CompoundAssignment, SuperBase is already emitted by emitGet.
   if (isSuper()) {
     if (!bce_->emitSuperBase()) {
       //          [stack] THIS KEY SUPERBASE
       return false;
     }
   }
 }

#ifdef DEBUG
 state_ = State::Rhs;
#endif
 return true;
}

bool ElemOpEmitter::emitDelete() {
 MOZ_ASSERT(state_ == State::Key);
 MOZ_ASSERT(isDelete());

 if (isSuper()) {
   if (!bce_->emitSuperBase()) {
     //            [stack] THIS KEY SUPERBASE
     return false;
   }

   // Unconditionally throw when attempting to delete a super-reference.
   if (!bce_->emit2(JSOp::ThrowMsg, uint8_t(ThrowMsgKind::CantDeleteSuper))) {
     //            [stack] THIS KEY SUPERBASE
     return false;
   }

   // Another wrinkle: Balance the stack from the emitter's point of view.
   // Execution will not reach here, as the last bytecode threw.
   if (!bce_->emitPopN(2)) {
     //            [stack] THIS
     return false;
   }
 } else {
   JSOp op = bce_->sc->strict() ? JSOp::StrictDelElem : JSOp::DelElem;
   if (!bce_->emitElemOpBase(op)) {
     // SUCCEEDED
     return false;
   }
 }

#ifdef DEBUG
 state_ = State::Delete;
#endif
 return true;
}

bool ElemOpEmitter::emitAssignment() {
 MOZ_ASSERT(isSimpleAssignment() || isPropInit() || isCompoundAssignment());
 MOZ_ASSERT(state_ == State::Rhs);

 MOZ_ASSERT_IF(isPropInit(), !isSuper());

 JSOp setOp = isPropInit() ? JSOp::InitElem
              : isSuper()  ? bce_->sc->strict() ? JSOp::StrictSetElemSuper
                                                : JSOp::SetElemSuper
              : bce_->sc->strict() ? JSOp::StrictSetElem
                                   : JSOp::SetElem;
 if (!bce_->emitElemOpBase(setOp)) {
   //              [stack] ELEM
   return false;
 }

#ifdef DEBUG
 state_ = State::Assignment;
#endif
 return true;
}

bool ElemOpEmitter::emitIncDec(ValueUsage valueUsage) {
 MOZ_ASSERT(state_ == State::Key);
 MOZ_ASSERT(isIncDec());

 if (!emitGet()) {
   //              [stack] ... ELEM
   return false;
 }

 MOZ_ASSERT(state_ == State::Get);

 JSOp incOp = isInc() ? JSOp::Inc : JSOp::Dec;
 if (!bce_->emit1(JSOp::ToNumeric)) {
   //              [stack] ... N
   return false;
 }
 if (isPostIncDec() && valueUsage == ValueUsage::WantValue) {
   //              [stack] OBJ KEY SUPERBASE? N
   if (!bce_->emit1(JSOp::Dup)) {
     //            [stack] ... N N
     return false;
   }
   if (!bce_->emit2(JSOp::Unpick, 3 + isSuper())) {
     //            [stack] N OBJ KEY SUPERBASE? N
     return false;
   }
 }
 if (!bce_->emit1(incOp)) {
   //              [stack] ... N+1
   return false;
 }

 JSOp setOp =
     isSuper()
         ? (bce_->sc->strict() ? JSOp::StrictSetElemSuper : JSOp::SetElemSuper)
         : (bce_->sc->strict() ? JSOp::StrictSetElem : JSOp::SetElem);
 if (!bce_->emitElemOpBase(setOp)) {
   //              [stack] N? N+1
   return false;
 }
 if (isPostIncDec() && valueUsage == ValueUsage::WantValue) {
   if (!bce_->emit1(JSOp::Pop)) {
     //            [stack] N
     return false;
   }
 }

#ifdef DEBUG
 state_ = State::IncDec;
#endif
 return true;
}