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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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/ForInEmitter.h"

#include "frontend/BytecodeEmitter.h"
#include "frontend/EmitterScope.h"
#include "frontend/SourceNotes.h"
#include "vm/Opcodes.h"
#include "vm/Scope.h"

using namespace js;
using namespace js::frontend;

using mozilla::Maybe;
using mozilla::Nothing;

ForInEmitter::ForInEmitter(BytecodeEmitter* bce, const EmitterScope* headLexicalEmitterScope)
  : bce_(bce),
    headLexicalEmitterScope_(headLexicalEmitterScope)
{}

bool
ForInEmitter::emitIterated()
{
    MOZ_ASSERT(state_ == State::Start);
    tdzCacheForIteratedValue_.emplace(bce_);

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

bool
ForInEmitter::emitInitialize()
{
    MOZ_ASSERT(state_ == State::Iterated);
    tdzCacheForIteratedValue_.reset();

    if (!bce_->emit1(JSOP_ITER))                      // ITER
        return false;

    // For-in loops have both the iterator and the value on the stack. Push
    // undefined to balance the stack.
    if (!bce_->emit1(JSOP_UNDEFINED))                 // ITER ITERVAL
        return false;

    loopInfo_.emplace(bce_, StatementKind::ForInLoop);

    // Annotate so IonMonkey can find the loop-closing jump.
    if (!bce_->newSrcNote(SRC_FOR_IN, &noteIndex_))
        return false;

    // Jump down to the loop condition to minimize overhead (assuming at
    // least one iteration, just like the other loop forms).
    if (!loopInfo_->emitEntryJump(bce_))              // ITER ITERVAL
        return false;

    if (!loopInfo_->emitLoopHead(bce_, Nothing()))    // ITER ITERVAL
        return false;

    // If the loop had an escaping lexical declaration, reset the declaration's
    // bindings to uninitialized to implement TDZ semantics.
    if (headLexicalEmitterScope_) {
        // The environment chain only includes an environment for the
        // for-in loop head *if* a scope binding is captured, thereby
        // requiring recreation each iteration. If a lexical scope exists
        // for the head, it must be the innermost one. If that scope has
        // closed-over bindings inducing an environment, recreate the
        // current environment.
        MOZ_ASSERT(headLexicalEmitterScope_ == bce_->innermostEmitterScope());
        MOZ_ASSERT(headLexicalEmitterScope_->scope(bce_)->kind() == ScopeKind::Lexical);

        if (headLexicalEmitterScope_->hasEnvironment()) {
            if (!bce_->emit1(JSOP_RECREATELEXICALENV))
                return false;                         // ITER ITERVAL
        }

        // For uncaptured bindings, put them back in TDZ.
        if (!headLexicalEmitterScope_->deadZoneFrameSlots(bce_))
            return false;
    }

#ifdef DEBUG
    loopDepth_ = bce_->stackDepth;
#endif
    MOZ_ASSERT(loopDepth_ >= 2);

    if (!bce_->emit1(JSOP_ITERNEXT))                  // ITER ITERVAL
        return false;

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

bool
ForInEmitter::emitBody()
{
    MOZ_ASSERT(state_ == State::Initialize);

    MOZ_ASSERT(bce_->stackDepth == loopDepth_,
               "iterator and iterval must be left on the stack");

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

bool
ForInEmitter::emitEnd(const Maybe<uint32_t>& forPos)
{
    MOZ_ASSERT(state_ == State::Body);

    loopInfo_->setContinueTarget(bce_->offset());

    if (forPos) {
        // Make sure this code is attributed to the "for".
        if (!bce_->updateSourceCoordNotes(*forPos))
            return false;
    }

    if (!loopInfo_->emitLoopEntry(bce_, Nothing()))   // ITER ITERVAL
        return false;
    if (!bce_->emit1(JSOP_POP))                       // ITER
        return false;
    if (!bce_->emit1(JSOP_MOREITER))                  // ITER NEXTITERVAL?
        return false;
    if (!bce_->emit1(JSOP_ISNOITER))                  // ITER NEXTITERVAL? ISNOITER
        return false;

    if (!loopInfo_->emitLoopEnd(bce_, JSOP_IFEQ))     // ITER NEXTITERVAL
        return false;

    // Set the srcnote offset so we can find the closing jump.
    if (!bce_->setSrcNoteOffset(noteIndex_, SrcNote::ForIn::BackJumpOffset,
                                loopInfo_->loopEndOffsetFromEntryJump()))
    {
        return false;
    }

    if (!loopInfo_->patchBreaksAndContinues(bce_))
        return false;

    // Pop the enumeration value.
    if (!bce_->emit1(JSOP_POP))                       // ITER
        return false;

    if (!bce_->tryNoteList.append(JSTRY_FOR_IN, bce_->stackDepth, loopInfo_->headOffset(),
                                  bce_->offset()))
    {
        return false;
    }

    if (!bce_->emit1(JSOP_ENDITER))                   //
        return false;

    loopInfo_.reset();

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