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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/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)) {
// [stack] 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)) {
// [stack] ITER ITERVAL
return false;
}
loopInfo_.emplace(bce_, StatementKind::ForInLoop);
// Annotate so IonMonkey can find the loop-closing jump.
if (!bce_->newSrcNote(SRC_FOR_IN, ¬eIndex_)) {
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_)) {
// [stack] ITER ITERVAL
return false;
}
if (!loopInfo_->emitLoopHead(bce_, Nothing())) {
// [stack] 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)) {
// [stack] ITER ITERVAL
return false;
}
}
// 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)) {
// [stack] 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())) {
// [stack] ITER ITERVAL
return false;
}
if (!bce_->emit1(JSOP_POP)) {
// [stack] ITER
return false;
}
if (!bce_->emit1(JSOP_MOREITER)) {
// [stack] ITER NEXTITERVAL?
return false;
}
if (!bce_->emit1(JSOP_ISNOITER)) {
// [stack] ITER NEXTITERVAL? ISNOITER
return false;
}
if (!loopInfo_->emitLoopEnd(bce_, JSOP_IFEQ)) {
// [stack] 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)) {
// [stack] ITER
return false;
}
if (!bce_->addTryNote(JSTRY_FOR_IN, bce_->stackDepth, loopInfo_->headOffset(),
bce_->offset())) {
return false;
}
if (!bce_->emit1(JSOP_ENDITER)) {
// [stack]
return false;
}
loopInfo_.reset();
#ifdef DEBUG
state_ = State::End;
#endif
return true;
}