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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
#include "frontend/ForInEmitter.h"
#include "frontend/BytecodeEmitter.h"
#include "frontend/EmitterScope.h"
#include "vm/Opcodes.h"
#include "vm/StencilEnums.h" // TryNoteKind
using namespace js;
using namespace js::frontend;
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;
}
loopInfo_.emplace(bce_, StatementKind::ForInLoop);
if (!loopInfo_->emitLoopHead(bce_, Nothing())) {
// [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 (!bce_->emitJump(JSOp::JumpIfTrue, &loopInfo_->breaks)) {
// [stack] ITER NEXTITERVAL?
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_->emitInternedScopeOp(headLexicalEmitterScope_->index(),
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_->bytecodeSection().stackDepth();
#endif
MOZ_ASSERT(loopDepth_ >= 2);
#ifdef DEBUG
state_ = State::Initialize;
#endif
return true;
}
bool ForInEmitter::emitBody() {
MOZ_ASSERT(state_ == State::Initialize);
MOZ_ASSERT(bce_->bytecodeSection().stackDepth() == loopDepth_,
"iterator and iterval must be left on the stack");
#ifdef DEBUG
state_ = State::Body;
#endif
return true;
}
bool ForInEmitter::emitEnd(uint32_t forPos) {
MOZ_ASSERT(state_ == State::Body);
// Make sure this code is attributed to the "for".
if (!bce_->updateSourceCoordNotes(forPos)) {
return false;
}
if (!loopInfo_->emitContinueTarget(bce_)) {
// [stack] ITER ITERVAL
return false;
}
if (!bce_->emit1(JSOp::Pop)) {
// [stack] ITER
return false;
}
if (!loopInfo_->emitLoopEnd(bce_, JSOp::Goto, TryNoteKind::ForIn)) {
// [stack] ITER
return false;
}
// When we leave the loop body and jump to this point, the iteration value is
// still on the stack. Account for that by updating the stack depth manually.
int32_t stackDepth = bce_->bytecodeSection().stackDepth() + 1;
MOZ_ASSERT(stackDepth == loopDepth_);
bce_->bytecodeSection().setStackDepth(stackDepth);
// [stack] ITER ITERVAL
// Pop the value and iterator and close the iterator.
if (!bce_->emit1(JSOp::EndIter)) {
// [stack]
return false;
}
loopInfo_.reset();
#ifdef DEBUG
state_ = State::End;
#endif
return true;
}