Source code
Revision control
Copy as Markdown
Other Tools
/* -*- 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/ForOfEmitter.h"
#include "frontend/BytecodeEmitter.h"
#include "frontend/EmitterScope.h"
#include "frontend/ParserAtom.h" // TaggedParserAtomIndex
#include "vm/Opcodes.h"
#include "vm/StencilEnums.h" // TryNoteKind
using namespace js;
using namespace js::frontend;
using mozilla::Nothing;
ForOfEmitter::ForOfEmitter(BytecodeEmitter* bce,
const EmitterScope* headLexicalEmitterScope,
SelfHostedIter selfHostedIter, IteratorKind iterKind)
: bce_(bce),
selfHostedIter_(selfHostedIter),
iterKind_(iterKind),
headLexicalEmitterScope_(headLexicalEmitterScope) {}
bool ForOfEmitter::emitIterated() {
MOZ_ASSERT(state_ == State::Start);
// Evaluate the expression being iterated. The forHeadExpr should use a
// distinct TDZCheckCache to evaluate since (abstractly) it runs in its
// own LexicalEnvironment.
tdzCacheForIteratedValue_.emplace(bce_);
#ifdef DEBUG
state_ = State::Iterated;
#endif
return true;
}
bool ForOfEmitter::emitInitialize(uint32_t forPos) {
MOZ_ASSERT(state_ == State::Iterated);
tdzCacheForIteratedValue_.reset();
// [stack] # if AllowContentWithNext
// [stack] NEXT ITER
// [stack] # elif AllowContentWith
// [stack] ITERABLE ITERFN SYNC_ITERFN?
// [stack] # else
// [stack] ITERABLE
if (iterKind_ == IteratorKind::Async) {
if (!bce_->emitAsyncIterator(selfHostedIter_)) {
// [stack] NEXT ITER
return false;
}
} else {
if (!bce_->emitIterator(selfHostedIter_)) {
// [stack] NEXT ITER
return false;
}
}
// For-of loops have the iterator next method and the iterator itself on the
// stack.
int32_t iterDepth = bce_->bytecodeSection().stackDepth();
loopInfo_.emplace(bce_, iterDepth, selfHostedIter_, iterKind_);
if (!loopInfo_->emitLoopHead(bce_, Nothing())) {
// [stack] NEXT ITER
return false;
}
// If the loop had an escaping lexical declaration, replace the current
// environment with an dead zoned one to implement TDZ semantics.
if (headLexicalEmitterScope_) {
// The environment chain only includes an environment for the for-of
// 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] NEXT ITER
return false;
}
}
// For uncaptured bindings, put them back in TDZ.
if (!headLexicalEmitterScope_->deadZoneFrameSlots(bce_)) {
return false;
}
}
#ifdef DEBUG
loopDepth_ = bce_->bytecodeSection().stackDepth();
#endif
// Make sure this code is attributed to the "for".
if (!bce_->updateSourceCoordNotes(forPos)) {
return false;
}
if (!bce_->emit1(JSOp::Dup2)) {
// [stack] NEXT ITER NEXT ITER
return false;
}
if (!bce_->emitIteratorNext(mozilla::Some(forPos), iterKind_,
selfHostedIter_)) {
// [stack] NEXT ITER RESULT
return false;
}
if (!bce_->emit1(JSOp::Dup)) {
// [stack] NEXT ITER RESULT RESULT
return false;
}
if (!bce_->emitAtomOp(JSOp::GetProp,
TaggedParserAtomIndex::WellKnown::done())) {
// [stack] NEXT ITER RESULT DONE
return false;
}
// if (done) break;
MOZ_ASSERT(bce_->innermostNestableControl == loopInfo_.ptr(),
"must be at the top-level of the loop");
if (!bce_->emitJump(JSOp::JumpIfTrue, &loopInfo_->breaks)) {
// [stack] NEXT ITER RESULT
return false;
}
// Emit code to assign result.value to the iteration variable.
//
// Note that ES 13.7.5.13, step 5.c says getting result.value does not
// call IteratorClose, so start TryNoteKind::ForOfIterClose after the GetProp.
if (!bce_->emitAtomOp(JSOp::GetProp,
TaggedParserAtomIndex::WellKnown::value())) {
// [stack] NEXT ITER VALUE
return false;
}
if (!loopInfo_->emitBeginCodeNeedingIteratorClose(bce_)) {
return false;
}
#ifdef DEBUG
state_ = State::Initialize;
#endif
return true;
}
bool ForOfEmitter::emitBody() {
MOZ_ASSERT(state_ == State::Initialize);
MOZ_ASSERT(bce_->bytecodeSection().stackDepth() == loopDepth_ + 1,
"the stack must be balanced around the initializing "
"operation");
#ifdef DEBUG
state_ = State::Body;
#endif
return true;
}
bool ForOfEmitter::emitEnd(uint32_t iteratedPos) {
MOZ_ASSERT(state_ == State::Body);
MOZ_ASSERT(bce_->bytecodeSection().stackDepth() == loopDepth_ + 1,
"the stack must be balanced around the for-of body");
if (!loopInfo_->emitEndCodeNeedingIteratorClose(bce_)) {
// [stack] NEXT ITER VALUE
return false;
}
if (!loopInfo_->emitContinueTarget(bce_)) {
// [stack] NEXT ITER VALUE
return false;
}
// We use the iterated value's position to attribute the backedge,
// which corresponds to the iteration protocol.
// This is a bit misleading for 2nd and later iterations and might need
if (!bce_->updateSourceCoordNotes(iteratedPos)) {
return false;
}
if (!bce_->emit1(JSOp::Pop)) {
// [stack] NEXT ITER
return false;
}
if (!loopInfo_->emitLoopEnd(bce_, JSOp::Goto, TryNoteKind::ForOf)) {
// [stack] NEXT ITER
return false;
}
// All jumps/breaks to this point still have an extra value on the stack.
MOZ_ASSERT(bce_->bytecodeSection().stackDepth() == loopDepth_);
bce_->bytecodeSection().setStackDepth(bce_->bytecodeSection().stackDepth() +
1);
if (!bce_->emitPopN(3)) {
// [stack]
return false;
}
loopInfo_.reset();
#ifdef DEBUG
state_ = State::End;
#endif
return true;
}