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-rw-r--r--js/src/frontend/ForOfEmitter.cpp224
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diff --git a/js/src/frontend/ForOfEmitter.cpp b/js/src/frontend/ForOfEmitter.cpp
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+++ b/js/src/frontend/ForOfEmitter.cpp
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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/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
+ // some fix (bug 1482003).
+ 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;
+}