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-rw-r--r--js/src/frontend/ForInEmitter.cpp154
1 files changed, 154 insertions, 0 deletions
diff --git a/js/src/frontend/ForInEmitter.cpp b/js/src/frontend/ForInEmitter.cpp
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index 0000000000..4d9f9ad540
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+++ b/js/src/frontend/ForInEmitter.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/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;
+}