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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/. */
+
+#ifndef vm_GeneratorObject_h
+#define vm_GeneratorObject_h
+
+#include "js/Class.h"
+#include "vm/ArgumentsObject.h"
+#include "vm/ArrayObject.h"
+#include "vm/BytecodeUtil.h"
+#include "vm/GeneratorResumeKind.h" // GeneratorResumeKind
+#include "vm/JSObject.h"
+#include "vm/Stack.h"
+
+namespace js {
+
+class InterpreterActivation;
+
+namespace frontend {
+class TaggedParserAtomIndex;
+}
+
+extern const JSClass GeneratorFunctionClass;
+
+class AbstractGeneratorObject : public NativeObject {
+ public:
+ // Magic value stored in the resumeIndex slot when the generator is
+ // running or closing. See the resumeIndex comment below.
+ static const int32_t RESUME_INDEX_RUNNING = INT32_MAX;
+
+ enum {
+ CALLEE_SLOT = 0,
+ ENV_CHAIN_SLOT,
+ ARGS_OBJ_SLOT,
+ STACK_STORAGE_SLOT,
+ RESUME_INDEX_SLOT,
+ RESERVED_SLOTS
+ };
+
+ // Maximum number of fixed stack slots in a generator or async function
+ // script. If a script would have more, we instead store some variables in
+ // heap EnvironmentObjects.
+ //
+ // This limit is a performance heuristic. Stack slots reduce allocations,
+ // and `Local` opcodes are a bit faster than `AliasedVar` ones; but at each
+ // `yield` or `await` the stack slots must be memcpy'd into a
+ // GeneratorObject. At some point the memcpy is too much. The limit is
+ // plenty for typical human-authored code.
+ static constexpr uint32_t FixedSlotLimit = 256;
+
+ private:
+ static JSObject* createModuleGenerator(JSContext* cx, AbstractFramePtr frame);
+
+ public:
+ static JSObject* createFromFrame(JSContext* cx, AbstractFramePtr frame);
+ static AbstractGeneratorObject* create(JSContext* cx, HandleFunction callee,
+ HandleScript script,
+ HandleObject environmentChain,
+ Handle<ArgumentsObject*> argsObject);
+
+ static bool resume(JSContext* cx, InterpreterActivation& activation,
+ Handle<AbstractGeneratorObject*> genObj, HandleValue arg,
+ HandleValue resumeKind);
+
+ static bool suspend(JSContext* cx, HandleObject obj, AbstractFramePtr frame,
+ const jsbytecode* pc, unsigned nvalues);
+
+ static void finalSuspend(HandleObject obj);
+
+ JSFunction& callee() const {
+ return getFixedSlot(CALLEE_SLOT).toObject().as<JSFunction>();
+ }
+ void setCallee(JSFunction& callee) {
+ setFixedSlot(CALLEE_SLOT, ObjectValue(callee));
+ }
+
+ JSObject& environmentChain() const {
+ return getFixedSlot(ENV_CHAIN_SLOT).toObject();
+ }
+ void setEnvironmentChain(JSObject& envChain) {
+ setFixedSlot(ENV_CHAIN_SLOT, ObjectValue(envChain));
+ }
+
+ bool hasArgsObj() const { return getFixedSlot(ARGS_OBJ_SLOT).isObject(); }
+ ArgumentsObject& argsObj() const {
+ return getFixedSlot(ARGS_OBJ_SLOT).toObject().as<ArgumentsObject>();
+ }
+ void setArgsObj(ArgumentsObject& argsObj) {
+ setFixedSlot(ARGS_OBJ_SLOT, ObjectValue(argsObj));
+ }
+
+ bool hasStackStorage() const {
+ return getFixedSlot(STACK_STORAGE_SLOT).isObject();
+ }
+ bool isStackStorageEmpty() const {
+ return stackStorage().getDenseInitializedLength() == 0;
+ }
+ ArrayObject& stackStorage() const {
+ return getFixedSlot(STACK_STORAGE_SLOT).toObject().as<ArrayObject>();
+ }
+ void setStackStorage(ArrayObject& stackStorage) {
+ setFixedSlot(STACK_STORAGE_SLOT, ObjectValue(stackStorage));
+ }
+
+ // Access stack storage. Requires `hasStackStorage() && isSuspended()`.
+ // `slot` is the index of the desired local in the stack frame when this
+ // generator is *not* suspended.
+ const Value& getUnaliasedLocal(uint32_t slot) const;
+ void setUnaliasedLocal(uint32_t slot, const Value& value);
+
+ // The resumeIndex slot is abused for a few purposes. It's undefined if
+ // it hasn't been set yet (before the initial yield), and null if the
+ // generator is closed. If the generator is running, the resumeIndex is
+ // RESUME_INDEX_RUNNING.
+ //
+ // If the generator is suspended, it's the resumeIndex (stored as
+ // JSOp::InitialYield/JSOp::Yield/JSOp::Await operand) of the yield
+ // instruction that suspended the generator. The resumeIndex can be mapped to
+ // the bytecode offset (interpreter) or to the native code offset (JIT).
+
+ bool isBeforeInitialYield() const {
+ return getFixedSlot(RESUME_INDEX_SLOT).isUndefined();
+ }
+ bool isRunning() const {
+ return getFixedSlot(RESUME_INDEX_SLOT) == Int32Value(RESUME_INDEX_RUNNING);
+ }
+ bool isSuspended() const {
+ // Note: also update Baseline's IsSuspendedGenerator code if this
+ // changes.
+ Value resumeIndex = getFixedSlot(RESUME_INDEX_SLOT);
+ return resumeIndex.isInt32() &&
+ resumeIndex.toInt32() < RESUME_INDEX_RUNNING;
+ }
+ void setRunning() {
+ MOZ_ASSERT(isSuspended());
+ setFixedSlot(RESUME_INDEX_SLOT, Int32Value(RESUME_INDEX_RUNNING));
+ }
+ void setResumeIndex(const jsbytecode* pc) {
+ MOZ_ASSERT(JSOp(*pc) == JSOp::InitialYield || JSOp(*pc) == JSOp::Yield ||
+ JSOp(*pc) == JSOp::Await);
+
+ MOZ_ASSERT_IF(JSOp(*pc) == JSOp::InitialYield,
+ getFixedSlot(RESUME_INDEX_SLOT).isUndefined());
+ MOZ_ASSERT_IF(JSOp(*pc) != JSOp::InitialYield, isRunning());
+
+ uint32_t resumeIndex = GET_UINT24(pc);
+ MOZ_ASSERT(resumeIndex < uint32_t(RESUME_INDEX_RUNNING));
+
+ setFixedSlot(RESUME_INDEX_SLOT, Int32Value(resumeIndex));
+ MOZ_ASSERT(isSuspended());
+ }
+ void setResumeIndex(int32_t resumeIndex) {
+ setFixedSlot(RESUME_INDEX_SLOT, Int32Value(resumeIndex));
+ }
+ uint32_t resumeIndex() const {
+ MOZ_ASSERT(isSuspended());
+ return getFixedSlot(RESUME_INDEX_SLOT).toInt32();
+ }
+ bool isClosed() const { return getFixedSlot(CALLEE_SLOT).isNull(); }
+ void setClosed() {
+ setFixedSlot(CALLEE_SLOT, NullValue());
+ setFixedSlot(ENV_CHAIN_SLOT, NullValue());
+ setFixedSlot(ARGS_OBJ_SLOT, NullValue());
+ setFixedSlot(STACK_STORAGE_SLOT, NullValue());
+ setFixedSlot(RESUME_INDEX_SLOT, NullValue());
+ }
+
+ bool isAfterYield();
+ bool isAfterAwait();
+
+ private:
+ bool isAfterYieldOrAwait(JSOp op);
+
+ public:
+ void trace(JSTracer* trc);
+
+ static size_t offsetOfCalleeSlot() { return getFixedSlotOffset(CALLEE_SLOT); }
+ static size_t offsetOfEnvironmentChainSlot() {
+ return getFixedSlotOffset(ENV_CHAIN_SLOT);
+ }
+ static size_t offsetOfArgsObjSlot() {
+ return getFixedSlotOffset(ARGS_OBJ_SLOT);
+ }
+ static size_t offsetOfResumeIndexSlot() {
+ return getFixedSlotOffset(RESUME_INDEX_SLOT);
+ }
+ static size_t offsetOfStackStorageSlot() {
+ return getFixedSlotOffset(STACK_STORAGE_SLOT);
+ }
+
+ static size_t calleeSlot() { return CALLEE_SLOT; }
+ static size_t envChainSlot() { return ENV_CHAIN_SLOT; }
+ static size_t argsObjectSlot() { return ARGS_OBJ_SLOT; }
+ static size_t stackStorageSlot() { return STACK_STORAGE_SLOT; }
+ static size_t resumeIndexSlot() { return RESUME_INDEX_SLOT; }
+
+#ifdef DEBUG
+ void dump() const;
+#endif
+};
+
+class GeneratorObject : public AbstractGeneratorObject {
+ public:
+ enum { RESERVED_SLOTS = AbstractGeneratorObject::RESERVED_SLOTS };
+
+ static const JSClass class_;
+ static const JSClassOps classOps_;
+
+ static GeneratorObject* create(JSContext* cx, HandleFunction fun);
+};
+
+bool GeneratorThrowOrReturn(JSContext* cx, AbstractFramePtr frame,
+ Handle<AbstractGeneratorObject*> obj,
+ HandleValue val, GeneratorResumeKind resumeKind);
+
+/**
+ * Return the generator object associated with the given frame. The frame must
+ * be a call frame for a generator.
+ *
+ * This may return nullptr at certain points in the generator lifecycle:
+ *
+ * - While a generator call evaluates default argument values and performs
+ * destructuring, which occurs before the generator object is created.
+ *
+ * - Between the `Generator` instruction and the `SetAliasedVar .generator`
+ * instruction, at which point the generator object does exist, but is held
+ * only on the stack, and not the `.generator` pseudo-variable this function
+ * consults.
+ */
+AbstractGeneratorObject* GetGeneratorObjectForFrame(JSContext* cx,
+ AbstractFramePtr frame);
+
+/**
+ * If `env` or any enclosing environment is a `CallObject` associated with a
+ * generator object, return the generator.
+ *
+ * Otherwise `env` is not in a generator or async function, or the generator
+ * object hasn't been created yet; return nullptr with no pending exception.
+ */
+AbstractGeneratorObject* GetGeneratorObjectForEnvironment(JSContext* cx,
+ HandleObject env);
+
+GeneratorResumeKind ParserAtomToResumeKind(
+ frontend::TaggedParserAtomIndex atom);
+JSAtom* ResumeKindToAtom(JSContext* cx, GeneratorResumeKind kind);
+
+} // namespace js
+
+template <>
+bool JSObject::is<js::AbstractGeneratorObject>() const;
+
+#endif /* vm_GeneratorObject_h */