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// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_OBJECTS_ARGUMENTS_H_
#define V8_OBJECTS_ARGUMENTS_H_
#include "src/objects/fixed-array.h"
#include "src/objects/js-objects.h"
#include "src/objects/struct.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
class StructBodyDescriptor;
#include "torque-generated/src/objects/arguments-tq.inc"
// Superclass for all objects with instance type {JS_ARGUMENTS_OBJECT_TYPE}
class JSArgumentsObject
: public TorqueGeneratedJSArgumentsObject<JSArgumentsObject, JSObject> {
public:
DECL_VERIFIER(JSArgumentsObject)
DECL_PRINTER(JSArgumentsObject)
TQ_OBJECT_CONSTRUCTORS(JSArgumentsObject)
};
// JSSloppyArgumentsObject is just a JSArgumentsObject with specific initial
// map. This initial map adds in-object properties for "length" and "callee".
class JSSloppyArgumentsObject
: public TorqueGeneratedJSSloppyArgumentsObject<JSSloppyArgumentsObject,
JSArgumentsObject> {
public:
// Indices of in-object properties.
static const int kLengthIndex = 0;
static const int kCalleeIndex = kLengthIndex + 1;
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(JSSloppyArgumentsObject);
};
// JSStrictArgumentsObject is just a JSArgumentsObject with specific initial
// map. This initial map adds an in-object property for "length".
class JSStrictArgumentsObject
: public TorqueGeneratedJSStrictArgumentsObject<JSStrictArgumentsObject,
JSArgumentsObject> {
public:
// Indices of in-object properties.
static const int kLengthIndex = 0;
static_assert(kLengthIndex == JSSloppyArgumentsObject::kLengthIndex);
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(JSStrictArgumentsObject);
};
// Representation of a slow alias as part of a sloppy arguments objects.
// For fast aliases (if HasSloppyArgumentsElements()):
// - the parameter map contains an index into the context
// - all attributes of the element have default values
// For slow aliases (if HasDictionaryArgumentsElements()):
// - the parameter map contains no fast alias mapping (i.e. the hole)
// - this struct (in the slow backing store) contains an index into the context
// - all attributes are available as part if the property details
class AliasedArgumentsEntry
: public TorqueGeneratedAliasedArgumentsEntry<AliasedArgumentsEntry,
Struct> {
public:
using BodyDescriptor = StructBodyDescriptor;
TQ_OBJECT_CONSTRUCTORS(AliasedArgumentsEntry)
};
// Helper class to access FAST_ and SLOW_SLOPPY_ARGUMENTS_ELEMENTS, dividing
// arguments into two types for a given SloppyArgumentsElements object:
// mapped and unmapped.
//
// For clarity SloppyArgumentsElements fields are qualified with "elements."
// below.
//
// Mapped arguments are actual arguments. Unmapped arguments are values added
// to the arguments object after it was created for the call. Mapped arguments
// are stored in the context at indexes given by elements.mapped_entries[key].
// Unmapped arguments are stored as regular indexed properties in the arguments
// array which can be accessed from elements.arguments.
//
// elements.length is min(number_of_actual_arguments,
// number_of_formal_arguments) for a concrete call to a function.
//
// Once a SloppyArgumentsElements is generated, lookup of an argument with index
// |key| in |elements| works as follows:
//
// If key >= elements.length then attempt to look in the unmapped arguments
// array and return the value at key, missing to the runtime if the unmapped
// arguments array is not a fixed array or if key >= elements.arguments.length.
//
// Otherwise, t = elements.mapped_entries[key]. If t is the hole, then the
// entry has been deleted from the arguments object, and value is looked up in
// the unmapped arguments array, as described above. Otherwise, t is a Smi
// index into the context array specified at elements.context, and the return
// value is elements.context[t].
//
// A graphic representation of a SloppyArgumentsElements object and a
// corresponding unmapped arguments FixedArray:
//
// SloppyArgumentsElements
// +---+-----------------------+
// | Context context |
// +---------------------------+
// | FixedArray arguments +----+ HOLEY_ELEMENTS
// +---------------------------+ v-----+-----------+
// | 0 | Object mapped_entries | | 0 | the_hole |
// |...| ... | | ... | ... |
// |n-1| Object mapped_entries | | n-1 | the_hole |
// +---------------------------+ | n | element_1 |
// | ... | ... |
// |n+m-1| element_m |
// +-----------------+
//
// The elements.arguments backing store kind depends on the ElementsKind of
// the outer JSArgumentsObject:
// - FAST_SLOPPY_ARGUMENTS_ELEMENTS: HOLEY_ELEMENTS
// - SLOW_SLOPPY_ARGUMENTS_ELEMENTS: DICTIONARY_ELEMENTS
class SloppyArgumentsElements : public FixedArrayBase {
OBJECT_CONSTRUCTORS(SloppyArgumentsElements, FixedArrayBase);
public:
inline Tagged<Context> context() const;
inline void set_context(Tagged<Context> value,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
// Returns: FixedArray|NumberDictionary.
inline Tagged<FixedArray> arguments() const;
inline void set_arguments(Tagged<FixedArray> value,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
// Returns: Smi|TheHole.
inline Tagged<Object> mapped_entries(int index, RelaxedLoadTag) const;
inline void set_mapped_entries(int index, Tagged<Object> value);
inline void set_mapped_entries(int index, Tagged<Object> value,
RelaxedStoreTag);
inline int AllocatedSize() const;
static constexpr int SizeFor(int length) { return OffsetOfElementAt(length); }
static constexpr int OffsetOfElementAt(int index) {
return kHeaderSize + index * kTaggedSize;
}
DECL_CAST(SloppyArgumentsElements)
DECL_PRINTER(SloppyArgumentsElements)
DECL_VERIFIER(SloppyArgumentsElements)
#define FIELD_LIST(V) \
V(kContextOffset, kTaggedSize) \
V(kArgumentsOffset, kTaggedSize) \
V(kUnalignedHeaderSize, OBJECT_POINTER_PADDING(kUnalignedHeaderSize)) \
V(kHeaderSize, 0) \
V(kMappedEntriesOffset, 0) // mapped_entries[length]
DEFINE_FIELD_OFFSET_CONSTANTS(FixedArrayBase::kHeaderSize, FIELD_LIST)
#undef FIELD_LIST
class BodyDescriptor;
};
} // namespace internal
} // namespace v8
#include "src/objects/object-macros-undef.h"
#endif // V8_OBJECTS_ARGUMENTS_H_
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