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// Copyright 2018 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_MAYBE_OBJECT_INL_H_
#define V8_OBJECTS_MAYBE_OBJECT_INL_H_
#include "src/objects/maybe-object.h"
#ifdef V8_COMPRESS_POINTERS
#include "src/execution/isolate.h"
#endif
#include "src/objects/smi-inl.h"
#include "src/objects/tagged-impl-inl.h"
namespace v8 {
namespace internal {
//
// MaybeObject implementation.
//
// static
MaybeObject MaybeObject::FromSmi(Smi smi) {
DCHECK(HAS_SMI_TAG(smi.ptr()));
return MaybeObject(smi.ptr());
}
// static
MaybeObject MaybeObject::FromObject(Object object) {
DCHECK(!HAS_WEAK_HEAP_OBJECT_TAG(object.ptr()));
return MaybeObject(object.ptr());
}
MaybeObject MaybeObject::MakeWeak(MaybeObject object) {
DCHECK(object.IsStrongOrWeak());
return MaybeObject(object.ptr() | kWeakHeapObjectMask);
}
//
// HeapObjectReference implementation.
//
HeapObjectReference::HeapObjectReference(Object object)
: MaybeObject(object.ptr()) {}
// static
HeapObjectReference HeapObjectReference::Strong(Object object) {
DCHECK(!object.IsSmi());
DCHECK(!HasWeakHeapObjectTag(object));
return HeapObjectReference(object);
}
// static
HeapObjectReference HeapObjectReference::Weak(Object object) {
DCHECK(!object.IsSmi());
DCHECK(!HasWeakHeapObjectTag(object));
return HeapObjectReference(object.ptr() | kWeakHeapObjectMask);
}
// static
HeapObjectReference HeapObjectReference::ClearedValue(Isolate* isolate) {
// Construct cleared weak ref value.
Address raw_value = kClearedWeakHeapObjectLower32;
#ifdef V8_COMPRESS_POINTERS
// This is necessary to make pointer decompression computation also
// suitable for cleared weak references.
Address isolate_root = isolate->isolate_root();
raw_value |= isolate_root;
DCHECK_EQ(raw_value & (~static_cast<Address>(kClearedWeakHeapObjectLower32)),
isolate_root);
#endif
// The rest of the code will check only the lower 32-bits.
DCHECK_EQ(kClearedWeakHeapObjectLower32, static_cast<uint32_t>(raw_value));
return HeapObjectReference(raw_value);
}
template <typename THeapObjectSlot>
void HeapObjectReference::Update(THeapObjectSlot slot, HeapObject value) {
static_assert(std::is_same<THeapObjectSlot, FullHeapObjectSlot>::value ||
std::is_same<THeapObjectSlot, HeapObjectSlot>::value,
"Only FullHeapObjectSlot and HeapObjectSlot are expected here");
Address old_value = (*slot).ptr();
DCHECK(!HAS_SMI_TAG(old_value));
Address new_value = value.ptr();
DCHECK(Internals::HasHeapObjectTag(new_value));
#ifdef DEBUG
bool weak_before = HAS_WEAK_HEAP_OBJECT_TAG(old_value);
#endif
slot.store(
HeapObjectReference(new_value | (old_value & kWeakHeapObjectMask)));
#ifdef DEBUG
bool weak_after = HAS_WEAK_HEAP_OBJECT_TAG((*slot).ptr());
DCHECK_EQ(weak_before, weak_after);
#endif
}
} // namespace internal
} // namespace v8
#endif // V8_OBJECTS_MAYBE_OBJECT_INL_H_
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