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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_PTR_COMPR_INL_H_
#define V8_PTR_COMPR_INL_H_
#include "include/v8-internal.h"
#include "src/ptr-compr.h"
namespace v8 {
namespace internal {
#if V8_TARGET_ARCH_64_BIT
// Compresses full-pointer representation of a tagged value to on-heap
// representation.
V8_INLINE Tagged_t CompressTagged(Address tagged) {
return static_cast<Tagged_t>(static_cast<uint32_t>(tagged));
}
enum class OnHeapAddressKind {
kAnyOnHeapAddress,
kIsolateRoot,
};
// Calculates isolate root value from any on-heap address.
template <OnHeapAddressKind kAddressKind = OnHeapAddressKind::kAnyOnHeapAddress>
V8_INLINE Address GetRootFromOnHeapAddress(Address on_heap_addr) {
if (kAddressKind == OnHeapAddressKind::kIsolateRoot) return on_heap_addr;
return RoundDown(on_heap_addr + kPtrComprIsolateRootBias,
kPtrComprIsolateRootAlignment);
}
// Decompresses weak or strong heap object pointer or forwarding pointer,
// preserving both weak- and smi- tags.
template <OnHeapAddressKind kAddressKind = OnHeapAddressKind::kAnyOnHeapAddress>
V8_INLINE Address DecompressTaggedPointer(Address on_heap_addr,
Tagged_t raw_value) {
// Current compression scheme requires |raw_value| to be sign-extended
// from int32_t to intptr_t.
intptr_t value = static_cast<intptr_t>(static_cast<int32_t>(raw_value));
Address root = GetRootFromOnHeapAddress<kAddressKind>(on_heap_addr);
return root + static_cast<Address>(value);
}
// Decompresses any tagged value, preserving both weak- and smi- tags.
template <OnHeapAddressKind kAddressKind = OnHeapAddressKind::kAnyOnHeapAddress>
V8_INLINE Address DecompressTaggedAny(Address on_heap_addr,
Tagged_t raw_value) {
// Current compression scheme requires |raw_value| to be sign-extended
// from int32_t to intptr_t.
intptr_t value = static_cast<intptr_t>(static_cast<int32_t>(raw_value));
if (kUseBranchlessPtrDecompression) {
// |root_mask| is 0 if the |value| was a smi or -1 otherwise.
Address root_mask = static_cast<Address>(-(value & kSmiTagMask));
Address root_or_zero =
root_mask & GetRootFromOnHeapAddress<kAddressKind>(on_heap_addr);
return root_or_zero + static_cast<Address>(value);
} else {
return HAS_SMI_TAG(value)
? static_cast<Address>(value)
: (GetRootFromOnHeapAddress<kAddressKind>(on_heap_addr) +
static_cast<Address>(value));
}
}
#ifdef V8_COMPRESS_POINTERS
STATIC_ASSERT(kPtrComprHeapReservationSize ==
Internals::kPtrComprHeapReservationSize);
STATIC_ASSERT(kPtrComprIsolateRootBias == Internals::kPtrComprIsolateRootBias);
STATIC_ASSERT(kPtrComprIsolateRootAlignment ==
Internals::kPtrComprIsolateRootAlignment);
#endif // V8_COMPRESS_POINTERS
#else
V8_INLINE Tagged_t CompressTagged(Address tagged) { UNREACHABLE(); }
#endif // V8_TARGET_ARCH_64_BIT
} // namespace internal
} // namespace v8
#endif // V8_PTR_COMPR_INL_H_
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