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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_COMMON_PTR_COMPR_INL_H_ #define V8_COMMON_PTR_COMPR_INL_H_ #include "include/v8-internal.h" #include "src/common/ptr-compr.h" #include "src/execution/isolate.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)); } // Calculates isolate root value from any on-heap address. template <typename TOnHeapAddress> V8_INLINE Address GetIsolateRoot(TOnHeapAddress on_heap_addr); template <> V8_INLINE Address GetIsolateRoot<Address>(Address on_heap_addr) { // We subtract 1 here in order to let the compiler generate addition of 32-bit // signed constant instead of 64-bit constant (the problem is that 2Gb looks // like a negative 32-bit value). It's correct because we will never use // leftmost address of V8 heap as |on_heap_addr|. return RoundDown<kPtrComprIsolateRootAlignment>(on_heap_addr + kPtrComprIsolateRootBias - 1); } template <> V8_INLINE Address GetIsolateRoot<Isolate*>(Isolate* isolate) { Address isolate_root = isolate->isolate_root(); #ifdef V8_COMPRESS_POINTERS isolate_root = reinterpret_cast<Address>(V8_ASSUME_ALIGNED( reinterpret_cast<void*>(isolate_root), kPtrComprIsolateRootAlignment)); #endif return isolate_root; } // Decompresses smi value. V8_INLINE Address DecompressTaggedSigned(Tagged_t raw_value) { // For runtime code the upper 32-bits of the Smi value do not matter. return static_cast<Address>(raw_value); } // Decompresses weak or strong heap object pointer or forwarding pointer, // preserving both weak- and smi- tags. template <typename TOnHeapAddress> V8_INLINE Address DecompressTaggedPointer(TOnHeapAddress 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 = GetIsolateRoot(on_heap_addr); return root + static_cast<Address>(value); } // Decompresses any tagged value, preserving both weak- and smi- tags. template <typename TOnHeapAddress> V8_INLINE Address DecompressTaggedAny(TOnHeapAddress on_heap_addr, Tagged_t raw_value) { if (kUseBranchlessPtrDecompressionInRuntime) { // 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)); // |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 & GetIsolateRoot(on_heap_addr); return root_or_zero + static_cast<Address>(value); } else { return HAS_SMI_TAG(raw_value) ? DecompressTaggedSigned(raw_value) : DecompressTaggedPointer(on_heap_addr, raw_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(); } V8_INLINE Address DecompressTaggedSigned(Tagged_t raw_value) { UNREACHABLE(); } template <typename TOnHeapAddress> V8_INLINE Address DecompressTaggedPointer(TOnHeapAddress on_heap_addr, Tagged_t raw_value) { UNREACHABLE(); } template <typename TOnHeapAddress> V8_INLINE Address DecompressTaggedAny(TOnHeapAddress on_heap_addr, Tagged_t raw_value) { UNREACHABLE(); } #endif // V8_TARGET_ARCH_64_BIT } // namespace internal } // namespace v8 #endif // V8_COMMON_PTR_COMPR_INL_H_