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/*
* Copyright (C) 2023 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "Structure.h"
namespace JSC {
DECLARE_ALLOCATOR_WITH_HEAP_IDENTIFIER(MegamorphicCache);
class MegamorphicCache {
WTF_MAKE_FAST_ALLOCATED;
WTF_MAKE_NONCOPYABLE(MegamorphicCache);
public:
static constexpr uint32_t primarySize = 2048;
static constexpr uint32_t secondarySize = 512;
static_assert(hasOneBitSet(primarySize), "size should be a power of two.");
static_assert(hasOneBitSet(secondarySize), "size should be a power of two.");
static constexpr uint32_t primaryMask = primarySize - 1;
static constexpr uint32_t secondaryMask = secondarySize - 1;
static constexpr uint32_t storeCachePrimarySize = 2048;
static constexpr uint32_t storeCacheSecondarySize = 512;
static_assert(hasOneBitSet(storeCachePrimarySize), "size should be a power of two.");
static_assert(hasOneBitSet(storeCacheSecondarySize), "size should be a power of two.");
static constexpr uint32_t storeCachePrimaryMask = storeCachePrimarySize - 1;
static constexpr uint32_t storeCacheSecondaryMask = storeCacheSecondarySize - 1;
static constexpr uint16_t invalidEpoch = 0;
static constexpr PropertyOffset maxOffset = UINT16_MAX;
struct Entry {
static ptrdiff_t offsetOfUid() { return OBJECT_OFFSETOF(Entry, m_uid); }
static ptrdiff_t offsetOfStructureID() { return OBJECT_OFFSETOF(Entry, m_structureID); }
static ptrdiff_t offsetOfEpoch() { return OBJECT_OFFSETOF(Entry, m_epoch); }
static ptrdiff_t offsetOfOffset() { return OBJECT_OFFSETOF(Entry, m_offset); }
static ptrdiff_t offsetOfHolder() { return OBJECT_OFFSETOF(Entry, m_holder); }
void initAsMiss(StructureID structureID, UniquedStringImpl* uid, uint16_t epoch)
{
m_uid = uid;
m_structureID = structureID;
m_epoch = epoch;
m_offset = 0;
m_holder = nullptr;
}
void initAsHit(StructureID structureID, UniquedStringImpl* uid, uint16_t epoch, JSCell* holder, uint16_t offset, bool ownProperty)
{
m_uid = uid;
m_structureID = structureID;
m_epoch = epoch;
m_offset = offset;
m_holder = (ownProperty) ? JSCell::seenMultipleCalleeObjects() : holder;
}
RefPtr<UniquedStringImpl> m_uid;
StructureID m_structureID { };
uint16_t m_epoch { invalidEpoch };
uint16_t m_offset { 0 };
JSCell* m_holder { nullptr };
};
struct StoreEntry {
static ptrdiff_t offsetOfUid() { return OBJECT_OFFSETOF(StoreEntry, m_uid); }
static ptrdiff_t offsetOfOldStructureID() { return OBJECT_OFFSETOF(StoreEntry, m_oldStructureID); }
static ptrdiff_t offsetOfNewStructureID() { return OBJECT_OFFSETOF(StoreEntry, m_newStructureID); }
static ptrdiff_t offsetOfEpoch() { return OBJECT_OFFSETOF(StoreEntry, m_epoch); }
static ptrdiff_t offsetOfOffset() { return OBJECT_OFFSETOF(StoreEntry, m_offset); }
void init(StructureID oldStructureID, StructureID newStructureID, UniquedStringImpl* uid, uint16_t epoch, uint16_t offset)
{
m_uid = uid;
m_oldStructureID = oldStructureID;
m_newStructureID = newStructureID;
m_epoch = epoch;
m_offset = offset;
}
RefPtr<UniquedStringImpl> m_uid;
StructureID m_oldStructureID { };
StructureID m_newStructureID { };
uint16_t m_epoch { invalidEpoch };
uint16_t m_offset { 0 };
};
static ptrdiff_t offsetOfPrimaryEntries() { return OBJECT_OFFSETOF(MegamorphicCache, m_primaryEntries); }
static ptrdiff_t offsetOfSecondaryEntries() { return OBJECT_OFFSETOF(MegamorphicCache, m_secondaryEntries); }
static ptrdiff_t offsetOfStoreCachePrimaryEntries() { return OBJECT_OFFSETOF(MegamorphicCache, m_storeCachePrimaryEntries); }
static ptrdiff_t offsetOfStoreCacheSecondaryEntries() { return OBJECT_OFFSETOF(MegamorphicCache, m_storeCacheSecondaryEntries); }
static ptrdiff_t offsetOfEpoch() { return OBJECT_OFFSETOF(MegamorphicCache, m_epoch); }
MegamorphicCache() = default;
#if CPU(ADDRESS64) && !ENABLE(STRUCTURE_ID_WITH_SHIFT)
// Because Structure is allocated with 16-byte alignment, we should assume that StructureID's lower 4 bits are zeros.
static constexpr unsigned structureIDHashShift1 = 4;
#else
// When using STRUCTURE_ID_WITH_SHIFT, all bits can be different. Thus we do not need to shift the first level.
static constexpr unsigned structureIDHashShift1 = 0;
#endif
static constexpr unsigned structureIDHashShift2 = structureIDHashShift1 + 11;
static constexpr unsigned structureIDHashShift3 = structureIDHashShift1 + 9;
static constexpr unsigned structureIDHashShift4 = structureIDHashShift1 + 11;
static constexpr unsigned structureIDHashShift5 = structureIDHashShift1 + 9;
ALWAYS_INLINE static uint32_t primaryHash(StructureID structureID, UniquedStringImpl* uid)
{
uint32_t sid = bitwise_cast<uint32_t>(structureID);
return ((sid >> structureIDHashShift1) ^ (sid >> structureIDHashShift2)) + uid->hash();
}
ALWAYS_INLINE static uint32_t secondaryHash(StructureID structureID, UniquedStringImpl* uid)
{
uint32_t key = bitwise_cast<uint32_t>(structureID) + static_cast<uint32_t>(bitwise_cast<uintptr_t>(uid));
return key + (key >> structureIDHashShift3);
}
ALWAYS_INLINE static uint32_t storeCachePrimaryHash(StructureID structureID, UniquedStringImpl* uid)
{
uint32_t sid = bitwise_cast<uint32_t>(structureID);
return ((sid >> structureIDHashShift1) ^ (sid >> structureIDHashShift4)) + uid->hash();
}
ALWAYS_INLINE static uint32_t storeCacheSecondaryHash(StructureID structureID, UniquedStringImpl* uid)
{
uint32_t key = bitwise_cast<uint32_t>(structureID) + static_cast<uint32_t>(bitwise_cast<uintptr_t>(uid));
return key + (key >> structureIDHashShift5);
}
JS_EXPORT_PRIVATE void age(CollectionScope);
void initAsMiss(StructureID structureID, UniquedStringImpl* uid)
{
uint32_t primaryIndex = MegamorphicCache::primaryHash(structureID, uid) & primaryMask;
auto& entry = m_primaryEntries[primaryIndex];
if (entry.m_epoch == m_epoch) {
uint32_t secondaryIndex = MegamorphicCache::secondaryHash(entry.m_structureID, entry.m_uid.get()) & secondaryMask;
m_secondaryEntries[secondaryIndex] = WTFMove(entry);
}
m_primaryEntries[primaryIndex].initAsMiss(structureID, uid, m_epoch);
}
void initAsHit(StructureID structureID, UniquedStringImpl* uid, JSCell* holder, uint16_t offset, bool ownProperty)
{
uint32_t primaryIndex = MegamorphicCache::primaryHash(structureID, uid) & primaryMask;
auto& entry = m_primaryEntries[primaryIndex];
if (entry.m_epoch == m_epoch) {
uint32_t secondaryIndex = MegamorphicCache::secondaryHash(entry.m_structureID, entry.m_uid.get()) & secondaryMask;
m_secondaryEntries[secondaryIndex] = WTFMove(entry);
}
m_primaryEntries[primaryIndex].initAsHit(structureID, uid, m_epoch, holder, offset, ownProperty);
}
void initAsTransition(StructureID oldStructureID, StructureID newStructureID, UniquedStringImpl* uid, uint16_t offset)
{
uint32_t primaryIndex = MegamorphicCache::storeCachePrimaryHash(oldStructureID, uid) & storeCachePrimaryMask;
auto& entry = m_storeCachePrimaryEntries[primaryIndex];
if (entry.m_epoch == m_epoch) {
uint32_t secondaryIndex = MegamorphicCache::storeCacheSecondaryHash(entry.m_oldStructureID, entry.m_uid.get()) & storeCacheSecondaryMask;
m_storeCacheSecondaryEntries[secondaryIndex] = WTFMove(entry);
}
m_storeCachePrimaryEntries[primaryIndex].init(oldStructureID, newStructureID, uid, m_epoch, offset);
}
void initAsReplace(StructureID structureID, UniquedStringImpl* uid, uint16_t offset)
{
uint32_t primaryIndex = MegamorphicCache::storeCachePrimaryHash(structureID, uid) & storeCachePrimaryMask;
auto& entry = m_storeCachePrimaryEntries[primaryIndex];
if (entry.m_epoch == m_epoch) {
uint32_t secondaryIndex = MegamorphicCache::storeCacheSecondaryHash(entry.m_oldStructureID, entry.m_uid.get()) & storeCacheSecondaryMask;
m_storeCacheSecondaryEntries[secondaryIndex] = WTFMove(entry);
}
m_storeCachePrimaryEntries[primaryIndex].init(structureID, structureID, uid, m_epoch, offset);
}
uint16_t epoch() const { return m_epoch; }
void bumpEpoch()
{
++m_epoch;
if (UNLIKELY(m_epoch == invalidEpoch))
clearEntries();
}
private:
JS_EXPORT_PRIVATE void clearEntries();
std::array<Entry, primarySize> m_primaryEntries { };
std::array<Entry, secondarySize> m_secondaryEntries { };
std::array<StoreEntry, storeCachePrimarySize> m_storeCachePrimaryEntries { };
std::array<StoreEntry, storeCacheSecondarySize> m_storeCacheSecondaryEntries { };
uint16_t m_epoch { 1 };
};
} // namespace JSC
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