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AK: Use OOB pointer for "empty" last-fast-access Vector last ptr

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This is a _significant_ perf improvement as we no longer have to think
about tracking state transitions from empty <-> nonempty.
(corresponds to a ~20% perf improvement in LibWasm)
This commit is contained in:
Ali Mohammad Pur 2025-09-21 11:59:08 +02:00 committed by Ali Mohammad Pur
parent 02b3c4f8a9
commit 15bb9fee71
1 changed files with 39 additions and 37 deletions
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76
AK/Vector.h
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@ -69,11 +69,15 @@ public:
using ValueType = T;
Vector()
{
if constexpr (inline_capacity > 0)
update_metadata();
}
Vector(std::initializer_list<T> list)
requires(!IsLvalueReference<T>)
{
if constexpr (inline_capacity > 0)
update_metadata();
ensure_capacity(list.size());
for (auto& item : list)
unchecked_append(item);
@ -88,8 +92,8 @@ public:
if (!m_metadata.outline_buffer) {
TypedTransfer<T>::move(inline_buffer(), other.inline_buffer(), m_size);
TypedTransfer<T>::delete_(other.inline_buffer(), m_size);
update_metadata();
}
update_metadata();
}
other.m_metadata = {};
other.m_size = 0;
@ -101,7 +105,8 @@ public:
ensure_capacity(other.size());
TypedTransfer<StorageType>::copy(data(), other.data(), other.size());
m_size = other.size();
update_metadata();
if (m_capacity > 0)
update_metadata();
}
explicit Vector(ReadonlySpan<T> other)
@ -110,7 +115,8 @@ public:
ensure_capacity(other.size());
TypedTransfer<StorageType>::copy(data(), other.data(), other.size());
m_size = other.size();
update_metadata();
if (m_capacity > 0)
update_metadata();
}
template<size_t other_inline_capacity, FastLastAccess other_requested_fast_last_access>
@ -119,7 +125,8 @@ public:
ensure_capacity(other.size());
TypedTransfer<StorageType>::copy(data(), other.data(), other.size());
m_size = other.size();
update_metadata();
if (m_capacity > 0)
update_metadata();
}
~Vector()
@ -339,13 +346,8 @@ public:
{
VERIFY(m_size < capacity());
if constexpr (want_fast_last_access) {
if (m_size == 0) {
m_metadata.last_slot = slot(0);
m_size = 1;
} else {
++m_metadata.last_slot;
++m_size;
}
++m_metadata.last_slot;
++m_size;
} else {
++m_size;
}
@ -370,7 +372,7 @@ public:
VERIFY((size() + count) <= capacity());
TypedTransfer<StorageType>::copy(slot(m_size), values, count);
m_size += count;
update_metadata();
update_metadata(); // We have *some* space, since we're appending.
}
template<class... Args>
@ -428,7 +430,8 @@ public:
ensure_capacity(other.size());
TypedTransfer<StorageType>::copy(data(), other.data(), other.size());
m_size = other.size();
update_metadata();
if (m_capacity > 0)
update_metadata();
}
return *this;
}
@ -440,7 +443,8 @@ public:
ensure_capacity(other.size());
TypedTransfer<StorageType>::copy(data(), other.data(), other.size());
m_size = other.size();
update_metadata();
if (m_capacity > 0)
update_metadata();
return *this;
}
@ -459,8 +463,8 @@ public:
for (size_t i = 0; i < m_size; ++i)
data()[i].~StorageType();
m_size = 0;
if constexpr (want_fast_last_access)
m_metadata.last_slot = nullptr;
if (m_capacity != 0)
update_metadata();
}
void remove(size_t index)
@ -478,7 +482,7 @@ public:
}
--m_size;
update_metadata();
update_metadata(); // We have *some* space, we just removed something that was there.
}
void remove(size_t index, size_t count)
@ -500,7 +504,7 @@ public:
}
m_size -= count;
update_metadata();
update_metadata(); // We have *some* space, we just removed something that was there.
}
/// The iterator pair identify a set of indices *in ascending order* to be removed.
@ -532,7 +536,7 @@ public:
VERIFY(!(it != end));
m_size = write_index;
update_metadata();
update_metadata(); // We have *some* space, we just removed something that was there.
}
template<IterableContainer Is, typename ToIndex = decltype (*declval<Is>().begin()) (*)(decltype(declval<Is>().begin()) const&)>
@ -576,7 +580,7 @@ public:
if constexpr (!contains_reference)
last().~T();
--m_size;
update_metadata();
update_metadata(); // We have *some* space, we just removed something that was there.
if constexpr (contains_reference)
return *value;
@ -605,7 +609,7 @@ public:
if constexpr (!contains_reference)
m_metadata.last_slot->~T();
--m_size;
update_metadata();
update_metadata(); // We have *some* space, we just removed something that was there.
if constexpr (contains_reference)
return *value;
@ -663,7 +667,7 @@ public:
new (slot(index)) StorageType(&value);
else
new (slot(index)) StorageType(forward<U>(value));
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -696,7 +700,7 @@ public:
TRY(try_grow_capacity(size() + other_size));
TypedTransfer<StorageType>::move(data() + m_size, tmp.data(), other_size);
m_size += other_size;
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -705,7 +709,7 @@ public:
TRY(try_grow_capacity(size() + other.size()));
TypedTransfer<StorageType>::copy(data() + m_size, other.data(), other.size());
m_size += other.m_size;
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -717,7 +721,7 @@ public:
else
new (slot(m_size)) StorageType(move(value));
++m_size;
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -734,7 +738,7 @@ public:
TRY(try_grow_capacity(size() + count));
TypedTransfer<StorageType>::copy(slot(m_size), values, count);
m_size += count;
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -745,7 +749,7 @@ public:
TRY(try_grow_capacity(m_size + 1));
new (slot(m_size)) StorageType { forward<Args>(args)... };
++m_size;
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -777,7 +781,7 @@ public:
Vector tmp = move(other);
TypedTransfer<StorageType>::move(slot(0), tmp.data(), tmp.size());
m_size += other_size;
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -789,7 +793,7 @@ public:
TypedTransfer<StorageType>::move(slot(count), slot(0), m_size);
TypedTransfer<StorageType>::copy(slot(0), values, count);
m_size += count;
update_metadata();
update_metadata(); // We have *some* space, try_grow_capacity above ensured nonzero.
return {};
}
@ -821,7 +825,7 @@ public:
kfree_sized(m_metadata.outline_buffer, m_capacity * sizeof(StorageType));
m_metadata.outline_buffer = new_buffer;
m_capacity = new_capacity;
update_metadata();
update_metadata(); // We have *some* space, we just allocated it.
return {};
}
@ -838,7 +842,7 @@ public:
for (size_t i = size(); i < new_size; ++i)
new (slot(i)) StorageType {};
m_size = new_size;
update_metadata();
update_metadata(); // We have *some* space, try_ensure_capacity above ensured nonzero.
return {};
}
@ -855,7 +859,7 @@ public:
for (size_t i = size(); i < new_size; ++i)
new (slot(i)) StorageType { default_value };
m_size = new_size;
update_metadata();
update_metadata(); // We have *some* space, try_ensure_capacity above ensured nonzero.
return {};
}
@ -892,7 +896,7 @@ public:
for (size_t i = new_size; i < size(); ++i)
at(i).~StorageType();
m_size = new_size;
update_metadata();
update_metadata(); // We have *some* space, as new_size can't be zero here.
}
void resize(size_t new_size, bool keep_capacity = false)
@ -1037,13 +1041,11 @@ private:
StorageType& raw_first() { return raw_at(0); }
StorageType& raw_at(size_t index) { return *slot(index); }
/// NOTE: Do *not* call unguarded if m_capacity can be zero.
ALWAYS_INLINE void update_metadata()
{
if constexpr (want_fast_last_access) {
if (m_size > 0)
m_metadata.last_slot = slot(m_size - 1);
else
m_metadata.last_slot = nullptr;
m_metadata.last_slot = slot(m_size) - 1;
}
}