AuroraMiddleware/qt5base-lts
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Simplify reallocation handling in QList

Browse Source 
Have one generic method for detaching and reallocations.
Use that method throughout QList to avoid duplicated
instantiations of code paths that are rarely used.

Change-Id: I5b9add3be5f17b387e2d34028b72c8f52db68444
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Lars Knoll 2020-11-04 22:59:09 +01:00
parent 20883c9bcc
commit 6be39809b0
5 changed files with 103 additions and 163 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
src/corelib/tools/qarraydataops.h
View File

@ -1311,60 +1311,37 @@ public:
public:
void insert(qsizetype i, qsizetype n, parameter_type t)
{
if (this->needsDetach() || (n > this->freeSpaceAtBegin() && n > this->freeSpaceAtEnd())) {
T copy(t);
typename Data::GrowthPosition pos = Data::GrowsAtEnd;
if (this->size != 0 && i <= (this->size >> 1))
pos = Data::GrowsAtBeginning;
this->detachAndGrow(pos, n);
Q_ASSERT((pos == Data::GrowsAtBeginning && this->freeSpaceAtBegin() >= n) ||
(pos == Data::GrowsAtEnd && this->freeSpaceAtEnd() >= n));
DataPointer detached(DataPointer::allocateGrow(*this, n, pos));
const_iterator where = this->constBegin() + i;
detached->copyAppend(this->constBegin(), where);
detached->copyAppend(n, t);
detached->copyAppend(where, this->constEnd());
this->swap(detached);
} else {
T copy(t);
// Insert elements based on the divided distance. Good case: only 1
// insert happens (either to the front part or to the back part). Bad
// case: both inserts happen, meaning that we touch all N elements in
// the container (this should be handled "outside" by ensuring enough
// free space by reallocating more frequently)
T *where = this->begin() + i;
const auto beginSize = sizeToInsertAtBegin(where, n);
if (beginSize)
Base::insert(GrowsBackwardsTag{}, where, beginSize, copy);
if (n - beginSize)
Base::insert(GrowsForwardTag{}, where, n - beginSize, copy);
}
if (pos == QArrayData::GrowsAtBeginning)
Base::insert(GrowsBackwardsTag{}, where, n, copy);
else
Base::insert(GrowsForwardTag{}, where, n, copy);
}
void insert(qsizetype i, const T *data, qsizetype n)
{
if (this->needsDetach() || (n > this->freeSpaceAtBegin() && n > this->freeSpaceAtEnd())) {
typename Data::GrowthPosition pos = Data::GrowsAtEnd;
if (this->size != 0 && i <= (this->size >> 1))
pos = Data::GrowsAtBeginning;
DataPointer oldData;
this->detachAndGrow(pos, n, &oldData);
Q_ASSERT((pos == Data::GrowsAtBeginning && this->freeSpaceAtBegin() >= n) ||
(pos == Data::GrowsAtEnd && this->freeSpaceAtEnd() >= n));
DataPointer detached(DataPointer::allocateGrow(*this, n, pos));
auto where = this->constBegin() + i;
detached->copyAppend(this->constBegin(), where);
detached->copyAppend(data, data + n);
detached->copyAppend(where, this->constEnd());
this->swap(detached);
} else {
// Insert elements based on the divided distance. Good case: only 1
// insert happens (either to the front part or to the back part). Bad
// case: both inserts happen, meaning that we touch all N elements in
// the container (this should be handled "outside" by ensuring enough
// free space by reallocating more frequently)
T *where = this->begin() + i;
const auto k = sizeToInsertAtBegin(where, n);
if (k)
Base::insert(GrowsBackwardsTag{}, where, data, data + k);
if (k != n)
Base::insert(GrowsForwardTag{}, where, data + k, data + n);
}
if (pos == QArrayData::GrowsAtBeginning)
Base::insert(GrowsBackwardsTag{}, where, data, data + n);
else
Base::insert(GrowsForwardTag{}, where, data, data + n);
}
template<typename... Args>

88
src/corelib/tools/qarraydatapointer.h
View File

@ -162,17 +162,55 @@ public:
swap(tmp);
}
QArrayDataPointer detach()
void detach(QArrayDataPointer *old = nullptr)
{
if (needsDetach()) {
QPair<Data *, T *> copy = clone();
QArrayDataPointer old(d, ptr, size);
d = copy.first;
ptr = copy.second;
return old;
if (needsDetach())
reallocateAndGrow(QArrayData::GrowsAtEnd, 0, old);
}
return QArrayDataPointer();
// pass in a pointer to a default constructed QADP, to keep it alive beyond the detach() call
void detachAndGrow(QArrayData::GrowthPosition where, qsizetype n, QArrayDataPointer *old = nullptr)
{
if (!needsDetach()) {
if (!n ||
(where == QArrayData::GrowsAtBeginning && freeSpaceAtBegin() >= n) ||
(where == QArrayData::GrowsAtEnd && freeSpaceAtEnd() >= n))
return;
}
reallocateAndGrow(where, n, old);
}
Q_NEVER_INLINE void reallocateAndGrow(QArrayData::GrowthPosition where, qsizetype n, QArrayDataPointer *old = nullptr)
{
if constexpr (QTypeInfo<T>::isRelocatable && alignof(T) <= alignof(std::max_align_t)) {
if (where == QArrayData::GrowsAtEnd && !old && !needsDetach() && n > 0) {
(*this)->reallocate(constAllocatedCapacity() - freeSpaceAtEnd() + n, QArrayData::Grow); // fast path
return;
}
}
QArrayDataPointer dp(allocateGrow(*this, n, where));
if (where == QArrayData::GrowsAtBeginning) {
dp.ptr += n;
Q_ASSERT(dp.freeSpaceAtBegin() >= n);
} else {
Q_ASSERT(dp.freeSpaceAtEnd() >= n);
}
if (size) {
qsizetype toCopy = size;
if (n < 0)
toCopy += n;
if (needsDetach() || old)
dp->copyAppend(begin(), begin() + toCopy);
else
dp->moveAppend(begin(), begin() + toCopy);
dp.d->flags = flags();
Q_ASSERT(dp.size == toCopy);
}
swap(dp);
if (old)
old->swap(dp);
}
// forwards from QArrayData
@ -244,40 +282,6 @@ public:
return lhs.data() != rhs.data() || lhs.size != rhs.size;
}
static void reallocateGrow(QArrayDataPointer &from, qsizetype n)
{
Q_ASSERT(n > 0);
if constexpr (!QTypeInfo<T>::isRelocatable || alignof(T) > alignof(std::max_align_t)) {
QArrayDataPointer dd(allocateGrow(from, n, QArrayData::GrowsAtEnd));
dd->copyAppend(from.data(), from.data() + from.size);
from.swap(dd);
} else {
if (from.needsDetach()) {
QArrayDataPointer dd(allocateGrow(from, n, QArrayData::GrowsAtEnd));
dd->copyAppend(from.data(), from.data() + from.size);
from.swap(dd);
} else {
from->reallocate(from.constAllocatedCapacity() - from.freeSpaceAtEnd() + n, QArrayData::Grow); // fast path
}
}
}
private:
[[nodiscard]] QPair<Data *, T *> clone() const
{
QPair<Data *, T *> pair = Data::allocate(detachCapacity(size), QArrayData::KeepSize);
QArrayDataPointer copy(pair.first, pair.second, 0);
if (size)
copy->copyAppend(begin(), end());
if (pair.first)
pair.first->flags = flags();
copy.d = nullptr;
copy.ptr = nullptr;
return pair;
}
protected:
Data *d;
T *ptr;

87
src/corelib/tools/qlist.h
View File

@ -385,7 +385,8 @@ public:
void replace(qsizetype i, parameter_type t)
{
Q_ASSERT_X(i >= 0 && i < d->size, "QList<T>::replace", "index out of range");
auto oldData = d.detach();
DataPointer oldData;
d.detach(&oldData);
d.data()[i] = t;
}
void replace(qsizetype i, rvalue_ref t)
@ -395,7 +396,8 @@ public:
Q_UNUSED(t);
} else {
Q_ASSERT_X(i >= 0 && i < d->size, "QList<T>::replace", "index out of range");
auto oldData = d.detach();
DataPointer oldData;
d.detach(&oldData);
d.data()[i] = std::move(t);
}
}
@ -603,15 +605,8 @@ inline void QList<T>::resize_internal(qsizetype newSize)
Q_ASSERT(newSize >= 0);
if (d->needsDetach() || newSize > capacity() - d.freeSpaceAtBegin()) {
// must allocate memory
DataPointer detached(Data::allocate(d->detachCapacity(newSize)));
qsizetype toCopy = qMin(size(), newSize);
if (toCopy)
detached->copyAppend(constBegin(), constBegin() + toCopy);
d.swap(detached);
}
if (newSize < size())
d.reallocateAndGrow(QArrayData::GrowsAtEnd, newSize - d.size);
} else if (newSize < size())
d->truncate(newSize);
}
@ -645,7 +640,10 @@ inline void QList<T>::squeeze()
// must allocate memory
DataPointer detached(Data::allocate(size()));
if (size()) {
if (d.needsDetach())
detached->copyAppend(constBegin(), constEnd());
else
detached->moveAppend(d.data(), d.data() + d.size);
}
d.swap(detached);
}
@ -662,9 +660,7 @@ inline void QList<T>::remove(qsizetype i, qsizetype n)
if (n == 0)
return;
if (d->needsDetach())
d.detach();
d->erase(d->begin() + i, d->begin() + i + n);
}
@ -672,7 +668,6 @@ template <typename T>
inline void QList<T>::removeFirst()
{
Q_ASSERT(!isEmpty());
if (d->needsDetach())
d.detach();
d->eraseFirst();
}
@ -681,8 +676,7 @@ template <typename T>
inline void QList<T>::removeLast()
{
Q_ASSERT(!isEmpty());
if (d->needsDetach())
detach();
d.detach();
d->eraseLast();
}
@ -699,39 +693,22 @@ inline void QList<T>::append(const_iterator i1, const_iterator i2)
if (i1 == i2)
return;
const auto distance = std::distance(i1, i2);
if (d->needsDetach() || distance > d.freeSpaceAtEnd()) {
DataPointer detached(DataPointer::allocateGrow(d, distance, QArrayData::GrowsAtEnd));
detached->copyAppend(constBegin(), constEnd());
detached->copyAppend(i1, i2);
d.swap(detached);
} else {
// we're detached and we can just move data around
DataPointer oldData;
d.detachAndGrow(QArrayData::GrowsAtEnd, distance, &oldData);
d->copyAppend(i1, i2);
}
}
template <typename T>
inline void QList<T>::append(QList<T> &&other)
{
Q_ASSERT(&other != this);
if (other.isEmpty())
return;
if (other.d->needsDetach() || !std::is_nothrow_move_constructible_v<T>)
return append(other);
if (d->needsDetach() || other.size() > d.freeSpaceAtEnd()) {
DataPointer detached(DataPointer::allocateGrow(d, other.size(), QArrayData::GrowsAtEnd));
if (!d->needsDetach())
detached->moveAppend(begin(), end());
else
detached->copyAppend(cbegin(), cend());
detached->moveAppend(other.begin(), other.end());
d.swap(detached);
} else {
// we're detached and we can just move data around
d.detachAndGrow(QArrayData::GrowsAtEnd, other.size());
d->moveAppend(other.begin(), other.end());
}
}
template<typename T>
@ -739,14 +716,10 @@ template<typename... Args>
inline typename QList<T>::reference QList<T>::emplaceFront(Args &&... args)
{
if (d->needsDetach() || !d.freeSpaceAtBegin()) {
DataPointer detached(DataPointer::allocateGrow(d, 1, QArrayData::GrowsAtBeginning));
detached->emplaceBack(std::forward<Args>(args)...);
if (!d.needsDetach())
detached->moveAppend(d.begin(), d.end());
else
detached->copyAppend(constBegin(), constEnd());
d.swap(detached);
// protect against args being an element of the container
T tmp(std::forward<Args>(args)...);
d.reallocateAndGrow(QArrayData::GrowsAtBeginning, 1);
d->emplaceFront(std::move(tmp));
} else {
d->emplaceFront(std::forward<Args>(args)...);
}
@ -778,10 +751,8 @@ QList<T>::emplace(qsizetype i, Args&&... args)
DataPointer detached(DataPointer::allocateGrow(d, 1, pos));
const_iterator where = constBegin() + i;
// Create an element here to handle cases when a user moves the element
// from a container to the same container. This is a critical step for
// COW types (e.g. Qt types) since copyAppend() done before emplace()
// would shallow-copy the passed element and ruin the move
// protect against args being an element of the container
T tmp(std::forward<Args>(args)...);
detached->copyAppend(constBegin(), where);
@ -799,22 +770,10 @@ template<typename... Args>
inline typename QList<T>::reference QList<T>::emplaceBack(Args &&... args)
{
if (d->needsDetach() || !d.freeSpaceAtEnd()) {
// condition below should follow the condition in QArrayDataPointer::reallocateGrow()
if constexpr (!QTypeInfo<T>::isRelocatable || alignof(T) > alignof(std::max_align_t)) {
// avoid taking a temporary copy of Args
DataPointer detached(DataPointer::allocateGrow(d, 1, QArrayData::GrowsAtEnd));
detached->copyAppend(constBegin(), constEnd());
detached->emplace(detached.end(), std::forward<Args>(args)...);
d.swap(detached);
} else {
// Create an element here to handle cases when a user moves the element
// from a container to the same container. This is required as we call
// reallocate, which could delete the data args points to.
// This should be optimised to only take the copy when really required.
// protect against args being an element of the container
T tmp(std::forward<Args>(args)...);
DataPointer::reallocateGrow(d, 1);
d->emplace(d.end(), std::move(tmp));
}
d.reallocateAndGrow(QArrayData::GrowsAtEnd, 1);
d->emplaceBack(std::move(tmp));
} else {
d->emplaceBack(std::forward<Args>(args)...);
}

2
tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp
View File

@ -2079,7 +2079,7 @@ void tst_QArrayData::dataPointerAllocate()
const auto freeAtBegin = newDataPointer.freeSpaceAtBegin();
const auto freeAtEnd = newDataPointer.freeSpaceAtEnd();
QVERIFY(newAlloc > oldDataPointer.constAllocatedCapacity());
QVERIFY(newAlloc >= oldDataPointer.constAllocatedCapacity());
QCOMPARE(freeAtBegin + freeAtEnd, newAlloc);
if (GrowthPosition == QArrayData::GrowsAtBeginning) {
QVERIFY(freeAtBegin > 0);

4
tests/auto/corelib/tools/qlist/tst_qlist.cpp
View File

@ -874,8 +874,8 @@ void tst_QList::appendList() const
v6 << (QList<ConstructionCounted>() << 1 << 2);
v6 << (QList<ConstructionCounted>() << 3 << 4);
QCOMPARE(v6, expectedFour);
QCOMPARE(v6.at(0).copies, 2);
QCOMPARE(v6.at(0).moves, 1);
QCOMPARE(v6.at(0).copies, 1);
QCOMPARE(v6.at(0).moves, 3);
// +=
QList<ConstructionCounted> v7;