Update allocation interface of QArrayDataPointer

Added overload to allocGrow that figures the capacity to allocate from
the newSize argument passed. This is useful in QList (and likely in other
places)

Fixed QArrayPodOps::reallocate as a drive by: don't call memmove when
it is not needed

Task-number: QTBUG-84320
Change-Id: I67efe55a60efaf3ab6057b0249d6a446e04a09e3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 11 insertions, 8 deletions

diff --git a/src/corelib/tools/qarraydataops.h b/src/corelib/tools/qarraydataops.h
index edfcd82706..03ba93198c 100644
--- a/src/corelib/tools/qarraydataops.h
+++ b/src/corelib/tools/qarraydataops.h
@@ -460,8 +460,7 @@ public:
         const bool grows = options & (Data::GrowsForward | Data::GrowsBackwards);
 
         // ### optimize me: there may be cases when moving is not obligatory
-        if (this->d && !grows) {
-            const auto gap = this->freeSpaceAtBegin();
+        if (const auto gap = this->freeSpaceAtBegin(); this->d && !grows && gap) {
             auto oldBegin = this->begin();
             this->ptr -= gap;
             ::memmove(static_cast<void *>(this->begin()), static_cast<void *>(oldBegin),
diff --git a/src/corelib/tools/qarraydatapointer.h b/src/corelib/tools/qarraydatapointer.h
index aebc83ba3f..ad5acdb7fd 100644
--- a/src/corelib/tools/qarraydatapointer.h
+++ b/src/corelib/tools/qarraydatapointer.h
@@ -209,6 +209,12 @@ public:
         return d->constAllocatedCapacity() - freeSpaceAtBegin() - this->size;
     }
 
+    static QArrayDataPointer allocateGrow(const QArrayDataPointer &from,
+                                          qsizetype newSize, QArrayData::ArrayOptions options)
+    {
+        return allocateGrow(from, from.detachCapacity(newSize), newSize, options);
+    }
+
     static QArrayDataPointer allocateGrow(const QArrayDataPointer &from, qsizetype capacity,
                                           qsizetype newSize, QArrayData::ArrayOptions options)
     {
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 4298434a94..bd593bae55 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -564,7 +564,7 @@ inline void QList<T>::append(const_iterator i1, const_iterator i2)
     const size_t newSize = size() + distance;
     const bool shouldGrow = d->shouldGrowBeforeInsert(d.end(), qsizetype(distance));
     if (d->needsDetach() || newSize > d->allocatedCapacity() || shouldGrow) {
-        DataPointer detached(DataPointer::allocateGrow(d, d->detachCapacity(newSize), newSize,
+        DataPointer detached(DataPointer::allocateGrow(d, newSize,
                                                        d->detachFlags() | Data::GrowsForward));
         detached->copyAppend(constBegin(), constEnd());
         detached->copyAppend(i1, i2);
@@ -586,7 +586,7 @@ inline void QList<T>::append(QList<T> &&other)
     const size_t newSize = size() + other.size();
     const bool shouldGrow = d->shouldGrowBeforeInsert(d.end(), other.size());
     if (d->needsDetach() || newSize > d->allocatedCapacity() || shouldGrow) {
-        DataPointer detached(DataPointer::allocateGrow(d, d->detachCapacity(newSize), newSize,
+        DataPointer detached(DataPointer::allocateGrow(d, newSize,
                                                        d->detachFlags() | Data::GrowsForward));
 
         if (!d->needsDetach())
@@ -619,8 +619,7 @@ QList<T>::insert(qsizetype i, qsizetype n, parameter_type t)
         if (size_t(i) <= newSize / 4)
             flags |= Data::GrowsBackwards;
 
-        DataPointer detached(DataPointer::allocateGrow(d, d->detachCapacity(newSize), newSize,
-                                                       flags));
+        DataPointer detached(DataPointer::allocateGrow(d, newSize, flags));
         const_iterator where = constBegin() + i;
         detached->copyAppend(constBegin(), where);
         detached->copyAppend(n, t);
@@ -652,8 +651,7 @@ QList<T>::emplace(qsizetype i, Args&&... args)
         if (size_t(i) <= newSize / 4)
             flags |= Data::GrowsBackwards;
 
-        DataPointer detached(DataPointer::allocateGrow(d, d->detachCapacity(newSize), newSize,
-                                                       flags));
+        DataPointer detached(DataPointer::allocateGrow(d, newSize, flags));
         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