Move existing items when inserting instead of copying them

Use move operations to move existing items instead of copying
them. This speeds up insertions for non relocatable types
significantly (e.g. for std::string).

Change-Id: I308f381ac2242e50505f02675c2d2afbf21069d1
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 28 insertions, 33 deletions

diff --git a/src/corelib/tools/qarraydataops.h b/src/corelib/tools/qarraydataops.h
index fc9c5dbe7f..0e067bbbe5 100644
--- a/src/corelib/tools/qarraydataops.h
+++ b/src/corelib/tools/qarraydataops.h
@@ -566,8 +566,8 @@ public:
 
         // Array may be truncated at where in case of exceptions
 
-        T *const end = this->end();
-        const T *readIter = end;
+        T *end = this->end();
+        T *readIter = end;
         T *writeIter = end + (e - b);
 
         const T *const step1End = where + qMax(e - b, end - where);
@@ -578,7 +578,7 @@ public:
         while (writeIter != step1End) {
             --readIter;
             // If exception happens on construction, we should not call ~T()
-            new (writeIter - 1) T(*readIter);
+            new (writeIter - 1) T(std::move(*readIter));
             --writeIter;
         }
 
@@ -596,7 +596,7 @@ public:
         while (readIter != where) {
             --readIter;
             --writeIter;
-            *writeIter = *readIter;
+            *writeIter = std::move(*readIter);
         }
 
         while (writeIter != where) {
@@ -617,8 +617,8 @@ public:
 
         typedef typename QArrayExceptionSafetyPrimitives<T>::template Destructor<T *> Destructor;
 
-        T *const begin = this->begin();
-        const T *readIter = begin;
+        T *begin = this->begin();
+        T *readIter = begin;
         T *writeIter = begin - (e - b);
 
         const T *const step1End = where - qMax(e - b, where - begin);
@@ -627,7 +627,7 @@ public:
 
         // Construct new elements in array
         while (writeIter != step1End) {
-            new (writeIter) T(*readIter);
+            new (writeIter) T(std::move(*readIter));
             ++readIter;
             ++writeIter;
         }
@@ -644,7 +644,7 @@ public:
 
         // Copy assign over existing elements
         while (readIter != where) {
-            *writeIter = *readIter;
+            *writeIter = std::move(*readIter);
             ++readIter;
             ++writeIter;
         }
@@ -669,8 +669,8 @@ public:
         typedef typename QArrayExceptionSafetyPrimitives<T>::template Destructor<T *> Destructor;
 
         // Array may be truncated at where in case of exceptions
-        T *const end = this->end();
-        const T *readIter = end;
+        T *end = this->end();
+        T *readIter = end;
         T *writeIter = end + n;
 
         const T *const step1End = where + qMax<size_t>(n, end - where);
@@ -681,7 +681,7 @@ public:
         while (writeIter != step1End) {
             --readIter;
             // If exception happens on construction, we should not call ~T()
-            new (writeIter - 1) T(*readIter);
+            new (writeIter - 1) T(std::move(*readIter));
             --writeIter;
         }
 
@@ -699,7 +699,7 @@ public:
         while (readIter != where) {
             --readIter;
             --writeIter;
-            *writeIter = *readIter;
+            *writeIter = std::move(*readIter);
         }
 
         while (writeIter != where) {
@@ -718,8 +718,8 @@ public:
 
         typedef typename QArrayExceptionSafetyPrimitives<T>::template Destructor<T *> Destructor;
 
-        T *const begin = this->begin();
-        const T *readIter = begin;
+        T *begin = this->begin();
+        T *readIter = begin;
         T *writeIter = begin - n;
 
         const T *const step1End = where - qMax<size_t>(n, where - begin);
@@ -728,7 +728,7 @@ public:
 
         // Construct new elements in array
         while (writeIter != step1End) {
-            new (writeIter) T(*readIter);
+            new (writeIter) T(std::move(*readIter));
             ++readIter;
             ++writeIter;
         }
@@ -744,7 +744,7 @@ public:
 
         // Copy assign over existing elements
         while (readIter != where) {
-            *writeIter = *readIter;
+            *writeIter = std::move(*readIter);
             ++readIter;
             ++writeIter;
         }
@@ -1225,23 +1225,18 @@ public:
             detached->copyAppend(where, this->constEnd());
             this->swap(detached);
         } else {
-            // we're detached and we can just move data around
-            if (i == this->size && n <= this->freeSpaceAtEnd()) {
-                copyAppend(n, t);
-            } 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);
-            }
+            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);
         }
     }