Don't move data in QArrayDataOps::reallocate()

reallocate() should only ever call realloc(), and only be used to
create more space at the end of the data.

Change-Id: I2ac4dbc90d2afaa571bb620108d7984356712cb2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>

3 files changed, 7 insertions, 19 deletions

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index 18ee2dbfb3..945a2a26fd 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -671,7 +671,7 @@ QByteArray qUncompress(const uchar* data, qsizetype nbytes)
                 return invalidCompressedData();
             } else {
                 // grow the block
-                d->reallocate(d->allocatedCapacity()*2, QByteArray::Data::GrowsForward);
+                d->reallocate(d->allocatedCapacity()*2);
                 if (Q_UNLIKELY(d.data() == nullptr))
                     return invalidCompressedData();
             }
@@ -1719,7 +1719,7 @@ void QByteArray::reallocData(qsizetype alloc, Data::ArrayOptions options)
         dd.data()[dd.size] = 0;
         d = dd;
     } else {
-        d->reallocate(alloc, options);
+        d->reallocate(alloc);
     }
 }
 
@@ -1734,7 +1734,7 @@ void QByteArray::reallocGrowData(qsizetype n)
         dd.data()[dd.size] = 0;
         d = dd;
     } else {
-        d->reallocate(d.constAllocatedCapacity() + n, Data::GrowsForward);
+        d->reallocate(d.constAllocatedCapacity() + n);
     }
 }
 
diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp
index 51af7fe32a..3e6188a38d 100644
--- a/src/corelib/text/qstring.cpp
+++ b/src/corelib/text/qstring.cpp
@@ -2516,7 +2516,7 @@ void QString::reallocData(qsizetype alloc, Data::ArrayOptions allocOptions)
         dd.data()[dd.size] = 0;
         d = dd;
     } else {
-        d->reallocate(alloc, allocOptions);
+        d->reallocate(alloc);
     }
 }
 
@@ -2531,7 +2531,7 @@ void QString::reallocGrowData(qsizetype n)
         dd.data()[dd.size] = 0;
         d = dd;
     } else {
-        d->reallocate(d.constAllocatedCapacity() + n, Data::GrowsForward);
+        d->reallocate(d.constAllocatedCapacity() + n);
     }
 }
 
diff --git a/src/corelib/tools/qarraydataops.h b/src/corelib/tools/qarraydataops.h
index 3aab72f8ae..140d79b2e3 100644
--- a/src/corelib/tools/qarraydataops.h
+++ b/src/corelib/tools/qarraydataops.h
@@ -457,21 +457,9 @@ public:
         }
     }
 
-    void reallocate(qsizetype alloc, typename Data::ArrayOptions options)
+    void reallocate(qsizetype alloc)
     {
-        // when reallocating, take care of the situation when no growth is
-        // happening - need to move the data in this case, unfortunately
-        const bool grows = options & (Data::GrowsForward | Data::GrowsBackwards);
-
-        // ### optimize me: there may be cases when moving is not obligatory
-        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),
-                      this->size * sizeof(T));
-        }
-
-        auto pair = Data::reallocateUnaligned(this->d, this->ptr, alloc, options);
+        auto pair = Data::reallocateUnaligned(this->d, this->ptr, alloc, QArrayData::GrowsBackwards);
         this->d = pair.first;
         this->ptr = pair.second;
     }