Optimize QPromise destructor

Unify cancel and finish in QPromise destructor in a single call. This
saves us one extra mutex lock and atomic state change.

Task-number: QTBUG-84977
Change-Id: Iac06302c39a2863008b27325fcf6792d4f58c8ae
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 26 insertions, 4 deletions

diff --git a/src/corelib/thread/qfutureinterface.cpp b/src/corelib/thread/qfutureinterface.cpp
index b34385897c..e640114bb0 100644
--- a/src/corelib/thread/qfutureinterface.cpp
+++ b/src/corelib/thread/qfutureinterface.cpp
@@ -110,14 +110,36 @@ static inline int switch_from_to(QAtomicInt &a, int from, int to)
 
 void QFutureInterfaceBase::cancel()
 {
+    cancel(CancelMode::CancelOnly);
+}
+
+void QFutureInterfaceBase::cancel(QFutureInterfaceBase::CancelMode mode)
+{
     QMutexLocker locker(&d->m_mutex);
-    if (d->state.loadRelaxed() & Canceled)
-        return;
 
-    switch_from_to(d->state, suspendingOrSuspended, Canceled);
+    const auto oldState = d->state.loadRelaxed();
+
+    switch (mode) {
+    case CancelMode::CancelAndFinish:
+        if ((oldState & Finished) && (oldState & Canceled))
+            return;
+        switch_from_to(d->state, suspendingOrSuspended | Running, Canceled | Finished);
+        break;
+    case CancelMode::CancelOnly:
+        if (oldState & Canceled)
+            return;
+        switch_from_to(d->state, suspendingOrSuspended, Canceled);
+        break;
+    }
+
     d->waitCondition.wakeAll();
     d->pausedWaitCondition.wakeAll();
-    d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Canceled));
+
+    if (!(oldState & Canceled))
+        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Canceled));
+    if (mode == CancelMode::CancelAndFinish && !(oldState & Finished))
+        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Finished));
+
     d->isValid = false;
 }