Use QHash instead of QMap for resolved types

This vastly speeds up resolved type reference lookups in
QQmlObjectCreator::createInstance, which translates to significant
improvements in qmlbench:
perf record -b ./src/qmlbench --shell frame-count delegates_qobject.qml
went from roughly 730 frames to > 800 locally.

To have a stable order in the hash, we simply sort a tempory vector of
keys. As this happens only once, the overhead is negligible and
partially offset by the better memory locality of the QHash anyway.

Task-number: QTBUG-88672
Change-Id: Ib547a87fd0d2d81f366ea927ade232f33b3d3788
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 13 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4executablecompilationunit.cpp b/src/qml/jsruntime/qv4executablecompilationunit.cpp
index f61bf36b0e..ade5204f9e 100644
--- a/src/qml/jsruntime/qv4executablecompilationunit.cpp
+++ b/src/qml/jsruntime/qv4executablecompilationunit.cpp
@@ -865,10 +865,22 @@ bool ExecutableCompilationUnit::saveToDisk(const QUrl &unitUrl, QString *errorSt
     });
 }
 
+/*!
+    \internal
+    This function creates a temporary key vector and sorts it to guarantuee a stable
+    hash. This is used to calculate a check-sum on dependent meta-objects.
+ */
 bool ResolvedTypeReferenceMap::addToHash(QCryptographicHash *hash, QQmlEngine *engine) const
 {
+    std::vector<int> keys (count());
+    int i = 0;
     for (auto it = constBegin(), end = constEnd(); it != end; ++it) {
-        if (!it.value()->addToHash(hash, engine))
+        keys[i] = it.key();
+        ++i;
+    }
+    std::sort(keys.begin(), keys.end());
+    for (int key: keys) {
+        if (!this->operator[](key)->addToHash(hash, engine))
             return false;
     }