qtbase: use qHashMulti & qHashRange instead of QHashCombine

If we have no specific need for the private QHashCombine class, use the
front-end functions. For headers, we do have a need: we prefer
QHashCombine because it compiles faster.

Change-Id: I73578ea802d3b905a53bfffd504c20af0ca96cf8
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/io/qurlquery.cpp

@@ -428,11 +428,8 @@ bool comparesEqual(const QUrlQuery &lhs, const QUrlQuery &rhs)
 size_t qHash(const QUrlQuery &key, size_t seed) noexcept
 {
     if (const QUrlQueryPrivate *d = key.d) {
-        QtPrivate::QHashCombine hash;
         // keep in sync with operator==:
-        seed = hash(seed, d->valueDelimiter);
-        seed = hash(seed, d->pairDelimiter);
-        seed = hash(seed, d->itemList);
+        return qHashMulti(seed, d->valueDelimiter, d->pairDelimiter, d->itemList);
     }
     return seed;
 }

src/corelib/itemmodels/qitemselectionmodel.cpp

@@ -1813,10 +1813,7 @@ struct RowOrColumnDefinition {
 };
 size_t qHash(const RowOrColumnDefinition &key, size_t seed = 0) noexcept
 {
-    QtPrivate::QHashCombine hash;
-    seed = hash(seed, key.parent);
-    seed = hash(seed, key.rowOrColumn);
-    return seed;
+    return qHashMulti(seed, key.parent, key.rowOrColumn);
 }
 
 QT_SPECIALIZE_STD_HASH_TO_CALL_QHASH_BY_CREF(RowOrColumnDefinition)

src/corelib/serialization/qcborvalue.cpp

@@ -3192,12 +3192,8 @@ size_t qHash(const QCborValue &value, size_t seed)
         return qHash(value.toArray(), seed);
     case QCborValue::Map:
         return qHash(value.toMap(), seed);
-    case QCborValue::Tag: {
-        QtPrivate::QHashCombine hash;
-        seed = hash(seed, value.tag());
-        seed = hash(seed, value.taggedValue());
-        return seed;
-    }
+    case QCborValue::Tag:
+        return qHashMulti(seed, value.tag(), value.taggedValue());
     case QCborValue::SimpleType:
         break;
     case QCborValue::False:

src/corelib/tools/qversionnumber.cpp

@@ -576,10 +576,7 @@ QDebug operator<<(QDebug debug, const QVersionNumber &version)
 */
 size_t qHash(const QVersionNumber &key, size_t seed)
 {
-    QtPrivate::QHashCombine hash;
-    for (int i = 0; i < key.segmentCount(); ++i)
-        seed = hash(seed, key.segmentAt(i));
-    return seed;
+    return qHashRange(key.begin(), key.end(), seed);
 }
 
 QT_END_NAMESPACE

tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp

@@ -23,7 +23,7 @@ public:
     // random values
     static constexpr quint64 ZeroSeed = 0;
     static constexpr quint64 RandomSeed32 = 1045982819;
-    static constexpr quint64 RandomSeed64 = QtPrivate::QHashCombine{}(RandomSeed32, RandomSeed32);
+    static constexpr quint64 RandomSeed64 = qHashMulti(0, RandomSeed32, RandomSeed32);
     size_t seed;
 
     template <typename T1, typename T2> void stdPair_template(const T1 &t1, const T2 &t2);

tests/benchmarks/corelib/tools/qhash/tst_bench_qhash.cpp

@@ -12,7 +12,7 @@
 #include <QTest>
 
 static constexpr quint64 RandomSeed32 = 1045982819;
-static constexpr quint64 RandomSeed64 = QtPrivate::QHashCombine{}(RandomSeed32, RandomSeed32);
+static constexpr quint64 RandomSeed64 = qHashMulti(0, RandomSeed32, RandomSeed32);
 
 class tst_QHash : public QObject
 {