Utils: Cache FilePath::qHash

Calling toCaseFolded is expensive if the same filepath is hashed
often, so we calculate the hash value once and cache the result.

One such case was found to happen when parsing tests,
as the cpp parser is queried a lot and it uses hash maps / sets
with filepaths.

Change-Id: Ic3ca7f09e8f108f5a89b3fdb17743ae7c3258001
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/filepath.cpp

@@ -441,6 +441,7 @@ void FilePath::setParts(const QStringView scheme, const QStringView host, QStrin
     if (path.length() >= 3 && path[0] == '/' && path[1] == '.' && path[2] == '/')
         path = path.mid(3);
 
+    m_hash = 0;
     m_data = path.toString() + scheme.toString() + host.toString();
     m_schemeLen = scheme.size();
     m_hostLen = host.size();
@@ -2078,10 +2079,16 @@ QTCREATOR_UTILS_EXPORT bool operator>=(const FilePath &first, const FilePath &se
 
 QTCREATOR_UTILS_EXPORT size_t qHash(const FilePath &filePath, uint seed)
 {
-    if (filePath.caseSensitivity() == Qt::CaseSensitive)
-        return qHash(QStringView(filePath.m_data), seed);
-    const size_t schemeHostHash = qHash(QStringView(filePath.m_data).mid(filePath.m_pathLen), seed);
-    return qHash(filePath.path().toCaseFolded(), seed) ^ schemeHostHash;
+    Q_UNUSED(seed);
+
+    if (filePath.m_hash == 0) {
+        if (filePath.caseSensitivity() == Qt::CaseSensitive)
+            filePath.m_hash = qHash(QStringView(filePath.m_data), 0);
+        else
+            filePath.m_hash = qHash(filePath.m_data.toCaseFolded(), 0);
+    }
+
+    return filePath.m_hash;
 }
 
 QTCREATOR_UTILS_EXPORT size_t qHash(const FilePath &filePath)

src/libs/utils/filepath.h

@@ -277,6 +277,7 @@ private:
     unsigned int m_pathLen = 0;
     unsigned short m_schemeLen = 0;
     unsigned short m_hostLen = 0;
+    mutable size_t m_hash = 0;
 };
 
 class QTCREATOR_UTILS_EXPORT DeviceFileHooks