CMake: Speed up extra compiler processing a bit

Makes extra compiler selection 30% faster on my test project.

Change-Id: If78084ce4a5a93140598dd19e8448295ca122863
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cmakeprojectmanager/cmakeproject.cpp

@@ -531,24 +531,35 @@ void CMakeProject::createGeneratedCodeModelSupport()
 {
     qDeleteAll(m_extraCompilers);
     m_extraCompilers.clear();
-    QList<ExtraCompilerFactory *> factories =
+    const QList<ExtraCompilerFactory *> factories =
             ExtraCompilerFactory::extraCompilerFactories();
 
+    const QSet<QString> fileExtensions
+            = Utils::transform<QSet>(factories, [](const ExtraCompilerFactory *f) { return f->sourceTag(); });
+
     // Find all files generated by any of the extra compilers, in a rather crude way.
-    foreach (const QString &file, files(SourceFiles)) {
-        foreach (ExtraCompilerFactory *factory, factories) {
-            if (file.endsWith('.' + factory->sourceTag())) {
-                QStringList generated = filesGeneratedFrom(file);
-                if (!generated.isEmpty()) {
-                    const FileNameList fileNames = transform(generated,
-                                                             [](const QString &s) {
-                        return FileName::fromString(s);
-                    });
-                    m_extraCompilers.append(factory->create(this, FileName::fromString(file),
-                                                            fileNames));
-                }
-            }
-        }
+    const QStringList fileList = files(SourceFiles, [&fileExtensions](const FileNode *fn) {
+        const QString fp = fn->filePath().toString();
+        const int pos = fp.lastIndexOf('.');
+        return pos >= 0 && fileExtensions.contains(fp.mid(pos + 1));
+    });
+
+    // Generate the necessary information:
+    for (const QString &file : fileList) {
+        ExtraCompilerFactory *factory = Utils::findOrDefault(factories, [&file](const ExtraCompilerFactory *f) {
+            return file.endsWith('.' + f->sourceTag());
+        });
+        QTC_ASSERT(factory, continue);
+
+        QStringList generated = filesGeneratedFrom(file);
+        if (generated.isEmpty())
+            continue;
+
+        const FileNameList fileNames
+                = transform(generated,
+                            [](const QString &s) { return FileName::fromString(s); });
+        m_extraCompilers.append(factory->create(this, FileName::fromString(file),
+                                                fileNames));
     }
 
     CppTools::GeneratedCodeModelSupport::update(m_extraCompilers);