Track tree references that have to be expanded

... as this is relevant for performance of analysis. We log the total
numer of trees at performance level and the individual directories
at debug level, if requested.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/buildtool/build_engine/target_map/target_map.cpp b/src/buildtool/build_engine/target_map/target_map.cpp
index 66e1ec73..8005a032 100644
--- a/src/buildtool/build_engine/target_map/target_map.cpp
+++ b/src/buildtool/build_engine/target_map/target_map.cpp
@@ -16,6 +16,8 @@
 #include "src/buildtool/build_engine/expression/function_map.hpp"
 #include "src/buildtool/build_engine/target_map/built_in_rules.hpp"
 #include "src/buildtool/build_engine/target_map/utils.hpp"
+#include "src/buildtool/common/statistics.hpp"
+#include "src/buildtool/logging/logger.hpp"
 #include "src/utils/cpp/path.hpp"
 #include "src/utils/cpp/vector.hpp"
 
@@ -1342,6 +1344,12 @@ void TreeTarget(
                 (*setter)(std::move(analysis_result));
                 return;
             }
+            Logger::Log(LogLevel::Debug, [&key]() {
+                return fmt::format(
+                    "Source tree reference for non-known tree {}",
+                    key.target.ToString());
+            });
+            Statistics::Instance().IncrementTreesAnalysedCounter();
 
             using BuildMaps::Target::ConfiguredTarget;