4 files changed, 22 insertions, 0 deletions

diff --git a/src/buildtool/build_engine/target_map/TARGETS b/src/buildtool/build_engine/target_map/TARGETS
index e57a8c3b..2b201fbf 100644
--- a/src/buildtool/build_engine/target_map/TARGETS
+++ b/src/buildtool/build_engine/target_map/TARGETS
@@ -46,6 +46,7 @@
     , ["src/buildtool/build_engine/base_maps", "targets_file_map"]
     , ["src/buildtool/build_engine/expression", "expression"]
     , ["src/buildtool/execution_api/local", "local"]
+    , ["src/buildtool/logging", "logging"]
     , ["src/buildtool/multithreading", "async_map_consumer"]
     , ["src/utils/cpp", "hash_combine"]
     , ["src/utils/cpp", "path"]
diff --git a/src/buildtool/build_engine/target_map/result_map.hpp b/src/buildtool/build_engine/target_map/result_map.hpp
index ca55ee74..846a381e 100644
--- a/src/buildtool/build_engine/target_map/result_map.hpp
+++ b/src/buildtool/build_engine/target_map/result_map.hpp
@@ -16,6 +16,7 @@
 #include "src/buildtool/build_engine/expression/expression.hpp"
 #include "src/buildtool/build_engine/target_map/configured_target.hpp"
 #include "src/buildtool/build_engine/target_map/target_cache.hpp"
+#include "src/buildtool/common/statistics.hpp"
 #include "src/buildtool/common/tree.hpp"
 #include "src/buildtool/logging/logger.hpp"
 #include "src/buildtool/multithreading/task.hpp"
@@ -252,6 +253,12 @@ class ResultTargetMap {
                         });
         result.actions.erase(lastaction, result.actions.end());
 
+        int trees_traversed = Statistics::Instance().TreesAnalysedCounter();
+        if (trees_traversed > 0) {
+            Logger::Log(LogLevel::Performance,
+                        "Analysed {} non-known source trees",
+                        trees_traversed);
+        }
         Logger::Log(LogLevel::Info,
                     "Discovered {} actions, {} trees, {} blobs",
                     result.actions.size(),
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;
 
diff --git a/src/buildtool/common/statistics.hpp b/src/buildtool/common/statistics.hpp
index e34ccd03..071fc199 100644
--- a/src/buildtool/common/statistics.hpp
+++ b/src/buildtool/common/statistics.hpp
@@ -18,6 +18,7 @@ class Statistics {
         num_actions_flaky_tainted_ = 0;
         num_rebuilt_actions_compared_ = 0;
         num_rebuilt_actions_missing_ = 0;
+        num_trees_analysed_ = 0;
     }
     void IncrementActionsQueuedCounter() noexcept { ++num_actions_queued_; }
     void IncrementActionsExecutedCounter() noexcept { ++num_actions_executed_; }
@@ -37,6 +38,7 @@ class Statistics {
     void IncrementExportsNotEligibleCounter() noexcept {
         ++num_exports_not_eligible_;
     }
+    void IncrementTreesAnalysedCounter() noexcept { ++num_trees_analysed_; }
     [[nodiscard]] auto ActionsQueuedCounter() const noexcept -> int {
         return num_actions_queued_;
     }
@@ -67,6 +69,9 @@ class Statistics {
     [[nodiscard]] auto ExportsNotEligibleCounter() const noexcept -> int {
         return num_exports_not_eligible_;
     }
+    [[nodiscard]] auto TreesAnalysedCounter() const noexcept -> int {
+        return num_trees_analysed_;
+    }
 
   private:
     std::atomic<int> num_actions_queued_{};
@@ -79,6 +84,7 @@ class Statistics {
     std::atomic<int> num_exports_cached_{};
     std::atomic<int> num_exports_uncached_{};
     std::atomic<int> num_exports_not_eligible_{};
+    std::atomic<int> num_trees_analysed_{};
 };
 
 #endif  // INCLUDED_SRC_BUILDTOOL_COMMON_STATISTICS_HPP