Memoise checkSourcePath()

This prevents hydra-eval-jobs from statting the same files over and
over again.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 86e93a5ac9..8594a2707d 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -7,6 +7,7 @@
 #include "hash.hh"
 
 #include <map>
+#include <unordered_map>
 
 
 namespace nix {
@@ -100,6 +101,9 @@ private:
 
     std::map<std::string, std::pair<bool, std::string>> searchPathResolved;
 
+    /* Cache used by checkSourcePath(). */
+    std::unordered_map<Path, Path> resolvedPaths;
+
 public:
 
     EvalState(const Strings & _searchPath, ref<Store> store);