Ninja: Cache ConvertToNinjaPath results to avoid repeat work

Calls to this method may dominate generation time in some cases.
Measurements for configuring cmake itself show a cache hit rate of ~57%
(7753 total calls, 4453 cache hits).  For a larger project (that also
makes use of custom targets as prerequisite for all compile targets),
the measured cache hit ratio is ~96% (2530827 total calls, 2433124 cache
hits).  For this project the observable cmake runtime could be reduced
from 40s to 30s.

Signed-off-by: Matthias Maennich <matthias@maennich.net>

1 files changed, 5 insertions, 1 deletions

diff --git a/Source/cmGlobalNinjaGenerator.h b/Source/cmGlobalNinjaGenerator.h
index 00bf91c..7f80d08 100644
--- a/Source/cmGlobalNinjaGenerator.h
+++ b/Source/cmGlobalNinjaGenerator.h
@@ -9,6 +9,7 @@
 #include <map>
 #include <set>
 #include <string>
+#include <unordered_map>
 #include <utility>
 #include <vector>
 
@@ -245,7 +246,7 @@ public:
     return this->RulesFileStream;
   }
 
-  std::string ConvertToNinjaPath(const std::string& path) const;
+  std::string const& ConvertToNinjaPath(const std::string& path) const;
 
   struct MapToNinjaPathImpl
   {
@@ -452,6 +453,9 @@ private:
 
   std::map<cmGeneratorTarget const*, cmNinjaOuts> TargetDependsClosures;
 
+  /// the local cache for calls to ConvertToNinjaPath
+  mutable std::unordered_map<std::string, std::string> ConvertToNinjaPathCache;
+
   std::string NinjaCommand;
   std::string NinjaVersion;
   bool NinjaSupportsConsolePool;