Speed up graph traversal for project->targets map

The cmGlobalGenerator::AddTargetDepends method traces the dependencies
of targets recursively to collect the complete set of targets needed for
a given project (for VS .sln files).  This commit teaches the method to
avoid tracing its dependencies more than once.  Otherwise the code does
an all-paths walk needlessly.

1 files changed, 6 insertions, 8 deletions

diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index f4fa6f42a7..812cffde80 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -1971,14 +1971,12 @@ cmGlobalGenerator::AddTargetDepends(cmTarget* target,
                                     projectTargets)
 {
   // add the target itself
-  projectTargets.insert(target);
-  // get the direct depends of target
-  cmGlobalGenerator::TargetDependSet const& tset 
-    = this->GetTargetDirectDepends(*target);
-  if(tset.size())
-    {
-    // if there are targets that depend on target 
-    // add them and their depends as well
+  if(projectTargets.insert(target).second)
+    {
+    // This is the first time we have encountered the target.
+    // Recursively follow its dependencies.
+    cmGlobalGenerator::TargetDependSet const& tset
+      = this->GetTargetDirectDepends(*target);
     for(cmGlobalGenerator::TargetDependSet::const_iterator i =
           tset.begin(); i != tset.end(); ++i)
       {