From 6b1852874325520a418eb05ec3c2149c2eb194a2 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 1 Dec 2015 10:44:48 -0500
Subject: [PATCH 1/2] cmOrderDirectories: Factor out directory comparison

Create an `IsSameDirectory` helper method.
---
 Source/cmOrderDirectories.cxx | 13 +++++++++----
 Source/cmOrderDirectories.h   |  3 +++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/Source/cmOrderDirectories.cxx b/Source/cmOrderDirectories.cxx
index 35ee12709..94912049b 100644
--- a/Source/cmOrderDirectories.cxx
+++ b/Source/cmOrderDirectories.cxx
@@ -73,10 +73,8 @@ public:
       {
       // Check if this directory conflicts with the entry.
       std::string const& dir = this->OD->OriginalDirectories[i];
-      if(dir != this->Directory &&
-         cmSystemTools::GetRealPath(dir) !=
-         cmSystemTools::GetRealPath(this->Directory) &&
-         this->FindConflict(dir))
+      if (!this->OD->IsSameDirectory(dir, this->Directory) &&
+          this->FindConflict(dir))
         {
         // The library will be found in this directory but this is not
         // the directory named for it.  Add an entry to make sure the
@@ -639,3 +637,10 @@ void cmOrderDirectories::DiagnoseCycle()
     ->IssueMessage(cmake::WARNING, e.str(),
                    this->Target->Target->GetBacktrace());
 }
+
+bool cmOrderDirectories::IsSameDirectory(std::string const& l,
+                                         std::string const& r)
+{
+  return (l == r ||
+          cmSystemTools::GetRealPath(l) == cmSystemTools::GetRealPath(r));
+}
diff --git a/Source/cmOrderDirectories.h b/Source/cmOrderDirectories.h
index 211c786d5..0657e92dc 100644
--- a/Source/cmOrderDirectories.h
+++ b/Source/cmOrderDirectories.h
@@ -80,6 +80,9 @@ private:
   struct ConflictList: public std::vector<ConflictPair> {};
   std::vector<ConflictList> ConflictGraph;
 
+  // Compare directories after resolving symlinks.
+  bool IsSameDirectory(std::string const& l, std::string const& r);
+
   friend class cmOrderDirectoriesConstraint;
   friend class cmOrderDirectoriesConstraintLibrary;
 };

From 4e3cf8b012404e4d9602c16d473480cc3d0c7928 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 1 Dec 2015 10:57:33 -0500
Subject: [PATCH 2/2] cmOrderDirectories: Reduce repeat realpath() calls

Since commit v3.1.0-rc1~110^2 (Tolerate symlinks during RPATH ordering,
2014-09-09) we call realpath() for every directory ordering constraint
check.  On some platforms/filesystems this is slow, so memoize the
result of the call for each directory.
---
 Source/cmOrderDirectories.cxx | 17 +++++++++++++++--
 Source/cmOrderDirectories.h   |  3 +++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/Source/cmOrderDirectories.cxx b/Source/cmOrderDirectories.cxx
index 94912049b..e3406a83e 100644
--- a/Source/cmOrderDirectories.cxx
+++ b/Source/cmOrderDirectories.cxx
@@ -641,6 +641,19 @@ void cmOrderDirectories::DiagnoseCycle()
 bool cmOrderDirectories::IsSameDirectory(std::string const& l,
                                          std::string const& r)
 {
-  return (l == r ||
-          cmSystemTools::GetRealPath(l) == cmSystemTools::GetRealPath(r));
+  return this->GetRealPath(l) == this->GetRealPath(r);
+}
+
+std::string const& cmOrderDirectories::GetRealPath(std::string const& dir)
+{
+  std::map<std::string, std::string>::iterator i =
+    this->RealPaths.lower_bound(dir);
+  if (i == this->RealPaths.end() ||
+      this->RealPaths.key_comp()(dir, i->first))
+    {
+    typedef std::map<std::string, std::string>::value_type value_type;
+    i = this->RealPaths.insert(
+      i, value_type(dir, cmSystemTools::GetRealPath(dir)));
+    }
+  return i->second;
 }
diff --git a/Source/cmOrderDirectories.h b/Source/cmOrderDirectories.h
index 0657e92dc..477216bbd 100644
--- a/Source/cmOrderDirectories.h
+++ b/Source/cmOrderDirectories.h
@@ -83,6 +83,9 @@ private:
   // Compare directories after resolving symlinks.
   bool IsSameDirectory(std::string const& l, std::string const& r);
 
+  std::string const& GetRealPath(std::string const& dir);
+  std::map<std::string, std::string> RealPaths;
+
   friend class cmOrderDirectoriesConstraint;
   friend class cmOrderDirectoriesConstraintLibrary;
 };