2 files changed, 21 insertions, 4 deletions
diff --git a/include/llvm/PassManagers.h b/include/llvm/PassManagers.h
index bd3672f944..4b82c98985 100644
--- a/include/llvm/PassManagers.h
+++ b/include/llvm/PassManagers.h
@@ -120,6 +120,10 @@ public:
   /// Collect passes whose last user is P
   void collectLastUses(std::vector<Pass *> &LastUses, Pass *P);
 
+  // Walk LastUser map and create inverted map. This should be done
+  // after all passes are added and before running first pass.
+  void collectInvertedLU();
+
   /// Find the pass that implements Analysis AID. Search immutable
   /// passes and all pass managers. If desired pass is not found
   /// then return NULL.
@@ -171,6 +175,7 @@ private:
   // Map to keep track of last user of the analysis pass.
   // LastUser->second is the last user of Lastuser->first.
   std::map<Pass *, Pass *> LastUser;
+  std::map<Pass *, std::vector <Pass *> > InvertedLU;
 
   /// Immutable passes are managed by top level manager.
   std::vector<ImmutablePass *> ImmutablePasses;
diff --git a/lib/VMCore/PassManager.cpp b/lib/VMCore/PassManager.cpp
index bc85967ee1..6c1f2360d8 100644
--- a/lib/VMCore/PassManager.cpp
+++ b/lib/VMCore/PassManager.cpp
@@ -362,13 +362,19 @@ void PMTopLevelManager::setLastUser(std::vector<Pass *> &AnalysisPasses,
   }
 }
 
+// Walk LastUser map and create inverted map. This should be done
+// after all passes are added and before running first pass.
+void PMTopLevelManager::collectInvertedLU() {
+   for (std::map<Pass *, Pass *>::iterator LUI = LastUser.begin(),
+          LUE = LastUser.end(); LUI != LUE; ++LUI)
+     InvertedLU[LUI->second].push_back(LUI->first);
+}
+
 /// Collect passes whose last user is P
 void PMTopLevelManager::collectLastUses(std::vector<Pass *> &LastUses,
                                             Pass *P) {
-   for (std::map<Pass *, Pass *>::iterator LUI = LastUser.begin(),
-          LUE = LastUser.end(); LUI != LUE; ++LUI)
-      if (LUI->second == P)
-        LastUses.push_back(LUI->first);
+   std::vector<Pass *>&LU = InvertedLU[P]; 
+   LastUses.insert(LastUses.end(), LU.begin(), LU.end());
 }
 
 /// Schedule pass P for execution. Make sure that passes required by
@@ -938,6 +944,9 @@ bool FunctionPassManagerImpl::run(Function &F) {
   dumpArguments();
   dumpPasses();
 
+  // Collect inverted map of LastUsers. This improves speed of
+  // collectLastUses().
+  TPM->collectInvertedLU();
   initializeAllAnalysisInfo();
   for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index) {  
     FPPassManager *FP = getContainedManager(Index);
@@ -1086,6 +1095,9 @@ bool PassManagerImpl::run(Module &M) {
   dumpArguments();
   dumpPasses();
 
+  // Collect inverted map of LastUsers. This improves speed of
+  // collectLastUses().
+  TPM->collectInvertedLU();
   initializeAllAnalysisInfo();
   for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index) {  
     MPPassManager *MP = getContainedManager(Index);