Index: llvm/trunk/include/llvm/IR/LegacyPassManagers.h
===================================================================
--- llvm/trunk/include/llvm/IR/LegacyPassManagers.h
+++ llvm/trunk/include/llvm/IR/LegacyPassManagers.h
@@ -195,6 +195,9 @@
   /// then return NULL.
   Pass *findAnalysisPass(AnalysisID AID);
 
+  /// Retrieve the PassInfo for an analysis.
+  const PassInfo *findAnalysisPassInfo(AnalysisID AID) const;
+
   /// Find analysis usage information for the pass P.
   AnalysisUsage *findAnalysisUsage(Pass *P);
 
@@ -251,6 +254,12 @@
   SmallVector<ImmutablePass *, 16> ImmutablePasses;
 
   DenseMap<Pass *, AnalysisUsage *> AnUsageMap;
+
+  /// Collection of PassInfo objects found via analysis IDs and in this top
+  /// level manager. This is used to memoize queries to the pass registry.
+  /// FIXME: This is an egregious hack because querying the pass registry is
+  /// either slow or racy.
+  mutable DenseMap<AnalysisID, const PassInfo *> AnalysisPassInfos;
 };
 
 
Index: llvm/trunk/lib/IR/LegacyPassManager.cpp
===================================================================
--- llvm/trunk/lib/IR/LegacyPassManager.cpp
+++ llvm/trunk/lib/IR/LegacyPassManager.cpp
@@ -600,8 +600,7 @@
   // If P is an analysis pass and it is available then do not
   // generate the analysis again. Stale analysis info should not be
   // available at this point.
-  const PassInfo *PI =
-    PassRegistry::getPassRegistry()->getPassInfo(P->getPassID());
+  const PassInfo *PI = findAnalysisPassInfo(P->getPassID());
   if (PI && PI->isAnalysis() && findAnalysisPass(P->getPassID())) {
     delete P;
     return;
@@ -619,7 +618,7 @@
 
       Pass *AnalysisPass = findAnalysisPass(*I);
       if (!AnalysisPass) {
-        const PassInfo *PI = PassRegistry::getPassRegistry()->getPassInfo(*I);
+        const PassInfo *PI = findAnalysisPassInfo(*I);
 
         if (!PI) {
           // Pass P is not in the global PassRegistry
@@ -716,8 +715,7 @@
       return *I;
 
     // If Pass not found then check the interfaces implemented by Immutable Pass
-    const PassInfo *PassInf =
-      PassRegistry::getPassRegistry()->getPassInfo(PI);
+    const PassInfo *PassInf = findAnalysisPassInfo(PI);
     assert(PassInf && "Expected all immutable passes to be initialized");
     const std::vector<const PassInfo*> &ImmPI =
       PassInf->getInterfacesImplemented();
@@ -731,6 +729,17 @@
   return nullptr;
 }
 
+const PassInfo *PMTopLevelManager::findAnalysisPassInfo(AnalysisID AID) const {
+  const PassInfo *&PI = AnalysisPassInfos[AID];
+  if (!PI)
+    PI = PassRegistry::getPassRegistry()->getPassInfo(AID);
+  else
+    assert(PI == PassRegistry::getPassRegistry()->getPassInfo(AID) &&
+           "The pass info pointer changed for an analysis ID!");
+
+  return PI;
+}
+
 // Print passes managed by this top level manager.
 void PMTopLevelManager::dumpPasses() const {
 
@@ -759,8 +768,7 @@
   dbgs() << "Pass Arguments: ";
   for (SmallVectorImpl<ImmutablePass *>::const_iterator I =
        ImmutablePasses.begin(), E = ImmutablePasses.end(); I != E; ++I)
-    if (const PassInfo *PI =
-        PassRegistry::getPassRegistry()->getPassInfo((*I)->getPassID())) {
+    if (const PassInfo *PI = findAnalysisPassInfo((*I)->getPassID())) {
       assert(PI && "Expected all immutable passes to be initialized");
       if (!PI->isAnalysisGroup())
         dbgs() << " -" << PI->getPassArgument();
@@ -824,7 +832,7 @@
 
   // This pass is the current implementation of all of the interfaces it
   // implements as well.
-  const PassInfo *PInf = PassRegistry::getPassRegistry()->getPassInfo(PI);
+  const PassInfo *PInf = TPM->findAnalysisPassInfo(PI);
   if (!PInf) return;
   const std::vector<const PassInfo*> &II = PInf->getInterfacesImplemented();
   for (unsigned i = 0, e = II.size(); i != e; ++i)
@@ -957,7 +965,7 @@
   }
 
   AnalysisID PI = P->getPassID();
-  if (const PassInfo *PInf = PassRegistry::getPassRegistry()->getPassInfo(PI)) {
+  if (const PassInfo *PInf = TPM->findAnalysisPassInfo(PI)) {
     // Remove the pass itself (if it is not already removed).
     AvailableAnalysis.erase(PI);
 
@@ -1037,7 +1045,7 @@
   for (SmallVectorImpl<AnalysisID>::iterator
          I = ReqAnalysisNotAvailable.begin(),
          E = ReqAnalysisNotAvailable.end() ;I != E; ++I) {
-    const PassInfo *PI = PassRegistry::getPassRegistry()->getPassInfo(*I);
+    const PassInfo *PI = TPM->findAnalysisPassInfo(*I);
     Pass *AnalysisPass = PI->createPass();
     this->addLowerLevelRequiredPass(P, AnalysisPass);
   }
@@ -1142,7 +1150,7 @@
       PMD->dumpPassArguments();
     else
       if (const PassInfo *PI =
-            PassRegistry::getPassRegistry()->getPassInfo((*I)->getPassID()))
+            TPM->findAnalysisPassInfo((*I)->getPassID()))
         if (!PI->isAnalysisGroup())
           dbgs() << " -" << PI->getPassArgument();
   }
@@ -1218,7 +1226,7 @@
   dbgs() << (const void*)P << std::string(getDepth()*2+3, ' ') << Msg << " Analyses:";
   for (unsigned i = 0; i != Set.size(); ++i) {
     if (i) dbgs() << ',';
-    const PassInfo *PInf = PassRegistry::getPassRegistry()->getPassInfo(Set[i]);
+    const PassInfo *PInf = TPM->findAnalysisPassInfo(Set[i]);
     if (!PInf) {
       // Some preserved passes, such as AliasAnalysis, may not be initialized by
       // all drivers.
@@ -1658,8 +1666,8 @@
 
     OnTheFlyManagers[P] = FPP;
   }
-  const PassInfo * RequiredPassPI =
-    PassRegistry::getPassRegistry()->getPassInfo(RequiredPass->getPassID());
+  const PassInfo *RequiredPassPI =
+      TPM->findAnalysisPassInfo(RequiredPass->getPassID());
 
   Pass *FoundPass = nullptr;
   if (RequiredPassPI && RequiredPassPI->isAnalysis()) {