Index: llvm/trunk/include/llvm/IR/LegacyPassManagers.h
===================================================================
--- llvm/trunk/include/llvm/IR/LegacyPassManagers.h
+++ llvm/trunk/include/llvm/IR/LegacyPassManagers.h
@@ -320,12 +320,12 @@
   bool preserveHigherLevelAnalysis(Pass *P);
 
 
-  /// Populate RequiredPasses with analysis pass that are required by
-  /// pass P and are available. Populate ReqPassNotAvailable with analysis
-  /// pass that are required by pass P but are not available.
-  void collectRequiredAnalysis(SmallVectorImpl<Pass *> &RequiredPasses,
-                               SmallVectorImpl<AnalysisID> &ReqPassNotAvailable,
-                               Pass *P);
+  /// Populate UsedPasses with analysis pass that are used or required by pass
+  /// P and are available. Populate ReqPassNotAvailable with analysis pass that
+  /// are required by pass P but are not available.
+  void collectRequiredAndUsedAnalyses(
+      SmallVectorImpl<Pass *> &UsedPasses,
+      SmallVectorImpl<AnalysisID> &ReqPassNotAvailable, Pass *P);
 
   /// All Required analyses should be available to the pass as it runs!  Here
   /// we fill in the AnalysisImpls member of the pass so that it can
@@ -351,6 +351,7 @@
                     enum PassDebuggingString S2, StringRef Msg);
   void dumpRequiredSet(const Pass *P) const;
   void dumpPreservedSet(const Pass *P) const;
+  void dumpUsedSet(const Pass *P) const;
 
   unsigned getNumContainedPasses() const {
     return (unsigned)PassVector.size();
Index: llvm/trunk/include/llvm/PassAnalysisSupport.h
===================================================================
--- llvm/trunk/include/llvm/PassAnalysisSupport.h
+++ llvm/trunk/include/llvm/PassAnalysisSupport.h
@@ -40,7 +40,7 @@
 
 private:
   /// Sets of analyses required and preserved by a pass
-  VectorType Required, RequiredTransitive, Preserved;
+  VectorType Required, RequiredTransitive, Preserved, Used;
   bool PreservesAll;
 
 public:
@@ -80,6 +80,25 @@
   }
   ///@}
 
+  ///@{
+  /// Add the specified ID to the set of analyses used by this pass if they are
+  /// available..
+  AnalysisUsage &addUsedIfAvailableID(const void *ID) {
+    Used.push_back(ID);
+    return *this;
+  }
+  AnalysisUsage &addUsedIfAvailableID(char &ID) {
+    Used.push_back(&ID);
+    return *this;
+  }
+  /// Add the specified Pass class to the set of analyses used by this pass.
+  template<class PassClass>
+  AnalysisUsage &addUsedIfAvailable() {
+    Used.push_back(&PassClass::ID);
+    return *this;
+  }
+  ///@}
+
   /// Add the Pass with the specified argument string to the set of analyses
   /// preserved by this pass. If no such Pass exists, do nothing. This can be
   /// useful when a pass is trivially preserved, but may not be linked in. Be
@@ -107,6 +126,7 @@
     return RequiredTransitive;
   }
   const VectorType &getPreservedSet() const { return Preserved; }
+  const VectorType &getUsedSet() const { return Used; }
 };
 
 //===----------------------------------------------------------------------===//
Index: llvm/trunk/lib/IR/LegacyPassManager.cpp
===================================================================
--- llvm/trunk/lib/IR/LegacyPassManager.cpp
+++ llvm/trunk/lib/IR/LegacyPassManager.cpp
@@ -989,29 +989,28 @@
 
   // At the moment, this pass is the last user of all required passes.
   SmallVector<Pass *, 12> LastUses;
-  SmallVector<Pass *, 8> RequiredPasses;
+  SmallVector<Pass *, 8> UsedPasses;
   SmallVector<AnalysisID, 8> ReqAnalysisNotAvailable;
 
   unsigned PDepth = this->getDepth();
 
-  collectRequiredAnalysis(RequiredPasses,
-                          ReqAnalysisNotAvailable, P);
-  for (Pass *PRequired : RequiredPasses) {
+  collectRequiredAndUsedAnalyses(UsedPasses, ReqAnalysisNotAvailable, P);
+  for (Pass *PUsed : UsedPasses) {
     unsigned RDepth = 0;
 
-    assert(PRequired->getResolver() && "Analysis Resolver is not set");
-    PMDataManager &DM = PRequired->getResolver()->getPMDataManager();
+    assert(PUsed->getResolver() && "Analysis Resolver is not set");
+    PMDataManager &DM = PUsed->getResolver()->getPMDataManager();
     RDepth = DM.getDepth();
 
     if (PDepth == RDepth)
-      LastUses.push_back(PRequired);
+      LastUses.push_back(PUsed);
     else if (PDepth > RDepth) {
       // Let the parent claim responsibility of last use
-      TransferLastUses.push_back(PRequired);
+      TransferLastUses.push_back(PUsed);
       // Keep track of higher level analysis used by this manager.
-      HigherLevelAnalysis.push_back(PRequired);
+      HigherLevelAnalysis.push_back(PUsed);
     } else
-      llvm_unreachable("Unable to accommodate Required Pass");
+      llvm_unreachable("Unable to accommodate Used Pass");
   }
 
   // Set P as P's last user until someone starts using P.
@@ -1044,22 +1043,27 @@
 }
 
 
-/// Populate RP with analysis pass that are required by
+/// Populate UP with analysis pass that are used or required by
 /// pass P and are available. Populate RP_NotAvail with analysis
 /// pass that are required by pass P but are not available.
-void PMDataManager::collectRequiredAnalysis(SmallVectorImpl<Pass *> &RP,
-                                       SmallVectorImpl<AnalysisID> &RP_NotAvail,
-                                            Pass *P) {
+void PMDataManager::collectRequiredAndUsedAnalyses(
+    SmallVectorImpl<Pass *> &UP, SmallVectorImpl<AnalysisID> &RP_NotAvail,
+    Pass *P) {
   AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);
+
+  for (const auto &UsedID : AnUsage->getUsedSet())
+    if (Pass *AnalysisPass = findAnalysisPass(UsedID, true))
+      UP.push_back(AnalysisPass);
+
   for (const auto &RequiredID : AnUsage->getRequiredSet())
     if (Pass *AnalysisPass = findAnalysisPass(RequiredID, true))
-      RP.push_back(AnalysisPass);
+      UP.push_back(AnalysisPass);
     else
       RP_NotAvail.push_back(RequiredID);
 
   for (const auto &RequiredID : AnUsage->getRequiredTransitiveSet())
     if (Pass *AnalysisPass = findAnalysisPass(RequiredID, true))
-      RP.push_back(AnalysisPass);
+      UP.push_back(AnalysisPass);
     else
       RP_NotAvail.push_back(RequiredID);
 }
@@ -1196,6 +1200,15 @@
   dumpAnalysisUsage("Preserved", P, analysisUsage.getPreservedSet());
 }
 
+void PMDataManager::dumpUsedSet(const Pass *P) const {
+  if (PassDebugging < Details)
+    return;
+
+  AnalysisUsage analysisUsage;
+  P->getAnalysisUsage(analysisUsage);
+  dumpAnalysisUsage("Used", P, analysisUsage.getUsedSet());
+}
+
 void PMDataManager::dumpAnalysisUsage(StringRef Msg, const Pass *P,
                                    const AnalysisUsage::VectorType &Set) const {
   assert(PassDebugging >= Details);
@@ -1300,6 +1313,7 @@
         dumpPassInfo(BP, MODIFICATION_MSG, ON_BASICBLOCK_MSG,
                      I->getName());
       dumpPreservedSet(BP);
+      dumpUsedSet(BP);
 
       verifyPreservedAnalysis(BP);
       removeNotPreservedAnalysis(BP);
@@ -1514,6 +1528,7 @@
     if (LocalChanged)
       dumpPassInfo(FP, MODIFICATION_MSG, ON_FUNCTION_MSG, F.getName());
     dumpPreservedSet(FP);
+    dumpUsedSet(FP);
 
     verifyPreservedAnalysis(FP);
     removeNotPreservedAnalysis(FP);
@@ -1591,6 +1606,7 @@
       dumpPassInfo(MP, MODIFICATION_MSG, ON_MODULE_MSG,
                    M.getModuleIdentifier());
     dumpPreservedSet(MP);
+    dumpUsedSet(MP);
 
     verifyPreservedAnalysis(MP);
     removeNotPreservedAnalysis(MP);