Index: include/llvm/IR/LegacyPassManagers.h
===================================================================
--- include/llvm/IR/LegacyPassManagers.h
+++ include/llvm/IR/LegacyPassManagers.h
@@ -186,6 +186,12 @@
   /// Set pass P as the last user of the given analysis passes.
   void setLastUser(ArrayRef<Pass*> AnalysisPasses, Pass *P);
 
+  /// Set pass P as locked for last use changes.
+  void setLockedLastUse(const Pass *P);
+
+  /// Determine if the last use of pass P is unlocked.
+  bool isLastUseUnlocked(const Pass *P);
+
   /// Collect passes whose last user is P
   void collectLastUses(SmallVectorImpl<Pass *> &LastUses, Pass *P);
 
@@ -239,6 +245,10 @@
   // LastUser->second is the last user of Lastuser->first.
   DenseMap<Pass *, Pass *> LastUser;
 
+  // Map to keep track of locks on last use. A pass has its
+  // last use locked when the pass is no longer preserved.
+  SmallVector<const Pass *, 16> LockedLastUse;
+
   // Map to keep track of passes that are last used by a pass.
   // This inverse map is initialized at PM->run() based on
   // LastUser map.
@@ -420,6 +430,10 @@
   bool isPassDebuggingExecutionsOrMore() const;
 
 private:
+  void removeNotPreservedAnalysis(Pass *P,
+      const AnalysisUsage::VectorType &PreservedSet,
+      DenseMap<AnalysisID, Pass*> &AnalysisSet);
+
   void dumpAnalysisUsage(StringRef Msg, const Pass *P,
                          const AnalysisUsage::VectorType &Set) const;
 
Index: lib/IR/LegacyPassManager.cpp
===================================================================
--- lib/IR/LegacyPassManager.cpp
+++ lib/IR/LegacyPassManager.cpp
@@ -497,6 +497,18 @@
   activeStack.push(PMDM);
 }
 
+/// Set pass P as locked for last use changes.
+void PMTopLevelManager::setLockedLastUse(const Pass *P) {
+  LockedLastUse.push_back(P);
+}
+
+/// Determine if the last use of pass P is unlocked.
+bool PMTopLevelManager::isLastUseUnlocked(const Pass *P) {
+  for (const Pass *Locked : LockedLastUse)
+    if (P == Locked) return false;
+  return true;
+}
+
 /// Set pass P as the last user of the given analysis passes.
 void
 PMTopLevelManager::setLastUser(ArrayRef<Pass*> AnalysisPasses, Pass *P) {
@@ -505,7 +517,8 @@
     PDepth = P->getResolver()->getPMDataManager().getDepth();
 
   for (Pass *AP : AnalysisPasses) {
-    LastUser[AP] = P;
+    if (isLastUseUnlocked(AP))
+      LastUser[AP] = P;
 
     if (P == AP)
       continue;
@@ -543,7 +556,8 @@
       if (LUI->second == AP)
         // DenseMap iterator is not invalidated here because
         // this is just updating existing entries.
-        LastUser[LUI->first] = P;
+        if (isLastUseUnlocked(LUI->first))
+          LastUser[LUI->first] = P;
     }
   }
 }
@@ -870,28 +884,35 @@
   }
 }
 
-/// Remove Analysis not preserved by Pass P
-void PMDataManager::removeNotPreservedAnalysis(Pass *P) {
-  AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);
-  if (AnUsage->getPreservesAll())
-    return;
-
-  const AnalysisUsage::VectorType &PreservedSet = AnUsage->getPreservedSet();
-  for (DenseMap<AnalysisID, Pass*>::iterator I = AvailableAnalysis.begin(),
-         E = AvailableAnalysis.end(); I != E; ) {
+void PMDataManager::removeNotPreservedAnalysis(Pass *P,
+    const AnalysisUsage::VectorType &PreservedSet,
+    DenseMap<AnalysisID, Pass*> &AnalysisSet) {
+  for (DenseMap<AnalysisID, Pass*>::iterator I = AnalysisSet.begin(),
+         E = AnalysisSet.end(); I != E; ) {
     DenseMap<AnalysisID, Pass*>::iterator Info = I++;
     if (Info->second->getAsImmutablePass() == nullptr &&
         std::find(PreservedSet.begin(), PreservedSet.end(), Info->first) ==
         PreservedSet.end()) {
       // Remove this analysis
+      Pass *S = Info->second;
       if (PassDebugging >= Details) {
-        Pass *S = Info->second;
         dbgs() << " -- '" <<  P->getPassName() << "' is not preserving '";
         dbgs() << S->getPassName() << "'\n";
       }
-      AvailableAnalysis.erase(Info);
+      TPM->setLockedLastUse(S);
+      AnalysisSet.erase(Info);
     }
   }
+}
+
+/// Remove Analysis not preserved by Pass P
+void PMDataManager::removeNotPreservedAnalysis(Pass *P) {
+  AnalysisUsage *AnUsage = TPM->findAnalysisUsage(P);
+  if (AnUsage->getPreservesAll())
+    return;
+
+  const AnalysisUsage::VectorType &PreservedSet = AnUsage->getPreservedSet();
+  removeNotPreservedAnalysis(P, PreservedSet, AvailableAnalysis);
 
   // Check inherited analysis also. If P is not preserving analysis
   // provided by parent manager then remove it here.
@@ -900,22 +921,7 @@
     if (!InheritedAnalysis[Index])
       continue;
 
-    for (DenseMap<AnalysisID, Pass*>::iterator
-           I = InheritedAnalysis[Index]->begin(),
-           E = InheritedAnalysis[Index]->end(); I != E; ) {
-      DenseMap<AnalysisID, Pass *>::iterator Info = I++;
-      if (Info->second->getAsImmutablePass() == nullptr &&
-          std::find(PreservedSet.begin(), PreservedSet.end(), Info->first) ==
-             PreservedSet.end()) {
-        // Remove this analysis
-        if (PassDebugging >= Details) {
-          Pass *S = Info->second;
-          dbgs() << " -- '" <<  P->getPassName() << "' is not preserving '";
-          dbgs() << S->getPassName() << "'\n";
-        }
-        InheritedAnalysis[Index]->erase(Info);
-      }
-    }
+    removeNotPreservedAnalysis(P, PreservedSet, *InheritedAnalysis[Index]);
   }
 }
 
Index: test/Feature/legacypassmanager.ll
===================================================================
--- /dev/null
+++ test/Feature/legacypassmanager.ll
@@ -0,0 +1,19 @@
+; RUN: opt < %s -S -globals-aa -lcssa -argpromotion
+;
+; This is to verify a fix to bug 27050. The opt arguments expands to a series
+; that involves -basiccg twice. Before the fix, both those CallGraphs were
+; live at the same time during execution, which caused a value handle assert
+; during argpromotion since only the latest CG's asserting value handles were
+; removed when a function was deleted.
+
+%rec = type { i8 }
+
+define void @bar() {
+  call void @foo(%rec* undef)
+  ret void
+}
+
+define internal void @foo(%rec* %par0) {
+  ret void
+}
+