Index: include/llvm/Pass.h
===================================================================
--- include/llvm/Pass.h
+++ include/llvm/Pass.h
@@ -82,16 +82,21 @@
   AnalysisResolver *Resolver;  // Used to resolve analysis
   const void *PassID;
   PassKind Kind;
+  bool Unavailable;
   void operator=(const Pass&) = delete;
   Pass(const Pass &) = delete;
 
 public:
   explicit Pass(PassKind K, char &pid)
-    : Resolver(nullptr), PassID(&pid), Kind(K) { }
+    : Resolver(nullptr), PassID(&pid), Kind(K), Unavailable(false) { }
   virtual ~Pass();
 
-
   PassKind getPassKind() const { return Kind; }
+  bool isAvailable() const { return !Unavailable; }
+
+  /// Sets a flag to indicates that the pass does not have results, either
+  /// because it was skipped or is already freed.
+  void markUnavailable(bool x = true) { Unavailable = x; }
 
   /// getPassName - Return a nice clean name for a pass.  This usually
   /// implemented in terms of the name that is registered by one of the
@@ -316,8 +321,9 @@
 protected:
   /// Optional passes call this function to check whether the pass should be
   /// skipped. This is the case when Attribute::OptimizeNone is set or when
-  /// optimization bisect is over the limit.
-  bool skipFunction(const Function &F) const;
+  /// optimization bisect is over the limit. It also sets flag Unavailable on
+  /// the pass.
+  bool skipFunction(const Function &F);
 };
 
 
Index: lib/CodeGen/MachineDominators.cpp
===================================================================
--- lib/CodeGen/MachineDominators.cpp
+++ lib/CodeGen/MachineDominators.cpp
@@ -69,7 +69,7 @@
 }
 
 void MachineDominatorTree::verifyAnalysis() const {
-  if (VerifyMachineDomInfo)
+  if (VerifyMachineDomInfo && isAvailable())
     verifyDomTree();
 }
 
Index: lib/CodeGen/MachineFunctionPass.cpp
===================================================================
--- lib/CodeGen/MachineFunctionPass.cpp
+++ lib/CodeGen/MachineFunctionPass.cpp
@@ -38,8 +38,10 @@
 bool MachineFunctionPass::runOnFunction(Function &F) {
   // Do not codegen any 'available_externally' functions at all, they have
   // definitions outside the translation unit.
-  if (F.hasAvailableExternallyLinkage())
+  if (F.hasAvailableExternallyLinkage()) {
+    markUnavailable();
     return false;
+  }
 
   MachineModuleInfo &MMI = getAnalysis<MachineModuleInfo>();
   MachineFunction &MF = MMI.getMachineFunction(F);
Index: lib/IR/Pass.cpp
===================================================================
--- lib/IR/Pass.cpp
+++ lib/IR/Pass.cpp
@@ -146,13 +146,16 @@
   return PMT_FunctionPassManager;
 }
 
-bool FunctionPass::skipFunction(const Function &F) const {
-  if (!F.getContext().getOptBisect().shouldRunPass(this, F))
+bool FunctionPass::skipFunction(const Function &F) {
+  if (!F.getContext().getOptBisect().shouldRunPass(this, F)) {
+    markUnavailable();
     return true;
+  }
 
   if (F.hasFnAttribute(Attribute::OptimizeNone)) {
     DEBUG(dbgs() << "Skipping pass '" << getPassName() << "' on function "
                  << F.getName() << "\n");
+    markUnavailable();
     return true;
   }
   return false;
Index: test/CodeGen/Generic/externally_available.ll
===================================================================
--- test/CodeGen/Generic/externally_available.ll
+++ test/CodeGen/Generic/externally_available.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s | not grep test_
+; RUN: llc -verify-machine-dom-info < %s | not grep test_
 
 ; test_function should not be emitted to the .s file.
 define available_externally i32 @test_function() {