Index: include/llvm/IR/CallSite.h
===================================================================
--- include/llvm/IR/CallSite.h
+++ include/llvm/IR/CallSite.h
@@ -475,6 +475,24 @@
     CALLSITE_DELEGATE_SETTER(setOnlyAccessesArgMemory());
   }
 
+  /// Determine if the function may only access memory that is
+  /// inaccessible from the IR.
+  bool onlyAccessesInaccessibleMemory() const {
+    CALLSITE_DELEGATE_GETTER(onlyAccessesInaccessibleMemory());
+  }
+  void setOnlyAccessesInaccessibleMemory() {
+    CALLSITE_DELEGATE_SETTER(setOnlyAccessesInaccessibleMemory());
+  }
+
+  /// Determine if the function may only access memory that is
+  /// either inaccessible from the IR or pointed to by its arguments.
+  bool onlyAccessesInaccessibleMemOrArgMem() const {
+    CALLSITE_DELEGATE_GETTER(onlyAccessesInaccessibleMemOrArgMem());
+  }
+  void setOnlyAccessesInaccessibleMemOrArgMem() {
+    CALLSITE_DELEGATE_SETTER(setOnlyAccessesInaccessibleMemOrArgMem());
+  }
+
   /// Determine if the call cannot return.
   bool doesNotReturn() const {
     CALLSITE_DELEGATE_GETTER(doesNotReturn());
Index: include/llvm/IR/InstrTypes.h
===================================================================
--- include/llvm/IR/InstrTypes.h
+++ include/llvm/IR/InstrTypes.h
@@ -1480,6 +1480,12 @@
     default:
       return false;
 
+    case Attribute::InaccessibleMemOrArgMemOnly:
+      return hasReadingOperandBundles();
+
+    case Attribute::InaccessibleMemOnly:
+      return hasReadingOperandBundles();
+
     case Attribute::ArgMemOnly:
       return hasReadingOperandBundles();
 
Index: include/llvm/IR/Instructions.h
===================================================================
--- include/llvm/IR/Instructions.h
+++ include/llvm/IR/Instructions.h
@@ -1807,6 +1807,24 @@
     addAttribute(AttributeList::FunctionIndex, Attribute::ArgMemOnly);
   }
 
+  /// @brief Determine if the function may only access memory that is
+  /// inaccessible from the IR.
+  bool onlyAccessesInaccessibleMemory() const {
+    return hasFnAttr(Attribute::InaccessibleMemOnly);
+  }
+  void setOnlyAccessesInaccessibleMemory() {
+    addAttribute(AttributeList::FunctionIndex, Attribute::InaccessibleMemOnly);
+  }
+
+  /// @brief Determine if the function may only access memory that is
+  /// either inaccessible from the IR or pointed to by its arguments.
+  bool onlyAccessesInaccessibleMemOrArgMem() const {
+    return hasFnAttr(Attribute::InaccessibleMemOrArgMemOnly);
+  }
+  void setOnlyAccessesInaccessibleMemOrArgMem() {
+    addAttribute(AttributeList::FunctionIndex, Attribute::InaccessibleMemOrArgMemOnly);
+  }
+
   /// Determine if the call cannot return.
   bool doesNotReturn() const { return hasFnAttr(Attribute::NoReturn); }
   void setDoesNotReturn() {
@@ -3889,6 +3907,24 @@
     addAttribute(AttributeList::FunctionIndex, Attribute::ArgMemOnly);
   }
 
+  /// @brief Determine if the function may only access memory that is
+  /// inaccessible from the IR.
+  bool onlyAccessesInaccessibleMemory() const {
+    return hasFnAttr(Attribute::InaccessibleMemOnly);
+  }
+  void setOnlyAccessesInaccessibleMemory() {
+    addAttribute(AttributeList::FunctionIndex, Attribute::InaccessibleMemOnly);
+  }
+
+  /// @brief Determine if the function may only access memory that is
+  /// either inaccessible from the IR or pointed to by its arguments.
+  bool onlyAccessesInaccessibleMemOrArgMem() const {
+    return hasFnAttr(Attribute::InaccessibleMemOrArgMemOnly);
+  }
+  void setOnlyAccessesInaccessibleMemOrArgMem() {
+    addAttribute(AttributeList::FunctionIndex, Attribute::InaccessibleMemOrArgMemOnly);
+  }
+
   /// Determine if the call cannot return.
   bool doesNotReturn() const { return hasFnAttr(Attribute::NoReturn); }
   void setDoesNotReturn() {
Index: lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- lib/Analysis/BasicAliasAnalysis.cpp
+++ lib/Analysis/BasicAliasAnalysis.cpp
@@ -617,6 +617,10 @@
 
   if (CS.onlyAccessesArgMemory())
     Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesArgumentPointees);
+  else if (CS.onlyAccessesInaccessibleMemory())
+    Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesInaccessibleMem);
+  else if (CS.onlyAccessesInaccessibleMemOrArgMem())
+    Min = FunctionModRefBehavior(Min & FMRB_OnlyAccessesInaccessibleOrArgMem);
 
   // If CS has operand bundles then aliasing attributes from the function it
   // calls do not directly apply to the CallSite.  This can be made more
Index: test/Analysis/BasicAA/cs-cs.ll
===================================================================
--- test/Analysis/BasicAA/cs-cs.ll
+++ test/Analysis/BasicAA/cs-cs.ll
@@ -260,3 +260,69 @@
 ; CHECK: NoModRef: call void @an_argmemonly_func(i8* %q) <-> call void @an_inaccessiblememonly_func()
 ; CHECK: Both ModRef: call void @an_argmemonly_func(i8* %q) <-> call void @an_inaccessibleorargmemonly_func(i8* %q)
 }
+
+;; test that unknown operand bundle has unknown effect to the heap
+define void @test9(i8* %p) {
+; CHECK-LABEL: Function: test9
+entry:
+  %q = getelementptr i8, i8* %p, i64 16
+  call void @a_readonly_func(i8* %p) [ "unknown"() ]
+  call void @an_inaccessiblememonly_func() [ "unknown"() ]
+  call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ]
+  call void @an_argmemonly_func(i8* %q) [ "unknown"() ]
+  ret void
+
+; CHECK: Both ModRef:  Ptr: i8* %p     <->  call void @a_readonly_func(i8* %p) [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %q     <->  call void @a_readonly_func(i8* %p) [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %p     <->  call void @an_inaccessiblememonly_func() [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %q     <->  call void @an_inaccessiblememonly_func() [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %p     <->  call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %q     <->  call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %p     <->  call void @an_argmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %q     <->  call void @an_argmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @a_readonly_func(i8* %p) [ "unknown"() ] <->   call void @an_inaccessiblememonly_func() [ "unknown"() ]
+; CHECK: Both ModRef:   call void @a_readonly_func(i8* %p) [ "unknown"() ] <->   call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @a_readonly_func(i8* %p) [ "unknown"() ] <->   call void @an_argmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessiblememonly_func() [ "unknown"() ] <->   call void @a_readonly_func(i8* %p) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessiblememonly_func() [ "unknown"() ] <->   call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessiblememonly_func() [ "unknown"() ] <->   call void @an_argmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ] <->   call void @a_readonly_func(i8* %p) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ] <->   call void @an_inaccessiblememonly_func() [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ] <->   call void @an_argmemonly_func(i8* %q) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_argmemonly_func(i8* %q) [ "unknown"() ] <->   call void @a_readonly_func(i8* %p) [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_argmemonly_func(i8* %q) [ "unknown"() ] <->   call void @an_inaccessiblememonly_func() [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_argmemonly_func(i8* %q) [ "unknown"() ] <->   call void @an_inaccessibleorargmemonly_func(i8* %q) [ "unknown"() ]
+}
+
+;; test callsite overwrite of unknown operand bundle
+define void @test10(i8* %p) {
+; CHECK-LABEL: Function: test10
+entry:
+  %q = getelementptr i8, i8* %p, i64 16
+  call void @a_readonly_func(i8* %p) readonly [ "unknown"() ]
+  call void @an_inaccessiblememonly_func() inaccessiblememonly [ "unknown"() ]
+  call void @an_inaccessibleorargmemonly_func(i8* %q) inaccessiblemem_or_argmemonly [ "unknown"() ]
+  call void @an_argmemonly_func(i8* %q) argmemonly [ "unknown"() ]
+  ret void
+
+; CHECK: Just Ref:  Ptr: i8* %p        <->  call void @a_readonly_func(i8* %p) #6 [ "unknown"() ]
+; CHECK: Just Ref:  Ptr: i8* %q        <->  call void @a_readonly_func(i8* %p) #6 [ "unknown"() ]
+; CHECK: NoModRef:  Ptr: i8* %p        <->  call void @an_inaccessiblememonly_func() #7 [ "unknown"() ]
+; CHECK: NoModRef:  Ptr: i8* %q        <->  call void @an_inaccessiblememonly_func() #7 [ "unknown"() ]
+; CHECK: NoModRef:  Ptr: i8* %p        <->  call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %q     <->  call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ]
+; CHECK: NoModRef:  Ptr: i8* %p        <->  call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ]
+; CHECK: Both ModRef:  Ptr: i8* %q     <->  call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ]
+; CHECK: Just Ref:   call void @a_readonly_func(i8* %p) #6 [ "unknown"() ] <->   call void @an_inaccessiblememonly_func() #7 [ "unknown"() ]
+; CHECK: Just Ref:   call void @a_readonly_func(i8* %p) #6 [ "unknown"() ] <->   call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ]
+; CHECK: Just Ref:   call void @a_readonly_func(i8* %p) #6 [ "unknown"() ] <->   call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessiblememonly_func() #7 [ "unknown"() ] <->   call void @a_readonly_func(i8* %p) #6 [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessiblememonly_func() #7 [ "unknown"() ] <->   call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ]
+; CHECK: NoModRef:   call void @an_inaccessiblememonly_func() #7 [ "unknown"() ] <->   call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ] <->   call void @a_readonly_func(i8* %p) #6 [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ] <->   call void @an_inaccessiblememonly_func() #7 [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ] <->   call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ] <->   call void @a_readonly_func(i8* %p) #6 [ "unknown"() ]
+; CHECK: NoModRef:   call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ] <->   call void @an_inaccessiblememonly_func() #7 [ "unknown"() ]
+; CHECK: Both ModRef:   call void @an_argmemonly_func(i8* %q) #9 [ "unknown"() ] <->   call void @an_inaccessibleorargmemonly_func(i8* %q) #8 [ "unknown"() ]
+}