diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -100,6 +100,35 @@
   BaseTy getAssumed() const { return Assumed; }
 
 protected:
+  /// Copy the bits set in \p BitsEncoding from \p From to \p To.
+  static void copyBits(BaseTy &To, const BaseTy From, BaseTy BitsEncoding) {
+    BaseTy UnaffectedBits = To & (~BitsEncoding);
+    BaseTy AffectedBits = From & BitsEncoding;
+    To = UnaffectedBits | AffectedBits;
+  }
+
+  /// Set the bits of \p Target also set in \p BitsEncoding.
+  static void setBits(BaseTy &Target, BaseTy BitsEncoding) {
+    Target = Target | BitsEncoding;
+  }
+
+  /// Unset the bits of \p Target also set in \p BitsEncoding.
+  static BaseTy &unsetBits(BaseTy &Target, BaseTy BitsEncoding) {
+    Target = Target & ~BitsEncoding;
+    return Target;
+  }
+
+  /// Intersect the bits of \p Target also set in \p BitsEncoding.
+  static BaseTy &intersectBits(BaseTy &Target, BaseTy BitsEncoding) {
+    Target = Target & BitsEncoding;
+    return Target;
+  }
+
+  /// Return true if the bits set in \p BitsEncoding are set in \p Source.
+  static bool testBits(BaseTy Source, BaseTy BitsEncoding) {
+    return (Source & BitsEncoding) == BitsEncoding;
+  }
+
   /// The known state encoding in an integer of type BaseTy.
   BaseTy Known;
 
@@ -691,17 +720,17 @@
 
   /// See AANoCapture::isAssumedNoCapture(...).
   bool isAssumedNoCapture() const override {
-    return getAssumed() == BEST_STATE;
+    return testBits(getAssumed(), NOT_CAPTURED | NOT_RETURNED);
   }
 
   /// See AANoCapture::isKnownNoCaptureMaybeReturned(...).
   bool isKnownNoCaptureMaybeReturned() const override {
-    return getKnown() & NOT_CAPTURED;
+    return testBits(getKnown(), NOT_CAPTURED);
   }
 
   /// See AANoCapture::isAssumedNoCaptureMaybeReturned(...).
   bool isAssumedNoCaptureMaybeReturned() const override {
-    return getAssumed() & NOT_CAPTURED;
+    return testBits(getAssumed(), NOT_CAPTURED);
   }
 
   /// see AbstractAttribute::isAssumedNoCaptureMaybeReturned(...).
@@ -926,7 +955,7 @@
   if (!AssumedNoCapture)
     indicateFixpoint(/* Optimistic */ false);
   else if (MaybeReturned)
-    Assumed = Known | (Assumed & ~NOT_RETURNED);
+    setBits(unsetBits(Assumed, NOT_RETURNED), Known);
 
   return (AssumedState == getAssumed()) ? ChangeStatus::UNCHANGED
                                         : ChangeStatus::CHANGED;