diff --git a/llvm/lib/IR/AttributeImpl.h b/llvm/lib/IR/AttributeImpl.h
--- a/llvm/lib/IR/AttributeImpl.h
+++ b/llvm/lib/IR/AttributeImpl.h
@@ -244,10 +244,10 @@
   friend TrailingObjects;
 
 private:
-  /// Bitset with a bit for each available attribute Attribute::AttrKind.
-  uint64_t AvailableFunctionAttrs;
   LLVMContext &Context;
   unsigned NumAttrSets; ///< Number of entries in this set.
+  /// Bitset with a bit for each available attribute Attribute::AttrKind.
+  uint8_t AvailableFunctionAttrs[12];
 
   // Helper fn for TrailingObjects class.
   size_t numTrailingObjects(OverloadToken<AttributeSet>) { return NumAttrSets; }
@@ -267,7 +267,7 @@
   /// Return true if the AttributeSet or the FunctionIndex has an
   /// enum attribute of the given kind.
   bool hasFnAttribute(Attribute::AttrKind Kind) const {
-    return AvailableFunctionAttrs & ((uint64_t)1) << Kind;
+    return AvailableFunctionAttrs[Kind / 8] & ((uint64_t)1) << (Kind % 8);
   }
 
   using iterator = const AttributeSet *;
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -896,7 +896,7 @@
 
 AttributeListImpl::AttributeListImpl(LLVMContext &C,
                                      ArrayRef<AttributeSet> Sets)
-    : AvailableFunctionAttrs(0), Context(C), NumAttrSets(Sets.size()) {
+    : Context(C), NumAttrSets(Sets.size()), AvailableFunctionAttrs{} {
   assert(!Sets.empty() && "pointless AttributeListImpl");
 
   // There's memory after the node where we can store the entries in.
@@ -909,8 +909,10 @@
   static_assert(attrIdxToArrayIdx(AttributeList::FunctionIndex) == 0U,
                 "function should be stored in slot 0");
   for (const auto I : Sets[0]) {
-    if (!I.isStringAttribute())
-      AvailableFunctionAttrs |= 1ULL << I.getKindAsEnum();
+    if (!I.isStringAttribute()) {
+      Attribute::AttrKind Kind = I.getKindAsEnum();
+      AvailableFunctionAttrs[Kind / 8] |= 1ULL << (Kind % 8);
+    }
   }
 }